gms | German Medical Science

Objectives: Periodontitis is an inflammation of the tooth surrounding tissue, which has been proposed to result in inflammatory jaw bone destruction. Another disease of the oral cavity is tooth resorption (TR). This dental condition is associated with the destruction of dental mineralized tissue. Among other species, cats and humans suffer from these dental diseases. In previous studies we found complement and mast cells involved in osteoclastogenesis under inflammatory conditions. We utilized a translational model of feline orodental diseases to investigate the underlying pathologic molecular mechanisms.

Methods: The teeth and the gingiva samples were collected from domestic cats, which had an appointment for dental treatment under anesthesia. The owners' consent was obtained and an owner survey was completed for each cat. Based on the clinical findings we categorized the samples in different groups: gingivitis, periodontitis or TR. However, if signs of tooth resorption were visible in the µCT scans, teeth are assigned to the TR group independently from the clinical classification. 8 µm sections of the samples were processed. Performed stainings: toluidine blue and histamine staining for mast cells, TRAP staining for osteoclasts, von Kossa staining for calcium crystals, immunohistochemical staining for complement C3, C5a and receptor of C5a (C5aR); ANOVA followed by multiple comparison Tukey's post-hoc test *p ≤ 0.05.

Results and conclusion: The staining for osteoclasts revealed significantly increased cell count on bone (p ≤ 0.01) and tooth surface (p ≤ 0.05) in the TR group. Calcium crystal concentration was also significantly increased in TR (p ≤ 0.05) compared to gingivitis group, as well as mast cell count (p ≤ 0.05). In TR group complement C3 positive cells were significantly increased compared to both gingivitis and periodontitis (p ≤ 0.05). Moreover, there was a by trend increase in C5a positive cells in TR and periodontitis compared to gingivitis. No significant difference in expression of C5aR between the groups were seen.

This study sought to determine pathologic molecular mechanisms underlying periodontitis and TR. Here, mast cells were significantly increased in TR compared to gingivitis. Moreover, calcium crystals were present in gingiva sections in the TR group. In humans, primary hyperoxaluria, a disease characterized by deposition of oxalate crystals in several oral tissues, is known for causing root resorption. Further, crystal deposition is known for leading to complement activation. Interestingly, C3 positive cells were significantly increased in TR compared to gingivitis and periodontitis. This is in conformity with earlier studies revealing C3 as modulating factor for osteoclasts. Understanding molecular mechanisms of jaw bone loss may contribute to develop new therapeutic strategies to prevent progressive bone loss and enhance musculoskeletal regeneration.