Mechanisms of Synovial Joint Formation

描述（由申请人提供）：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是如何形成的。在肢体中，关节发育始于未来关节部位间质间带的出现。区间祖细胞被认为产生包括关节软骨在内的组织并参与关节形态发生，但尚不清楚细胞是如何完成这些关键任务的。信号蛋白GDF-5和Wnt-14在早期区间强烈表达。研究发现GDF-5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在带间形成过程中以不同的模式表达；关节周围间充质细胞向新生带间迁移；GDF-5在关节形态发生过程中局限于凸侧表达；Wnt-14信号传导涉及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在带间和节理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消融小鼠并评估其后果。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；chimeric-microsurgical方法;以及Wnt-14和GDF-5在鸡和小鼠自足（爪）上的功能获得和功能丧失方法，包括从现有的GDF-5缺失的短足小鼠和b-catenin依赖的轴蛋白-2启动子报告小鼠中分离的小鼠。该项目将提供关于联合形成机制的基本资料。这一结果对于构思新的、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故障关节将是无价的。

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.