Common mechanisms of Osteoarthritis in three mouse models

描述(申请人提供)：骨关节炎(OA)形式的滑膜关节软骨变性是慢性残疾的主要原因之一，但其分子发病机制尚不清楚。因此，有必要开发和研究合适的动物模型。不成比例的小鼠症(DMM)和先天性脊柱骨盆发育不良(SEDC)小鼠品系是II型纤维胶原基因突变的结果，而软骨发育不良(CHO)小鼠品系是XI型纤维胶原基因突变的结果，这三种小鼠的特征都是骨骼发育不良。尽管它们来自不同类别的突变，具有不同的骨骼表型，但这三个突变都表现出相似的膝关节软骨早发性退行性变。因此，我们假设小鼠骨关节炎通过共同的病理途径进行，即使退化可能是由不同类型的侮辱引起的。为了验证这一假说，并确定与OA一致并为这三种小鼠模型所共有的生物分子变化，我们提出了以下具体目标：1)从组织学和超微结构角度研究SEDC膝关节和TMJ关节软骨中OA的特征；2)使用软骨退变和软骨细胞凋亡的生物标记物确定这三个突变体导致膝关节和TMJ关节软骨退变的共同模式；以及3)确定DMM、SEDC和CHO突变是否引起ER应激，足以触发关节软骨发育中的未折叠蛋白反应(UPR)，以及UPR是否激活炎症或细胞凋亡途径。组织化学将检测软骨基质大分子的质变，免疫组织化学将记录OA生物标记物(DDR-2、MMP3、MMP13、COL2-3/4M抗体、NITEGE和VDIPEN)和程序性细胞死亡的出现，所有这些都与组织病理学变化的启动有关。在这些突变体的杂合子中存在内质网应激反应的证据表明，未折叠的蛋白质被保留在细胞中，软骨发育过程中持续的内质网应激可能有助于早发性骨性关节炎的表型。因此，这一观察结果将成为开放式获取中的一个新的调查领域。识别所有三种鼠标模型的共同变化将是我们成功的关键。这些假定的普遍病理途径可能是治疗干预的新靶点和疾病诊断的分子标记物。公共卫生相关性：这项在三个小鼠模型上的研究将为OA的发病机制提供生物分子方面的见解，并为未来各种药物和基于基因的治疗方法的使用铺平道路。

DESCRIPTION (provided by applicant): Degeneration of synovial joint cartilage in the form of osteoarthritis (OA) is one of the leading causes of chronic disability, yet the molecular pathogenesis of OA is poorly understood. Therefore, the development and study of appropriate animal models is needed. The Disproportionate micromelia (Dmm) and spondyloepiphyseal dysplasia congenita (sedc) mouse strains are the result of mutations in the type II fibrillar collagen gene, whereas the chondrodysplasia (cho) mouse strain is the result of a mutation in the type XI fibrillar collagen gene, and all three are characterized by skeletal dysplasia. Though they result from different classes of mutations and have different skeletal phenotypes, all three mutants exhibit similar early-onset degeneration of knee-joint cartilage. Accordingly, we hypothesize that murine OA proceeds through common pathological pathways even though the degeneration may be initiated by different types of insults. To test this hypothesis and to identify the biomolecular changes that are coincident with OA and common to these three murine models, the following specific aims are proposed: 1) to characterize OA in sedc knee and temporomandibular joint (TMJ) articular cartilage histologically and ultrastructurally; 2) to identify common patterns of articular cartilage degeneration leading to OA in both knee and TMJ of the three mutants using biomarkers of cartilage degeneration and chondrocyte apoptosis; and 3) to determine whether the Dmm, sedc, and cho mutations cause ER stress that is severe enough to trigger the unfolded protein response (UPR) in developing articular cartilage, and whether that UPR activates inflammation or apoptosis pathways. Histochemistry will detect qualitative changes in cartilage matrix macromolecules, and immunohistochemistry will document the appearance of OA biomarkers (DDR-2, MMP-3, MMP-13, COL2-3/4m antibody, NITEGE and VDIPEN) and programmed cell death, all in relation to initiation of histopathological changes. Evidence of an ER stress response in the heterozygotes of these mutants would suggest that unfolded proteins are being retained in the cells and that continuous ER stress during cartilage development may contribute to the early-onset OA phenotype. This observation would thus become a new area of investigation in OA. Identification of changes that are common to all three mouse models will be the key to our success. These putative universal pathological pathways may represent new targets for therapeutic intervention and molecular markers for diagnosis of disease. PUBLIC HEALTH RELEVANCE: This study in three murine models will provide biomolecular insight into the pathogenesis of OA and pave the way for future investigations into the use of various drug and gene-based therapies.