Site-specific analysis of gene expression in early osteoarthritis using the Pond-Nuki model in dogs

BACKGROUND: Osteoarthritis (OA) is a progressive and debilitating disease that often develops from a focal lesion and may take years to clinically manifest to a complete loss of joint structure and function. Currently, there is not a cure for OA, but early diagnosis and initiation of treatment may dramatically improve the prognosis and quality of life for affected individuals. This study was designed to determine the feasibility of analyzing changes in gene expression of articular cartilage using the Pond-Nuki model two weeks after ACL-transection in dogs, and to characterize the changes observed at this time point. METHODS: The ACL of four dogs was completely transected arthroscopically, and the contralateral limb was used as the non-operated control. After two weeks the dogs were euthanatized and tissues harvested from the tibial plateau and femoral condyles of both limbs. Two dogs were used for histologic analysis and Mankin scoring. From the other two dogs the surface of the femoral condyle and tibial plateau were divided into four regions each, and tissues were harvested from each region for biochemical (GAG and HP) and gene expression analysis. Significant changes in gene expression were determined using REST-XL, and Mann-Whitney rank sum test was used to analyze biochemical data. Significance was set at (p < 0.05). RESULTS: Significant differences were not observed between ACL-X and control limbs for Mankin scores or GAG and HP tissue content. Further, damage to the tissue was not observed grossly by India ink staining. However, significant changes in gene expression were observed between ACL-X and control tissues from each region analyzed, and indicate that a unique regional gene expression profile for impending ACL-X induced joint pathology may be identified in future studies. CONCLUSION: The data obtained from this study lend credence to the research approach and model for the characterization of OA, and the identification and validation of future diagnostic modalities. Further, the changes observed in this study may reflect the earliest changes in AC reported during the development of OA, and may signify pathologic changes within a stage of disease that is potentially reversible

Articular cartilage and changes in Arthritis: Cell biology of osteoarthritis

The reaction patterns of chondrocytes in osteoarthritis can be summarized in five categories: (1) proliferation and cell death (apoptosis); changes in (2) synthetic activity and (3) degradation; (4) phenotypic modulation of the articular chondrocytes; and (5) formation of osteophytes. In osteoarthritis, the primary responses are reinitiation of synthesis of cartilage macromolecules, the initiation of synthesis of types IIA and III procollagens as markers of a more primitive phenotype, and synthesis of active proteolytic enzymes. Reversion to a fibroblast-like phenotype, known as 'dedifferentiation', does not appear to be an important component. Proliferation plays a role in forming characteristic chondrocyte clusters near the surface, while apoptosis probably occurs primarily in the calcified cartilage