Role of alpha- and beta-adrenergic receptors in cardiomyocyte differentiation from murine-induced pluripotent stem cells

Objectives: Induced pluripotent stem cell (iPSC)-derived cardiomyocytes are a promising source of cells for regenerative heart disease therapies, but progress towards their use has been limited by their low differentiation efficiency and high cellular heterogeneity. Previous studies have demonstrated expression of adrenergic receptors (ARs) in stem cells after differentiation; however, roles of ARs in fate specification of stem cells, particularly in cardiomyocyte differentiation and development, have not been characterized. Materials and methods: Murine-induced pluripotent stem cells (miPSCs) were cultured in hanging drops to form embryoid bodies, cells of which were then differentiated into cardiomyocytes. To determine whether ARs regulated miPSC differentiation into cardiac lineages, effects of the AR agonist, epinephrine (EPI), on miPSC differentiation and underlying signalling mechanisms, were evaluated. Results: Treatment with EPI, robustly enhanced miPSC cardiac differentiation, as indicated by increased expression levels of cardiac-specific markers, GATA4, Nkx2.5 and Tnnt2. Although β-AR signalling is the foremost signalling pathway in cardiomyocytes, EPI-enhanced cardiac differentiation depended more on α-AR signalling than β-AR signalling. In addition, selective activation of α₁-AR signalling with specific agonists induced vigorous cardiomyocyte differentiation, whereas selective activation of α₂- or β-AR signalling induced no or less differentiation, respectively. EPI- and α₁-AR-dependent cardiomyocyte differentiation from miPSCs occurred through specific promotion of CPC proliferation via the MEK-ERK1/2 pathway and regulation of miPS cell-cycle progression. Conclusions: These results demonstrate that activation of ARs, particularly of α₁-ARs, promoted miPSC differentiation into cardiac lineages via MEK-ERK1/2 signalling.