Angiogenesis-like Activity of Endothelial Cells Co-cultured with VEGF-producing Smooth Muscle Cells

Abstract

A number of strategies have been investigated to improve therapeutic vascularization of ischemic and bioengineered tissues. In these studies, we genetically modified vascular smooth muscle cells (VSMC) to promote endothelial cell proliferation, migration, and formation of microvascular networks. VSMCs were virally transduced to produce vascular endothelial growth factor (VEGF), which acts as a chemoattractant and mitogen of endothelial cells (EC). VSMCs transduced with VEGF₁₆₅ cDNA produced significant levels of the protein (2–4 ng/10⁵ cell/day). The proliferation of ECs increased after exposure to VEGF-transfected SMCs or their conditioned media. The chemotactic response of ECs to the VEGF-producing cells was explored in two in vitro systems, the modified Boyden chamber assay and a 2-D fence-style migration assay, and both demonstrated increased migration of ECs in response to VEGF-transfected cells. Furthermore, endothelial cells seeded on top of the VEGF-transfected SMCs formed capillary-like structures. These results suggest that VSMCs genetically modified to produce VEGF could be a potential delivery mechanism to enhance endothelial cell migration and subsequent capillary formation, which in turn could improve vascularization of ischemic or regenerating tissue. Furthermore, this system could potentially be used as an in vitro test bed for evaluation of novel angiogenic and anti-angiogenic compounds.