School of Mechanical and Manufacturing Engineering, Materials Processing Research Centre, Dublin City University, Glasnevin, Dublin, Ireland.
J Biomed Mater Res A. 2010 Sep 15;94(4):1080-90. doi: 10.1002/jbm.a.32790.
Mechanically, poly(vinyl alcohol) (PVA)-based cryogels are extremely well suited for vascular tissue engineering applications. However, their surface properties lead to a slow rate of endothelialization, and the mode of cell attachment leaves the endothelium susceptible to removal under physiological shear stress conditions. In this study, abrupt and ramped disturbed shear stress conditions created by a turbulent orbital flow were used to examine endothelialization on PVA/gelatin cryogels. Cell proliferation rate and apoptosis were evaluated by fluorescent activated cell sorter (FACS) analysis, and the expression of cell-adhesion molecules was used to evaluate the response of cells on cryogels to static and shear conditions by real-time polymerase chain reaction (RT-PCR). Application of a ramped shear stress had a profound effect on endothelial cell proliferation (22.30 +/- 0.20-fold increase), necrosis (eliminated), apoptosis (1.04 +/- 0.18 increase), and overall facilitation of endothelialization while concomitantly increasing nitric oxide (NO) synthesis levels. Ramped shear stress was also effective in helping the retention of the endothelial cells on the cryogel surface, whereas abrupt application caused widespread removal. Under static conditions, Selectin-P expression decreased, whereas both inter-cellular adhesion molecule (ICAM) and platelet endothelial cell adhesion molecule (PECAM)-I expression increased on cryogels over a 10-day culture period. Under both shear stress conditions, Selectin-P expression was decreased both on cryogels and tissue culture polystyrene (TCPS). Controlled application of disturbed shear stress shortens endothelialization times on cryogel surfaces, in contrast to the established antiproliferative effect of shear stress caused by laminar flow, without compromising their functionality. This demonstrates how such mechanical stimuli can be exploited to alter cellular behavior and facilitate the required outcomes for tissue engineering applications.
从力学角度来看，基于聚乙烯醇（PVA）的冷冻凝胶非常适合用于血管组织工程应用。然而，其表面特性导致内皮细胞的增殖速度缓慢，细胞附着的方式使内皮细胞容易在生理剪切力条件下被去除。在这项研究中，通过使用湍流轨道流来创建突然和渐变的扰动脉冲剪切力条件，研究了 PVA/明胶冷冻凝胶上的内皮细胞化。通过荧光激活细胞分选（FACS）分析评估细胞增殖率和细胞凋亡，通过实时聚合酶链反应（RT-PCR）评估细胞粘附分子的表达，以评估细胞对冷冻凝胶在静态和剪切条件下的反应。渐变剪切力的应用对内皮细胞的增殖有深远的影响（增加 22.30 +/- 0.20 倍），对坏死（消除）、凋亡（增加 1.04 +/- 0.18 倍）和整体内皮化的促进作用，同时增加一氧化氮（NO）的合成水平。渐变剪切力也有助于保留内皮细胞在冷冻凝胶表面上，而突然施加的剪切力则会导致广泛的去除。在静态条件下，选择素-P 的表达减少，而在 10 天的培养过程中，细胞间粘附分子（ICAM）和血小板内皮细胞粘附分子（PECAM）-I 在冷冻凝胶上的表达均增加。在两种剪切力条件下，选择素-P 在冷冻凝胶和组织培养聚苯乙烯（TCPS）上的表达均减少。受控应用扰动脉冲剪切力可缩短冷冻凝胶表面的内皮细胞化时间，与层流引起的剪切力的已知抗增殖作用相反，而不会影响其功能。这表明机械刺激如何可以被利用来改变细胞行为并促进组织工程应用所需的结果。
