Histopathology of calcineurin inhibitor-induced nephrotoxicity

Distinct morphological features of acute tubular injury in renal allografts correlate with clinical outcome

Acute tubular injury (ATI) is common in renal allografts and is related to inferior long-term allograft function. However, it is unknown which of the morphological features of ATI can predict outcome and how they should be graded. Here, we examine features of ATI systematically in protocol biopsies and biopsies for cause to define the most predictive features. Analyses included 521 protocol biopsies taken at 6 wk, 3 mo, and 6 mo after transplantation and 141 biopsies for cause from 204 patients. Features of ATI included brush border loss, tubular epithelial lucency, flattening, pyknosis, nuclei loss, and luminal debris, each graded semiquantitatively. Additional immunohistochemical stainings were performed for markers of cell injury (neutrophil gelatinase-associated lipocalin), cell death [cleaved caspase-3, fatty acid-coenzyme A ligase 4 (FACL4)], and proliferation (K_i-67). Interobserver reliability was good for pyknosis, flattening, and brush border loss and poor for lucency, nuclei loss, and luminal debris. In protocol biopsies between 6 wk and 6 mo, the degree of ATI remained virtually unchanged. Biopsies for cause had generally higher injury scores. Deceased donor source, delayed graft function, ganciclovir/valganciclovir treatment, and urinary tract infection correlated with ATI. The degree of pyknosis, flattening, and brush border loss correlated best with impaired allograft function. FACL4 expression was observed in areas of ATI. Only patients with K_i-67 expression showed stable or improved allograft function in the longitudinal assessment. Reliable assessment of ATI is possible by semiquantitative grading of tubular epithelial cell brush border loss, flattening, and pyknosis. Examination of K_i-67 expression can help determine the potential for recovery from this damage.

Calcineurin Inhibitor Nephrotoxicity Through the Lens of Longitudinal Histology: Comparison of Cyclosporine and Tacrolimus Eras

BACKGROUND

The contribution of calcineurin inhibitors (CNI) nephrotoxicity to progressive kidney transplant injury remains debated, with little long-term data from the modern tacrolimus (TAC) era using lower doses.

METHODS

This longitudinal cohort study evaluated histological evidence of CNI nephrotoxicity from normal donor kidneys of successful kidney-pancreas transplant recipients during cyclosporine (CSA) and TAC eras, analyzed by intention-to-treat.

RESULTS

From 200 patients, 1622 adequate prospective protocol (84.3%) and indication (15.7%) kidney biopsies yielded 8.1 ± 4.1 samples per patient, over 7.4 ± 4.4 years posttransplant. The TAC era demonstrated less rejection and reduced early immune-mediated tubular damage, compared with CSA (P < 0.001). The incidences of acute mild arteriolopathy, striped interstitial fibrosis, glomerular congestion, and tubular microcalcification were all greater with CSA (hazard ratios of 1.70, 9.35, and 3.78, respectively) and maximal within the first posttransplant year, compared with TAC-treated patients (P < 0.001). However, the 1-, 5-, and 10-year prevalence moderate arteriolar hyalinosis was similar: CSA was 5.4%, 38.4%, and 79.1%; and TAC was 4.3%, 33.6% and 77.2%, respectively (P = NS). Morphometric measurement demonstrated lumenal narrowing from inwards collapse of hyalinized arteriolar walls unable to maintain its structural integrity. Severe hyalinosis was calculated to reduce arteriolar blood flow to 20 ± 34% of normal. Severity of arteriolar hyalinosis correlated with contemporaneous glomerulosclerosis (r = 0.44, P < 0.001), and subsequent progression in 1356 sequential biopsy pairs, consistent with glomerular ischemia.

CONCLUSIONS

Tacrolimus-based therapy appeared superior to the CSA era, with less early CNI nephrotoxicity and fewer rejection episodes, but comparable chronic arteriolar toxicity. Calcineurin inhibitors are imperfect long-term maintenance immunosuppressive agents because of frequent and irreversible chronic toxicity.

A comparative, randomized trial of concentration-controlled sirolimus combined with reduced-dose tacrolimus or standard-dose tacrolimus in renal allograft recipients

BACKGROUND

The clinical safety and efficacy of sirolimus plus reduced-dose tacrolimus was evaluated in de novo renal allograft recipients enrolled in a comparative, open-label study.

METHODS

One hundred twenty-eight renal allograft recipients were randomly assigned (1:1) to receive reduced-dose tacrolimus plus sirolimus (rTAC) or standard-dose tacrolimus and sirolimus (sTAC) for 6 months. The primary efficacy endpoint was calculated creatinine clearance values at 6 months.

RESULTS

Demographic variables were similar between groups. At 6 months, mean (± standard deviation) calculated creatinine clearance was significantly improved in the rTAC group (63.8 vs 52.7 mL/min, P = .005), although mean serum creatinine values were not significantly different. Patient survival (95.2% and 96.9%) and graft survival (93.7% and 98.5%) were similar between the rTAC and sTAC groups, respectively. Acute rejection rates were 17.5% with rTAC and 7.7% with sTAC (P = .095).

