Angiotensin II receptor blocker valsartan ameliorates cardiac fibrosis partly by inhibiting miR-21 expression in diabetic nephropathy mice.

Cardiac fibrosis with diabetic nephropathy (DN) is one of major diabetic complications. miR-21 and MMP-9 were closely associated with fibrosis diseases. Angiotensin II receptor blockers (ARB) have cardioprotective effects. However, it remains unclear whether miR-21 was involved in the mechanism of cardiac fibrosis with DN by target MMP-9 and ARB ameliorates cardiac fibrosis partly by inhibiting miR-21 expression. In this study, In Situ Hybridization(ISH), RT-PCR, cell transfection, western blotting and laser confocal telescope were used, respectively. ISH showed that miR-21, concentrated in cytoplasmic foci in the proximity of the nucleus, was mainly localized in cardiac fibroblasts and at relatively low levels in cardiomyocytes within cardiac tissue with DN. RT-PCR showed that miR-21 expression was significantly enhanced in cardiac tissue with DN, accompanied by the increase of col-IV, FN, CVF, PVCA, LVMI, HWI and NT-pro-BNP (p < 0.05). Bioinformatics analysis and Luciferase reporter gene assays showed that MMP-9 was a validated target of miR-21. Furthermore, cell transfection experiments showed that miR-21 overexpression directly decreased MMP-9 expression. Interestingly, miR-21 levels in cardiac tissue was positively correlated with ACR (r = -0.870, P = 0.003), whereas, uncorrelated with SBP, HbA1C and T-Cho (p > 0.05). More importantly, ARB can significantly decrease miR-21 expression in cardiac tissue, cardiac fibroblasts and serum. Overall, our results suggested that miR-21 may contribute to the pathogenesis of cardiac fibrosis with DN by target MMP-9, and that miR-21 may be a new possible therapeutic target for ARB in cardiac fibrosis with DN.