Junichiro Sageshima

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 β3 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 β3 integrin. Thus, the disease can be abrogated by lowering serum suPAR concentrations through plasmapheresis, or by interfering with the suPAR–β3 integrin interaction through antibodies and small molecules targeting either uPAR or β3 integrin. Our study identifies serum suPAR as a circulating factor that may cause FSGS.

Rituximab Targets Podocytes in Recurrent Focal Segmental Glomerulosclerosis

Rituximab treatment in high-risk patients with focal segmental glomerulosclerosis directly affects podocyte function and is linked to reduced incidence of recurrent proteinuria after kidney transplantation. Rituximab Prods Podocytes to Action Rituximab is a monoclonal antibody against CD20, a protein located on the surface of B cells. It is typically used to treat certain cancers and autoimmune disorders, but has also treated kidney conditions, including focal segmental glomerulosclerosis (FSGS)—a disorder that can affect both pediatric and adult patients. Recurrent FSGS is a problem for 30 to 40% of patients who have undergone kidney transplantation, and can be characterized by progression to end-stage renal disease and recurrence of proteinuria after transplant. Despite the ability of rituximab to treat FSGS, it has been unclear exactly how this drug achieves success in some patients, but not others. Fornoni and colleagues hypothesized that rituximab operates in a B cell–independent manner, targeting instead specific kidney cells called podocytes. To test this hypothesis, Fornoni et al. studied 41 patients at high risk for FSGS: 14 historical control patients who were not treated with rituximab and 27 patients who received rituximab at the time of kidney transplant. They found fewer podocytes with sphingomyelin phosphodiesterase acid-like 3b (SMPDL-3b) protein in biopsies from patients who later developed recurrent FSGS. The authors had also collected serum from all patients before transplant and then later treated normal human podocytes in culture with the sera. Serum from patients who would later develop recurrent FSGS caused a decrease in both SMPDL-3b protein and acid sphingomyelinase activity. This phenomenon was prevented by rituximab. The FSGS serum from patients also disrupted the actin cytoskeleton of cultured podocytes, but pretreatment with rituximab, or even overexpression of SMPDL-3b protein, partially prevented this phenotype. Together, these data suggest that modulation of sphingolipid-related proteins plays a role in the pathogenesis of recurrent FSGS and, moreover, that these proteins and enzymes might be targets of rituximab treatment. With the mechanism solved, rituximab may represent a new therapeutic strategy to prevent recurrent proteinuria after kidney transplantation. Here’s to happy and healthy kidneys! Focal segmental glomerulosclerosis (FSGS) is a glomerular disease characterized by proteinuria, progression to end-stage renal disease, and recurrence of proteinuria after kidney transplantation in about one-third of patients. It has been suggested that rituximab might treat recurrent FSGS through an unknown mechanism. Rituximab not only recognizes CD20 on B lymphocytes, but might also bind sphingomyelin phosphodiesterase acid-like 3b (SMPDL-3b) protein and regulate acid sphingomyelinase (ASMase) activity. We hypothesized that rituximab prevents recurrent FSGS and preserves podocyte SMPDL-3b expression. We studied 41 patients at high risk for recurrent FSGS, 27 of whom were treated with rituximab at time of kidney transplant. SMPDL-3b protein, ASMase activity, and cytoskeleton remodeling were studied in cultured normal human podocytes that had been exposed to patient sera with or without rituximab. Rituximab treatment was associated with lower incidence of posttransplant proteinuria and stabilization of glomerular filtration rate. The number of SMPDL-3b+ podocytes in postreperfusion biopsies was reduced in patients who developed recurrent FSGS. Rituximab partially prevented SMPDL-3b and ASMase down-regulation that was observed in podocytes treated with the sera of patients with recurrent FSGS. Overexpression of SMPDL-3b or treatment with rituximab was able to prevent disruption of the actin cytoskeleton and podocyte apoptosis induced by patient sera. This effect was diminished in cultured podocytes where SMPDL-3b was silenced. Our study suggests that treatment of high-risk patients with rituximab at time of kidney transplant might prevent recurrent FSGS by modulating podocyte function in an SMPDL-3b–dependent manner.

