Pulsatile Flow–Induced Angiogenesis

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Abstract
Objective— Angiogenesis plays a key role in the growth and function of normal and pathological tissues. We investigated the effect of pulsatile flow on endothelial cell (EC) in vitro angiogenic activity. Methods and Results— Bovine aortic ECs were exposed to “static” or “flow” (1.2 to 67.0 mL/min, shear stress 1.4 to 19.2 dyne/cm 2 ) conditions for 2 to 24 hours. After exposure, angiogenesis was measured as tubule formation on Matrigel, and EC migration was assessed by filter migration assay. Pulsatile flow increased angiogenesis and EC migration in a temporal and force-dependent manner, with a maximal effect at 16 hours (13.2 dyne/cm 2 ). Pertussis toxin completely inhibited the effect of pulsatile flow on angiogenesis and migration. Transfection of ECs with inhibitory mutants of the α subunit of G i 1 or G i 3, but not G i 2, inhibited the flow-induced angiogenic response by 61±2% and 32±6%, respectively, whereas transfection with constitutively activated mutants of the α subunit of G i 1 or G i 3, but not G i 2, increased the flow-induced response by 202±23% and 70±4%, respectively. In contrast, inhibition of Gβγ by the carboxy terminal fragment of β-adrenergic receptor kinase overexpression increased the flow-induced response by 82±8%. Conclusions— These results suggest that pulsatile flow stimulates angiogenesis and that this effect is mediated by activation of G iα 1 or G iα 3, but not Gβγ, subunits.