Effacement Of Foot Processes Research Articles

Minimal Change Disease.

Minimal change disease (MCD) is a major cause of idiopathic nephrotic syndrome (NS), characterized by intense proteinuria leading to edema and intravascular volume depletion. In adults, it accounts for approximately 15% of patients with idiopathic NS, reaching a much higher percentage at younger ages, up to 70%-90% in children >1 year of age. In the pediatric setting, a renal biopsy is usually not performed if presentation is typical and the patient responds to therapy with oral prednisone at conventional doses. Therefore, in this setting steroid-sensitive NS can be considered synonymous with MCD. The pathologic hallmark of disease is absence of visible alterations by light microscopy and effacement of foot processes by electron microscopy. Although the cause is unknown and it is likely that different subgroups of disease recognize a different pathogenesis, immunologic dysregulation and modifications of the podocyte are thought to synergize in altering the integrity of the glomerular basement membrane and therefore determining proteinuria. The mainstay of therapy is prednisone, but steroid-sensitive forms frequently relapse and this leads to a percentage of patients requiring second-line steroid-sparing immunosuppression. The outcome is variable, but forms of MCD that respond to steroids usually do not lead to chronic renal damage, whereas forms that are unresponsive to steroids may subsequently reveal themselves as FSGS. However, in a substantial number of patients the disease is recurrent and requires long-term immunosuppression, with significant morbidity because of side effects. Recent therapeutic advances, such as the use of anti-CD20 antibodies, have provided long-term remission off-therapy and suggest new hypotheses for disease pathogenesis.

A case of rapid progression of Fabry nephropathy with remarkable glomerulomegaly: a case report and mini literature review of weak response to enzyme replacement therapy (ERT)

Fabry disease is a rare X-linked hereditary disorder (Xq22) caused by a deficiency in alpha-galactosidase (α-GAL) activity. This enzyme deficit results in the systemic accumulation of glycophospholipids, leading to multi-organ failure including the heart, kidneys, and brain. Enzyme replacement therapy (ERT) improves the prognosis of patients with Fabry disease. We describe a case showing progressive renal failure despite ERT. An 18-year-old obese male patient (body mass index (BMI) 29.9 kg/m2) was admitted for detailed examination of mild degree hypertension (150/65 mmHg) and proteinuria occurring for 2 years prior to admittance. Laboratory tests revealed mostly normal kidney function (serum creatinine 0.5 mg/dL, estimated glomerular filtration rate 181 mL/min/m2) with low α-GAL activity, a significant level of proteinuria (0.5–1.0 g/day), and the presence of mulberry cells in the urinary sediment. Renal biopsy demonstrated marked glomerulomegaly with diffuse vacuolization of the glomerular epithelial cells and focal segmental glomerulosclerosis. Electron microscopy revealed typical zebra bodies in the glomerular epithelial cells and effacement of foot processes of the epithelium. We could not find any cause of glomerulomegaly except for obesity. α-GAL gene analysis revealed a missense mutation in R301Q. Although ERT with agalsidase α was initiated, his renal function declined, and hemodialysis was initiated at 22 years of age. We present a case of rapid progression of Fabry nephropathy despite ERT. As with other renal diseases, obesity may aggravate the progression of Fabry nephropathy.

Formation of tight junctions between neighboring podocytes is an early ultrastructural feature in experimental crescentic glomerulonephritis.

PurposeIn crescentic glomerulonephritis (CGN), the development of cellular bridges between podocytes and parietal epithelial cells (PECs) triggers glomerular crescent formation. However, the sequential changes in glomerular ultrastructure in CGN are not well defined. This study investigated the time course of glomerular ultrastructure in experimental CGN.MethodsTransmission electron microscopy (TEM) was performed using kidney samples from rats with nephrotoxic serum nephritis (NSN) from day 1 to day 14. Morphometric analysis was conducted on randomly selected glomeruli captured on TEM digital images.ResultsOn day 1 of NSN, there was widespread formation of focal contacts between the cell bodies of neighboring podocytes, and tight junctions were evident at the site of cell-to-cell contact. This was confirmed by the increased expression of the tight junction molecule, zonula occludens-1 (ZO-1), which localized to the points of podocyte cell–cell body contact. On day 2, the interpodocyte distance decreased and the glomerular basement membrane thickness increased. Foot process effacement (FPE) was segmental on day 3 and diffuse by day 5, accompanied by the formation of podocyte cellular bridges with Bowman’s capsule, as confirmed by a decrease in podocyte-to-PEC distance. Fibrinoid necrosis and cellular crescents were evident in all glomeruli by days 7 and 14. In vitro, the exposure of podocytes to macrophage-conditioned media altered cellular morphology and caused an intracellular redistribution of ZO-1.ConclusionThe formation of tight junctions between podocytes is an early ultrastructural abnormality in CGN, preceding FPE and podocyte bridge formation and occurring in response to inflammatory injury. Podocyte-to-podocyte tight junction formation may be a compensatory mechanism to maintain the integrity of the glomerular filtration barrier following severe endocapillary injury.

