Background:Calcineurin inhibitor nephrotoxicity (CNIT) is a well-known contributor to chronic allograft dysfunction in kidney transplant recipients (KTRs). Pediatric KTRs are particularly at risk given their duration of calcineurin inhibitor exposure. Current reliance on late and insensitive markers (serum creatinine) precludes identification of CNIT prior to the onset of irreversible damage. Understanding the molecular pathways related to CNIT could allow development of early diagnostic/monitoring tools and guide individualization of therapy.

Methods:40 de-identified formalin-fixed paraffin-embedded kidney biopsies from pediatric KTRs with histologic diagnosis of CNIT were classified into training/validation sets. Normal allograft (NA) samples served as controls, while acute rejection and interstitial fibrosis/tubular atrophy samples were used to determine marker specificity. Isolated total RNA was evaluated for gene expression (SensationPlus™) and microRNA (miRNA) profiles using microarrays in the training set (Affymetrix™ GeneChip® HG-U133 2.0 microarray, GeneChip® miRNA v4.0 Array). Differentially expressed genes/miRNA probesets with a p-value<0.005, FDR<5%, ≥2-fold change were validated by RT-qPCR. Gene ontology, pathway analysis, and integrative approaches were used to evaluate biological significance.

Results:119 miRNA and 1384 gene probe sets were differentially expressed between CNIT and NA biopsies. CNIT-associated molecular functions identified included cellular growth/proliferation, as well as cell death, necrosis, and apoptosis (p <0.001). TGFB-1 was identified as a top upstream regulator in the pathway analysis, and was validated by RT-qPCR. 55 genes were associated with nephrotoxicity, including cell death of renal tubular cells and apoptosis of podocytes. Important predicted miRNAs included miR-199a-3p and miR-30c-5p; miR-199a-3p was differentially expressed by microarray and validated by RT-qPCR in both training and validation sets.

Conclusions:The interplay of identified differentially expressed miRNAs:mRNAs may provide the basis for a unique molecular signature for accurate pediatric CNIT diagnosis. In particular, miR-199a-3p and miR-30c-5p are candidate biomarkers that warrant further investigation.

CITATION INFORMATION: Rhone E, Gehrau R, Bontha S, Walker P, Dumur C, Maluf D, Mas V. Genomic-Derived Markers to Identify Calcineurin Inhibitor Nephrotoxicity in Pediatric Kidney Transplant Recipients. Am J Transplant. 2016;16 (suppl 3).

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