Expression of receptor activator of nuclear factor κB ligand and osteoprotegerin in chronic apical periodontitis

Objective:To investigate the expression of key mediators that regulate bone resorption, receptor activator of nuclear factor-κB ligand (RANKL) and osteoprotegerin (OPG) in human perapical granuloma (PG) and radicular cyst (RC) characterized by periapical bone destruction. Methods:Immunohistochemical technique was performed using monoclonal antibody to detect RANKL and OPG expression in PG (n= 20 ) and RC (n= 20 ). As control group, healthy periodontal ligament tissues (n = 6 ) were obtained from teeth with orthodontic indication of extraction. Results: The RANKL protein expression was significantly higher in PG (43.74 ±8.40) and RC (40.33 ±7.53) than in control group (15.47±2.59, P = 0.000) , but no statistical significance could be found between PG and RC groups(P= 0.161) .The expression of OPG in PG (27.81 ±5.17), RC (26.35 ±3.86) and control group (24.33 ±3.50) show no statistical significance (P 0.05). Moreover, RANKL/OPG ratio in PG (1.59±0.26) and RC (1.54±0.24) was much higher than that in control group (0.64±0.10, P =0.000), however the ratio of RANKL/OPG showed no significant difference between PG and RC groups (P= 0.504) . Conclusion:RANKL and OPG were observed in the periapical lesions. RANKL may be responsible for bone resorption in periapical lesions. RANKL and OPG may play an important role in the development of periapical lesions.