Activation of RhoA in podocytes induces focal segmental glomerulosclerosis

Proper organization of the actin cytoskeleton is essential for the normal structure and function of podocytes. RhoA modulates actin dynamics but its role in podocyte biology is controversial. Here, we generated transgenic mice that express a constitutively active form of RhoA in a podocyte-specific and doxycycline-inducible manner. Induction of activated RhoA with doxycycline resulted in significant albuminuria. Furthermore, both the degree of albuminuria and the histologic changes in the glomerulus positively correlated with the level of constitutively active RhoA expression: low levels of expression associated with segmental foot-process effacement without changes observable by light microscopy, whereas higher levels of expression associated with both extensive foot-process effacement and histologic features of focal segmental glomerulosclerosis (FSGS). In addition, induction of activated RhoA markedly upregulated glomerular mRNA expression of fibronectin and collagen IA1, and the degree of upregulation positively correlated with the level of albuminuria. Withdrawal of doxycycline led to a decline in albuminuria toward basal levels in most mice, but heavy albuminuria persisted in some mice. Taken together, these data suggest that activation of RhoA in podocytes leads to albuminuria accompanied by a range of histologic changes characteristic of minimal change disease and FSGS in humans. Although most changes are reversible, severe and prolonged activation of RhoA may cause irreversible glomerulosclerosis.     

Immunosuppressive treatment in primary focal segmental glomerulosclerosis

Background: The therapeutic effects of immunosuppressive agents such as cyclosporin A, mycophenolate mofetil, rituximab and sirolimus on primary focal segmental glomerulosclerosis (FSGS) remain controversial. The present study was intended to review and analyze the treatment results of immunosuppressive agents for primary FSGS in child and adult patients. Methods: Complete remission rates and partial remission rates were extracted from published articles and analyzed using statistical tests. Results: Cyclosporin A was effective in the treatment of child and adult patients with idiopathic FSGS. Rituximab therapy displayed a higher complete remission and partial remission rate in children than in adult FSGS patients. Conclusions: Multiple-center large-scale rigorous trials should be considered to evaluate the risk-benefit ratio of immunosuppressive treatment in patients with primary FSGS.     

The treatment of primary focal segmental glomerulosclerosis

Nephrotic patients with primary focal segmental glomerulosclerosis (FSGS) have a poor prognosis with 50% progressing to end stage renal disease (ESRD) over 3 to 8 years. The achievement of a remission in proteinuria has been associated with a significantly improved renal survival as compared to those patients not attaining a remission. Unfortunately, spontaneous remissions are rare in FSGS, and the response to therapy has historically been poor. Recent experience with more aggressive immunosuppressive therapy has lead to an increase in the remission rate for FSGS patients and given rise to optimism in the treatment of this glomerulopathy.     

Serum microRNAs levels in primary focal segmental glomerulosclerosis

Background

MicroRNAs (miRNAs, miRs) are involved in most physiological, developmental, and pathological processes. miR-192 and miR-205 are expressed preferentially in the renal cortex and closely relevant to the renal cell biology. In the present study, we aim to measure the serum levels of miR-192 and miR-205 and their correlation with clinicopathological data in patients with primary focal segmental glomerulosclerosis (FSGS) and minimal change disease (MCD).

Methods

Fifty-six patients (35 male, 21 female) with idiopathic nephrotic syndrome (FSGS 30, MCD 26) and 20 healthy controls were enrolled in the study. We quantified the serum levels of miR-192 and miR-205 in patients with FSGS and MCD by RT-qPCR.

Results

Patients with FSGS had higher serum levels of miR-192 and miR-205 than those with MCD (324.49?±?42.74 fmol/l versus 90.19?±?27.14 fmol/l, p?<?0.01, 2.25?±?0.69 fmol/l versus 0.60?±?0.51 fmol/l, p?<?0.01, respectively). The level of miR-192 was positively correlated with the proteinuria in patients with FSGS and MCD (r?=?0.62, p?<?0.001, r?=?0.84, p?<?0.001, respectively). Similarly, the level of miR-205 was positively correlated with the proteinuria in patients with FSGS (r?=?0.54, p?=?0.002). In addition, the serum level of miR-192 was significantly correlated with the degree of interstitial fibrosis in patients with FSGS (r?=?0.342, p?<?0.05).

Conclusions

miR-192 and miR-205 have the potential as markers to differentiate FSGS from MCD.     

