Recurrence of idiopathic nephrotic syndrome after renal transplantation

Podocyte effacement closely links to suPAR levels at time of posttransplantation focal segmental glomerulosclerosis occurrence and improves with therapy

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) recurs after kidney transplantation in more than 30% of cases and can lead to allograft loss. Serum soluble urokinase-type plasminogen activator receptor (suPAR) is implicated in the pathogenesis of native and recurrent FSGS.

METHODS

We conducted a retrospective study of 25 adults with posttransplantation FSGS. We investigated the relationship between suPAR levels and podocyte changes and the impact of therapy on podocyte structure. We assessed response to therapy by improvement in proteinuria, allograft function, and resolution of histologic changes.

RESULTS

A median (interquartile range) of 15 (10-23) plasmapheresis sessions was administered; 13 of the subjects also received rituximab. Median pretreatment suPAR levels were higher among those with severe (≥75%) versus those with mild (≤25%) podocyte foot process effacement (13,030 vs. 4806 pg/mL; P=0.02). Overall, mean±SD of proteinuria improved from 5.1±3.8 to 2.1±2.8 mg/dL (P=0.003), mean podocyte effacement decreased from 57%±33% to 22%±22% (P=0.0001), estimated glomerular filtration rates increased from median (interquartile range) of 32.9 (20.6-44.2) to 39.3 (28.8-63.4; P<0.0001), and suPAR levels decreased from a median of 6.781 to 4.129 pg/mL (P=0.02) with therapy.

CONCLUSIONS

Podocyte effacement is the first pathologic manifestation of FSGS after transplantation. The degree of podocyte effacement correlates with suPAR levels at time of diagnosis. Response to therapy results in significant reduction of suPAR levels and complete or significant improvement of podocyte effacement.

Pathophysiology and treatment of focal segmental glomerulosclerosis: the role of animal models

Focal segmental glomerulosclerosis (FSGS) is a kidney disease with progressive glomerular scarring and a clinical presentation of nephrotic syndrome. FSGS is a common primary glomerular disorder that causes renal dysfunction which progresses slowly over time to end-stage renal disease. Most cases of FSGS are idiopathic Although kidney transplantation is a potentially curative treatment, 40% of patients have recurrence of FSGS after transplantation. In this review a brief summary of the pathogenesis causing FSGS in humans is given, and a variety of animal models used to study FSGS is discussed. These animal models include the reduction of renal mass by resecting 5/6 of the kidney, reduction of renal mass due to systemic diseases such as hypertension, hyperlipidemia or SLE, drug-induced FSGS using adriamycin, puromycin or streptozotocin, virus-induced FSGS, genetically-induced FSGS such as via Mpv-17 inactivation and α-actinin 4 and podocin knockouts, and a model for circulating permeability factors. In addition, an animal model that spontaneously develops FSGS is discussed. To date, there is no exact understanding of the pathogenesis of idiopathic FSGS, and there is no definite curative treatment. One requirement facilitating FSGS research is an animal model that resembles human FSGS. Most animal models induce secondary forms of FSGS in an acute manner. The ideal animal model for primary FSGS, however, should mimic the human primary form in that it develops spontaneously and has a slow chronic progression. Such models are currently not available. We conclude that there is a need for a better animal model to investigate the pathogenesis and potential treatment options of FSGS.

Podocyte foot process effacement in postreperfusion allograft biopsies correlates with early recurrence of proteinuria in focal segmental glomerulosclerosis

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) is a relatively prevalent glomerular disorder that often progresses to end-stage renal disease. Thirty to 80% of kidney transplant (KT) recipients with FSGS will experience recurrence characterized by proteinuria and podocyte damage. We hypothesized that the degree of podocyte foot process (FP) effacement in postreperfusion transplant biopsies can be used to predict the development of clinical recurrence of FSGS.

METHOD

Nineteen pairs of pre- and postreperfusion biopsy specimens were studied. We evaluated the degree of FP effacement in postreperfusion KT biopsies by counting the number of widened FP per capillary loop. Early recurrence of FSGS was defined as development of nephrotic range proteinuria between days 3 and 30 posttransplant.

RESULTS

Early recurrence occurred in 7 of 19 grafts (36.8%) at a mean of 4.29±1.89 days. The mean score of FP effacement in postreperfusion allograft biopsies was 0.72±0.31 and 1.35±0.63 in the nonrecurrent and recurrent group, respectively (P=0.039). There was an association between FP effacement and proteinuria (P = 0.04). The FP effacement score predicts early recurrence with a sensitivity of 71.4% and specificity of 91.7%.

CONCLUSION

FP effacement can be observed within minutes after reperfusion in renal transplantation of recipients with FSGS that will ultimately develop recurrent FSGS. This suggests a key role for the podocyte injury in the pathogenesis of recurrent FSGS and further supports the presence of circulating factors causing FP effacement. The FP effacement score in the postreperfusion KT biopsy may become a useful predictive test if validated in larger studies.

Recent progress in the pathophysiology and treatment of FSGS recurrence

Focal segmental glomerulosclerosis (FSGS) is a glomerular disease characterized by proteinuria, frequent progression to end-stage renal disease, and recurrence after kidney transplantation in ∼25% of patients, which negatively impacts long-term allograft survival. Experimental studies suggest that abnormalities in T and, possibly, B cells may represent one initial pathogenic trigger, leading to podocyte injury and progressive loss. New data also support the existence of circulating permeability factors able to damage the podocytes, but no single molecule has been consistently identified as the causal pathogenic element in FSGS recurrence. Unfortunately, major progress from mechanistic studies has not translated into substantial advancements in patient treatment, with plasmapheresis (PP) and high doses of cyclosporine (CsA) remaining the mainstays of therapy. Despite consistent experimental and clinical evidence that treatment of proteinuria slows renal function decline in proteinuric nephropathies, maximal use of antiproteinuric agents such as renin angiotensin system antagonists is not routine in the management of FSGS recurrence. More recently, encouraging results have been reported with anti-CD20 depleting antibody rituximab, but further studies are needed to establish its safety/efficacy profile.

