Department of Chemical and Biological Engineering, University of Colorado, Boulder, Colorado, USA.
J Biomed Mater Res A. 2012 Jun;100(6):1375-86. doi: 10.1002/jbm.a.34104. Epub 2012 Mar 7.
Poly(ethylene glycol) (PEG) hydrogels, modified with RGD, are promising platforms for cell encapsulation and tissue engineering. While these hydrogels offer tunable mechanical properties, the extent of the host response may limit their in vivo applicability. The overall objective was to characterize the effects of hydrogel stiffness on the in vitro macrophage response and in vivo host response. We hypothesized that stiffer substrates induce better attachment, adhesion, and increased cell spreading, which elevates the macrophage classically activated phenotype and leads to a more severe foreign body reaction (FBR). PEG-RGD hydrogels were fabricated with compressive moduli of 130, 240, and 840 kPa, and the same RGD concentration. Hydrogel stiffness did not impact macrophage attachment, but elicited differences in cell morphology. Cells retained a round morphology on 130 kPa substrates, with localized and dense F-actin and localized α(V) integrin stainings. Contrarily, cells on stiffer substrates were more spread, with filopodia protruding from the cell, a more defined F-actin, and greater α(V) integrin staining. When stimulated with lipopolysaccharide, macrophages had a classical activation phenotype, with increased expression of TNF-α, IL-1β, and IL-6, however the degree of activation was significantly reduced with the softest hydrogels. A FBR ensued in response to all hydrogels when implanted subcutaneously in mice, but 28 days postimplantation the layer of macrophages at the implant surface was significantly lower in the softest hydrogels. In conclusion, hydrogels with lower stiffness led to reduced macrophage activation and a less severe and more typical FBR, and therefore are more suited for in vivo tissue engineering applications.
聚乙二醇（PEG）水凝胶经过 RGD 修饰后，是细胞包封和组织工程的有前途的平台。虽然这些水凝胶具有可调节的机械性能，但宿主反应的程度可能限制了它们在体内的适用性。总体目标是研究水凝胶硬度对体外巨噬细胞反应和体内宿主反应的影响。我们假设更硬的基质会诱导更好的附着、黏附和细胞铺展，从而提高巨噬细胞经典激活表型，并导致更严重的异物反应（FBR）。PEG-RGD 水凝胶的压缩模量分别为 130、240 和 840kPa，且 RGD 浓度相同。水凝胶硬度不会影响巨噬细胞的附着，但会引起细胞形态的差异。细胞在 130kPa 的基质上保持圆形形态，局部和密集的 F-肌动蛋白和局部α（V）整合素染色。相反，在较硬的基质上的细胞更伸展，有突出于细胞的丝状伪足，更明确的 F-肌动蛋白和更大的α（V）整合素染色。当用脂多糖刺激时，巨噬细胞具有经典的激活表型，TNF-α、IL-1β 和 IL-6 的表达增加，但在最柔软的水凝胶中，激活程度显著降低。当将所有水凝胶皮下植入小鼠时，都会引发 FBR，但在植入后 28 天，最柔软水凝胶的植入表面的巨噬细胞层明显较低。总之，硬度较低的水凝胶导致巨噬细胞激活减少，异物反应较轻且更典型，因此更适合体内组织工程应用。
