Background: Effects of Fusobacterium nucleatum (F. nucleatum) biofilm on epithelial cell proliferation, apoptotic cell death, and basement membrane constituent collagen IV production were examined in an organotypic dento-epithelial (OD-E) model.
Methods: The OD-E model was constructed by seeding keratinocytes on fibroblast-containing collagen gels and by placing tooth pieces on top. A 3-day-old biofilm either a laboratory strain (American Type Culture Collection [ATCC] 25586) or a clinical strain (Anaerobe Helsinki Negative [AHN] 9508) of F. nucleatum was placed on the top of the model. The coculture was incubated ≤24 hours. The expression and localization of Ki-67, caspase-3, and collagen IV were examined by immunohistochemistry.
Results: Hematoxylin and eosin staining showed epithelial migration and lateral sprouting into the connective tissue matrix in F. nucleatum OD-E cocultures. The proliferation pattern of the in vitro dento-epithelial junction was changed. In controls without bacterial challenge, the Ki-67 expression was abundant in the cells attached to the tooth, whereas in F. nucleatum biofilm-treated cultures, the Ki-67-expressing cells were more often in the connective tissue-facing side of the epithelium. An apoptotic marker caspase-3 was expressed in controls and in F. nucleatum laboratory strain ATCC cocultures throughout the epithelium, in contrast to cultures treated with F. nucleatum clinical strain AHN, in which caspase-3 was absent. Collagen IV stainings were negative in both controls and F. nucleatum cocultures.
Conclusion: F. nucleatum biofilm coculture with OD-E model causes lateral sprouting of the epithelium with an altered epithelial proliferation pattern, resembling the histologic changes seen in vivo in the early pathogenesis of periodontal disease.