UCLA

Ischemic damage from a myocardial infarction can have dramatic negative effects on the heart's ability to adequately perfuse the body, due to the irreversible loss of over a billion cardiomyocytes responsible for ventricular contraction. Regenerative therapies utilizing multipotent cardiac progenitor cells (CPCs) derived from either human embryonic (hESCs) or induced pluripotent stem cells have gained popularity as potential alternatives to someday replace expensive, high-risk medical procedures. Previous studies identified multipotent progenitors localized in the endocardial cushions of the developing mouse heart that co-expressed CD31 and PDGFRα. Additionally, recent data in mice have shown that the loss of a single transcription factor, Scl, enabled robust cardiomyogenic differentiation from endothelium in the heart, resulting in the ectopic appearance of these progenitor cells. However, no studies have shown similar findings in humans.

The purpose of this study is to identify these CD31+/PDGFRα+ cells in the human heart and generate cardiomyocyte-like cells from hESC-derived endothelium. It is hypothesized that human endogenous and embryonic stem cell-derived endothelial cells possess unrealized cardiomyogenic potential. Stained sagittal sections of week 9, 15, and 17 human fetal hearts showed the co-expression of the cell surface markers PDGFRα and CD31 on cells surrounding the ventricular vasculature. In addition, a 5-step protocol was used to differentiate hESCs into cardiomyocyte-like cells through an endothelial cell intermediate. Yield of isolated mesodermal progenitor cells was approximately 10.5%. Under the modified sorting protocol, yield of the mesodermal progenitor cells was approximately 18.6%. The subsequent cell sort yield for CD31+ endothelial cells was approximately 4.8%. Under the modified protocol with and without the addition of lithium chloride, endothelial cell yields were 21.3% and 26.6% respectively. The hESC-derived endothelial cells showed the formation of blood tubes in vitro and, once in cardiac growth medium, expressed Troponin T under fluorescence microscopy. Based on these results, this population of CD31+/PDGFRα+ cells could represent a latent population of cardiac progenitors capable of differentiating into cardiomyocytes.