Abstract 9742: Conservation of Mir Direct Cardiac Reprogramming Across Several Mammalian Species

Abstract

There is considerable interest in regenerating the injured heart by reprogramming resident fibroblasts into new functional cardiomyocytes. Cardiac reprogramming has been achieved via transcription factors or miRNAs. Transcription factor combinations appear to be species-specific as evidenced by the fact that combinations of transcription factors which are effective for the reprogramming of mouse fibroblasts, are ineffective in pigs and humans. It is unknown if miRNA based cardiac reprogramming suffers from the same limitation. We have previously demonstrated that mouse cardiac fibroblasts(mCFs) can be directly converted into cardiomyocytes both in vitro and in vivo via a combination of four microRNAs (miR-1, miR-133a, miR-208a and miR-499) termed “miR combo.” To test species-specificity, miR combo was transfected into cardiac fibroblasts isolated from the left ventricle of adult sheep, dogs, pigs and humans. Reprogramming was determined by qPCR and RNA-seq. In contrast to transcription factor based approaches, miR combo effectively reprogrammed fibroblasts from all of the tested mammalian species. Marked upregulation of cardiac developmental, sarcomere, and cardiac ion channel genes was observed (N=3-5, P<0.001).Concomitant with up-regulation of cardiomyocyte-specific signatures, fibroblast-specific genes were down-regulated (N=3-5, P<0.001). Moreover, we also observed marked downregulation of genes that are associated with neuronal, skeletal muscle and endothelial cells (N=3-5, P<0.001). Importantly, we also found that miR comb otransfection induced dog, pig and human cardiac fibroblasts to develop into cardiomyocyte-like cells (N=3, P<0.05). In conclusion, we have demonstrated that in contrast to transcription factor based approaches, miR combo effectively reprograms mammlian cardiac fibroblasts into cardiomyocyte-like cells. These findings validate the potential of miR combo as a therapeutic modality for myocardial regeneration following myocardial injury in humans.