COMP Is a Biomarker of Cartilage Destruction, Extracellular Matrix and Vascular Remodeling and Tissue Repair

This review covers the roles of cartilage oligomeric matrix protein (COMP), an established biomarker of cartilage breakdown in pathological tissues in osteoarthritis, and in emerging areas in extracellular matrix and vascular remodeling associated with trauma, fibrosis and cancer. COMP is produced by chondrocytes, tenocytes, myofibroblasts, and in some specialized tissue contexts, endothelial and vascular smooth muscle cells. COMP expression by tendon and cartilage cells is sensitive to weight bearing and tensional mechanical stimulation. Vascular smooth muscle cells are sensitive to shear forces which regulate COMP expression in vascular tissues in atherosclerosis and in carotid stenosis. COMP is a multivalent bridging molecule that stabilizes tissues. It facilitates the signaling of TGF-β and BMP-2 in chondrogenesis, osteogenesis, tissue fibrosis, vascular and ECM remodeling and tumor development by providing a multimeric environment through which growth factor binding and receptor activation can occur. Engineered COMP proteins have been used as molecular templates in the development of chimeric therapeutic proteins of potential application in repair biology. Tie2 (Angiopoietin-1 receptor, Tyrosine-protein kinase receptor TEK), when activated by an engineered COMP-inspired angiopoietin-2 pentamer, is a potent angiogenic molecule of obvious application in wound healing. COMP's multifunctional properties show it is much more than a biomolecular marker protein through its ability to participate in many biological processes. Further studies are warranted to fully explore the biology of this fascinating molecule, particularly in the wound repair processes.