|Ph.D Student||Goldberg-Satran Ruth|
|Subject||Gene Therapy of Rheumatoid Arthritis:|
Loal Administration of Osteoprotegerin
|Department||Department of Medicine||Supervisors||Dr. Gila Maor|
|Professor Nathan Karin|
Rheumatoid arthritis (RA) is a chronic inflammatory synovitis, leading to destruction of the articular cartilage and the subchondral bone.The damage at the subchondral bones is mediated mainly by the osteoclasts' (OC) Receptor Activator of Nuclear Factor-κB Ligand (RANKL) and the RANKL decoy receptor-osteoprotegerin (OPG), which inhibits OC activation. In the current study we explore the assumption that OPG has also a beneficial role in the articular cartilage, acting as a local growth factor that may have a protective effect on the joint. Mandibular condyle-derived primary chondrocytes - (MCDC) were treated with 20% (v/v) RA-derived synovial fluid (RASF), with IL-1b + TNFα and with recombinant OPG (rOPG) was added either alone or to RASF- or IL-1b + TNFα- treated cells. We report our findings of, OPG markedly improving the morphology, cell viability, proliferation and differentiation of the RASF-treated cells. The presence of specific binding sites for OPG was assayed by immunoprecipitaition (IP) with anti-OPG antibodies of OPG cross-linked to chondrocytes membranes. Using IP we found ~150 kDa OPG tyrosine kinase-specific binding sites. We have also found that OPG increases both ERK and AKT phosphorylation. We studied the effects of specific blocking of these pathways, using the inhibitors PD98059, LY294002 and Genistein, showing that the OPG stimulatory effects on viability, proliferation and differentiation are negatively affected. The present study provides direct evidence that OPG serves as a local growth factor in the cartilage, and may play a significant role in preventing the RA-induced damages to the joints.