Mechanisms of osteocyte induction and regulation of pathogen-induced osteolysis

近年来，人们发现骨细胞是一种多功能细胞，可以作为开发的靶细胞。 新疗法。然而，目前尚不清楚骨细胞是否可以作为骨髓炎的治疗靶点。 牙周炎，如果是这样，哪种分子机制可以作为靶点。令我们惊讶的是， Pam3CSK4诱导的“骨细胞MYD88修复小鼠”颅骨溶解与野生型相似 动物，尽管MYD88在包括免疫细胞在内的所有其他细胞中被全局删除。皮下 炎性渗出物表达肿瘤坏死因子-ɑ、IL-1β和IL-6，中性粒细胞和巨噬细胞丰富。 这些发现表明，骨细胞源性炎症因子正在诱导骨吸收和 炎性细胞迁移。在体外，多重分析表明Pam3CSK4刺激分泌 原代骨细胞来源的CCL2、CCL3、CXCL1和IL-6。此外，“骨细胞MYD88-修复小鼠” 表现为细菌性牙周炎伴牙槽骨丢失。总而言之，我们的数据提供了这部小说 观察表明，仅骨细胞MYD88通路的激活就足以触发和发展 大量炎性骨溶解。更重要的是，这些数据提供了瞄准 通过骨细胞及其受体激活骨表面免疫细胞和破骨细胞前体 分子信号机制。然而，目前尚不清楚细菌诱导的骨溶解作用有多大。 当正常(MYD88充足)免疫和破骨细胞时，受骨细胞MYD88途径控制 祖细胞存在。此外，MYD88是否是一个令人信服的有益药物靶点仍未得到测试 用于体内骨感染引起的骨溶解。我们假设A)MYD88介导的骨细胞炎症 与正常免疫和破骨细胞前体细胞协同调节骨溶解，B)阻断 MYD88抑制剂介导的骨细胞MYD88通路抑制骨细胞源性炎症介质 从而预防和治疗由于骨感染引起的骨溶解。为了检验这些假说， 提出了以下具体目标：目的1)确定骨细胞MYD88缺失的影响 对颅骨骨溶解的作用。目的2)确定骨细胞MYD88功能缺失对 牙龈假单胞菌引起牙周炎。目的3)确定药物对骨细胞的抑制是否以及如何 MyD88可有效治疗细菌性炎症引起的骨溶解。我们认为骨细胞 在细菌诱导的骨溶解条件下发挥作用，了解其重要作用可能导致新的 治疗学。我们将揭示骨细胞作为炎症细胞的新的和基本的作用，它调节 免疫细胞活化和破骨细胞形成。骨细胞的新方面将提供新的治疗方法 骨髓炎和牙周炎的治疗策略。

Recently, it has been discovered that osteocytes are multifunctional cells that can serve as targets to develop new therapeutics. However, it is not known if osteocytes can be a therapeutic target for osteomyelitis and periodontitis, and if so, which molecular mechanism can be targeted. To our surprise, the magnitude of Pam3CSK4-induced calvarial osteolysis in “osteocyte MYD88-restoration mice” was similar to wild-type animals even though MYD88 was globally deleted in all other cells including immune cells. Subcutaneous inflammatory infiltrates expressed TNF-ɑ, IL-1β, and IL-6 and were rich in neutrophils and macrophages. These findings suggest that osteocyte-derived inflammatory factors are inducing bone resorption and inflammatory cell migration. In vitro, the multiplex analysis showed that Pam3CSK4 stimulates the secretion of CCL2, CCL3, CXCL1, and IL-6 from primary osteocytes. In addition, “osteocyte MYD88-restoration mice” exhibited bacterially-induced periodontitis with alveolar bone loss. Together, our data provide the novel observation suggesting that MYD88 pathway activation of osteocytes alone is sufficient to trigger and develop considerable inflammatory osteolysis. More importantly, these data offer the opportunity to target the activation of immune cells and osteoclast progenitors on the bone surface through the osteocyte and its molecular signaling mechanisms. However, it remains unknown how bacterially-induced osteolysis is controlled by the osteocyte MYD88 pathway when normal (MYD88-sufficient) immune and osteoclast progenitor cells are present. Furthermore, it remains untested if MYD88 is a convincing beneficial drug target for osteolysis due to bone infections in vivo. We hypothesize that A) MYD88-mediated osteocyte inflammation regulates osteolysis in cooperation with normal immune and osteoclast progenitor cells and B) blocking the osteocyte MYD88 pathway by MYD88 inhibitors suppresses osteocyte-derived inflammatory mediators, resulting in the protection against and treatment of osteolysis due to bone infections. To test the hypotheses, the following specific aims are proposed: Aim 1) Determine the impact of the deletion of osteocyte MYD88 function on calvarial osteolysis. Aim 2) Determine the impact of the deletion of osteocyte MYD88 function on P.gingivalis-induced periodontitis. Aim 3) Determine whether and how pharmacological inhibition of osteocyte MYD88 can be effective for treating osteolysis due to bacterial inflammation. We propose that the osteocytes play a role in bacterially-induced osteolysis conditions and understanding the important role could lead to new therapeutics. We will uncover a novel and essential role of osteocytes as inflammatory cells that regulate immune cell activation and osteoclast formation. The new aspect of osteocytes will provide new therapeutic strategies for osteomyelitis and periodontitis.