Prevalence of Glomerulopathies in Canine Mammary Carcinoma

The incidence and prevalence of paraneoplastic glomerulopathy, especially associated with carcinoma, are a matter of debate and the causal link between cancer and glomerular diseases remains unclear. The aim of this study was to evaluate renal biopsies of selected bitches with spontaneous mammary gland carcinoma. We hypothesized that dogs with mammary carcinomas would show histologic evidence of glomerular pathology. A prospective study was performed in dogs with naturally occurring mammary carcinoma that were undergoing tumor resection and ovariohysterectomy. We evaluated renal biopsies of 32 bitches with spontaneous mammary gland carcinoma and 11 control dogs without mammary gland neoplasia. Samples were obtained from the left kidney and the biopsy material was divided for light microscopy (LM), immunofluorescence (IF) and transmission electron microscopy (TEM). Light microscopy abnormalities were identified in 78.1% of dogs with mammary carcinoma (n = 25) and in none of the dogs in the control group. Focal glomerular mesangial matrix expansion was the most common alteration (n = 15, 60.0%), but mesangial cell proliferation (n = 9, 36.0%) and focal segmental glomerulosclerosis (n = 9, 36.0%), synechiae (n = 7, 28.0%), and globally sclerotic glomeruli (n = 6, 24.0%) were also frequent in dogs with malignancy. Immunofluorescence microscopy revealed strong IgM staining was demonstrated in 64.3% (n = 18) of carcinoma dogs. Transmission electron microscopy from dogs with carcinoma revealed slight changes, the most frequent of which was faint sub-endothelial and mesangial deposits of electron-dense material (78%). Mesangial cell interpositioning and segmental effacement of podocyte foot processes were identified in some specimens (45%). Changes in the glomerulus and proteinuria are common in dogs with naturally occurring mammary carcinoma and this condition appears to provide an excellent large animal model for cancer-associated glomerulopathy in humans.

Exogenous kallikrein protects against diabetic nephropathy

The kallikrein-kinin system has been shown to be involved in the development of diabetic nephropathy, but specific mechanisms are not fully understood. Here, we determined the renal-protective role of exogenous pancreatic kallikrein in diabetic mice and studied potential mechanisms in db/db type 2 diabetic and streptozotocin-induced type 1 diabetic mice. After the onset of diabetes, mice were treated with either pancreatic kallikrein (db/db+kallikrein, streptozotocin+kallikrein) or saline (db/db+saline, streptozotocin+saline) for 16 weeks, while another groupof streptozotocin-induced diabetic mice received thesame treatment after onset of albuminuria (streptozotocin'+kallikrein, streptozotocin'+saline). Db/m littermates or wild type mice were used as non-diabetic controls. Pancreatic kallikrein had no effects on body weight, blood glucose and blood pressure, but significantly reduced albuminuria among all three groups. Pathological analysis showed that exogenous kallikrein decreased thethickness of the glomerular basement membrane, protected against the effacement of foot process, the lossof endothelial fenestrae, and prevented the loss of podocytes in diabetic mice. Renal fibrosis, inflammation and oxidative stress were reduced in kallikrein-treated micecompared to diabetic controls. The expression of kininogen1, tissue kallikrein, kinin B1 and B2 receptors were all increased in the kallikrein-treated compared to saline-treated mice. Thus, exogenous pancreatic kallikrein both prevented and ameliorated diabetic nephropathy, which may be mediated by activating the kallikrein-kinin system.

Impact of long-term high-fat diet intake gestational protein-restricted offspring on kidney morphology and function

