Effects of osteoprotegerin, RANK and RANKL on bone destruction and collapse in avascular necrosis femoral head.

Avascular necrosis of femoral head (AVFH) is a clinically recalcitrant disease of hip that leads to joint destruction. Osteoprotegerin (OPG), receptor activator of nuclear factor kappa-B (RANK) and RANK ligand (RANKL) regulates the balance, maturation and function of osteoclast and bone remodeling. This study aims to investigate molecular pathways which leads to AVN by studying expression profile of OPG, RANK and RANKL genes. Quantitative Real Time-PCR is used to evaluate mRNA expression of OPG, RANK and RANKL. mRNA and protein level in normal and necrotic tissue from 42 samples of ANFH specimens were analyzed. OPG and RANKL protein levels are estimated by western blotting. The results indicated that OPG mRNA levels are higher but not significantly different in necrotic tissue than that in normal tissue (P>0.05). Although expression of RANK and RANKL is significantly lower than that of OPG, RANK and RANKL mRNA levels are higher in necrotic tissue than normal tissue (P<0.05). Protein levels of OPG and RANKL show no significant difference. In conclusion, OPG, RANK and RANKL play important role in progress of bone remodeling in necrotic area and in disturbance of bone homeostasis, which might have an effect on bone destruction and subsequent collapse of hip joint.