Development of proteinuria after switch to sirolimus-based immunosuppression in long-term cardiac transplant patients

A quantitative assessment of renal function utilizing albuminuria in pediatric heart transplant recipients

INTRODUCTION

Kidney disease is common after pediatric heart transplantation. Serum creatinine-based glomerular filtration rate is the most frequently reported measure of kidney function. Albuminuria is an additional marker of kidney dysfunction and is not well described in this population. In this study, we evaluate the prevalence and degree of albuminuria and describe clinical factors associated with albuminuria in a cohort of pediatric heart transplant recipients.

METHODS

This was a cross-sectional study of pediatric heart transplant recipients. Albuminuria was assessed using spot urine albumin-to-creatinine ratio collected at the most recent annual screening cardiac catheterization through August 2019.

RESULTS

In 115 patients at a median duration of 10.2 years post-transplant, 39% had albuminuria. Stage 3 or greater chronic kidney disease was present in 6%. The immunosuppressive regimen at the time of measurement contained a calcineurin inhibitor (CNI) in 88% and a proliferation signal inhibitor (PSI) in 62%. In multivariable modeling, lower eGFR, PSI use, and younger age at transplant were associated with higher levels of albuminuria, whereas CNI use was associated with lower levels of albuminuria.

CONCLUSION

Albuminuria is a prevalent finding in medium-term follow up of pediatric heart transplant recipients, reflecting kidney injury, and is associated with other markers of kidney dysfunction, such as low eGFR. Younger age at transplant, lower eGFR, and PSI use were among the associations with albuminuria.

Effects and mechanism of Rictor interference in podocyte injury induced by high glucose

Rapamycin-insensitive companion of mTOR (Rictor) is a critical effector of mTOR protein complex 2 (mTORC2). The aim of the present study was to investigate the effect of Rictor in the mTORC2 signaling pathway in high glucose (HG)-induced diabetic podocyte injury by silencing the expression of Rictor. In the present study, mouse podocytes were treated with glucose (150 mM) and mannitol (200 mM), the Rictor gene was silenced using small interfering RNA (siRNA). Apoptosis was detected by flow cytometry, whereas podocyte cytoskeletal protein expression was detected by western blotting (WB) and immunofluorescence staining. The results demonstrated that, compared with that in the control group, the podocyte apoptotic rate was significantly increased in the mannitol group (negative group) and the groups that were treated with glucose (model groups). The podocyte apoptotic rate in the model + Rictor siRNA group was significantly decreased compared with that in the negative, model and the model glucose + siRNA negative control (NC) groups. WB indicated that the protein expression levels of podocalyxin and synaptopodin were reduced in the model and model + siRNA NC groups compared with those in the normal control and negative groups. Additionally, the protein expression levels of α-smooth muscle actin (α-SMA) and P-AKT/AKT were increased in the model and model + siRNA NC groups compared with the those in control and negative groups. Compared with those the model and model + siRNA NC groups, the protein expression levels of podocalyxin and synaptopodin were increased, whilst those of the α-SMA and P-AKT/AKT proteins were decreased, in the model + Rictor siRNA group. Results from immunofluorescence analysis were basically consistent with those of WB. Therefore, results of the present study suggest that silencing of the Rictor gene may reduce the damage to podocytes induced by HG, such that the Rictor/mTORC2 signaling pathway may be involved in the remodeling of podocyte actin cytoskeletal in diabetes.

Rapamycin treatment induces tubular proteinuria: role of megalin-mediated protein reabsorption

Introduction: Rapamycin is an immunosuppressor that acts by inhibiting the serine/threonine kinase mechanistic target of rapamycin complex 1. Therapeutic use of rapamycin is limited by its adverse effects. Proteinuria is an important marker of kidney damage and a risk factor for kidney diseases progression and has been reported in patients and animal models treated with rapamycin. However, the mechanism underlying proteinuria induced by rapamycin is still an open matter. In this work, we investigated the effects of rapamycin on parameters of renal function and structure and on protein handling by proximal tubule epithelial cells (PTECs). Methods: Healthy BALB/c mice were treated with 1.5 mg/kg rapamycin by oral gavage for 1, 3, or 7 days. At the end of each treatment, the animals were kept in metabolic cages and renal function and structural parameters were analyzed. LLC-PK1 cell line was used as a model of PTECs to test specific effect of rapamycin. Results: Rapamycin treatment did not change parameters of glomerular structure and function. Conversely, there was a transient increase in 24-h proteinuria, urinary protein to creatinine ratio (UPCr), and albuminuria in the groups treated with rapamycin. In accordance with these findings, rapamycin treatment decreased albumin-fluorescein isothiocyanate uptake in the renal cortex. This effect was associated with reduced brush border expression and impaired subcellular distribution of megalin in PTECs. The effect of rapamycin seems to be specific for albumin endocytosis machinery because it did not modify renal sodium handling or (Na⁺+K⁺)ATPase activity in BALB/c mice and in the LLC-PK1 cell line. A positive Pearson correlation was found between megalin expression and albumin uptake while an inverse correlation was shown between albumin uptake and UPCr or 24-h proteinuria. Despite its effect on albumin handling in PTECs, rapamycin treatment did not induce tubular injury measured by interstitial space and collagen deposition. Conclusion: These findings suggest that proteinuria induced by rapamycin could have a tubular rather than a glomerular origin. This effect involves a specific change in protein endocytosis machinery. Our results open new perspectives on understanding the undesired effect of proteinuria generated by rapamycin.

Clinical efficacy and safety of sirolimus in systemic lupus erythematosus: a real-world study and meta-analysis

Objective:

To provide real-world data and summarize current clinical evidence on the efficacy and safety of sirolimus in active systemic lupus erythematosus (SLE) patients.

Methods:

This was a prospective real-world clinical study. Included SLE patients should have Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) ⩾ 2. They were treated with sirolimus and followed up regularly. The SLEDAI-2K, Physician Global Assessment (PGA), serological activity indices, and remission of organ manifestations were evaluated. We also performed a meta-analysis to integrate current evidence of sirolimus in SLE.

