CD276 (B7‐H3) Maintains Proliferation and Regulates Differentiation in Angiogenic Function in Late Endothelial Progenitor Cells

Endothelial progenitor cells (EPCs) provide an important source of recovery from blood vessel dysfunction. Late EPCs (LEPCs) are circulating blood cells that are capable of promoting vascular repair. Using transcriptome analysis, we identified distinctive LEPC profiles and found that CD276 (B7‐H3) mRNA is strongly expressed in LEPCs. CD276 protein is present abundantly on the cell surface of LEPC when analyzed by fluorescence‐activated cell sorter and immunocytochemistry. CD276, a B7 family member, is a type I transmembrane glycoprotein. The role of CD276 in LEPCs remains unknown. CD276 knockdown by lentivirus transduction in LEPCs significantly decreased proliferation and increased apoptosis of LEPCs in vitro. After CD276 silencing, the cell cycle of LEPCs was prone to remain at the G0/G1 phase, and the cell migration rates as well as transwell and wound‐healing migration were decreased. CD276 knockdown in LEPCs increased the G1 phase regulators cyclin D2/D3/E1‐cyclin‐dependent kinases (CDK2/4/6), but decreased the S‐G2‐M phase regulators cyclin A/B‐CDK1. However, LEPCs with CD276 knockdown resulted in increased tube formation in vitro and angiogenesis in a Matrigel plug assay in vivo. FoxC1/C2, an upstream signal of Notch in arterial cell proliferation, and Hey1/2, which is known to promote arterial differentiation in the vasculature, were upregulated in CD276 knockdown LEPCs. In LEPCS, CD276 has a positive effect on proliferation and migration of endothelial cells, but negative effects on angiogenesis, particularly endothelial cell differentiation. Our data indicate, for therapeutic purpose, that CD276 can be used to acquire and maintain cell populations of LEPCs and blocking CD276 will promote angiogenetic differentiation. We found that CD276 (B7‐H3) is enriched on the cell membrane of LEPCs. CD276 knockdown reduced proliferation and migration of LEPCs by increasing cell cycle inhibitors such as p21cip1 and pRb and decreasing pErk1/2 and pAkt but promoted angiogenesis and endothelial cell differentiation by elevating vascular endothelial growth factor‐vascular endothelial growth factor receptor 1 and p‐p38. Stem Cells 2019;37:382–394 We found CD276 (B7‐H3) is enriched on the cell membrane of late endothelial progenitor cells (LEPCs). CD276 knockdown reduced proliferation and migration of LEPCs by increasing cell cycle inhibitors such as p21cip1 and pRb and decreasing pErk1/2 and pAkt but promoted angiogenesis and endothelial cell differentiation by ele