Xue Xufeng, Hong Xiaowei, Li Zida, Deng Cheri X, Fu Jianping
Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
Biomaterials. 2017 Jul;134:22-30. doi: 10.1016/j.biomaterials.2017.04.039. Epub 2017 Apr 22.
Human mesenchymal stem cells (hMSCs) have great potential for cell-based therapies for treating degenerative bone diseases. It is known that mechanical cues in the cell microenvironment play an important role in regulating osteogenic (bone) differentiation of hMSCs. However, mechanoregulation of lineage commitment of hMSCs in conventional two-dimensional (2D) monocultures or bioengineered three-dimensional (3D) tissue constructs remains suboptimal due to complex biomaterial design criteria for hMSC culture. In this study, we demonstrate the feasibility of a novel cell mechanics and mechanobiology tool, acoustic tweezing cytometry (ATC), for mechanical stimulation of hMSCs. ATC utilizes ultrasound (US) pulses to actuate functionalized lipid microbubbles (MBs) which are covalently attached to hMSCs via integrin binding to exert forces to the cells. ATC stimulation increases cytoskeletal contractility of hMSCs regardless of the cell area. Furthermore, ATC application rescues osteogenic differentiation of hMSCs in culture conditions that are intrinsically repressive for hMSC osteogenesis (e.g., soft cell culture surfaces). ATC application activates transcriptional regulator YAP to enhance hMSC osteogenesis. Our data further show that F-actin, myosin II, and RhoA/ROCK signaling functions upstream of YAP activity in mediating ATC-stimulated hMSC osteogenesis. With the capability of applying controlled dynamic mechanical stimuli to cells, ATC provides a powerful tool for mechanoregulation of stem cell behaviors in tissue engineering and regenerative medicine applications.
人间充质干细胞（hMSCs）在用于治疗退行性骨疾病的细胞疗法方面具有巨大潜力。众所周知，细胞微环境中的机械信号在调节hMSCs的成骨（骨）分化中起着重要作用。然而，由于hMSC培养的复杂生物材料设计标准，在传统的二维（2D）单培养或生物工程三维（3D）组织构建物中，hMSCs谱系定向的机械调节仍然不够理想。在本研究中，我们证明了一种新型细胞力学和机械生物学工具——声镊细胞术（ATC）对hMSCs进行机械刺激的可行性。ATC利用超声（US）脉冲驱动功能化脂质微泡（MBs），这些微泡通过整合素结合与hMSCs共价连接，从而对细胞施加力。无论细胞面积大小，ATC刺激均可增加hMSCs的细胞骨架收缩性。此外，在对hMSC成骨本质上具有抑制作用的培养条件下（例如，柔软的细胞培养表面），应用ATC可挽救hMSCs的成骨分化。应用ATC可激活转录调节因子YAP以增强hMSC的成骨作用。我们的数据进一步表明，F-肌动蛋白、肌球蛋白II和RhoA/ROCK信号在介导ATC刺激的hMSC成骨过程中，在YAP活性的上游发挥作用。由于能够对细胞施加可控动态机械刺激，ATC为组织工程和再生医学应用中干细胞行为的机械调节提供了一个强大的工具。
