Factors associated with proteinuria in renal transplant recipients treated with sirolimus

Rapamycin promotes podocyte migration through the up-regulation of urokinase receptor

Conversion to rapamycin from calcineurin inhibitors may contribute to improvement of graft function in kidney transplant recipients, especially in patients with calcineurin inhibitor-related nephrotoxicity. The conversion from calcineurin inhibitors to rapamycin in kidney transplant recipients has been associated with a higher incidence of proteinuria. It could be explained by possible hemodynamic changes due to withdrawal of calcineurin inhibitors. Podocyte damage occurs commonly in rapamycin-related proteinuria. The vascular endothelial growth factor system has been suggested to be implicated in mammalian target of rapamycin inhibitor-associated proteinuria. However, induction of urokinase receptor (uPAR) signaling in podocytes leads to foot process effacement and urinary protein. In this study, we assessed the role of uPAR in primary cultured podocytes with rapamycin treatment. Our results indicate that 24-hour rapamycin treatment promotes podocyte migration on the wound scratch assay in a dose-dependent manner. Rapamycin treatment for 2 days does not increase the apoptosis of podocytes or affect the podocyte cell viability and morphology. The up-regulation of uPAR in podocytes was confirmed by immunofluorescence staining, real-time polymerase chain reaction (1.8 ± 0.3-fold increase of relative quantification; P < .01) and Western blot analysis. Rapamycin treatment also causes the activation of FAK and ILK in a dose-dependent manner. In summary, rapamycin could promote podocyte migration through the up-regulation of uPAR. This finding provides a new mechanism of rapamycin-associated proteinuria. It also suggests that pharmacologic inhibition of uPAR signaling cascade may have therapeutic potential in the setting of rapamycin-related proteinuria.

Five-year follow-up of patients with type 1 diabetes transplanted with allogeneic islets: the UIC experience

This report summarizes a 5-year phase 1/2 allogeneic islet transplantation clinical trial conducted at the University of Illinois at Chicago (UIC). Ten patients were enrolled in this single center, open label, and prospective trial in which patients received 1-3 transplants. The first four subjects underwent islet transplantation with the Edmonton immunosuppressive regimen and the remaining six subjects received the UIC immunosuppressive protocol (Edmonton plus etanercept and exenatide). All 10 patients achieved insulin independence after 1-3 transplants. At 5 years of follow-up, 6 of the initial 10 patients were free of exogenous insulin. During the follow-up period, 7 of the 10 patients maintained positive C-peptide levels and a composite hypoglycemic score of 0. Most patients maintained HbA1c levels <6.0 % (42.1 mmol/mol) and a significantly improved β-score. In conclusion, this study demonstrated long-term islet graft function without using T cell depleting induction, with an encouraging outcome that includes 60 % of patients remaining insulin independent after 5 years of initial transplantation.

A prospective, multinational pharmacoepidemiological study of clinical conversion to sirolimus immunosuppression after renal transplantation

This prospective pharmacoepidemiological study examined treatment and outcomes in patients converted to sirolimus (SRL) after renal transplantation. 484 subjects in 36 centres in 7 countries were followed for up to 5 years. Principal reasons for conversion were declining graft function (146/484, 30%) and side effects of prior therapy (144/484, 30%) and the major treatment combinations after conversion were SRL ± MMF (62%), SRL + TAC (21.5%), SRL + CSA (16.5%). The cumulative probability of biopsy-confirmed acute rejection (BCAR) was 5% (n = 22), death-censored graft loss 12% (n = 56) and death 6% (n = 22), and there was no significant relationship to the treatment combination employed. Median calculated creatinine clearance was 48.4 (29.3, 64.5) mL/min at conversion, rising to 54.1 (41.2, 69.0) mL/min at month 1, 55.7 (39.0, 73.0) mL/min at month 12, 58.6 (39.7, 75.2) mL/min at two years and 60.9 (36.0, 77.0) mL/min at three years post-conversion. The most common adverse events were hypertension (47%), hyperlipidemia (26%), urinary tract infections (25%), anaemia (24%) and diarrhea (14%), and cardiac events, hyperlipemia and CMV infection were more common in patients converted during the first year. SRL was most frequently combined with MMF after conversion, but principal clinical outcomes were not significantly influenced by the treatment combination employed in normal practice.

