Yang Chun, DelRio Frank W, Ma Hao, Killaars Anouk R, Basta Lena P, Kyburz Kyle A, Anseth Kristi S
Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, CO 80303; BioFrontiers Institute, University of Colorado Boulder, Boulder, CO 80303;
Material Measurement Laboratory, National Institute of Standards and Technology, Boulder, CO 80305;
Proc Natl Acad Sci U S A. 2016 Aug 2;113(31):E4439-45. doi: 10.1073/pnas.1609731113. Epub 2016 Jul 19.
There is a growing appreciation for the functional role of matrix mechanics in regulating stem cell self-renewal and differentiation processes. However, it is largely unknown how subcellular, spatial mechanical variations in the local extracellular environment mediate intracellular signal transduction and direct cell fate. Here, the effect of spatial distribution, magnitude, and organization of subcellular matrix mechanical properties on human mesenchymal stem cell (hMSCs) function was investigated. Exploiting a photodegradation reaction, a hydrogel cell culture substrate was fabricated with regions of spatially varied and distinct mechanical properties, which were subsequently mapped and quantified by atomic force microscopy (AFM). The variations in the underlying matrix mechanics were found to regulate cellular adhesion and transcriptional events. Highly spread, elongated morphologies and higher Yes-associated protein (YAP) activation were observed in hMSCs seeded on hydrogels with higher concentrations of stiff regions in a dose-dependent manner. However, when the spatial organization of the mechanically stiff regions was altered from a regular to randomized pattern, lower levels of YAP activation with smaller and more rounded cell morphologies were induced in hMSCs. We infer from these results that irregular, disorganized variations in matrix mechanics, compared with regular patterns, appear to disrupt actin organization, and lead to different cell fates; this was verified by observations of lower alkaline phosphatase (ALP) activity and higher expression of CD105, a stem cell marker, in hMSCs in random versus regular patterns of mechanical properties. Collectively, this material platform has allowed innovative experiments to elucidate a novel spatial mechanical dosing mechanism that correlates to both the magnitude and organization of spatial stiffness.
人们越来越认识到基质力学在调节干细胞自我更新和分化过程中的功能作用。然而，局部细胞外环境中亚细胞水平的空间力学变化如何介导细胞内信号转导并决定细胞命运，在很大程度上尚不清楚。在此，研究了亚细胞基质力学特性的空间分布、大小和组织对人间充质干细胞（hMSCs）功能的影响。利用光降解反应，制备了一种水凝胶细胞培养底物，其具有空间变化且不同力学特性的区域，随后通过原子力显微镜（AFM）对这些区域进行了映射和量化。发现潜在基质力学的变化可调节细胞黏附及转录事件。在接种于具有较高浓度刚性区域水凝胶上的hMSCs中，观察到细胞高度铺展、呈细长形态，且Yes相关蛋白（YAP）激活程度更高，呈剂量依赖性。然而，当机械刚性区域的空间组织从规则模式变为随机模式时，hMSCs中YAP激活水平降低，细胞形态更小且更圆。从这些结果我们推断，与规则模式相比，基质力学的不规则、无序变化似乎会破坏肌动蛋白组织，并导致不同的细胞命运；这一点通过观察发现随机模式与规则模式力学特性下hMSCs中碱性磷酸酶（ALP）活性较低以及干细胞标志物CD105表达较高得到了验证。总体而言，这个材料平台使得创新性实验得以阐明一种与空间刚度的大小和组织相关的新型空间力学剂量机制。
