Triiodothyronine Promotes Cardiac Differentiation and Maturation of Embryonic Stem Cells via the Classical Genomic Pathway

摘要

Chu-Pak Lau, Hung-Fat Tse, and Chung-Wah Siu Embryonic stem cells (ESCs) can differentiate into functional car- diomyocytes and thus represent a promising cell source for car- diac regenerative therapy. Nevertheless, the therapeutic appli- cation of ESC-derived cardiomyocytes is limited by the low efficacy of the current protocol for cardiac differentiation and their immature phenotypes. Although thyroid hormone is es- sential for normal cardiac development and function, its role in the cardiac differentiation of ESCs, as well as the maturation of ESC-derived cardiomyocytes, remains unclear. In this study, we examined the cardiac differentiation of murine ESCs in the pres- ence of T; for 10 d using flow cytometry, RT-PCR, cellular elec- trophysiology study, and confocal calcium imaging. Compared with control conditions, T; supplementation increased the num- ber of ESC-derived cardiomyocytes and was accompanied by up-regulation of a panel of cardiac markers, including Nkx2.5, myosin light chain-2V, as well as a- and B-myosin heavy chain. More importantly, electrophysiological study revealed that ESC- derived cardiomyocytes exhibited more adult-like phenotypes after T, supplementation based on action potential characteris- tics. They also exhibited more adult-like calcium homeostasis properties. These phenotypic changes were associated with up- regulation of sarco(endo)plasmic reticulum calcium ATPase-2a and ryanodine receptor-2 expression. In addition, the classical (genomic) pathway was shown to be involved in T,-induced car- diac differentiation of ESCs. Our results show that T3 supple- mentation promotes cardiac differentiation of ESCs and en- hances maturation of electrophysiological, as well as calcium homeostasis, properties of ESC-derived cardiomyocytes.