[Effects of calcitonin on osteoblast cell proliferation and OPG/RANKL expression: experiment with mouse osteoblasts].

OBJECTIVE: To investigate the effects of calcitonin on the proliferation of osteoblasts and the OPG/RANKL expression therein. METHODS: Osteoblasts were separated by enzyme digestion methods from the cranial bones of 30 newborn mice, cultured, and inoculated in 96-well plate. Calcitonin of the concentrations of 10, 40, and 80 IU/L was administrated into the culture medium for 24, 48, and 72 hours. The proliferation of osteoblasts was detected by MTT method. Flow cytometry was used to analyze the cell cycle. The mRNA expression of osteoprotegerin (OPG) and RANKL and protein expression of OPG were examined by RT-PCR and ELISA respectively. RESULTS: The proliferation rates of the osteoblasts exposed to the calcitonin of the concentrations of 40 and 80 IU/L for 24. 48, and 72 hours cell were all significantly higher than those of the blank control group (P < 0.05, P < 0.01). The index of osteoblasts at the G1 phase was significantly lower and the indexes of the osteoblasts at the S phase and G2-M phase were significantly increased after exposure to calcitonin (all P < 0.01). The OPG mRNA expression of the osteoblasts exposed to 80 IU/L calcitonin was significantly higher and the RANKL mRNA expression was significantly lower compared with the control group (P < 0.05). The OPG protein expression of the osteoblasts exposed to 80 LU/L calcitonin was significantly higher than that of the control group at different time points (P < 0.05, P < 0.01). CONCLUSION: Calcitonin increases the osteoblast proliferation and the OPG mRNA expression in the osteoblasts while RANKL mRNA expression in the osteoblasts is inhibited.