Abstract: OBJECTIVE: Glomerular mesangial expansion and podocyte loss are important early features of diabetic nephropathy, whereas tubulointerstitial injury and fibrosis are critical for progression of diabetic nephropathy to kidney failure. Therefore, we analyzed the expression of genes in glomeruli and tubulointerstitium in kidney biopsies from diabetic nephropathy patients to identify pathways that may be activated in humans but not in murine models of diabetic nephropathy that fail to progress to glomerulosclerosis, tubulointerstitial fibrosis, and kidney failure. RESEARCH DESIGN AND METHODS: Kidney biopsies were obtained from 74 patients (control subjects, early and progressive type 2 diabetic nephropathy). Glomerular and tubulointerstitial mRNAs were microarrayed, followed by bioinformatics analyses. Gene expression changes were confirmed by real-time RT-PCR and immunohistological staining. Samples from db/db C57BLKS and streptozotocin-induced DBA/2J mice, commonly studied murine models of diabetic nephropathy, were analyzed. RESULTS: In human glomeruli and tubulointerstitial samples, the Janus kinase (Jak)-signal transducer and activator of transcription (Stat) pathway was highly and significantly regulated. Jak-1, -2, and -3 as well as Stat-1 and -3 were expressed at higher levels in patients with diabetic nephropathy than in control subjects. The estimated glomerular filtration rate significantly correlated with tubulointerstitial Jak-1, -2, and -3 and Stat-1 expression (R(2) = 0.30-0.44). Immunohistochemistry found strong Jak-2 staining in glomerular and tubulointerstitial compartments in diabetic nephropathy compared with control subjects. In contrast, there was little or no increase in expression of Jak/Stat genes in the db/db C57BLKS or diabetic DBA/2J mice. CONCLUSIONS: These data suggest a direct relationship between tubulointerstitial Jak/Stat expression and progression of kidney failure in patients with type 2 diabetic nephropathy and distinguish progressive human diabetic nephropathy from nonprogressive murine diabetic nephropathy.

Abstract: To elucidate the mechanisms of glomerulonephritis, including Goodpasture's syndrome, mouse models are used that use heterologous Abs against the glomerular basement membrane (GBM) with or without preimmunization with foreign IgG from the same species. These studies have revealed the requirement of either FcgammaR or complement, depending on the experimental model used. In this study, we provide evidence that both FcgammaR and complement are obligatory for a full-blown inflammation in a novel attenuated passive model of anti-GBM disease. We demonstrate that administration of subnephritogenic doses of rabbit anti-GBM Abs followed by a fixed dose of mouse mAbs to rabbit IgG, allowing timing and dosing for the induction of glomerulonephritis, resulted in reproducible complement activation via the classical pathway of complement and albuminuria in wild-type mice. Because albuminuria was absent in FcR-gamma-chain(-/-) mice and reduced in C3(-/-) mice, a role for both FcgammaR and complement is postulated. Because C1q(-/-) and C4(-/-) mice lacking a functional classical and lectin pathway did develop albuminuria, we suggest involvement of the alternative pathway of complement. Anti-GBM glomerulonephritis occurs acutely following the administration of mouse anti-rabbit IgG, and proceeds in a chronic fashion dependent on both FcgammaR and complement. This novel attenuated model allows elucidating the relative contribution of different mediator systems of the immune system to the development of renal injury, and also provides a platform for the assessment of different treatment protocols and evaluation of drugs that ultimately may be beneficial for the treatment of anti-GBM mediated glomerulonephritides.

Abstract: Diabetic nephropathy is the most common cause of endstage renal disease. Approaches targeting angiotensin II significantly delay its progression. However, many patients still need renal replacement therapy. High throughput techniques such as unbiased gene expression profiling and proteomics may identify new therapeutic targets. Cell death is thought to contribute to progressive renal cell depletion in chronic nephropathies. A European collaborative effort recently applied renal biopsy transcriptomics to identify novel mediators of renal cell death in diabetic nephropathy. Twenty-five percent of cell death regulatory genes were upor downregulated in diabetic kidneys. TNF-related apoptosisinducing ligand (TRAIL) and osteoprotegerin had the highest level of expression. In diabetic nephropathy, tubular cells and podocytes express TRAIL. Inflammatory cytokines, including MIF via CD74, upregulate TRAIL. A high glucose environment sensitized renal cells to the lethal effect of TRAIL, while osteoprotegerin is protective. These results suggest that, in addition to glucose levels, inflammation and TRAIL are therapeutic targets in diabetic nephropathy.

Abstract: Although metabolic derangement plays a central role in diabetic nephropathy, a better understanding of secondary mediators of injury may lead to new therapeutic strategies. Expression of macrophage migration inhibitory factor (MIF) is increased in experimental diabetic nephropathy, and increased tubulointerstitial mRNA expression of its receptor, CD74, has been observed in human diabetic nephropathy. Whether CD74 transduces MIF signals in podocytes, however, is unknown. Here, we found glomerular and tubulointerstitial CD74 mRNA expression to be increased in Pima Indians with type 2 diabetes and diabetic nephropathy. Immunohistochemistry confirmed the increased glomerular and tubular expression of CD74 in clinical and experimental diabetic nephropathy and localized glomerular CD74 to podocytes. In cultured human podocytes, CD74 was expressed at the cell surface, was upregulated by high concentrations of glucose and TNF-alpha, and was activated by MIF, leading to phosphorylation of extracellular signal-regulated kinase 1/2 and p38. High glucose also induced CD74 expression in a human proximal tubule cell line (HK2). In addition, MIF induced the expression of the inflammatory mediators TRAIL and monocyte chemoattractant protein 1 in podocytes and HK2 cells in a p38-dependent manner. These data suggest that CD74 acts as a receptor for MIF in podocytes and may play a role in the pathogenesis of diabetic nephropathy.

Abstract: Basic fibroblast growth factor (FGF-2) plays a role in renal fibrogenesis, although its potential implications for tubulointerstitial involvement in diabetic nephropathy are unknown. We evaluated the expression of FGF-2 in kidney biopsies from patients with diabetic nephropathy and studied the mechanisms of its induction in human renal fibroblasts under hyperglycemia. Tubulointerstitial expression of FGF-2 was significantly upregulated in diabetic nephropathy compared with control kidneys with a good correlation to the degree of the injury. Fibroblasts cultivated in high glucose displayed increased FGF-2 mRNA as well as protein synthesis and secretion compared with normal glucose. Proliferation rates under hyperglycemia were significantly higher and could be almost completely inhibited by addition of a neutralizing FGF-2 antibody. Alterations in proliferation were associated with changes in p27(kip1) expression. Hyperglycemia induced the expression of PKC-beta1 and PKC-beta2; however, only inhibition of PKC-beta1 but not PKC-beta2 led to a significant decrease of FGF-2 levels. Relevance of the culture findings and functional association was corroborated by colocalization of FGF-2 and PKC-beta in human diabetic kidneys in vivo. High glucose stimulated fibronectin synthesis and secretion, which could be substantially prevented by inhibition of PKC-beta1 and to a lesser extent by inhibiting the FGF-2. Expression of active phosphorylated form of p38 mitogen-activated protein kinase was upregulated under hyperglycemia; however, its inhibition had no effects on FGF-2 synthesis. Our results implicate a role of FGF-2 in high glucose-altered molecular signaling in pathogenesis of diabetic renal disease.

Abstract: BACKGROUND: Proteinuria is a major marker of the decline of renal function and an important risk factor of coronary heart disease. Elevated proteinuria is associated to the disruption of slit-diaphragm and loss of podocyte foot processes, structural alterations that are considered irreversible. The objective of the present study was to investigate whether proteinuria can be reversed and to identify the structural modifications and the gene/protein regulation associated to this reversal. METHODOLOGY/PRINCIPAL FINDINGS: We used a novel transgenic strain of mouse (RenTg) that overexpresses renin at a constant high level. At the age of 12-month, RenTg mice showed established lesions typical of chronic renal disease such as peri-vascular and periglomerular inflammation, glomerular ischemia, glomerulosclerosis, mesangial expansion and tubular dilation. Ultrastructural analysis indicated abnormal heterogeneity of basement membrane thickness and disappearance of podocyte foot processes. These structural alterations were accompanied by decreased expressions of proteins specific of podocyte (nephrin, podocin), or tubular epithelial cell (E-cadherin and megalin) integrity. In addition, since TGFbeta is considered the major pro-fibrotic agent in renal disease and since exogenous administration of BMP7 is reported to antagonize the TGFbeta-induced phenotype changes in kidney, we have screened the expressions of several genes belonging in the TGFbeta/BMP superfamily. We found that the endogenous inhibitors of BMPs such as noggin and Usag-1 were several-fold activated inhibiting the action of BMPs and thus reinforcing the deleterious action of TGFbeta.Treatment with an AT1 receptor antagonist, at dose that did not decrease arterial pressure, gradually reduced albuminuria. This decrease was accompanied by re-expression of podocin, nephrin, E-cadherin and megalin, and reappearance of podocyte foot processes. In addition, expressions of noggin and Usag-1 were markedly decreased, permitting thus activation of the beneficial action of BMPs. CONCLUSIONS/SIGNIFICANCE: These findings show that proteinuria and alterations in the expression of proteins involved in the integrity and function of glomerular and renal epithelial phenotype are reversible events when the local action of angiotensin II is blocked, and provide hope that chronic renal disease can be efficiently treated.