Abatacept in B7-1–Positive Proteinuric Kidney Disease

Abatacept (cytotoxic T-lymphocyte-associated antigen 4-immunoglobulin fusion protein [CTLA-4-Ig]) is a costimulatory inhibitor that targets B7-1 (CD80). The present report describes five patients who had focal segmental glomerulosclerosis (FSGS) (four with recurrent FSGS after transplantation and one with primary FSGS) and proteinuria with B7-1 immunostaining of podocytes in kidney-biopsy specimens. Abatacept induced partial or complete remissions of proteinuria in these patients, suggesting that B7-1 may be a useful biomarker for the treatment of some glomerulopathies. Our data indicate that abatacept may stabilize β1-integrin activation in podocytes and reduce proteinuria in patients with B7-1-positive glomerular disease.

Recurrence of type 1 diabetes after simultaneous pancreas-kidney transplantation, despite immunosuppression, is associated with autoantibodies and pathogenic autoreactive CD4 T-cells

OBJECTIVE To investigate if recurrent autoimmunity explained hyperglycemia and C-peptide loss in three immunosuppressed simultaneous pancreas-kidney (SPK) transplant recipients. RESEARCH DESIGN AND METHODS We monitored autoantibodies and autoreactive T-cells (using tetramers) and performed biopsy. The function of autoreactive T-cells was studied with in vitro and in vivo assays. RESULTS Autoantibodies were present pretransplant and persisted on follow-up in one patient. They appeared years after transplantation but before the development of hyperglycemia in the remaining patients. Pancreas transplant biopsies were taken within ∼1 year from hyperglycemia recurrence and revealed β-cell loss and insulitis. We studied autoreactive T-cells from the time of biopsy and repeatedly demonstrated their presence on further follow-up, together with autoantibodies. Treatment with T-cell–directed therapies (thymoglobulin and daclizumab, all patients), alone or with the addition of B-cell–directed therapy (rituximab, two patients), nonspecifically depleted T-cells and was associated with C-peptide secretion for >1 year. Autoreactive T-cells with the same autoantigen specificity and conserved T-cell receptor later reappeared with further C-peptide loss over the next 2 years. Purified autoreactive CD4 T-cells from two patients were cotransplanted with HLA-mismatched human islets into immunodeficient mice. Grafts showed β-cell loss in mice receiving autoreactive T-cells but not control T-cells. CONCLUSIONS We demonstrate the cardinal features of recurrent autoimmunity in three such patients, including the reappearance of CD4 T-cells capable of mediating β-cell destruction. Markers of autoimmunity can help diagnose this underappreciated cause of graft loss. Immune monitoring during therapy showed that autoimmunity was not resolved by the immunosuppressive agents used.

Effect of Kidney Transplantation on Outcomes among Patients with Hepatitis C

The long-term outcome of kidney transplantation in patients infected with hepatitis C virus (HCV) and end stage renal disease (ESRD) is not well described. We retrospectively identified 230 HCV-infected patients using enzyme immunoassay and nucleic acid testing obtained during the transplant evaluation. Of 207 patients who had a liver biopsy before transplant, 44 underwent 51 follow-up liver biopsies at approximately 5-year intervals either while on the waitlist for a kidney or after kidney transplantation. Advanced fibrosis was present in 10% of patients biopsied, identifying a population that may warrant consideration for combined liver-kidney transplantation. Kidney transplantation does not seem to accelerate liver injury; 77% of kidney recipients who underwent follow-up biopsies showed stable or improved liver histology. There was a higher risk for death during the first 6 months after transplant, but undergoing transplantation conferred a long-term survival advantage over remaining on the waitlist, which was evident by 6 months after transplant (HR, 0.32; 95% CI, 0.17 to 0.62). Furthermore, the risk for death resulting from infection was significantly higher during the first 6 months after transplant (HR, 26.6; 95% CI, 5.01 to 141.3), whereas there was an early (≤6 months) and sustained decrease in the risk for cardiovascular death (HR, 0.20; 95% CI, 0.08 to 0.47). In summary, these data suggest the importance of liver biopsy before transplant and show that kidney transplantation confers a long-term survival benefit among HCV-infected patients with ESRD compared with remaining on the waitlist. Nevertheless, the higher incidence of early infection-related deaths after transplant calls for further study to determine the optimal immunosuppressive protocol.

