Mechanisms of osteocyte induction and regulation of pathogen-induced osteolysis

最近，人们发现骨细胞是多功能的细胞，可以作为发展的目标， 新疗法然而，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目标。令我们惊讶的是， Pam3CSK 4诱导的"骨细胞MYD 88恢复小鼠"颅骨骨质溶解与野生型相似 尽管MYD 88在所有其他细胞（包括免疫细胞）中被全局删除，但在动物中，MYD 88在所有其他细胞（包括免疫细胞）中被全局删除。皮下 炎性浸润表达TNF-α、IL-1 β和IL-6，并富含中性粒细胞和巨噬细胞。 这些发现表明骨细胞衍生的炎症因子诱导骨吸收， 炎性细胞迁移。在体外，多重分析显示，Pam3CSK 4刺激分泌 来自原代骨细胞的CCL2、CCL3、CXCL1和IL-6。此外，"骨细胞MYD 88-恢复小鼠" 表现出细菌引起的牙周炎，伴有牙槽骨丢失。总之，我们的数据提供了新的 这一观察结果表明，单独激活MYD 88通路的骨细胞足以触发和发展 严重的炎性骨质溶解更重要的是，这些数据提供了针对 通过骨细胞和骨表面的免疫细胞和破骨细胞祖细胞的活化， 分子信号机制然而，细菌诱导的骨质溶解是如何 当正常（MYD88充足）免疫和破骨细胞 存在祖细胞。此外，MYD 88是否是一个令人信服的有益药物靶点仍有待验证。 用于体内骨感染引起的骨质溶解。我们假设A）MYD 88介导的骨细胞炎症 与正常免疫和破骨细胞祖细胞合作调节骨质溶解，和B）阻断 骨细胞MYD88通路通过MYD88抑制剂抑制骨细胞衍生的炎症介质， 从而防止和治疗由于骨感染引起的骨质溶解。为了验证这些假设， 具体目的如下：目的1）确定骨细胞MYD 88缺失的影响 对颅骨骨质溶解的作用。目的2）确定骨细胞MYD 88功能缺失对骨形成的影响。 牙龈卟啉单胞菌引起的牙周炎。目的3）确定药物是否抑制骨细胞以及如何抑制骨细胞 MYD 88可有效治疗由于细菌炎症引起的骨质溶解。我们认为骨细胞 在细菌诱导的骨质溶解条件下发挥作用，了解这一重要作用可能会导致新的 治疗学我们将揭示骨细胞作为炎症细胞的一个新的和重要的作用， 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 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.