Differentiation of human bone marrow-derived mesenchymal stem cells (hMSCs) is regulated by a variety of cues of their surrounding microenvironments. In particular, mechanical properties of cell culture matrices have been recently disclosed to play a pivotal role in stem cell differentiation. However, it remains elusive how viscosity affects the chondrogenic differentiation of hMSCs during three-dimensional (3D) culture. In this study, a 3D culture system that was established by embedding viscous gelatin solution in chemically cross-linked gelatin hydrogels was used for 3D culture of hMSCs in gelatin solutions with different viscosities. The influence of solution viscosity on chondrogenic differentiation of hMSCs was investigated. Viscous gelatin solutions promoted cell proliferation in the order of low, middle and high viscosity while elastic hydrogels restricted cell proliferation. High viscosity gelatin solution led to increased production of the cartilaginous matrix. Under the synergistic stimulation of chondrogenic induction factors, high viscosity was beneficial for the chondrogenic differentiation of hMSCs. The results suggested the role of viscosity should be considered as one of the dominant mechanical cues affecting stem cell differentiation.

人骨髓源间充质干细胞（hMSCs）的分化受周围微环境的各种提示调节。特别地，最近已经公开了细胞培养基质的机械性质在干细胞分化中起关键作用。但是，仍然不清楚如何在三维（3D）培养过程中粘度如何影响hMSC的软骨分化。在这项研究中，通过将粘性明胶溶液嵌入化学交联的明胶水凝胶中而建立的3D培养系统用于在具有不同粘度的明胶溶液中进行hMSC的3D培养。研究了溶液粘度对hMSCs成软骨分化的影响。粘性明胶溶液以较低的顺序促进细胞增殖，中高粘度，而弹性水凝胶限制细胞增殖。高粘度明胶溶液导致软骨基质的产量增加。在软骨诱导因子的协同刺激下，高粘度有利于hMSCs的软骨分化。结果表明粘度的作用应被视为影响干细胞分化的主要机械提示之一。