Although the mechanism of the increase in bone resorption induced by estrogen deficiency is still controversial, recent studies have suggested that estrogen may modulate the secretion of bone resorption cytokines that are produced in the bone
microenvironment and influence bone remodeling. Among them, TNF-α promotes bone resorption by stimulating the activity of mature osteoclasts and osteoclastogenesis, and the production of this cytokine is mediated by estrogen. We performed this
study to
evaluate the effect of ovariectomy on femur bone mineral density and levels of TNF-αin the culture media of bone marrow monocytes.
The experimental animals were 15 female Sprague-Dawley rats that were 6 weeks of age and weighed an average of 172.8 gm at the beginning of the study. Bilateral ovariectomy were performed in all rats from a vental approach. Bone mineral
density(BMD) of
femur and levels of TNF-αof culture media of peripheral blood and bone marrow monocytes were measured before and 8 weeks after operation with using DPX-L and ELISA assay, respectively. Seum levels of LH, FSH, E2 were measured by RIA assay.
BMD of femur was lower after ovariectomy(0.20±0.03 g/cm2) than before ovariectomy(o.25±0.06 g/cm2)(p<0.05). Serum levels of LH, FSH were higher after ovariectomy(0.71±0.29mIU/ml, 10.27±1.21 mIU/ml) than before ovariectomy(0.17±0.04 mIU/ml,
2.79±0.61mIU/ml)(p<0.01) and serum level of E2 was lower after ovariectomy(6.37±4.75 pg/ml) than before ovariectomy(7159.16±385.82 pg/ml)(p<0.01), respectively. Levels of TNF-αin culture media of bone marrow monocytes were higher after
ovariectomy(59.26±6.56 pg/ml) than before ovariectomy(23.37±4.13 pg/ml)(p<0.01), but there were no statistically significant differences in culture media of the peripheral blood monocytes(before ovariectomy: 22.96±3.62 pg/ml ; after
ovariectomy:
23.55±2.98pg/ml)(P>0.05).
It is possible that increased production of TNF-αin estrogen deficiency induced by ovariectomy occures in the bone microenvironment and this ccytokine may play a critical causal role in inducing bone loss.
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