Topical Application of Aggregatibacter Actinomycetemcomitans Cytolethal Distending Toxin Induces Cell Cycle Arrest in the Rat Gingival Epithelium in Vivo

Background: Aggregatibacter actinomycetemcomitans is one of the etiological pathogens implicated in the onset of periodontal disease. This pathogen produces cytolethal distending toxin (CDT) that acts as a genotoxin to induce cell cycle arrest and cellular distension in cultured cell lines. Therefore, CDT is a possible virulence factor; however, the in vivo activity of CDT on periodontal tissue has not been explored. Here, CDT was topically applied into the rat molar gingival sulcus; and the periodontal tissue was histologically and immunohistochemically examined.

Materials And Methods: Recombinant purified A. actinomycetemcomitans CDT was applied to gingival sulcus of male Wistar rats and tissue samples were immunohistochemmically examined.

Results: One day after application, infiltration of neutrophils and dilation of blood vessels in the gingival connective tissue were found. At day three, desquamation and detachment of cells in the junctional epithelium was observed. This abrasion of junctional epithelium was not observed in rats treated with mutated CDT, in which a His274Ala mutation is present in the CdtB subunit. This indicates the tissue abrasion may be caused by the genotoxicity of CdtB. Expression of the proliferating cell nuclear antigen (PCNA), a marker for proliferating cells, was significantly suppressed using CDT treatment in the junctional epithelium and gingival epithelium.

Conclusion: Using the rat model, these data suggest CDT intoxication induces cell cycle arrest and damage in periodontal epithelial cells in vivo.