Influence of Pressure on Endothelial Tubulogenic Activity

We propose a comprehensive series of studies to establish fluid pressure as a mechanical modulator of capillary-like tube formation (i.e., tubulogenesis) by endothelial cells (EC). Our objective is to elucidate the involvement of the pressurized microenvironment of EC in early tubulogenic signaling processes related to angiogenesis and/or lymphangiogenesis. Previously, we showed that the endothelial phenotype is sensitive to the mean value of an applied pressure regime. Notably, our results pointed to the selective involvement of fibroblast growth factor-2 (FGF2), fibroblast growth factor receptor-2 (FGFR2) activation, and vascular endothelial growth factor-C (VEGF-C) in the enhanced proliferation rates of EC exposed to 40 mmHg mean cyclic pressures. Based on these findings and because cell proliferation is one of the earliest steps in endothelial-mediated tube formation, we hypothesize that fluid pressures modulate the induction of a tubulogenic phenotype in EC through its actions on cell signaling by select growth factors. We test this hypothesis with the following specific aims: 1) characterize the pressure-sensitivity of EC tubulogenic activity; 2) reveal the role of VEGF-C upregulation in pressure-sensitive endothelial tubulogenesis; 3) define the facultative role of pressure on FGFR2 activation by FGF2 upstream of EC tubulogenic responses; and 4) elucidate the pressure-sensitive tubulogenic phenotype (either angio- or lymphangio- genesis or both). For this purpose, we have formed a multi-disciplinary team of researchers with expertise in the fields of cell biomechanics, mechanobiology, angiogenesis, lymphangiogenesis, and growth factor binding as well as with clinical experience. This combined expertise will be utilized to systematically identify fluid pressure parameters that modulate endothelial tube formation and link these with clinical scenarios. As such, we expect to elucidate novel relationships between the pressurized environment of the EC and the induction of a specific tubulogenic phenotype based on a novel and selective growth factor signaling axis involving lymphangiogenesis-specific VEGF-C and tubulogenic FGF2. We expect our results to have direct implications in vascular pathologies associated with high morbidity (e.g., pulmonary hypertension, cancer) or that are highly-debilitating (e.g., glaucoma, lymphedema) as well as in the formulation of tissue engineering strategies that use mechanobiology to microvascularize synthetic tissues.