Kidney Disease After Nonkidney Solid Organ Transplant

Nonkidney solid organ transplants (NKSOTs) are increasing in the United States with improving long-term allograft and patient survival. CKD is prevalent in patients with NKSOT and is associated with increased morbidity and mortality especially in those who progress to end-stage kidney disease. Calcineurin inhibitor nephrotoxicity is a main contributor to CKD after NKSOT, but other factors in the pretransplant, peritransplant, and post-transplant period can predispose to progressive kidney dysfunction. The management of CKD after NKSOT generally follows society guidelines for native kidney disease. Kidney-protective and calcineurin inhibitor-sparing immunosuppression has been explored in this population and warrants a discussion with transplant teams. Kidney transplantation in NKSOT recipients remains the kidney replacement therapy of choice for suitable candidates, as it provides a survival benefit over remaining on dialysis.

Clinicopathological Analysis of Medullary Ray Injury in 1-Year Protocol Paediatric Renal Allograft Biopsies

AIM

Medullary ray injury was recently reported in renal transplant biopsies. This study was performed to clarify the clinicopathological features of medullary ray injury in paediatric living renal transplant recipients.

METHODS

Paediatric recipients who completed a 5-year follow-up after living renal transplantation were enroled. We evaluated the clinical and pathological parameters of the presence or absence of medullary ray injury in their 1-year protocol biopsies.

RESULTS

Of 48 1-year protocol biopsies, 18 (37.5%) showed histological evidence of medullary ray injury. The 48 paediatric recipients were classified as those with medullary ray injury (n = 18; MRI-1Y [+] group) and those without medullary ray injury (n = 30; MRI-1Y [-] group) in the 1-year protocol biopsies. The prevalence of histological evidence of calcineurin inhibitor (CNI) nephrotoxicity, chronic obstruction or reflux nephropathy, and imaging findings of vesicoureteral reflux was 66.7, 22.2, and 7.7% in the MRI-1Y (+) group and 33.3, 13.3, and 15.4% in the MRI-1Y (-) group, respectively. Only the prevalence of CNI nephrotoxicity was significantly different between the 2 groups. There was no significant difference in the mean estimated glomerular filtration rate at 1, 3, or 5 years after transplantation between the 2 groups.

CONCLUSION

In total, 37.5% of 1-year protocol biopsies showed histological evidence of medullary ray injury. This finding suggests that CNI nephrotoxicity might be the main contributor to medullary ray injury in 1-year protocol biopsies. The presence of medullary ray injury had little influence on renal function, at least during the first 5 years after transplantation.

The Cytochrome P450 3A5 Non-Expressor Kidney Allograft as a Risk Factor for Calcineurin Inhibitor Nephrotoxicity

BACKGROUND

Tacrolimus is mainly metabolized by cytochrome P450 3A5 (CYP3A5), which is expressed in the liver. However, CYP3A5 is also expressed in the kidney tissue and may contribute to local tacrolimus clearance in the kidney allograft. We aimed to evaluate the association between the allograft CYP3A5 genotype and transplant outcomes.

METHODS

We conducted a retrospective cohort study at the King Chulalongkorn Memorial Hospital, Thailand, comparing 2 groups of donor and recipient CYP3A5 genotypes, the expressor (*1/*1 and *1/*3) and the non-expressor (*3/*3). The primary outcomes were allograft complications including calcineurin inhibitor (CNI) nephrotoxicity and acute rejection episode.

RESULTS

Of the 50 enrolled patients, 21 donors were expressors and 29 donors were the non-expressors. Tacrolimus trough concentrations were similar between the 2 genotypes. The incidence of CNI nephrotoxicity was higher in recipients with non-expressor donor genotype compared with the expressor donor genotype (72.4 vs. 33.3%, p = 0.006). CNI nephrotoxicity incidence was not different when recipient's genotypes were compared. Multivariate analysis from Cox-regression showed a hazard ratio of 3.18 (p = 0.026) for CNI nephrotoxicity in the non-expressor compared with the expressor donor. The recipient CYP3A5 genotypes did not significantly contribute to CNI nephrotoxicity. Kaplan-Meier analysis demonstrated the lowest CNI nephrotoxicity-free survival in recipients with the expressor genotype who received allograft from the non-expressor donors (p = 0.005).

