Enamel Matrix Proteins: Effect on Gene Expression with Bone Allografts

Objectives: The purpose of this study was to evaluate the effect of enamel matrix derivative(EMD) on gene expression when combined with non-osteoinductive and minimally osteoinductive bone allografts derived from the same donor. Methods: Freeze-dried bone allograft (FDBA; non-osteoinductive) and demineralized freeze-dried bone allograft (DFDBA; minimally osteoinductive) with 1% residual calcium content were processed from the same donor and verified with respect to osteoinductive activity using an athymic nude mouse model. Using the same model, 36 athymic nude mice (nu/nu) were divided into 6 equal treatment groups comparing graft alone (FDBA versus DFDBA) or graft in combination with EMD (2 and 4 mg). Explants were performed at 28 days and expression of interleukin-6 (IL-6), vascular endothelial growth factor (VEG-F), alkaline phosphatase (ALP) and osteocalcin (OCN) was determined using RT-PCR analysis. Results: EMD induced modest reductions in IL-6 and OCN gene expression (35% and 20%, respectively; N.S.) in the both FDBA and DFDBA groups. Similar levels of gene expression were found for VEG-F and ALP in both the FDBA and DFDBA groups. The expression of IL-6 was positively correlated (Gamma statistic) with VEG-F (0.97; p £ 0.001) and OCN (0.78; p £ 0.004) in this model. Conclusions: The results of the present study suggest that EMD supports similar patterns of selected gene expression (IL-6, VEG-F, ALP and OCN) when combined with allografts differing in mineral content and inherent osteoinductive activity.