Randomized Trial of Mycophenolate Mofetil Versus Enteric-coated Mycophenolate Sodium in Primary Renal Transplant Recipients Given Tacrolimus and Daclizumab/thymoglobulin: One Year Follow-up

Background. It was of interest to compare enteric-coated mycophenolate sodium (EC-MPS) versus mycophenolate mofetil (MMF) among renal transplant recipients receiving a tacrolimus-based immunosuppressive regimen. Methods. Between December 2004 and February 2006, a single-center, open-label randomized trial of MMF (group A, n=75) versus EC-MPS (group B, n=75) was performed in primary renal transplant recipients receiving combined thymoglobulin/daclizumab induction along with reduced tacrolimus dosing and elimination of corticosteroids 1 week postoperatively. The primary endpoint was the incidence rate of acute rejection (AR) during the first 12 months posttransplant; secondary aims were to compare graft and patient survival, renal function, drug dosing and monitoring, gastrointestinal side effects, and other adverse events at 12 months of follow-up. Results. Patient/graft survival in groups A and B were 100%/96% versus 99%/96%, respectively (N.S.). At 12 months, a total of nine patients (6%) experienced biopsy-proven AR, 3% (2/75) vs. 9% (7/75) in the MMF and EC-MPS arms, respectively (N.S.). At 12 months, the geometric mean*/SE serum creatinine concentration and arithmetic mean±SE calculated glomerular filtration rate in groups A and B, respectively, were 1.30*/1.03 and 61.4±2.0 vs. 1.26*/1.03 and 66.0±2.1 (N.S.). Incidence of new onset diabetes mellitus (11% vs. 11%), infections requiring hospitalization (13% vs. 15%), and gastrointestinal side effects (36% vs. 32%) appeared equivalent (N.S.). Conclusions. Early efficacy and toxicity were equivalent between the two study arms. Optimizing either MMF or EC-MPS along with a combined thymoglobulin/daclizumab induction, low tacrolimus dosing and steroid avoidance resulted in a low AR rate and an acceptably high renal function at 12 months.

Disparities among Blacks, Hispanics, and Whites in time from starting dialysis to kidney transplant waitlisting.

Background Although a longer time on dialysis before kidney transplant waitlisting has been shown for Blacks versus non-Blacks, relatively few studies have compared this outcome between Hispanics and Whites. Methods A multivariable analysis of 1910 (684 Black, 452 Hispanic, and 774 White) consecutive patients waitlisted at our center for a primary kidney transplant between 2005 and mid-2010 was performed for time from starting dialysis to waitlisting (months), the percentage who were preemptively waitlisted (waitlisted before starting dialysis), and time from starting dialysis to waitlisting after excluding the preemptively waitlisted patients. Results The variables associated with significantly longer median times from starting dialysis to waitlisting and less preemptive waitlisting included Medicare insurance for patients ages <65 years (by far, the most significant variable in each analysis), Black race, higher percentage of households in the patient’s zip code living in poverty, being a non-U.S. citizen (for preemptive waitlisting), Medicaid insurance, waitlisted for kidney-alone (vs. kidney-pancreas) transplant, and higher body mass index (longer median times for the latter three variables). Although the effect of Black race was mostly explained by significant associations with lower socioeconomic status (Medicare insurance for patients ages <65 years and greater poverty in the patient’s zip code), an unexplained component still remained. The univariable differences showing poorer outcomes for Hispanics versus Whites were smaller and completely explained in multivariable analysis by significant associations with lower socioeconomic status and non-U.S. citizenship. Conclusion Black and Hispanic patients had significantly longer times from starting dialysis to waitlisting, in large part related to their lower socioeconomic status and less preemptive waitlisting. A greater focus on earlier nephrology care may help to erase much of these disparities.

Insulin protein and proliferation in ductal cells in the transplanted pancreas of patients with type 1 diabetes and recurrence of autoimmunity

