Mechno-regulation of genome function to direct stem cell fate

越来越多的病理情况与其机械环境的细胞感知不适当或有缺陷有关。成体间充质干细胞(MSCs)为许多再生治疗提供了一种很有前途的细胞来源，但对机械刺激如何转化为细胞内的调节信号的机制知之甚少。细胞行为在很大程度上受基因表达的调控，基因表达通过DNA的转录从细胞核内指导。DNA以染色质的形式包装在细胞核内。染色质的紧致状态会影响基因转录，并可能导致基因沉默。这种紧凑状态由许多组蛋白控制，并进一步受到核层的影响，核层是核内核膜内的纤维基质。这控制了位于细胞核边缘的DNA中的基因沉默，并通过蛋白质复合体(LINC复合体)连接到细胞骨架；细胞骨架为细胞提供结构。在干细胞分化的过程中，细胞核已经被证明是重塑的，核僵硬和核层改变；潜在地影响基因转录。此外，如果核的硬度以及核和细胞骨架之间的连接(LINC复合体)被调节，向核的力传递可能会发生变化。这个项目将解决核作为机械刺激传感器的概念。它还将解决这样的假设，即细胞核作为机械传感器的角色随着细胞沿着其分化路线的进展而改变。我们将研究机械刺激引起核组织和干细胞分化变化的机制。通过全面描述生物物理刺激的MSCs在分化过程中力学性质、蛋白质组成、核结构和表观遗传学特征的变化，我们将确定导致细胞机械敏感性改变的关键途径。这项工作的结果将对我们理解细胞对机械刺激的反应具有深远的影响，并将影响基于细胞的再生医学和肌肉骨骼修复的策略。

A growing number of pathological conditions are associated with inappropriate or defective cellular sensing of their mechanical environment. Adult mesenchymal stem cells (MSCs) provide a promising cell source for many regenerative therapies although relatively little is known concerning the mechanisms through which mechanical stimuli are transduced into regulatory signals within the cell.Cellular behaviour is largely regulated by gene expression, which is directed from within the nucleus through transcription of DNA. DNA is packaged within the nucleus as chromatin. The compaction state of chromatin impacts gene transcription, and can result in gene silencing. This compaction state is controlled by a number of histone proteins, and is further influenced by the nuclear lamina, a fibrillar matrix within the nucleus lining the inner nuclear membrane. This controls gene silencing in DNA situated near the edge of the nucleus, and is connected via a complex of proteins (the LINC complex) to the cytoskeleton; the cells skeleton which provides the cell with structure. During stem cell differentiation, the nucleus has been shown to remodel, with alterations to nuclear stiffness and the nuclear lamina; potentially influencing gene transcription. Furthermore, if the nucleus stiffness and the connections between the nucleus and cytoskeleton, the LINC complex, are modulated, force transfer to the nucleus may be altered.This project will address the concept that the nucleus acts as a sensor for mechanical stimuli. It will also address the hypothesis that the role of the nucleus as a mechanosensor changes as a cell progresses along its differentiation route. We will investigate the mechanisms through which mechanical stimuli can induce changes in nuclear organisation and stem cell differentiation. By fully characterising changes in the mechanical properties, protein composition, nuclear architecture and epigenetic signature of biophysically stimulated MSCs as they undergo differentiation, we will identify key pathways responsible for the alteration of cellular mechanosensitivity. These can then be targeted to repair defective mechanosensitivity in diseased or aged cells.The results of this work will have far reaching implications for our understanding of how cells respond to mechanical stimulation, and will impact strategies for cell based regenerative medicine and musculoskeletal repair.