Different regulation of miR-29a-3p in glomeruli and tubules in an experimental model of angiotensin II-dependent hypertension: potential role in renal fibrosis

The aim of this study was to evaluate the role of the angiotensin II (Ang II) induced-differential miRNA expression in renal glomerular and tubulo-interstitial fibrosis in an experimental model of Ang II-dependent hypertension. To clarify this issue, Sprague Dawley rats were treated with Ang II (200ng/kg per minute, n=15) or physiological saline (n=14) for 4weeks. Systolic blood pressure and albuminuria were measured every 2weeks. At the end of the experimental period, renal glomerular and tubulo-interstitial fibrosis was evaluated by histomorphometric analysis, after Sirius-Red and Masson's trichrome staining. Ang II increased systolic blood pressure (P<0.0001), albuminuria (P<0.01) and both glomerular and tubulo-interstitial fibrosis (P<0.01). Using laser capture microdissection and miRNA microarray analysis this study showed that miR-29a-3p was down-regulated in renal tubules and up-regulated in glomeruli. Real-time polymerase chain reaction (PCR) experiments confirmed in Ang II-treated rats a down-regulation of miR-29a-3p in tubules (P<0.01), while no significant changes were observed in glomeruli. Matrix metalloproteinase-2 (MMP-2) was identified as putative miR-29a-3p target (by TargetScan, miRanda, Tarbase software) and functionally confirmed by luciferase activity assay. These data demonstrate that the effects of Ang II on miR-29a-3p expression in renal tubules is different from the one exerted in the glomeruli and that miR-29a-3p targets MMP-2. These results suggest that the development of renal fibrosis at glomerular and tubulo-interstitial level depends on different molecular mechanisms.