Insulin-like Growth Factor 1 Can Promote Proliferation And Osteogenic Differentiation Of Human Dental Pulp Stem Cells Via MTOR Pathway

Aim To understand the effect of IGF-1 on the proliferation and osteogenic differentiation of dental pulp stem cel s(DPSCs).Methods We isolated and cultured DPSCs. Then identified multipotency of DPSCs by chondrogenic and adipogenic. Chondrogenic and adipogenic differentiation of DPSCs was testified by positive staining with toluidine blue and O il Red O. DPSCs were cultured and stimulated with 0-200 ng/ml IGF-1. The prolifereative effect and optimal concentration of IGF-1 on DPSCs was detected by CCK-8, determination of cell number and flow cytometry assay. DPSCs cultured in osteogenic differentiation medium with 100 ng/ ml IGF-1 for 3, 7, 14 and 21 days. At 21 days, treatment with the PI3 K inhibitor, LY294002, or the mTOR inhibitor, rapamycin. We detected ARS/ALP positive cells ratio. The expression level of osteogenic marker protein RUNX2, OSX, OCN, COL?and PI3K-AKT- mTOR pathway relative protein mTO R, p- mTO R, PI3 K, p-PI3 K, AKT, p-AKT and p-S6 K were detected by immunofluorescent staining and Western blot.Results DPSCs exhibited a fibroblast- like morphology, could differentiate into chondrogenic cells and adipogenic cells. In this study, we found that stimulated with 0-200 ng/ml IGF-1, DPSCs show a high proliferation ability, short population double time and decreased cell number in G1/G0 phase at 100 ng/ml. IGF-1 treated DPSCs exhibited higher protein expression levels of RUNX2/OSX at day 3 and OCN at days 7–14. After stimulated with IGF-1, the expression of p-mTOR and p-S6 K were increased, indicated that mTOR pathway was activated. While inhibit mTOR pathway, the effect of IGF-1 on DPSCs osteogenic differentiation was reversed.Conclusion Our study indicated that treated with IGF-1 could promote proliferation and osteogenic differentiation of DPSCs via mTOR pathways, which might have clinical implications for osteoporosis.