Results:

A total of 49 patients were included in the final analysis. After treatment, the SLEDAI-2K (6.2 ± 3.1 versus 4.0 ± 3.4, p = 0.001) decreased significantly, and the prednisone dosage was tapered successfully (9.9 ± 8.8 mg/day versus 5.9 ± 4.0 mg/day, p = 0.002). Serological activity indices also improved [complement 3 (C3): 0.690 ± 0.209 g/l versus 0.884 ± 0.219 g/l, p < 0.001; complement 4: 0.105 ± 0.059 g/l versus 0.141 ± 0.069 g/l, p < 0.001; anti-dsDNA antibody, 200 ± 178 IU/ml versus 156 ± 163 IU/ml, p = 0.022]. The remission proportions of arthritis, skin rash, and thrombocytopenia were 100%, 88.8%, and 46.2%, respectively. A total of 41.2% of lupus nephritis (LN) patients achieved renal remission, but the average 24-h urine protein level was not significantly changed. Meta-analysis enrolled five studies with 149 patients included, and revealed similar results regarding the changes of SLEDAI-2K [−3.5 (−5.0, −2.1)], C3 [0.224 (0.136, 0.311) g/l] and daily dosage of prednisone [−12.7 (−19.9, −5.6) mg/day].

Conclusion:

Sirolimus might be effective and tolerated in SLE. The role of sirolimus in LN requires further study.

The role of sirolimus in proteinuria in diabetic nephropathy rats

Objective(s):

The aim of this study was to observe the impact of sirolimus on proteinuria in streptozotocin (STZ) induced diabetic rats.

Materials and Methods:

Rats were given a single injection of STZ to induce diabetic rat model. Rats’ 24 hr urine was collected to test, urinary and the kidney tissues were harvested at the 8^th and 20^th weeks, respectively. Podocyte morphological changes were examined by electron microscopy and the ZO-1, podocin expressions in kidneys were detected by immunohistochemistry; the protein levels of Raptor and pS6 were measured by Western blot assay.

Results:

In the early stage of diabetic nephropathy (DN), sirolimus reduced the proteinuria significantly (P<0.05); but in the advanced stage of DN, sirolimus worsened proteinuria (P<0.05). Electron microscopy test suggested that sirolimus could reduce the injury of podocyte at the early DN, but increased the injury at the late DN podocyte. Immunohistochemistry results indicated that sirolimus increased the expressions of podocin and ZO-1 at the early DN (P<0.05), but reduced the expressions of ZO-1 and podocin (P<0.05) at the advanced DN. In the different periods of DN, the expression levels of Raptor and pS6 in sirolimus-treated groups were significantly lower than in the DN control groups (P<0.05).

Conclusion:

Sirolimus can reduce proteinuria and alleviate the early DN podocyte injury in diabetic rat model by inhibiting the activity of mTORC1; but in the advanced stage of DN, sirolimus can increase podocyte injury and urine protein level.

Proteinuria and baseline renal function predict mortality and renal outcomes after sirolimus therapy in liver transplantation recipients

Background

Chronic kidney disease is a significant complication after liver transplantation (LT), but the role of pre-existing renal insufficiency and proteinuria remains unclear among LT recipients receiving sirolimus.

Methods

We assessed the effects of proteinuria and baseline renal function on long-term renal and survival outcomes among 576 LT recipients who received SRL in a medical center between 2005 and 2014. Renal outcomes were the incidences of >50% reduction in their baseline estimated glomerular filtration rate and end stage kidney disease requiring renal replacement therapy. Proteinuria was identified using morning dipstick results (≥30 mg/dL) at baseline and within the first year after the initiation of SRL therapy. A Kaplan-Meier analysis was performed to estimate time to event. Factors associated with the outcomes were determined using the Cox proportional hazards model with a significance level set at P <0.05.

Results

During the study period, renal function deteriorated in 135 (25.3%) patients and 68 (11.8%) patients died. Persistent and new onset proteinuria contributed to a high rate of mortality and the deterioration of renal function (both log-rank tests, P <0.0001). After adjustments, new onset proteinuria within the first year after the initiation of SRL therapy increased the risk of deteriorating renal function, regardless of baseline estimated glomerular filtration rate. Moreover, pre-existing (hazard ratio = 1.91; P <0.001) and new onset diabetes (hazard ratio = 2.34; P <0.0001) were significantly associated with new onset proteinuria among SRL users.

Conclusions

These findings support the effective monitoring and early management of the predictable risks for proteinuria among new SRL users in order to delay the progression of renal disease.

Effect of Calcineurin Inhibitor-Free, Everolimus-Based Immunosuppressive Regimen on Albuminuria and Glomerular Filtration Rate After Heart Transplantation

BACKGROUND

Albuminuria in maintenance heart transplantation (HTx) is associated with poor renal response when switching to a calcineurin inhibitor (CNI)-lowered or CNI-free immunosuppressive regimen using everolimus (EVR), but the significance of albuminuria associated with EVR treatment after early CNI withdrawal in de novo HTx is unknown.

METHODS

We tested if measured glomerular filtration rate (mGFR, by chrome-ethylenediaminetetraacetic acid clearance) was associated with urine albumin/creatinine ratio (UACR) post-HTx in a subgroup of patients included in the Scandinavian Heart Transplant Everolimus De Novo Study With Early Calcineurin Inhibitor Avoidance trial, where de novo HTx patients (n = 115) were randomized to EVR with complete CNI elimination 7 to 11 weeks post-HTx or standard CNI immunosuppression.

RESULTS

In 66 patients, UACR measures were available at 1 year. In 7 patients in the EVR group, a CNI was reintroduced within 12 months. Median mGFR was significantly higher in the EVR group both 1 and 3 years post-HTx (P = 0.0004 and P = 0.03, respectively). Median UACR at 1 year was significantly higher in the EVR group (P = 0.002). There was no correlation between log(UACR) at 1 year and mGFR at 1 or 3 years (r = -0.01, P = 0.9 and r = 0.15, P = 0.26, respectively) and in the EVR group between log(UACR) at 1 year and change in mGFR (Δ1-3 years) (r = 0.27, P = 0.14). Excluding patients in the EVR group in whom a CNI was reintroduced did not significantly change the results.

