Cardiovascular diseases remain the major cause of death in the western world. Stem and progenitor cell-derived cardiomyocytes (SPC-CMs) hold great promise for myocardial repairs. Recent advances in reprogramming somatic cells to induced pluripotent stem cells (iPSCs) open the door for future patient-specific, cell-based therapies. However, most SPC-CMs displayed immature electrophysiological (EP) phenotypes with variable automaticity. Implanting these electrically immature cardiomyocytes (CMs) into hearts might carry arrhythmogenic risks. Human embryonic stem cell (hESC)- or human iPSC-derived cardiomyocytes (hESC-CMs or iPSC-CMs) provide a model system to study the development of CMs, in part because they are an immature population of cardiomyocytes that could continue to mature in the embryoid body (EB) environment. Elucidating cellular factors and molecular pathways governing electrical maturation of early hESC-CMs would enable engineered microenvironment to create electrophysiologically compatible hESC-CMs for a safe cell-based therapy of cardiovascular diseases.
Using hESC-CMs and an antibiotic-selection system to isolate hESC-CMs (>95% purity), we found that non-myocardial cells in EBs induced electrical maturation and ion channel expression of primitive hESC-CMs during differentiation. A novel add-back (co-culture) method was also established to enable an engineered microenvironment for controlled EP maturation of primitive hESC-CMs. With these established methods, we further studied the role of endothelial cells (ECs) and their molecular pathways in inducing EP maturation of primitive hESC-CMs. In the Year 1, our data firmly support that ECs influenced the EP maturation of primitive hESC-CMs through their paracrine pathways and various types of receptors. In particular, we found that ECs significant influenced the expression of several specific types of ion channels of early hESC-CMs via paracrine pathways. We also generated new iPSC lines from various fibroblast sources to determine if these iPSCs possess similar cardiogenic capability as H9 hESCs. We will apply information obtained from hESC-CM experiments to induce EP maturation of cardiomyocytes derived from various iPSCs. Our proposed study potentially will provide significant insights in directed ion channel maturation of primitive SPC-CMs and in improving the safety of current cell-based therapies in hearts.