Abstract: Podocytes possess the complete machinery for glutamatergic signaling, raising the possibility that neuron-like signaling contributes to glomerular function. To test this, we studied mice and cells lacking Rab3A, a small GTPase that regulates glutamate exocytosis. In addition, we blocked the glutamate ionotropic N-methyl-d-aspartate receptor (NMDAR) with specific antagonists. In mice, the absence of Rab3A and blockade of NMDAR both associated with an increased urinary albumin/creatinine ratio. In humans, NMDAR blockade, obtained by addition of ketamine to general anesthesia, also had an albuminuric effect. In vitro, Rab3A-null podocytes displayed a dysregulated release of glutamate with higher rates of spontaneous exocytosis, explained by a reduction in Rab3A effectors resulting in freedom of vesicles from the actin cytoskeleton. In addition, NMDAR antagonism led to profound cytoskeletal remodeling and redistribution of nephrin in cultured podocytes; the addition of the agonist NMDA reversed these changes. In summary, these results suggest that glutamatergic signaling driven by podocytes contributes to the integrity of the glomerular filtration barrier and that derangements in this signaling may lead to proteinuric renal diseases.

Abstract: IgA nephropathy (IgAN) is characterized by glomerular deposition of IgA, often together with complement components. This deposited IgA is mainly polymeric in nature. Although early studies suggested a role for local complement activation in the development of glomerular injury in IgAN, recent attention has focused on the involvement of the lectin pathway of complement activation in the progression of renal disease in IgAN. In addition, we have found that glomerular secretory IgA deposition may be one of the initiators of local complement activation in the kidney. In the present review we discuss recent developments in this area and provide a model of how mucosal immunity and renal inflammation may be interconnected.

Abstract: Podocyte dysfunction, represented by foot process effacement and proteinuria, is often the starting point for progressive kidney disease. Therapies aimed at the cellular level of the disease are currently not available. Here we show that induction of urokinase receptor (uPAR) signaling in podocytes leads to foot process effacement and urinary protein loss via a mechanism that includes lipid-dependent activation of alphavbeta3 integrin. Mice lacking uPAR (Plaur-/-) are protected from lipopolysaccharide (LPS)-mediated proteinuria but develop disease after expression of a constitutively active beta3 integrin. Gene transfer studies reveal a prerequisite for uPAR expression in podocytes, but not in endothelial cells, for the development of LPS-mediated proteinuria. Mechanistically, uPAR is required to activate alphavbeta3 integrin in podocytes, promoting cell motility and activation of the small GTPases Cdc42 and Rac1. Blockade of alphavbeta3 integrin reduces podocyte motility in vitro and lowers proteinuria in mice. Our findings show a physiological role for uPAR signaling in the regulation of kidney permeability.

Abstract: Apoptotic cell death contributes to diabetic nephropathy (DN), but its role is not well understood. The tubulointerstitium from DN biopsy specimens was microdissected, and expression profiles of genes related to apoptosis were analyzed. A total of 112 (25%) of 455 cell death-related genes were found to be significantly differentially regulated. Among those that showed the greatest changes in regulation were two death receptors, OPG (the gene encoding osteoprotegerin) and Fas, and the death ligand TRAIL. Glomerular and proximal tubular TRAIL expression, assessed by immunohistochemistry, was higher in DN kidneys than controls and was associated with clinical and histologic severity of disease. In vitro, proinflammatory cytokines but not glucose alone regulated TRAIL expression in the human proximal tubular cell line HK-2. TRAIL induced tubular cell apoptosis in a dosage-dependant manner, an effect that was more marked in the presence of high levels of glucose and proinflammatory cytokines. TRAIL also activated NF-kappaB, and inhibition of NF-kappaB sensitized cells to TRAIL-induced apoptosis. It is proposed that TRAIL-induced cell death could play an important role in the progression of human DN.

Abstract: The endoplasmic reticulum (ER) is an important site for protein folding and becomes "stressed" when its capacity to fold proteins is overwhelmed. In response, "unfolded protein response" (UPR) genes are induced, increasing the capacity to fold proteins; if the response is insufficient, then apoptosis ensues. For investigation of whether proteinuria and hyperglycemia induce ER stress in renal epithelial cells, microarray data from biopsies of established diabetic nephropathy (DN) were analyzed. Expression of UPR genes was significantly different in these biopsies than in control kidneys or biopsies of patients with mild DN, suggesting an association between the degree of DN and UPR gene expression. Expression of the transcription factor XBP1 and the ER chaperones HSPA5 and HYOU1 were increased, but the proapoptotic gene DDIT3 was unchanged. These findings were replicated in an independent cohort of patients with established DN by real-time reverse transcriptase-PCR. Immunofluorescence of renal biopsies from patients with DN confirmed the upregulation for HSPA5 and HYOU1 proteins in tubular epithelia. In biopsies of minimal-change disease, the mRNA levels of some ER stress molecules were also induced, but protein expression of HSPA5 and HYOU1 remained significantly lower than that observed in DN. Exposure of renal tubular epithelial cells to albumin and high glucose in vitro enhanced expression of genes involved in ER stress. These observations suggest that in proteinuric diseases, tubular epithelial cells undergo ER stress, which induces an adaptive, protective UPR. Although this may protect the cells from ER stress, persistence of hyperglycemia and proteinuria may eventually lead to apoptosis.

Abstract: Mechanism of renal fibrosis leading to end stage kidney remains still a challenge of interest in humans. The pathogenesis of chronic kidney disease is characterized by progressive loss of kidney function and fibrosis. The mechanism of epithelial-mesenchymal transition (EMT) has been predominantly studied in in vitro studies, and we previously demonstrated the EMT of tubular epithelial cells in dogs. In this study, we examined and quantified the modifications of cadherin-catenin complex by immunohistochemistry of E-cadherin and beta-catenin and the mesenchymal marker vimentin in 25 dogs with three different spontaneous inflammatory renal diseases. Results showed a significant down-expression of levels of E-cadherin and beta-catenin directly correlated with the tubular-interstitial damage (TID). In TID grades 2 and 3, E-cadherin expression was significantly reduced (p < 0.001). beta-catenin expression was overall similar to E-cadherin. The mesenchymal-associated protein, vimentin, was de novo identified in tubules within areas of inflammation. In this work, we identified the loss of cadherin or catenin expression as a progressive mechanism in tubulo-interstitial fibrosis, which allows dissociation of structural integrity of renal epithelia and loss of epithelial polarity. The dog might result more significant as model for new therapies.

Abstract: Diabetic nephropathy (DN) is a frequent complication in patients with diabetes. Although the majority of DN models and human studies have focused on glomeruli, tubulointerstitial damage is a major feature of DN and an important predictor of renal dysfunction. This study sought to investigate molecular markers of pathogenic pathways in the renal interstitium of patients with DN. Microdissected tubulointerstitial compartments from biopsies with established DN and control kidneys were subjected to expression profiling. Analysis of candidate genes, potentially involved in DN on the basis of common hypotheses, identified 49 genes with significantly altered expression levels in established DN in comparison with controls. In contrast to some rodent models, the growth factors vascular endothelial growth factor A (VEGF-A) and epidermal growth factor (EGF) showed a decrease in mRNA expression in DN. This was validated on an independent cohort of patients with DN by real-time reverse transcriptase-PCR. Immunohistochemical staining for VEGF-A and EGF also showed a reduced expression in DN. The decrease of renal VEGF-A expression was associated with a reduction in peritubular capillary densities shown by platelet-endothelial cell adhesion molecule-1/CD31 staining. Furthermore, a significant inverse correlation between VEGF-A and proteinuria, as well as EGF and proteinuria, and a positive correlation between VEGF-A and hypoxia-inducible factor-1alpha mRNA was found. Thus, in human DN, a decrease of VEGF-A, rather than the reported increase as described in some rodent models, may contribute to the progressive disease. These findings and the questions about rodent models in DN raise a note of caution regarding the proposal to inhibit VEGF-A to prevent progression of DN.

Abstract:

Abstract: Injury to podocytes and their slit diaphragms typically leads to marked proteinuria. Mutations in the TRPC6 gene that codes for a slit diaphragm-associated, cation-permeable ion channel have been shown recently to co-segregate with hereditary forms of progressive kidney failure. Herein is shown that induced expression of wild-type TRPC6 is a common feature of human proteinuric kidney diseases, with highest induction observed in membranous nephropathy. Cultured podocytes that are exposed to complement upregulate TRPC6 protein. Stimulation of receptor-operated channels in puromycin aminonucleoside-treated podocytes leads to increased calcium influx in a time- and dosage-dependent manner. Mechanistically, it is shown that TRPC6 is functionally connected to the podocyte actin cytoskeleton, which is rearranged upon overexpression of TRPC6. Transient in vivo gene delivery of TRPC6 into mice leads to expression of TRPC6 protein at the slit diaphragm and causes proteinuria. These studies suggest the involvement of TRPC6 in the pathology of nongenetic forms of proteinuric disease.