CONCLUSIONS

The effects of EVR with early CNI withdrawal after HTx on albuminuria and renal function seem dissociated; hence, the clinical significance of albuminuria in this setting is uncertain and should not necessarily rule out EVR-based immunosuppression.

Tacrolimus combined with low-dose corticosteroids is an effective and safe therapeutic option for refractory IgA nephropathy

Tacrolimus (TAC) has been shown to improve remission from proteinuria in patients with refractory IgA nephropathy (IgAN); however, the efficacy and safety of TAC in such patients have not been fully explored. Therefore, the present study was conducted to evaluate the tolerance to and efficacy of TAC combined with low-dose corticosteroids in patients with refractory IgAN. This was a single-center retrospective study. A total of 28 patients with refractory IgAN were randomly included and received TAC plus corticosteroid; 26 patients received TAC and prednisone, and 2 patients received TAC and methylprednisolone. In addition, all patients were treated with an angiotensin inhibitor. Total urinary protein excretion, serum albumin, blood glucose, complete remission (CR), partial remission (PR), cholesterol, low-density lipoprotein (LDL), serum creatinine (Scr) and estimated GFR (eGFR) were tested at baseline and at 3, 6 and 12 months after the initiation of treatment in all patients. The primary endpoints were CR and PR. Secondary endpoints included changes of Scr, eGFR, clinical data and adverse events. After 12 months, CR was achieved in 40.1% of patients and PR in 43.4%, yielding a total response rate of 83.5%, and the total urinary protein excretion, serum albumin, cholesterol and LDL results were improved significantly compared with those at baseline. Proteinuria and serum albumin results were significantly improved by month 3 of treatment. Two patients relapsed during months 3-6 of follow-up. At the 12-month follow-up, renal function was improved compared with the baseline level as evidenced by eGFR and Scr, respectively. The blood glucose level was stable. One case of pneumococcal pneumonia developed in a patient treated with TAC plus low-dose methylprednisolone and one case of upper gastrointestinal hemorrhage was found in a patient treated with TAC plus low-dose prednisone; both cases completely recovered after treatment. In conclusion, TAC combined with low-dose corticosteroids may be an effective and safe therapeutic option for the treatment of refractory IgAN. However, given the small number of patients in this study, further prospective randomized controlled trials are required with a larger sample of participants and longer follow-up period.

Acute Kidney Disease After Liver and Heart Transplantation

After transplantation of nonrenal solid organs, an acute decline in kidney function develops in the majority of patients. In addition, a significant number of nonrenal solid organ transplant recipients develop chronic kidney disease, and some develop end-stage renal disease, requiring renal replacement therapy. The incidence varies depending on the transplanted organ. Acute kidney injury after nonrenal solid organ transplantation is associated with prolonged length of stay, cost, increased risk of death, de novo chronic kidney disease, and end-stage renal disease. This overview focuses on the risk factors for posttransplant acute kidney injury after liver and heart transplantation, integrating discussion of proteinuria and chronic kidney disease with emphasis on pathogenesis, histopathology, and management including the use of mechanistic target of rapamycin inhibition and costimulatory blockade.

Belatacept for renal rescue in lung transplant patients

Renal failure causes morbidity and mortality after lung transplantation and is aggravated by exposure to nephrotoxic immunosuppressant (IS) drugs. We report an off-label experience using belatacept for lung transplant recipients with severe renal insufficiency to reduce nephrotoxic IS exposure. We analyzed data retrospectively from a consecutive series of lung transplant patients with renal insufficiency in whom belatacept treatment was initiated between June 2012 and June 2014 at the University of Maryland Medical Center. Eight patients received belatacept because of acute or chronic renal insufficiency (median) GFR 24 (IQR 18-26). Glomerular filtration rate (GFR) remained stable in two patients and increased in five. One patient with established renal and respiratory failure received only the induction dose of belatacept and died 4 months later of respiratory and multisystem organ failure. Calcineurin inhibitor or sirolimus exposure was safely withheld or reduced without moderate or severe acute rejection during ongoing belatacept in the other seven patients. FEV1 remained stable over the 6-month study interval. Belatacept use appears to permit safe transient reduction in conventional immunosuppressive therapy and was associated with stable or improved renal function in a small retrospective series of lung transplant recipients with acute or chronic renal insufficiency.

Safety of mTOR inhibitors in adult solid organ transplantation

INTRODUCTION

Mammalian target of rapamycin (mTOR) inhibitors (sirolimus and everolimus) are a class of immunosuppressive drugs approved for solid organ transplantation (SOT). By inhibiting the ubiquitous mTOR pathway, they present a peculiar safety profile. The increased incidence of serious adverse events in early studies halted the enthusiasm as a kidney sparing alternative to calcineurin inhibitors (CNI).

AREAS COVERED

Herein we review mTOR inhibitors safety profile for adult organ transplantation, ranging from acute side effects, such as lymphoceles, delayed wound healing, or cytopenias, to long-term ones which increase morbidity and mortality, such as cancer risk and metabolic profile. Infection, proteinuria, and cutaneous safety profiles are also addressed.

EXPERT OPINION

In the authors' opinion, mTOR inhibitors are a safe alternative to standard immunosuppression therapy with CNI and mycophenolate/azathioprine. Mild adverse events can be easily managed with an increased awareness and close monitoring of trough levels. Most serious side effects are dose- and organ-dependent. In kidney and heart transplantation mTOR inhibitors may be safely used as either low-dose de novo or through early-conversion. In the liver, conversion 4 weeks post-transplantation may reduce long-term chronic kidney disease secondary to calcineurin nephrotoxicity, without increasing hepatic artery/portal vein thrombosis.

