- Top of page
- Biomechanical Modulation of Chondrocyte Function: Abnormal Loading on Normal Cartilage or Normal Loading on Abnormal Cartilage?
- Is OA a Genetic Disease?
- Why Is Aging Cartilage Not Necessarily OA Cartilage?
- What Is the Contribution of Phenotypic Modulation of Chondrocyte Function?
- The Role of Inflammation: What Are the Critical Regulatory Molecules and Where Do They Come From?
- Catabolism Versus Anabolism: What Gets Turned on First?
- What Is the Role of the Subchondral Bone and Does OA Pathogenesis Start or Progress There?
- What Is the Source of Pain in the OA Joint and Can Anti-Pain Therapies Also Modify Structure?
- Are There Validated Approaches for Early Diagnosis Using Biomarkers and Non-Invasive Imaging Techniques?
- Are Tissue Engineering and Gene Therapy Viable Approaches in the Foreseeable Future?
- What Are the Lessons From Animal Models?
- Conclusion: Future Directions for Research
- Literature Cited
Osteoarthritis (OA) is characterized by degeneration of articular cartilage, limited intraarticular inflammation with synovitis, and changes in peri-articular and subchondral bone. Multiple factors are involved in the pathogenesis of OA, including mechanical influences, the effects of aging on cartilage matrix composition and structure, and genetic factors. Since the initial stages of OA involve increased cell proliferation and synthesis of matrix proteins, proteinases, growth factors, cytokines, and other inflammatory mediators by chondrocytes, research has focused on the chondrocyte as the cellular mediator of OA pathogenesis. The other cells and tissues of the joint, including the synovium and subchondral bone, also contribute to pathogenesis. The adult articular chondrocyte, which normally maintains the cartilage with a low turnover of matrix constituents, has limited capacity to regenerate the original cartilage matrix architecture. It may attempt to recapitulate phenotypes of early stages of cartilage development, but the precise zonal variations of the original cartilage cannot be replicated. Current pharmacological interventions that address chronic pain are insufficient, and no proven structure-modifying therapy is available. Cartilage tissue engineering with or without gene therapy is the subject of intense investigation. There are multiple animal models of OA, but there is no single model that faithfully replicates the human disease. This review will focus on questions currently under study that may lead to better understanding of mechanisms of OA pathogenesis and elucidation of effective strategies for therapy, with emphasis on mechanisms that affect the function of chondrocytes and interactions with surrounding tissues. J. Cell. Physiol. 213:626–634. © 2007 Wiley-Liss, Inc.