The Multiscale Role of Piezo Channels in Obesity-Associated Cartilage Damage

项目摘要 骨关节炎（OA）是一种使滑膜关节衰弱的疾病，是疼痛和残疾的主要原因 国际吧OA影响了超过3000万美国人，但没有疾病修饰药物。肥胖是一个主要的 OA的危险因素;然而，很难将低水平全身炎症的作用与 改变关节负荷与增加体重的影响。虽然软骨需要负荷来维持组织 体内平衡，以前的研究表明，由于体重增加导致的异常负荷可能解释了 为什么与健康体重相比，肥胖患者的软骨损伤率更高 个体然而，最近的许多研究表明，体重增加本身并不能解释OA 在人类和动物模型中，脂肪因子，来自身体脂肪的炎症介质， 在OA发病机制中的重要作用。此外，Guilak实验室以前的研究强调了 机械敏感离子通道Piezo 1和Piezo 2在软骨健康和维护中的重要性： 肥胖和OA相关的炎症介质白细胞介素1 α（IL-1α），调节和敏感压电 通道功能因此，该提议调查细胞因子/脂肪因子信号传导是否是 压电通道对机械力变得超敏，最终导致软骨细胞死亡增加。 这项提案的目的是直接研究肥胖相关炎症与肥胖之间的相互作用。 软骨细胞的机械敏感性。本研究旨在探讨机械感觉改变在发病机制中的作用， OA与肥胖的关系将导致靶向这些途径的最终目标，以开发新的治疗方法， 接近。具体目标1的重点是确定肥胖相关的炎症性疾病是否会改变Piezo 如果这种增加的表达转化为增加的软骨细胞对 机械载荷本研究针对肥胖症中关键的脂肪因子失调：IL-1α、瘦素、肿瘤坏死因子 因子α（TNF-α）和白细胞介素6（IL-6）。Specific Aim 2使用先前在美国开发的转基因小鼠， 实验室研究软骨细胞特异性Piezo 1和/或Piezo 2离子通道的丢失是否能保护软骨 在肥胖和关节损伤的体内模型中的损伤。具体地，小鼠将被喂食高脂肪饮食（60%脂肪）， 进行内侧半月板失稳（DMM）手术，已知会诱发创伤后OA。 这两个目标共同战略性地开发原子力显微镜（AFM）和钙（Ca 2+）成像技术 在体内评估软骨完整性，以补充基因修饰小鼠在模型中的使用， HFD叠加DMM损伤。这项研究的结果将有助于确定 肥胖影响软骨健康，最终导致OA疾病修饰药物的开发， 更广泛地应用于受压电离子通道的机械感觉改变影响的其他组织。

PROJECT SUMMARY Osteoarthritis (OA) is a debilitating disease of the synovial joints and is the leading cause of pain and disability worldwide. OA affects over 30 million Americans, but there are no disease modifying drugs. Obesity is a major risk factor for OA; however, it has been difficult to disentangle the role of low-level systemic inflammation from the effects of altered joint loading with increased body mass. While cartilage requires loading to maintain tissue homeostasis, previous studies have suggested that abnormal loading due to increased body mass may explain why individuals with obesity experience cartilage damage at elevated rates when compared to healthy weight individuals. However, many recent studies demonstrate that increased body mass alone does not explain OA damage in human and animal models, and that adipokines, inflammatory mediators from body fat, play an important role in OA pathogenesis. Additionally, previous studies from the Guilak lab highlight the synergistic importance of the mechanosensitive ion channels Piezo1 and Piezo2 in cartilage health and maintenance: obesity and an OA-relevant inflammatory mediator, interleukin 1 alpha (IL-1α), modulates and sensitizes Piezo channel function. As such, this proposal investigates if cytokine/adipokine signaling is the mechanism by which Piezo channels become hypersensitized to mechanical force, ultimately leading to increased chondrocyte death. The goal of this proposal is to directly investigate the interaction between obesity-associated inflammation and the mechanosensitivity of chondrocytes. This study on the role of altered mechanosensation in the pathogenesis of OA with obesity will lead to the ultimate goal of targeting these pathways to develop novel therapeutic approaches. Specific Aim 1 focuses on determining if obesity-associated inflammatory conditions alter Piezo expression in cartilage and if this increased expression translates to increased chondrocyte sensitivity to mechanical loads. This study hones in on key dysregulated adipokines with obesity: IL-1α, Leptin, tumor necrosis factor alpha (TNF-α), and interleukin 6 (IL-6). Specific Aim 2 uses transgenic mice previously developed in the lab to investigate if the loss of chondrocyte-specific Piezo1 and/or Piezo2 ion channels protects against cartilage damage in an in vivo model of obesity and joint injury. Specifically, mice will be fed a high-fat diet (60% fat) and subjected to a destabilization of the medial meniscus (DMM) surgery, known to evoke post-traumatic OA. Together, both aims strategically develop atomic force microscopy (AFM) and calcium (Ca2+) imaging techniques with in vivo assessments of cartilage integrity to complement the use of genetically-modified mice in a model of HFD superimposed with DMM injury. The results from this study will help identify the mechanisms by which obesity affects cartilage health, ultimately leading to the development of OA disease modifying drugs, that may be more broadly applied to other tissues affected by altered mechanosensation of Piezo ion channels.