CONCLUSIONS

The rTAC regimen provided effective immunosuppression and was associated with improved creatinine clearance. Adequate immunosuppressant exposure must be achieved in the early postoperative period to minimize the risk of acute rejection.

Empiric switch from calcineurin inhibitor to sirolimus-based immunosuppression in pediatric heart transplantation recipients

Sirolimus is used in heart transplant patients with CAV and CNI-induced nephropathy. However, little is known regarding the tolerability, rejection rate, and effect on renal function when used empirically in children. We describe our experience with the empiric use of a sirolimus-based immunosuppressive regimen in pediatric heart transplantation recipients. We reviewed records of patients in whom conversion was attempted to a CNI-free sirolimus-based regimen. Rejection episodes and measures of renal function were recorded. We attempted to convert 20 patients, of which 16 were successful. In total, six of 20 patients (30%) experienced adverse effects. Of the 16 converted, four patients converted to sirolimus due to CNI-induced disease (three nephropathy, one CAV), while 12 patients (mean age 5.5 yr, range 0.1-21 yr; 33% female; 33% with a history of congenital heart disease) were empirically switched to sirolimus at a mean of 2.3 yr after transplant. Follow-up was available for a mean of 2.5 yr after conversion (range 0.5-8.3 yr). The rate of rejection while taking CNIs was 0.18 rejection episodes per patient-year (total of five episodes), compared with 0.03 rejection episodes per patient-year (total of one episode) while on sirolimus. Renal function, in terms of GFR, significantly improved after sirolimus conversion at latest follow-up (from 86 ± 37 mL/min to 130 ± 49 mL/min, p = 0.02). Here, we demonstrate the potential benefit of empiric use of sirolimus in pediatric heart transplant patients in a CNI-free regimen. Larger and longer studies are needed to further clarify risks of rejection and adverse effect profiles.

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.

Steroid withdrawal and reduction of cyclosporine A under mycophenolate mofetil after heart transplantation

Survival and quality of life after heart transplantation are limited by a significant incidence of cardiovascular complications. Side effects of immunosuppressives contribute unfavorably. Aim of this study was to determine (1) whether withdrawal of corticosteroids and dose reduction of cyclosporine A can be performed safely under immunosuppressive therapy with mycophenolate mofetil and (2) if this is beneficial for renal function and cardiovascular risk reduction. Long term heart transplant recipients on steroids and cyclosporine A were examined in a monocentric, prospective, single-arm cohort study. Steroids were withdrawn, mycophenolate mofetil introduced and cyclosporine A dose reduced (target level 50-90 ng/ml). Follow up was 24 months. 23 patients were analyzed: Renal parameters (creatinine, urea, uric acid) improved significantly (p<0.01), as did cardiovascular parameters (heart rate [p<0.05], systolic and diastolic blood pressure [p<0.01]), HbA1c (p<0.05) and triglycerides (p<0.05). In contrast, the self-percepted state of health (SF36™) decreased. Drop outs occurred mostly due to steroid withdrawal syndrome [n=7]. The incidence of adverse events reflected the usual course after heart transplantation. We conclude that CS free immunosuppression comprising reduced cyclosporine levels and addition of MMF in long term heart transplant recipients is safe and improves the cardiovascular risk profile, carbohydrate metabolism and renal function.

Is there any way to protect from tacrolimus-induced renal and pancreas injury?

BACKGROUND

The aim of this study was to explore effects of erythropoietin and pentoxifylline in tacrolimus-induced pancreatic beta cell and renal injury in rats.

METHODS

Rats in group I were given saline; rats in group II were injected with tacrolimus; rats in group III were received erythropoietin (Epo) and tacrolimus; while rats in group IV were injected pentoxifylline (Ptx) plus tacrolimus for nine d. On 10th day, blood and tissue samples were taken for biochemical and pathological evaluations.

RESULTS

Tacrolimus-injected animals exhibited significant elevation in blood urea nitrogen (BUN), and serum BUN levels were improved in rats pretreated with Ptx. Significantly more apoptotic nuclei were observed in kidneys of tacrolimus group. In rats subjected to tacrolimus and pretreated with Epo, there was significant decrease in apoptotic nuclei staining than those in tacrolimus group. Blood trough levels of tacrolimus were significantly higher in erythropoietin-pretreated group, although same amount of tacrolimus was injected with other groups.

CONCLUSION

Results of our study demonstrated significant antiapoptotic effects of erythropoietin on renal tubules, increasing effect of erythropoietin on tacrolimus blood levels, and insignificant antioxidant effects of both erythropoietin and pentoxifylline on renal and pancreas tissues. Study with clinically greater tacrolimus levels may be useful to confirm these findings.

Long-term kidney allograft function and survival in prednisone-free regimens: tacrolimus/mycophenolate mofetil versus tacrolimus/sirolimus

BACKGROUND AND OBJECTIVES

The optimal maintenance immunosuppressive regimen to improve long-term renal allograft function and graft survival is yet to be determined.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This observational study prospectively compared tacrolimus/sirolimus with tacrolimus/mycophenolate mofetil in renal transplant recipients using a prednisone-free regimen with over 8.5 years of follow-up. Patients received methylprednisonlone and anti-IL2 receptor antagonist (Basiliximab) induction and were blindly randomized to either the tacrolimus/mycophenolate mofetil (n=45) or tacrolimus/sirolimus (n=37) groups. Outcome measures included patient and renal allograft survival, incidence of acute rejection, and estimated GFR.

