Abstract: PURPOSE: Different concentrations of 17 β-estradiol (E₂) were applied in the osteogenic differentiation of rat bone mesenchymal stem cells (BMSCs), and the proliferation and apoptosis of BMSCs were explored. METHODS: BMSCs were obtained from the femurs and tibias of SD rats. The proliferation curve was conducted to rBMSCs in culture medium containing 0, 10^-9, and 10^-7 mol/L 17 β-estradiol by CCK-8 for 7 days. Annexin V and PI for flow cytometry were applied to detect the impact of E₂ on apoptosis of rBMSCs. After 1, 7, 11 and 14 days of osteogenic induction, the activity of alkaline phosphatase (ALP) was assayed; ALP staining was performed on day 7 and day 14; Alizarin red staining for calcium deposits was carried out on day 21. Concentrations of 0, 10^-9, and 10^-7 mol/L 17 β-estradiol were administrated to rBMSCs for real-time PCR of osteogenic related genes on day 1, 3, 5, 7, 14, and day 21. The data was statistically analyzed using SPSS 19.0 software package. RESULTS: The effect of 17 β-estradiol on proliferation and apoptosis of rBMSCs was not obvious. However, after osteogenic induction, the ALP activity and Alizarin red staining were significantly stronger in the groups containing 17 β-estradiol. Especially, the use of 17 β-estradiol with the concentration of 10^-9 mol/L enhanced the expression of osteogenic related genes like RUNX2, ALP, COL I, and OCN, which was significantly higher than other groups. CONCLUSIONS: 17 β-estradiol promotes osteogenic differentiation of BMSCs in a dose-dependent pattern in vitro.

Key words: Estrogen, Bone mesenchymal stem cells, Osteogenic differentiation