应力微环境调控MSCs迁移-成骨分化及Lamin A在其中的机制研究

A key challenge in skeletal disease treatment is how to improve the efficiency of bone remolding. We have devoted to study the mechanotransduction mechanism of MSCs (mesenchymal stem cells), and found that mechanical environment can modulate bone remolding by regulating the migration and osteogenic differentiation of MSCs. In 2013, the journal Science reported that extracellular matrix stiffness can direct stem cell differentiation by the nuclear lamina layer protein, named Lamin A. Recent studies also suggested that Lamin A modulated stem cell migration by regulating the nuclear skeleton stiffness and resilience, and proved the importance of the nucleus as mechanoreceptors in cell transport for the first time. Based on these clues, we further found that the migration ability of MSCs was highly related to their osteogenic differentiation ability. The MSCs with higher migration activity also presented with higher osteogenic differentiation potential, and is more adaptive to mechanical microenvironment by regulation the expression of Lamin A. It suggests that the Lamin A, microenvironment and stem cell differentiation are highly related, and provides a new ideal target to study mechanical control and bone remodeling. This project aims to establish an in vitro MSCs migration model, and study the relationship between stem cell migration, lineage differentiation and stress sensitivity. We also plan to study the regulation effects of mechanical environment on stem cell migration and osteogenic differentiation, and further study the regulation mechanism of Lamin A in this process by using gene transfection, RNA interference, dual luciferase and chromatin immunoprecipitation techniques.

骨重建效率不佳是骨骼疾患治疗的瓶颈。我们前期发现，应力微环境通过调控间充质干细胞MSCs迁移和分化来影响骨重建平衡，为提高骨重建效率提供了新思路。2013年Science报道核纤层蛋白Lamin A是基质硬度调节干细胞分化的力感受器；近期研究提示Lamin A通过调节核骨架硬度来调控干细胞迁移，首次揭示细胞核作为应力感受器对细胞运输的重要性。项目组在此基础上发现迁移能力高的MSCs成骨分化能力亦强，并在应力刺激下适应性上调Lamin A表达，证实Lamin A、应力微环境、干细胞分化之间存在密切关联，是研究应力调控与骨重建的理想靶标。本项目拟建立MSCs体外迁移模型，研究干细胞迁移、谱系分化及力敏感性的关系；明确体内、外应力微环境对其迁移-成骨分化调控效应；并以Lamin A为靶标，通过基因转染、RNA干扰、双荧光素酶、染色质免疫共沉淀芯片等，研究应力微环境对细胞迁移-成骨分化的调控机制。

骨骼相关疾病是我国第二大公共健康问题，干细胞迁移至局部组织并定向分化是骨折愈合及骨骼疾病骨重建的生理基础。而干细胞迁移过程会改变自身所处的力学环境和力学刺激。这些力学刺激可以参与调控间充质干细胞（mesenchymal stem cells, MSCs）募集、维持MSCs干性，并参与骨重建平衡调控。本项目通过Transwell筛选不同迁移能力MSCs，构建出稳定的筛选不同迁移能力MSCs的模型，并系统研究了MSCs的迁移能力与干细胞增殖、自我更新、分化能力的相关性，发现迁移能力高的MSCs增殖及成骨分化能力增强，但成脂分化能力减弱，并通过连续迁移实验予以证实。课题组进一步通过皮下异位成骨、骨缺损模型验证具有高迁移能力的MSCs促进骨质形成的能力更强。同时项目组发现迁移能力强的MSCs能更有效地参与骨质疏松患者骨重建过程，促进骨质恢复。此外，课题组发现力学刺激与细胞迁移存在偶联效应，即张应力刺激能够进一步上调迁移能力高的MSCs成骨分化能力。课题组进一步证实这一偶联效应与MSCs中Lamin A差异性表达有关，即应力刺激能通过调控Lamin A的表达影响不同迁移能力MSCs的分化能力，并可能与wnt/β-catenin的差异性表达有关。本项目表明MSCs的迁移能力与定向分化能力存在相关性，迁移能力高的MSCs在干细胞治疗及骨组织工程中可能具有更高的治疗价值；同时，本项目指出力学刺激与干细胞迁移能力存在偶联作用，并与共同调控Lamin A以及wnt/β-catenin有关。通过调控Lamin A能够促进应力微环境下的骨重建，提高骨修复效率。

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