CONCLUSION

In conclusion, our results suggest that donor CYP3A5 non-expressor genotype (*3/*3) is a risk for CNI nephrotoxicity.

Successful treatment of recurrent immunoglobulin a nephropathy using steroid pulse therapy plus tonsillectomy 10 years after kidney transplantation: a case presentation

Background

Both prevention and treatment of recurrent immunoglobulin A nephropathy (IgAN) in kidney transplant recipients are important since recurrent IgAN seems to affect long-term graft survival. We present here a case of recurrent IgAN that was successfully treated using steroid pulse therapy plus tonsillectomy 10 years after kidney transplantation.

Case presentation

A 46-year-old male was admitted for an episode biopsy with a serum creatinine level of 1.8 mg/dl and proteinuria (0.7 g/day). Histological features showed recurrent IgAN (only focal segmental mesangial proliferation) and severe arteriolar hyalinosis partly associated with calcineurin inhibitor toxicity, with limited interstitial fibrosis and tubular atrophy (5%) (IF/TA) 8 years after transplantation. Sodium restriction and conversion from cyclosporine to tacrolimus successfully reduced his proteinuria to the level of 0.15 g/day. However, 2 years later, his proteinuria increased again (1.0 g/day) and a second episode biopsy showed global mesangial proliferation with glomerular endocapillary and extracapillary proliferation accompanied by progressive IF/TA (20%). The steroid pulse therapy plus tonsillectomy successfully decreased his proteinuria and he achieved clinical remission 3 years after this treatment.

Conclusion

This case, presented with a review of relevant literature, demonstrates the difficulty and importance of the treatment of recurrent IgAN and calcineurin inhibitor arteriolopathy, especially in long-term kidney allograft management.

Graft versus host disease-dependent renal dysfunction after hematopoietic stem cell transplantation

Nephropathy is an important complication in hematopoietic stem cell transplantation (HSCT) wherein multifactorial causes, i.e., radiation, drug toxicity, graft versus host disease (GVHD), are thought to contribute renal dysfunction. Here, we report a 10-year-old boy with high-risk acute myelocytic leukemia and severe but partially reversible renal dysfunction. The patient initially received umbilical cord blood transplantation (UCBT) with CY 120 mg/kg and kidney unshielded 12 Gy of total body irradiation. After the leukemic relapse, he received allogenic bone marrow transplantation (BMT) 270 days after the first transplantation. Two months later, his renal function started to deteriorate and urinary protein increased gradually to 1 g/day. Four months after BMT, by the symptoms of severe GVHD, the dose of tacrolimus, utilized to avoid GVHD, was increased although his serum Cre level elevated to 2.97 mg/dL. Serum Cre level improved to 2.0 mg/dL paralleled with GVHD improvement. Renal histological findings showed severe interstitial edema, features of thrombotic microangiopathy (TMA), and C4d deposition along the glomerular capillaries and peritubular capillaries. We suggested that control of GVHD had benefitted to ameliorate renal function of the patient. Treatment for GVHD improved renal dysfunction and TMA of our patients. Moreover, renal biopsy was powerful to elucidate the exact origin of renal dysfunction after HSCT.

Transcriptional profiling of belatacept and calcineurin inhibitor therapy in renal allograft recipients

Calcineurin inhibitor (CNI) use may lead to allograft injury and compromised renal function. Gene expression profiles of 12-month kidney biopsies from a Phase 3 study of belatacept and a CNI comparator, cyclosporine (CsA), were compared with expression profiles of a set of historical, demographically matched, preimplantation control biopsies. Gene set enrichment analysis was used to test each set of differentially expressed genes (DEGs) for the enrichment of an in vitro-derived CNI toxicity (CNIT) gene set and published gene sets associated with chronic allograft injury (CAI), immune modulation and tissue remodeling. The unique set of genes differentially expressed in CNI biopsies compared with preimplantation controls was enriched for genes associated with fibrosis, early tubulointerstitial damage and in vitro CNIT. The DEGs from belatacept biopsies were not enriched for the CNIT genes but, instead, exhibited enrichment for gene sets associated with immune response and tissue remodeling. A combined analysis of DEGs across both treatment groups identified select solute transporter and cellular differentiation genes whose expression at 12 months correlated with renal function at 36 months. These results provide mechanistic insights into the reduced CAI and higher renal function observed in belatacept- versus CsA-treated patients.