Efficient generation of human embryonic stem cell-derived cardiac progenitors based on tissue-specific EGFP expression

Cardiac progenitor cells (CPCs) are committed to the cardiac lineage but retain their proliferative capacity before becoming quiescent mature cardiomyocytes. In medical therapy and research the use of human pluripotent stem cell-derived CPCs would have several advantages over mature cardiomyocytes, as the progenitors show better engraftment into existing heart tissues, and provide unique potential for cardiovascular developmental, as well as for pharmacological studies. Here we demonstrate that the CAG promoter-driven EGFP reporter system allows the identification and isolation of embryonic stem cell-derived CPCs. Tracing of CPCs during differentiation confirmed upregulation of surface markers, previously described to identify cardiac precursors and early cardiomyocytes. Isolated CPCs express cardiac lineage specific transcripts, still have proliferating capacity and can be re-aggregated into embryoid body-like structures (CAG-EGFPhigh rEBs). Expression of TROPONIN T and NKX2.5 mRNA are upregulated in long-term cultured CAG-EGFPhigh rEBs, in which more than 90% of the cells become Troponin I positive mature cardiomyocytes. Moreover, about one third of the CAG-EGFPhigh rEBs show spontaneous contractions. The method described here provides a powerful tool to generate expandable cultures of pure human CPCs which can be used to elucidate toxicological mechanisms during cardiac development, as well as to explore early markers of the cardiac lineage.