Abstract 1110: MicroRNA-1 Regulates Cardiomyocyte Differentiation And Proliferation In Human-derived Cardiomyocyte Progenitor Cells.
Myocardial regeneration can occur in humans, albeit with very low efficiency. To improve regeneration of the injured myocardium, one can enhance the intrinsic capacity of the heart to regenerate itself and/or replace the damaged tissue by cell transplantation. Recently, we have isolated cardiomyocyte progenitor cells (CMPCs) from human fetal hearts and from adult human biopsies that can be expanded in culture and efficiently differentiated into beating cardiomyocytes. In addition, these CMPCs also efficiently differentiate into tubular structures on matrigel, forming aligned endothelial cells surrounded by smooth muscle cells. Recently, several studies have demonstrated that microRNAs (miRNAs) are important for transcriptional regulation during angiogenesis, heart development, and maintenance of stem cell populations by translational repression. We hypothesize that, since miRNAs regulate stem cell maintenance, miRNAs are involved in proliferation/differentiation of the human cardiomyocytes progenitor cells in vitro.
Methods and results: Human fetal CMPCs were isolated, cultured and efficiently differentiated into beating cardiomyocytes. We observed that the muscle-specific miRNA-1 was highly upregulated (qRT-PCR, >7000 fold) in differentiated cardiomyocytes and hardly present in proliferating CMPCs. Transient transfection of miRNA-1 in undifferentiated CMPCs reduced their proliferation rate by 25% (MTT assay and FACS analysis) and enhanced differentiation into cardiomyocytes. When undifferentiated CMPCs were transiently transfected with miRNA-1 and seeded onto matrigel, angiogenic morphology was changed. The mean length and size of the tubules was significantly increased (2.5 and 4.5 fold, respectively), whereas the number of junctions was reduced by 50%. This suggests that more CMPCs were directed into the smooth muscle-like phenotype and not into branching endothelial cells, leading to larger tubules with less side junctions.
Conclusion: Our results demonstrate a strong regulatory role of miRNAs in human CMPC proliferation and differentiation into cardiomyocytes. miRNA-1 functions as a key regulator, and is involved in the onset of human CMPC differentiation into cardiomyocytes and smooth muscle like cells.