Everolimus as primary immunosuppression in kidney transplantation: experience in conversion from calcineurin inhibitors

BACKGROUND

We analyzed our clinical experience with everolimus (EVL) and identified prognostic factors for a successful conversion.

METHODS

Retrospective study of 220 kidney recipients consecutively converted to EVL with calcineurin inhibitor elimination. We studied risk factors for proteinuria at 1 year after conversion, decline in renal function, and graft survival.

RESULTS

Baseline creatinine clearance was 52.4±17.8 mL/min vs. 53.4±20.1 mL/min 1 year after conversion (P=0.150). Median proteinuria increased from 304 mg/day (interquartile range 160-507) to 458 mg/day (interquartile range 238-892; P<0.001). Risk factors for development of proteinuria ≥900 mg/day (P75) at 1-year postconversion were creatinine clearance less than 60 mL/min (odds ratio [OR] 3.37; 95% confidence interval [CI]: 1.15-9.89), serum triglycerides ≥150 mg/day (OR 4.35; 95% CI: 1.70-11.17), no treatment with prednisone (OR 3.04; 95% CI: 1.22-7.59), baseline proteinuria ≥550 mg/day (OR 10.37; 95% CI: 3.99-26.99), and conversion ≥3 years after transplant (OR 5.77; 95% CI: 1.89-17.59). An interaction was observed between baseline proteinuria and time to conversion: in patients with baseline proteinuria ≥550 mg/day, the risk of developing proteinuria ≥900 mg/day was 77.1% if they were converted after ≥3 years posttransplant. However, this risk was 29.8% in the subgroup converted before (P=0.02). Actuarial graft survival at 1 and 4 years postconversion was 98.2% and 86.5%, respectively. Baseline proteinuria ≥550 mg/day was a risk factor for graft loss in patients converted after the third year but not in patients converted before this time. EVL discontinuation rate was 24% in the first year postconversion.

CONCLUSIONS

Conversion to EVL and elimination of calcineurin inhibitors is safe. Success depends on not making late conversions and not converting patients with high baseline proteinuria.

Loss of nephrin expression in glomeruli of kidney-transplanted patients under m-TOR inhibitor therapy

The development of proteinuria has been observed in kidney-transplanted patients on m-TOR inhibitor (m-TORi) treatment. Recent studies suggest that m-TORi(s) may alter the behavior and integrity of glomerular podocytes. We analyzed renal biopsies from kidney-transplanted patients and evaluated the expression of nephrin, a critical component of the glomerular slit-diaphragm. In a group of patients on 'de novo' m-TORi-treatment, the expression of nephrin within glomeruli was significantly reduced in all cases compared to pretransplant donor biopsies. Biopsies from control transplant patients not treated with m-TORi(s) failed to present a loss of nephrin. In a group of patients subsequently converted to m-TORi-treatment, a protocol biopsy performed before introduction of m-TORi was also available. The expression of nephrin in the pre-m-TORi biopsies was similar to that observed in the pretransplant donor biopsies but was significantly reduced after introduction of m-TORi(s). Proteinuria increased after the m-TORi inititiation in this group. However, in some cases proteinuria remained normal despite reduction of nephrin. In vitro, sirolimus downregulated nephrin expression by human podocytes. Our results suggest that m-TORi(s) may affect nephrin expression in kidney-transplanted patients, consistently with the observation in vitro on cultured podocytes.

Clinical predictors of proteinuria after conversion to sirolimus in kidney transplant recipients

Proteinuria is an increasingly recognized effect of sirolimus (SRL) therapy in kidney transplant recipients. Predictors of proteinuria after conversion to SRL are not well described, and in particular the risk in African-American (AA) kidney recipients is unknown. We sought to analyze risk factors for proteinuria with SRL therapy in a cohort of 39 patients (44% AA) converted from tacrolimus to SRL at a mean time of 4 months posttransplantation. Patients were maintained on therapy with mycophenolate mofetil while most patients underwent early steroid withdrawal. Urinary protein to creatinine ratio (Up/cr) at a mean of 14 months postconversion increased to > or =500 mg/g in 65% of AAs versus 14% of non-AAs (p = 0.001). Mean arterial blood pressure at the time of conversion and pretransplant proteinuric kidney disease were also predictors of proteinuria after SRL conversion. In conclusion, AAs appear to be at high risk for proteinuria and should be monitored closely after conversion to SRL in calcineurin inhibitor sparing protocols.