Targeting Mast Cells in Post-Traumatic Joint Rehabilitation and Osteoarthritis

许多退伍军人和平民遭受创伤性关节损伤，这往往导致康复不良 结果、关节功能障碍和损伤关节中骨关节炎（OA）的发展。现有的治疗方法 关节损伤和OA仅减轻症状，而在促进愈合或预防OA方面无效。 越来越多的证据表明，关节损伤后的"低度"炎症与不良康复结果有关， 和创伤后OA的最终发展。更好地了解潜在的炎症 靶向失调途径的药理学机制和鉴定可以改变 护理和康复的军事人员，退伍军人，和平民与创伤性关节损伤。我们 初步研究表明，肥大细胞在介导关节炎性反应中起关键作用， 损伤和促进创伤后OA的发展。在本建议中，我们的目的是阐明 肥大细胞在关节损伤后的不良康复结果和创伤后OA的发展中的作用。 肥大细胞在OA滑膜以及创伤后非OA关节中被检测到，并且能够产生 促炎和降解介质。我们发现肥大细胞介质的过度表达，包括肥大 细胞特异性胰蛋白酶，在滑膜和关节损伤或OA患者的体液中。数据来自两 小鼠模型表明，缺乏肥大细胞会减弱OA相关的病理，而植入肥大细胞则会减弱OA相关的病理。 肥大细胞恢复了这种表型。肥大细胞活化的药理学抑制证实了这些结果。 我们的体外研究表明类胰蛋白酶诱导OA发病机制中不可或缺的几个过程： 人软骨，关节软骨细胞凋亡，促炎反应和增殖， 滑膜成纤维细胞。此外，我们发现由Fc ε RI、Syk和组胺释放介导的IgE信号传导， 因子（HRF）参与创伤后OA的发病机制。尽管如此， 关于关节创伤后肥大细胞激活的上游机制，以及在OA中， IgE，以及靶向肥大细胞通路或产物是否可能改善康复和预防OA。我们 假设关节损伤后，IgE介导肥大细胞活化，包括Fc ε RI、Syk和HRF 促进炎症，从而损害康复并加速OA的发展。我们还 假设损伤诱导关节和软骨分解产物导致IgE反应和/或 产生激活肥大细胞的HRF，并且可以鉴定生物标志物以指导药理学 靶向肥大细胞以促进成功康复并预防创伤后OA的发展。 为了验证这些假设，在目标1中，我们提出了肥大细胞活化，脱粒， 生物标志物在人类关节损伤后，在康复，和在OA。在目标2中，我们将描述IgE 在关节损伤、康复和OA中的反应。在目标3中，我们将确定可实现以下目标的战略 肥大细胞途径改善关节损伤后的康复结果并预防继发性OA 内侧半月板（DMM）小鼠模型的不稳定。重要的是，Aim 3将专注于FDA批准的 靶向肥大细胞的药物，从而提供了一种快速翻译和评估有前途的 候选人在促进成功的康复结果和预防发展的功效 人类关节损伤后继发性OA。如果成功，该提案将阐明肥大细胞的作用 和IgE在关节损伤后的康复结果和OA发展中的作用（目的1和2），建立 生物标志物，以识别可能患有肥大细胞介导的不良康复结果的个体 和创伤后OA（目标1和2），并确定候选药物干预措施，目标肥大细胞 细胞，以促进成功的康复和最佳的功能结果（目标3）。

Many Veterans and civilians sustain traumatic joint injuries, which frequently lead to poor rehabilitation outcomes, joint dysfunction, and development of osteoarthritis (OA) in the injured joint. Existing treatments for joint injury and OA only alleviate symptoms, and are ineffective in promoting healing or preventing OA. Increasing evidence implicates “low-grade” inflammation following joint injury in poor rehabilitation outcomes, and in the eventual development of post-traumatic OA. A better understanding of the underlying inflammatory mechanisms and identification of pharmacologic agents that target the dysregulated pathways could transform the care and rehabilitation for military personnel, Veterans, and civilians with traumatic joint injuries. Our preliminary studies suggest a critical role for mast cells in mediating inflammatory responses following joint injury and in promoting the development of post-traumatic OA. In this proposal, we aim to elucidate the roles of mast cells in poor rehabilitation outcomes following joint injury and in the development of post-traumatic OA. Mast cells are detected in OA synovium as well as in post-trauma non-OA joints, and are capable of producing pro-inflammatory and degradative mediators. We found overexpression of mast cell mediators, including mast cell-specific tryptases, in synovial membranes and fluids from individuals with joint injury or OA. Data from two mouse models indicated that lack of mast cells attenuated OA-related pathologies, whereas engraftment of mast cells restored this phenotype. Pharmacologic inhibition of mast cell activation confirmed these results. Our in vitro studies showed that tryptase induces several processes integral to OA pathogenesis: degeneration of human cartilage, apoptosis of articular chondrocytes, and pro-inflammatory responses and proliferation of synovial fibroblasts. Further, we found that IgE signaling mediated by FcεRI, Syk, and histamine-releasing factor (HRF) is involved in the pathogenesis of post-traumatic OA. Nevertheless, important questions remain about the upstream mechanisms underlying mast cell activation following joint trauma and in OA, the role of IgE, and whether targeting mast cell pathways or products might improve rehabilitation and prevent OA. We hypothesize that following joint injury, IgE-mediated activation of mast cells involving FcεRI, Syk, and HRF promotes inflammation, which impairs rehabilitation and accelerates the development of OA. Further, we hypothesize that injury-induced joint and cartilage breakdown products lead to an IgE response and/or production of HRF that activates mast cells, and that biomarkers can be identified to guide pharmacologic targeting of mast cells to promote successful rehabilitation and prevent the development of post-traumatic OA. To test these hypotheses, in Aim 1, we propose to characterize mast cell activation, degranulation, and biomarkers in human joints post-injury, in rehabilitation, and in OA. In Aim 2, we will characterize the IgE response in joint injury, rehabilitation, and OA. In Aim 3, we will identify strategies that pharmacologically target mast cell pathways to improve rehabilitation outcomes and to prevent secondary OA following joint injury in the destabilization of the medial meniscus (DMM) mouse model. Importantly, Aim 3 will focus on FDA-approved drugs that target mast cells, thereby providing a path for rapid translation and evaluation of promising candidates for efficacy in promoting successful rehabilitation outcomes and preventing development of secondary OA following joint injury in humans. If successful, the proposal will elucidate the roles of mast cells and IgE in rehabilitation outcomes and development of OA following joint injury (Aims 1 and 2), establish biomarkers to identify individuals who are likely to suffer from mast-cell-mediated poor rehabilitation outcomes and post-traumatic OA (Aims 1 and 2), and identify candidate pharmacologic interventions that target mast cells to promote successful rehabilitation and optimal functional outcomes (Aim 3).