Connexin channels in transducing mechanical signals in bone

项目摘要 骨组织所承受的机械载荷在骨形成和骨重建中起着重要作用。 骨细胞是最丰富的骨细胞类型，也是骨骼的主要机械感觉细胞。他们 通过协调成骨细胞的形成，协调整个骨基质的骨重建 和骨吸收。骨细胞通过间隙与相邻的骨细胞和其他骨细胞连接 连接通道并通过半通道进入细胞外环境。这两种渠道都是由 连接蛋白（Cx）43. Cx43参与骨组织对机械刺激的反应， 在基因敲除模型中显示;然而，间隙连接通道和半通道在基因敲除模型中的不同功能， 骨细胞，以及这些通道在机械过程中的生理作用的机制 装载量仍然很大程度上未知。为了剖析这两种通道的生理作用，我们有 最近开发了两种主要表达Cx43显性失活突变体的转基因小鼠模型 在骨细胞中。我们也正在建立一个Cx43突变基因敲入小鼠模型，以补充我们的研究。 转基因模型这些突变损害骨细胞间隙连接通道和/或半通道。此外，本发明还提供了一种方法， 我们已经产生了特异性抑制Cx43半通道但不抑制间隙连接通道的抗体。 此外，我们已经开发了新的方法，使我们能够评估骨细胞半通道活性原位。 初步数据表明，Cx43半通道的损伤减弱了机械性代谢的合成作用。 在骨头上加载。我们和其他人还表明，骨细胞Cx43半通道是开放的， 机械应力，释放小骨合成代谢因子，包括体外的三尖杉酯碱。目标是 确定Cx43半通道在介导机械合成代谢作用中的特定机制作用。 骨骼组织上的负荷。提出了三个具体的目的：1）测试假设，骨细胞 Cx43半通道在介导骨骼组织机械负荷的合成代谢功能中起着至关重要的作用。 2)为了验证骨细胞Cx43半通道介导机械负荷的合成代谢功能的假设， 通过PGE 2释放，以及PGE 2和Wnt信号传导的激活。3)为了验证激活和 Cx43半通道的失活受整合素活化/细胞骨架和MAPK的特异性调节 信号，分别。拟议的研究预计将产生重大的积极影响， 骨组织中的机械传导机制及其调控，构成潜能，意义 对开发用于治疗骨质疏松症和骨的新治疗剂的贡献 损失

Project Summary Mechanical loading experienced by skeletal tissues plays an important role in bone formation and remodeling. Osteocytes are the most abundant bone cell type and the major mechanosensory cells of the bone. They orchestrate bone remodeling from their location throughout bone matrix by coordinating osteoblastic formation and osteoclastic resorption. Osteocytes are connected to neighboring osteocytes and other bone cells via gap junction channels and to extracellular environments via hemichannels. Both types of channels are formed by connexin (Cx) 43. The involvement of Cx43 in response to mechanical stimulation of bone tissue has been shown in gene knockout models; however, the distinct functions of gap junction channels and hemichannels in osteocytes, as well as the mechanism underlying the physiological roles of these channels during mechanical loading remain largely unknown. To dissect the physiological roles of these two types of channels, we have recently developed two transgenic mouse models expressing Cx43 dominant negative mutants predominantly in osteocytes. We are also generating a Cx43 mutant gene knockin mouse model to complement our transgenic models. These mutations impair osteocytic gap junction channels and/or hemichannels. In addition, we have generated antibodies that specifically inhibit Cx43 hemichannels, but not gap junction channels. Moreover, we have developed novel approaches that allow us to assess osteocytic hemichannel activity in situ. Preliminary data show that impairment of Cx43 hemichannels attenuates the anabolic effect of mechanical loading on the bone. We and others have also shown that osteocytic Cx43 hemichannels are opened by mechanical stress, releasing small bone anabolic factors including prostaglandins in vitro. The objective is to determine the specific mechanistic role of Cx43 hemichannels in mediating the anabolic effect of mechanical loading on the skeletal tissues. Three specific aims are proposed: 1) To test the hypothesis that osteocytic Cx43 hemichannels play a crucial role in mediating anabolic function of mechanical loading on skeletal tissue. 2) To test the hypothesis that osteocytic Cx43 hemichannels mediate anabolic function of mechanical loading via PGE2 release, and activation of PGE2 and Wnt signaling. 3) To test the hypothesis that activation and inactivation of Cx43 hemichannels are specifically regulated by integrin activation/cytoskeleton and MAPK signaling, respectively. The proposed studies are expected to have a major positive impact by defining the mechanical transduction mechanism and its regulation in bone tissue, constituting potential, significant contributions toward the development of new therapeutic agents for the treatment of osteoporosis and bone loss.