Abstract: BACKGROUND: Recently we reported a possible role for secretory IgA (SIgA) in IgA nephropathy (IgAN), as suggested by increased serum levels in patients with active disease and accumulation of SIgA in a glomerular eluate. Therefore, we attempted to find support for these findings by analysis of the presence of SIgA in biopsies of IgAN patients. METHODS: Renal biopsies of 26 patients with biopsy-proven IgAN were analysed for the presence of SIgA and complement proteins. RESULTS: In 15% mesangial deposition of SIgA was demonstrated, using a specific staining for secretory component (SC) and colocalization with IgA. The presence of SIgA in these biopsies showed a strong correlation with deposition of mannose-binding lectin (MBL) and C4d. Moreover, we observed a strong colocalization between SIgA and MBL or C4d. This local complement activation has previously been linked to more severe renal disease. CONCLUSIONS: Therefore, these data provide additional evidence for a pathogenic role for SIgA in IgA nephropathy.

Abstract: BACKGROUND: Filtrin (NEPH3/KIRREL2) is a recently characterized member of the nephrin-like proteins of the immunoglobulin superfamily, and it has been suggested to participate in the maintenance of the glomerular filtration barrier in the kidney. In this study, the gene and protein expression of filtrin were examined in patients with acquired proteinuric diseases. METHODS: Filtrin mRNA levels in renal biopsies were measured with quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) in two sets of patients with proteinuria. The mRNA levels were normalized to the housekeeping gene GAPDH and also related to the podocyte-specific genes nephrin and podocin. Immunofluorescence microscopy was employed to explore changes in the glomerular distribution of filtrin. RESULTS: Reduced glomerular expression of filtrin mRNA was observed in all studied diagnostic groups. In focal segmental glomerulosclerosis, the filtrin mRNA level was only one-tenth of the control samples (P approximately 5.0x10(-6)), and this finding was confirmed in a second set of samples. The ratios of filtrin to nephrin and podocin demonstrated a marked decrease in the expression of filtrin relative to the podocyte marker genes. However, no correlation between the expression of filtrin and the levels of serum creatinine and proteinuria was observed. Immunostaining showed changes in the expression pattern of filtrin in renal biopsies. Immunoelectron microscopic studies localized filtrin at the slit diaphragm of the podocyte foot processes. CONCLUSIONS: Down-regulation of the filtrin gene and protein expression in the renal biopsies together with the localization to the inter-podocyte filtration slit imply a potential role for this molecule in the pathogenesis of proteinuric diseases.

Abstract: Tubulo-interstitial fibrosis in dogs may result from primary injury to the interstitium or develop secondary to other renal diseases. As in human renal pathology, tubular epithelial cells (TEC) are believed to actively participate in the mechanisms of renal fibrosis. In this study, we examined the changes in the tubular epithelial component in two specific canine diseases. Immunohistochemistry showed the expression of the epithelial marker cytokeratin, the smooth muscle marker alpha-SMA, the mesenchymal marker vimentin and PCNA in 20 dogs with membranous glomerulonephritis and membrano-proliferative glomerulonephritis. Results showed that the loss of the epithelial marker in TEC was directly correlated to the grade of tubulo-interstitial disease present and independent of the type of glomerulonephritis. Varying degrees of vimentin positivity were detected in tubular epithelium in areas of inflammation, and low numbers of scattered alpha-SMA-positive cells were also observed. Immunohistochemistry showed that epithelial tubular cells lose their cytokeratin staining characteristics and transdifferentiate into cells exhibiting key mesenchymal immunophenotypic feature of vimentin-positive staining in both diseases investigated. The integrity of the tubular basement membrane is likely to be fundamental in maintaining the epithelial phenotype of TEC. Animal models provide opportunities for investigating the pathogenesis of renal fibrosis in humans.

Abstract: The occurrence and extent of apoptosis in the kidneys of patients with diabetic nephropathy is largely unknown. We evaluated apoptosis in renal biopsies obtained from patients with early or advanced type II diabetic nephropathy. Apoptosis was about 6- and 3-fold higher, respectively, in glomeruli and tubules in kidneys of patients with early nephropathy than in the normal kidney and this was not further increased in advanced diabetic nephropathy. Glomerular apoptosis was related directly to hemoglobin A1(c) and systolic blood pressure, whereas tubular cell apoptosis correlated to diabetes duration and low-density lipoprotein-cholesterol. Fas, Fas ligand, and p38 mitogen-activated protein kinase expressions were enhanced in glomeruli and tubules; however, this did not correlate with apoptosis. In patients with proteinuria, apoptosis was associated with the subsequent loss of kidney function. When these parameters were subjected to multivariate analysis, only glomerular apoptosis retained a significant independent predictive value. Our findings suggest that apoptosis might be a clinically relevant mechanism of glomerular and tubular cell loss in proteinuric type II diabetic patients.

Abstract: Rats of the Milan hypertensive strain (MHS) are resistant to both hypertensive and diabetic renal disease. Genetically determined hypertrophy of intrarenal arteries has been suggested as the putative mechanism preventing transmission of systemic hypertension to the glomerular microcirculation or diabetes-induced loss of autoregulation, which lead to glomerular hypertension and consequent podocyte injury and proteinuria. This study aimed to investigate glomerular barrier function and structure in ageing and diabetic MHS rats under basal conditions and after injection of 2.5 g of bovine serum albumin (BSA) causing increased workload and possibly removing haemodynamic protection by inducing renal cortical vasodilatation. Genetically related rats of the Milan normotensive strain (MNS) served as a proteinuric counterpart. No change in renal function or structure was detected in diabetic MHS rats, whereas MNS rats developed diabetic nephropathy superimposed on that occurring spontaneously in this strain. Diabetic, but not non-diabetic, MHS rats showed significantly reduced synaptopodin and nephrin expression, though to a lesser extent than non-diabetic and diabetic MNS rats, together with unchanged podocyte number, density and structure and no proteinuria. Agrin expression was significantly altered in diabetic versus non-diabetic MHS animals, whereas collagen I was expressed only in diabetic MHS rats and collagen IV content did not change significantly between the two groups. Upon BSA injection, proteinuria increased markedly and abundant BSA was detected only in kidneys from diabetic MHS rats. BSA injection was associated with changes in intrarenal arteries suggesting vasodilatation, without any influx of inflammatory cells. These data indicate that while MNS rats show marked changes in the glomerular filtration barrier with either age or diabetes, glomerulosclerosis-resistant MHS rats develop only minor diabetes-induced podocyte (and extracellular matrix) alterations, which are not associated with proteinuria unless they are unmasked by an increased workload or removal of the haemodynamic protection.

Abstract: Histological and immunohistological examination of renal biopsy material is the method of choice for the diagnosis of glomerular and interstitial renal disease. However, our understanding of renal damage is still largely incomplete because of the limited knowledge of the etiology and pathogenesis of numerous kidney diseases. For this reason, we still provide unspecific treatment to kidney patients, which is generally aimed at counteracting inflammatory alterations and slowing progression towards renal failure, without intervening directly in the cause of the disease. The recent development of the ''omics'' (genomics, proteomics, metabolomics) following the enormous progress of high-throughput technologies and information technology tools is profoundly transforming our knowledge in every biomedical field, including nephrology. It is expected that in a very short time a better understanding of both physiological and pathological events in the kidney will translate into different therapeutic strategies, possibly targeted to individual needs. Nephrologists and renal pathologists must take these changes into account and realize that a new approach to renal biopsy is urgently required. Renal biopsy material has in fact an enormous importance in the generation of new knowledge and in the validation of experimental results from high-throughput technologies and animal models. Furthermore, it is conceivable that a new classification of renal diseases will be needed soon as a result of the improved knowledge. For these reasons, renal biopsy material should be adequately processed and preserved according to modern methods, and collaborative projects should be fostered to achieve standardized methods and avoid a waste of energy in singular efforts.

Abstract: IgA nephropathy (IgAN) is characterized by glomerular co-deposition of IgA and complement components. Earlier studies showed that IgA activates the alternative pathway of complement, whereas more recent data also indicate activation of the lectin pathway. The lectin pathway can be activated by binding of mannose-binding lectin (MBL) and ficolins to carbohydrate ligands, followed by activation of MBL-associated serine proteases and C4. This study examined the potential role of the lectin pathway in IgAN. Renal biopsies of patients with IgAN (n=60) showed mesangial deposition of IgA1 but not IgA2. Glomerular deposition of MBL was observed in 15 (25%) of 60 cases with IgAN and showed a mesangial pattern. All MBL-positive case, but none of the MBL-negative cases showed glomerular co-deposition of L-ficolin, MBL-associated serine proteases, and C4d. Glomerular deposition of MBL and L-ficolin was associated with more pronounced histologic damage, as evidenced by increased mesangial proliferation, extracapillary proliferation, glomerular sclerosis, and interstitial infiltration, as well as with significantly more proteinuria. Patients who had IgAN with or without glomerular MBL deposition did not show significant differences in serum levels of MBL, L-ficolin, or IgA or in the size distribution of circulating IgA. Furthermore, in vitro experiments showed clear binding of MBL to polymeric but not monomeric patient IgA, without a significant difference between both groups. Together, these findings strongly point to a role for the lectin pathway of complement in glomerular complement activation in IgAN and suggest a contribution for both MBL and L-ficolin in the progression of the disease.