Emerging evidence highlights the far-reaching consequences of high-fat diet (HFD) and obesity on kidney morphological and functional disorders. In the present study, we aim to evaluate the effects of early HFD intake on renal function and morphology in maternal protein-restricted offspring (LP). LP and normal protein-intake offspring (NP) were fed HFD (LPH and NPH, respectively) or standard rodent (LPN and NPN) diet from the 8th to 13th week of age. Blood pressure, kidney function, immunohistochemistry and scanning electron microscopy were analyzed. Increased total cholesterol and low-density lipoprotein serum levels were observed in LPH offspring. The adiposity index was reduced in the (LPN) group and, conversely, increased in the NPH and LPH groups. Blood pressure was higher beyond the 10th week of age in the LPH group compared with the other groups. Decreased urinary sodium excretion was observed in LP offspring, whereas the HFD-treated groups presented a decreased urine pH in a time-dependent fashion. The LPN, NPH and LPH groups showed increased expression of type 1 angiotensin II (AngII) receptor (AT1R), TGF-β1, collagen and fibronectin in the kidneys. Moreover, the adult fetal-programmed offspring showed pronounced effacement of the podocyte foot process associated with the rupture of cell membranes and striking urinary protein excretion, exacerbated by HFD treatment. To the best of our knowledge, this is the first study demonstrating that young fetal-programmed offspring submitted to long-term HFD intake have increased susceptibility to renal structural and functional disorders associated with an accentuated stage of fibrosis and tubular dysfunction.

Effect of mycophenolic acid in experimental, nontransplant glomerular diseases: new mechanisms beyond immune cells

Mycophenolic acid (MPA) was introduced into clinical practice as immunosuppressive drug therapy to prevent allograft rejection. Since then, its clinical application has widened. Our goal was to review the lessons learned from experimental nontransplant glomerular disease models on the mechanisms of MPA therapy. T and B lymphocytes are preferentially dependent on de novo purine synthesis. By inhibiting the rate-limiting enzyme of de novo purine synthesis, MPA depletes the pool of deoxyguanosine triphosphate (dGTP) and inhibits proliferation of these immune cells. Furthermore, MPA can also induce apoptosis of immune cells and is known to inhibit synthesis of fucose- and mannose-containing membrane glycoproteins altering the surface expression and binding ability of adhesion molecules. However, MPA exerts a direct effect also on nonimmune cells. Mesangial cells are partially dependent on de novo purine biosynthesis and are thus susceptible to MPA treatment. Additionally, MPA can inhibit apoptosis in podocytes and seems to be beneficial in preserving the expression of nephrin and podocin, and by attenuation of urokinase receptor expression leads to decreased foot-process effacement. In summary, our manuscript sheds light on the molecular mechanisms underlying the antiproteinuric effect of MPA. Overall, MPA is an excellent treatment option in many immunologic glomerulopathies because it possesses immunosuppressive properties, has a remarkable effect on nonimmune cells and counteracts the proliferation of mesangial cells, expansion of mesangial matrix, and foot-process effacement of podocytes combined with a low systemic toxicity.

Epigenetic Regulation Through SIRT1 in Podocytes.

SIRT1 is an NAD-dependent deacetylase. One important role of SIRT1 is its deacetylation activity in the modulation of cell stress signals via epigenetics. In podocytes, SIRT1 regulates the expression of important genes such as PGC-1α, Foxo4, p65 and STAT3, which act to maintain podocyte function by modulating the levels of histone acetylation. Here, we confirmed that SIRT1 protects podocytes by maintaining PGC-1α via its deacetylase-activated transcriptional activity in mitochondria and podocytes. We then showed that the alteration of Foxo4 (forkhead box O4) acetylation and decrease in SIRT1 promote podocyte apoptosis in diabetic nephropathy, resulting in the gradual development of diabetic nephropathy. Next, we showed that advanced glycation end products (AGEs) induced p65 and STAT3 acetylation in human podocytes. Decreased Sirt1 activity in podocytes results in the development of proteinuria and kidney injury via the acetylation of p65 and STAT3. These findings suggest that the beneficial effects of SIRT1 in diabetic nephropathy act via the deacetylation of transcription factors. In addition to its essential role in regulating the epigenetics of podocytes, we recently showed that SIRT1 is necessary to maintaining the function of slit membranes and podocytes. The actin cytoskeleton becomes vulnerable to various stresses, including oxidative stress, which in turn leads to the derangement and effacement of foot processes, slit membrane dysfunction, and proteinuria. SIRT1 protects podocytes and prevents glomerular injury by deacetylating cortactin and changing cortactin localization, thereby maintaining the integrity of the actin cytoskeleton. We expect that SIRT1 will be shown to sufficiently suppress the development of kidney dysfunction and will be proven useful in the near future. The clinical application of SIRT1-activated chemical agents has just started, and results are eagerly anticipated.

