Large-scale microRNA high-throughput screening identifies miR-515-3p and miR-519e-3p as inducers of human iPSC-cardiomyocyte proliferation
Ischemic heart failure persists to be a global health problem despite optimized medical and adjunctive device therapies. Loss of cardiomyocytes and the absence of a proliferative response comprise a major contributor to pathological remodeling and death in this patient population. Experimental studies have shown that miRNAs may be used as a therapeutic option to reinduce adult cardiomyocyte proliferation. Using a functional high-throughput screening, we assessed the proliferative potential after transient hypoxia of 2019 microRNAs by transfecting both miR-inhibitor and miR-mimic libraries in human iPSC-derived cardiomyocytes (hiPSC-CM). Whereas miR-inhibitors failed to enhance EdU-uptake, overexpression of 28 miRNAs substantially induced proliferative activity in hiPSC-CMs, with an overrepresentation of miRNAs belonging to the C19MC-cluster and adjacent miR-371-373 family. Two of these miRNAs, miR-515-3p and miR-519e-3p, increased markers of early and late mitosis, with an additive cardiomyocyte turnover after transient hypoxia and substantially increased presence of Aurora B-kinase in midbodies, indicative of cell division. These findings were supported by qRT-PCR, Western blot and RNA-Sequencing after overexpression of miR-515-3p and miR-519e-3p showing substantial alterations of signaling pathways relevant for cardiomyocytes proliferation in hiPSC-CM. Collectively, these results support a critical role of miR-515-3p and miR-519e-3p for induction of proliferation in human cardiomyocytes under hypoxic conditions, an integral feature of ischemic cardiomyopathy.Key Words:  Cardiomyocyte proliferation, microRNAs, cell cycle, high throughput screening, human induced pluripotent stem cells.