Mechanisms of Synovial Joint Formation

描述(申请人提供)：滑膜关节对骨骼功能至关重要，但令人惊讶的是，我们仍然不知道它们在胎儿时期实际是如何形成的。在肢体中，关节发育始于未来关节部位间充质带的出现。带间祖细胞被认为可以产生包括关节软骨在内的组织，并参与关节形态的形成，但目前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在早期区域强烈表达。GDF-5被发现作为生长和区间决定因子，而WNT-14作为区间/早期联合基因的上游调节因子，包括GDF-5本身、Chordin和CD-44。在前期工作中，我们首次发现：WNT-14和GDF-5在关节间隙形成过程中以不同的方式表达；关节周围间充质细胞迁移到新生的间隙；GDF-5在关节形态发生过程中仅限于凸侧表达；WNT-14信号涉及b-连环蛋白。我们的中心假设是：(I)区间是由来自关节周围部位的祖细胞组成的；(Ii)GDF-5和Wnt-14在区间和关节的形成和形态发生过程中具有不同但相互关联的作用。我们的目标是建立带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，并建立有条件的WNT-14消融小鼠并评估后果。我们将使用细胞追踪程序，包括ROSA报告小鼠与可用的GDF-5-CRE小鼠交配；嵌合显微外科方法；以及WNT-14和GDF-5在鸡和小鼠自体(PAW)上获得和丧失功能的方法，包括从可用的GDF-5缺失的短足症小鼠和b-连环素依赖Axin-2启动子报告小鼠分离的方法。该项目将产生有关联合形成机制的基本信息。这一结果将对构思新的、直接的和特定的治疗方法来修复和恢复老年人和其他受影响的患者常见的功能障碍的关节具有无价的价值。

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.