Effects of 17 β-estradiol and progesterone on the cell proliferation and differentiation of cultured rat osteoblasts

Objective: To investigate the effect of 17 β-estradiol (E2),progesterone (P) or E2 plus P on the proliferation and differentiation of rat osteoblast (ROB) in vitro.Methods:The neonatal ROB were cultured with phenol red-free media containing steroid-free fetal calf serum. The cells were respectively exposed to vehicle (control group),P (P group) and E2 plus P (E2+P group). The cell proliferation was assessed by MTT assay;the level of type 1 collagen (Col1) mRNA in ROB was measured with reverse transcriptase-polymerase chain reaction (RT-PCR);the concentration of carboxyterminal propeptide of type 1 collagen (P1CP) in medium was determined by radioimmunoassay;the calcium nodule in the cell layer was stained with Von Kossa method and the total calcium content analysed by atomic absorptiometry.Results: (1) The cell proliferation in P group was higher than that of control group (P0.01),while those in E2 and E2+P group were similar to the control;(2) The levels of Col1 mRNA and P1CP in E2,P and E2+P groups were higher than control group (P0.01 or 0.001);(3) The cellular AKP content,calcium nodule number and total calcium content in E2 and E2+P group were higher than those of control group (P0.01),while those in E2 group changed little when compared with control group.Conclusion :These results suggested that P and E2 +P could promote bone matrix formation and calcification ;P could promote the cell proliferation ;E2 could only stimulate bone matrix expression .These might be one of the mechanisms of P or E2 plus P to enhance bone formation .