TNFα pathway blockade ameliorates toxic effects of FSGS plasma on podocyte cytoskeleton and β3 integrin activation

BACKGROUND

In the absence of mutant genes encoding components of the podocyte slit diaphragm, about 30-50 % of children with primary glucocorticoid-resistant focal segmental glomerulosclerosis (FSGS) develop recurrent proteinuria and slowly progressive FSGS lesions following renal transplantation. Recurrence of FSGS in the allograft strongly suggests a circulating factor that disturbs normal podocyte biology. To date, the nature of the circulating factor is unclear, and there is no cure for the recurrent form of FSGS (R-FSGS).

METHODS

Cultured differentiated human podocytes were exposed to the plasmapheresis effluent or blood plasma samples from pediatric patients with recurrent or primary FSGS; in some cases, podocytes were pre-incubated with specific antibodies to block the tumor necrosis factor-alpha (TNFα) signaling pathway. Integrity of focal adhesion complexes and actin cytoskeleton were investigated by immunofluorescent microscopy.

RESULTS

Plasmapheresis effluent from an R-FSGS child or fresh plasma from two children with primary FSGS rapidly disturbed the cytoskeleton of normal human podocytes in vitro. Plasma from a child with R-FSGS also activated β3 integrin and dispersed focal adhesion complexes. The effects were reversed by pre-incubation with antibodies against TNFα or either of the two TNFα receptors. When our patient with R-FSGS became resistant to plasmapheresis, we initiated treatment with twice weekly etanercept injections and then infliximab. Within 3 weeks of regular anti-TNFα therapy, the patient achieved sustained partial remission of proteinuria, allowing us to wean her off plasmapheresis completely.

CONCLUSIONS

We suggest that in some FSGS patients, disruption of the podocyte cytoskeleton and β3 integrin-mediated podocyte attachment are driven by the TNFα pathway.

[Pathogenesis and treatment of idiopathic nephrotic syndrome in adults]

Idiopathic nephrotic syndrome is the most frequent glomerular disease in children and in young adults. While genetic analyses have provided new insights into disease pathogenesis through the discovery of several podocyte genes mutated in distinct forms of inherited nephrotic syndrome, the molecular bases of minimal change nephrotic syndrome and focal and segmental glomerulosclerosis with relapses remain unclear. Although immune cell disorders, which may involve both innate and adaptive immunity, appear to play a role in the pathogenesis of steroid sensitive minimal change nephrotic syndrome, the mechanisms by which they induce podocyte dysfunction remain unresolved. It was postulated that podocyte injury results from a circulating factor secreted by abnormal T cells, but the possibility that bipolarity of the disease results from a functional disorder shared by both immune cells and the podocytes is not excluded. Minimal change nephrotic syndrome relapses are associated with an expansion of T and B cell compartments and production of growth factors as well as many cytokines. Dysfunction of T cells is supported by several findings including, inhibition of a type IV hypersensitivity reaction and unclassical T helper polarization, resulting from transcriptional interference between Th1 and Th2 transcriptional factors. A low serum level of some IgG fractions is frequently observed suggesting a defect in T-B cell cooperation, which remains to be explored. In this review, we discuss recent advances in the pathogenesis and the therapy of idiopathic nephrotic syndrome.

Recurrent focal segmental glomerulosclerosis: a discrete clinical entity

Focal segmental glomerulosclerosis refers to a set of particular histopathologic lesions in which steroid-resistant podocyte injury leads to patchy adhesions between the glomerular tuft and Bowman's capsule, followed by progressive glomerulosclerosis and proteinuric renal failure. Because of the nonspecific nature of this lesion, it has been difficult to classify the various forms of primary nephrotic syndrome in children. However, with the recognition of hereditary FSGS caused by mutations podocyte slit diaphragm genes, it is increasingly clear that the steroid-resistant form of FSGS that recurs in the renal allografts (R-FSGS) constitutes a distinct clinical entity. Capitalizing on recent studies in which patients have been screened for slit diaphragm gene mutations, this review focuses on the natural history and pathogenesis of R-FSGS.

Outcome of kidney allograft in patients with adulthood-onset focal segmental glomerulosclerosis: comparison with childhood-onset FSGS

BACKGROUND

Idiopathic focal segmental glomerulosclerosis (FSGS) occurring at young age is known to predispose to poor graft outcome, but the outcome of adulthood-onset FSGS (A-FSGS) has not been thoroughly investigated. Here, we compared the graft outcomes between kidney recipients with A-FSGS and childhood-onset FSGS (C-FSGS).

METHODS

We enrolled 47 A-FSGS recipients and 60 C-FSGS recipients with an onset age of ≤ 15, from four of the largest transplant centers in Korea.

RESULTS

The baseline characteristics were similar between two groups. The 1- and 3-year cumulative recurrence rates were 20.0 and 22.1%, respectively. FSGS was recurrent in 19 C-FSGS patients [median duration, 2 months (interquartile range, IQR, 1-35)], and 11 patients had recurrent disease in A-FSGS [5 months (IQR, 3-37)]. The recurrence rate was similar between two groups (P = 0.126). The 5- and 10-year graft survival rates were 90.0 and 78.5%, respectively. The overall graft survival rates were not different between two groups. After adjusting baseline characteristics, the development of major outcomes was similar between two groups except acute rejection that was more frequent in A-FSGS. The age of disease onset did not affect recurrence in both groups. While grafts with recurrence had poorer graft survival in the A-FSGS group (P = 0.005), the recurrence was not associated with graft loss in the C-FSGS group (P = 0.558).

CONCLUSIONS

The onset age did not affect the graft outcome in patients with FSGS, and the recurrence significantly affected graft survival in A-FSGS. Therefore, the main focus should aim for the management of recurrence.

Minimal change disease: a CD80 podocytopathy?

Minimal change disease is the most common nephrotic syndrome in children. Although the etiology of minimal change disease remains to be elucidated, it has been postulated that it is the result of a circulating T-cell factor that causes podocyte cytoskeleton disorganization leading to increased glomerular capillary permeability and/or changes in glomerular basement membrane heparan sulfate glycosaminoglycans resulting in proteinuria. Minimal change disease has been associated with allergies and Hodgkin disease. Consistent with these associations, a role for interleukin-13 with minimal change disease has been proposed. Furthermore, studies evaluating podocytes also have evolved. Recently, increased expression of CD80 (also termed B7-1) on podocytes was identified as a mechanism for proteinuria. CD80 is inhibited by binding to CTLA-4, which is expressed on regulatory T cells. Recently, we showed that urinary CD80 is increased in minimal change disease patients and limited studies have suggested that it is not commonly present in the urine of patients with other glomerular diseases. Interleukin-13 or microbial products via Toll-like receptors could be factors that induce CD80 expression on podocytes. CTLA-4 appears to regulate CD80 expression in podocytes, and to be altered in minimal change disease patients. These findings lead us to suggest that proteinuria in minimal change disease is caused by persistent CD80 expression in podocytes, possibly initiated by stimulation of these cells by antigens or cytokines.