Abstract: Alterations in glomerular podocyte cell-cell and cell-matrix contacts are key events in progressive glomerular failure. Integrin-linked kinase (ILK) has been implicated in podocyte cell-matrix interaction and is induced in proteinuria. For evaluation of ILK function in vivo, mice with a Cre-mediated podocyte-specific ILK inactivation were generated. These mice seemed normal at birth but developed progressive focal segmental glomerulosclerosis and died in terminal renal failure. The first ultrastructural lesions that are seen at onset of albuminuria are glomerular basement membrane (GBM) alterations with a significant increase in true harmonic mean GBM thickness. Podocyte foot process effacement and loss of slit diaphragm followed with progression to unselective proteinuria. No significant reduction of slit membrane molecules (podocin and nephrin), key GBM components (fibronectin, laminins, and collagen IV isoforms), or podocyte integrins could be observed at onset of proteinuria. However, alpha3-integrins were relocalized into a granular pattern along the GBM, consistent with altered integrin-mediated matrix assembly in ILK-deficient podocytes. As the increased GBM thickness precedes structural podocyte lesions and key components of the GBM were expressed at comparable levels to controls, these data suggest an essential role of ILK for the close interconnection of GBM structure and podocyte function.

Abstract: BACKGROUND: GLUT1 upregulation and increased glucose transport activity may contribute to extracellullar matrix (ECM) accumulation characterizing diabetic nephropathy (DN). Rats of the Milan hypertensive strain (MHS) are resistant to both hypertensive and diabetic renal disease, due to a haemodynamic protection. On the contrary, those of the Milan normotensive strain (MNS) develop spontaneous glomerulosclerosis, and when rendered diabetic, show typical morphological and haemodynamic changes. METHODS: To assess whether susceptibility to diabetic glomerulopathy in MNS rats is associated with higher glucose transporter 1 (GLUT1) expression (and glucose transport activity) vs MHS rats, diabetic and nondiabetic MNS and MHS rats were followed for 6 months and mesangial cells derived from these animals were exposed to high glucose (HG) vs normal glucose (NG) conditions. RESULTS: Glomerular expression of GLUT1 protein and ECM and transforming growth factor-beta (TGF-beta) mRNA was significantly upregulated in diabetic vs nondiabetic MNS, but not MHS rats. Upon exposure to HG and/or TGF-beta, mesangial cells from 1- and 8-month-old MNS rats showed higher glucose transport activity and GLUT1 membrane expression than those from age-matched MHS rats. Likewise, ECM and TGF-beta production increased more markedly in response to HG and/or TGF-beta in MNS vs MHS mesangial cells. CONCLUSIONS: These data indicate that susceptibility to diabetic glomerulopathy in MNS rats is associated with increased GLUT1-dependent glucose transport activity in response to hyperglycaemia and/or TGF-beta, which may amplify ECM overproduction. Conversely, the haemodynamic protection from glomerulosclerosis in MHS rats is associated with lack of upregulation of TGF-beta/GLUT1 axis, thus supporting the concept that this axis may represent the link between haemodynamic and metabolic mechanisms of injury.

Abstract: Renal involvement in type 2 diabetes is a well known clinical occurrence. According to data from the literature, besides diabetic glomerulosclerosis, type 2 diabetic nephropathy may occur as a non specific chronic damage mostly related to vascular changes, or as a glomerular disease superimposed on or even unrelated to diabetic glomerulosclerosis. The most common picture remains in any case diabetic glomerulosclerosis (diabetic GS), that is characterized by variable degrees of mesangial sclerosis.

Abstract: Although patients with chronic renal failure are increasing worldwide, many aspects of kidney biology remain to be elucidated. Recent research has uncovered several molecular properties of the glomerular filtration barrier, in which podocytes, highly differentiated, ramified cells that enwrap the glomerular basement membrane, have been reported to be mainly responsible for filter's selectivity. We previously described that podocytes express Rab3A, a GTPase restricted to cell types that are capable of highly regulated exocytosis, such as neuronal cells. Here, we first demonstrate by a proteomic study that Rab3A in podocytes coimmmunoprecipitates with molecules once thought to be synapse specific. We then show that podocytes possess structures resembling synaptic vesicles, which contain glutamate, coexpress Rab3A and synaptotagmin 1, and undergo spontaneous and stimulated exocytosis and recycling, with glutamate release. Finally, from the results of a cDNA microarray study, we describe the presence of a series of neuron- and synapse-specific molecules in normal human glomeruli and confirm the glomerular protein expression of both metabotropic and ionotropic glutamate receptors. These data point toward a synaptic-like mechanism of communication among glomerular cells, which perfectly fits with the molecular composition of the glomerular filter and puts in perspective several previous observations, proposing a different working hypothesis for understanding glomerular signaling dynamics.

Abstract: The term amyloidosis refers to the deposition of an amorphous substance defined by the presence of a fibrillar structure by electron microscopy and a characteristic beta-pleated sheet structure by x-ray diffraction. The existence of this group of diseases has been recognized for centuries, but major advances in the elucidation of the nature of the deposits have been achieved in the past few years. It is now recognized that the beta-sheet configuration responsible for the general appearance of amyloid deposits is common to a large array of proteins with a different origin. This tertiary structure is responsible for the characteristic tinctorial and optical properties evident by Congo red staining. The material that accumulates in the extracellular compartment progressively destroys the involved organ. The accumulation of amyloid deposits may complicate the course of a wide variety of diseases. Classifications of amyloid disorders reflect some of the current concepts concerning the protein composition of amyloid fibrils in different diseases.

Abstract: Mechanisms for human membranous glomerulonephritis (MGN) remain elusive. Most up-to-date concepts still rely on the rat model of Passive Heymann Nephritis that derives from an autoimmune response to glomerular megalin, with complement activation and membrane attack complex assembly. Clusterin has been reported as a megalin ligand in immunodeposits, although its role has not been clarified. We studied renal biopsies of 60 MGN patients by immunohistochemistry utilizing antibodies against clusterin, C5b-9, and phosphorylated-protien kinase C (PKC) isoforms (pPKC). In vitro experiments were performed to investigate the role of clusterin during podocyte damage by MGN serum and define clusterin binding to human podocytes, where megalin is known to be absent. Clusterin, C5b-9, and pPKC-alpha/beta showed highly variable glomerular staining, where high clusterin profiles were inversely correlated to C5b-9 and PKC-alpha/beta expression (P=0.029), and co-localized with the low-density lipoprotein receptor (LDL-R). Glomerular clusterin emerged as the single factor influencing proteinuria at multivariate analysis and was associated with a reduction of proteinuria after a follow-up of 1.5 years (-88.1%, P=0.027). Incubation of podocytes with MGN sera determined strong upregulation of pPKC-alpha/beta that was reverted by pre-incubation with clusterin, serum de-complementation, or protein-A treatment. Preliminary in vitro experiments showed podocyte binding of biotinilated clusterin, co-localization with LDL-R and specific binding inhibition with anti-LDL-R antibodies and with specific ligands. These data suggest a central role for glomerular clusterin in MGN as a modulator of inflammation that potentially influences the clinical outcome. Binding of clusterin to the LDL-R might offer an interpretative key for the pathogenesis of MGN in humans.

Abstract: Rapidly progressive glomerulonephritis (RPGN) is a clinical syndrome characterized by loss of renal function within days to weeks and by glomerular crescents on biopsy. The pathogenesis of this disease is unclear, but circulating factors are believed to have a major role. Here, we show that deletion of the Von Hippel-Lindau gene (Vhlh) from intrinsic glomerular cells of mice is sufficient to initiate a necrotizing crescentic glomerulonephritis and the clinical features that accompany RPGN. Loss of Vhlh leads to stabilization of hypoxia-inducible factor alpha subunits (HIFs). Using gene expression profiling, we identified de novo expression of the HIF target gene Cxcr4 (ref. 3) in glomeruli from both mice and humans with RPGN. The course of RPGN is markedly improved in mice treated with a blocking antibody to Cxcr4, whereas overexpression of Cxcr4 alone in podocytes of transgenic mice is sufficient to cause glomerular disease. Collectively, these results indicate an alternative mechanism for the pathogenesis of RPGN and glomerular disease in an animal model and suggest novel molecular pathways for intervention in this disease.

Abstract: Despite a lot of research efforts, the origin of renal fibroblasts is still matter of debate. Epithelial-mesenchymal transition (EMT) of tubular epithelial cells could be at least one of the mechanisms by which renal fibroblasts are generated. Every kind of renal injury is potentially able to induce renal tubular cells to go through the various steps of EMT and generate fibroblasts, as it has been demonstrated by experimental models, in vitro experiments, and renal biopsy studies. It means that, if EMT is a common process of progression of renal failure, further studies and a better understanding of this process can lead us to envisage specific treatments to counteract the progression of renal disease.

Abstract: As reported in the previous chapter (Part I) the term amyloidosis refers to the deposition of an amorphous substance defined by the presence of fibrillary structure by electron microscopy and a characteristic betapleated sheet structure by X-ray diffraction. Renal biopsy is fundamental in diagnostic terms because morphological demonstration is necessary and the tissue most frequently involved by amyloidosis is the kidney. In the previous chapter we presented the different histochemical and immunohistochemical techniques that are necessary to differentiate the two main types of amyloidosis defined as AL and AA. Here we show the variability of deposition of amyloid in glomerular, vascular and interstitial compartments.

