Abstract 13347: Injectable Collagen-based Hydrogel Matrix Modulates Micro-RNA Expression and Prevents Cardiac Deterioration Post-myocardial Infarction

Background: Injectable hydrogel biomaterials have emerged as promising therapies for treating myocardial infarction (MI). We developed a collagen type I based injectable hydrogel matrix that can prevent the deterioration of cardiac function when delivered soon post-MI and found that the effects may be mediated through a microRNA (miRNA) mechanism. Methods/Results: C57BL/6J mice underwent LAD ligation to induce MI. Mice then received myocardial injections of PBS or matrix delivered at 3hours post-MI. Analyses were performed at 2 days, 1 and 3 months post-treatment. At one month post-treatment, mice that received the matrix had superior left ventricular ejection fraction (LVEF; 45.1±2.3%) compared to the PBS group (29.6±2.4%; p< 0.001). LVEF was maintained in matrix-treated mice at 3 months (42.9±3.8%). Matrix treatment was also associated with reduced infarct sizes and improved ventricular volumes. Matrix-treated mice had more angiogenesis, mitigated apoptosis and reduced inflammation in the infarcted myocardium at both 2 and 28 days post-treatment. To better understand the mechanisms, we performed miRNA microarrays on infarct and peri-infarct tissue. Matrix treatment resulted in 120 miRNAs with differential expression within +/- 0.3 log2 fold change. In particular, we found matrix treatment down-regulated miR-92a ( p< 0.0005), an anti-angiogenic miRNA. Integrins α5 (Itgα5) and αV (ItgαV), involved in angiogenesis and cell-matrix interactions, were identified as putative miR-92a targets and pursued further in vitro using circulating angiogenic cells (CACs). CACs cultured on the matrix had increased Itgα5 and ItgαV expression after 4 days (12.4-fold and 13.9-fold, respectively vs. fibronectin; p< 0.01). When applied in an in vitro angiogenesis assay, the number of CACs that incorporated into capillary-like structures was greater (by 4.2-fold) for cells derived from matrix culture ( p <0.005). Conclusion: We demonstrate pronounced benefits associated with our hydrogel matrix when delivered at 3h post-MI. The matrix effects may be mediated, at least in part, through its ability to regulate miR-92a and integrin-mechanisms. Overall, the matrix may provide a promising therapeutic approach for protecting the myocardium post-MI.