阿仑膦酸钠对长期应用皮质激素大鼠股骨头骨组织OPG/RANKL mRNA表达的影响

Effects of alendronate on expression levels of OPG and RANKL mRNAs in bone tissues of femoral head of rats receiving long-term glucocorticoid administration

目的观察阿仑膦酸钠对长期应用皮质激素大鼠骨组织中骨保护素(osteoprotegerin,OPG)/核因子κB受体活化因子配基(RANKL)mRNA表达的影响,探讨其预防激素性股骨头坏死的效果及作用机制。方法健康SD大鼠30只,雌雄各半,随机分为激素组、阿仑膦酸钠组和空白对照组,每组10只。激素组和阿仑膦酸钠组给予肌肉注射醋酸泼尼松龙12.5mg/kg体重,每周2次,阿仑膦酸钠组同时给予阿仑膦酸钠5mg/kg体重灌胃,1次/周;对照组只给予相同体积生理盐水肌注。4周后取左侧股骨头骨组织,石蜡包埋,HE染色,鉴定骨质疏松和股骨头坏死情况;取右侧股骨头骨组织提取总RNA,采用实时定量聚合酶链反应(RTQ-PCR)技术检测OPG mRNA和RANKL mRNA的表达水平,计算OPG/RANKL比值。结果激素组、阿仑膦酸钠组及对照组的动物死亡率分别为10%(1/10)、10%(1/10)、0(0/10);股骨头坏死率分别为66.67%(6/9)、22.22(2/9)、0(0/10);股骨头骨组织OPG mRNA的相对表达量分别为0.96±0.16、1.35±0.26和1.60±0.49,RANKL mRNA的相对表达量分别为3.33±1.04、1.98±0.51和1.58±0.42,激素组与对照组比较,其OPG mRNA的表达水平降低,RANKL mRNA表达升高,OPG/RANKL比值下降,差异有统计学意义(P<0.05);阿仑膦酸钠组与对照组比较,差异无统计学意义。结论①糖皮质激素醋酸泼尼松龙能下调大鼠骨组织OPG mRNA的表达水平,上调RANKL mRNA水平,使OPG/RANKL比值下降;②阿仑膦酸钠预防激素性股骨头坏死可能与其拮抗皮质激素对OPG mRNA和RANKL mRNA表达的调控有关。

Objective To investigate the effects of alendronate on expression levels of osteoprotegerin （OPG） and receptor activator of nuclear factor kappa B ligand （RANKL） mRNAs in bone tissues of femoral head of rats receiving long-term glucocorticoid administration, and to explore the effect and mechanism of alendronate in preventing glucocorticoid-induced femoral head necrosis. Methods Totally 30 healthy adult SD rats were randomly divided into 3 groups： glucocorticoid group, alendronate group and blank control group. The glucecorticoid group and alendronate group were treated by intramuscular injection of prednisolone, 12.5 mg/kg, two times per week, and rats in the alendronate group were intragastrically administered with alendronate, 5 mg/kg weight at the same time, one time per week. The control group was treated only by the same volume of intramuscularly injected sodium chloride. After 4 weeks＇ intervention, osteoporosis and osteonecrosis of left femoral head were detected by HE staining, the total RNA of right femoral head bone tissue was extracted and the expression levels of OPG and RANKL mRNAs were examined by real-time quantitative polymerase chain reaction （RTQ-PCR）. Results The mortality of rats was 10% （1/10）, 10% （1/10） and 0 （0/10） in glucocorticoid,alendronate and control groups. The osteoporosis and necrosis rates of femoral bone head were 66.67% （6/9）, 22.22% （2/9） and 0 （0/10） in the three groups, respectively. The level of OPG mRNA expression was 0.96 ± 0.16, 1.35 ±0.26 and 1.60 ±0.49 in glucocorticoid, alendronate and control groups, while the expression of RANKL mRNA was 3.33 ± 1.04, 1.98 ±0.51 and 1.58± 0.42. The level of OPG mRNA expression was lower in the glucocorticoid group than in the control group; the level of RANKL mRNA expression was increased in the glucocorticoid group, whose OPG/RANKL ratio decreased significantly （P 〈 0.05）. The alendronate and control groups did not differ significantly. Conlusion O Glucocorticoid significantly down-regulated the level of OPG mRNA expression and up-regulated RANKL mRNA expression, thus lowering OPG/RANKL ratio. ② Alendronate prevents glucocorticoid-induced osteonecrosis of femoral head, which may be correlated to alendronate＇s counteracting with glucocorticiod in the regulation of expressions of OPG and RANKL mRNA.