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Abstract: Minimal Change disease and focal segmental glomerulosclerosis are both clinically characterized by presence of Nephrotic Syndrome. The term Minimal Change disease describes a pathology appearance on light microscopy in which there are no definitive changes from normal glomeruli, although the degree of change that is considered significant remains the subject of some controversy. The focal segmental glomerulosclerosis is morphologically characterized by a segmental solidification of the glomerular tuft, due to collapse of the capillary wall, affecting only some glomeruli (focal). It remains unresolved whether Minimal Change disease and focal segmental glomerulosclerosis are different diseases or whether they represent a spectrum of presentation of the same disease process.

Abstract: Podocytes, the glomerular epithelial cells of the kidney, share important features with neuronal cells. In addition to phenotypical and functional similarities, a number of gene products have been found to be expressed exclusively or predominantly by both cell types. With the hypothesis of a common transcriptome shared by podocytes and neurons, digital differential display was used to identify novel podocyte-expressed gene products. Comparison of brain and kidney cDNA libraries with those of other organs identified Sam68-like mammalian protein 2 (SLM-2), a member of the STAR family of RNA processing proteins, as expressed by podocytes. SLM-2 expression was found to be restricted in the kidney to podocytes. In proteinuric diseases, SLM-2, a known regulator of neuronal mRNA splice site selection, was found significantly upregulated on mRNA and protein levels. Knockdown of SLM-2 by short interfering RNA in podocytes was performed to evaluate its biologic role. RNA splicing of vascular endothelial growth factor (VEGF), a key regulator of the filtration barrier and expressed as functionally distinct splice isoforms, was evaluated. VEGF(165) expression was found to be reduced by 25% after SLM-2 knockdown. In vivo, the glomerular expression of SLM-2 correlated with the mRNA levels of VEGF(165). This study demonstrates the power of digital differential display to predict cell type-specific gene expression by hypothesis-driven analysis of tissue cDNA libraries. SLM-2-dependent VEGF splicing indicates the importance of mRNA splice site selection for glomerular filtration barrier function.

Abstract: "ANCA-associated vasculitis" are Wegener's Granulomatosis, Micropolyarteritis and its renal-limited variant (previously called idiopathic necrotizing glomerulonephritis). According to the "Chapel Hill Consensus Conference" classification, ANCA-associated vasculitis are characterized by prevalent involvement of small-size vessels, whereas medium and large-size arteries involvement is the marker of Polyarteritis Nodosa. But the vessel size-based classification is not always powerful enough, because also in ANCA-associated vasculitis the involvement of medium and large-size arteries if frequent. The distinctive marker of ANCA-associated renal vasculitis has therefore become the presence of necrotizing extracapillary glomerulonephritis, that is always absent in Polyarteritis Nodosa.

Abstract: BACKGROUND: The delicate foot process architecture of glomerular podocytes critically depends on integrin mediated cell-glomerular basement membrane (GBM) interaction. Integrin signaling via the integrin-linked kinase (ILK) is activated in podocyte damage and associated with considerable podocyte phenotype alterations. ILK has been shown to regulate cell fate via nuclear interaction of beta-catenin with lymphoid enhancer factor (LEF-1) transcription factors. The aim of this study was to elucidate the molecular mechanisms of ILK dependant phenotype regulation in podocytes. METHODS: ILK function was evaluated in conditionally immortalized murine glomerular epithelial cells using overexpression of ILK and a small molecule ILK inhibitor in puromycin/adriamycin-induced podocyte damage in vitro and in vivo. RESULTS: Kinase active, but not mutant ILK induced translocation of beta-catenin to the cell nucleus, de novo expression of LEF-1, and nuclear colocalization of beta-catenin and LEF-1. The role of ILK signaling in podocyte damage was evaluated using puromycin, an agent known to cause selective proteinuria and to increase ILK activity. The small molecular ILK inhibitor MC-5 blocked puromycin-induced nuclear translocation of beta-catenin, podocyte detachment, cell proliferation, and repression of the slit membrane molecules P-cadherin and CD2ap. In vivo activation of the beta-catenin pathway could be shown by nuclear colocalization of beta-catenin with WT-1 in adriamycin nephropathy. CONCLUSION: ILK regulates podocyte cell matrix interaction, proliferation, and slit membrane gene expression in podocyte damage. As this pathway is amendable to pharmacologic intervention, further detailed studies of in vivo ILK function in glomerular disease appear justified.

Abstract: BACKGROUND: Pentraxin 3 (PTX3) is a prototypic long pentraxin with structural similarities in the C-terminal domain to the classical short pentraxins C-reactive protein (CRP) and serum amyloid P component. PTX3 is suggested to play an important role in the innate resistance against pathogens, regulation of inflammatory reactions, and clearance of apoptotic cells. Unlike the classic pentraxins, PTX3 is mainly expressed extrahepatically. The present study was designed to investigate the expression of PTX3 by human proximal renal tubular epithelial cells (PTECs). METHODS: PTECs were cultured in the presence or absence of inflammatory cytokines. PTX3 mRNA expression was measured by reverse transcription-polymerase chain reaction (RT-PCR) in human kidney and PTECs. PTX3 protein levels in PTEC cultures were quantified by enzyme-linked immunosorbent assay (ELISA). RESULTS: PTX3 mRNA was shown to be constitutively expressed in human kidney. Constitutive expression and production of PTX3 was shown in primary mesangial cells, in primary PTECs, and in renal fibroblasts. Further analysis showed that interleukin (IL)-1 and tumor necrosis factor-alpha (TNF-alpha) stimulation strongly enhanced the expression and production of PTX3 in PTECs in a dose- and time-dependent manner. In addition, activation of PTECs with IL-17 and CD40L, respectively, but not with IL-6 or IL-4, resulted in strongly increased production of PTX3, whereas granulocyte macrophage-colony-stimulating factor (GM-CSF) inhibited IL-1-induced PTX3 production. PTX3 produced by PTEC is functionally active in binding C1q. CONCLUSION: These results indicate that PTX3 is expressed and released by PTECs and that in proinflammatory conditions PTX3 production is up-regulated. Local expression of PTX3 may play a role in the innate immune response and inflammatory reactions in the kidney.

Abstract: Monoclonal diseases of B-cell lineage, often referred to as plasma cell dyscrasias, are characterized by abnormal and uncontrolled proliferation of a single clone of B cells at different maturation stages, with a more or less marked differentiation to immunoglobulin (Ig)-secreting plasma cells. Thus B-cell proliferation is usually associated with the production and secretion in blood of a monoclonal Ig or a fragment thereof. An ominous consequence of secretion of monoclonal Ig products is their deposition in tissue. These proteinaceous deposits can take the form of casts (in myeloma cast nephropathy), cristals (in myeloma-associated Fanconi's syndrome), fibrils (in light-chain [LC] amyloidosis), or granular precipitates (in monoclonal Ig deposition disease [LCDD]).

Abstract: In the first part of Histopathological Atlas of Renal Diseases we described the typical morphological features of Anca-associated vasculitis. The histological features in Wegener's granulomatosis, Micropolyarteritis and its renal-limited variant, are characterized by "pauci immune" necrotizing extracapillary glomerulonephritis. The cellular composition of glomerular crescent and the mechanisms underlying crescent formation are still incompletely understood. The recent availability of monoclonal antibodies directed against epithelial cells and leucocytes allowed a more precise identification of the crescent cells. In this chapter we will describe the prevalent presence of monocytes in the crescents, the possible mechanisms of recruitment of these cells and the morphological consequences of this glomerular infiltration for the chronic progression of lesions.

Abstract: Henoch-Schonlein purpura is a clinical syndrome characterized by the association of skin, joint, and gastrointestinal symptoms. Henoch-Schonlein purpura is characterized by wide-spread vasculitis. Although the clinical symptoms of this disease are characteristic, the diagnosis is not always easy to establish because other forms of systemic vasculitis - mainly the microscopic form of periarteritis nodosa - may mimic the disease. In addition, in contrast to systemic lupus erythematosus, there are no biological tests that can identify Henoch-Schonlein purpura with certainty. Immunofluorescence microscopic techniques have made an important contribution to both the diagnosis and the study of the pathogenesis of the disease, particularly since they have demonstrated the presence of IgA deposits in the glomeruli and in the vessel walls. These findings not only confirmed the immunologic nature of the pathologic lesions but also drew attention to the remarkable similarity between Henoch-Schonlein purpura nephritis and IgA nephropathy.

Abstract: The main diagnostic feature of anti-glomerular basement membrane (anti-GBM) antibody disease is represented by the immunofluorescence pattern of intense and diffuse linear IgG deposition along the glomerular basement membrane. By light microscopy several histological patterns can be observed.

