Microarray analysis of in vitro pericyte differentiation reveals an angiogenic program of gene expression

ABSTRACT The vasculature consists of endothelial cells (ECs) lined by pericyte/vascular smooth muscle cells (vSMCs). Pericyte/vSMCs provide support to the mature vasculature but are also essential for normal blood vessel development. To determine how pericyte‐EC communication influences vascular development, we used the well‐established in vitro model of TGFβ‐stimulated differentiation of 10T1/2 cells into pericyte/vSMCs. Microarray analysis was performed to identify genes that were differentially expressed by induced vs. uninduced 10T1/2 cells. We discovered that these cells show an angiogenic program of gene expression, with up‐regulation of several genes previously implicated in angiogenesis, including VEGF, IL‐6, VEGF‐C, HB‐EGF, CTGF, tenascin C, integrin α5, and Eph receptor A2. Up‐regulation of some genes was validated by Western blots and immunocytochemistry. We also examined the functional significance of these gene expression changes. VEGF and IL‐6 alone and in combination were important in 10T1/2 cell differentiation. Furthermore, we used a coculture system of 10T1/2 and human umbilical vein ECs (HUVECs), resulting in the formation of cordlike structures by the HUVECs. This cordlike structure formation was disrupted when neutralizing antibodies to VEGF or IL‐6 were added to the coculture system. The results of these studies show that factors produced by pericytes may be responsible for recruiting ECs and promoting angiogenesis. Therefore, a further understanding of the genes involved in pericyte differentiation could provide a novel approach for developing anti‐angiogenic therapies.