RESULTS

The tacrolimus/mycophenolate mofetil group compared with the tacrolimus/sirolimus group had overall better renal allograft survival (91% versus 70%, P=0.02); 13 patients (35.1%) in the tacrolimus/sirolimus group and 8 patients (17.8%) in the tacrolimus/mycophenolate mofetil group experienced biopsy-proven acute cellular rejection (P=0.07). By 3 months post-transplant, estimated GFR was significantly lower in the tacrolimus/sirolimus group compared with the tacrolimus/mycophenolate mofetil group (47.7 versus 59.6 ml/min per 1.73 m(2), P=0.0002), and this trend persisted throughout the follow-up period. Also, the slope of decline in the tacrolimus/sirolimus group was significantly steeper than in the tacrolimus/mycophenolate mofetil group.

CONCLUSIONS

This study shows that, in a prednisone-free immunosuppressive regimen, long-term renal graft survival and function are significantly worse in the tacrolimus/sirolimus group than the tacrolimus/mycophenolate mofetil group. The synergistic nephrotoxic effect and higher acute rejection rates in the tacrolimus/sirolimus compared with the tacrolimus/mycophenolate mofetil group adversely affect graft survival.

Preclinical and clinical studies on the induction of renal allograft tolerance through transient mixed chimerism

PURPOSE OF REVIEW

The present review updates the current status of research for induction of tolerance through a mixed chimerism approach in nonhuman primates and humans.

RECENT FINDINGS

Allograft tolerance has been successfully achieved with a nonmyeloablative conditioning regimen and donor bone marrow transplantation in human leukocyte antigen (HLA)-matched and mismatched kidney transplantation. In HLA-matched kidney transplantation, persistent mixed chimerism and renal allograft tolerance has been achieved in some patients. In HLA-mismatched combinations, induction of persistent mixed chimerism has not been achieved using a nonmyeloablative preparative regimen. Nevertheless, the transient mixed chimerism that has been achieved has resulted in long-term renal allograft tolerance in the majority of patients. Recent preclinical studies have demonstrated that the presence of heterologous memory T-cell responses observed in primates, but not in rodents, may be a major barrier for induction of durable chimerism and tolerance in primates. Strategies to overcome such memory T-cell responses may, therefore, be of great value in the development of reliable protocols for clinical tolerance induction.

SUMMARY

Induction of tolerance in clinical kidney transplantation has been achieved via mixed chimerism approaches. Improvements in the consistency and safety of tolerance induction and extension of successful protocols to other organs and to organs from deceased donors will all be among the next steps in bringing tolerance to a wider range of clinical applications.

Tolerability of everolimus-based immunosuppression in maintenance liver transplant recipients

BACKGROUND

The aim of this study was to evaluate the tolerability of the conversion from calcineurin inhibitor (CNI) to everolimus (ERL) in maintenance liver transplant (LT) recipients.

METHODS

From January 2005 to March 2008, ERL was introduced after LT as maintenance immunosuppressive therapy because of (i) de novo or recurrent cancer after LT, (ii) pre-existing liver carcinoma on the liver explant or (iii) CNI toxicity. CNI dosage was progressively reduced until discontinuation.

RESULTS

The study population included 94 patients, of mean age 57 ± 10. The mean delay between LT and ERL introduction was 5 ± 5 yr. After a mean follow-up of 12 ± 7 months, 70% of the patients did present at least one side effect. The mean trough level of ERL was 6 μg/L at the end of follow-up. Main side effects included hyperlipidemia (37%), dermatitis (19%), mucositis (15%), and proteinuria (18%). Biopsy-proven acute rejection occurred in 9% of patients. Global ERL discontinuation rate was 21% (16% because of side effects).

CONCLUSIONS

The results of our experience indicate that conversion to ERL is associated with adverse effects in 70% of patients leading to drug discontinuation in 16% (and amenable to dose reduction in the remainders). Longer follow-up periods are necessary to capture the impact of ERL fully on renal function and survival in cancer patients.

Usefulness of sirolimus as rescue therapy in heart transplant recipients with renal failure: analysis of the Spanish Multicenter Observational Study (RAPACOR)

BACKGROUND

Chronic renal failure is a common complication of heart transplantation. Sirolimus (SRL) is an immunosuppressive drug that, unlike calcineurin inhibitors (CNIs), is not associated with nephrotoxicity.

METHODS

We collected efficacy and safety data from a Spanish registry of heart transplant recipients who were switched from a CNI to SRL due to renal failure. Patients were included if the serum creatinine level before switching was >1.5 mg/dL and/or the estimated creatinine clearance level was below 50 mL/min.

RESULTS

Ninety-seven patients started SRL due to renal impairment. When SRL was started, CNIs were progressively tapered and in some cases withdrawn. Mean baseline creatinine level was 2.5 mg/dL and mean creatinine clearance level was 39 mL/min. Only 1 episode of acute rejection was observed in a patient receiving SRL plus cyclosporine (CsA) but the eventual allograft function remained stable. Compared with baseline, a significant improvement in renal function was observed at 6 months among patients who stopped CNIs before the third month after SRL was started, although not among those who continued taking CNIs. Upon multivariate analysis, no predictors of response were observed. SRL was withdrawn in 18% of patients due to adverse events.

