State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.
Acta Biomater. 2018 Oct 1;79:83-95. doi: 10.1016/j.actbio.2018.08.018. Epub 2018 Aug 19.
It is generally recognised that mesenchymal stem cells (MSCs) can differentiate into multiple lineages through guidance from the biophysical properties of the substrates. However, the precise biophysical mechanism that enables MSCs to respond to substrate properties remains unclear. In the current study, polydimethylsiloxane (PDMS) substrates with different stiffnesses were fabricated and the way in which the elastic modulus of the substrate regulated differentiation towards osteogenesis and adipogenesis in adipose-derived stromal cells (ASCs) was explored. Initially, a cell morphology change by SEM was observed between the stiff and soft substrates. The cytoskeleton stains including microfilament by F-actin and microtubule by α- and β-tubulin further showed a larger cell spreading area on the stiff substrate. Then the expression of vinculin, in charge for the linkage of adhesion molecules to the actin cytoskeleton, was enhanced on the stiff substrate. This change in focal adhesion plaque further triggered intracellular β-catenin signaling and promoted its nuclear translocation especially on the stiff substrate. The influence of β-catenin signaling on direct differentiation to osteogenic lineages was through direct binding between its downstream protein, Lef-1, and the osteogenic transcriptional factors, Runx2 and Osx, while on differentiation to adipogenic lineages was through modulating the expression of PPARγ. The imbalance of stiffness-induced β-catenin signaling finally induced a stronger osteogenesis and a weaker adipogenesis on the stiff substrate relative to those on the soft substrate. This study indicates the importance of stiffness on ASC differentiation and could help to increase understanding of the mechanism underlying molecular signal transduction from mechanosensing, mechanotransducing to stem cell differentiation.
Mesenchymal stem cells can differentiate into multiple lineages, such as adipogenesis, myogenesis, neurogenesis, angiogenesis and osteogenesis, through influence of biophysical properties of the extracellular matrix. However, the precise bio-mechanism that triggers stem cell differentiation in response to matrix biophysical properties remains unclear. In the current study, we provide a series of experiments involving the characterization of cell morphology, microfilament, microtubule and adhesion capacity of adipose-derived stromal cells (ASCs) in response to substrate stiffness, and further elucidation of cytoplasmic β-catenin-dependent signal transduction, nuclear translocation and resultant promoter activation of transcriptional factors for osteogenesis and adipogenesis. This study provides an explanation on deeper understanding of bio-mechanism underlying substrate stiffness-triggered β-catenin signal transduction from active mechanosensing, mechanotransducing to stem cell differentiation.
人们普遍认为，间充质干细胞（MSCs）可以通过基质的生物物理特性的指导分化为多个谱系。然而，确切的生物物理机制使 MSCs 能够响应基质特性仍不清楚。在本研究中，制备了具有不同硬度的聚二甲基硅氧烷（PDMS）基底，并探索了基底弹性模量调节脂肪来源基质细胞（ASCs）向成骨和成脂分化的方式。最初，通过 SEM 观察到在硬基底和软基底之间细胞形态的变化。细胞骨架染色，包括 F-肌动蛋白微丝和 α-和 β-微管蛋白微管，进一步显示在硬基底上有更大的细胞铺展面积。然后，负责将黏附分子与肌动蛋白细胞骨架连接的黏着斑蛋白 vinculin 在硬基底上表达增强。黏附斑的这种变化进一步触发了细胞内β-连环蛋白信号转导，并促进其核转位，特别是在硬基底上。β-连环蛋白信号转导对直接向成骨谱系分化的影响是通过其下游蛋白 Lef-1 与成骨转录因子 Runx2 和 Osx 之间的直接结合，而对向成脂谱系分化的影响是通过调节 PPARγ 的表达。刚度诱导的β-连环蛋白信号的失衡最终导致在硬基底上的成骨作用较强，而在软基底上的成脂作用较弱。本研究表明了硬度对 ASC 分化的重要性，并有助于增加对从机械感受、机械转导到干细胞分化的分子信号转导机制的理解。
间充质干细胞可以通过细胞外基质的生物物理特性的影响分化为多个谱系，如成脂、成肌、神经发生、血管生成和成骨。然而，触发干细胞分化以响应基质生物物理特性的确切生物力学机制尚不清楚。在本研究中，我们进行了一系列实验，涉及细胞形态、微丝、微管和脂肪来源基质细胞（ASCs）对基质刚度的反应的黏附能力的表征，进一步阐明了细胞质β-连环蛋白依赖性信号转导、核转位和随后的成骨和成脂转录因子的启动子激活。本研究提供了一个解释，说明更深层次地理解基质刚度触发β-连环蛋白信号转导的生物力学机制，从主动机械感受、机械转导到干细胞分化。
