Health consequences of mutant cartilage oligomeric matrix protein and its relationship to abnormal growth and joint degeneration.

Cartilage oligomeric matrix protein (COMP), an extracellular matrix protein, has been shown to enhance proliferation and mechanical integrity in the matrix, supporting functions of the growth plate and articular cartilage. Mutations in COMP cause pseudoachondroplasia (PSACH), a severe dwarfing condition associated with premature joint degeneration and significant lifelong joint pain. The MT (mutant)-COMP mouse mimics PSACH with decreased limb growth, early joint degeneration and pain. Ablation of endoplasmic reticulum stress CHOP signaling eliminated pain and prevented joint degeneration. The health effects of mutant COMP are discussed in relation to cellular/chondrocyte stress in the growth plate, articular cartilage and nearby tissues, and the implications for therapeutic approaches. There are many similarities between osteoarthritis and mutant-COMP protein-induced joint degeneration, suggesting that the relevance of findings in the joints may extend beyond PSACH to idiopathic primary OA.