CONCLUSIONS

Switching to SRL was safe in heart allograft recipients, improving renal function among those previously receiving a CNI. Renal function improves if CNIs are withdrawn soon after starting SRL.

Chronic allograft dysfunction: can we use mammalian target of rapamycin inhibitors to replace calcineurin inhibitors to preserve graft function?

PURPOSE OF REVIEW

Graft loss after first year of transplantation can be due to composite of factors that may include immunological and nonimmunological factors. Among the nonimmunological factors, toxicity of immunosuppression drugs, especially calcineurin inhibitor (CNI) toxicity is perhaps the leading cause of graft dysfunction. The most common phenotype associated with progressive graft dysfunction is the development of interstitial fibrosis and tubular atrophy not otherwise specified, a hallmark finding of chronic allograft nephropathy as well as CNI toxicity. Protocol biopsies have demonstrated that histological lesions of CNI toxicity can develop as early as 3 months posttransplantation.

RECENT FINDINGS

Early detection of interstitial fibrosis and tubular atrophy offers the opportunity for replacement of the CNI with mammalian target of rapamycin inhibitors. Early detection of CNI-associated graft damage even before the onset of graft dysfunction is critical to prevent progressive nephron loss. Furthermore, the conversion to sirolimus in patients with advanced graft dysfunction may not be beneficial.

SUMMARY

Until the day transcriptomic assays and high-density microarrays are available routinely to detect the incipient graft injury, early allograft biopsy, preferably during the first 3-6 months of transplantation can detect the presence of interstitial fibrosis and tubular atrophy not otherwise specified before the onset of graft dysfunction and replacement of CNI with sirolimus could prevent the progressive nephron loss.

Pathogenesis and management of chronic allograft nephropathy

Chronic allograft nephropathy (CAN) is a common cause of late kidney transplant failure, characterized by progressive histological damage in the allograft. Although functional biomarkers such as creatinine are typically used to predict CAN, recent evidence suggests that composite, quantitative histological indices may be better predictors of long-term graft outcomes. Calcineurin inhibitors (CNIs) have been associated with major improvements in early rejection outcomes, but appear to cause both acute and chronic nephrotoxicity. The acute phase is associated with functional nephrotoxicity and is reversible with a reduction in CNI dosage, whereas the chronic phase is characterized by persistent histological lesions that are typically irreversible. Results from recent clinical trials suggest that converting from a CNI to sirolimus, withdrawing a CNI from a sirolimus-based regimen or using a CNI-free strategy may improve long-term outcomes by reducing CNI-related nephrotoxicity. However, in the de novo transplant setting, triple therapy with sirolimus, mycophenolate mofetil and corticosteroids is not recommended in combination with basiliximab induction. A treatment algorithm, based on the patient's histological score obtained on an allograft biopsy taken at approximately 6-12 months post-transplant, has been developed by our group and is described here.

Sirolimus in liver transplant recipients with renal dysfunction offers no advantage over low-dose calcineurin inhibitor regimens

The purpose of this study is to review the clinical experience with sirolimus immunosuppression in liver transplant patients with calcineurin inhibitor-induced chronic renal insufficiency. The study design is a case-control retrospective series. Fifty-seven liver transplant patients with renal insufficiency that were started on sirolimus at greater than 90 days postoperatively and treated for more than 90 days were identified. A control group of 57 patients maintained on low-dose calcineurin inhibitors, matched for gender, year of transplant, and baseline creatinine clearance, was also identified. There were no significant differences in the absolute creatinine clearance values between the sirolimus and control groups from 6 months before sirolimus conversion to 12 months after sirolimus conversion. Patients exposed to calcineurin inhibitors for more than 5 years or those with an initial creatinine clearance of less than 30 mL/minute who were converted to sirolimus did worse than control patients maintained on low-dose calcineurin inhibitors. Progression to renal replacement therapy, episodes of acute and chronic rejection, and death were similar between the sirolimus and control groups. The overall prevalence of side effects was significantly higher in the sirolimus group compared with the control group, although these were generally tolerable in most patients. In conclusion, this study suggests that conversion to sirolimus in liver transplant patients with chronic renal insufficiency is associated with stabilization of renal function but confers no additional benefit to low-dose calcineurin inhibitor regimens and may in fact be disadvantageous in patients with a creatinine clearance of less than 30 mL/minute.

Replacement of Calcineurin-Inhibitors With Sirolimus as Primary Immunosuppression in Stable Cardiac Transplant Recipients

BACKGROUND

Calcineurin-inhibitor (CNI) nephrotoxicity is a major cause of morbidity and mortality after cardiac transplantation. The aim of this study was to assess over 2 years the safety and effect on renal function of withdrawal of CNI immunosuppression and replacement with sirolimus (SRL) in stable cardiac transplant recipients.

