中文摘要：

目的观察ApoE基因敲除（ApoE-／-）小鼠骨量的变化，并探讨其骨量变化的可能机制。方法28周龄雄性ApoE-／-鼠6只和野生型C57BL／6J（WT）鼠10只，颈脱臼法处死动物，应用显微CT测定小鼠右侧股骨远端松质骨和皮质骨的骨微结构参数，采用双能X线吸收仪测定左侧股骨骨密度。应用ELISA方法测定血清中的护骨素（OPG）和核因子KB受体活化因子配基（RANKL）的水平。分离鼠左侧胫骨，脱钙后置4％多聚甲醛固定，用免疫组织化学染色SP法检测胫骨中OPG和RANKL的表达情况。结果28周龄ApoE-／-鼠股骨松质骨体积骨密度（294±38）mg／mm^3、组织骨密度（627±23）mg／mm^3、骨矿含量（0．57±0．08）mg、骨体积分数（20．38±4．74）％、骨小梁数量（6．67±0．78）mm^-1、骨小梁厚度（0．03±0．01）mm明显高于WT鼠，而骨面积分数（69-±18）mm^-1、骨小梁间隔（0．12±0．01）和结构模型指数（1．73±0．24）明显减低。DXA测定显示ApoE-／-鼠的总体骨密度[（0．063±0．004）g／cm^2]，比WT鼠[（0．056±0．004）g／cm^2，P=0．01]增加了12．6％。ELISA结果显示ApoE-／-鼠OPG水平[（4．98±0．97）ng／ml]明显高于WT鼠[（3．54±0．65）ng／ml]，而RANKL水平在两组鼠中无显著变化[（575±83）pg／ml比（591±87）pg／ml，P〉0．05]，差异无统计学意义。但OPG表达水平明显增高。结论OPG／RANKL比率失衡使得骨动态平衡被打破，骨吸收功能减弱可能是造成ApoE-／-鼠骨量增加的机制之一。

英文摘要：

Objective To study bone mass changes and its mechanisms in murine knockout apolipoprotein E （ApoE -/- ）. Methods Both 28-week-old male ApoE -/- mice （n = 6） and wild-type （WT） mice （n = 10） were euthanized. The trabecular and cortical bone microarchitecture were assessed by micro-CT （μCT） in right distal femur. The total body BMD （bone mineral density） of left femur was determined by dual-energy X-ray absorptiometry （DXA）. The serum concentrations of osteoprotegerin （OPG） and receptor activator of nuclear factor κB ligand （RANKL） were analyzed using enzyme-linked immunosorbent assay （ELISA）. The left tibias were dissected and fixed in 4% paraformaldebyde after decalcified in 0. 15M EDTA buffer for 30 days. And the expressions of OPG and RANKL were detected by immunohistochemical staining. Results Compared with WT mice, the ApoE -/- mice showed an increased volumetric BMD （ 294 ± 38 ） mg/mm3, tissue BMD （ 627 ± 23 ） mg/mm3, BMC （ bone mineral content） （0. 57 ± 0. 08 ） rag, bone volume fraction （ 20. 38 ± 4. 74 ） %, trabecular number （ 6. 67 ± 0. 78 ） mm^-1, trabecular thickness（0. 03 ± 0. 01 ） mm with an decreased bone surface fraction （69 ± 18） mm-1 , trabecular separation（0. 12 ± 0.01 ）and structure mode index（ 1.73 ± 0. 24）. The total body BMD was higher in ApoE - / - mice than WT mice [ （0. 063 ± 0. 004 ） g/cm2 vs （0. 056 ± 0. 004 ） g/cm2 ]. The serum level of OPG was significantly higher in ApoE - / - mice than WT mice [ （4. 98 ± 0. 97 ） ng/ml vs （3. 54 ±0. 65）ng/ml]. The results of immunohistochemical staining showed that the OPG expression was at a higher level in bone cell of ApoE - / - mice and RANKL showed no obvious change in either sera or bone cells. Conclusion A decreased bone resorption causes an increased bone mass in ApoE -/- mice and leads to an imbalanced ratio of OPG/RANKL