Chronic renal insufficiency in heart transplant recipients: risk factors and management options

Renal dysfunction after heart transplantation is a frequently observed complication, in some cases resulting in significant limitation of quality of life and reduced survival. Since the pathophysiology of renal failure (RF) is multifactorial, the current etiologic paradigm for chronic kidney disease after heart transplantation relies on the concept of calcineurin inhibitor (CNI)-related nephrotoxicity acting on a predisposed recipient. Until recently, the management of RF has been restricted to the minimization of CNI dosage and general avoidance of classic nephrotoxic risk factors, with somewhat limited success. The recent introduction of proliferation signal inhibitors (PSIs) (sirolimus and everolimus), a new class of immunosuppressive drugs lacking intrinsic nephrotoxicity, has provided a completely new alternative in this clinical setting. As clinical experience with these new drugs increases, new renal-sparing strategies are becoming available. PSIs can be used in combination with reduced doses of CNIs and even in complete CNI-free protocols. Different strategies have been devised, including de novo use to avoid acute renal toxicity in high-risk patients immediately after transplantation, or more delayed introduction in those patients developing chronic RF after prolonged CNI exposure. In this review, the main information on the clinical relevance and pathophysiology of RF after heart transplantation, as well as the currently available experience with renal-sparing immunosuppressive regimens, particularly focused on the use of PSIs, is reviewed and summarized, including the key practical points for their appropriate clinical usage.

Conversion from calcineurin inhibitors to mTOR inhibitors stabilizes diabetic and hypertensive nephropathy after liver transplant

AIM: To investigate if conversion to the mammalian target of rapamycin inhibitors (mTORi) improves renal function in diabetic and/or hypertensive liver transplant patients immunosuppressed with tacrolimus or cyclosporine.

METHODS: The study included 86 liver graft recipients immunosuppressed with mTORi treatment after orthotopic liver transplantation (OLT), including all liver recipients with worsening renal function before conversion to mTORi (n = 55 patients) and recipients with normal renal function who converted to mTORi for other reasons (n = 31 patients). We identified patients with diabetes mellitus (n = 28), arterial hypertension (n = 27), proteinuria (n = 27) and all three factors (n = 8) (some patients have hypertension and diabetes and no proteinuria). The primary endpoint was evolution in renal function defined as the development in plasma creatinine as a function of diabetes mellitus (DM), hypertension (HT) or proteinuria. We required elevated serum creatinine for at least two weeks to define renal dysfunction.

RESULTS: Only patients that converted because of renal failure with plasma creatinine levels > 1.5 mg/dL showed an improvement of renal function (2.14 to 1.77 mg/dL) (P = 0.02). Patients with DM showed no improvement of serum creatinine levels (1.31 mg/dL to 1.37 mg/dL) compared with non DM patients (1.31 mg/dL to 1.15 mg/dL) (P = 0.01), HT patients (1.48 mg/dL to 1.5 mg/dL) with non HT patients (1.21mg/dL to 1.08 mg/dL) and patients with proteinuria (1.44 mg/dL to 1.41 mg/dL) and no proteinuria (1.31 mg/dL to 1.11 mg/dL).

CONCLUSION: In OLT recipients with diabetes or hypertensive nephropathy, conversion to mTORi does not improve renal function but stabilizes plasma levels of creatinine. Proteinuria is not a contraindication to conversion to mTORi; it also stabilizes renal function. Conversion to mTORi should only be avoided in patients with diabetes, hypertension and proteinuria.

Sirolimus conversion after heart transplant: risk factors for acute rejection and predictors of renal function response

In a randomized, comparative study of cardiac transplant patients with mild-to-moderate renal insufficiency, conversion from calcineurin inhibitors (CNIs) to sirolimus improved renal function at 1 year versus continuing CNIs, with an attendant risk of biopsy-confirmed acute rejection (BCAR). Post hoc analyses were conducted to identify predictors of BCAR and GFR improvement associated with conversion. Patients with proteinuria >500 mg/day were excluded. Univariate and multivariate regression analyses tested 13 parameters for BCAR and six for GFR improvement. In 57 sirolimus-treated patients, mean daily mycophenolate mofetil (MMF) dose was lower in those with versus without BCAR (1000 vs. 1420 mg; p = 0.014). Receiver operating characteristic analysis identified MMF dose ≤1000 mg/day as the optimal cutoff to predict BCAR. Multivariate analysis confirmed low MMF dose (odds ratio: 9.94; p = 0.007) and non-white race (odds ratio: 15.3; p = 0.06) were independently associated with BCAR. GFR improvement was evaluated in intent-to-treat patients (n = 116). Significant interaction was detected between treatment effect and preexisting diabetes status (univariate p = 0.077; multivariate p = 0.022), indicating greater beneficial effect of sirolimus in those without preexisting diabetes. These findings suggest that sirolimus is more effective in improving GFR in patients without preexisting diabetes, and adequate MMF doses are needed for sirolimus conversion.

Sirolimus Immunoprophylaxis and Renal Histological Changes in Long-Term Cardiac Transplant Recipients

Background: The effects of sirolimus (SIR), as a substitution for calcineurin inhibitor (CNI) immunoprophylaxis, on renal function in very-long-term cardiac transplant recipients have been a matter of controversy. Objective: To assess the impacts of SIR as a substitution for CNI on renal function up to 24 months in long-term cardiac recipients as well as the renal histological changes in patients with suspected CNI-induced nephrotoxicity. Methods: A total of 23 cardiac transplant recipients aged 57.7 ± 11.2 years, 91 months post–cardiac transplantation were recruited; 15 patients were randomized to CNI-free immune suppression with SIR, and 8 patients were allocated to continue their CNI regimens. Serum creatinine and calculated serum creatinine clearance were measured at prespecified time points up to 24 months. Renal structure and function were assessed by renal biopsies, renal ultrasound, and magnetic resonance imaging at baseline. Results: There were no significant changes in creatinine clearance during the course of the study in patients treated with SIR. However, SIR-treated patients exhibited a significant decrease in 24-hours and nighttime systolic and diastolic blood pressures. Typical findings of significant hypertensive renal disease were detected in 9 of the 11 (82%) patients. Features of chronic CNI toxicity were detected in 6 (55%) patients. Conclusions: There is a very high rate of hypertensive renal disease concomitantly with some degree of CNI toxicity in long-term cardiac transplant recipients with renal dysfunction. This very high rate of hypertension-related disease may limit the impact of SIR on improving renal function long term following cardiac transplantation.

