Osteoblastic lineage cells regulate osteoclastogenesis via Cx43 and gap junctions

描述(由申请人提供)： 项目摘要/摘要正常的骨重建需要骨吸收、破骨细胞和成骨细胞之间的同步活动。这种同步化包括成骨细胞和破骨细胞的招募，以及对破骨细胞和成骨细胞增殖和分化的刺激。骨吸收和骨形成之间的失衡可能会导致骨病，如骨质疏松症和骨化症。缝隙连接(GJ)是跨膜的通道，允许离子和信号分子在相邻的两个细胞之间通过，其大小小于1KD。每个缝隙连接由两个半通道或连接外显子组成，每个连接外显子由6个连接蛋白组成。骨细胞中连接蛋白的主要形式是Cx43。以往的体外研究表明，Cx43、半通道和GJ对成骨细胞、骨细胞和破骨细胞的分化和功能具有调节作用。然而，Cx43和GJIC在骨骼中的体内功能还知之甚少。为了解决这一缺陷，我们特别删除了小鼠成骨细胞和骨细胞中的Cx43。基因敲除的小鼠表现出骨质疏松的表型，破骨细胞数量增加。因此，在这一应用中，我们假设成骨细胞系细胞，包括成骨细胞和骨细胞，与破骨细胞沟通，并通过Cx43和GJIC抑制破骨细胞的生成。我们的假设预测，降低Cx43水平和成骨细胞系细胞和破骨细胞系细胞之间的异型GJIC会导致破骨细胞活性增加。我们将通过三个目标来研究成骨细胞系细胞是否通过Cx43和GJIC调节破骨细胞的生成：目的1，证实Cx43介导的破骨细胞和破骨细胞之间的GJIC；目的2，定量不同Cx43水平的成骨细胞和骨细胞在体内和体外诱导的破骨细胞数量和活性；以及目的3，探讨Cx43和GJIC介导的成骨细胞和成骨细胞调控破骨细胞生成的机制。通过完成这些目标，我们不仅将确定Cx43和GJIC在骨骼中的新功能，还将确定导致骨量减少的新机制。 公共卫生相关性： 项目简介我们将研究破骨细胞是否通过Cx43介导的缝隙连接细胞间通讯(GJIC)与成骨细胞系细胞进行通讯。此外，我们还将研究Cx43和GJIC在成骨细胞系细胞调控破骨细胞形成中的作用和机制。拟议目标的完成将极大地有助于开发治疗骨代谢障碍的新靶点，包括骨量减少症和骨化症。

DESCRIPTION (provided by applicant): Project Summary/Abstract The normal remodeling of bone requires synchronized activity between bone resorbing osteoclastic and bone forming osteoblastic cells. This synchronization includes the recruitment of osteoblasts and osteoclasts, and the stimulation of osteoclast and osteoblast proliferation and differentiation. Imbalances between bone resorption and formation may lead to bone disorders, such as osteoporosis and osteopetrosis. Gap junctions (GJ) are membrane-spanning channels that allow passage of ions and signaling molecules, less than 1KD in size, between two adjacent cells. Each gap junction is composed of two hemichannels or connexons and each connexon is comprised of 6 connexins. The predominant form of connexin in bone cells is Cx43. Previous In vitro studies demonstrated that Cx43, hemichannel and GJ regulate osteoblast, osteocyte and osteoclast differentiation and function. However, little is known about the in vivo function of Cx43 and GJIC in bone. To address this deficit, we specifically deleted Cx43 in mouse osteoblasts and osteocytes. The knockout mice displayed osteopenic phenotypes with increased osteoclast number. Therefore, in this application, we hypothesize that osteoblastic lineage cells, including osteoblasts and osteocytes, communicate with osteoclastic cells and inhibit osteoclastogenesis via Cx43 and GJIC. Our hypothesis predicts that reducing Cx43 levels and heterotypic GJIC between osteoblastic lineage cells and osteoclastic lineage cells leads to increased osteoclastic activity. We will examine whether osteoblastic lineage cells regulate osteoclastogenesis via Cx43 and GJIC by completing three aims over a 3 year period: Aim 1, demonstrate Cx43-mediated GJIC between osteoblastic or osteocytic and osteoclastic cells; Aim 2, quantify osteoclast cell number and activity, both in vivo and in vitro, induced by osteoblasts and osteocytes with different Cx43 levels; and aim 3, investigate the mechanism of Cx43 and GJIC mediated osteoblastic and osteocytic cell regulated osteoclastogenesis. By completing these aims we will not only identify new functions of Cx43 and GJIC in bone, but will also identify novel mechanisms contributing to osteopenia. PUBLIC HEALTH RELEVANCE: Project Narrative We will examine whether osteoclasts communicate with osteocblastic lineage cells via Cx43 mediated gap junctional intercellular communication (GJIC). Furthermore, We will also investigate the role and mechanism of Cx43 and GJIC in osteoclastogenesis regulated by osteoblastic lineage cells. The completion of the proposed aims will greatly help to develop novel therapeutic targets for disorders of bone metabolism including osteopenias and osteopetrosis.