Experimental Study Of The Osteoprotegerin And The Ovariectomized Rat Model Of Osteoporosis

【Objective】 To establish the rat model of osteoporosis by ovariectomy, and observe the changes of bone structure in rats at different time including the growth period,adulthood, ovariectomized period and sham-ovariectomized period, in order to explore the best establishing model time and detect methods of rat model of osteoporosis. Meanwhile, observe the expression of osteoprotegerin in ovariectomized rats tibia at different period and the relationship between OPG and other markers, clarify the role of OPG on osteoporosis. 【Methods】 SD female rats were randomly divided into the growth period groups(three months and five months),adulthood group(six months),ovariectomized (OVX)(ovariectomized at six months) and sham-ovariectomized(SHAM) groups(one month, two months, three months after operation). Serum AKP and TRAP were measured by chromatometry. The whole-body bone mineral density(BMD) and bone mineral content(BMC) were measured by Dual-energy X-ray absorptiometry. The rats of each group were sacrificed at proper time and histomorphometry of the tibia, including percent of trabecular area (Tb.Ar%),trabecular thickness(Tb.Th),trabecular number(Tb.N) and trabecular separation(Tb.Sp) were evaluated by computer-assisted image analysis software, and the content of OPG determined by immunohistochemistry, which included mean optical density (MOD) ,positive area density in bone trabecula and total positive area of cancellous bone, were evaluated by computer-assisted image analysis and semiquantitative analysis. Correlation analysis was made between BMD, BMC and histomorphometrical markers, between OPG detected markers and AKP, TRAP, BMD.【Results】 1. BMC and Tb.Th of SD female rats increased continuously by months, there was no significant difference of BMC between OVX groups and SHAM groups(P>0.05), Tb.Th increased slowly in OVX groups, significantly lower than SHAM groups at two months after operation( P<0.05). Tb.Ar% ,Tb.N and BMD reached the peak at six months of adulthood, then decreased. BMD and Tb.Ar% of OVX groups were lower than those of SHAM groups respectively at one month after operation(P<0.05,P<0.01). Tb.N of OVX groups were lower than that of SHAM group at two month after operation(P<0.05). Tb.Sp decreased at growth period, inversely increased at adulthood, OVX group increased significantly than SHAM group at two month after operation(P <0.01). 2. The OVX rats were defined as OP model at one month after operation. BMD was significantly positively correlated with Tb.Ar% and Tb.Th(r=0.4453,P <0.01;r=0.3256,P <0.05), significantly negativly correlated with Tb.Sp(r=-0.2554,P<0.05), BMC had no correlation with histomorphometrical markers. 3. Serum levels of AKP and TRAP were the highest and the lowest respectively at three months, serum levels of AKP and TRAP in OVX groups were both higher than SHAM groups, which had significant difference at one month(P<0.05) and three months(P<0.05) after operation respectively. 4. The positive area density of OPG in bone trabecula and MOD increased monthly. Both the positive area density of OPG in bone trabecula and MOD decreased in OVX groups compared with those of SHAM groups at one month after operation and MOD decreased significantly (P<0.01), then both increased compensatively at two and three months after operation. The total OPG positive area of cancellous bone of normal rats increased monthly, which significantly decreased at ovariectomized rats at one, two, three months after operation(P<0.05, P<0.01, P<0.01). 5. The positive area density of OPG in bone trabecula was significantly positively related with TRAP(r=0.592,P <0.01), The total OPG positive area of cancellous bone and MOD were positively related with BMD(r=0.3532,P <0.01, r=0.298,P <0.05), and negatively correlated with AKP(r=-0.301,P <0.05, r=-0.293,P <0.05). 【Conclusion】 1. The bone mass in SD female rat reachs peak at six months and BMD and Tb.Ar% significantly decrease at one month after ovariectoming, which demonstrates that the OP model is established succe...