Pulsatile Flow–Induced Angiogenesis

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 ␣ subunit of G i 1 or G i 3, but not G i 2, inhibited the flow-induced angiogenic response by 61Ϯ2% and 32Ϯ6%, respectively, whereas transfection with constitutively activated mutants of the ␣ subunit of G i 1 or G i 3, but not G i 2, increased the flow-induced response by 202Ϯ23% and 70Ϯ4%, respectively. In contrast, inhibition of G␤␥ by the carboxy terminal fragment of ␤-adrenergic receptor kinase overexpression increased the flow-induced response by 82Ϯ8%. Conclusions-These results suggest that pulsatile flow stimulates angiogenesis and that this effect is mediated by activation of G i␣ 1 or G i␣ 3, but not G␤␥, subunits.

Fluid shear stress modulates endothelial cell invasion into three-dimensional collagen matrices

“…Cullen and colleagues (10) reported that subjecting bovine aortic ECs to WSS caused Transwell migration and tubule formation to increase monotonically with increasing WSS ranging from 0 to 20 dyn/cm 2 . In these studies, Cullen et al (10) applied WSS to bovine aortic ECs before placing them onto Transwell chambers to assay migration or onto 2-D Matrigels to measure tubule formation. In our experiment, where WSS was applied during the 3-D invasion assay, invasion distance increased monotonically with increasing WSS; however, EC invasion density shows a bimodal dependence on WSS magnitude.…”

“…We were unable to stimulate invasion of ECs in a static system using conditioned media from WSS-treated invasion cultures, indicating the enhancement of invasion caused by WSS was not due to the generation of soluble proangiogenic factors. It is worth noting that these two studies (10,21) were performed using media containing 10 -20% FBS or FCS. Given that FBS and FCS contain 141-180 nM S1P, and that the K d for S1P to its receptors is ϳ20 nM (46), the possibility exists that S1P receptor activation may have contributed to the angiogenic events observed in these studies.…”

Use of Ultrasound for Non-Invasive Assessment of Flow-Mediated Dilation

“…This was until Davies et al 56) , in 1986, provided evidence that time-averaged shear stress alone could not explain the pathological behavior of endothelial cells exposed to complex flow patterns. Subsequent studies [57][58][59][60][61][62][63][64][65] have shown that vascular endothelial cells respond not only to time-averaged shear stress, but respond differently to different patterns of flow.…”

Multiple Pathogenic Roles of Microvasculature in Inflammatory Bowel Disease: A Jack of All Trades

“…84,85 Finally, shear stress on the endothelium due to increased blood flow may stimulate angiogenesis. 86,87 Initially, functional changes prevail, including dilation, increased permeability, activation of the endothelium, and diapedesis. In the second phase, structural changes occur, with capillary and venule remodeling and proliferation of ECs.…”