Mechno-regulation of genome function to direct stem cell fate

越来越多的病理状况与其机械环境的不适当或有缺陷的细胞感知有关。成体间充质干细胞（MSCs）是一种有前途的再生治疗细胞来源，但其将机械刺激转化为细胞内调控信号的机制目前知之甚少，细胞行为主要受基因表达调控，基因表达由细胞核内的DNA转录调控。DNA作为染色质包装在细胞核内。染色质的致密状态影响基因转录，并可导致基因沉默。这种致密状态由许多组蛋白控制，并进一步受到核纤层的影响，核纤层是细胞核内内衬核膜的纤维基质。它控制位于细胞核边缘附近的DNA中的基因沉默，并通过蛋白质复合物（LINC复合物）连接到细胞骨架;细胞骨架为细胞提供结构。在干细胞分化过程中，细胞核已被证明会重塑，改变核硬度和核纤层;可能影响基因转录。此外，如果细胞核的刚度和细胞核与细胞骨架之间的连接，LINC复合体，被调制，力传递到细胞核可能会改变。本项目将解决的概念，细胞核作为一个传感器的机械刺激。它还将解决的假设，细胞核作为一个机械传感器的作用，随着细胞的进展沿着其分化路线的变化。我们将研究机械刺激诱导细胞核组织和干细胞分化的机制。通过充分表征生物刺激的MSC在分化过程中的机械特性、蛋白质组成、核结构和表观遗传特征的变化，我们将确定负责细胞机械敏感性改变的关键途径。这些可以有针对性地修复病变或老化细胞中有缺陷的机械敏感性。这项工作的结果将对我们理解细胞如何对机械刺激做出反应产生深远的影响，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.