Deconstructing Cartilage Mechanotransduction by Piezo Channels

骨关节炎（OA）通过影响滑膜关节而引起疼痛和衰弱，并且在超过12%的人中发现。 美国25-74岁的总人口。OA的患病率随着年龄的增长而显著增加， 超过70%的65岁以上的人群有放射学证据。在我们社会的这个不断增长的部分，OA是 是造成残疾、脆弱和社会孤立的重要因素。尽管有巨大的社会经济影响 对于OA，没有可用的疾病修饰疗法。OA的显著特征是进行性， 关节软骨的形态、组成和机械性能的退行性变化。 关节软骨细胞中的机械传导是疾病发病机制的关键组成部分， 直接感知细胞的机械环境和由此导致的软骨代谢失衡之间的关系 在OA。我们最近发现了机械敏感性PIEZO离子通道-事实上， PIEZO 1和PIEZO 2都在关节软骨中表达，是关节炎中软骨细胞机械转导的基础。 对有害的机械压力的反应。 本研究的总体目标是确定压电介导的机械转导机制， 更深入地研究软骨细胞，以便这些见解可以用于疾病的发展- 修改关节负荷引起的损伤（包括OA）的方法。除了我们最近发现的 在软骨细胞压电介导的机械转导中，我们发现用 IL-1α（一种促炎细胞因子）的病理生理相关浓度增加了Piezo 1基因 Piezo 1的表达增加也存在于老化的骨关节炎软骨中 猪和人因此，该补助金的具体目的是：（1）确定协同作用的机制 Piezo 1/2在软骨细胞力学转导中的作用;（2）解构Piezo 1/2介导的 在炎症条件下软骨细胞的机械转导;（3）阐明压电- 在器官型软骨外植体和体内介导的机械转导。目标1将依赖于细胞研究。 我们将在电生理学、通道运输、有限元等水平上探索Piezo 1/2的协同作用。 建模和超微结构，后者还检查了来自OA与对照的人软骨。在Aim 2小学 猪软骨细胞将用IL-1α刺激以解构压电介导的机械转导。 目的3将依赖于猪骨软骨组织外植体和软骨细胞特异性和诱导性Piezo 1/2-/-小鼠， 我们产生的。将对细胞、外植体和动物施加各种模式的机械应力， 将进行压电介导的机械转导的功能丧失研究， 和翻译/治疗方向。提出的目标将扩展我们的初步发现与机制， 深入的研究，这将增加我们对OA的理解，在一个非增量的方式，这将激发 开发新的疾病缓解OA药物（DMOAD）。

Osteoarthritis (OA) is painful and debilitating by affecting the synovial joints, and is found in over 12% of the total United States population 25-74 years of age. The prevalence of OA increases significantly with age, with radiographic evidence in over 70% of the population over age 65. In this growing segment of our society, OA is a significant contributor to disability, frailty and social isolation. Despite the tremendous socioeconomic impact of OA, there are no disease-modifying therapies available. OA is distinctively characterized by the progressive, degenerative changes in the morphology, composition, and mechanical properties of articular cartilage. Mechanotransduction in articular chondrocytes is a key component of disease pathogenesis, given the link between direct sensing of the cells’ mechanical environment and the resulting metabolic imbalance of cartilage in OA. We have recently identified the mechanosensitive PIEZO ion channels - in fact a synergy between PIEZO1 and PIEZO2, both expressed in articular cartilage - to underlie chondrocyte mechanotransduction in response to injurious mechanical stress. The overall objective of this study is to define the mechanisms of Piezo-mediated mechanotransduction in chondrocytes more in-depth so that these insights can be leveraged toward the development of disease- modifying approaches in joint-loading-induced injuries, including OA. In addition to our recent discovery of chondrocytic Piezo-mediated mechanotransduction, we found that treatment of chondrocytes with pathophysiologically-relevant concentrations of IL-1α, a pro-inflammatory cytokine, increased Piezo1 gene expression, and that increased expression of Piezo1 was also present in osteoarthritic cartilage from aging pigs and humans. Thus, the Specific Aims of this grant are: (1) to determine the mechanisms of synergistic functioning of Piezo1/2 in chondrocyte mechanotransduction; (2) to deconstruct Piezo-mediated mechanotransduction in chondrocytes under inflammatory conditions; (3) to elucidate the role of Piezo- mediated mechanotransduction in organotypic cartilage explants and in-vivo. Aim 1 will rely on cellular studies. We will explore synergisms of Piezo1/2 at the levels of electrophysiology, channel trafficking, finite element modeling, and ultra-structure, the latter also examining human cartilage from OA vs controls. In Aim 2 primary porcine chondrocytes will be stimulated with IL-1α for deconstruction of Piezo-mediated mechanotransduction. Aim 3 will rely on porcine osteochondral explants and chondrocyte-specific and inducible Piezo1/2-/- mice which we have generated. Various modes of mechanical stress will be applied to cells, explants, and animals, and loss-of-function studies of Piezo-mediated mechanotransduction will be conducted with both mechanistic intent and translational/therapeutic direction. The proposed Aims will extend our initial discovery with mechanistic in- depth studies that will increase our understanding of OA in a non-incremental manner, and this will inspire the development of new Disease-Modifying OA Drugs (DMOADs).