Expression of CHI3L1 and CHIT1 in osteoarthritic rat cartilage model. A morphological study.

Osteoarthritis is a degenerative joint disease, which affects millions of people around the world. It occurs when the protective cartilage at the end of bones wears over time, leading to loss of flexibility of the joint, pain and stiffness. The cause of osteoarthritis is unknown, but its development is associated with different fac- tors, such as metabolic, genetic, mechanical and inflammatory ones. In recent years the bio- logical role of chitinases has been studied in relation to different inflammatory diseases and more in particular the elevated levels of human cartilage glycoprotein 39 (CHI3L1) and chi- totriosidase (CHIT1) have been reported in a variety of diseases including chronic inflamma- tion and degenerative disorders. The aim of this study was to investigate, by immunohistochem- istry, the distribution of CHI3L1 and CHIT1 in osteoarthritic and normal rat articular cartilage, to discover their potential role in the develop- ment of this disease. The hypothesis was that the expression of chitinases could increase in OA disease. Immunohistochemical analysis showed that CHI3L1 and CHIT1 staining was very strong in osteoarthritic cartilage, especial- ly in the superficial areas of the cartilage most exposed to mechanical load, while it was weak or absent in normal cartilage. These findings suggest that these two chitinases could be func- tionally associated with the development of osteoarthritis and could be used as markers, so in the future they could have a role in the daily clinical practice to stage the severity of the dis- ease. However, the longer-term in vivo and in vitro studies are needed to understand the exact mechanism of these molecules, their receptors and activities on cartilage tissue.