Coregulation of VEGF-A And PLGF in Vascular Endothelial and Smooth Muscle Cells

Abstract Placental growth factor (PLGF) and vascular endothelial growth factor-A (VEGF-A) are important regulators of both physiological and pathological vascular remodeling. We previously reported that in monoculture human coronary EC primarily expresses PLGF, while human coronary smooth muscle cells (SMC) primarily express VEGF-A. However, in the vasculature, EC and SMC are in close proximity. Thus, in this study we sought to 1) determine whether this cell-specific expression pattern is maintained when EC and SMC are cocultured, and 2) test the hypothesis that EC and SMC co-regulate the expression of VEGF-A and PLGF. EC and SMC were cultured on either side of a porous Transwell insert and media PLGF and VEGF-A levels were measured by ELISA. We confirmed that the cell type-specific expression of PLGF and VEGF-A we observed in monocultures remains evident in the coculture model. Interestingly, coculture of EC and SMC increased media PLGF relative to EC monoculture, but decreased media VEGF-A compared to SMC monoculture. Coculture conditions also increased VEGFR2 levels on the surface of EC but decreased VEGFR1 levels on the surface of SMC. Inhibition of VEGFR2 tyrosine kinase activity decreased PLGF and increased VEGF in both EC and cocultures but not in SMC monocultures. We conclude that PLGF and VEGF-A exert both paracrine and autocrine regulatory effects on each other and that these effects are mediated by VEGFR2 (in EC) and VEGFR1 (in SMC). Based on these results, we recommend that researchers investigating VEGFR signaling consider the use of coculture models when designing studies.