Aim/hypothesisWe investigated whether beta cell neoformation occurs in the transplanted pancreas in patients with type 1 diabetes who had received a simultaneous pancreas–kidney transplant (SPK) and later developed recurrence of autoimmunity.MethodsWe examined pancreas transplant biopsies from nine SPK patients with or without recurrent autoimmunity or recurrent diabetes and from 16 non-diabetic organ donors. Tissues were analysed by immunohistochemistry and immunofluorescence.ResultsNumerous cytokeratin-19 (CK-19)+ pancreatic ductal cells stained for insulin in six SPK recipients with recurrent autoimmunity, in five of whom diabetes requiring insulin therapy recurred. These cells also stained for the transcription factor pancreatic-duodenal homeobox-1 (Pdx-1), which is implicated in pancreatic development and beta cell differentiation. The number of insulin+ ductal cells varied, being highest in the patient with the most severe beta cell loss and lowest in the normoglycaemic patient. In the patient with the most severe beta cell loss, we detected insulin+CK-19+Pdx-1+ cells staining for the proliferation-related Ki-67 antigen (Ki-67), indicating proliferation. We were unable to detect Ki-67+ beta cells within the islets in any SPK patient. Some insulin+CK-19– ductal cells contained chromogranin A, suggesting further endocrine differentiation. Insulin+ cells were rarely noted in the pancreas transplant ducts in three SPK patients without islet autoimmunity and in six of 16 non-diabetic organ donors; these insulin+ cells were never CK-19+.Conclusions/interpretationInsulin+ pancreatic ductal cells, some apparently proliferating, were found in the transplanted pancreas with recurrent islet autoimmunity/diabetes. Replicating beta cells were not detected within islets. The observed changes may represent attempts at tissue remodelling and beta cell regeneration involving ductal cells in the human transplanted pancreas, possibly stimulated by hyperglycaemia and chronic inflammation.

Randomized Trial of Immunosuppressive Regimens in Renal Transplantation

The optimal long-term regimen for immunosuppression for kidney transplant recipients is unknown. We conducted a randomized trial involving 150 kidney transplant recipients to compare tacrolimus/sirolimus, tacrolimus/mycophenolate mofetil (MMF), and cyclosporine/sirolimus. All patients received daclizumab induction and maintenance corticosteroids. Median follow-up was 8 yr post-transplant. Acute rejection (AR) occurred significantly less often among those treated with tacrolimus/MMF (12%) than among those treated with tacrolimus/sirolimus (30%) or cyclosporine/sirolimus (28%). Mean estimated GFR was consistently higher in the tacrolimus/MMF arm, especially after controlling for donor age in a multivariable model during the first 36 mo (P ≤ 0.008). The rate of dying with a functioning graft was significantly higher among those treated with tacrolimus/sirolimus (26%) than among those treated with tacrolimus/MMF (12%) or cyclosporine/sirolimus (4%). We did not observe significant differences in actuarial graft survival at 8 yr post-transplant between the groups. Patient noncompliance seemed responsible for 45% (13/29) of observed graft failures, with 11 of these occurring after 36 mo. Significantly more viral infections, protocol violations, and need for antilipid therapy occurred among patients receiving sirolimus, but we did not observe differences between the groups with regard to infections requiring hospitalization or new-onset diabetes. Taken together, these results suggest that maintenance therapy with tacrolimus/MMF is more favorable than either tacrolimus/sirolimus or cyclosporine/sirolimus.

Minimization and withdrawal of steroids in pancreas and islet transplantation

For reducing the corticosteroid (CS)‐related side‐effects, especially cardiovascular events, CS‐sparing protocols have become increasingly common in pancreas transplantation (PT). Lympho‐depleting induction antibodies, such as rabbit anti‐thymocyte globulin (rATG) or alemtuzumab, have been widely used in successful trials. The results of various CS‐sparing protocols combining calcineurin inhibitors (CNI) and mycophenolate or sirolimus, have been mixed for rejection and survival rates. Most of the studies were uncontrolled trials of low‐risk patients, therefore the grade of evidence is limited. Large‐scale prospective studies with long‐term follow up are necessary to assess risks and benefits of CS‐sparing regimens in PT before recommending such strategies as standard practice. Islet allo‐transplantation for patients with brittle type 1 diabetes mellitus, less invasive and safer procedure than PT, has been attempted since late 1980s, but diabetogenic immunosuppressants at maintenance, mainly CS and high‐dose CNI, prevented satisfactory results (10% insulin‐independence at 1‐year post‐transplant). Since 2000, CS‐free and CNI‐reducing protocols, including more potent induction [daclizumab, OKT3γ1(ala‐ala) anti‐CD3 antibody, rATG] and maintenance (sirolimus, mycophenolate) agents, have significantly improved short‐term outcomes whereas long‐term are still inadequate (from 80% to 20% insulin‐independence from 1‐ to 5‐year post‐transplant). Main limitations are allo‐ and autoimmunity, immunosuppression‐related islet and systemic toxicity and transplant site unsuitability, which tolerogenic protocols and biotechnological solutions may solve.