MicroRNAs and the kidney: coming of age

Purpose of review MicroRNAs (miRNAs) are regulatory RNAs that act as posttranscriptional repressors by binding the 3' untranslated region of target genes. They have been implicated in diverse biologic and pathologic processes and are emerging as important players in kidney health and disease. Here, we review the latest literature in this exciting and rapidly evolving field. Recent findings Studies of conditional Dicer knockout mice revealed critical roles for miRNAs in orchestrating kidney development and maintaining the structural and functional integrity of the renal collecting system and glomerular barrier. Expression profiling has provided a reasonably clear picture of miRNAs present in normal kidney and pointed to individual miRNAs that may serve special functional roles therein. Specific miRNAs have been implicated in pathways linked to cystic kidney disease (mir-15a), and Wilms' tumor (miR-17-92). Several miRNAs are upregulated by transforming growth factor beta-1 in models of diabetic nephropathy. Some promote matrix deposition (miR-192 and miR-377) or epithelial-to-mesenchymal transition (miR-200 and miR-205), whereas preliminary findings suggest others might serve protective roles (miR-21). miRNAs recently identified in urinary exosomes could potentially serve as disease biomarkers. Summary Nephrology is in the midst of a miRNA 'revolution' that promises incredible advances in our understanding of genetic regulatory pathways underlying kidney disease, and, with it, new avenues for treatment.