Peyton Shelly R, Raub Christopher B, Keschrumrus Vic P, Putnam Andrew J
Department of Chemical Engineering and Materials Science, The Henry Samueli School of Engineering, University of California, Irvine, CA 92697-2575, USA.
Biomaterials. 2006 Oct;27(28):4881-93. doi: 10.1016/j.biomaterials.2006.05.012. Epub 2006 Jun 9.
Hydrogels based on poly(ethylene glycol) (PEG) are of increasing interest for regenerative medicine applications and are ideal materials to direct cell function due to the ability to confer key functionalities of native extracellular matrix (ECM) on PEG's otherwise inert backbone. Given extensive recent evidence that ECM compliance influences a variety of cell functions, PEG-based hydrogels are also attractive due to the ease with which their mechanical properties can be controlled. In these studies, we exploited the chemical and mechanical tunability of PEG-based gels to study the impact of ECM chemistry and mechanics on smooth muscle cells (SMCs) in both 2-D and 3-D model systems. First, by controlling the extent of crosslinking and therefore the mechanical properties of PEG-based hydrogels (tensile moduli from 13.7 to 423.9kPa), we report here that the assembly of F-actin stress fibers and focal adhesions, indicative of the state of actin contractility, were influenced by the compliance of 2-D PEG gels functionalized with either short adhesive peptides or full-length ECM proteins. Varying ECM ligand density and identity independent of gel compliance affected the physical properties of the focal adhesions, and also influenced SMC spreading in 2-D. Furthermore, SMCs proliferated to a greater extent as gel stiffness was increased. In contrast, the degree of SMC differentiation, which was qualitatively assessed by the extent of smooth muscle alpha-actin bundling and the association of calponin and caldesmon with the alpha-actin fibrils, was found to decrease with substrate stiffness in 2-D cultures. In 3-D, despite the fact that their viability and degree of spreading were greatly reduced, SMCs did express some contractile markers indicative of their differentiated phenotype when cultured within PEG-RGDS constructs. Combined, these data suggest that the mechanical and chemical properties of PEG hydrogels can be tuned to influence SMC phenotype in both 2-D and 3-D.
基于聚乙二醇（PEG）的水凝胶在再生医学应用中越来越受到关注，由于能够将天然细胞外基质（ECM）的关键功能赋予原本惰性的PEG主链，因此是指导细胞功能的理想材料。鉴于最近有大量证据表明ECM的顺应性会影响多种细胞功能，基于PEG的水凝胶因其机械性能易于控制也具有吸引力。在这些研究中，我们利用基于PEG的凝胶的化学和机械可调性，在二维和三维模型系统中研究ECM化学和力学对平滑肌细胞（SMC）的影响。首先，通过控制交联程度从而控制基于PEG的水凝胶的机械性能（拉伸模量从13.7至423.9kPa），我们在此报告，F-肌动蛋白应力纤维和粘着斑的组装（这是肌动蛋白收缩状态的指标）受到用短粘附肽或全长ECM蛋白功能化的二维PEG凝胶顺应性的影响。与凝胶顺应性无关地改变ECM配体密度和种类会影响粘着斑的物理性质，并且也会影响二维中SMC的铺展。此外，随着凝胶硬度的增加，SMC增殖程度更大。相比之下，在二维培养中，通过平滑肌α-肌动蛋白成束程度以及钙调蛋白和钙调素与α-肌动蛋白原纤维的关联进行定性评估的SMC分化程度，被发现会随着底物硬度的增加而降低。在三维中，尽管它们的活力和铺展程度大大降低，但当在PEG-RGDS构建体中培养时，SMC确实表达了一些表明其分化表型的收缩标记。综合这些数据表明，可以调节PEG水凝胶的机械和化学性质以在二维和三维中影响SMC表型。
