Abstract 298: Pluripotent Stem Cell Microrna-294 as a Mediator of Cardiac Proliferative Response After Myocardial Injury

Abstract

Rationale: Embryonic heart is characteristic of rapidly dividing cardiomyocytes required to build a working myocardium. In contrast, cardiomyocytes retain some proliferative capacity in the neonates but lose most of it in adulthood. Embryonic stem cell cycle (ESCC) miRs are a class of microRNAs regulating the unique cell cycle of ESCs and their characteristic pluripotency. Nevertheless, expression of miR-294, a member of the ESCC miRs is lost during developmental transitions from the ESCs to mature cells. Effect of miR-294 to induce cardiac proliferation and heart function has not been previously studied. Objective: To determine whether miR-294 drives cardiac proliferative response leading to augmentation of cardiac function after myocardial infarction. Methods and Results: miR expression analysis in the heart during development revealed elevated levels of miR-294 in the prenatal stages while the expression was lost in the neonates and adults as confirmed by qRT-PCR. Neonatal ventricular cardiomyocytes (NRVMs) treated with miR-294 mimic to showed elevated mRNA levels of cell cycle markers ( E2F family and cyclins ) concurrent with increased expression of p-histone 3, Ki67 and Aurora B kinase (G2/M) as confirmed by immunocytochemistry compared to control cells. Cardiac progenitor cells (CPCs) engineered with miR-294 lentivirus led to increased proliferation and metabolic activity. An inducible cardiac specific AAV-9 carrying miR-294 was administered in mice subjected to myocardial infarction. Increased cardiac function in mice receiving AAV-miR-294 was observed 8 weeks after injury. Increase myocyte proliferation was observed in the heart after miR-294 treatment as analyzed by BrdU uptake, p-Histone 3 and Aurora B expression by immunostaining. Concurrently, a decrease in infarct size along with decreased apoptosis was observed in the miR-294 hearts compared to the control. Furthermore, increased c-kit+ CPCs activation and proliferation was observed in the miR-294 receiving hearts. Conclusion: Ectopic expression of miR-294 recapitulates embryonic signaling and enhances cardiomyocyte ability to proliferate together with CPC activation and expansion leading to augmented cardiac function in mice after myocardial infarction.