Regulation of cytokines by EMD in inflamed and wounded conditions

Periodontitis is characterized by inflammation as well as loss of periodontal attachment, collagen, and alveolar bone. In addition to its beneficial effects on periodontal regeneration, enamel matrix derivative (EMD) has been shown to decrease the incidence of postoperative pain and swelling. However, the cellular and molecular basis for the actions of EMD on early gingival wound healing is yet to be elucidated.

Objectives: This in vitro study was established to examine whether EMD modulates the synthesis of inflammatory mediators under normal, wounded, or inflamed conditions in periodontal ligament (PDL) cells.

Methods: PDL cells from six different donors were cultured in the presence or absence of EMD 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)-1 beta during the entire experimental intervals. The gene expression of IL-1 beta, IL-8, and tumor necrosis factor (TNF) alpha was determined by real-time RT-PCR. The statistical analysis was performed using the Wilcoxon-test (p<0.05).

Results: The gene expression of inflammatory cytokines was significantly upregulated under inflamed and wounded conditions. At 4 hours, significantly increased expression levels of IL-8 and TNF alpha were also observed in cells treated with EMD. EMD enhanced the inflammation- and wounding-induced expression of IL-1 beta and IL-8 at 4 hours. In contrast, IL-8 and TNF alpha were significantly reduced by EMD in inflammation and wounding at later time points.

Conclusions: These findings demonstrate that EMD regulates the synthesis of inflammatory cytokines under normal, wounded, and inflamed conditions. EMD might accelerate wound healing in vivo by an initial enhancement of the inflammatory process and a subsequent inhibition of the inflammatory cytokine expression.

This study was supported by a grant from the ITI Foundation (No: 487/2006).