Innate inflammation in osteoarthritis

骨关节炎(OA)在美国是导致残疾的主要原因，尤其是在退伍军人中，他们是 不成比例地受到衰老和关节创伤的影响。骨性关节炎最终导致关节失效，包括 软骨细胞分化和功能受损，其机制还不完全 明白了。由于目前尚无治疗骨性关节炎的药物，因此存在尚未得到满足的主要需求。 高级翻译。我们的长期目标是验证限制骨性关节炎软骨衰竭的新靶点，包括 促进分子固有炎症过程(“炎症老化”)的过程。一个主要的障碍是 领域是多种稳态机制在骨性关节炎软骨细胞中失调，我们需要理清 它们是最早的，也是软骨细胞分化改变和活性丧失的中心。我们有 衰老和膝骨性关节炎患者的线粒体质量、功能和生物发生能力降低 软骨细胞，部分与TFAM和其他线粒体转录因子缺乏有关。我们的核心 假说认为关节软骨细胞线粒体功能障碍是一种早期的、关键的、有靶向性和可逆性的 衰老和生物力学损伤引起的骨性关节炎的改变，并被改变的线粒体逆行放大 发信号。这包括抗炎线粒体肽Human in的减少，导致对 我们假设的软骨细胞在体外至少是部分可逆的，使用人蛋白类似物HNGF6A。 有效控制与损伤和衰老相关的组织退化不仅需要生物发生，而且还需要 维护健康的线粒体。在我们假设的新的、可测试的OA发病机制模型中， 软骨细胞线粒体损伤在很大程度上是通过前馈和反馈环路持续存在的，涉及 在正常情况下确保线粒体质量控制的细胞监测机制上的妥协。我们特别指出 假设软骨细胞有丝分裂失败，不仅是由于缺乏有丝分裂“关键”BNIP3a， 而且还减少了受损的多泛素化线粒体外膜的蛋白酶体降解 蛋白质，如PINK1和Parkin，通过泛素蛋白酶体系统(UPS)，这是必不可少的 有丝分裂。 我们的初步研究开辟了实质性的新天地，揭示了UPS功能在 骨关节炎软骨细胞，包括有缺陷的20S蛋白酶体核心颗粒的蛋白分解活性，以及堆积的 软骨细胞K48多泛素化蛋白。我们进一步鉴定了人膝关节骨性关节炎软骨细胞 蛋白酶体组装受损，这种状态导致软骨细胞丢失的全局性后果 分化，通过软骨细胞主转录因子Sox9的表达减少，并降低 基质合成代谢基因表达。为了测试我们的早期、关键的OA发病机制的综合模型， 创新的应用是我们汇集了一个特别多样化的调查团队，包括 线粒体生物学、自噬和有丝分裂吞噬以及UPS和图谱方面的合作专家 细胞泛素组签名。我们将使用我们最近验证的软骨细胞生物力学模型 损伤，并通过对两个正常年龄的年龄匹配分析，对人类软骨细胞老化进行独特的研究 和OA膝关节软骨细胞。此外，我们解决了专门测试线粒体的作用的问题 在衰老损伤的骨关节炎中，通过产生软骨细胞特异性的TFAM基因敲除小鼠模型，这将是 与正常小鼠相比，分析了在体内衰老的骨关节炎。这些研究的完成将推动我们的 通过识别新的骨性关节炎软骨细胞生物标记物，以及通过 将人和其他新颖、合理的靶点定位于潜在的医疗疾病修饰开发 办公自动化疗法。

Osteoarthritis (OA) is a major cause of disability in the USA, particularly so in veterans, who are disproportionately affected by aging and joint trauma. OA culminates in failure of the joint, which includes compromised cartilage chondrocyte differentiation and function, by mechanisms that are not completely understood. Because there is no disease-modifying medical therapy for OA, there is major unmet need to advance translation. Our long-term objective is to validate novel targets to limit OA cartilage failure, including processes that promote molecular innate inflammatory processes ("inflamm-aging"). A major obstacle in the field is that multiple homeostasis mechanisms are dysfunctional in OA chondrocytes, and we need to sort out which are the earliest, and central to the chondrocyte differentiation changes and viability loss. We have identified decreased mitochondrial mass, function, and biogenesis capacity in aging and OA knee chondrocytes, linked partly to deficiency of TFAM and other mitochondrial transcription factors. Our core hypothesis is that articular chondrocyte mitochondrial dysfunction is an early, pivotal, targetable, and reversible change in OA due to aging and biomechanical injury, and amplified by altered mitochondrial retrograde signaling. This includes decrease in the anti-inflammatory mitochondrial peptide humanin, causing effects on chondrocytes that we posit to be at least partly reversible in vitro using the humanin analog HNGF6A. Effective control of injury- and aging-associated tissue degeneration requires not only biogenesis but also maintenance of healthy mitochondria. In the novel, testable OA pathogenesis model that we hypothesize, chondrocyte mitochondrial damage is perpetuated, in large part, by feed-forward and feedback loops involving compromise in cell surveillance mechanisms that normally assure mitochondrial quality control. We specifically hypothesize the failure of chondrocyte mitophagy, via not only deficiency of the mitophagy “linchpin” BNIP3a, but also decreased proteasomal degradation of damaged polyubiquitinated outer mitochondrial membrane proteins, such as PINK1 and Parkin, by the ubiquitin proteasome system (UPS), which is essential for mitophagy. Our preliminary studies break substantial new ground by revealing markedly impaired UPS function in OA chondrocytes, including defective 20S proteasome core particle proteolytic activity, and accumulation of chondrocyte K48 polyubiquitinated proteins. We further identified that human knee OA chondrocytes have impaired assembly of the proteasome, a state that induces global outcomes of loss of chondrocytic differentiation, via diminished expression of the chondrocyte master transcription factor Sox9, and decreased matrix anabolic gene expression. For testing our integrative model of early, pivotal OA pathogenesis, innovation is applied by our bringing together of a particularly diverse investigative team, including collaborating experts in mitochondrial biology, autophagy and mitophagy, and in the UPS and profiling of cellular ubiquitylome signatures. We will employ our recently validated model of chondrocyte biomechanical injury, and carry out unique studies of human chondrocyte aging, via age-matched analyses of both normal and OA knee chondrocytes. Moreover, we address the problem of specifically testing the role of mitochondrial damage in OA of aging, by generating a chondrocyte-specific mouse model of TFAM knockout, which will be compared to normal mice in analyses for OA with aging in vivo. Completion of these studies will advance our long term goal of spurring translation in OA, by identifying novel OA chondrocyte biomarkers, and by pinpointing humanin and other novel, rational targets for potential development of medical disease-modifying OA therapies.