ObjectiveTo explore the suitable level and action time of 17-β estradiol and fluid shear stress（FSS） and their combined effect on the proliferation of rat osteoblasts in vitro.Methods MC3T3-E1 osteoblasts were adopted after subcultured and different concentrations of 17-β estradiol and FSS values were applied respectively on MC3T3- E1, the suitable level of 17-β estradiol and FSS were selected through MTT and alkaline phosphatase（ALP）. Then the two factors at the suitable level were applied simultaneously to MC3T3 -E1 to detect the proliferation activity.Results Seventeen-β estradiol
（10-8 mol·L-1） for 5 d and 12×10-5 N FSS for 60 min exhibited better effects on the proliferation activity than the other groups respectively, and the combined effect of both factors was better than any single-factor treated group.ConclusionBoth 17-β estradiol and FSS have a suitable threshold in promoting proliferation of osteoblasts, and two-factor treated group exhibits better effect than any other single -factor treated groups. Therefore 17-β estradiol and FSS have a synergetic action on differentiation and proliferation of osteoblasts.