METHODS

CNI was substituted with SRL in 78 cardiac transplant recipients (SRL group) of whom 58 (group A) had CNI-induced renal impairment (glomerular filtration rate [GFR] <50 mL/min) and 20 (group B) had preserved renal function (GFR >50 mL/min). Fifty-one patients (CNI group) with renal impairment (GFR < or =50 mL/min) maintained on CNI served as controls. Secondary immunosuppressants were unchanged.

RESULTS

In the SRL group, GFR increased from 47.0+/-18.0 to 61.2+/-22.2 ml/min (P=0.0001) 24 months after SRL initiation. In Group A, GFR increased from 40.5+/-12.7 to 53.9+/-19.8 mL/min (P<0.0001). In Group B, GFR increased marginally from 67.2+/-15.8 to 83.5+/-27.8 mL/min (P=0.10). In the CNI group, GFR declined from 40.5+/-14.0 mL/min to 36.4+/-12.5 mL/min (P=0.23) after 24 months of follow up. There was no significant difference in cardiac rejection or cardiac allograft function. In SRL group, proteinuria increased from 299+/-622 mg/day to 517+/-795 mg/day (P=0.0002) 12 months after SRL initiation and then stabilized; it did not differ from CNI group at 24 months (637+/-806 vs. 514+/-744 mg/day, P=0.39). Uric acid decreased from 7.6+/-2.4 to 6.2+/-1.9 mg/dL (P=0.0007) in the SRL group.

CONCLUSIONS

Graduated substitution of CNI with SRL in cardiac transplant recipients is safe and improves renal function, without cardiac compromise.

The Effect of FK778 on the Progression of Chronic Allograft Nephropathy in a Rat Model

BACKGROUND

Chronic allograft nephropathy (CAN) still belongs to the leading causes of graft loss over the long term. The leflunomide derivative FK778 is a novel immunosuppressant with improved pharmacokinetic properties that effectively prolonged graft survival in several transplantation models. In the present study, we investigated the effects of FK778 at different phases after transplantation on the progression of CAN.

METHODS

Fisher 344 kidneys were orthotopically transplanted into Lewis recipients. Recipients were treated with FK778 (5 mg/kg/day) over different time periods (early: days 0-10 only, continuous: day 0 to week 24, or late: weeks 16-24 only posttransplantation). Proteinuria was measured every 4 weeks, whereas grafts were harvested at 24 weeks posttransplantation for morphological and immunohistochemical analysis as well as transforming growth factor-beta and platelet derived growth factor-B chain expression.

RESULTS

Continuous treatment with FK778 ameliorated the progression of CAN, whereas late treatment reduced proteinuria and resulted in a similar grade of CAN as compared to animals with continuous treatment. In contrast, FK778 given only during the early phase after transplantation had no effect on the progression of CAN as compared to controls.

CONCLUSION

In summary, FK778 is a potent immunosuppressive drug that can delay the progression of CAN, even when given at later stages after transplantation.

Long-term renal allograft function on a tacrolimus-based, pred-free maintenance immunosuppression comparing sirolimus vs. MMF

It is not known how different steroid-free immunosuppressive combinations affect renal graft survival and long-term kidney transplant function. Here we sought to compare the impact on graft survival and long-term graft function of two tacrolimus (Tac)-based, prednisone-free maintenance immunosuppressive protocols: Tac/Mycophenolate Mofetil (MMF) vs. Tac/Sirolimus (SRL). Renal transplant patients given induction therapy with IL2-RA and methylprednisolone on days 0, 1 and 2 post-transplant were prospectively randomized to two maintenance immunosuppressive regimens with Tac/MMF (n = 45) or Tac/SRL (n = 37). During the 3-year follow-up the following data were collected: patient survival, renal allograft survival, incidence of acute rejection and glomerular filtration rate (GFR) at different time-points post-transplant. Cumulative graft survival was significantly different in the two groups: one kidney loss in the Tac/MMF vs. six kidney losses in the Tac/SRL (log-rank test p = 0.04). GFR at different time-points post-transplant was consistently and statistically better in the Tac/MMF than in the Tac/SRL group. The slope of GFR decline per month was flatter in the Tac/MMF than in the Tac/SRL group. This study showed that renal graft survival and graft function were significantly lower in the combination of Tac/SRL than Tac/MMF.

Cyclosporine A induces vascular fibrosis and heat shock protein expression in rat

The immunosuppressive drug Cyclosporine A (CsA) has been successfully used in several diseases with immunological basis and in transplant patients. However, the therapeutic treatment induces several side effects, which include the development of severe hypertension, renal failure and cardiotoxicity in the majority of the patients. Since the mechanism by which CsA induces hypertension is not well defined, the aim of this study is to evaluate the morphological changes and the expression of heat shock proteins (HSPs) in the thoracic aorta of CsA-treated rats. The study was carried out on 40 male Wistar rats with an average weight of 200-250 g. The animals were divided into four groups. Groups I and II were injected subcutaneously (sc) daily with castor oil for 15 or 30 days and used as control; group III and IV were injected sc daily with CsA (15 mg/Kg/day) for 15 or 30 days. After the end of the treatment, the thoracic aortae were removed and treated for morphological (Sirius Red) and immunohistochemical evaluation (HSP 25, alphaB-crystallin and HSP 47). The results indicate that CsA induces (1) time-dependent vascular damage visible as fibrosis mainly in intima-media tunica of aorta, and (2) a clear increase in HSP expression. In fact, after 30 days of treatment, HSP and alphaB-crystallin are increased in all tunicas, whereas HSP47 only in tunica media and adventitia. These findings could suggest that these proteins are up-regulated after CsA treatment in order to play a defensive role in vascular damage.

