In the myocardium, microRNAs have been postulated to be organized in complex genetic regulatory networks that regulate the hypertrophic and fibrotic remodeling responses to biomechanical stress. We hypothesized that miR-21 and miR-30c could exert collaborative effects on the early myocardial fibrotic response to pressure overload in mice.Methods
Female mice were subjected to gauged transverse aortic constriction (TAC) or sham surgery (Sham) for 1, 3, 7 or 14 hours (n=6 per group). Cultured NIH-3T3 fibroblasts were transfected with a precursor of miR-21 (pre-miR-21) or a snRNA control oligonucleotide. Small and large RNA expressions were determined by quantitative PCR with specific TaqMan assays.Results
The LV expression levels of mir-21 and miR-30c increased significantly after TAC following parallel time courses during the 14 h follow-up. The relative increase values of both miRNAs in TAC vs sham mice were significantly and directly correlated (Pearson's r=0.85, p < 0.001). MiR-21 and miR-30c kept a significant and positive correlation with the fibrosis related genes, collagen I and collagen III [(miR-21 vs COL I: r=0.68; p < 0.001); (miR-21 vs COL III: r=0.63 p < 0.01); (miR-30 vs COL I: r=0.58; p < 0.01); (miR-30 vs COL III: r=0.46; p < 0.05)]. Transfection of pre-miR-21 to cultured fibroblasts induced overexpression not only of miR-21 (32 ± 3.0 at 0nM pre-miR-21 vs 442 ± 16 at 10 nM pre-miR-21, p < 0.001) but also of miR-30c (21.9 ± 3.8 at 0nM pre-miR-21 vs 178 ± 58 at 10 nM pre-miR-21, p < 0.05).Conclusion
The synchronous and correlative myocardial over-expression of miR-21, miR-30c and collagens suggest a highly coordinated regulatory role for these miRNAs on the early remodeling response to pressure overload. We postulated that, as occurs in the synexpression groups of genes, a network of regulatory elements could govern the tight spatiotemporal co-expression of the miRNAs involved in the fibrotic process. (Funding: ISCIII, PS09/01097; FMV-UC 09/01; FMV-API 10/20).