Altered Gas6/sMerTK Balance in Gingival Crevicular Fluid Across Periodontal Health, Gingivitis, and Periodontitis: A Cross-Sectional Study

Background/Objectives: Periodontitis reflects a dysregulated inflammatory response in which impaired resolution and efferocytosis may play a central role. The TAM receptor MerTK and its ligand growth arrest-specific-6 (Gas6) are key regulators of these processes; however, their profile in gingival crevicular fluid (GCF) across the periodontal disease spectrum remains unclear. This cross-sectional study aimed to evaluate GCF levels of Gas6 and soluble MerTK (sMerTK) in individuals with periodontal health, gingivitis, and periodontitis, and to examine their associations with clinical periodontal parameters. Methods: Eighty-one systemically healthy adults were enrolled into three groups: periodontal health, gingivitis, and periodontitis. Full-mouth clinical periodontal measurements were recorded. Gas6 and sMerTK levels were quantified by enzyme-linked immunosorbent assay. Results: sMerTK progressively decreased from periodontal health to gingivitis and periodontitis, with significant differences among all groups (p < 0.001). Gas6 total amount was higher in the diseased groups, whereas its concentration decreased. The Gas6/sMerTK ratio increased stepwise with disease severity (p < 0.001), showing positive correlations with clinical attachment loss and other clinical periodontal parameters, while sMerTK showed inverse correlations. Conclusions: These findings suggest that the local GCF Gas6/sMerTK balance is altered across periodontal states, primarily due to a marked reduction in sMerTK. The Gas6/sMerTK ratio may represent a potential exploratory indicator of periodontal inflammatory status, although longitudinal validation is required.