Effect of inflammation and wounding on EMD-stimulated proliferation in vitro

Periodontitis is a multicausal inflammatory disease associated with loss of periodontal attachment, collagen, and alveolar bone. In order to support regeneration of lost periodontal structures, periodontal surgery is often combined with the application of enamel matrix proteins (EMD). One critical mechanism whereby EMD promotes periodontal regeneration is by stimulating the proliferation of periodontal ligament (PDL) cells. However, it is as yet unknown whether the beneficial actions of EMD are abrogated by inflammation or wounding due to the surgical procedure.

Objectives: This in vitro study was performed to investigate whether the EMD-stimulated proliferation of PDL cells is modulated by inflammation or wounding.

Methods: PDL cells from six different donors were cultured in the presence or absence of EMD under normal, wounded, or inflamed conditions up to 8 days. Cells were wounded by scraping the cell monolayers in a standardized manner at the beginning of the experiments. In order to mimic an inflammatory environment, cells were incubated with interleukin (IL)-1beta during the entire experimental intervals. At the end of experiments, the cell number was determined by an automatic cell counter. The statistical analysis was performed using the Wilcoxon-test (p<0.05).

Results: No significant differences between groups were observed after 1 day. However, EMD caused a significant increase in cell number in both normal and wounded conditions after 4 and 8 days. The stimulatory effect of EMD on cell proliferation was abrogated when cells were exposed to an inflammatory environment. The inhibitory effect of IL-1beta on the EMD-stimulated proliferation was dose-dependent.

Conclusion: These results suggest that the proliferative effect of EMD is diminished in inflamed periodontal tissues. However, a one-time wounding may not affect the beneficial actions of EMD regarding cell proliferation. These findings emphasize that an efficient antiinfectious and antiinflammatory periodontal treatment is critical prior to the application of EMD.

ITI Foundation (#487/2006)