Thiopurine S-methyltransferase genotype predicts azathioprine-induced myelotoxicity in kidney transplant recipients

Azathioprine (AZA) is an immunosuppressive prodrug that undergoes metabolism by thiopurine S-methyltransferase (TPMT). Eighty to ninety-five percent of low or deficient TPMT enzyme activity is genetically determined by the presence of three nonfunctional mutant alleles: TPMT*2, TPMT*3A and TPMT*3C. Using TPMT as a pharmacogenetic paradigm, we explored the association between these genetic mutations and development of adverse drug effects in an ethnically diverse renal transplant population receiving azathioprine. Biochemical and clinical data were retrospectively evaluated during the first four weeks after kidney transplantation. TPMT nonfunctional mutant alleles were identified by polymerase chain reaction-based methods. Of 89 patients initially consented, 36 met inclusion criteria for this retrospective study. Five patients possessing a single TPMT nonfunctional mutant allele were identified: TPMT*3A: n = 2 Caucasians; TPMT*3B: n = 1 Caucasian; TPMT*3C: n = 2 African-Americans. TPMT nonfunctional mutant alleles were associated with significant reductions in hematological indices and a significant increase in cyclosporine plasma concentrations in the first month post-transplant. TPMT genotype was an independent predictor for hemoglobin, hematocrit and red blood cell changes while mean azathioprine dose (mg/kg/day), azathioprine dose (mg/kg/day) at day 30 and cyclosporinemia at day 30 were not. Prospective application of pharmacogenetic principles may assist in optimization of immunosuppressive drug therapy and minimize drug toxicities.

Cyclosporine renal dysfunction

Cyclosporine (CsA), introduced as an immunosuppressive agent in the 1980s, quickly become the first-line treatment in organ transplantation. However, these improvements were associated with an increased incidence of renal dysfunction. CsA causes histopathological changes in renal transplants that are often difficult to distinguish from other processes, especially chronic allograft nephropathy. Enhanced angiotensin II, transforming growth factor-beta, and vascular endothelial growth factor expression together with down-regulation of nitric oxide synthesis may play roles in chronic CsA nephropathy. Efforts have recently focused upon protocols that minimize the risk of CsA nephrotoxicity while preserving low rates of acute rejection. Four types of CsA-sparing studies have emerged from recent clinical experience: (1) conversion studies in which a nonnephrotoxic drug is substituted to allow CsA reduction, (2) minimal CsA exposure studies in which reduced CsA doses are combined with nonnephrotoxic drugs, (3) withdrawal studies in which CsA is completely discontinued at some time after transplantation, and (4) CsA-free studies in which the drug is completely avoided from the time of transplantation. Monitoring of CsA immunosuppression according to C2 blood levels, which better correlate with the area under the time-concentration curve than trough concentrations, should reduce the risk for toxicity; however, the most appropriate target range has not yet been clearly established. Because of interindividual differences in CsA absorption and susceptibility to renal dysfunction, the current therapeutic drug monitoring should be supplemented with pharmacogenetic information on genetic variability of relevant genes for pharmacokinetic parameters and therapeutic targets. This approach may guide choices for immunosuppressants for particular patients, with low toxicity. Thus, despite of 20 years of its history, CsA renal dysfunction remains an important clinical challenge.

Strategies for ensuring effective surveillance in post-transplant patients: practical organization and clinical evaluation

Results of renal transplantation have improved steadily over the years. This article reviews the current status of patient and graft survival and discusses major causes of mortality and renal allograft failure. Review of recent literature demonstrates that the traditional enemies of transplantation, acute rejection and opportunistic infections are no longer major problems facing transplantation. Chronic graft nephropathy and death with functioning graft due to cardiovascular disease are the main challenges in the current era. An impact of an early graft thrombosis, recurrent renal disease and post-transplant malignancies are also reviewed. Chronic graft nephropathy is examined in a context of differences between two calcineurin inhibitors, cyclosporin microemulsion and tacrolimus. Strategies of post-transplant surveillance are suggested.

The natural history of chronic allograft nephropathy

BACKGROUND

With improved immunosuppression and early allograft survival, chronic allograft nephropathy has become the dominant cause of kidney-transplant failure.

METHODS

We evaluated the natural history of chronic allograft nephropathy in a prospective study of 120 recipients with type 1 diabetes, all but 1 of whom had received kidney-pancreas transplants. We obtained 961 kidney-transplant-biopsy specimens taken regularly from the time of transplantation to 10 years thereafter.