Deletion of the Formin, Drf1, is Protective Against Renal Damage in a Murine Model of Diabetes

Our studies have shown the cytoplasmic domain of the receptor for advanced glycation endproducts (RAGE) binds to the formin molecule, diaphanous‐1 (mDia1). mDia1 is a member of the formin family of intracellular molecules involved in cellular migration which act as effectors of Rho GTPase signaling. In RAGE‐expressing cells devoid of Drf1 (gene encoding mDia1), incubation with RAGE ligands failed to generate reactive oxygen species or activate key signaling cellular stress pathways. Here, we sought to determine if mDia1 plays key roles in a murine model of diabetic nephropathy (DN). Our preliminary data reveal that mDia1 expression is increased in human and murine diabetic podocytes and parietal epithelial cells in a diffuse and global pattern compared to age‐matched controls. Furthermore, expression patterns of mDia1 are highly analogous to those of RAGE. While the role of RAGE has been shown to play a key role in the development of DN, the potential contribution of mDia1 has yet to be elucidated. Therefore, we tested the hypothesis that mDia1 contributes to the development and progression of diabetic renal disease in a murine model.Male wild‐type and Drf1‐null (WT, Drf1KO; all in the C57BL/6 background) mice were rendered diabetic at 6 weeks of age with streptozotocin and sacrificed after 3 or 6 months of diabetes. Kidneys were harvested and processed for histology and gene expression and stained with periodic‐acid Schiff (PAS) and semi‐quantitative scoring was used to determine the degree of mesangial sclerosis by average findings in >100 glomeruli/mouse (scale 0–3+; 0=absent, 1=mild, 2=moderate, 3=severe). Glomerular basement membrane (GBM) thickness and podocyte foot process effacement (FPE) were measured by ultrastructural analysis (>8 glomeruli/mouse). Gene expression of inflammatory markers (transforming growth factor beta; Tgfb, interleukin 6; Il6, and monocyte chemoattractant protein 1; Ccl2) were assessed by quantitative real time PCR using RNA prepared from whole kidney cortex and normalized to beta‐actin.This preliminary study suggests that deletion of Drf1 in mice results in a substantial protection against indices of DN by reducing podocyte effacement, inflammation and fibrosis in type 1 DM. Histological and microscopic observations show that mDiaKO mice have a reduced GBM, less podocyte FPE and a decrease in mesangial sclerosis compared to WT mice after 6 months of diabetes. Genotype WT Drf1KO ND (n=5) DM (n=5) ND (n=5) DM (n=5) GBM (nm) 217.3±14.1 288.5±17.46^ 228.3±16.5 246.0±23.2* FPE [%] 9.6±3.6 29.0±6.8^ 9.8±2.3* 13.0±4.7* MS 0.4±0.4 2.0±0.4^ 0.0±0.0* 1.3±0.6*# p<0.05 vs. WT ND, p<0.05 vs WT DM, p<0.05 vs Drf1KO ND. Values shown are Mean±SEM. Ratio of target gene fold‐change normalized to beta‐actin. Gene expression of inflammatory markers in diabetes is downregulated with deletion of mDia1 compared to WT after both 3 and 6 months. Condition 3 months 6 months WTND Drf1KOND WTDM Drf1KODM WTND Drf1KOND WTDM Drf1KODM n=3 n=3 n=3 n=3 n=3 n=3 n=5 n=3 Tgfb 1 1.02 2.67^# 1.09* 1 0.52ab 7.32ac 0.82abc Il6 1 0.96 1.49^# 1.21.^*# 1 0.52ab 2.13ac 0.73abc Ccl2 1 1.01 1.43^# 1.17^*# 1 0.75ab 1.82ac 1.12abc p<0.05 vs. WT ND 3 months, p<0.05 vs WT DM 3 months, p<0.05 vs Drf1KO ND 3 months, p<0.05 vs WT ND 6 months, p<0.05 vs WT DM 6 months, p<0.05 vs Drf1KO ND 6 months. Values shown are Mean±SEM.

GADD45B mediates podocyte injury in zebrafish by activating the ROS-GADD45B-p38 pathway.

GADD45 gene has been implicated in cell cycle arrest, cell survival or apoptosis in a cell type specific and context-dependent manner. Members of GADD45 gene family have been found differentially expressed in several podocyte injury models, but their roles in podocytes are unclear. Using an in vivo zebrafish model of inducible podocyte injury that we have previously established, we found that zebrafish orthologs of gadd45b were induced upon the induction of podocyte injury. Podocyte-specific overexpression of zebrafish gadd45b exacerbated edema, proteinuria and foot-process effacement, whereas knockdown of gadd45b by morpholino-oligos in zebrafish larvae ameliorated podocyte injury. We then explored the role of GADD45B induction in podocyte injury using in vitro podocyte culture. We confirmed that GADD45B was significantly upregulated during the early phase of podocyte injury in cultured human podocytes and that podocyte apoptosis induced by TGF-β and puromycin aminonucleoside (PAN) was aggravated by GADD45B overexpression but ameliorated by shRNA-mediated GADD45B knockdown. We also showed that ROS inhibitor NAC suppressed PAN-induced GADD45B expression and subsequent activation of p38 MAPK pathway in podocytes and that inhibition of GADD45B diminished PAN-induced p38 MAPK activation. Taken together, our findings demonstrated that GADD45B has an important role in podocyte injury and may be a therapeutic target for the management of podocyte injury in glomerular diseases.

