In vitro generation of human embryonic stem cell-derived heart organoids possessing physiological ion currents

Recently, methods for in vitro organogenesis have been widely developed due to their strong potential for medical applications. Cardiac organoids with functional ion channel activity are necessary for non-clinical applications.

In the present study, we optimized the culturing method of human heart organoids (hHOs) from human embryonic stem cells (hESCs) in the presence of the highly concentrated laminin-entactin and fibroblast growth factor 4 by the supplementation of BMP4, BMP10 and ROCK inhibitor (Y27632).

The resulting hHOs showed distinctive cardiac morphology with atrium- and ventricle-like chambers composed of cardiac cells, smooth muscle and endothelial cells as well as expressed the integral proteins of gap junctions like Connexin 40 (Cx40), Cx43 and Cx45, and ion channel proteins including K_ir2.1(KCNJ2), hERG (KCNH2), Na_v1.5 (SCN5A), and Ca_v1.2 (CACNA1C). In addition to the contractile ability in hHOs, isolated cardiomyocytes from these hHOs exhibited Na and Ca currents by patch clamp analysis.

These results indicate that hHOs generated in this study retain physiological cardiac functions, as they recapitulate in vivo cardiac ion currents and cardiac muscle contraction, although their abilities remain limited. The present method for hHOs will contribute to understanding the fundamental mechanism of cardiogenesis and provide an alternative tool for cardiac safety assessment of newly developed drugs as an in vitro human ESC-derived test system.