Tissue miRNA profile is associated with acute tubular necrosis, rejection phenotypes and BK polyomavirus-associated nephropathy in human kidney allografts

MicroRNAs, short noncoding RNAs, are involved in the modulation of gene expression, mainly by inhibiting the translation of mRNAs. Under physiological conditions, miRNAs are involved in viral infections and immune responses, among others; aberrant miRNA expression has been associated with kidney transplant pathologies, but a comprehensive comparison of later, particularly in tissue sections, is still pending.We used the genome-wide screening of miRNAs to identify those potentially involved in the disease processes after kidney transplantation. RNA was isolated from formalin-fixed paraffin- embedded kidney biopsy samples. Study included 8 patients with acute tubular necrosis (ATN), 8 patients with antibody-mediated rejection (ABMR), 10 patients with T-cell-mediated rejection (TCMR), 10 patients with BK polyomavirus-associated nephropathy (BKPyVAN) and 12 surveillance biopsies from patients with stable allograft function and no major abnormalities (normal allografts, CTRL).We found 136 miRNAs differentially expressed in diseased kidney transplant tissue compared with normal allografts; of these, 74 miRNAs were differentially expressed in ABMR, 65 in ATN, 62 in BKPyVAN, 69 in TCMR, and 16 miRNAs were not associated with a specific disease phenotype. In addition, 29 miRNAs were differently expressed between ABMR and ATN, 39 between BKPyVAN and TCMR, and 20 between BKPyVAN and ABMR, and 38 between ABMR and TCMR.Our findings show that miRNA derived from kidney allograft biopsy samples represent an additional diagnostic tool to distinguish different disease phenotypes. This finding has the potential to assist clinicians in therapeutic decision making and to translate to non-invasive monitoring of patients, e.g. blood samples.