Neutrophil recruitment and function mediate sexual dimorphism in experimental periodontitis

Periodontitis is a chronic inflammatory disease that has been shown to have biological sex-based differences with respect to disease prevalence and severity. Understanding the mechanisms behind this difference may highlight potential adjunctive therapies for periodontal disease that could address differences in disease progression between males and females. Our objective was to examine clinical and immunological differences between male and female mice in periodontal disease progression using the ligature-induced periodontitis model. Periodontitis was induced in male and female C57BL/6J mice for 7 or 21 days, at which point maxillae were characterized for bone loss by microCT or immune infiltrate by flow cytometry. Ligature-induced periodontitis led to alveolar bone loss at both 7 and 21 days in both female and male mice. Males and females had similar linear bone loss 7 days post-ligature placement, while male mice had significantly more linear bone loss by day 21. Male mice had significantly more immune cells in their maxillae 7 days post-ligature placement compared to female mice (p < 0.05). Both male and female mice showed a shift in immune populations towards neutrophils, with no significant difference between males and females. Neutrophil counts were elevated in male mice on day 7 but not day 21, while female mice did not have any statistically significant changes in neutrophil counts. Neutrophil depletion using a Ly6G antibody limited bone loss in male but not female mice relative to isotype antibody-treated controls. Analysis of single-cell sequencing data from human patients with periodontitis showed that, similar to males in our mouse model, male patients with periodontitis showed enrichment for CXCR4 expression with low CD62L (SELL). Padi4 knockout in male and female mice had decreased bone loss at 21 days post-ligature compared with WTs and still displayed sexual dimorphism. Together, these data suggest a mechanistic role for neutrophil inflammation in sexual dimorphism in periodontitis.