Plasma NGAL and glomerular filtration rate in cardiac transplant recipients treated with standard or reduced calcineurin inhibitor levels

AIM

Predictors of renal recovery following conversion from calcineurin inhibitor- to proliferation signal inhibitor-based therapy are lacking. We hypothesized that plasma NGAL (P-NGAL) could predict improvement in glomerular filtration rate (GFR) after conversion to everolimus.

PATIENTS & METHODS

P-NGAL was measured in 88 cardiac transplantation patients (median 5 years post-transplant) with renal dysfunction randomized to continuation of conventional calcineurin inhibitor-based immunosuppression or switching to an everolimus-based regimen.

RESULTS

P-NGAL correlated with measured GFR (mGFR) at baseline (R(2) = 0.21; p < 0.001). Randomization to everolimus improved mGFR after 1 year (median [25-75 % percentiles]: ΔmGFR 5.5 [-0.5-11.5] vs -1 [-7-4] ml/min/1.73 m(2); p = 0.006). Baseline P-NGAL predicted mGFR after 1 year (R(2) = 0.18; p < 0.001), but this association disappeared after controlling for baseline mGFR.

CONCLUSION

P-NGAL and GFR correlate with renal dysfunction in long-term heart transplantation recipients. P-NGAL did not predict improvement of renal function after conversion to everolimus-based immunosuppression.

Use of mTOR inhibitors in chronic heart transplant recipients with renal failure: calcineurin-inhibitors conversion or minimization?

BACKGROUND

In the last decade, mTOR inhibitors (mTOR-is) have become the cornerstone of the calcineurin inhibitor (CNI)-reduced/free regimens aimed to the preservation of post-transplant renal function. We compared utility and safety of the total replacement of calcineurin inhibitors with a mTOR-i with a strategy based on calcineurin inhibitor minimization and concomitant use of m-TOR-i.

METHODS

In a retrospective multi-center cohort of 394 maintenance cardiac recipients with renal failure (GFR<60 mL/min/1.73 m(2)), we compared 235 patients in whom CNI was replaced with a mTOR-i (sirolimus or everolimus) with 159 patients in whom mTOR-is were used to minimize CNIs. A propensity score analysis was carried out to balance between group differences.

RESULTS

Overall, after a median time of 2 years from mTOR-i initiation, between group differences for the evolution of renal function were not observed. In a multivariate adjusted model, improvement of renal function was limited to patients with mTOR-i usage within 5years after transplantation, particularly with the conversion strategy, and in those patients who could maintain mTOR-i therapy. Significant differences between strategies were not found for mortality, infection and mTOR-i withdrawal due to drug-related adverse events. However, conversion group tended to have a higher acute rejection incidence than the minimization group (p=0.07).

CONCLUSION

In terms of renal benefits, our results support an earlier use of mTOR-is, irrespective of the strategy. The selection of either a conversion or a CNI minimization protocol should be based on the clinical characteristics of the patients, particularly their rejection risk.

Impact of calcineurin-inhibitor conversion to mTOR inhibitor on renal allograft function in a prednisone-free regimen

Traditionally, chronic calcineurin inhibitor (CNI) nephrotoxicity has been considered to be one of the main nonimmune mechanisms causing chronic renal allograft dysfunction. CNI minimization and withdrawal strategies have yielded inconsistent results. Few studies address the feasibility of CNI elimination in a prednisone-free regimen. We report a prospective, randomized trial in 200 patients evaluating the impact on renal function and incidence of acute rejection after conversion from tacrolimus (Tac) to sirolimus (SRL). Patients with recent (<3 months) acute rejection episodes or with >0.5 g/day of proteinuria were excluded. All were induced with alemtuzumab, underwent rapid steroid elimination and were maintained on mycophenolate mofetil and Tac. At 12 months posttransplant, patients were randomized 2:1 to SRL (n = 123) or maintained on Tac (n = 64). Mean follow-up was 41.1 ± 15.8 months in the SRL group and 40.7 ± 14.4 months in the Tac group. Biopsy-proven acute rejection at 24 months postrandomization was similar between the groups. Patient survival, graft survival and estimated GFR were also not statistically different. Our study demonstrates that in a prednisone-free immunosuppressive regimen, conversion from Tac to SRL at 12 months posttransplantation is not associated with increased rates of acute rejection and graft loss. However, despite CNI elimination, renal allograft function is equally maintained in both groups.

Regulation of blood-testis barrier (BTB) dynamics during spermatogenesis via the "Yin" and "Yang" effects of mammalian target of rapamycin complex 1 (mTORC1) and mTORC2

In mammalian testes, haploid spermatozoa are formed from diploid spermatogonia during spermatogenesis, which is a complicated cellular process. While these cellular events were reported in the 1960s and 1970s, the underlying molecular mechanism(s) that regulates these events remained unexplored until the past ∼10 years. For instance, adhesion proteins were shown to be integrated components at the Sertoli cell-cell interface and/or the Sertoli-spermatid interface in the late 1980s. But only until recently, studies have demonstrated that some of the adhesion proteins serve as the platform for signal transduction that regulates cell adhesion. In this chapter, a brief summary and critical discussion are provided on the latest findings regarding these cell-adhesion proteins in the testis and their relationship to spermatogenesis. Moreover, antagonistic effects of two mammalian target of rapamycin (mTOR) complexes, known as mTORC1 and mTORC2, on cell-adhesion function in the testis are discussed. Finally, a hypothetic model is presented to depict how these two mTOR-signaling complexes having the "yin" and "yang" antagonistic effects on the Sertoli cell tight junction (TJ)-permeability barrier can maintain the blood-testis barrier (BTB) integrity during the epithelial cycle while preleptotene spermatocytes are crossing the BTB.

