Adhesion ligands and mechanical properties of extracellular matrix (ECM) play significant roles in directing mesenchymal stem cells' (MSCs) behaviors, but how they affect chondrogenic differentiation of MSCs has rarely been studied. In this study, we investigated the effects of matrix stiffness and adhesion ligand density on proliferation and chondrogenic differentiation of MSCs by using UV crosslinked hydrogels comprised of methacrylated gelatin (GelMA) and poly(ethylene glycol) diacrylate (PEGDA) of different weight ratios. The PEGDA/GelMA hydrogels were fabricated by adjusting the weight ratio of PEGDA and GelMA with low or high adhesion ligand density (0.05 and 0.5% GelMA, respectively) and independent tunable stiffness (1.6, 6, and 25 kPa separately for hydrogels with 5, 10, and 15% PEGDA). MSCs presented differential behaviors to ECM by adjusting its adhesion ligand density and stiffness. Cell proliferation and chondrogenic differentiation could be enhanced with the improvement of adhesive properties and stiffness, evidenced by cell viability assay, hematoxylin–eosin staining, Safranin O staining, immunohistochemistry (Collagen types II, Col2a1), as well as the chondrogenic genes expression of Col2a1, Acan, and Sox9. This study may provide new strategies to design the scaffolds for cartilage tissue engineering.

中文翻译：

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基质刚度和粘附配体密度对间充质干细胞成软骨分化的影响。

细胞外基质 (ECM) 的粘附配体和机械特性在指导间充质干细胞 (MSC) 的行为方面发挥着重要作用，但很少研究它们如何影响 MSC 的软骨分化。在这项研究中，我们通过使用由不同重量比的甲基丙烯酸化明胶 (GelMA) 和聚乙二醇二丙烯酸酯 (PEGDA) 组成的紫外线交联水凝胶，研究了基质刚度和粘附配体密度对 MSCs 增殖和软骨形成分化的影响。PEGDA/GelMA 水凝胶是通过调整具有低或高粘附配体密度（分别为 0.05 和 0.5% GelMA）和独立可调刚度（分别为 1.6、6 和 25 kPa，对于具有 5、 10 和 15% PEGDA）。MSCs 通过调整其粘附配体密度和刚度向 ECM 呈现不同的行为。通过细胞活力测定、苏木精-伊红染色、番红 O 染色、免疫组织化学（II 型胶原蛋白、Col2a1）以及Col2a1、Acan和Sox9。这项研究可能为设计用于软骨组织工程的支架提供新的策略。