Abstract 5357: MicroRNA 25 and 29a are Differentially Regulated in SMAD-3 Deficient Mice in Pressure Overload Cardiac Hypertrophy and Decrease Collagen Synthesis in Isolated Cardiac Fibroblasts
We have shown previously that there is a significant 2.8-fold decrease in myocardial fibrosis in Smad-3 knockout (KO) mice subjected to transaortic constriction (TAC). However, the exact mechanisms linking Smad-3 activation and myocardial fibrosis are not known. Noting that micro RNAs (miRs) play an important role in regulating cardiac remodeling, we sought to determine whether miRNAs were differentially regulated in Smad-3 KO mice subjected to TAC compared to littermate controls(LM). MicroRNA array analysis of sham and banded Smad-3 KO and LM mice revealed differential expression of 55 miRs (p<0.01 by ANOVA). We cross-referenced known or predicted miR interactions using 3 target-prediction algorithms, and found that 9 candidate miRs had two or more predicted fibrosis related gene targets, of which miR-25 and miR-29a had significantly more targets than the others. To determine whether these lead candidate miRs were sufficient to suppress collagen synthesis, we transfected isolated mouse cardiac fibroblasts with miR-25 and 29a precursors, and examined mRNA levels for collagen subunits 1α1, 1α2 and 3α1 by real-time PCR at 48 hours. We found that miR-25 significantly (p < 0.05) suppressed mRNA levels for collagen 1α2 and that miR-29a suppressed mRNA levels for collagen 1α1, 1α2 and 3α1 when compared to control fibroblasts transfected with a scrambled miR. These results show for the first time that miR-25 and 29a are sufficient to suppress collagen synthesis in isolated cardiac fibroblasts, and suggest that miR-25 and 29a may represent novel targets for preventing the pathological myocardial fibrosis observed in pressure overload cardiac hypertrophy.