Circulating urokinase receptor as a cause of focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a cause of proteinuric kidney disease, compromising both native and transplanted kidneys. Treatment is limited because of a complex pathogenesis, including unknown serum factors. Here we report that serum soluble urokinase receptor (suPAR) is elevated in two-thirds of subjects with primary FSGS, but not in people with other glomerular diseases. We further find that a higher concentration of suPAR before transplantation underlies an increased risk for recurrence of FSGS after transplantation. Using three mouse models, we explore the effects of suPAR on kidney function and morphology. We show that circulating suPAR activates podocyte β(3) integrin in both native and grafted kidneys, causing foot process effacement, proteinuria and FSGS-like glomerulopathy. Our findings suggest that the renal disease only develops when suPAR sufficiently activates podocyte β(3) integrin. Thus, the disease can be abrogated by lowering serum suPAR concentrations through plasmapheresis, or by interfering with the suPAR-β(3) integrin interaction through antibodies and small molecules targeting either uPAR or β(3) integrin. Our study identifies serum suPAR as a circulating factor that may cause FSGS.

Circulating permeability factors in idiopathic nephrotic syndrome and focal segmental glomerulosclerosis

Circulating permeability factors may be important in idiopathic nephrotic syndrome (INS) including focal segmental glomerulosclerosis (FSGS) and in recurrence after renal transplantation. Evidence for plasma factors includes posttransplant recurrence of proteinuria and its response to plasmapheresis or immunoadsorption and induction of proteinuria in experimental animals by infusion of patient plasma or its fractions. The authors and other investigators have used proteomic techniques to seek pathogenic molecules. The authors have recently proposed cardiotrophin-like cytokine-1 (CLC-1) as an active factor in FSGS. Other potential permeability factors include hemopexin and vascular permeability factor in minimal change nephrotic syndrome (MCNS) and soluble urokinase receptor in FSGS. In the authors' studies, in vitro plasma permeability activity is blocked by diverse substances that may decrease levels of active molecules or block the effects of circulating permeability factors. It has been shown that the simple sugar galactose blocks the effect of FSGS serum on albumin permeability in vitro and decreases permeability activity when administered to patients. Because identities of permeability factors and their mechanisms of action are not well defined, therapy of INS/FSGS is empiric. Corticosteroids are the mainstay of initial therapy whereas calcineurin inhibitors such as cyclosporine A (CsA) and immunosuppressive medications provide adjunctive therapy. Nonspecific therapies such as blocking the renin-angiotensin system and controlling blood pressure and plasma lipids may also diminish proteinuria and slow progression. Identification of molecules that initiate proteinuria and application of findings from in vitro studies may lead to development of new treatments to arrest progression and prevent recurrence after transplantation.

Recurrence of focal segmental glomerulosclerosis in renal allograft: an in-depth review

Focal segmental glomerulosclerosis is a major cause of chronic kidney disease requiring transplantation in children. Recurrence rate in the renal allograft transplantation is as high as 50%. Recurrence of FSGS is associated with renal dysfunction and early graft loss. To date, there is no established therapy for recurrent FSGS after renal transplant. We have reviewed the current English literature in order to summarize current practices with emphasis on graft outcome. We conclude that despite multiple approaches to the post transplant management of recurrent FSGS, none have been shown to be consistently beneficial. Currently, pheresis combined with high dose anti-calcineurin with or without rituximab seems to be the most promising. Further controlled studies are needed to define the optimal therapeutic regimens to treat recurrent of FSGS.

Potential role of soluble ST2 protein in idiopathic nephrotic syndrome recurrence following kidney transplantation

BACKGROUND

Corticosteroid-resistant idiopathic nephrotic syndrome (INS) recurs rapidly after transplantation in 30% to 50% of transplant recipients, suggesting the presence of 1 or more circulating factors that alter the glomerular filtration barrier. We investigated the possible role in INS recurrence of soluble ST2 (sST2) protein, a marker of T helper type 2 (T(H)2) cells and a factor predicted to be regulated by the transcription factor c-Maf; involvement of sST2 protein would be consistent with the observation that both T(H)2 cells and c-Maf appear to be activated during INS relapse.

STUDY DESIGN

Retrospective observational study.

SETTING & PARTICIPANTS

Patients with biopsy-proven corticosteroid-resistant INS who had undergone kidney transplantation between September 1983 and April 2007 (n = 71). A control group consisting of proteinuric transplant recipients with kidney failure unrelated to INS (n = 34).

PREDICTOR

Patients who developed INS recurrence after transplantation (n = 31) were compared with those in whom INS did not recur (n = 40) and the control group. Recurrence of INS was defined as urine protein excretion greater than 2 g/d immediately after transplantation that persisted at greater than 1 g/d despite treatment or a kidney graft biopsy showing minimal change glomerulonephritis or focal segmental glomerulosclerosis.

OUTCOMES & MEASUREMENTS

Urine protein excretion in the 3 groups was 5.0 g/d (range, 1.3 to 10.5), 0.14 g/d (range, 0 to 0.46), and 4.3 g/d (range, 3 to 6.2). The sST2 protein was analyzed both quantitatively and qualitatively in patient sera, and its activity was tested in vitro on a mouse podocyte cell line and in vivo in rats.

RESULTS

sST2 protein levels were significantly increased after transplantation in patients with INS recurrence compared with the 2 other groups (617.5 versus 23 pg/mL; P < 0.001 and 158.5 pg/mL; P < 0.01 respectively). However, patients with recurrence expressed a normal sST2 isoform, and the sST2 protein was unable to induce podocyte injury in vitro or trigger proteinuria in rats.

LIMITATIONS

Pretransplantation and posttransplantation sera do not always represent paired samples.

CONCLUSIONS

These data suggest that sST2 protein is a marker of INS recurrence that does not seem to be involved in the development of INS.

