Objective To compare the effect between glucocorticoid and ovariectomy on bone mass, bone turnover markers, estrogen level, and adipogenic differentiation by BMSCs, and to analyze the possible molecular mechanism. Methods Thirty six 3-month-old female Sprague Dawley rats were randomly divided to 3 groups, control group, methylprednisolone group (MP), and ovariectomized group (OVX). The rats in 3 groups were sacrificed in 8 weeks. The body mass, adrenal weight, and uterus weight were detected. BMD, BMC, and BA of the left femurs were detected using dual energy X-ray absorptiometry. The serum levels of PINP, β-CTX, and estrogen were determined using ELISA. Meanwhile, adipogenic differentiation by BMSCs was observed by oil red staining of the right femurs. The mRNA expression of Runx2, Col1α1, and MMP9 in the left tibia was detected using RT-PCR. Results In 8 weeks after the operation, the body mass in rats of MP group was significantly lower than that in control group and OVX group, while the body mass of OVX group was significantly higher than that in control group (P<0.05). BMC, BMD, and BA in rats of MP group and BMC and BMD in rats of OVX group were significantly lower than those in control group (P<0.05). In addition, BMC, BMD, and BA in MP group were significantly lower than those in OVX group (P<0.05). The levels of PINP and β-CTX in both groups were higher than those in control group, and they were significantly higher in MP group than in OVX group (P<0.05). The estrogen level in both groups were significantly lower than that in control group (P<0.05). The fat in bone marrow of both groups was more than that in control group. The expression of Runx2 mRNA in both groups was significantly down-regulated comparing with that in control group (P<0.05). The expression of Col1α1 and MMP9 mRNA was higher than that in control group, but the difference was not significant. Conclusion Both glucocorticoid and ovariectomy can induce high-turnover osteoporosis in rat, and glucocorticoid-induced bone loss is more severe. Both models can down-regulate estrogen level and promote adipogenic differentiation by BMSCs. The molecular mechanism may be related to the expression level of Runx2 mRNA. |