Plasma Soluble Urokinase Receptor Level Is Correlated with Podocytes Damage in Patients with IgA Nephropathy.

BackgroundFocal segmental glomerulosclerosis (FSGS) lesions are similar in characteristics to S lesions of the Oxford classification of IgA nephropathy (IgAN) and may predict poor prognosis. In the present study, we aimed to explore the association between plasma soluble urokinase receptor (suPAR) levels and S lesions and podocytes damage in IgAN patients.MethodsWe enrolled 569 IgAN patients with follow-up data and detected plasma suPAR levels at renal biopsy by enzyme-linked immunosorbent assay.ResultsPlasma suPAR levels in IgAN patients with or without S lesions did not differ significantly (P = 0.411). However, suPAR levels were positively correlated with proteinuria (r = 0.202, P < 0.001), and negatively correlated with estimated glomerular filtration rate (eGFR, r = –0.236, P < 0.001). In the partial correlation to adjust for eGFR, plasma suPAR levels remained positively correlated with proteinuria (r = 0.112, P = 0.023). In a Cox proportional hazards model, higher levels of plasma suPAR were not associated with poor renal outcome. Plasma suPAR levels of IgAN and primary FSGS patients with nephrotic syndrome were not significantly different (P = 0.306). Plasma suPAR levels in patients with extensive effacement of the epithelial cell foot processes of glomerular podocytes were significantly higher than those with segmental effacement on the basis of comparable eGFR (P = 0.036).ConclusionsIn IgAN patients, plasma suPAR levels were not associated with S lesions. However, they were positively associated with proteinuria and negatively associated with eGFR. In addition, plasma suPAR levels were positively associated with the effacement degree of the foot processes, which might partially contribute to the development of proteinuria in patients with IgAN.

TRPC6 channel as an emerging determinant of the podocyte injury susceptibility in kidney diseases.

Podocytes (terminally differentiated epithelial cells of the glomeruli) play a key role in the maintenance of glomerular structure and permeability and in the incipiency of various renal abnormalities. Injury to podocytes is considered a major contributor to the development of kidney disease as their loss causes proteinuria and progressive glomerulosclerosis. The physiological function of podocytes is critically dependent on proper intracellular calcium handling; excessive calcium influx in these cells may result in the effacement of foot processes, apoptosis, and subsequent glomeruli damage. One of the key proteins responsible for calcium flux in the podocytes is transient receptor potential cation channel, subfamily C, member 6 (TRPC6); a gain-of-function mutation in TRPC6 has been associated with the onset of the familial forms of focal segmental glomerulosclerosis (FSGS). Recent data also revealed a critical role of this channel in the onset of diabetic nephropathy. Therefore, major efforts of the research community have been recently dedicated to unraveling the TRPC6-dependent effects in the initiation of podocyte injury. This mini-review focuses on the TRPC6 channel in podocytes and colligates recent data in an attempt to shed some light on the mechanisms underlying the pathogenesis of TRPC6-mediated glomeruli damage and its potential role as a therapeutic target for the treatment of chronic kidney diseases.

Recessive nephrocerebellar syndrome on the Galloway-Mowat syndrome spectrum is caused by homozygous protein-truncating mutations ofWDR73

