Endothelial biomechanics is emerging as a key player in the regulation of vascular endothelial cells. Here, we address the mechanism of endothelial stiffening induced by oxidized-LDL (oxLDL), a potential determinant of cardiovascular disease. We also investigate the role of oxLDL-induced endothelial stiffening in lumen formation. Endothelial stiffness was estimated by analyzing progressive membrane deformation using Micropipette Aspiration. We show that oxLDL induces RhoA activation and that oxLDL-induced endothelial stiffening is abrogated by inhibition of RhoA or its downstream target ROCK. 7-ketocholesterol, a major oxysterol in oxLDL increases endothelial cell stiffening, contractility and network formation. OxLDL-induced increase in endothelial force generation estimated in a gel contraction assay also required RhoA/ROCK activity. OxLDL also facilitates formation of endothelial branching networks in 3D collagen gels in vitro and induces increased formation of functional blood vessels in a Matrigel plug assay in vivo. Both effects are RhoA and ROCK dependent. Importantly, loading cells with cholesterol prevented oxLDL-induced RhoA activation and the downstream signaling cascade and reversed oxLDL-induced lumen formation. The observed effects on oxLDL-induced endothelial stiffening and its association with increased endothelial angiogenic activity in vitro and formation of functional vessels in vivo suggest a potential role for endothelial biomechanics in cardiovascular disease
