Differential behavior of pericytes and adipose stromal cells in vasculogenesis and angiogenesis

Perfusable vascularization of tissue-engineered systems remains one of the main hurdles in producing large-scale functional tissues. Blood vessel formation by endothelial cells is dependent on supporting cells such as stromal cells. From them, the pericyte is the most relevant due to its close interaction with the endothelial cells, protecting them from external harm and architecting new vessels and connections. However, the identity of this cell type and its relation with other mesodermic cells, such as the mesenchymal stromal/stem cells, is highly debated. In this study, we delve into the distinct behavior of stromal cells and pericytes in the context of vascularization. The protein MCAM/CD146 was proposed as a specific marker for pericyte selection from adipose-derived stromal cells. By employing microfluidic chips that consist of an internal chamber flanked by two parallel media channels, we replicated the primary processes involved in vessel formation: vasculogenesis, which refers to the de novo vessel formation, and angiogenesis, the sprouting of new vessels from existing ones. In angiogenesis, pericytes promoted significantly more and bigger sproutings than the stromal cells. In vasculogenesis, stromal cells promoted the formation and proliferation of endothelial structures similar to the embryonic capillary plexus, whereas pericytes arrested the endothelial cell division and forced them to form vessel-like structures. Furthermore, pericytes exhibited an intimate interaction with endothelial cells leading to the synthesis of a shared basement membrane between these cell types, which was rarely observed for its unselected counterpart. Bulk mRNA sequencing confirmed an upregulation of pro-vascularization and cytostatic genes in co-cultures of pericytes and endothelial cells; while stromal cells strongly stimulate mitosis and organelle biogenesis pathways, and decrease inflammatory cytokines, explaining the different vasculogenesis outcomes. We therefore confirm MCAM as a specific marker for pericyte isolation from adipose tissue, also showing that this cell type acts as a mural cell in co-culture with endothelial cells in microfluidic chips, promoting their angiogenic sprouting and vasculogenic tubulogenesis. ### Competing Interest Statement The authors have declared no competing interest.