We describe a novel nephrocerebellar syndrome on the Galloway-Mowat syndrome spectrum among 30 children (ages 1.0 to 28 years) from diverse Amish demes. Children with nephrocerebellar syndrome had progressive microcephaly, visual impairment, stagnant psychomotor development, abnormal extrapyramidal movements and nephrosis. Fourteen died between ages 2.7 and 28 years, typically from renal failure. Post-mortem studies revealed (i) micrencephaly without polymicrogyria or heterotopia; (ii) atrophic cerebellar hemispheres with stunted folia, profound granule cell depletion, Bergmann gliosis, and signs of Purkinje cell deafferentation; (iii) selective striatal cholinergic interneuron loss; and (iv) optic atrophy with delamination of the lateral geniculate nuclei. Renal tissue showed focal and segmental glomerulosclerosis and extensive effacement and microvillus transformation of podocyte foot processes. Nephrocerebellar syndrome mapped to 700 kb on chromosome 15, which contained a single novel homozygous frameshift variant (WDR73 c.888delT; p.Phe296Leufs*26). WDR73 protein is expressed in human cerebral cortex, hippocampus, and cultured embryonic kidney cells. It is concentrated at mitotic microtubules and interacts with α-, β-, and γ-tubulin, heat shock proteins 70 and 90 (HSP-70; HSP-90), and the carbamoyl phosphate synthetase 2/aspartate transcarbamylase/dihydroorotase multi-enzyme complex. Recombinant WDR73 p.Phe296Leufs*26 and p.Arg256Profs*18 proteins are truncated, unstable, and show increased interaction with α- and β-tubulin and HSP-70/HSP-90. Fibroblasts from patients homozygous for WDR73 p.Phe296Leufs*26 proliferate poorly in primary culture and senesce early. Our data suggest that in humans, WDR73 interacts with mitotic microtubules to regulate cell cycle progression, proliferation and survival in brain and kidney. We extend the Galloway-Mowat syndrome spectrum with the first description of diencephalic and striatal neuropathology.

Characterization of early disease status in treatment-naive male paediatric patients with Fabry disease enrolled in a randomized clinical trial.

Trial DesignThis analysis characterizes the degree of early organ involvement in a cohort of oligo-symptomatic untreated young patients with Fabry disease enrolled in an ongoing randomized, open-label, parallel-group, phase 3B clinical trial.MethodsMales aged 5–18 years with complete α-galactosidase A deficiency, without symptoms of major organ damage, were enrolled in a phase 3B trial evaluating two doses of agalsidase beta. Baseline disease characteristics of 31 eligible patients (median age 12 years) were studied, including cellular globotriaosylceramide (GL-3) accumulation in skin (n = 31) and kidney biopsy (n = 6; median age 15 years; range 13–17 years), renal function, and glycolipid levels (plasma, urine).ResultsPlasma and urinary GL-3 levels were abnormal in 25 of 30 and 31 of 31 patients, respectively. Plasma lyso-GL-3 was elevated in all patients. GL-3 accumulation was documented in superficial skin capillary endothelial cells (23/31 patients) and deep vessel endothelial cells (23/29 patients). The mean glomerular filtration rate (GFR), measured by plasma disappearance of iohexol, was 118.1 mL/min/1.73 m2 (range 90.4–161.0 mL/min/1.73 m2) and the median urinary albumin/creatinine ratio was 10 mg/g (range 4.0–27.0 mg/g). On electron microscopy, renal biopsy revealed GL-3 accumulation in all glomerular cell types (podocytes and parietal, endothelial, and mesangial cells), as well as in peritubular capillary and non-capillary endothelial, interstitial, vascular smooth muscle, and distal tubules/collecting duct cells. Lesions indicative of early Fabry arteriopathy and segmental effacement of podocyte foot processes were found in all 6 patients.ConclusionsThese data reveal that in this small cohort of children with Fabry disease, histological evidence of GL-3 accumulation, and cellular and vascular injury are present in renal tissues at very early stages of the disease, and are noted before onset of microalbuminuria and development of clinically significant renal events (e.g. reduced GFR). These data give additional support to the consideration of early initiation of enzyme replacement therapy, potentially improving long-term outcome.Trial RegistrationClinicalTrials.gov NCT00701415

Glomerular endothelial cell injury and focal segmental glomerulosclerosis lesion in idiopathic membranous nephropathy.

BackgroundFocal segmental glomerulosclerosis (FSGS) lesions have often been discussed as a negative predictor in idopathic membranous nephropathy (MN). The mechanism of the development of FSGS lesion in MN is still uncertain.MethodsFrom 250 cases of MN, 26 cases contained FSGS lesion. We compared the clinicopathological characteristics between MN cases with FSGS lesion [MN-FSGS(+)] and MN without FSGS lesion [MN-FSGS(−)], matched for gender, age, stage of MN.ResultsThe glomerular filtration rate (eGFR) was significantly lower in MN-FSGS(+) cases compared to MN-FSGS(−), although nephrotic syndrome, hematuria, and systolic blood pressure levels were not significantly different between the two groups. Pathologically, glomeruli in MN-FSGS(+) cases showed narrowing and loss of glomerular capillaries with separating from GBM or disappearance of CD34+ endothelial cells, and accumulation of extracellular matrix (ECM) in capillary walls, indicating the development of glomerular capillary injury. These findings of endothelial injury were seen even in MN-FSGS(−) cases, but they were more prominent in MN-FSGS(+) than MN-FSGS(−) by computer assessed morphometric analysis. In MN-FSGS(+) cases, 44 out of 534 glomeruli (8.2%) contained FSGS lesions (n = 31, NOS lesion; n = 13, perihilar lesion). Significant thickness of GBM with ECM accumulation was evident in MN-FSGS(+) cases. Podocyte injury with effacement of foot processes was also noted, but the expression of VEGF on podocytes was not different between the two groups, which suggests that the significant thickness of capillary walls may influence the function of VEGF from podocyte resulting in the glomerular capillary injury that contribute to the development of FSGS lesion in MN.ConclusionGlomerular capillary injury was seen in all MN cases. Furthermore, the prominent injuries of glomerular capillaries may be associated with the deterioration of eGFR and the formation of FSGS lesions in MN.

