Periodontal Expression of OPG/RANKL and IL-6/OSM in GCF

Objectives: This study aimed to identify and quantify IL-6/OSM/OPG/RANKL in the gingival crevicular fluid (GCF) of patients with periodontitis, and to clarify their correlation with disease severity. Methods: Ninety-five sites in 20 patients with generalized periodontitis were divided into 4 groups by sites based on probing depth (PD) and bleeding on probing (BOP). In periodontitis patients, GCF was obtained using sterile paper strips from clinically health sites (PD ≤3 mm without BOP, n = 12), mildly diseased sites (PD ≥3 mm with BOP, n = 23), moderately diseased sites (PD = 4~6 mm with BOP, n = 33), and severely diseased sites (PD > 6 mm with BOP, n = 27) in periodontitis patients. Fourteen clinically health sites from 4 periodontally health individuals were enrolled as the control group. Levels of IL-6/OSM/OPG/RANKL in GCF were determined by ELISA and expressed as total amounts (pg/site). The Kruskal-Wallis analysis of variance and Mann-Whitney U test were used for group comparisons. Spearman's rank correlation coefficients were calculated to define strong correlations between variables. Results: GCF IL-6, OSM, and RANKL, but not OPG, were elevated in diseased sites of patients with periodontitis. GCF IL-6 and OSM were correlated with the severity of periodontitis with the same correlation coefficient (p<0.01). However, the expression of OPG and RANKL showed no correlation to disease severity, but the content of RANKL in GCF was significantly positively correlated with those of IL-6 and OSM (p < 0.05). In addition, the expression of IL-6 was also positively correlated with that of OSM in the GCF of diseased sites (p <0.01). Conclusions: Expressions of the total contents of IL-6 and OSM in GCF were correlated with the severity of the periodontal lesions. Results also imply that IL-6 and OSM up-regulate RANKL expression and lead to the destructive sequence of the periodontium.