Rejection after conversion to a proliferation signal inhibitor in chronic heart transplantation

We sought to determine the incidence, risk factors, and consequences of acute rejection (AR) after conversion from a calcineurin inhibitor (CNI) to a proliferation signal inhibitor (PSI) in maintenance heart transplantation. Relevant clinical data were retrospectively obtained for 284 long-term heart transplant recipients from nine centers in whom CNIs were replaced with a PSI (sirolimus or everolimus) between October 2001 and March 2009. The rejection rate at one yr was 8.3%, stabilizing to 2% per year thereafter. The incidence rate after conversion (4.9 per 100 patient-years) was significantly higher than that observed on CNI therapy in the pre-conversion period (2.2 per 100 patient-years). By multivariate analysis, rejection risk was associated with a history of late AR prior to PSI conversion, early conversion (<5 yr) after transplantation and age <50 yr at the time of conversion. Use of mycophenolate mofetil was a protective factor. Post-conversion rejection did not significantly influence the evolution of left ventricular ejection fraction, renal function, or mortality during further follow-up. Conversion to a CNI-free immunosuppression based on a PSI results in an increased risk of AR. Awareness of the clinical determinants of post-conversion rejection could help to refine the current PSI conversion strategies.

Mechanistic target of rapamycin inhibitors in solid organ transplantation: from benchside to clinical use

PURPOSE OF REVIEW

Here, we review recent advances and new insights in mechanistic target of rapamycin (mTOR) biology (signalling pathway, kidney biology and immune system), and recent clinical data on mTOR inhibitors related to solid organ transplantation.

RECENT FINDINGS

The mTOR pathway is a major integrator of signals governing protein and lipid biosynthesis and growth factor-driven cell cycle progression. Recent findings have emphasized a critical role of mTOR in cellular homeostasis with a crucial role in podocyte function. Beyond CD8(+) and regulatory T-cell control, mTOR protein is involved in critical biological functions of T helper cells or dendritic cells. New specific inhibitors of mTORC1/C2 are available and shed new light on mTOR functions. Finally, clinical trials have better defined the use of mTOR inhibitors and emphasized their role in cancer prevention.

SUMMARY

The mTOR pathway is considered as a key integrator of multiple inputs that drives numerous biological processes in cell biology. mTOR inhibitors are potent immunosuppressive drugs for solid organ transplantation. Newly designed specific inhibitors of mTOR complex 1 and 2 offer promising therapeutic effects and a better understanding of the pathway. Many conditions may benefit from mTOR inhibition for a short period, but tolerance of treatment in a chronic setting remains a major concern.

The effect of everolimus versus mycophenolate upon proteinuria following kidney transplant and relationship to graft outcomes

Although mTOR inhibitor use has been associated with proteinuria in kidney transplant recipients, dose dependency and impact on allograft function are unknown. In a post hoc analysis, we compared rates of proteinuria 3 months posttransplant among everolimus (EVR) and mycophenolate (MPA) treatment arms and used a time-dependent model to correlate the risk of proteinuria to EVR trough levels up to 24 months posttransplant. eGFR and graft loss was compared by proteinuria status at 3 months. Of 833 randomized patients, 24%, 36% and 19% of lower exposure EVR (1.5 mg/day), higher exposure EVR (3.0 mg/day) and MPA-treated patients had proteinuria ≥ 300 mg/g Cr at 3 months, respectively. EVR 1.5 was not associated with an increase in risk of proteinuria (HR 1.20; p = 0.19) unlike EVR 3.0 (HR 1.84; p < 0.001) versus MPA. EVR trough levels >8 ng/mL were significantly associated with proteinuria compared to 3-8 ng/mL (HR 1.86; p < 0.001). Those patients with proteinuria at 3 months and those who developed proteinuria thereafter had lower eGFR and higher graft loss at 24 months, regardless of treatment arm. We identify a dose-dependent effect of EVR with the risk of proteinuria; however, its independent impact upon eGFR and graft survival at 2 years was not evident.

Endothelial dysfunction and cardiac allograft vasculopathy

Cardiac allograft vasculopathy remains a major challenge to long-term survival after heart transplantation. Endothelial injury and dysfunction, as a result of multifactorial immunologic and nonimmunologic insults in the donor and the recipient, are prevalent early after transplant and may be precursors to overt cardiac allograft vasculopathy. Current strategies for managing cardiac allograft vasculopathy, however, rely on the identification and treatment of established disease. Improved understanding of mechanisms leading to endothelial dysfunction in heart transplant recipients may provide the foundation for the development of sensitive screening techniques and preventive therapies.

Randomized controlled trial of sirolimus conversion in cardiac transplant recipients with renal insufficiency

This randomized, comparative, multinational phase 3b/4 study of patients 1-8 years postcardiac transplantation (mean 3.9 years) evaluated the effect of conversion from a calcineurin inhibitor (CNI) to sirolimus on renal function in patients with renal insufficiency. In total, 116 patients on CNI therapy with GFR 40-90 mL/min/1.73 m(2) were randomized (1:1) to sirolimus (n = 57) or CNI (n = 59). Intent-to-treat analysis showed the 1-year adjusted mean change from baseline in creatinine clearance (Cockcroft-Gault) was significantly higher with sirolimus versus CNI treatment (+3.0 vs. -1.4 mL/min/1.73 m(2) , respectively; p = 0.004). By on-therapy analysis, values were +4.7 and -2.1, respectively (p < 0.001). Acute rejection (AR) rates were numerically higher in the sirolimus group; 1 AR with hemodynamic compromise occurred in each group. A significantly higher treatment discontinuation rate due to adverse events (AEs; 33.3% vs. 0%; p < 0.001) occurred in the sirolimus group. Most common treatment-emergent AEs significantly higher in the sirolimus group were diarrhea (28.1%), rash (28.1%) and infection (47.4%). Conversion to sirolimus from CNI therapy improved renal function in cardiac transplant recipients with renal impairment, but was associated with an attendant AR risk and higher discontinuation rate attributable to AEs.