New insights into the pathophysiology of idiopathic nephrotic syndrome

Corticoresistant idiopathic nephrotic syndrome (INS) is a glomerulopathy of unknown etiology whose original aspect is its recurrence after kidney transplantation in 30 to 50% of patients with end-stage renal disease. This suggests the involvement of circulating factors that would alter the glomerular filtration barrier, but whose nature remains elusive. Although a T cell immune origin has been suggested, the actual role of these cells in INS recurrence is still unclear. Here we present an 8-year-old patient with corticoresistant INS who developed a recurrence of her initial disease after kidney transplantation. Rituximab therapy was proposed 11 months after transplantation; although no immediate effect was induced, a slow but persistent decrease in proteinuria began a few months after Rituximab infusions despite cessation of plasma exchanges and steroid therapy. The pathophysiology of INS and the putative mechanisms of action of Rituximab are discussed.

Clinical features and mutational survey of NPHS2 (podocin) in Japanese children with focal segmental glomerulosclerosis who underwent renal transplantation

Recurrent FSGS is a major challenge in the field of nephrology. To clarify the role of NPHS2 defects in the pathogenesis of FSGS recurrence, we sequenced all eight exons of NPHS2 in 11 Japanese pediatric FSGS patients with or without post-transplant recurrence. All patients had biopsy-proven primary FSGS, had no family history of renal diseases or consanguinity, were steroid-resistant, and received living-related renal transplantation. The mean age at onset was 5.0 +/- 3.1 yr and mean age at renal transplantation was 10.4 +/- 4.1 yr. Mutational analysis of NPHS2 was performed using polymerase chain reaction and direct sequencing. We found a synonymous T/C polymorphism at alanine 318 (GCC to GCT) in seven of 11 patients but no other causative NPHS2 mutations. FSGS recurred immediately after transplant in seven patients, while the remaining four patients had no recurrence for 3.2-5.8 yr. There were no differences between recurrent and non-recurrent patients in the onset age and the interval from onset to ESRD. In conclusion, we detected no causative NPHS2 mutations in Japanese pediatric FSGS patients with or without post-transplant recurrence. Further studies on the involvement of other genes are required to better understand recurrent FSGS.

Recurrence of nephrotic syndrome/focal segmental glomerulosclerosis following renal transplantation in children

The incidence of recurrence of nephrotic syndrome/focal segmental glomerulosclerosis (NS/FSGS) is variable (~30%). The incidence of recurrence is less in African-Americans than in whites and Hispanics. Graft survival rates are decreased in recipients with FSGS, especially if remission of the NS is not achieved in those with recurrence. Although controversial, the use of living donor (LD) transplants are not contraindicated; however, obligatory heterozygote parental grafts with a podocin mutation should be used with caution. Optimal treatment to induce a remission post-transplant has not been delineated. Pre-transplant and/or prophylactic post-transplant pre-operative plasmapheresis (PP) for high-risk patients--especially those with recurrence in a previous graft--may be promising. An international multicenter controlled study is required to delineate the optimal approach to prevent and/or treat the recurrence of NS/FSGS.

Focal Segmental Glomerulosclerosis and Renal Transplantation

Primary focal segmental glomerulosclerosis (FSGS) is a major cause of nephrotic syndrome and eventual end-stage renal disease. It is known to be due to an abnormality of the visceral epithelial cells (podocytes) of the glomerulus. The morphological hallmark of primary FSGS is diffuse effacement of podocyte foot processes. The etiology of the podocyte damage is not been clearly established. FSGS can also be a secondary process due to underlying conditions including obesity and heroin use. In the secondary processes, the mechanism appears to be a decreased ratio of podocytes to the glomerular filtration surface area. Familial forms of FSGS also exist due to alterations of several different podocyte proteins. Primary FSGS is an increasing cause of end-stage renal disease. Recurrence of severe FSGS in renal allograft recipients presents a major challenge to transplant physicians. The incidence of recurrence is generally accepted to be between 20% and 30%. Risk factors for and characteristics of recurrence include a rapid progression of the primary disease to end-stage renal failure, early onset of nephrotic range proteinuria after allografting, frequent loss of the allograft, a high frequency of recurrence in subsequent allografts, and children less than 15 years of age. Some investigators have identified a circulating factor called the FSGS factor that appears to be associated with recurrence after transplantation. This factor has been shown to be a protein between 30 and 50 kd molecular weight. Logically, the possibility of a circulating factor associated with recurrence of FSGS led investigators to treat patients with plasmapheresis. Several studies have been reported with varying success. The response of patients to plasmapheresis seems to be completely individual. Other studies have added cyclophosphamide and/or mycophenolate mofetil to the plasmapheresis protocol. Again success in these studies has been variable. However, because some patients show complete recovery with plasmapheresis, individuals who develop recurrent FSGS after transplantation usually are given a trial of plasmapheresis therapy.

Long-Term Outcome of Renal Transplantation in Focal Glomerulosclerosis

INTRODUCTION

Focal segmental glomerulosclerosis (FSGS) has a tendency to recur frequently after kidney transplantation. We evaluated 12 cases to examine the incidence and long-term outcomes of recurrent FSGS.

MATERIALS AND METHODS

Twelve patients with renal failure caused by FSGS received kidney allografts from living related donors. Tacrolimus or cyclosporine was used in combination with prednisolone and azathioprine or mycophenolate mofetil.

RESULTS

The mean graft survival was 87.4 +/- 46.8 months. The graft survival rates in FSGS recipients were at 1 year, 100%; 5 years, 79.6%; 10 years, 68.2%. Two out of four recipients experienced graft loss due to chronic rejection. The other two out of four recipients with graft loss displayed severe proteinuria diagnosed as recurrence of FSGS. To treat recurrent FSGS, plasma exchange was partially effective to reduce proteinuria.

CONCLUSION

Our incidence of recurrent FSGS is 16.7% with graft survivals at 5 and 10 years of 79.6% and 68.2%, respectively. The recurrence of FSGS happened after scheduled reductions in immunosuppressants. Careful observation is required with maintenance of immunosuppression in these patients.

