Date on Master's Thesis/Doctoral Dissertation

5-2013

Document Type

Master's Thesis

Degree Name

M.S.

Department

Oral Biology

Committee Chair

Liang, Shuang

Author's Keywords

Periodontal disease; PD in mouse model; Mouse model; Ligature mouse model; P. gingivalis in mice; Sexual dimorphism in PD

Subject

Teeth--Diseases; Sex differences

Abstract

Background: Periodontal disease is an infection-driven chronic inflammatory disease. It occurs primarily from excessive inflammatory reactions that arise from complex exchanges between the host immune system and the tooth associated oral bacteria. It is the number one cause of tooth loss among adults. However, many factors confound results between males and females as to which sex is more susceptible to periodontal disease. Identifying the sex more prone to disease is integral in developing models of risk assessment and looking into the pathogenesis. Objective: To examine in vivo and in vitro the differences between male and female mice challenged with Porphyromonas gingivalis. Methods: Mice were divided into four groups consisting of male ligated, male nonligated, female experimental ligated, and female non-ligated. All groups were given a ligature around the second molar. Experimental groups were administered P. gingivalis while the controls being non-ligated. After 7 days, mice were euthanized and bone losses were determined. Bone losses were measured by taking the distance from the cementoenamel junction (CEJ) to the alveolar bone crest (ABC). Colony Forming Units (CFUs) were acquired from all groups as well. CFUs displayed bacterial clearance amongst the male and female mice. An oral gavage infection model was administered to confirm our ligature model results. Four groups were developed consisting of male experimentals, male sham infections, female experimentals, and female shams. From an in vitro perspective gingival tissue was harvested from each mouse and cytokine response levels were measured. Cytokine levels served as a method of looking into the immune system’s role in periodontal disease. Results: In comparison with male mice, female mice displayed significantly increased periodontal bone loss (p < 0.05) in both the ligature and oral gavage models, accompanied by elevated expression of pro-inflammatory cytokines. More oral bacteria were also detected in female mice than in males. In vitro experiments showed that macrophages from female mice respond to P. gingivalis with higher intensity. These findings along with the previously mentioned may contribute to more severe inflammation and bone losses in females. Conclusion: Female mice are more likely to exhibit persistent P. gingivalis infection, and develop higher levels of bone loss in comparison to their male counterparts. These occurrences differ from human studies in which males are the predominant gender for this disease.

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