Part I The Relative Expression Of Receptor Activator Of Nuclear Factor-Kappa B Ligand And Osteoprtegerin MRNA In Bone Tissue In Ovariectomized Mice

Receptor Activator of Nuclear Factor-Kappa B Ligand (RANKL), a membrane-bound protein expressed on osteoblasts and bone marrow stromal cells,is believed to induce osteoclast differentiation and activation by direct cell to cell interaction with osteoclast lineage cells.This induction is interrupted by osteoprotegerin (OPG),a soluble receptor of RANKL. Thus, OPG conteracts the stimulatory effect of RANKL on osteoclast differentiation and activation and it has been suggested that a high RANKL/OPG ratio is associated with an increased osteoclatogenesis while a low ratio with a decreased osteoclatogenesis. Previous in vitro studies indiated that other osteotropic hormones and factors such as PTH, 1, 25(OH)2D3, IL-1, IL-6 and TNF regulated osteoclastogenesis through the effect on RANKL/OPG ratio. The aim of the present study was to investigate the expression and regulation of RANKL and OPG in vivo in ovariectomized mice.forty female mice at six weeks of age were allocated into 5 groups, 8 in each. Group II > El and IVwere ovariectomized. Group IV were injected subcutaneusly with Benzoic estradiol for 5 weekstaneusly with Benzoic estradiol for 5 weeksone day after the ovariectomy. Group II and III were given placebo instead and sacrificed 1 and 5 weeks after the ovariectomy respectively. Group I and V were sham-operated and treated with placebo,then sacrificed l,and 5 weeks after ovariectomy. The tibia and femor were dissected out and mRNA levels of RANKL and OPG were studied using reverse transcription polyraerase chain reaction technique. The data showed that the mRNA level of RANKL was increased by ovariectomy while that of OPG was reduced in one week but increased in 5 weeks after ovariectomy, which seemed a compensation to the acceleration of bone loss. As a consequence, the ratio RANKL/OPG was increased by ovariectomy while reduced significantly when Benzoic estradiol was administrated.In summary, Our results indicate that Ovx-induced bone loss may be associated with the disturbance of RANKL/OPG.