Plasmapheresis for Recurrent Posttransplant Focal Segmental Glomerulosclerosis

The high recurrence rate of focal segmental glomerulosclerosis (FSGS) in kidney transplant recipients suggests that such patients have a circulating factor that alters glomerular capillary permeability. Serum from patients with FSGS increases glomerular permeability to albumin. This permeability factor has been partially identified as a protein. The removal of this protein by plasmapheresis (PP) decreases proteinuria. In this study we report data on the therapeutic effects of PP in FSGS children with recurrence in the transplanted kidney. Three hundred pediatric (age <19 years) renal transplants were performed, including 21 patients (24 transplants) with FSGS as a cause of renal failure. Fourteen (58.3%) subjects experienced disease recurrence (proteinuria >1 g/m(2) per day) within 1 month after transplantation. Mean age patient was 12 +/- 4.3 years, including 83.3% Caucasians and 70.2% recipients of living donor grafts. Nine were treated with 10 cycles of PP (3 cycles/weekly), initiated immediately after recurrence (<48 hours). Immunosuppression included high doses of cyclosporine (C(2) levels of 1700-1800 ng/mL), mycophenolate sodium or mofetil, and prednisone. Thirteen patients were induced with anti-IL2 receptor monoclonal antibody (daclizumab/basiliximab). Among the patients who underwent PP, five (55.5%) achieved a complete remission and one (12%), a partial remission (1 g/24 hours). There were no cases of remission among the five patients who were not treated with PP. Those who achieved remission after PP experienced no recurrences during the 2.6 +/- 1.4 years follow-up. PP appears to be effective to treat recurrent FSGS following kidney transplantation. It should be started as soon as possible.

Peritoneal protein losses in children with steroid-resistant nephrotic syndrome on continuous-cycler peritoneal dialysis

Glomerular protein permeability rises in nephrotic syndrome and may result from the effect of an unidentified "circulating factor." The effect of this "circulating factor" on the permeability of other body membranes is unknown. In this study we examine the peritoneal membrane protein permeability in patients with nephrotic syndrome on chronic-cycler peritoneal dialysis. We conducted a retrospective study of peritoneal protein losses in the dialysate effluent of 60 pediatric peritoneal dialysis patients (ages 5.1-22 years) over a 6-year period (January 1997-December 2002). Nineteen patients had steroid-resistant nephrotic syndrome (SRNS), while 41 had other non-nephrotic etiologies of renal failure. Total and normalized peritoneal protein losses are higher in SRNS than in non-nephrotic patients (12,603+/-5,403 mg/day vs 4,475+/-469 mg/day, P<0.05; 297.8+/-79.3 mg/kg per day vs 156.8+/-16.0 mg/kg per day, P<0.05; 9,614.6+/-3,253.4 mg/m(2) per day vs 4,168.3+/-367.3 mg/m(2) per day, P<0.05). The ratio of total protein in dialysate to plasma, a measure of peritoneal membrane protein permeability, was higher in SRNS patients (3.50+/-1.00% vs 0.68+/-0.06%, P<0.001). Serum albumin concentration was lower in SRNS patients (3.09+/-0.13 mg/dl vs 3.52+/-0.07 mg/dl, P<0.01). There were no differences between the two groups with regard to duration of peritoneal dialysis, dialysis prescription, numbers of peritonitis episodes, catheter replacements, or hospitalizations. In summary, these results demonstrate that peritoneal protein losses in patients with SRNS are twice as great as in those without nephrotic syndrome. These results are consistent with the systemic effect of a "circulating factor" in SRNS and underscore the importance of adequate protein intake in patients on peritoneal dialysis.

Recurrence of focal-segmental glomerulosclerosis in children after renal transplantation: clinical and genetic aspects

Focal segmental glomerulosclerosis (FSGS) is the primary renal disease in approximately one-tenth of pediatric patients receiving a renal allograft. Recurrence of proteinuria after renal transplantation is observed in approximately 30% of patients and negatively impacts graft survival. Risk factors for recurrence are a chronological age <15 years at onset of the nephrotic syndrome and a rapid progression of the disease in the native kidneys leading to end-stage renal disease in less than 3 years. Mesangial proliferation in the native kidneys is also an important negative predictive factor for disease recurrence. With rapid recurrence of FSGS and loss of the allograft, further renal transplants also carry a high likelihood of FSGS recurrence. Different pathogenic factors have been discussed for the recurrence of proteinuria/FSGS in the transplanted kidney, especially the involvement of a proteinuric circulating factor, whose production seems to follow T-cell dysfunction. In the last decade, mutations in genes encoding podocyte proteins have been identified in different forms of hereditary FSGS. Mutations of NPHS2 were detected in 26-38% of familial autosomal recessive steroid-resistant NS (SRNS), 6-19% of sporadic cases of SRNS, and in few adult patients with FSGS. Large multicenter studies demonstrated that patients with two pathogenic NPHS2 mutations have a very low risk of recurring FSGS after renal transplantation, whereas patients with only one mutation presumably have a risk comparable to non-NPHS2 FSGS patients. The management of FSGS following renal transplantation remains controversial. Following the assumption of a putative permeability factor, several studies have suggested the efficacy of plasmapheresis in inducing remission, preferably in conjunction with high-dose cyclosporine A or cyclophosphamide. Prospective studies will be necessary to better evaluate different therapeutic approaches.

Risk factors and outcome of focal and segmental glomerulosclerosis recurrence in adult renal transplant recipients

BACKGROUND

Recurrence of nephrotic syndrome (NS) after renal transplantation for primary focal segmental glomerulosclerosis (FSGS) is a frequent and still unpredictable complication. However, risk factors for recurrence have not yet been clearly identified.

METHODS

Data from 33 patients who underwent 35 renal transplantations for FSGS in two French centres are reported.

RESULTS

Recurrent NS occurred in 12 transplant recipients (34%). A significantly higher number of patients in the group with recurrence (R group) compared with the group without recurrence (NR group) received cyclosporine for FSGS treatment before transplantation (83.3% vs 43.4%, P<0.02). Donors of R group recipients were significantly older than those of the non-NR group recipients (42.8 years vs 35 years, P<0.05). A higher number of patients from the R group required post-transplantation dialysis (33.3% vs 17.4%, P = 0.002). Surprisingly, acute rejection occurred more frequently in patients of the NR group compared with the R group, although the difference was not significant. Among the 12 patients with NS relapse, 9 were treated with plasmapheresis. Graft loss related to recurrence occurred in 6 cases. The 5-year graft survival was significantly lower in patients with recurrent NS compared with patients without recurrence (57% vs 82%, P<0.001).

