Systemic Administration of Porphyromonas Gingivalis Lipopolysaccharide Induces Glial Activation and Depressive-Like Behavior in Rats.

BACKGROUND: Periodontitis is one of the most common chronic inflammatory disorders in adults. Although clinical studies have suggested a causal relationship between periodontitis and major depression (MD), the biological mechanisms by which periodontitis instigates MD are unknown. We investigated whether a systemic administration of lipopolysaccharide (LPS) from Porphyromonas gingivalis (Pg), a major Gram-negative pathogen of periodontitis, causes depressive-like behavior and glial activation in the hippocampus and the prefrontal cortex (PFC), which are MD-related brain regions. MATERIALS AND METHODS: Eight-week-old male Sprague Dawley rats were randomly divided into a behavioral test group and an immunohistochemistry group. The rats in each group were further assigned to the sham injection (saline) and Porphyromonas gingivalis-lipopolysaccharide (Pg-LPS) injection protocols. The rats received an intraperitoneal injection of saline or Pg-LPS with gradually increasing doses (day 1: 0.5, day 2: 0.5, day 3: 0.75, day 4: 0.75, day 5: 1.0, day 6: 1.0, and day 7: 1.0 mg/kg of body weight) for seven consecutive days. After the systemic administration, the behavior test group underwent the forced swimming test (FST) and Y-maze test. For the immunohistochemistry group, we quantified the immunoreactivity for microglial Iba-1 (ionized calcium-binding adapter molecule 1) and astrocytic glial fibrillary acidic protein (GFAP) in the hippocampus (dentate gyrus [DG], cornu ammonis [CA1 and CA3]) and PFC (prelimbic [PrL] and the infralimbic [IL]) areas. RESULTS: The FST immobility time in the Pg-LPS group was significantly longer than that in the sham group. In the Y-maze test, a significant decline in spontaneous alternation behavior was observed in the Pg-LPS group compared to the sham group. The peripheral administration of Pg-LPS significantly increased the immunoreactivity for Iba-1 in the CA3 and PrL. Pg-LPS injection significantly increased the immunoreactivity for GFAP in the DG, CA1, and CA3. CONCLUSIONS: The major result of this study is that a repeated systemic administration of Pg-LPS caused depressive-like behavior and both microglial and astrocytic activation in rats. This finding may comprise biological evidence of a causal relationship between periodontitis and MD.

Implementation of a personal identification system using alveolar bone images.

OBJECTIVE: In recent years, personal identification has been performed using antemortem panoramic X-ray images and postmortem-CT images. Using these, we have developed a personal identification method that focuses on the alveolar bone. This study examined the effectiveness of this method and aimed to implement a reproducible system. MATERIALS AND METHODS: For personal identification, a total of 633 CT images and panoramic X-ray images belonging to three groups with different conditions were used.　These images were 160 sets in the same person group and 96,820 in the other groups. The similarity of alveolar bone images was calculated using the landmark method of Procrustes analysis. The processes were system implemented and the methodology was validated. RESULTS: The ability to identify between the same person group and other person groups showed 0.9769 as the area under the curve (AUC: ROC curve). At the cutoff value of 4.978, there was no false rejection rate, but false acceptance rate was slightly higher. CONCLUSION: This method was useful as a screening method for personal identification. In addition, system implementation was efficient and reduced human error. In the future, we aim to realize a more efficient personal identification method using distortion-corrected images and including auto-detective landmarks using deep learning.