Proteinuria following sirolimus conversion is associated with deterioration of kidney function in liver transplant recipients

BACKGROUND

The role of sirolimus (SRL) conversion in the preservation of kidney function in liver transplant (LT) recipients with calcineurin inhibitor (CNI) nephrotoxicity is unclear.

METHODS

Data on 102 LT recipients with deteriorating kidney function after CNI exposure who were later converted to SRL were retrospectively reviewed. Kidney function was assessed using serum creatinine and estimated glomerular filtration rate (eGFR) at time of conversion and serially thereafter. The primary endpoint was stabilization or improvement of kidney function as assessed by eGFR at last recorded follow-up compared with eGFR at the time of conversion.

RESULT

After a median (interquartile range) of 3.1 (1.6-4.5) years of follow-up, serum creatinine decreased from 1.9 ± 0.8 to 1.8 ± 0.7 mg/dL (P=0.25) and eGFR increased from 40.8 ± 16.7 to 44.3 ± 20.0 mL/min (P=0.03). During the same time period, 24-hr urinary protein excretion increased from median (interquartile range) of 72 (0-155) to 382 (169-999) mg/day (P=0.0001). Sixty-five (64%) patients achieved the primary endpoint and 37 (36%) experienced deterioration in kidney function. Independent predictors of deterioration of kidney function after SRL conversion were development of proteinuria ≥ 1000 mg/day (odds ratio [OR]: 3.3, confidence interval [CI]: 1.1-9.5 P=0.03), post-LT diabetes (OR: 4.2, CI: 1.6-11.1, P=0.004), and higher eGFR at time of conversion (OR: 1.6, CI: 1.2-2.2, P=0.003).

CONCLUSION

Improvement or stabilization of kidney function occurred in the majority of LT recipients converted to SRL for CNI nephrotoxicity. Proteinuria ≥ 1000 mg/day, post-LT diabetes, and higher baseline eGFR were independent predictors of kidney function loss after SRL conversion.

mTOR inhibitor-associated proteinuria in kidney transplant recipients

The use of mammalian target of rapamycin inhibitor (mTOR-I) after kidney transplantation has been associated with a higher incidence of proteinuria compared with calcineurin inhibitors (CNIs). This review will focus on mTOR-I-associated proteinuria in different settings after kidney transplantation: de novo mTOR-I treatment in combination with CNI, de novo mTOR-I-containing and CNI-free treatment, early conversion from a CNI-based regimen to an mTOR-I-based regimen, and late conversion. Some possible mechanisms of mTOR-I-induced proteinuria will also be reviewed.

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.

The effects of immunosuppressants on vascular function, systemic oxidative stress and inflammation in rats

Immunosuppressants have been associated with increased cardiovascular disease risk. We determined the effects of calcineurin and mammalian target of rapamycin (mTOR) inhibitor administration on endothelial dysfunction and associated inflammation and oxidative stress in adult rats. Cyclosporine A (low and high dose), sirolimus, tacrolimus, everolimus and placebo were administered to 8-week-old male Wistar rats for 10 consecutive days. Aortic vascular endothelial and smooth muscle function were assessed ex vivo in organ baths. Maximal aortic contraction to noradrenaline in sirolimus-treated rats was significantly greater than cyclosporine groups, everolimus and placebo, whereas endothelial-dependent relaxation was significantly impaired with cyclosporine and tacrolimus compared with everolimus. Endothelial-independent relaxation was impaired in tacrolimus-treated rats compared with low dose cyclosporine, everolimus and sirolimus. Sirolimus was associated with a reduction in plasma interleukin (IL)-1β and tumour necrosis factor (TNF)-α and higher levels of catalase and total antioxidant status. In nontransplanted rats, vascular dysfunction was evident following administration of cyclosporine A, sirolimus and tacrolimus, whereas everolimus did not compromise aortic endothelial or smooth muscle function. At the doses administered in this model, the immunosuppressants exerted varying effects on vascular function.

Proliferation signal inhibitors and post-transplant malignancies in heart transplantation: practical clinical management questions

Although malignancy is a major threat to long-term survival of heart transplant (HT) recipients, clear strategies to manage immunosuppression in these patients are lacking. Several lines of evidences support the hypothesis of an anticancer effect of proliferation signal inhibitors (PSIs: mammalian target of rapamycin [mTOR] inhibitors) in HT recipients. This property may arise from PSI's ability to replace immunosuppressive therapies that promote cancer progression, such as calcineurin inhibitors or azathioprine, and/or through their direct biological actions in preventing tumor development and progression. Given the lack of randomized studies specifically exploring these issues in the transplant setting, a collaborative group reviewed current literature and personal clinical experience to reach a consensus aimed to provide practical guidance for the clinical conduct in HT recipients with malignancy, or at high risk of malignancy, with a special focus on advice relevant to potential role of PSIs.

Effects of sirolimus on human mesangial cells

Mesangial cell (MC) proliferation and production of extracellular matrix or loss of MC are both central findings in a number of renal proteinuric diseases. However, the role of MC as components of the glomerular filtration barrier and whether MC alterations induce changes in the glomerular filtration barrier leading to proteinuria are still matters of debate. The effects of Sirolimus (SRL) in proteinuric nephropathies is controversial: some papers have indicated a reduction and others, an increase in proteinuria after sirolimus treatment. Considering the pivotal role of MC in the pathogenesis of many chronic nephropathies, we evaluated the effect of SRL on cultured human MC. We treated primary human MC cultures with SRL, or platelet-derived growth factor (PDGF) or SRL + PDGF, or dimethylsulfoxide, the SRL vehicle, as a control. PDGF was used to activate MC. After 48 hours treatment, MC showed a significant growth increase that was significantly reduced by SRL (P < .01). Apoptosis, determined by the TUNEL assay and flow cytometry, was not modified by the treatments at 24 hours. SRL treatment increased significantly the number of alpha-smooth muscle actin-positive cells compared with controls (P < .05). Cells treated with SRL and SRL + PDGF showed significant changes in morphology with increased mean cell surface, perimeter, and maximum diameter (P < .01) but not protein content. Furthermore, MC treated with SRL showed decreased migration through polycarbonate membranes. The changes induced by SRL may help to explain some of the in vivo effects observed in SRL-treated patients.

