TRAIL IN ON OSTEOBLASTS. COMPARISON WITH OA AND OSTEOSARCOMA CELL LINES. INFLUENCE OF IL-6 AND SIL-6R

Introduction: Abnormalities of mesenchymal stem cells and osteoblastic cells (Obs) might play a role in producing bone collapse due to insufficient repair of the necrotic area in osteonecrosis of the femoral head (ON). Osteoblast and osteocyte apoptosis should be increased at the osteonecrotic site. Materials and Methods: We compared the TRAIL (TNF-related apoptosis-inducing ligand) cytotoxicity in primary Obs isolated from femoral heads from patients with ON or osteoarthritis (OA) and on two human osteosarcoma cell lines, MG-63 and SaOS 2 . Results and Discussion: We showed that ON but also OA Obs were sensitive to TRAIL. We also observed TRAIL cytotoxicity on MG-63 but not SaOS 2 cells. Moreover, we saw that TRAIL negatively regulated Akt and ERK survival pathways in MG-63 cells. We also investigated the IL-6 influences on apoptotic response of Obs to TRAIL. Even though decreased IL-6 and sIL-6R levels were observed at peripheral sites of the ON in regard to the levels produced in the iliac crest, IL-6 had no protective effects on TRAIL-induced apoptosis in ON Obs and only a weak protective effect in MG-63 cells. However, TRAIL stimulated IL-6 production in MG-63 cells and, cells and OA Obs, suggesting to a lesser extend, in SaOS 2 other roles of TRAIL in the bone environment.