Abstract: Membranous glomerulonephritis (MGN), histologically defined by subepithelial immune deposits, is the most common cause of nephrotic syndrome in Caucasian adults. The current hypothesis of the underlying disease mechanism postulates production of antibodies against podocyte-derived antigens. Respective antigens could be demonstrated in different animal models and recently in human neonatal MGN. Further support for this hypothesis was generated by the response of human MGN to therapeutic B cell depletion by rituximab. However, the role of B cells in this disease is not well defined. In this study, the interstitial expression of CD20 mRNA was determined in 31 MGN patients and controls (tumor nephrectomies (n = 4), minimal change disease (MCD, n = 10) and focal segmental glomerulosclerosis (n = 6)). CD20 mRNA expression was significantly higher in MGN patients compared to controls. By immunohistochemistry, a focal or diffuse interstitial B cell infiltration could be detected in MGN patients (n = 63), which was absent or minimal in patients with MCD (n = 11). These data suggest an involvement of B cells in the pathogenesis of MGN, possibly as antigen-presenting cells. Further studies should investigate the potential to predict the response to therapeutic B cell depletion by intrarenal CD20 quantification, a potential diagnostic basis for the selection of a specific therapy currently evolving for renal disease.

Abstract: Kidney podocytes and their slit diaphragms form the final barrier to urinary protein loss. This explains why podocyte injury is typically associated with nephrotic syndrome. The present study uncovered an unanticipated novel role for costimulatory molecule B7-1 in podocytes as an inducible modifier of glomerular permselectivity. B7-1 in podocytes was found in genetic, drug-induced, immune-mediated, and bacterial toxin-induced experimental kidney diseases with nephrotic syndrome. The clinical significance of our results is underscored by the observation that podocyte expression of B7-1 correlated with the severity of human lupus nephritis. In vivo, exposure to low-dose LPS rapidly upregulates B7-1 in podocytes of WT and SCID mice, leading to nephrotic-range proteinuria. Mice lacking B7-1 are protected from LPS-induced nephrotic syndrome, suggesting a link between podocyte B7-1 expression and proteinuria. LPS signaling through toll-like receptor-4 reorganized the podocyte actin cytoskeleton in vitro, and activation of B7-1 in cultured podocytes led to reorganization of vital slit diaphragm proteins. In summary, upregulation of B7-1 in podocytes may contribute to the pathogenesis of proteinuria by disrupting the glomerular filter and provides a novel molecular target to tackle proteinuric kidney diseases. Our findings suggest a novel function for B7-1 in danger signaling by nonimmune cells.

Abstract: The characteristic and diagnostic lesion of idiopathic IgA nephropathy (IgAN, Berger's disease) is glomerular IgA deposition, as a unique or predominant positive immunoglobulin. Despite the relatively uniform feature of the immunohistological pattern, the morphological lesions observed by light microscopy are extremely variable. This variability in glomerular and interstitial alterations has frequently created some difficulties in histological classification.

Abstract: Membranous glomerulonephritis (MGN) is characterized by thickening of the glomerular basement membrane due to the presence of subepithelial immune deposits. From a morphological point of view, idiopathic MGN is indistinguishable from class V lupus nephritis. The glomerular lesion is extremely variable and the basement membrane thickening changes over time. According to the classic descriptions, MGN is in fact divided into four stages.

Abstract: Membranoproliferative glomerulonephritis (MPGN) is histologically characterized by intense glomerular hypercellularity (mainly due to mesangial proliferation) and diffuse thickening of the glomerular basement membrane with the appearance of ""double contours"". Two distinct histological forms have been identified--Type I MPGN and Type II MPGN. Type I MPGN is characterized by the predominant presence of subendothelial deposits, while Type II MPGN presents dense homogenous deposits in the basement membrane. Actually, despite many morphological and clinical similarities, there are enough histological and immunohistological differences to suggest that Type II MPGN is a separate and distinct entity, caused by different pathogenetic and morphogenetic mechanisms. Some researchers have identified a further entity: Type III MPGN, characterized by the concomitant presence of subendothelial and subepithelial deposits, but many authors at present believe that Type III MPGN is a morphological variant of Type I MPGN, given their clinical, immunological, and immunohistological similarities

Abstract: Acute post-streptococcal glomerulonephritis, also known as "proliferative-exudative nephritis" is morphologically characterized by intense endocapillary proliferation and massive accumulation of inflammatory cells.

Abstract: BACKGROUND: Hyperlipemia characterizes nephrotic syndrome (NS) and contributes to the progression of the underlying nephropathy. The data in the literature support an implication of apolipoprotein E (apoE) in both hyperlipemia and focal segmental glomerulosclerosis (FSGS), a malignant condition associated with NS. METHODS: The apoE genotype was determined in 209 nephrotic patients, who were classified according to age and their response to steroids as resistant children (N = 96) and adults (43), and steroid dependent (33) and steroid responder (37) children. A total of 123 presented the histological features of FSGS. In a subgroup of 28 patients, serum and urinary levels of apoE and renal deposits were evaluated by immunofluorescence. RESULTS: The allelic frequencies of the three major haplotypes epsilon2, epsilon3, and epsilon4 were the same in nephrotic patients versus controls, and homozygosity for epsilon3epsilon3 was comparably the most frequent genotype (70 vs. 71%) followed by epsilon3epsilon4, epsilon2epsilon3, epsilon2epsilon4, epsilon4epsilon4. Serum levels of apoE were fivefold higher in NS and in FSGS patients than in controls, with a direct correlation with hypercholesterolemia and proteinuria. ApoE genotypes did not influence serum levels. Urinary levels were 1/10,000 of serum with an increment in nephrotic urines. Finally, immunofluorescence demonstrated the absence of apoE in sclerotic glomeruli, while comparably nephrotic patients with membranous nephropathy had an increased glomerular expression of apoE. CONCLUSIONS: ApoE is dysregulated in NS with a marked increment in serum, which is a part of the complex lipid metabolism. Down-regulation of glomerular apoE instead is a peculiarity of FSGS and may contribute to the pathogenesis of the disease. The normal distribution of apoE genotypes in nephrotic patients with FSGS excludes a pathogenetic role of genetic variants.

Abstract: Several recent studies have focused on similarities between glomerular podocytes and neurons because the two cells share a specialized cytoskeletal organization and several expression-restricted proteins, such as nephrin and synaptopodin. In neurons, the small guanosine triphosphatase Rab3A and its effector rabphilin-3A form a complex required for the correct docking of synaptic vesicles to their target membrane. Because rabphilin-3A binds in neurons to cytoskeletal proteins also important for podocyte homeostasis, and the complex rabphilin-3A-Rab3A has been demonstrated in neurons and neuroendocrine cells, the aim of our work was to investigate their possible expression and regulation in podocytes. Normal kidneys from mouse, rat, and human were studied by immunohistochemistry, Western blotting, and reverse transcriptase-polymerase chain reaction to evaluate the expression of Rab3A and rabphilin-3A. Double-staining immunohistochemistry and immunogold electron microscopy were then used to precisely localize the two proteins at the cellular and subcellular levels. Rab-3A and rabphilin-3A regulations in disease were then analyzed in growth hormone-transgenic mice, a well established model of focal and segmental glomerulosclerosis, and in human biopsies from proteinuric patients. Our results demonstrated that rabphilin-3A and Rab3A are present in normal mouse, rat, and human kidneys, with an exclusively glomerular expression and a comma-like pattern of positivity along the glomerular capillary wall, suggestive for podocyte staining. Co-localization of both molecules with synaptopodin confirmed their presence in podocytes. By immunogold electron microscopy both proteins were found around vesicles contained in podocyte foot processes. Their expression was increased in growth hormone-transgenic mice compared to their wild-type counterpart, and in a subset of biopsies from proteinuric patients. Our data, demonstrating the presence of two synaptic proteins in podocytes, further supports similarities between cytoskeletal and vesicular organization of podocytes and neurons. The altered expression observed in mouse and human proteinuric diseases suggests a possible role for these molecules in glomerulopathies.

Abstract: There are several reports of glomerulonephritis (GN) in diabetics or patients with diabetic glomerulosclerosis. Cases of rapidly progressive GN where crescentic histologic changes are superimposed on diabetic glomerulosclerosis are very unusual. We report the case of a patient with type I diabetes mellitus, who developed rapidly progressive renal insufficiency. Renal biopsy disclosed anti-glomerular basement membrane nephritis superimposed on classical diabetic glomerulosclerosis.

Abstract: BACKGROUND: Many factors contribute to the pathogenesis of glomerular proteinuria, but no exact molecular mechanisms are known to date. The recently reported protein nephrin, encoded by the NPHS1 gene, appears to be crucial for the integrity of the glomerular filtration barrier. METHODS: Immunohistochemistry was used to detect possible changes in glomerular nephrin, and a new proteinuria-associated protein expression was developed in various diagnostic groups of human kidney biopsies. RESULTS: In normal control kidney, antibodies to intracellular and extracellular nephrin domain showed a typical podocyte pattern of reactivity, while the 18C7 antibody to a normally inaccessible proteinuria-associated epitope was negative. Instead, strong glomerular positivity by 18C7 was seen in membranous glomerulonephropathy, membranoproliferative glomerulonephritis, systemic lupus erythematosus and cryoglobulinemic nephritis, while with antibodies to either intracellular or extracellular nephrin domains, a down-regulation in nephrin expression pattern was shown. CONCLUSIONS: Unmasking or de novo expression of distinct glomerular proteins may be an important feature reflecting the pathophysiological events in these diseases with altered glomerular permeability, while only mild changes in the slit diaphragm protein nephrin appear to take place.

