Effect of metformin on the behavior of dental pulp stem cells cultured on freeze-dried bone allografts.

BACKGROUND Considering the complications associated with autogenous bone grafting, the use of freezedried bone allograft (FDBA) granules may be considered as an alternative treatment plan. OBJECTIVES The aim of this study was to evaluate the effect of metformin on both the proliferation and osteogenic capability of dental pulp stem cells (DPSCs) cultured on FDBA granules. MATERIAL AND METHODS First, a pilot study was conducted only on DPSCs to confirm cellular viability and the osteoinducing effect of 100 μmol/L metformin. Next, the cells were loaded on FDBA granules and treated with and without metformin. Finally, the following analyses were performed: scanning electron microscopy (SEM) (cell attachment); the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay (proliferation); and alkaline phosphatase (ALP) activity analysis (osteogenic differentiation). RESULTS The SEM images revealed that metformin enhanced the adhesion of DPSCs on FDBA granules. In addition, metformin was shown to increase cell proliferation/viability from day 1 to day 7. Compared to the control, a significant difference was observed after 7 days of treatment. Metformin enhanced the osteogenic capability of FDBA in both standard and osteoinducing conditions. An increase in ALP activity was significant after 7 days of treatment. The positive effect of metformin on differentiation was significant in osteoinducing conditions. CONCLUSIONS Metformin can be applied as an additional osteoinductive factor in bone regeneration treatment. Moreover, scaffolds with controlled release of metformin can be considered a proper osteoinductive bone substitute that may lessen the complications related to applying allograft scaffolds alone.