Mechanisms of Synovial Joint Formation

描述（由申请人提供）：滑膜关节对于骨骼功能至关重要，但令人惊讶的是，我们对它们在胎儿生命中实际上是如何形成的仍然一无所知。在肢体中，关节发育始于未来关节部位间质间质的出现。人们认为带间祖细胞产生包括关节软骨在内的组织并参与关节形态发生，但尚不清楚这些细胞如何执行这些关键任务。信号蛋白 GDF-5 和 Wnt-14 在早期区间强烈表达。研究发现 GDF-5 充当生长和节间决定因子，而 Wnt-14 充当节间/早期关节基因的上游调节因子，包括 GDF-5 本身、脊索蛋白和 CD-44。在前期工作中，我们首次表明： Wnt-14 和 GDF-5 在层间形成过程中以不同的模式表达；关节周围间充质细胞迁移至新生的间带；在关节形态发生过程中，GDF-5 的表达仅限于凸侧； Wnt-14 信号传导涉及 b-连环蛋白。我们的中心假设是：(i) 区域间由来自关节周围部位的祖细胞组成； (ii) GDF-5 和 Wnt-14 在区间和关节形成以及形态发生过程中具有不同但相互关联的作用。我们的目标是建立区间细胞的起源和命运图，确定 GDF-5 和 Wnt-14 的作用和作用机制，并创建条件性 Wnt-14 消融小鼠并评估后果。我们将使用细胞追踪程序，包括将 ROSA 报告小鼠与可用的 GDF-5-Cre 小鼠交配；嵌合显微外科手术方法； Wnt-14 和 GDF-5 在小鸡和小鼠自足（爪子）上获得和丧失功能的方法，包括从现有的 GDF-5 缺失短足小鼠和 b-连环蛋白依赖性 axin-2 启动子报告小鼠中分离出来的那些。该项目将产生有关联合形成机制的基本信息。这些结果对于构思新的、定向的和具体的疗法来修复和恢复老年人和其他受影响的患者常见的关节功能障碍而言具有无价的价值。

DESCRIPTION (provided by applicant): Synovial joints are critical for skeletal function, but we remain surprisingly ignorant about how they actually form during fetal life. In the limb, joint development starts with appearance of a mesenchymal interzone at future joint sites. Interzone progenitor cells are thought to give rise to tissues including articular cartilage and participate in joint morphogenesis, but it is not clear how the cells perform these critical tasks. The signaling proteins GDF-5 and Wnt-14 are strongly expressed by early interzone. GDF-5 was found to act as a growth and interzone determination factor, while Wnt-14 acted as an upstream regulator of interzone/early joint genes, including GDF-5 itself, Chordin and CD-44. In preliminary work we show for the first time that: Wnt-14 and GDF-5 are expressed in distinct patterns during interzone formation; peri-joint mesenchymal cells migrate into nascent interzone; GDF-5 expression becomes restricted to convex side during joint morphogenesis; and Wnt-14 signaling involves b-catenin. Our central hypotheses are: (i) interzone is made of progenitor cells derived from peri-joint sites; and (ii) GDF-5 and Wnt-14 have distinct, but interrelated roles during interzone and joint formation and morphogenesis. Our aims are to establish origin and fate maps of interzone cells, determine GDF-5 and Wnt-14 roles and mechanisms of action, and create conditionally Wnt-14-ablated mice and assess consequences. We will use cell tracing-tracking procedures, including ROSA reporter mice mated with available GDF-5-Cre mice; chimeric-microsurgical approaches; and Wnt-14 and GDF-5 gain- and loss-of-function approaches on chick and mouse autopods (paws), including those isolated from available GDF-5-null brachypodism mice and b-catenin-dependent axin-2 promoter reporter mice. The project will generate fundamental information on mechanisms of joint formation. The results will be invaluable in conceiving novel, directed and specific therapies to repair and restore malfunctioning joints common to aging individuals and otherwise affected patients.