Abstract: BACKGROUND: Clusterin is a lipoprotein that has anti-complement effects in membranous nephropathy (MN). In focal segmental glomerulosclerosis (FSGS), it inhibits permeability plasma factor activity and could influence proteinuria. Moreover, with aging, knockout mice for clusterin develop a progressive glomerulopathy with sclerosis. METHODS: Since little is known about clusterin metabolism in humans, we determined clusterin levels and composition in the sera and urine of 23 patients with MN, 25 with FSGS and 23 with steroid-responsive nephrotic syndrome (NS). Renal localization was evaluated by immunofluorescence and morphometry. RESULTS: Serum clusterin was markedly reduced in active MN, in FSGS and in children with NS compared to controls; after stable remission of proteinuria, nearly normal levels were restored. Among various biochemical variables, serum clusterin was inversely correlated with hypercholesterolemia. Urinary clusterin, representing a 0.01 fraction of serum, was higher in the urine from normal subjects and FSGS patients in remission with proteinuric MN, FSGS and idiopathic NS; clusterin was inversely correlated with proteinuria. In all cases, urinary and serum clusterin was composed of the same 80 kD isoforms. Finally, a decrease in focal segmental or global clusterin staining was found in FSGS glomeruli, especially in areas of sclerosis. Instead, in MN an overall increment of staining was observed that ranged from mild/focal to very intense/diffuse. CONCLUSIONS: The overall pool of clusterin is reduced in glomerular diseases causing nephrotic syndrome, with hypercholesterolemia appearing as the unifying feature. Depletion of clusterin should negatively affect the clinical outcome in nephrotic patients and efforts should be aimed at normalizing clusterin overall pool.

Abstract: BACKGROUND: In recent studies performed on cultured cells and experimental nephropathies, it has been hypothesized that tubular epithelial cells (TEC), via epithelial-mesenchymal transformation (EMT), can become collagen-producing cells. According to this theory, they should proceed through several activating steps, such as proliferation and phenotype changes, to eventually synthesize extracellular matrix (ECM). METHODS: To evaluate whether EMT operates in human TECs, 133 renal biopsies of different renal diseases were studied, analyzing by immunohistochemistry and in situ hybridization the possible expression of markers of proliferation (PCNA, Mib-1), cellular phenotype (vimentin, alpha-SMA, cytokeratin, ZO-1) and ECM production (prolyl 4-hydroxylase, HSP47, interstitial collagens). RESULTS: Independently of histological diagnosis, variable degrees of TEC positivity for PCNA (2.7 +/- 2.4 cells/field) and Mib-1 (1.9 +/- 2.3) were present. TECs expressing vimentin (1.4 +/- 4.7) and alpha-smooth muscle actin (alpha-SMA; 0.04 +/- 0.4) also were detected. It was possible to observe loss of epithelial antigens from 8 to 10% of the tubular cross sections. Moreover, TECs were stained by prolyl 4-hydroxylase (3.6 +/- 4.3), heat shock protein-47 (HSP47; 2.9 +/- 5.4), collagen type I (0.2 +/- 2.7) and type III (0.3 +/- 2.0). Collagen types I and III mRNAs were found in 0.8 to 1.4 cells/field. The number of TEC with EMT features were associated with serum creatinine and the degree of interstitial damage (P< or = 0.03), and even considering the 45 cases with mild interstitial lesions, the tubular expression of all markers remained strictly associated with renal function (P< or = 0.01). CONCLUSIONS: Our results suggest that, via transition to a mesenchymal phenotype, TEC can produce ECM proteins in human disease and directly intervene in the fibrotic processes. Moreover, the association of EMT features with serum creatinine supports the value of these markers in the assessment of disease severity.

Abstract: BACKGROUND: Segmental glomerular necrosis has been described in the biopsy material in a minority of patients with idiopathic IgA nephropathy in the oldest studies on this disease, but this marker of active capillaritis has received little attention in the subsequent literature, and its significance and relevance for the clinical outcome is still unknown. METHODS: Thirty-five out of 340 patients (10.3%) biopsied in our division at the San Carlo Hospital since 1974 showed active segmental necrotizing lesions. The morphological features and the natural history of this group of patients were compared with those of a control group of 229 patients who had comparable serum creatinine and extent of glomerular sclerosis, but who lacked active segmental necrosis. RESULTS: Patients with the necrotic variant showed a significantly more marked extracapillary proliferation and interstitial accumulation of monocytes and T lymphocytes and, in the segmental areas of necrotizing and extracapillary lesions, infiltration of monocytes, deposition of fibrinogen, and expression of the adhesion molecule vascular cell adhesion molecule-1. No difference was found in the presenting clinical syndrome. The clinical course was frequently characterized by acute flare ups, and the progression to end-stage renal failure was more frequent, although actuarial renal survival was not significantly worse (P = 0.07). The aggressive treatment with steroids and cyclophosphamide, carried out in 20 of the 35 patients, has probably been beneficial, justifying the multicenter controlled trial that recently has been initiated. CONCLUSIONS: Vasculitic lesions of the glomerular capillaries, with histologic and immunohistological features similar to those of Henoch-Schönlein purpura and antineutrophil cytoplasmic antibody-positive renal vasculitis, were found in 10% of patients with idiopathic IgAN. Clinical features at presentation did not differ from those of the other patients with IgAN, and despite of the more frequent occurrences of recurrent acute flare ups, rapid progression to end-stage renal failure was a rare phenomenon, even in untreated patients.

Abstract: BACKGROUND: Tubulointerstitial fibrosis is an integral part of progressive renal disease. Human cortical fibroblasts are believed to be key effector cells in fibrogenesis. Thus, a reliable culture of these cells is necessary for studies of their pathophysiology. METHODS: Cortical fibroblast culture from routine kidney biopsies were analyzed and the cells were characterized. Indirect immunofluorescence staining was done after the first passage for cytokeratin, vimentin, alpha-smooth muscle actin, CD 44, CD 54, CD 68, collagen types I, III, and HLA-DR. We then assessed the utility of the putative fibroblast markers CD 90, prolyl-4-hydroxylase (P4H) and F1b in simultaneous stainings of tubular epithelial cells. RESULTS: During the study period, 49 biopsy cores were cultured and cortical fibroblasts could be successfully established in 21 cases (42.9%). There was no relation between the success rate of culture and the degree of interstitial fibrosis, but an association was seen with the time of completion of the first passage. There was a negative correlation between the extent of scarring and the percentage of cytokeratin positive cells (r = -0.66, p < 0.001). All primary fibroblasts were negative for factor VIII, HLA-DR, CD 68, and cytokeratin. They expressed alpha-smooth muscle actin and collagen types I and III to variable degrees. There was a robust correlation between the percentage of alpha-smooth muscle actin positive cells and interstitial scarring but no such association with collagen type I or type III positive cells. The three putative fibroblast markers did not prove useful in differentiating between tubular epithelial cells and fibroblasts. However, since only fibroblasts stained positive for CD 90 and negative for cytokeratin, these two markers may suffice to distinguish fibroblasts from other renal cellular elements. CONCLUSIONS: Cortical renal fibroblasts can be easily cultured from kidney biopsy cores, though the success rate of pure cultures is below 50%. Staining for CD 90 and cytokeratin may suffice for initial characterization of these cells.

Abstract: Although it is widely known that many macrophages are present in glomeruli of antineutrophil cytoplasmic antibody (ANCA)-positive renal vasculitis (ANCA + RV) and are believed to contribute to necrotizing extracapillary damage, their precise role is not yet completely understood, especially in humans. The goal of this study was to provide evidence of glomerular macrophage properties in human vasculitis. Twenty-five renal biopsies of ANCA + RV and 18 cases of cryoglobulinemic glomerulonephritis (cryoGN), a disease characterized by massive glomerular macrophage infiltration but absence of necrotizing extracapillary lesions, were selected, and macrophage number, adhesion, acute activation, proliferation, and apoptosis were analyzed by immunohistochemistry and in situ hybridization. Accumulation of macrophages in ANCA + RV was found in areas of glomerular active lesions, whereas in cryoGN, they homogeneously occupied the entire glomerular tuft. Considering the areas of accumulation, comparable macrophage numbers were detected in both diseases. Glomerular vascular cell adhesion molecule-1 was found only in ANCA + RV and only in areas of active lesions. Acute macrophage activation (HLA class II, 27E10) and proinflammatory cytokine production (tumor necrosis factor-alpha, interleukin-1alpha) were prominent in ANCA + RV, whereas in cryoGN, 30% of glomerular macrophages seemed activated and cytokine expression was limited to a few glomerular cells (P: = 0.01). Moreover, only in ANCA + RV proliferative markers were shown on glomerular macrophages and apoptotic macrophages were found. From the data, it seems that ANCA + RV and cryoGN differ profoundly in macrophage properties, namely adhesion, proliferation, and apoptotic clearance. Moreover, acute activation and cytokine production seem to be present in a greater number of macrophages in ANCA + RV, giving this disease a stronger severity that could be taken into account for therapeutic strategies.