Proregenerative Microenvironment Triggered by Donor Mesenchymal Stem Cells Preserves Renal Function and Structure in Mice with Severe Diabetes Mellitus.

The aim of our work was to evaluate, in an animal model of severe diabetes mellitus, the effect of mesenchymal stem cells (MSCs) administration on diabetic nephropathy (DN) progression. After diabetes induction, one group of mice received the vehicle (DM) and other group received a single dose of MSCs (DM + MSCs). DM + MSCs mice showed a significant improvement in functional parameters of the kidney compared with untreated mice. While DM mice presented marked histopathological changes characteristics of advanced stages of DN (fibrosis, glomerulosclerosis, glomerular basement membrane thickening, capillary occlusion, decreased podocyte density, and effacement of foot processes), DM + MSCs mice showed only slight tubular dilatation. The renoprotection was not associated with an improvement in diabetic condition and very low number of donor cells was found in the kidney of DM + MSCs mice, suggesting that renoprotection could be mediated by paracrine effects. Indeed, DM + MSC mice presented increased renal proliferation index, decreased renal apoptotic index and the restoration of proregenerative factors, and anti-inflammatory cytokines levels. Moreover, macrophage infiltration and oxidative stress damage were also reduced in DM + MSCs mice. Our data demonstrate that MSC administration triggers a proregenerative microenvironment in DN kidney, which allows the preservation of the renal function even if diabetes was uncorrected.

CRB2 Mutations Produce a Phenotype Resembling Congenital Nephrosis, Finnish Type, with Cerebral Ventriculomegaly and Raised Alpha-Fetoprotein

We report five fetuses and a child from three families who shared a phenotype comprising cerebral ventriculomegaly and echogenic kidneys with histopathological findings of congenital nephrosis. The presenting features were greatly elevated maternal serum alpha-fetoprotein (MSAFP) or amniotic fluid alpha-fetoprotein (AFAFP) levels or abnormalities visualized on ultrasound scan during the second trimester of pregnancy. Exome sequencing revealed deleterious sequence variants in Crumbs, Drosophila, Homolog of, 2 (CRB2) consistent with autosomal-recessive inheritance. Two fetuses with cerebral ventriculomegaly and renal microcysts were compound heterozygotes for p.Asn800Lys and p.Trp759Ter, one fetus with renal microcysts was a compound heterozygote for p.Glu643Ala and p.Asn800Lys, and one child with cerebral ventriculomegaly, periventricular heterotopias, echogenic kidneys, and renal failure was homozygous for p.Arg633Trp in CRB2. Examination of the kidneys in one fetus showed tubular cysts at the corticomedullary junction and diffuse effacement of the epithelial foot processes and microvillous transformation of the renal podocytes, findings that were similar to those reported in congenital nephrotic syndrome, Finnish type, that is caused by mutations in nephrin (NPHS1). Loss of function for crb2b and nphs1 in Danio rerio were previously shown to result in loss of the slit diaphragms of the podocytes, leading to the hypothesis that nephrosis develops from an inability to develop a functional glomerular barrier. We conclude that the phenotype associated with CRB2 mutations is pleiotropic and that the condition is an important consideration in the evaluation of high MSAFP/AFAFP where a renal cause is suspected.

Structural analysis of how podocytes detach from the glomerular basement membrane under hypertrophic stress.

