School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, United States.
Exp Cell Res. 2013 Mar 10;319(5):684-96. doi: 10.1016/j.yexcr.2012.11.017. Epub 2012 Dec 7.
Multipotent human mesenchymal stem cells (hMSCs) are uniquely suited for the growing field of regenerative medicine due to their ease of isolation, expansion, and transplantation. However, during ex vivo expansion necessary to obtain clinically relevant cell quantities, hMSCs undergo fundamental changes culminating in cellular senescence. The molecular changes as hMSCs transition into senescence have been well characterized, but few studies have focused on the mechanical properties that govern many processes necessary for therapeutic efficacy. We show that before detectable differences in classical senescence markers emerge, single-cell mechanical and cytoskeletal properties reveal a subpopulation of 'non-functioning' hMSCs that appears after even limited expansion. This subpopulation, characterized by a loss of dynamic cytoskeletal stiffening and morphological flexibility in response to chemotactic signals grows with extended culture resulting in overall decreased hMSC motility and ability to contract collagen gels. These changes were mitigated with cytoskeletal inhibition. Finally, a xenographic wound healing model was used to demonstrate that these in vitro differences correlate with decreased ability of hMSCs to aid in wound closure in vivo. These data illustrate the importance of analyzing not only the molecular markers, but also mechanical markers of hMSCs as they are investigated for potential therapeutics.
多能人类间充质干细胞（hMSCs）由于其易于分离、扩增和移植，非常适合不断发展的再生医学领域。然而，在获得临床相关细胞数量所需的体外扩增过程中，hMSCs 会发生根本性变化，最终导致细胞衰老。hMSCs 向衰老过渡时的分子变化已经得到了很好的描述，但很少有研究关注决定治疗效果的许多必要过程的力学特性。我们表明，在可检测到经典衰老标志物出现之前，单细胞力学和细胞骨架特性就揭示了一个“非功能”hMSC 的亚群，即使是在有限的扩增后也会出现这种亚群。这个亚群的特点是，在对趋化信号的反应中，动态细胞骨架变硬和形态灵活性丧失，在延长培养后会导致 hMSC 整体迁移能力和收缩胶原凝胶的能力下降。用细胞骨架抑制可以缓解这些变化。最后，使用异种动物伤口愈合模型证明，这些体外差异与 hMSC 减少体内协助伤口闭合的能力相关。这些数据表明，在研究 hMSC 作为潜在治疗方法时，不仅要分析分子标志物，还要分析 hMSC 的力学标志物。
