Cyclosporin A Alters Expression of Renal MicroRNAs: New Insights Into Calcineurin Inhibitor Nephrotoxicity

Background Calcineurin inhibitors are powerful immunosuppressants that revolutionized organ transplantation. However, non‐immune effects of the calcineurin inhibitor, cyclosporin A (CsA), have significantly hindered their use. Specifically, nephrotoxicity, which is associated with tubulointerstitial fibrosis, inflammation, and podocyte damage, affects up to half of all transplant patients. Calcineurin is involved in many aspects of kidney development and function. Therefore, mechanisms of CsA‐induced nephrotoxicity are complex and not yet fully understood. MicroRNAs (miRs) are short non‐coding RNAs that regulate protein‐coding RNA expression through post‐translational repression of target messenger RNAs (mRNAs). MicroRNA dysregulation is known to be involved in kidney diseases including fibrosis. Objective This study investigates the microRNA expression changes induced by cyclosporin A. Methods and Results We compared the renal microRNA expression profiles between mice that received CsA (20mg/kg) or vehicle daily for 6 weeks. The results demonstrated that CsA induced significant changes in renal microRNA expression. We used combined criteria of False Discovery Rate (≤0.1), fold change (≥2) and median signal strength (≥50) and identified 76 expression level significantly changed microRNAs. This approach identified microRNAs previously linked to renal fibrosis including let‐7d, miR21, miR29, miR30, miR130, miR192, and miR200 as well as microRNAs that have not been reported to be related to nephrotoxicity or immunosuppression. Pathway analysis of microRNA/mRNA changes highlighted the Wnt, TGF‐β, mTOR, and VEGF pathways. The mRNA expression profiles were compared in the same samples. The change of mRNA and microRNA profiles showed close correlations. To validate that the observed microRNA and mRNA expression level changes in mice kidney tissue were directly related to CsA treatment, the expression of three microRNAs (miR21, miR186, and miR709) and three mRNAs (bmpr1a, smurf1 and smad 7) were compared in the HEK293 cell line. A similar trend of expression level change was induced by CsA treatment in all selected microRNAs and mRNAs in the in vitro cell model. These data provide a roadmap for future work to study the role of the known and novel candidate microRNAs in the mechanism of nephrotoxicity and future therapeutic potential. Conclusions Our study profiled expression of microRNA and mRNA genes in mouse kidney after kidney fibrosis has been induced (the major sign of kidney toxicity) and compared the pairwise expression profiles. The results indicate that CsA induces an extensive change in both microRNA and mRNA gene expressions compared to control mice. In addition, the microRNA and mRNA profiling results show a close correlation. Support or Funding Information NIH1R15M113120‐01