Fibronectin (Fn) adsorption was studied on different commercial polymer surface chemistries, including tissue culture polystyrene (TCPS), bacteriologic polystyrene (BPS), fluoropolymer Teflon AF, and poly-L-lactide (PLLA). Antibody probes detected the availability of Fn's cell binding domain on adsorbed Fn in the competitive presence and absence of bovine serum albumin (BSA). Domain availability was highest for Fn adsorbed on TCPS, especially in the presence of either serum albumin or dilute serum. Attachment and growth efficiencies for human umbilical venous endothelial cells (HUVECs) cultured on surfaces preadsorbed with Fn in serum and serum-free media correlated with antibody cell-binding domain availability: TCPS > BPS, Teflon AF > PLLA. Intracellular signaling from the GTPase, RhoA, was highest (RhoA:RhoGDI inhibitor ratio) in cells cultured on the Teflon AF surfaces, indicating that despite lower attached cell numbers on Teflon AF compared to TCPS, cell signaling remained activated after 24 h of growth. Up-regulated cellular Fn mRNA messages, assessed using RT-PCR techniques, supported HUVECs' producing the endogenous extracellular matrix (ECM) protein Fn in order to attach and survive on the suboptimal Teflon AF culture surfaces.

Hemodynamic forces play an active role in vascular pathologies, particularly in relation to the localization of atherosclerotic lesions. It has been established that low shear stress combined with cyclic reversal of flow direction (oscillatory shear stress) affects the endothelial cells and may lead to an initiation of plaque development. The aim of the study was to analyze the effect of hemodynamic conditions in arterial segments perfused in vitro in the absence of other stimuli. Left common porcine carotid segments were mounted into an ex vivo arterial support system and perfused for 3 days under unidirectional high and low shear stress (6 +/- 3 and 0.3 +/- 0.1 dyn/cm(2)) and oscillatory shear stress (0.3 +/- 3 dyn/cm(2)). Bradykinin-induced vasorelaxation was drastically decreased in arteries exposed to oscillatory shear stress compared with unidirectional shear stress. Impaired nitric oxide-mediated vasodilation was correlated to changes in both endothelial nitric oxide synthase (eNOS) gene expression and activation in response to bradykinin treatment. This study determined the flow-mediated effects on native tissue perfused with physiologically relevant flows and supports the hypothesis that oscillatory shear stress is a determinant factor in early stages of atherosclerosis. Indeed, oscillatory shear stress induces an endothelial dysfunction, whereas unidirectional shear stress preserves the function of endothelial cells. Endothelial dysfunction is directly mediated by a downregulation of eNOS gene expression and activation; consequently, a decrease of nitric oxide production and/or bioavailability occurs.

Background: The aim of this study was to analyze the arterial wall response to plaque-prone hemodynamic environments, known to occur mainly in areas of arterial trees such as bifurcations and branching points. In these areas, the vasculature is exposed to cyclically reversing flow that induces an endothelial dysfunction predisposing thus arteries to local development of atherosclerotic plaques. Methods: We used an ex vivo perfusion system that allows culturing arterial segments under different hemodynamic conditions. Porcine carotid arteries were exposed for 3 days to unidirectional high and low shear stress (6 ± 3 and 0.3 ± 0.1 dyn/cm²) as well as to oscillatory shear stress (0.3 ± 3 dyn/cm²). This latter condition mimics the hemodynamics present at plaque-prone areas. At the end of the perfusion, the influence of different flow patterns on arterial metabolism was assessed in terms of matrix turnover as well as of smooth muscle cell function, differentiation and migration. Results: Our results show that after 3 days of perfusion none of the applied conditions influence smooth muscle cell phenotype retaining their full contraction capacity. However, an increase in the expression level of matrix metalloproteinase-2 and -9, as well as a decrease in plasminogen activator inhibitor-1 expression were observed in arteries exposed to oscillatory shear stress when compared to arteries exposed to unidirectional shear stress. Conclusion: These observations suggest that plaque-prone hemodynamic environment triggers a vascular wall remodelling process and promotes changes in arterial wall metabolism, with important implication in atherogenesis.

425articles nature publishing group BACKGROUND With advancing age arteries stiffen, reducing arterial compliance and leading to the development of systolic hypertension and to a substantial increase in pulse pressure. An augmented pulse pressure can be a predictor of the development of hypertension, which has been linked to several cardiovascular diseases including atherosclerosis, and to pathologies such as diabetes and renal dysfunction. In this study, we tested the hypothesis that reduced wall compliance induces pulse-pressure-mediated changes in arterial wall metabolism and remodeling. METHODSPorcine carotid arteries were perfused for 24 h using an ex vivo arterial support system. Control arteries were exposed to a pulse shear stress (6 ± 3 dynes/cm 2 ) combined with a pulse pressure of 80 ± 10 mm Hg, yielding a physiological cyclic stretch of 4-5%. A reduced compliance group was also studied, in which arteries were wrapped with an external band, thereby decreasing cyclic stretch to levels <1%. RESULTSThe experimentally reduced compliance caused a decreased contraction capacity induced by norepinephrine(NE), and this was associated with lower levels of α-smooth muscle cell-actin (α-SMC-actin) and desmin protein expressions. Arteries that were exposed to a reduced cyclic stretch exhibited a higher level of matrix metalloproteinase-2 (MMP-2) expression activity as well as an increase in Ki67 expression, thereby suggesting that matrix degradation and cellular proliferation had been initiated. Furthermore, the expression of plasminogen activator inhibitor-1 (PAI-1) in stiffened arteries was lower than in the control arteries. CONCLUSIONSThese findings underline the importance of cyclic stretch in the maintenance of a differentiated and fully functional phenotype of vascular SMCs, as well as in the regulation of migratory properties, proliferation, and matrix turnover.

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