Abstract 496: Deep Sequencing of microRNAs in Medullary Thick Ascending Limbs Isolated From Fibrotic and Non-Fibrotic Regions of a Kidney
Renal medullary fibrosis is a pathological hallmark of Dahl salt-sensitive (SS) rats fed a high-salt diet. The development of fibrosis is localized and progressive. We examined alterations of microRNA expression in medullary thick ascending limbs (mTALs) during the progression of fibrosis within a kidney. mTALs were isolated using laser capture microdissection from fibrotic and non-fibrotic regions of the same kidney in SS rats fed a 4% NaCl diet for 14 days (n=5) or from SS rats maintained on a 0.4% NaCl diet (n=2). microRNA expression profiles were examined using next-generation sequencing. microRNA abundance profiles were highly reproducible across rats (r2=0.93 to 0.99). Detectable microRNAs included 130 known rat microRNAs, 64 microRNA homologs, 89 newly predicted rat microRNAs, and 13 newly predicted microRNA homologs. Four known rat microRNAs, 4 newly predicted rat microRNAs, and 1 microRNA homolog exhibited p values of less than 0.1 (paired t-test) between mTALs isolated from fibrotic and non-fibrotic regions in rats fed the high-salt diet (n=5). Seventeen microRNAs exhibited p values of less than 0.05 (unpaired t-test) in mTALs isolated from non-fibrotic kidney regions of SS rats fed the high-salt diet (n=5) compared to mTALs from SS rats fed the 0.4% NaCl diet (n=2). Thirteen microRNAs were identified when mTALs isolated from fibrotic regions were compared to SS rats fed the 0.4% NaCl diet, 6 of which overlapped with microRNAs identified from non-fibrotic regions. The 4 known rat microRNAs identified from the comparison of fibrotic and non-fibrotic regions within a kidney included 2 members of the miR-30 family (miR-30a and miR-30b-5p). Both miR-30’s were down-regulated in mTALs isolated from fibrotic regions compared to non-fibrotic regions. We previously found that miR-30b was down-regulated in human kidney epithelial cells treated with the pro-fibrotic factor TGFβ1. miR-30a or miR-30b was not identified in comparisons of SS rats on the 4% and 0.4% NaCl diets. The study was the first to examine genome-wide molecular profiles in tissue regions in different stages of injury progression within a kidney. The result suggests that down-regulation of the miR-30 family in mTALs might contribute to the progression of renal medullary fibrosis in SS rats.
- © 2012 by American Heart Association, Inc.