Identification of cardiac stem cells with FLK1, CD31, and VE‐cadherin expression during embryonic stem cell differentiation

We evaluated the expression of the FLK1, one of the lateral mesoderm early markers where cardiogenesis occurs, to characterize and isolate cardiac stem/progenitor cells from ES cells. Dissociated cells from embryoid bodies (EBs) on day 3, 4, or 5 were collected into two subpopulations with or without FLK1 expression and coculture on OP9 stromal cells was continued to examine whether contracting colonies came out or not. FLK1 + cells from EBs at days 3 and 4 formed spontaneous contracting colonies more efficiently than FLK1 − cells on the same days, but not at day 5. Most contracting cardiac colonies derived from FLK1 cells mainly on day 4 were detected on endothelial cells along with hematopoietic cells. Further characterization of cells with these capabilities into three lineages revealed the FLK1 + CD31 − VE‐cadherin ‐ phenotype. Our findings indicate that FLK1 + cells, especially FLK1 + CD31 − VE‐cadherin − cells, could act as cardiohemangioblasts to form cardiac cells as well as endothelial cells and hematopoietic cells.—Iida, M., Heike, T., Yoshimoto, M., Baba, S., Doi, H., Nakahat, T. Identification of cardiac stem cells with FLK1, CD31, and VE‐cadherin expression during embryonic stem cell differentiation. FASEB J. 19, 371–378 (2005)