CONCLUSION

This study confirms the benefit to identify in the future clinical or biological predictive risk factors for NS recurrence after renal transplantation. It also indicates that donor age is a reliable risk factor for recurrence in adult recipients and suggests for the first time a possible opposite relationship between recurrent FSGS and acute rejection.

Recurrence of nephrotic syndrome after renal transplantation: influence of increased immunosuppression

Recurrence of nephrotic syndrome after renal transplantation leads to graft loss within 1 year in 50-80% of patients who do not receive any specific treatment. Several treatment protocols have been proposed leading to long-term remission in 50-80% of patients. The aim of our study was to evaluate the efficiency of intensified immunosuppression, simultaneously including methylprednisolone pulses, cyclophosphamide, high-dose cyclosporine and plasma exchanges. Fourteen patients with early recurrence were treated with a protracted high-dose prednisone or IV methylprednisolone, oral cyclophosphamide, high-dose oral or IV cyclosporine, and plasma exchanges. By the end of cyclophosphamide therapy and plasma-exchange program, six out of 14 patients had no proteinuria; five had residual proteinuria without nephrotic syndrome and three experienced ongoing gross proteinuria with nephrotic syndrome. By the end of follow-up, four out of the 14 patients had lost their graft: one out of six with complete remission, one out of five with residual proteinuria and two out of three with persistent nephrotic syndrome. We conclude that multiple reinforcement of immunosuppression in patients with recurrent nephrotic syndrome following renal transplantation as performed in our patients is not more efficient than the single use of cyclophosphamide or plasma exchange or high-dose cyclosporine as reported in the literature.

Plasmapheresis for the prophylaxis and treatment of recurrent focal segmental glomerulosclerosis following renal transplant

We evaluated 10 patients with primary focal segmental glomerulosclerosis (FSGS) treated with plasmapheresis (PS) following renal transplantation. Three patients lost their first graft due to FSGS recurrence. In seven patients, PS was indicated as treatment for probable recurrence defined as the onset of proteinuria above 1 g/24 hours. In the remaining three patients, treatment was started in the first week posttransplant as prophylaxis against recurrence. The PS protocol was 17 sessions with the exchange of 2.5 L of plasma for 5% albumin over 10 to 12 weeks. Losartan (25 to 100 mg/d) was given to most patients at the end of PS treatment. The mean follow-up time after PS was 10 months. All patients currently have a functioning graft. A full response to treatment, defined as persistently reduced proteinuria to less than 500 mg/24 hours or the lack of recurrence in prophylactic treatment, was achieved in six patients. Three patients showed a partial decrease in proteinuria (to less than 1 g/24 hours). One patient failed to respond and still has nephrotic range proteinuria. No adverse effects of PS were recorded. A prompt start of PS combined with the use of losartan yields good results in the prophylaxis and treatment of recurrent FSGS following renal transplant in terms of quickly reduced proteinuria. Given the natural course of FSGS, a longer follow-up is needed to estimate the impact of PS on graft survival.

New insights into the pathogenesis and the therapy of recurrent focal glomerulosclerosis

Recurrent focal glomerulosclerosis (FSGS) in renal allografts has remained a frustrating and enigmatic disease. Recent studies on gene mutations encoding podocin and other components of the slit-diaphragm in patients with native kidney nephrotic syndrome have underscored the heterogenecity of the idiopathic form of FSGS. While familial FSGS rarely recurs following transplantation, the sporadic variety of FSGS is associated with a 30% recurrence rate. The patients with the sporadic variety of FSGS who have homozygous or complex heterozygous podocin mutations have a low recurrence rate. In the other patients with sporadic FSGS, a more complex and likely multifactorial etiology accounts for the recurrence of FSGS. The role of CD80 expression on podocytes is intriguing but requires confirmation in kidney biopsies of patients with recurrent FSGS. Recent findings on podocin genomics, the permeability factor and CD80 expression may ultimately lead to a better understanding of recurrent FSGS as well as a more effective approach to its prevention and treatment.

Recurrence of focal glomerulosclerosis in post-renal transplant recipients: report of two cases

INTRODUCTION

Focal segmental glomerulosclerosis (FGS) has a tendency to recur frequently after kidney transplantation. To evaluate the incidence and outcome of recurrence of FGS, we report 2 cases of recurrence.

PATIENTS

Among 12 patients with renal failure caused by biopsy-proved FGS who received kidney allografts from living related donors, 2 experienced recurrent FGS.

CASE REPORTS

Case 1 was a 28-year-old man who received a renal transplant from his mother. The recurrence of FGS happened just after the scheduled reduction in immunosuppressants at 36 months after the transplantation. He developed subsequently end-stage renal failure (ESRD) 50 months after transplantation. Case 2 was a 22-year-old man who received a renal transplant from this ABO disparate mother. A few days after renal transplantation, he displayed a severe nephrotic syndrome due to recurrent FGS, reaching ESRD at 23 months. To treat recurrent FGS, plasma exchange was partially effective, reducing the proteinuria but not stopping the progression of disease.

DISCUSSION

Two recipients with severe proteinuria were diagnosed as having recurrent FGS. The incidence of recurrent FGS was 16.7% with 5-year and 10-year graft survival rates among recipients with ESRD caused by FGS of 79.6% and 68.2%, respectively. The incidence and graft survival rates were better than those expected based upon previous reports. Once the recurrence occurred, it was difficult to halt the progression of disease. Effective prevention of FGS and careful observations with maintained of immunosuppression are necessary in these patients.

Evolution of nephrotic-associated focal segmental glomerulosclerosis and relation to the glomerular tip lesio11See Editorial by Haas,P. 1188

BACKGROUND

Several entities or variants within focal segmental glomerulosclerosis (FSGS) have been described, but their changes with time and interrelationships are undetermined.

METHODS

Changes with time were studied in two series of segmental sclerosing lesions in the nephrotic syndrome, one of 22 specimens from ten patients in a trial, the other of 176 specimens from 121 consecutive patients.

