Abstract
In developing embryos or in vitro differentiation cultures using pluripotent stem cells (PSCs), such as embryonic stem cells and induced pluripotent stem cells, fetal liver kinase 1 (Flk1)-expressing mesodermal cells are thought to be a heterogeneous population that includes hematopoietic progenitors, endothelial progenitors, and cardiac progenitors. However, information on cell surface markers for separating these progenitors in Flk1⁺ cells is currently limited. In the present study, we show that distinct types of progenitor cells in Flk1⁺ cells could be separated according to the expression of coxsackievirus and adenovirus receptor (CAR, also known as CXADR), a tight junction component molecule. We found that mouse and human PSC- and mouse embryo-derived Flk1⁺ cells could be subdivided into Flk1⁺CAR⁺ cells and Flk1⁺CAR⁻ cells. The progenitor cells with cardiac potential were almost entirely restricted to Flk1⁺CAR⁺ cells, and Flk1⁺CAR⁻ cells efficiently differentiated into hematopoietic cells. Endothelial differentiation potential was observed in both populations. Furthermore, from the expression of CAR, Flk1, and platelet-derived growth factor receptor-α (PDGFRα), Flk1⁺ cells could be separated into three populations (Flk1⁺PDGFRα⁻ CAR⁻ cells, Flk1⁺PDGFRα⁻CAR⁺ cells, and Flk1⁺PDGFRα⁺CAR⁺ cells). Flk1⁺PDGFRα⁺ cells and Flk1⁺PDGFRα⁻ cells have been reported as cardiac and hematopoietic progenitor cells, respectively. We identified a novel population (Flk1⁺PDGFRα⁻ CAR⁺ cells) with the potential to differentiate into not only hematopoietic cells and endothelial cells but also cardiomyocytes. Our findings indicate that CAR would be a novel and prominent marker for separating PSC- and embryo-derived Flk1⁺ mesodermal cells with distinct differentiation potentials.