RESULTS

Two distinctive phases of injury were evident as chronic allograft nephropathy evolved. An initial phase of early tubulointerstitial damage from ischemic injury (P<0.05), prior severe rejection (P<0.01), and subclinical rejection (P<0.01) predicted mild disease by one year, which was present in 94.2 percent of patients. Early subclinical rejection was common (affecting 45.7 percent of biopsy specimens at three months), and the risk was increased by the occurrence of a prior episode of severe rejection and reduced by tacrolimus and mycophenolate therapy (both P<0.05) and gradually abated after one year. Both subclinical rejection and chronic rejection were associated with increased tubulointerstitial damage (P<0.01). Beyond one year, a later phase of chronic allograft nephropathy was characterized by microvascular and glomerular injury. Chronic rejection (defined as persistent subclinical rejection for two years or longer) was uncommon (5.8 percent). Progressive high-grade arteriolar hyalinosis with luminal narrowing, increasing glomerulosclerosis, and additional tubulointerstitial damage was accompanied by the use of calcineurin inhibitors. Nephrotoxicity, implicated in late ongoing injury, was almost universal at 10 years, even in grafts with excellent early histologic findings. By 10 years, severe chronic allograft nephropathy was present in 58.4 percent of patients, with sclerosis in 37.3 percent of glomeruli. Tubulointerstitial and glomerular damage, once established, was irreversible, resulting in declining renal function and graft failure.

CONCLUSIONS

Chronic allograft nephropathy represents cumulative and incremental damage to nephrons from time-dependent immunologic and nonimmunologic causes.

Gingival overgrowth in kidney transplant recipients treated with cyclosporine and its relationship with chronic graft nephropathy

Our previous study of a group of renal transplant recipients treated with CsA showed a significantly faster development of chronic graft failure among patients with gingival hyperplasia (GH) compared to unaffected patients. The aim of the present research was to establish the impact of CsA dose and blood levels on the incidence of chronic graft nephropathy and gingival overgrowth as well as to assess risk factors for chronic graft nephropathy. The study included 64 renal graft recipients (32 patients with GH and 32 without GH) transplanted between 1989 and 1994. There were no significant differences between the pretransplant demographic and clinical data of the patients with and without GH. Patients with GH received a significantly higher total yearly dosages of CsA compared those without GH (P <.03). Serum creatinine in the first year posttransplant in patients with GH was 1.9 mg/dL versus 1.6 mg/dL in those without GH. During 9 to 14 years follow-up, end-stage renal failure due to chronic nephropathy occurred in 18 patients (56%) with GH and eight patients (25%) without GH. Ten-year renal graft survival was 35% in GH patients and 69% in patients without GH. Ten-year patient survival was 69% in the GH group and 91% in the group without GH. CsA dosage was a risk factor for GH and for graft loss, which implies a role of CsA toxic effects on the pathological mechanisms of GH and of chronic allograft nephropathy.

Long-term mycophenolate mofetil monotherapy in combination with calcineurin inhibitors for chronic renal dysfunction after liver transplantation

BACKGROUND

Calcineurin inhibitors (CNIs) are the first-line immunosuppressive agents administered after liver transplantation, but they cause renal impairment. Two recent randomized trials report cellular rejection and liver graft loss when mycophenolate mofetil (MMF) monotherapy was used as a renal-sparing agent. Our experience with MMF in the same setting but with longer follow-up is described.

METHODS

In 45 patients with serum creatinine more than 120 micromol/L or creatinine clearance less than 50 mL/min, 2 g MMF per day was administered (median 29 months, 1-49 months) either as monotherapy (with all other immunosuppression withdrawn in 1 month) in 16 patients (group I) or in combination with low-dose CNI (trough tacrolimus </=5 ng/mL, cyclosporin A </=50 ng/mL) in 29 patients (18 patients without [group II] and 11 patients with [group III] previous refractory rejection [rejection after two episodes of treated rejection]).

RESULTS

In group I (median interval receiving MMF, 33 months), only one patient (6%) experienced cellular rejection, and serum creatinine normalized in five of eight patients long term. In group II (median follow-up 26.5 months), none of 18 experienced rejection, and serum creatinine normalized in 6 of 10 long term. In group III (median follow-up 34 months), 5 of 11 patients (45%) experienced further rejection, one was not steroid responsive, and serum creatinine normalized in four of eight patients long term. There was no graft loss or death as a result of rejection.

CONCLUSIONS

Our cohort with prolonged follow-up showed significant improvement in renal function with both MMF monotherapy and in combination with low-dose CNI with minimal rejection (five of six steroid responsive) and no graft loss. MMF substitution is a therapeutic strategy that deserves more extensive use in liver transplantation.

Role of endogenous vascular endothelial growth factor in tubular cell protection against acute cyclosporine toxicity

BACKGROUND

Recent studies have shown that exogenous administration of vascular endothelial growth factor (VEGF) is protective against cyclosporine A (CsA) renal toxicity. No data are available, however, on the possible role of endogenous VEGF. Our objective was to examine whether endogenous VEGF has a significant role in the renal response against CsA toxicity.

METHODS

In vivo, we used high-dose (50-150 mg/kg/day) CsA +/- specific goat anti-mouse VEGF blocking monoclonal antibody (alpha-VEGF) in mice. In vitro, we exposed mouse tubular cells (MCT) to CsA +/- alpha-VEGF.

