In vitro modeling of host-parasite interactions: the 'subgingival' biofilm challenge of primary human epithelial cells

We describe the growth of a mature 'subgingival' in vitro biofilm, its composition during development, its ability to adapt to aerobic conditions and how we expose in vitro a HGEC monolayer to this biofilm. Challenging the host derived HGEC with the biofilm invoked apoptosis in the epithelial cells, triggered release of pro-inflammatory cytokines and in parallel induced rapid degradation of the cytokines by biofilm-generated enzymes.We developed an experimental in vitro model to study processes taking place in the gingival crevice during the initiation of inflammation. The new model takes into account that the microbial challenge derives from a biofilm community and not from planktonically cultured bacterial strains. It will facilitate easily the introduction of additional host cells such as neutrophils for future biofilm:host cell challenge studies. Our methodology may generate particular interest, as it should be widely applicable to other biofilm-related chronic inflammatory diseases.In most natural environments bacteria exist as highly structured dense surface attached aggregates designated as biofilms [1,2]. This applies also to bacteria colonizing the skin and human mucosa. Under certain conditions, biofilms may cause disease. Classical examples are gingivitis and chronic inflammatory periodontal disease. Dental plaque colonizing teeth initiates inflammation in the adjacent host gingival epithelium. The epithelial cells lining the crevice between the gum and the tooth are the first line of defense to the plaque bacteria [3]. Dental plaque has long been recognized as a complex polymicrobial biofilm [1,4-6]. The maturation of this biofilm involves a change in the microbiota from predominantly Gram-positive facultative anaerobes to Gram-negative anaerobic bacteria [7]. As the plaque accumulates, it induces inflammation in the adjacent host tissues and the biofilm over time extends under the gum, down the root surface, creating a niche favoring the growth of fasti