局灶节段性肾小球硬化症大鼠尿足细胞动态检测及其意义

目的建立局灶节段性肾小球硬化症(FSGS)大鼠模型,观察尿中脱落的肾小球足细胞的变化,并探讨其意义。方法FSGS组(n=7):采用左颈静脉插管一次性缓慢注射嘌呤霉素核苷酸(PAN,9mg/100g体重的方法建立)FSGS大鼠模型。正常对照组(n=5):注射等量生理盐水,实验周期20周。动态检测24h尿蛋白定量;间接免疫荧光方法动态检测尿沉渣足细胞特异性标志蛋白podocalyxin(PCX)、Wilm'stumor鄄1(WT鄄1);20周末肾组织光镜下观察肾小球病变;电镜观察肾小球足细胞的改变;免疫荧光染色观察肾小球内PCX和成熟足细胞特异性标志蛋白synaptopodin(PP44)的表达。结果FSGS组大鼠24h尿蛋白定量在第天较注射前明显升高,第312天达到高峰[(672.74±98.72)比(19.31±3.15)mg/24h,P<0.01),此后开始下降,于第6周接近注射前水平,持续至11周[(35.46±14.88)比(19.31±3.15)mg/24h,P=0.0238];从12周开始再度缓慢升高,持续高水平至20周,为注射前近7倍[(140.61±68.90)比(19.31±3.15)mg/24h,P<0.01]。FSGS组大鼠从12周开始,尿足细胞出现阳性(>1～5个/HP),持续至20周。光镜显示,30%～50%肾小球出现不同程度的局灶节段性硬化;电镜证实足突部分融合并可见足突与基底膜剥离。足细胞特异标记蛋白PCX、PP44在肾小球节段性硬化部位呈现节段性缺失。对照     

Methylenetetrahydrofolate reductase polymorphism in childhood primary focal segmental glomerulosclerosis

AIM: The purpose of this study was to evaluate the association between the methylenetetrahydrofolate reductase (MTHFR) C/T polymorphism and the prevalence and course of focal segmental glomerulosclerosis (FSGS) in our pediatric population. METHODS: Genotypes for MTHFR were determined in 15 primary FSGS patients (male/female, 6/9) and 238 control subjects (male/female, 110/128) by the polymerase chain reaction and restriction fragment length polymorphism method. RESULTS: For the whole group, the genotype frequencies (CC/CT/TT) of MTHFR in FSGS and control subjects were almost comparable. The TT genotype was associated with early onset of the disease as compared with the CC genotype. Furthermore, all the patients with the TT genotype had steroid-resistant FSGS and developed into end-stage renal failure, while those carrying either CC or CT genotype did not. CONCLUSION: We speculate that the TT genotype may be associated with early development and progression of childhood FSGS. Confirmatory studies using larger and ethnically distinct populations are needed to reveal the role of homocysteine in FSGS with consideration of medical interventions.     

Eye involvement in children with primary focal segmental glomerulosclerosis

Distinct eye abnormalities have been described in children with nephrotic syndrome, particularly in diffuse mesangial sclerosis (i.e. Pierson syndrome). The aim of the study was to investigate whether there were any associated ocular anomalies in children with steroid-resistant nephrotic syndrome (SRNS), all of whom had revealed primary focal segmental glomerulosclerosis in biopsy. Thirty-three SRNS patients (16 male, 17 female) with a median age of 10.5 years (range 3–25 years) were enrolled in the study. Twenty steroid-sensitive nephrotic syndrome (SSNS) patients (ten male, ten female) with a median age of 8 years (range 3–15 years) served as controls. All SRNS patients were examined by mutational analysis for mutations in the NPHS2, WT1, and LAMB2 genes. Nine out of 33 SRNS patients (27.2%) showed various eye abnormalities. However, no abnormal ocular findings were detected in any of the SSNS patients. Abnormal eye findings detected in SRNS patients were anisometropic amblyopia (n = 4), Mittendorf’s dots (n = 4), myopic astigmatism (n = 3) and exotropia (n = 1). Macular pigment changes (n = 1), posterior subcapsular opacities (n = 1) and cataract (n = 1) were considered as steroid-induced side effects. In four patients, more than one eye abnormality was found. Mutational analysis for the NPHS2, WT1 and LAMB2 genes revealed disease-causing mutations in 24.2% of patients. Homozygous NPHS2 mutations were detected in five patients (15.1%), all of whom had parental consanguinity. In three patients (9%) from non-consanguineous parents, heterozygous de novo WT1 mutations were detected as disease-causing mutations. No LAMB2 mutation was detected in any patient. While four out of five (80%) patients with homozygous NPHS2 mutations showed at least one abnormal ocular finding (i.e. Mittendorf’s dot or anisometric amblyopia), none of the patients with a WT1 mutation had ocular involvement. In conclusion, ocular involvement may accompany SRNS caused by primary focal segmental glomerulosclerosis (FSGS). Ophthalmologic evaluation at the time of diagnosis might be beneficial to characterize further the spectrum of this possible association.     

