Tissue microenvironment dictates the state of human iPSC-derived endothelial cells of distinct developmental origin in 3D cardiac microtissues

Each tissue and organ in the body has its own type of vasculature. Here, we demonstrate that organotypic vasculature for the heart can be recreated in a three-dimensional cardiac microtissue (MT) model composed of human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs), cardiac fibroblasts (CFs), and endothelial cells (ECs). ECs in cardiac MTs upregulated expression of markers enriched in human intramyocardial ECs, including <i>CD36</i>, <i>CLDN5</i>, <i>APLNR</i>, <i>NOTCH4</i>, <i>IGFBP3</i>, and <i>ARHGAP18</i>. We further show that the local microenvironment largely dictates the organ-specific identity of hiPSC-derived ECs: we compared ECs derived from cardiac and paraxial mesoderm and found that, regardless of origin, they acquired similar identities upon integration into cardiac MTs. Overall, the results indicated that while the initial gene profile of ECs was dictated by developmental origin, this could be modified by the local tissue environment. This developmental "plasticity" in ECs has implications for multiple pathological and disease states.