[Effects of progestin on proliferation and differentiation of osteoblasts]

To study the effects of progesterone and levonorgestrel (LNG) on proliferation and differentiation of human normal osteoblasts and human osteosarcoma cell line MG-63.

Cell proliferation was tested by 3-[4,5-Dimethylthiazolzyl]-2,5-Diphenyl Tetrazolium Bromide (MTT) assay. The expression of c-fos, c-jun and osteocalcin was measured by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) or immunocytochemistry.

Compared to the control group, progesterone at concentrations of 10(-10) mol/L, 10(-8) mol/L and 10(-6) mol/L increased the proliferation of human osteoblasts by 9.8%, 23.0% and 32.8% respectively and that of MG-63 cells by 7.8%, 15.6% and 21.8% respectively. LNG at concentrations of 10(-10) mol/L, 10(-8) mol/L and 10(-6) mol/L increased the proliferation of human osteoblasts by 12.5%, 21.9% and 32.8% respectively and that of MG-63 cells by 9.6%, 14.4% and 23.0% respectively. Progesterone and LNG upregulated c-fos and c-jun mRNA and protein in a dose-dependent manner. Likewise, progesterone and LNG increased the expression of osteocalcin mRNA in human osteoblasts by 12.2%, 23.7%, 45.5% and 18.6%, 32.1%, 60.3% respectively. The effects of LNG were greater than those of progesterone. Meanwhile, the expression of osteocalcin mRNA in MG-63 cells was not influenced by either progesterone or LNG.

Progesterone and LNG stimulate proliferation of osteoblasts and increase the expression of c-fos, c-jun and osteocalcin.