Wnt/beta-catenin Signaling in Endochondral Ossification

描述(由申请人提供)：此申请是对NOT-OD-09-058的回应，NIH宣布恢复法资金可用于竞争性修订申请。控制骨骼发育、生长和功能的机制继续吸引着大量的研究工作，但还远远不清楚。在目前的Parent Grant中，我们研究了Wnt/b-catenin信号在生长板功能中的作用，我们当时的新假设是：Wnt/b-catenin信号的激活是软骨细胞肥大和功能以及软骨内成骨的进展和完成所必需的。这些数据充分肯定了我们假设的正确性，揭示了Wnt/b-catenin信号在软骨细胞肥大、基质重塑和细胞凋亡以及软骨内骨化过程中从软骨到骨的无缝过渡中的重要作用。我们的研究和其他人的研究对目前公众认识到Wnt/b-catenin信号在骨骼发育中的重要性做出了重大贡献。随着我们的父代Grant的进展，我们获得了关于Wnt/b-catenin信号和内质网(ER)应激之间可能联系的相关的、有趣的和相当新颖的数据。内质网应激和未折叠蛋白反应(UPR)因其生理和病理作用而在许多研究领域受到极大关注，但在骨骼生物学中却相对较少受到关注。我们使用转基因小鼠的初步数据显示，Wnt/b-catenin信号在体内刺激生长板中的ER应激/UPR和细胞凋亡。利用原代培养的软骨细胞，我们发现在内质网应激条件下，Wnt/b-catenin信号的急性激活会增强关键的UPR反应基因CHOP和Bip的表达，并导致细胞凋亡。我们对本修订申请的中心假设是Wnt/b-catenin信号与ER应激/UPR信号相互作用，调节和局部限制生长板软骨细胞的凋亡。我们的目标是：(1)确定Wnt/b-catenin信号激活如何调节CHOP和Bip的表达；(2)在Wnt/b-catenin信号激活过程中，研究CHOP和Bip在内质网应激诱导的细胞凋亡中的作用。这项修订申请拨款将使我们能够开始填补当前信息中的明显空白，并将为我们的母公司拨款增加新的目标。它将揭示Wnt/b-catenin信号与生长板功能中的内质网应激/UPR之间的调控联系，并在软骨内成骨中建立一个以前未被怀疑的范例。这些调节的串扰和回路可能对生长板的动态平衡和功能是必不可少的，可能是错乱的，并导致一些先天性和获得性骨骼疾病。 公共卫生相关性：项目叙事软骨在骨骼的形成和生长中扮演着重要的角色。由于先天或后天原因导致的软骨功能障碍可导致身体结构缺陷、生长迟缓和退行性软骨疾病。该项目将为调控软骨细胞行为和功能的机制提供新的信息，并将为揭示骨骼疾病的原因铺平道路。

DESCRIPTION (provided by applicant): This application is in response to NOT-OD-09-058, NIH Announces the Availability of Recovery Act Funds for Competitive Revision Applications. The mechanisms controlling skeletal development, growth and function continue to attract much research effort, but are far from clear. In the current Parent Grant, we studied the roles of Wnt/b-catenin signaling in growth plate function, and our novel hypothesis at the time was that 'Activation of Wnt/b-catenin signaling is required for chondrocyte hypertrophy and function and for progression and completion of endochondral ossification.' The data we obtained since and reported in several publications fully affirmed the validity of our hypothesis and did uncover the central importance of Wnt/b-catenin signaling in chondrocyte hypertrophy, matrix remodeling and apoptosis and in the seamless transition from cartilage to bone during endochondral ossification. Our studies and those by others have contributed significantly to the current public recognition of the importance of Wnt/b-catenin signaling in skeletal development. As our Parent Grant was progressing, we obtained related, intriguing and rather novel data on possible connections between Wnt/b-catenin signaling and endoplasmic reticulum (ER) stress. ER stress and unfolded protein response (UPR) are extremely popular in many fields of research because of their physiologic and pathologic roles, but have received relatively little attention in skeletal biology. Our preliminary data using transgenic mice now reveal that Wnt/b-catenin signaling stimulates ER stress/UPR and apoptosis in growth plates in vivo. Using primary chondrocyte cultures, we have found that acute activation of Wnt/b-catenin signaling enhances expression of CHOP and Bip (that are key UPR response genes) and leads to apoptosis under ER stress conditions. Our central hypothesis for this Revision Application is that that Wnt/b-catenin signaling interacts with ER stress/UPR signaling to regulate and topographically restrict apoptosis in growth plate chondrocytes. Our aims are: (1) to determine how CHOP and Bip expression is regulated by activation of Wnt/b-catenin signaling; and (2) to examine CHOP and Bip roles in ER-stress-induced apoptosis during Wnt/b-catenin signaling activation. This Revision Application grant will allow us to begin to fill glaring gaps in current information and will add novel goals to our Parent Grant. It will uncover regulatory interconnections between Wnt/b-catenin signaling and ER stress/UPR in growth plate function and establish a previously unsuspected paradigm in endochondral ossification. These regulatory cross-talk and circuitry are likely to be essential for growth plate homeostasis and function and may be deranged, and cause, a number of congenital and acquired skeletal diseases. PUBLIC HEALTH RELEVANCE: Project Narrative Cartilage plays essential roles in formation and growth of the skeleton. Dysfunction in cartilage due to congenital or acquired conditions can lead to defects in body structures, growth retardation and degenerative cartilage diseases. This project will provide novel information on mechanisms regulating behavior and function of cartilage cells and will pave the way to uncover the causes of skeletal diseases.