Gingival crevicular fluid RANKL and OPG levels in periodontal diseases

Objectives: Receptor activator of NF-kappaB Ligand (RANKL) stimulates osteoclastogenesis and bone resorption, whereas its decoy receptor osteoprotegerin (OPG) blocks its action. This bi-molecular system is crucial for the regulation of bone remodelling, and disruption of their balanced expression may lead to bone resorption. The aim of this study was to compare the concentrations of RANKL, OPG and their relative ratio in gingival crevicular fluid (GCF) of patients with periodontal disease. Materials and Methods: GCF was obtained from healthy (n=21), gingivitis (n=22), chronic periodontitis (n=28), generalized aggressive periodontitis (n=25) patients. The concentrations of RANKL and OPG in GCF were measured by commercially available ELISA kits. Results: The concentration of RANKL was low in both health and gingivitis groups (6.8 ± 3.8 pg/μl and 9 ± 5.7 pg/μl, respectively). However, RANKL concentrations were markedly increased in both chronic and generalized aggressive periodontitis groups (370.7 ± 54.7 pg/μl, and 387.5 ± 42.8 pg/μl, respectively). In contrast OPG levels were highest in healthy subjects (408.1 ± 36.6 pg/μl), and reduced in gingivitis (167.6 ± 20.6 pg/μl), chronic periodontitis (119.6 ± 14.4 pg/μl), and generalized aggressive periodontitis (101.5 ± 10.2 pg/μl). There was no significant difference in RANKL and OPG levels between chronic and generalized aggressive periodontitis groups. The RANKL/OPG ratio was elevated by approximately 200 fold in both chronic periodontitis and generalized aggressive periodontitis, compared to health. Conclusions: The GCF concentrations of RANKL and OPG were differentially regulated in chronic periodontitis and generalized aggressive periodontitis, but not gingivitis, resulting in a massively increased RANKL/OPG ratio. This ratio was similar in both forms of periodontitis, and may be a key factor in determining attachment loss in periodontitis.