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Abstract: The hallmark of Berger's disease is the mesangial and/or mesangioparietal deposition of IgA as the predominant or sole immunoglobulin. Despite similar appearance to the immunohistological pattern, morphological glomerular lesions differ in that they are wide ranging and variable, making precise and uniform classificatory approaches extremely difficult. The most characteristic and frequent abnormality is mesangial enlargement, which is produced by various combinations of excess of matrix and of hypercellularity, ranging from minimal to very extensive. In some cases the mesangial lesions are more severe giving a pattern of membrano-proliferative glomerulonephritis. The concomitant presence of necrotizing alterations of glomerular tuft with segmental extracapillary proliferation, similar to capillaritis of Henoch-Schönlein purpura and ANCA associated vasculitis, is now well documented and recognized by researchers. This similarity with vasculitic lesions is confirmed by the strong positivity of fibrinogen, of VCAM-1, and of the accumulation of monocytes within the same areas of segmental necrotic glomerular lesions. These active lesions appear to play a crucial role in the progression of the disease due to repeat formations of necrotizing/extracapillary alterations with subsequent glomerular sclerosis and fibrous adhesions. In the last decade, many groups of investigators have focused their attention on tubulo-interstitial lesions in IgA nephropathy, in particular, on leukocyte infiltration and intersitial fibrosis, demonstrating that the impairment of the glomerular filtration rate and the progression of the disease correlate better with tubulo-interstitial damage than with the degree of glomerular damage. This has also been confirmed by studies with repeat biopsies. Moreover, the recent availability of immunohistochemical and in situ hybridation methods that allow more precise evaluations of infiltrating cells and of numerous factors secreted by these cells (chemokines, cytokines, adhesion molecules etc ...) offers us incredible opportunities to expand our knowledge on mechanisms involved in the inflammatory process and in the progression of the disease.

Abstract: BACKGROUND: Among our cases of IgA glomerulonephritis (IgAGN), 10% show necrotizing/extracapillary lesions involving a small percentage of glomeruli and associated with a certain degree of inflammation in absence of glomerular and interstitial scarring. In our experience, also in repeat biopsies, these cases of IgAGN have a worse prognosis probably because necrotizing/extracapillary lesions can repeat and accumulate, leading to the progression of damage. As it is well known that transforming growth factor-beta (TGF-beta) and endothelin-1 (ET-1) are key-factors in the progression of glomerulonephritis, aim of the study was to examine their expression in renal biopsies of primary IgAGN with necrotizing/crescentic lesions in complete absence of interstitial fibrosis. To obtain information about the mitogenic effect of ET-1, the expression of c-fos, whose upregulation by ET-1 has been established in culture, was also studied. METHODS: Eighteen renal biopsies of patients with necrotizing/crescentic IgAGN were examined by immunohistochemistry with antibodies against TGF-beta, ET-1 and c-fos. The results were compared with those obtained on 22 cases of IgAGN characterized only by pure mesangial proliferation and 25 IgAGN biopsies with advanced, not active, glomerulointerstitial lesions. RESULTS: In necrotizing/crescentic IgAGN glomerular TGF-beta appeared more positive than in cases characterized only by pure mesangial proliferation and was especially expressed on cellular crescents. In the interstitium, TGF-beta, ET-1 and c-fos were expressed by infiltrating leukocytes, tubules, and small vessels. This positivity, although similar as localization, was less diffuse than in biopsies with advanced interstitial damage, but significantly greater than in cases with pure mesangial proliferation. CONCLUSIONS: Positivity of TGF-beta on cellular crescents is similar to that observed from other authors in different types of necrotizing/crescentic human glomerulonephritis and supports our hypothesis that this is a peculiar type of IgAGN. Moreover, interstitial expression of TGF-beta, ET-1 and c-fos in biopsies with glomerular active lesions but complete absence of interstitial fibrosis may potentially represent a signal of activation of mechanisms that induce and amplify the damage leading to further progression of the disease.

Abstract: Clinicomorphological features of 11 cases of non-crescentic acute post-streptococcal glomerulonephritis (APSGN) were reviewed. Intraglomerular and interstitial leukocytes and their possible correlation with the adhesion molecules intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and endothelial-leukocyte adhesion molecule-1 (ELAM-1/E-selectin) were investigated by an immunohistochemical method. Intraglomerular leukocytes were primarily granulocytes (11.4 +/- 10 cells/glomerular cross-section) and monocytes-macrophages (13.4 +/- 19.4 cells/glomerular cross-section). The granulocytes outnumbered monocytes-macrophages in 7 of 11 specimens. The number of intraglomerular leukocytes correlated with proteinuria at the time of renal biopsy. Intraglomerular ICAM-1 staining was strongly positive in all biopsies, especially when intraglomerular monocytes-macrophages prevailed. Expression of intraglomerular VCAM-1 and E-selectin in diseased kidneys did not differ from that in normal kidneys. Interstitial leukocytes were primarily monocytes-macrophages (158.9 +/- 96.8 cells/mm2) and T lymphocytes (102.2 +/- 63.9 cells/mm2). The number of interstitial leukocytes, especially monocytes-macrophages, correlated with serum creatinine level at the time of biopsy. Interstitial ICAM-1 staining was strongly positive on tubules, peritubular capillaries, and small vessels. The tubular positivity for ICAM-1 correlated with the number of interstitial monocytes-macrophages. Interstitial VCAM-1 and E-selectin were expressed as in normal kidney tissues. The data from this study demonstrate that APSGN is characterized by the presence of both intraglomerular and interstitial leukocyte infiltration, correlating respectively with proteinuria and serum creatinine at the time of renal biopsy. Among the adhesion molecules studied, ICAM-1 seems the most involved in leukocyte recruitment, especially in that of monocytes-macrophages.

Abstract: In renal biopsy specimens from 15 patients with antineutrophil cytoplasmic autoantibody (ANCA)-associated renal vasculitis, the infiltrating intraglomerular and interstitial leukocytes were localized and the adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) and the cytokine interleukin-1 alpha (IL-1 alpha) were studied by an immunohistochemical method. Intraglomerular leukocytes were mainly macrophages (13.46 +/- 9.29 cells/glomerular cross-section) and, to a lesser extent, T lymphocytes (4.61 +/- 2.81 cells/glomerular cross-section). Staining with VCAM-1, which was negative in the undamaged tufts, was strongly positive in necrotizing-extracapillary lesions. Staining with ICAM-1 was also present in the damaged tufts, but its pattern was more diffuse. Intraglomerular IL-1 alpha was found in all biopsy specimens. Where the Bowman's capsule was not damaged, the periglomerular infiltrating cells were macrophages (42.6 +/- 25.2 cells/glomerular cross-section) and T lymphocytes (51.06 +/- 33.0 cells/glomerular cross-section). When there was a granulomatous lesion involving the glomerulus, the number of cells per granulomatous area revealed a massive number of CD45-positive leukocytes (345.83 +/- 237.47 cells/granulomatous lesion), many of them positive for activity markers (HLA-DR, IL-2R), adhesion molecules, and IL-1 alpha. Many activated cells were also present in interstitial areas of perivascular clusters of leukocytes, in which T lymphocytes (prevalently CD4+ cells) outnumbered the macrophages (331.55 +/- 207.85 cells/0.05 mm2 area v 125.68 +/- 60.57 cells/0.05 mm2 area). Adhesion molecules and IL-1 alpha were found in both tubular and vascular areas in all biopsy specimens. Our data strongly support the involvement of both the adhesion molecules ICAM-1 and VCAM-1 in the recruitment of intraglomerular leukocytes in renal vasculitis, indicate that VCAM-1 is a very good marker of necrotizing-extracapillary damage, and suggest its crucial connection with the macrophage recruitment in these vasculitic lesions. The presence of histochemically detectable levels of IL-1 alpha in glomeruli, tubules, and vessels and on some inflammatory cells supports its involvement in the vasculitic lesions, probably by triggering a positive feedback that increases the damage.

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Abstract: The evidence that tubular damage, interstitial infiltration, and interstitial fibrosis occur in all glomerular diseases, either immunologically or non-immunologically mediated, is reviewed on the basis of personal data and data from the literature. The proposed mechanisms linking glomerular and tubular damage to the interstitial recruitment of mononuclear leukocytes and fibroblast proliferation, with abnormal extracellular matrix production leading to interstitial fibrosis, also are analyzed. The role of persistent heavy proteinuria and exposure to proinflammatory cytokines in inducing the damage of the tubular epithelial cells, with consequent acquisition by these cells of the ability to interact as antigen-presenting cells with T lymphocytes, is especially emphasized. Finally, the importance of the tubulointerstitial damage as a marker of unfavorable prognosis in glomerular diseases is documented.

Abstract: Factor XIII (FXIII) is a plasma pro-transglutaminase consisting of A and B subunits in a tetrameric structure. A cellular form of FXIII consisting exclusively of A subunits exists in platelets and monocytes: monocyte FXIII may be involved in connective tissue organization. To evaluate the expression and diagnostic significance of FXIII A subunit (FXIIIA) in acute leukemia, we performed an immunocytochemical study (PAP technique) with rabbit antiserum against FXIIIA on leukemic blasts of 48 cases. FXIIIA was detected only in myelomonocytic (M4), monocytic (M5) and megakaryocytic (M7) cases: in M4 and M5 samples the amount of blast cytoplasmic FXIIIA was closely correlated with the expression of monocyte-specific antigenic and cytochemical markers. Our data show immunocytochemical detection of FXIIIA to be useful for acute leukemia characterization.

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