Targeting GPR68 as a novel modulator of osteoarthritis

临床前提：骨关节炎（OA）是最常见的关节疾病，是一种使人衰弱的关节疾病 涉及进行性软骨退化，没有可用的疾病改善疗法。因此，努力 阐明可用于预防和/或治疗OA的新的分子靶点和机制至关重要 重要性最近，一种孤儿GPCR蛋白-GPR 68已被鉴定和表征， 肌肉骨骼组织，包括骨和椎间盘，但其在软骨和OA中的作用尚不清楚。 我们的初步分析表明，GPR 68在人OA软骨中稳定表达， 患者和实验模型的OA小鼠，表明其在OA发病机制中的作用。使用IDG/Pharos 数据库中，我们鉴定了与GPR 68相关的主要GO术语（基因本体论）“炎症过程”。在 本项目中，我们建议建立GPR 68在骨关节炎炎症信号传导中的功能作用， 探讨其在OA发病机制中的意义。 科学前提：我们提供了以下令人信服的初步证据：1。GPR 68是稳定的。 在人和小鼠软骨中表达，并且其在OA软骨中的表达显著高于 健康的软骨; 2. GPR 68 mRNA和蛋白水平在高级别OA软骨中较高， 低度OA软骨; 3.原代人软骨细胞的机械刺激导致 GPR 68的表达; 4. Gpr 68在手术诱导的OA小鼠软骨中的表达显着升高 (DMM手术）与假手术对照相比; 5. IL-1 β刺激OA软骨细胞可显著提高OA细胞的增殖能力。 GPR 68表达增加; 6.骨关节炎软骨细胞中GPR 68的敲低减轻了IL-1β诱导的骨关节炎软骨细胞凋亡 炎症基因的表达。 假设：GPR 68介导炎症和分解代谢作用，导致OA进展， GPR 68的抑制减弱了OA关节中的炎症和基质变性。 具体目的：为了验证这一假设，我们将建立GPR 68在炎症反应中的功能作用。 和人OA软骨细胞（Aim 1）中的分解代谢途径。然后，我们将定义Gpr 68在软骨中的作用。 体内手术诱导骨关节炎的降解（目的2）。 影响：确定GPR 68在调节软骨细胞炎症和炎症反应中的病理生理作用。 分解代谢活性将导致治疗OA的新治疗策略的潜在发展，从而奠定 为今后临床研究建立新型有效的OA修饰药物奠定了基础。

Clinical premise: Osteoarthritis (OA), the most common form of joint disorder, is a debilitating joint disease involving progressive cartilage degeneration, with no disease modifying therapy available. Thus, efforts to elucidate new molecular target and mechanism that can be utilized to prevent and/or treat the OA are of utmost importance. Recently, an orphan GPCR protein-the GPR68 has been identified and characterized in musculoskeletal tissues including bone and intervertebral disc, however its role in cartilage and OA is not known. Our preliminary analyses demonstrate that GPR68 was robustly expressed in cartilage derived from human OA patient and experimental model of OA in mice, indicating its role in OA pathogenesis. Using IDG/Pharos database, we identified `Inflammatory Process' a major GO term (Gene Ontology) associated with GPR68. In this project, we propose to establish the functional role of GPR68 in inflammatory signaling in osteoarthritic chondrocytes and ascertain its significance in OA pathogenesis. Scientific premise: We provide compelling preliminary evidence of the following: 1. GPR68 was robustly expressed in human and mice cartilage and its expression was significantly higher in OA cartilage compared to healthy cartilage; 2. GPR68 mRNA and protein levels was higher in high-grade OA cartilage as compared to low-grade OA cartilage; 3. Mechanical stimulation of primary human chondrocytes resulted in increased expression of GPR68; 4. Gpr68 expression was significantly higher in mice cartilage of surgically induced OA (DMM surgery) as compared to sham control; 5. IL1β stimulation of OA chondrocytes resulted in significantly increased expression of GPR68; 6. Knockdown of GPR68 in OA chondrocytes alleviated IL-1β induced expression of inflammatory genes. Hypothesis: GPR68 mediates inflammatory and catabolic effects leading to OA progression and thus suppression of GPR68 attenuates the inflammation and matrix degeneration in OA joints. Specific objectives: To verify this hypothesis, we will establish the functional role of GPR68 in inflammatory and catabolic pathways in human OA chondrocytes (Aim1). We will then define the role of Gpr68 in cartilage degradation in surgically induced osteoarthritis in vivo (Aim 2). Impact: Identifying the pathophysiological role of GPR68 in the regulation of chondrocyte inflammatory and catabolic activity will lead to the potential development of novel therapeutic strategies to treat OA, thus laying the foundation for future clinical study to establish a novel effective OA modifying drug.