STAT3-dependent mouse embryonic stem cell differentiation into cardiomyocytes: analysis of molecular signaling and therapeutic efficacy of cardiomyocyte precommitted mES transplantation in a mouse model of myocardial infarction.

Pluripotent embryonic stem (ES) cell therapy may be an attractive source for postinfarction myocardial repair and regeneration. However, the specific stimuli and signal pathways that may control ES cell-mediated cardiomyogenesis remains to be completely defined. The aim of the present study was to investigate (1) the effect and underlying signal transduction pathways of leukemia inhibitory factor (LIF) and bone-morphogenic protein-2 (BMP-2)-induced mouse ES cell (mES-D3 line) differentiation into cardiomyocytes (CMC) and (2) the efficacy of CMC precommitted mES cells for functional and anatomical cardiac repair in surgically-induced mouse acute myocardial infarction (AMI) model. Various doses of LIF and BMP-2 and their inhibitors or blocking antibodies were tested for mES differentiation to CMC in vitro. CMC differentiation was assessed by mRNA and protein expression of CMC-specific markers, Connexin-43, CTI, CTT, Mef2c, Tbx5, Nkx2.5, GATA-4, and alphaMHC. LIF and BMP-2 synergistically induced the expression of CMC markers as early as 2 to 4 days in culture. Signaling studies identified STAT3 and MAP kinase (ERK1/2) as specific signaling components of LIF+BMP-2-mediated CMC differentiation. Inhibition of either STAT3 or MAPK activation by specific inhibitors drastically suppressed LIF+BMP-2-mediated CMC differentiation. Moreover, in mouse AMI, transplantation of lentivirus-GFP-transduced, LIF+BMP-2 precommitted mES cells, improved post-MI left ventricular functions, and enhanced capillary density. Transplanted cells engrafted in myocardium and differentiated into CMC and endothelial cells. Our data suggest that LIF and BMP-2 may synergistically enhance CMC differentiation of transplanted stem cells. Thus augmentation of LIF/BMP-2 downstream signaling components or cell type specific precommitment may facilitate the effects of ES cell-based therapies for post-MI myocardial repair and regeneration.