RESULTS

The earliest lesions were probably all at the tubular origin, equivalent to the tip variant of FSGS. In some patients, lesions remained at this site, but progression to renal failure was accompanied by morphologic progression, with development of lesions at various sites, equivalent to FSGS, not otherwise specified (NOS). Progression was more likely if there were large lesions, abnormal mesangium, and extensive acute tubular damage. Patients with lesions at the tubular origin at presentation had a shorter duration of symptoms and less chronic renal damage than those with multiple lesions, were more likely to have a complete response of the nephrotic syndrome, and were less likely to progress to renal failure. Recurrent nephrotic syndrome occurred in 12 of 14 allografts at risk, and was usually accompanied by lesions at the tubular origin, then multiple lesions.

CONCLUSION

At least some patients with FSGS (NOS) have evolved from the tip variant. The tip variant has been considered a distinct entity. Another interpretation is that it includes two conditions, one an early form of classic FSGS, and the other closely related to minimal change nephropathy (MCN), equivalent to the glomerular tip lesion as originally defined.

Effect of Post-transplant Double Filtration Plasmapheresis on Recurrent Focal and Segmental Glomerulosclerosis in Renal Transplant Recipients

In the present study, we reviewed the effect of post-transplant double filtration plasmapheresis (DFPP) on recurrent focal segmental glomerulosclerosis (FSGS) in the transplanted kidney allograft. Sixteen patients with post-transplant recurrent FSGS were enrolled in this study. Out of 16 patients with recurrent FSGS after transplantation, five did not receive DFPP and lost their grafts, while 11 did receive DFPP and four of these patients lost their grafts. Seven patients were able to maintain normal renal function for an average observation period of 57.1 +/- 40.7 months (range 7-125 months). In five patients who had a significant reduction in urinary protein after DFPP, the urinary protein level decreased from 26.60 +/- 23.05 g/day (range 3.34-62.6 g/day) to 2.95 +/- 3.42 g/day (range 0.02-8.64 g/day) and renal function was maintained. The beneficial effects of DFPP on graft outcome were more likely to occur if the patients experienced a marked drop in urinary excretion. Thus, post-transplant DFPP appears to be effective for reducing urinary protein levels and improving long-term graft survival. With the small numbers in this trial, however, none of the findings were statistically significant. We recommend the use of post-transplant DFPP to prevent the progression of recurrent FSGS.

Outcomes after renal transplantation for FSGS in children

Focal segmental glomerulosclerosis (FSGS) is the primary diagnosis resulting in end-stage renal disease in approximately 12% of children receiving renal transplantation. Recurrent FSGS after transplantation is unpredictable and clear risk factors have not been identified. Post-transplantation, the incidence of acute tubular necrosis requiring dialysis is higher in children with FSGS compared with other diagnoses and may represent immediate severe recurrence. Graft survival is decreased in children with FSGS compared with other primary diagnoses, and the impact is greatest in recipients of living donor transplants. Graft loss caused by recurrent FSGS is significantly higher in living donor transplants compared with cadaveric donor transplants in children. Compared with adults, the impact of FSGS on graft survival appears to be greatest in children. White recipient race is associated with a higher risk of graft loss from recurrent FSGS. Efforts to elucidate the mechanisms of recurrent FSGS and to understand risk factors based on genetics, potential circulating cytokines and permeability factors, age and race must move forward before we can significantly impact outcomes in renal transplantation for FSGS.

Role of the immune system in the pathogenesis of idiopathic nephrotic syndrome

Idiopathic NS (nephrotic syndrome) is characterized by massive proteinuria, due to a leak in the glomerular barrier to proteins. Genetic defects that affect the function and the composition of the glomerular capillary wall, in particular of the visceral epithelial cells, have recently been recognized as the cause of familial forms of NS. MCNS (minimal change NS) and FSGS (focal and segmental glomerulosclerosis) are common non-familial forms of NS in which the causative defect has not yet been identified. Several studies have shown that non-familial NS is associated with the presence of circulating permeability factors and with complex disturbances in the immune system. Thus far, there is no direct evidence that these factors directly alter glomerular permeability to proteins, and some of these factors may be a consequence, rather than a cause, of NS. In this review, we will briefly highlight the mechanisms that underlie proteinuria in general and focus on the immunological disturbances associated with idiopathic NS, with attention to potential mechanisms whereby the immune system may directly act on the glomerular capillary filter.

Recurrence of primary disease in children after renal transplantation: an evidence-based update

The availability of new and more effective anti-rejection therapy has succeeded in reducing the incidence of acute cellular rejection in first months post-renal transplant. This in turn has escalated the order of significance of recurrence of primary disease in the renal allograft as a cause for patient morbidity and graft loss during this period. The aim of this review is to survey current literature, identify issues and potential areas for future research related to recurrence of primary disease after renal transplant. Our review of published reports suggests that our current knowledge and practice, related to the management of recurrence of primary disease, are mainly based on non-randomized and uncontrolled case series. The future need for well designed mechanistic as well as therapeutic, controlled and randomized multicenter clinical trials cannot be overemphasized.

Therapeutic plasma exchange in recurrent focal segmental glomerulosclerosis following transplantation

Focal segmental glomerulosclerosis (FSGS) recurs in 30% of renal allograft transplants with graft loss in half of the cases. A humoral factor may be implicated. We report on the use of therapeutic plasma exchange (TPE) in 11 patients with recurrent FSGS post transplantation. Medical records from 1989-2000 were reviewed for 11 adults transplanted for biopsy proven FSGS. Ten patients developed proteinuria (x: 6.1 g; range: 3-40 g/24 h) within 2 months of transplantation. In 1 patient, proteinuria (4 g) occurred 2 years post transplantation. Biopsy in six patients revealed early recurrent FSGS, while in five, suspected recurrence was based on clinical findings. Each patient received 5-11 TPEs (x: 6) with the COBE Spectra, daily or on alternate days with 2.5-3.5 L 5% albumin as the replacement fluid. In four, FFP was included because of coagulopathy. All received immunosuppression (IS) during and after TPE. A persistent drop in 24 h urine protein (U.P.) was observed in 10/11 patients. Seven had >70% drop in 24 h U.P. following the course of TPE, while three had a reduction of 45-50%. No change occurred in 1 patient. Follow-up (9 months-5 years) of seven patients has shown a persistent U.P. of <1 g with successful allograft survival. In these patients, TPE appeared effective in early recurrent FSGS. The decrease in U.P. may result from combined TPE and IS. Although the disease is designated in category III by the ASFA, TPE should be considered early when FSGS recurrence is established.