Familial focal segmental glomerulosclerosis

There is increasing recognition of the importance of genetic factors in the development of focal segmental glomerulosclerosis and related proteinuric disorders. Recently, four genes have been identified which, when defective, cause focal segmental glomerulosclerosis or nephrosis. All of these genes appear to be important in the maintenance of glomerular podocyte function. However, not all cases of familial nephrosis or proteinuria are explained by defects in these genes.     

Idiopathic focal segmental glomerulosclerosis

Idiopathic focal segmental glomerulosclerosis (FSGS) is a primary glomerular disease that essentially represents a form of chronic, progressive renal fibrosis for which there is no discernible cause. Often presenting with or eventually manifesting the nephrotic syndrome, this disease is increasing in incidence in both children and adults. Therapy continues to be a challenge, although some patients clearly respond to corticosteroids or cyclosporine with a decrease in, or remission of, proteinuria. A favorable response is associated with a decreased likelihood of progression to kidney failure. Given our clinical experience and recent advances in understanding the genetics of FSGS, a stochastic model of disease pathogenesis can be proposed.     

A clinicopathologic study of primary focal segmental glomerulosclerosis in children

There is very little information in the literature on the treatment and prognosis of primary focal segmental glomerulosclerosis (FSGS) among children in Pakistan. This is a review of 94 children (≤16 years) with a diagnosis of primary FSGS who presented to the Sindh Institute of Urology and Transplantation between 1995 and 2008. The clinical records and original renal biopsy reports were reviewed to determine demographic, clinical, laboratory and pathologic features. Renal biopsies were studied by light microscopy, immunofluoroscence and electron microscopy. Thera-peutic regimens and response to therapy were analyzed. Majority of the children (60, 63.8%) had steroid-dependant nephrotic syndrome (SDNS) and 33 (35%) had steroid-resistant nephrotic syndrome (SRNS). Cyclosphosphamide was used in SDNS, and this produced complete remission (CR) in 25/36 (69.4%), partial response (PR) in 4/36 (11%) and no response in 7/36 (19.4%) cases. Cyclosporine was used in SRNS and some SDNS children, and showed a CR in 30 (52.6%), PR in 20 (35%) and no response in seven (12.2%) cases. Tacrolimus was used in seven (7.44%) children. CR was obtained in two (28.5%) and PR in five (71.4%) cases. Renal insufficiency developed in 12 (12.7%) children. Results from this study show that majority of the children with primary FSGS at our center could achieve high rates of sustained remission with second- and third-line immunosuppressive therapies with fairly good prognosis.     

Pathophysiology of focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a major cause of idiopathic steroid-resistant nephrotic syndrome (SRNS) and end-stage kidney disease (ESKD). In recent years, animal models and studies of familial forms of nephrotic syndrome helped elucidate some mechanisms of podocyte injury and disease progression in FSGS. This article reviews some of the experimental and clinical data on the pathophysiology of FSGS. KR is a Pediatric Nephrology Trainee supported by grant no. NIH T32 DK007110 30. FJK is supported in part by NIH DK63549-04.     

Treatment of focal segmental glomerulosclerosis

The prognosis of untreated patients with focal segmental glomerulosclerosis is poor, as the disease progress to end-stage renal disease in approximately 50--70% of nephrotic patients. Although focal segmental glomerulosclerosis was initially considered to be a steroid-resistant disease, several studies have shown a better responsiveness to more prolonged courses of steroids. For patients with steroid-resistant or -dependent focal segmental glomerulosclerosis, cyclosporine A and cytotoxic agents have shown efficacy in clinical trials. Plasmapheresis or LDL-apheresis may represent a rescue treatment in patients who do not respond to other therapies. The role of other agents used in focal segmental glomerulosclerosis, including azathioprine, mycophenolate mofetil, tacrolimus, pefloxacin or vitamin E is still poorly defined.     

Familial collapsing focal segmental glomerulosclerosis

The majority of patients with non-HIV-related collapsing focal segmental glomerular sclerosis (FSGS) have idiopathic disease. Only a few genetic forms associated with rare syndromes have been described in families. Here we report two families with multiple members who have collapsing FSGS with no clear associated secondary etiology. Genetic analysis revealed a defect in the TRPC6 gene in one family, but excluded all known common inherited podocyte defects in the other family. The course and response to treatment differed dramatically among members of the same family.     

