pPKC α regulates through integrin β 1 human gingival fibroblasts/Streptococcus mitis adhesion in response to HEMA

Aim To investigate in coculture of human gingival fibroblasts (HGFs) and Streptococcus mitis, the molecular mechanisms driving the response to 2-hydroxyethyl methacrylate (HEMA) in terms of eukaryotic/prokaryotic cell adhesion, signal transduction and apoptosis. Methodology The clinical strain S. mitis DS12, cultured in Trypticase soy broth was added to HGFs, obtained from fragments of healthy marginal gingival tissue and cultured in DMEM, treated with 3 mmol L-1 2-hydroxyethyl methacrylate (HEMA) for 48 h and processed for microscopic, western blotting and flow cytometric analyses. Results 2-hydroxyethyl methacrylate (HEMA) treatment increased the adhesion between S. mitis and HGFs, which seemed to be mediated by the PKC alpha/integrin beta 1 signalling system, improved by the presence of saliva. It also reduced the viability and the adhesion of HGFs to polypropylene substrate in terms of procollagen I and MMP3 expression. The presence of saliva and S. mitis reduced the number of necrotic HGFs and upregulated the expression of both procollagen I and MMP3. Conclusions These results shed more light on the biological and molecular events occurring in vitro in a coculture model that mimics the environment of the oral cavity with HEMA treatment. The key role played by oral bacteria and saliva in preventing inflammatory and toxic processes that occur in vivo in human gingival fibroblasts upon the release of dental material monomers is confirmed.