The heart forming region of early chick embryo is an alternative source of embryonic stem cells.

In early chick embryo, the precardiac cells reside within distinct groups of mesodermal cells known as presumptive heart forming regions (HFRs). HFRs are located on the lateral sides of the Hensens node. In an effort to study fate of HFRs in isolation, HFRs were excised from early gastrulating chick embryos and cultured in vitro. A very small proportion of HFRs from 18 h incubated embryos differentiated into beating cardiomyocytes whereas about 43% of HFRs from embryos incubated for longer durations (20, 23 and 28 h) showed beating activity. The potential of HFRs, from 18 h incubated embryos, to differentiate into cardiomyocytes increased significantly in presence of Hensens node. About one third of the HFR cells underwent spontaneous differentiation into adipocytes in culture. Simultaneously, some of the cells derived from HFRs exhibited alkaline phosphatase (AP) activity indicating presence of stem cells in the culture. HFR cells were positive for vimentin indicating their mesenchymal origin. FGF supplement increased the proportion of AP-positive cells in a dose dependent manner. The present study demonstrates that HFRs can serve as a source of mesenchymal stem cells which can be gainfully employed for various purposes. The results also suggest that even though the in vitro cultured HFRs from 18 h incubated HH stage 4 chick embryo retain the potential to undergo cardiac differentiation, certain instructive signals from Hensens node may reinforce the fate.