RESULTS

alpha-VEGF markedly enhanced CsA renal toxicity, inducing severe tubular damage and increased blood urea nitrogen. In animals treated with CsA + alpha-VEGF, damage progressed to generalized tubular injury (histology) and apoptosis (terminal deoxynucleotide transferase-mediated dUTP nick-end labeling) with associated anemia and reticulocytosis (18 days of treatment). CsA + alpha-VEGF treatments strikingly increased tubular VEGF and Bcl-xL proteins. In vitro, autocrine production of VEGF by MCT was identified by Western blot. Of specific interest, CsA toxicity in MCT increased significantly in the presence of alpha-VEGF.

CONCLUSIONS

Endogenous VEGF has a relevant role in the renal tubular defense against CsA toxicity. Blockade of the VEGF effect by alpha-VEGF results in clear-cut intensification of the tubular injury and appearance of regenerative anemia in the CsA + alpha-VEGF-treated animals. The occurrence of both in vivo and in vitro effects of VEGF blockade provides evidence of a direct protective effect of VEGF on the tubular cell.

The effect of two different cyclosporine formulations on the long-term progression to chronic rejection in renal allograft recipients

INTRODUCTION

The introduction of the microemulsion formulation of cyclosporine (CsA) (Neoral-NEO) has been shown to provide improved absorption and less intrapatient variability than the previous formulation (Sandimmune-SIM) in kidney transplant recipients. It has been suggested that the use of the microemulsion formulation results in less acute rejection, and therefore permits better long-term transplant outcomes. Our aim was to determine whether the microemulsion formulation of cyclosporine has reduced the long-term (5 yr or more) rates of chronic rejection (allograft nephropathy) in a renal transplant population.

METHODS

The study population included 792 (508 cadaveric and 284 living donor) transplants performed in 786 patients at the Cleveland Clinic Foundation and its affiliate hospitals between July 1, 1987 and July 1, 1998. Patients who were less than 18-yr-old or had less than 12 months of graft function were excluded from the analysis. Over 90% of the cadaveric and 11% of the live donor recipients were given an induction antibody. A total of 591 patients were given the SIM formulation and 201 the NEO formulation of cyclosporine. Additional maintenance therapy included either azathioprine or mycophenolate mofetil, and steroids. All patients were followed to graft loss, death, or return to dialysis. The NEO group was followed until December 2001. The diagnosis of acute rejection was biopsy confirmed in >92% of cases. Chronic rejection was identified by clinical and biopsy criteria. Demographic and clinical data was collected from medical records, interviews, and phone contact with patients and treating physicians.

RESULTS

The mean follow-up was 84 +/- 31 months for the SIM group, and 54 +/- 14 months for the NEO group. At 70 months there was no significant difference (p = 0.17) - actuarial patient survival between the SIM (90.7%) vs. the NEO (93%) treated patients. In addition, at 70 months there was no significant difference (p = 0.55) in death censored actuarial graft survival between the SIM (84.3%) and the NEO treated (85.7%) patients. The acute rejection-free rate was 10% higher for the NEO vs. the SIM patients (79 vs. 69%, p = 0.0004). Chronic rejection was diagnosed in 141 of 591 (24%) of the SIM patients and in 56 of 201 (28%) of the NEO patients (p = ns). At 5 yr the mean serum creatinine (mg/dL) was 2.07 +/- 1.69 for the SIM and 2.15 +/- 1.61 for the NEO patients (p = ns).

CONCLUSIONS

The use of the microemulsion formulation of CsA has led to the improved delivery of the parent drug, and a decrease in the number of acute rejection episodes post-transplant. However, patient and graft survival, renal function, and progression to chronic allograft nephropathy at 5 yr were no different. The advantages of greater drug exposure from the microemulsion formulation may be counterbalanced by increased drug induced nephrotoxicity over time.

Calcineurin inhibitor nephrotoxicity: reduction in dose results in marked improvement in renal function in patients with coexisting chronic allograft nephropathy

BACKGROUND

Calcineurin inhibitors (CNI) have significantly reduced the incidence of acute rejection. Nephrotoxicity however, may contribute to long-term allograft dysfunction.

METHODS

Forty-six biopsies from patients who had been transplanted for more than 6 months were examined. Sixteen biopsies had evidence of chronic allograft nephropathy (CAN) alone, 21 biopsies had evidence of coexisting CAN in addition to histological evidence of calcineurin inhibitor nephrotoxicity (CNIN) while nine had neither evidence of nephrotoxicity nor CAN. Patients with evidence of nephrotoxicity underwent a reduction in dose of CNI while those with CAN alone had no change in therapy. Renal function was followed for a mean of 17.4 months after biopsy.

RESULTS

The serum creatinine at the time of diagnostic renal biopsy was comparable between those with CAN alone (mean 0.25 +/- 0.18 mmol/L) and those with coexisting CNIN (mean 0.23 +/- 0.05 mmol/L, p=0.33). The patients with CNIN however, had a rapid improvement in renal function within 1 month after dose reduction. This was sustained for the duration of follow-up (mean serum creatinine 0.162 +/- 0.038 mmol/L at 1 yr after dose reduction; p=0.001). In comparison, those with CAN alone had a gradual decline in renal function with a serum creatinine at 1 yr after biopsy of 0.31 +/- 0.187, p=0.01.

CONCLUSION

Reduction in the dose of CNI in those with histological evidence of nephrotoxicity resulted in a sustained improvement in renal function.