Fetuin-A in post-traumatic osteoarthritis: at the crossroad between joint and muscle degeneration

项目摘要 由创伤引起的关节损伤可发展为创伤后骨关节炎（PTOA），目前尚无治愈方法。 肌肉位于关节附近，对吸收关节负荷至关重要。股四头肌无力是 在OA患者中最早发现，可先于临床OA，并与疼痛增加相关。但如何 肌无力与PTOA的关系尚不清楚。在确定可能影响两种组织的OA治疗方法的努力中， 对于退行性变和疼痛，识别作用于关节和肌肉的新因素至关重要。在这方面， 胎球蛋白-A代表理想的候选物。胎球蛋白-A是在肝脏中合成的循环糖蛋白， 已被证明在损伤中具有抗炎作用，尽管其在关节炎中的作用仍不清楚。降低 胎球蛋白-A血清水平显示与更严重的放射学OA和疼痛相关。胎球蛋白A是一种 BMP信号传导拮抗剂，调节骨代谢。因此，BMP拮抗作用的损失减少， 在OA过程中，胎球蛋白-A可能会使BMP的局部活性失衡，导致更多的软骨细胞 以及骨骼损伤临床研究表明，从晚期OA中收集的成骨细胞 有显着较低的量的胎球蛋白-A比非sclerosis;我们的初步数据，在小鼠PTOA模型 （内侧半月板不稳定，DMM）显示OA软骨显示胎球蛋白-A开始急剧减少。 在早期阶段，在DMM小鼠中给予OA和全身性胎球蛋白A减少了这种损伤。重要的是 已经表明胎球蛋白-A对BMP的拮抗作用在肌肉发育和体内平衡中也是关键的。我们 DMM中的数据显示，在轻度和中度的四头肌中胎球蛋白-A蛋白水平均降低， 此外，人类OA肌肉的初步数据显示， OA股四头肌与对照组相比。总之，这些研究表明，胎球蛋白A的减少可能会发挥作用， 在OA及其相关疼痛中起关键作用，影响关节和肌肉组织。我们假设， 损伤后胎球蛋白A导致软骨和骨损伤，沿着肌肉损伤，最终导致 PTOA和疼痛。通过使用体内DMM小鼠创伤后OA模型，我们建议确定是否 胎球蛋白-A通过BMP信号传导起作用，是保护软骨、骨和肌肉的治疗因子 在OA期间保持完整性并减轻疼痛。具体地说，我们将确定胎球蛋白-A的保护作用， DMM通过全身性过表达胎球蛋白-A诱导OA，以及通过局部施用胎球蛋白-A， 关节使用微粒持续缓慢释放;我们将遵循软骨/骨损伤，炎症 和疼痛感知在不同阶段的PTOA（Aim 1）。我们通过测量获得的新的体内初步数据 腓肠肌比目鱼肌显示，DMM期间的肌肉强度从中度OA开始降低 阶段;因此，在一组单独的实验中，我们将使用肌肉功能的体内和体外分析， 检查全身或关节内注射胎球蛋白A如何影响OA进展期间的肌肉力量（Aim 2）。 我们还将确定胎球蛋白-A下游途径在关节和肌肉组织中的变化。

PROJECT ABSTRACT Joint damage caused by trauma can proceed to post-traumatic osteoarthritis (PTOA), with no cure available. Muscles are situated in joint proximity and are critical to absorb joint loads. Quadriceps weakness is one of the earliest findings in OA patients, can precede clinical OA, and is associated with increased pain. However, how muscle weakness relates to PTOA is unclear. In the efforts to identify OA treatments that can impact both tissue degeneration and pain, it is critical to identify novel factors acting on both joints and muscles. In this respect, fetuin-A represents an ideal candidate. Fetuin-A is a circulating glycoprotein synthesized in the liver and has been shown to have an anti-inflammatory role in injury, although its role in arthritis is still not clear. Decreased fetuin-A serum levels were shown to be correlated with more severe radiographic OA and pain. Fetuin-A is an antagonist of BMP signaling and regulates bone metabolism. Therefore, loss of BMP antagonism by reduced fetuin-A during OA, could allow for an unbalance in the local activity of BMPs, resulting in more chondrocyte hyperthrophy, and bone damage. A clinical study showed that sclerotic osteoblasts collected from late stage OA have significantly lower amounts of fetuin-A than non-sclerotic; our preliminary data in a mouse PTOA model (destabilization of medial meniscus, DMM) show that OA cartilage shows a drastic decrease of fetuin-A starting at the early stage OA and systemic fetuin-A administration in DMM mice reduced such damage. Importantly, it has been shown that BMP antagonism by Fetuin-A is also critical in muscle development and homeostasis. Our data in the DMM show that fetuin-A protein levels in quadriceps were decreased at both the mild and moderate OA stages; in addition, preliminary data in human OA muscles showed that protein fetuin-A levels were lower in OA quadriceps compared to controls. Taken together, these studies suggest that reduction in fetuin-A might play a key role in OA and its associated pain, affecting both joint and muscle tissues. We hypothesize that loss of fetuin-A after injury leads to cartilage and bone damage, along with muscle impairment, ultimately leading to PTOA and pain. By using the in-vivo DMM mouse post-traumatic OA model, we propose to determine whether fetuin-A, acting through BMP signaling, represents a therapeutic factor to preserve cartilage, bone and muscle integrity during OA and alleviate pain. Specifically, we will determine the fetuin-A protective effect during the DMM-induced OA by systemically overexpressing fetuin-A, as well as by local administration of fetuin-A intra- articularly using micro-particles for sustained slow release; we will follow cartilage/bone damage, inflammation and pain perception at different stages of PTOA (Aim1). Our new in-vivo preliminary data obtained by measuring the gastrocnemius soleus showed that muscle strength during DMM decreases starting at the moderate OA stage; therefore, in a separate set of experiments, we will use in-vivo and ex-vivo analyses of muscle function, to examine how systemic or intra-articular injected fetuin-A affect muscle strength during OA progression (Aim2). We will also determine fetuin-A downstream pathway changes in joint and muscle tissues.