Gravity-Vector Induces Mechanical Remodeling of rMSCs via Combined Substrate Stiffness and Orientation.
Gravity-Vector Induces Mechanical Remodeling of rMSCs via Combined Substrate Stiffness and Orientation.
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DOI：
10.3389/fbioe.2021.724101
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发表时间：
2021
影响因子：
5.7
通讯作者：
Long M
中科院分区：
文献类型：
--
作者：
Zhang C;Lü D;Zhang F;Wu Y;Zheng L;Zhang X;Li Z;Sun S;Long M
源自细胞微环境的独特物理因素对于干细胞的生物稳态至关重要。虽然已知基质硬度和方向分别调节间充质干细胞（MSC）的机械重塑和命运决定，但仍不清楚这两个因素如何结合起来操纵它们在重力矢量下的机械稳定性。在这里，我们通过将大鼠 MSC 以向上 (180°)、向下 (0°) 或侧向 (90°) 方向放置在刚度变化的聚二甲基硅氧烷 (PDMS) 基底上来量化这些综合效应。与玻璃盖玻片上的这些值相比，由于细胞核和细胞质之间的密度差异，在 2.5 MPa PDMS 基底上，核纵向易位在 0° 24 小时时较低，在 90° 24 和 72 小时时较高。在 0° 时，细胞受到显着减少的肌动蛋白和显着增强的波形蛋白表达的机械支撑。在 90° 时，增强的肌动蛋白和波形蛋白表达协同作用以维持细胞稳定性。具体而言，在 90° 2.5 MPa PDMS 上形成具有大量、低各向异性和可见核周波形蛋白索的核周肌动蛋白应力纤维 72 小时，支持核易位和整体细胞骨架表达的方向差异。这种方向依赖性往往在较软的 PDMS 上消失，在核易位和细胞骨架结构中呈现出独特的特征。此外，细胞形态和粘着斑主要受基底刚度的影响，随着刚度的降低，24 小时铺展面积增加，但 72 小时面积减少。从机制上讲，细胞倾向于通过 β1 整合素 - 粘着斑复合物 - 肌动蛋白机械敏感轴稳定在这些 PDMS 基底上。这些结果为理解基质刚度和方向的组合在定义 rMSC 的机械稳定性方面提供了见解。
Distinct physical factors originating from the cellular microenvironment are crucial to the biological homeostasis of stem cells. While substrate stiffness and orientation are known to regulate the mechanical remodeling and fate decision of mesenchymal stem cells (MSCs) separately, it remains unclear how the two factors are combined to manipulate their mechanical stability under gravity vector. Here we quantified these combined effects by placing rat MSCs onto stiffness-varied poly-dimethylsiloxane (PDMS) substrates in upward (180°), downward (0°), or edge-on (90°) orientation. Compared with those values onto glass coverslip, the nuclear longitudinal translocation, due to the density difference between the nucleus and the cytosol, was found to be lower at 0° for 24 h and higher at 90° for 24 and 72 h onto 2.5 MPa PDMS substrate. At 0°, the cell was mechanically supported by remarkably reduced actin and dramatically enhanced vimentin expression. At 90°, both enhanced actin and vimentin expression worked cooperatively to maintain cell stability. Specifically, perinuclear actin stress fibers with a large number, low anisotropy, and visible perinuclear vimentin cords were formed onto 2.5 MPa PDMS at 90° for 72 h, supporting the orientation difference in nuclear translocation and global cytoskeleton expression. This orientation dependence tended to disappear onto softer PDMS, presenting distinctive features in nuclear translocation and cytoskeletal structures. Moreover, cellular morphology and focal adhesion were mainly affected by substrate stiffness, yielding a time course of increased spreading area at 24 h but decreased area at 72 h with a decrease of stiffness. Mechanistically, the cell tended to be stabilized onto these PDMS substrates via β1 integrin–focal adhesion complexes–actin mechanosensitive axis. These results provided an insight in understanding the combination of substrate stiffness and orientation in defining the mechanical stability of rMSCs.