Clinical recommendations for the use of everolimus in heart transplantation

Proliferation signal inhibitors (PSIs), everolimus (EVL), and sirolimus are a group of immunosuppressor agents indicated for the prevention of acute rejection in adult heart transplant recipients. Proliferation signal inhibitors have a mechanism of action with both immunosuppressive and antiproliferative effects, representing an especially interesting treatment option for the prevention and management of some specific conditions in heart transplant population, such as graft vasculopathy or malignancies. Proliferation signal inhibitors have been observed to work synergistically with calcineurin inhibitors (CNIs). Data from clinical trials and from the growing clinical experience show that when administered concomitantly with CNIs, PSIs allow significant dose reductions of the latter without loss of efficacy, a fact that has been associated with stabilization or significant improvement in renal function in patients with CNI-induced nephrotoxicity. The purpose of this article was to review the current knowledge of the role of PSIs in heart transplantation to provide recommendations for the proper use of EVL in cardiac transplant recipients, including indications, treatment regimens, monitoring, and management of the adverse events.

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.

Prospects for mTOR inhibitor use in patients with polycystic kidney disease and hamartomatous diseases

Mammalian target of rapamycin (mTOR) is the core component of two complexes, mTORC1 and mTORC2. mTORC1 is inhibited by rapamycin and analogues. mTORC2 is impeded only in some cell types by prolonged exposure to these compounds. mTOR activation is linked to tubular cell proliferation in animal models and human autosomal dominant polycystic kidney disease (ADPKD). mTOR inhibitors impede cell proliferation and cyst growth in polycystic kidney disease (PKD) models. After renal transplantation, two small retrospective studies suggested that mTOR was more effective than calcineurin inhibitor-based immunosuppression in limiting kidney and/or liver enlargement. By inhibiting vascular remodeling, angiogenesis, and fibrogenesis, mTOR inhibitors may attenuate nephroangiosclerosis, cyst growth, and interstitial fibrosis. Thus, they may benefit ADPKD at multiple levels. However, mTOR inhibition is not without risks and side effects, mostly dose-dependent. Under certain conditions, mTOR inhibition interferes with adaptive increases in renal proliferation necessary for recovery from injury. They restrict Akt activation, nitric oxide synthesis, and endothelial cell survival (downstream from mTORC2) and potentially increase the risk for glomerular and peritubular capillary loss, vasospasm, and hypertension. They impair podocyte integrity pathways and may predispose to glomerular injury. Administration of mTOR inhibitors is discontinued because of side effects in up to 40% of transplant recipients. Currently, treatment with mTOR inhibitors should not be recommended to treat ADPKD. Results of ongoing studies must be awaited and patients informed accordingly. If effective, lower dosages than those used to prevent rejection would minimize side effects. Combination therapy with other effective drugs could improve tolerability and results.

Indications, tolerance and complications of a sirolimus and calcineurin inhibitor immunosuppression regimen: intermediate experience in pediatric heart transplantation recipients

Although SRL has been used in adults, few studies are reported in pediatric Htx recipients. Retrospective chart review of all Htx patients on SRL. We evaluated Cr at Htx and years 1, 3, 5, 7, 9, 11, 13, and 15 post-Htx. GFR was calculated (Schwartz). BMI, Hgb, lipid profiles, and complications were compared to 59 controls, and a matched case-control group used to compare GFR to SRL cohort. Twenty-one patients were converted to SRL 1-2 mg/day (target 4-8 ng/mL) and analyzed. Reasons for conversion: re-transplantation/TCAD (8), renal (7), rejection (5), other (1). Cr was higher (p = 0.004) and GFR lower (p = 0.025) in SRL group than controls at Htx. Patients began SRL a median of 3.6 yr (0.1-16.2) post-Htx at 15.2 yr of age (4.4-24.4), with follow-up 0.5-4.6 yr. SRL was well tolerated with no increase in hyperlipidemia, rejection or mortality. None required SRL discontinuation. SRL was well tolerated in pediatric Htx patients. Kidney function remained stable; subjects had no increase in mortality, rejection or PTLD. Multicenter studies using renal sparing protocols are needed to determine whether SRL should be used routinely in children.

Nonalbumin proteinuria in islet transplant recipients

The aim of this study was to evaluate the importance of nonalbumin-predominant proteinuria on kidney function (KF) after islet transplantation (ITx). Twenty-four-hour proteinuria and albuminuria were available in 27 recipients. KF was assessed by serum creatinine and estimated glomerular filtration rate (eGFR) was calculated by Modification of Diet in Renal Disease formula. Correlations between eGFR and albuminuria (r = -0.422, p < 0.001) were higher than with proteinuria (r = -0.223, p < 0.001; p = 0.006 for comparison between correlations). Nineteen (70%) subjects had proteinuria >or= 300 mg/24 h during the follow-up. Subjects were divided into three groups according to urinary protein excretion patterns: no proteinuria (n = 8), nonalbumin-predominant (n = 8), and albumin-predominant (n = 11) proteinuria. Proteinuria >or= 500 mg/24 h was observed only among patients with albumin-predominant proteinuria (64%; p = 0.002) and these patients had the lowest eGFR means post-ITx (no proteinuria: 84.2 +/- 16.4 vs. nonalbumin: 69.1 +/- 13.8 vs. albumin-predominant proteinuria: 65.5 +/- 16.6 ml/min/1.73 m(2), p = 0.044 for first vs. last group). In conclusion, high frequency of proteinuria was observed after ITx. However, it seems to be milder and have less impact on KF when albumin is not the major source of proteinuria. Prospective evaluation of proteinuria, including tubular function markers, should be performed to elucidate the mechanisms of kidney damage in this population.