Nephrotic urine prevents increased rat glomerular albumin permeability induced by serum from the same patient with idiopathic nephrotic syndrome

BACKGROUND

The putative humoral mediator thought to be involved in the pathogenesis of idiopathic nephrotic syndrome has not yet been identified. However, components exist in normal serum that block the permeability activity of FSGS serum in vitro. The potential of FSGS serum to increase glomerular albumin permeability may result from an imbalance between permeability factors and naturally occurring inhibitors. We hypothesized that this imbalance may be favoured by loss of inhibitory factors in nephrotic urine.

METHODS

The study population consisted of seven patients with biopsy-proven FSGS, one with IgM nephropathy, and three with idiopathic nephrotic syndrome without biopsy, from whom frozen serum and dialysed and lyophilized urine samples were available. Glomerular albumin permeability (P(alb)) was determined from the change in glomerular volume induced by applying oncotic gradients across the basement membrane of normal isolated rat glomeruli pre-incubated with patient serum, normal control serum, patient serum mixed with an equal volume of urine from the same patient, or patient serum mixed with normal urine. Serum and urine apolipoproteins J and E were measured by dot-blot, utilizing peroxidase-labelled antibodies. The urinary capacity to scavenge oxygen radicals was determined after exposure of isolated glomeruli to superoxide generated by xanthine and xanthine oxidase.

RESULTS

The mean P(alb) of the patients was markedly elevated at 0.74+/-0.08. The addition of urine from the same patient significantly reduced P(alb) (mean 0.15+/-0.23) in all but one of the patients with FSGS. Normal urine had no inhibitory effect in the 10 patients in which it was tested (mean 0.71+/-0.09). Serum apo J was slightly decreased and serum apo E was slightly increased compared with controls. Urine levels of both lipoproteins were significantly decreased compared with controls. Urine from FSGS patients effectively neutralized superoxide, whereas normal urine did not.

CONCLUSIONS

Nephrotic urine but not normal urine contains components that block increased albumin permeability in isolated rat glomeruli induced by serum from patients with the idiopathic nephrotic syndrome. The inhibitory function of these components, which appear not to include apolipoproteins J and E, may involve scavenging of superoxide as a final common pathway. Loss in the urine from the serum of naturally occurring inhibitors in the initial stages of the disease may propagate proteinuria and glomerular injury.

De novo minimal change disease associated with reversible post-transplant nephrotic syndrome. A report of five cases and review of literature

Nephrotic syndrome (NS) is frequent in renal transplant recipients and may be related to a large variety of glomerular lesions. In some of these cases, the transplant biopsy showed no significant glomerular changes and the NS was reversible, but the primary renal disease was not minimal change disease (MCD), suggesting that MCD may develop de novo in renal transplant setting. Knowledge of this entity, however, is limited. Among 67 cases of post-transplant NS encountered in a 12-yr period, five were found to be associated with de novo MCD. A critical review of the literature revealed nine additional cases of de novo MCD. The data from these 14 cases show that patients with de novo MCD had a large variety of primary renal diseases but MCD or focal segmental glomerulosclerosis was not among them. Eight of the 14 transplanted kidneys (60%) were from living related donors, suggesting this as a risk factor. Nephrotic range proteinuria (3-76 g/d) developed immediately or shortly after transplantation (within 4 months for all reported cases, except for one at 24 months). The serum creatinine when NS was first diagnosed was normal or mildly elevated, but acute renal failure occurred in three patients. On biopsy, the glomeruli were normal or, more frequently, displayed mild, focal segmental mesangial sclerosis, hypercellularity, deposition of IgM/C3, or accumulation of mononuclear inflammatory cells in some glomerular capillaries. The tubulointerstitial compartment was normal in cases with normal renal function; displayed mild acute and/or chronic rejection that correlated with a mildly elevated serum creatinine; or showed acute changes including acute rejection, acute tubular necrosis, or acute cyclosporin A toxicity, which accounted for both acute renal failure at presentation and its subsequent reversibility. Under various treatments, including increased steroids, angiotensin converting enzyme inhibitors, calcium channel blockers and angiotensin receptor blockers, sustained remission of NS was achieved in 13 cases, within a year (0.5-12 months) in 10 and later (24, 34 and 98 months, respectively) in three. In the remaining case, the patient died of septic shock 2 months after transplantation. After remission of the NS, the grafts functioned well without or with minimal proteinuria for several years. De novo MCD has characteristic clinical and pathologic features. It represents an important but hitherto underemphasized cause of post-transplant NS, which is potentially reversible and does not adversely affect the renal transplants.

Proteinuria after injection of human focal segmental glomerulosclerosis factor

BACKGROUND

Recurrent focal segmental glomerulosclerosis (FSGS) is heralded by proteinuria that may remit after treatment with plasmapheresis or immunoadsorption. Study of recurrent FSGS has been hampered by lack of an animal model that exhibits a pattern of proteinuria that mimics human disease. We have obtained a component of FSGS patient plasma (FSGS factor) that increases glomerular albumin permeability (P(alb)) in vitro and causes transient proteinuria in vivo.

METHODS

Plasma fractions containing FSGS factor and comparable plasma fractions from normal donors were injected into normal male Sprague-Dawley rats. Urinary protein, albumin, and creatinine were measured at various time points. Additionally, plasma samples from test animals were collected after injection and tested for FS activity defined by increased P(alb). Finally, glomeruli were isolated from animals after injection and P(alb) of these glomeruli tested.

RESULTS

Proteinuria and albuminuria were increased by 24 hr after injection with FSGS factor, and returned to baseline by 48 hr after injection. Injection with the same fraction of normal plasma had no effect on urinary protein. FSGS factor increased urinary protein in a dose-dependent manner. Serum collected from rats 15 or 60 min after injection with FSGS factor increased P(alb) of glomeruli in vitro, whereas serum collected 3 or more hours after injection had no effect. Glomeruli isolated from rats receiving injections with FSGS factor had increased in vitro P(alb) compared with glomeruli from rats injected with a fraction from normal plasma.

CONCLUSIONS

We have demonstrated that a single injection of FSGS factor increases P(alb) and, causes transient albuminuria and proteinuria in rats. FS activity in the plasma of recipient rats is also transient. This is the first detailed description of the time course and dose-dependence of proteinuria caused by FSGS factor in an animal model.