Impacts of mechanosensation and matrix architecture on cell fate specification in traumatic heterotopic ossification

项目摘要 异位骨化(HO)是骨外骨骼的病理形成，几乎完全形成于 约20%的髋关节置换术后患者会出现机械应力部位、烧伤或肌肉骨骼损伤。 目前，还没有疗法或基于物理疗法的方案来预防HO。在这方面，存在一个空白。 在我们对这一衰弱过程背后的致病机械传导途径的理解中。我们的 从HO位点恢复的小鼠HO-间充质祖细胞(MPC)的无偏转录谱 结合小鼠和人HO的免疫染色显示，一系列机械转导与 包括盘状物受体2(DDR2)、FAK和河马效应器YAP和TAZ在内的通路高度依赖于 随着观察到的细胞外基质(ECM)排列的变化而上调。使用一种新颖的、地区性的 MPC特异的可诱导CRE系统(Hoxa11-CreERT2)，我们已经汇编了支持关键的 DDR2信号和阶段特异性固定化在触发FAK/YAP/TAZ信号和MPC中的作用 血统承诺，但也是控制ECM对齐的一个意想不到的功能。加在一起，这些 观察结果导致了我们的中心假设，即MPC DDR2信号是移动诱导的必需信号 触发HO部位异常骨软骨分化的ECM排列改变，并可被以下物质阻断 DDR2抑制或损伤阶段特异性固定。 目标1：确定DDR2作为FAK/YAP/TAZ信号的关键上游调节因子在控制 HO的诱导和发展。我们假设DDR2-机械转导信号会改变 体内的骨软骨分化和HO，可以通过细胞特异性缺失模型或翻译来靶向 临床疗法。 目标2：确定损伤后MPC可以重新定向离开的最佳时间 通过基于制动的干预，异常的骨软骨命运和病理ECM对齐。 我们假设，在损伤后早期增殖阶段的固定将阻止病理变化。 在ECM中，MPC命运决定和异常骨化具有改善疾病的作用。 目的3：描述动员诱导的DDR2激活在胶原排列/各向异性中的作用 和机械传导信号。我们假设DDR2活动独立地驱动ECM对齐 活体肢体活动度或体外循环拉伸。 影响：拟议的研究将提供对DDR2和 关节活动度通过条件缺失模型和临床治疗来调节细胞外基质的排列、细胞命运和HO。

Project Summary Heterotopic ossification (HO) is the pathologic formation of extra-skeletal bone forming almost exclusively at sites of mechanical stress, that occurs in ~20% of patients after hip arthroplasty, burns or musculoskeletal injury. Currently, no therapeutics or physical therapy-based protocols exist to prevent HO. In this regard, there is a void in our understanding of the causative mechanotransductive pathways behind this debilitating process. Our unbiased transcription profiles in mouse HO-mesenchymal progenitor cells (MPCs) recovered from HO sites in combination with immunostaining of mouse and human HO revealed that a series of mechanotranduction-linked pathways, including discoidin receptor 2 (DDR2), FAK and the Hippo effectors, YAP and TAZ, are highly upregulated in tandem with observed changes in extracellular matrix (ECM) alignment. Using a novel, regional MPC-specific inducible Cre system (Hoxa11-CreERT2), we have compiled preliminary data that support critical roles for DDR2 signaling and stage-specific immobilization in both triggering FAK/YAP/TAZ signaling and MPC lineage commitment, but also an unexpected function in controlling ECM alignment. Together, these observations have led to our central hypothesis that MPC DDR2 signaling is necessary for mobility-induced changes in ECM alignment that trigger aberrant osteochondral differentiation at HO sites and can be blocked by DDR2 inhibition or injury stage-specific immobilization. Aim 1: Define the role of DDR2 as a critical upstream regulator of FAK/YAP/TAZ signaling in controlling the induction and progression of HO. We hypothesize that DDR2-mechanotransductive signaling alters osteochondral differentiation and HO in vivo and can be targeted with cell specific deletion models or translatable clinical therapies. Aim 2: Determine the optimal post-injury timing during which MPCs can be redirected away from aberrant osteochondral fate and pathologic ECM alignment through immobilization-based intervention. We hypothesize that immobilization during the early proliferative phase after injury will block pathologic changes in ECM alignment with disease-ameliorating effects on MPC fate determination and aberrant ossification. Aim 3: Characterize the role of mobilization-induced DDR2 activation on collagen alignment/anisotropy and mechanotransductive signaling. We hypothesize that DDR2 activity drives ECM alignment independently of limb mobility in vivo or cyclic stretch in vitro. Impact: The proposed studies will provide a comprehensive and mechanistic understanding of how DDR2 and joint mobility regulate ECM alignment, cell fate and HO using conditional deletion models and clinical therapies.