The role of lubricin in normal and pathological joint tissue: A contemporary review

Introduction The aim of this article was to critically review the literature about lubricin and its involvement in normal and pathological joint tissue. In particular, our research focused on new therapeutic approaches for the treatment of osteoarthritis related to lubricin. We reviewed the literature regarding lubricin expression. We examined the current literature by searching on PubMed and Scopus using appropriate keywords related to lubricin and joint tissue. Main research articles were then selected for review. Discussion Cartilage is the tissue that covers the ends of the bones where the bones meet to form a joint. The cartilage allows the bones to glide over one another with limited friction and wear. It contains proteoglycans such as aggrecan and lubricating fluidcontaining glycosaminoglycans such as hyaluronic acid. Osteoarthritis is the most common form of arthritis, a degenerative joint disease that mostly affects the cartilage. Lubricin, also commonly referred to as the superficial zone protein, is a glycoprotein specifically synthesised by chondrocytes located at the surface of articular cartilage. It has been shown that lubricin is critical to normal joint function, providing boundary lubrication of congruent articular surfaces under conditions of high contact pressure and nearzero sliding speed. Recent studies have demonstrated that administration of recombinant lubricin in the joint cavity would be effective in the prevention of cartilage degeneration in animal osteoarthritis models. It is a promising treatment for cartilage diseases, but further studies are necessary to shed light on its therapeutic value. Conclusion This critical review reported recent findings about the possible distribution of lubricin in some normal and pathological tissues and further provided new insights for future approaches in the treatment of osteoarthritis.