Genetics of focal segmental glomerulosclerosis

The recent advances in understanding the pathophysiology of focal segmental glomerulosclerosis (FSGS) and molecular function of glomerular filtration barrier come directly from genetic linkage and positional cloning studies. The exact role and function of the newly discovered genes and proteins are being investigated by in vitro and in vivo mechanistic studies. Those genes and proteins interactions seem to change susceptibility to kidney disease progression. Better understanding of their exact role in the development of FSGS may influence future therapies and outcomes in this complex disease.     

Treatment of focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) has been increasing in incidence over the past 2 decades and may currently be the most common form of primary nephrotic syndrome in the United States. Nephrotic patients with FSGS who do not achieve a remission in proteinuria usually advance to end-stage renal disease within 5 to 10 years. Although initially felt to be a steroid-resistant disease, especially in adults, studies show significant responsiveness to more prolonged courses of steroids. For patients with steroid-resistant or steroid-dependent FSGS, cyclosporine A and cytotoxic agents have shown efficacy in clinical trials. Other agents used include pulse methylprednisolone, azathioprine, tacrolimus, mycophenolate mofetil, and combination therapy. For recurrent FSGS after renal transplantation, plasmapheresis is often used but appears not to be as efficacious in adults as in the pediatric population.     

Permeability factors in focal segmental glomerulosclerosis

The pathologic diagnosis of focal segmental glomerulosclerosis (FSGS) is associated with a syndrome of steroid-resistant nephrotic syndrome and progressive renal insufficiency. The incidence of FSGS has increased in recent years. Known causes of FSGS include genetic abnormalities, viral infections, decreased nephron number, and hyperperfusion/hyperfiltration. The etiology is unknown in the majority of cases. FSGS recurs after initial renal transplantation in as many as 30% to 50% of patients. Recent studies have verified the hypothesis that plasma of patients with FSGS contains a factor or factors that increase permeability of glomerular capillaries and cause proteinuria after injection into rats. Patients who experience posttransplant recurrence of FSGS and those with rapidly progressive disease exhibit this activity. Permeability activity has been verified in functional assays and defined by measurement of albumin permeability (P(alb)) or glomerular volume variation (GVV). Permeability activity is decreased by plasmapheresis or immunoadsorption and can be recovered from discarded plasma or eluate from adsorption materials. Studies from our laboratory indicate that permeability activity is carried by small, highly glycosylated, hydrophobic protein(s)/peptide(s). Normal plasma contains substances capable of blocking or inactivating the FSGS permeability factor. Pharmacologic agents including cyclosporine, indomethacin, and derivatives of Trypterigium wilfordii also block permeability activity in vitro. The observation that permeability activity can be blocked by diverse agents raises hope that specific therapy may be designed for FSGS. Future investigations will permit identification of the active FSGS permeability factor, of mechanisms that initiate and perpetuate proteinuria, and of interventions to prevent renal failure in native kidneys and recurrence of disease in renal allografts.     

Mycophenolate mofetil for primary focal segmental glomerulosclerosis: systematic review

Abstract

Background: Current treatments for primary focal segmental glomerulosclerosis (FSGS), including corticosteroids and cyclosporine, are not satisfactory for all patients and may induce significant side effects. Antidotal benefits of mycophenolate mofetil (MMF) as an add-on to these immunosuppressive therapies have been reported. This review aims to systematically summarize the efficacy and safety of MMF as a treatment for primary FSGS. Method: Controlled and uncontrolled clinical trials evaluating the use of MMF in primary FSGS patients were identified from nine electronic databases and four clinical trial registries. Kidney failure was selected as the primary outcome. Results: Three randomized controlled trials (RCT) and 18 uncontrolled pre-post studies were included. Results from RCTs revealed that MMF is no more effective than cyclosporine or cyclophosphamide for promoting kidney function preservation when corticosteroid is used as baseline treatment. One underpowered RCT reported that MMF provides no extra benefit on top of prednisolone, but the result is unlikely to be reliable. Amongst the small, uncontrolled pre-post studies, three of them used MMF as monotherapy, two of which reported successful prevention of kidney failure in all patients. The remaining 15 uncontrolled studies used MMF as add-on therapy and 11 reported kidney failure as an outcome. Amongst them, eight reported no patients developed kidney failure. MMF was generally well tolerated with mild adverse effects, including abdominal discomfort, diarrhea and infections. Conclusions: MMF tended to show beneficial effects in uncontrolled studies which recruited patients with resistance to routine treatments, but such favorable results have only been reported in small, uncontrolled trials. No RCT results suggested that MMF was a good alternative to cyclosporine or cyclophosphamide. The role of MMF as an add-on to current therapies, or as monotherapy, should further be evaluated.