Influence of pro-/anti-inflammatory conditions on the effect of EMD

Method: PDL-fibroblasts and osteoblasts were cultured on EMD coated/non coated culture dishes for up to 12 days. The cells were treated with IL-1b (simulating proinflammation) and / or dexamethasone (simulating neutralization/antiinflammation). To characterize the effects of EMD, IL-1b and dexamethasone on the cells, the metabolic activity, quantification of mineral deposits and hard tissue formation were determined using MTS-test, measurements of catalytic activity of alkaline phosphatase (ALP), of concentration and mRNA expression of OPG and RANKL. IL-6, PGE₂ and COX-2 were chosen to examine inflammation.

Result: EMD significantly increased ALP-activity in osteoblasts, inhibited it in fibroblasts, inhibited the concentration and mRNA expression of OPG in osteoblasts. EMD initially induced an increase of the IL-6- andPGE₂-concentration in longer term a decrease. In the two cell lines EMD inhibited mRNA expression of COX-2. IL-1β was a strong activator of OPG- and IL-6 release and COX-2 expression and an inhibitor of PGE₂release. Dexamethasone inhibited OPG- and IL-6-release, PGE₂-concentration and COX-2 expression. Both, IL-1β and dexamethasone increased the activity of the ALP. The mRNA expression of RANKL was increased by EMD, IL-1β and dexamethasone in osteoblasts.

Conclusion: It is concluded that EMD initially stimulates inflammatory reactions in fibroblasts and osteoblasts but in long term it is an inhibitor of inflammation. EMD stimulates bone turnover and acts relatively independent of the surrounding inflammatory milieu.