Metformin enhances osteogenic differentiation of stem cells from human exfoliated deciduous teeth through AMPK pathway

Abstract Stem cells from human exfoliated deciduous teeth (SHEDs) are ideal seed cells in bone tissue engineering. As a first-line anti-diabetic drug, metformin has recently been found to promote bone formation. The purpose of this study was to investigate the effect of metformin on osteogenic differentiation of SHEDs and its underlying mechanism. SHEDs were isolated from the dental pulp of deciduous teeth from healthy children aged from 6 to 12, and their surface antigen markers of stem cells were detected by flow cytometry. The effect of metformin (10 - 200 μM) treatment on SHEDs cell viability, proliferation, and osteogenic differentiation was analyzed. The activation of adenosine 5'-monophosphate-activated protein kinase (AMPK) was determined by western blot assay for the AMPK phosphorylated at Thr172 (p-AMPK). SHEDs were confirmed as mesenchymal stem cells (MSCs) based on the expression of characteristic surface antigens. Metformin (10-200 μM) did not affect the viability and proliferation of SHEDs, but significantly increased the expression of osteogenic genes, the activity of alkaline phosphatase, matrix mineralization, and p-AMPK level in SHEDs. Compound C, a specific inhibitor of AMPK pathway, abolished metformin-induced osteogenic differentiation of SHEDs. Moreover, metformin treatment enhanced pro-angiogenic/osteogenic growth factors BMP2 and VEGF but reduced the osteoclastogenic factor RANKL/OPG expression in SHEDs. In conclusion, metformin could induce the osteogenic differentiation of SHEDs by activating the AMPK pathway and regulates the expression of pro-angiogenic/osteogenic growth factors and osteoclastogenic factors in SHEDs. Therefore, SHEDs, combined with metformin possesses therapeutic potential for bone regeneration and bone defect repair.