Human endothelial colony-forming cells provide trophic support for pluripotent stem cell-derived cardiomyocytes via distinctively high expression of neuregulin-1

The search for a source of endothelial cells (ECs) with translational therapeutic potential remains crucial in regenerative medicine. Human blood-derived endothelial colony-forming cells (ECFCs) represent a promising source of autologous ECs due to their robust capacity to form vascular networks in vivo and their easy accessibility from peripheral blood. However, whether ECFCs have distinct characteristics with translational value compared to other ECs remains unclear. Here, we show that vascular networks generated with human ECFCs exhibited robust paracrine support for human pluripotent stem cell-derived cardiomyocytes (iCMs), significantly improving protection against drug-induced cardiac injury and enhancing engraftment at ectopic (subcutaneous) and orthotopic (cardiac) sites. In contrast, iCM support was notably absent in grafts with vessels lined by mature-ECs. This differential trophic ability was due to a unique high constitutive expression of the cardioprotective growth factor neuregulin-1 (NRG1). ECFCs, but not mature-ECs, were capable of actively releasing NRG1, which, in turn, reduced apoptosis and increased the proliferation of iCMs via the PI3K/Akt signaling pathway. Transcriptional silencing of NRG1 abrogated these cardioprotective effects. Our study suggests that ECFCs are uniquely suited to support human iCMs, making these progenitor cells ideal for cardiovascular regenerative medicine.