Podocytes are lost by detachment from the GBM as viable cells; details are largely unknown. We studied this process in the rat after growth stimulation with FGF-2. Endothelial and mesangial cells responded by hyperplasia, podocytes underwent hypertrophy, but, in the long run, developed various changes that could either be interpreted showing progressing stages in detachment from the GBM or stages leading to a tighter attachment by foot process effacement (FPE). This occurred in microdomains within the same podocyte; thus, features of detachment and of reinforced attachment may simultaneously be found in the same podocyte. (1) Initially, hypertrophied podocytes underwent cell body attenuation and formed large pseudocysts, i.e., expansions of the subpodocyte space. (2) Podocytes entered the process of FPE starting with the retraction of foot processes (FPs) and the replacement of the slit diaphragm by occluding junctions, thereby sealing the filtration slits. Successful completion of this process led to broad attachments of podocyte cell bodies to the GBM. (3) Failure of sealing the slits led to gaps of varying width between retracting FPs facilitating the outflow of the filtrate from the GBM. (4) Since those gaps are frequently overarched by broadened primary processes, the drainage of the filtrate into the Bowman’s space may be hindered leading to the formation of small pseudocysts associated with bare areas of GBM. (5) The merging of pseudocysts created a system of communicating chambers through which the filtrate has to pass to reach Bowman’s space. Multiple flow resistances in series likely generated an expansile force on podocytes contributing to detachment. (6) Such a situation appears to proceed to complete disconnection generally of a group of podocytes owing to the junctional connections between them. (7) Since such groups of detaching podocytes generally make contact to parietal cells, they start the formation of tuft adhesions to Bowman’s capsule.

Focal and segmental glomerulosclerosis: clinical and kidney biopsy correlations.

BackgroundPrimary focal segmental glomerulosclerosis (FSGS) is a common glomerular disease in adults and ranks among the top causes of a primary glomerular disease causing end-stage renal disease (ESRD). Primary FSGS is, however, a diagnosis of exclusion and distinction between primary versus secondary FSGS is not always obvious, resulting in a number of patients with secondary FSGS undergoing unnecessary immunosuppressive therapy.MethodsWe reviewed the Mayo Clinic Renal Pathology Database for patients with a diagnosis of FSGS on native renal biopsy and divided the patients into nephrotic syndrome-associated (NS-associated) and non-nephrotic syndrome-associated (NNS-associated) FSGS as a first approximation followed by dividing the lesion according to the degree of foot process effacement (FPE) on electron microscopy (EM) examination.ResultsA total of 41 patients with FSGS with complete evaluation were identified. Of these, 18 were classified as having NS and 23 were classified as having NNS. Baseline characteristics (age, gender, body mass index, serum creatinine and hematuria) were not different between the groups. All of the patients with NS showed diffuse FPE ranging from 80 to 100% (mean 96%). On the other hand, of the 23 patients in the NNS group, 22 had segmental FPE and showed patchy effacement, with all cases showing 20–60% FPE (mean of 48%).ConclusionAdult patients presenting with NS, an FSGS lesion on LM, extensive FPE (≥80%) on EM examination and no risk factors associated with secondary FSGS are likely to have primary FSGS. Conversely, the absence of NS in a patient with segmental FPE on EM strongly suggests a secondary FSGS. Dividing FSGS into the presence or absence of NS together with the degree of FPE on EM examination is more helpful as it provides a more practical way to separate patients into cases of primary versus secondary FSGS.

Neph1 Is Reduced in Primary Focal Segmental Glomerulosclerosis, Minimal Change Nephrotic Syndrome, and Corresponding Experimental Animal Models of Adriamycin-Induced Nephropathy and Puromycin Aminonucleoside Nephrosis

Background/Aims: The transmembrane proteins Neph1 and nephrin form a complex in the slit diaphragm (SD) of podocytes. As recent studies indicate an involvement of this complex in the polymerization of the actin cytoskeleton and proteinuria, we wanted to study the subcellular localization of Neph1 in the normal human kidney and its expression in focal segmental glomerulosclerosis (FSGS), minimal change nephrotic syndrome (MCNS), and the corresponding experimental models of Adriamycin-induced nephropathy (ADR) and puromycin aminonucleoside nephrosis (PAN). All these disorders are characterized by substantial foot process effacement (FPE) and proteinuria. Materials and Methods: Kidney biopsies from patients with primary FSGS (perihilar type) and MCNS were compared to normal renal tissue. Mouse and rat kidney cortices from days 7 and 14 after Adriamycin injection and days 2 and 4 after puromycin aminonucleoside injection, respectively, were compared to control mouse and rat kidney. Polyclonal antibodies against Neph1 and nephrin were used for immunoelectron microscopy, and semiquantification was performed. Results: We localized Neph1 mainly to, and in close proximity to, the SD. Double staining of Neph1 and nephrin showed the proteins to be in close connection in the SD. The total amount of Neph1 in the podocytes was significantly reduced in FSGS, MCNS, ADR, and PAN. The reduction of Neph1 was also seen in areas with and without FPE. Nephrin was reduced in MCNS and PAN but unchanged in FSGS. Conclusion: With nephrin (but not Neph1) unchanged in FSGS, there might be a disruption of the complex and an involvement of Neph1 in its pathogenesis.