2型糖尿病大鼠骨髓腔内PPARγ和Cbf&agr;1 mRNA的表达与骨折愈合障碍的关系

目的:探讨2型糖尿病大鼠骨髓腔内过氧化物酶体增殖物激活受体γ (peroxisome proliferator-activated receptor gamma, PPARγ)和核心结合因子&agr;1(core binding factor alpha 1,Cbf&agr;1)表达的变化与2型糖尿病骨折愈合障碍之间的关系。方法:雄性SD大鼠随机分为对照组(n=15)和实验组(n=15)分别给予普通饲料、高糖高脂饲料喂养。8周后摘眼球取血,两组分别腹腔注射枸橼酸盐缓冲液和链脲佐菌素(STZ,35 mg/kg)。2周后再次摘眼球取血,并建立大鼠左胫骨牵引成骨模型,牵引14 d后处死动物,收集血液及左胫骨,无菌分离双侧股骨。X线摄片比较两组胫骨牵引间隙内骨痂的形成情况。组织学观察牵引骨痂内微骨柱(MCF)与初始基质前沿(PMF)及骨折两端髓腔内脂肪细胞的形成情况,并计算骨折两端髓腔内脂肪细胞与骨髓腔面积百分比。RT-PCR法检测两组动物股骨骨髓腔内PPARγ和Cbf&agr;1 mRNA的表达。结果:8周后实验组大鼠血清甘油三酯较对照组明显升高(P<0.01),血清总胆固醇较正常组升高(P<0.05),空腹血糖鹊核厮轿廾飨圆钜?P>0.05)。10周后实验组大鼠空腹血糖甯视腿ソ隙哉兆槊飨陨?P<0.01),血清总胆固醇较正常组升高(P<0.05),血胰岛素水平无明显差异(P>0.05),2型糖尿病大鼠模型建立。与对照组比较,2型糖尿病组大鼠X线摄片显示骨折断端之间牵引骨痂形成明显减少,骨痂组织学检查表现为MCF排列紊乱,PMF浅染；骨折两端髓腔内脂肪细胞及脂肪细胞占骨髓腔面积百分比明显增加(P<0.01)；RT-PCR法检测显示双侧股骨骨髓腔内PPARγ mRNA表达上调(P<0.05), 而Cbf&agr;1 mRNA的表达下调(P<0.05),而对照组则相反。2型糖尿病对早期骨折愈合表现为明显的抑制作用。结论:2型糖尿病大鼠骨折愈合障碍可能与2型糖尿病条件下骨髓腔内PPARγ mRNA表达增加而Cbf&agr;1 mRNA的表达受抑制有关。

Expression of PPARγ and Cbf&agr;1 mRNA in bone marrow cells in Type 2 diabetic rats and its correlation with impaired fracture healing

ObjectiveTo investigate the relationship between impaired fracture healing and the expression of peroxisome proliferator activated-receptor gamma (PPARγ) and core binding factor alpha 1 (Cbf&agr;1) mRNA in the bone marrow of Type 2 diabetic rats.MethodsThirty male Sprague-Dawley rats were divided into a control group (n=15, normal diet) and an experiment group (n=20, high fat and sucrosum diet). After 8 weeks, one eyeball was culled for blood collection. The experiment group was intraperitoneally injected with streptozotocin and the control group received citrate buffer. After another 2 weeks, the other eyeball was culled again to collect blood. The model of distraction osteogenesis in the left tibias of the rats was established. After 14 days, we sacrificed all the rats and collected the blood and left tibias. Both femurs were harvested with germ free. We observed the callus formation in the distraction gap by X-ray and the formation of primary matrix front and microcolumn by histological examination. We observed adipocytes in adjacent bone marrow of left tibia and computed the percentage of adipocytes accounting for the area of bone cavity. We measured the expression of PPARγ and Cbf&agr;1 mRNA in femurs marrow by RT-PCR.ResultsIn the experimental rats, the level of triglyceride was obviously elevated (P<0.01), so was the total cholesterol (P<0.05), while the level of fasting blood glucose and serum insulin did not obviously differ (P>0.05) after 8 weeks. The level of fasting blood glucose and triglyceride was obviously elevated (P<0.01), and so was the total cholesterol (P<0.05), while the level of serum insulin was not obviously different in the experiment group after 10 and 12 weeks. Callus formation in the distraction gap was obviously diminished by X-ray in the experimental rats. The array of microcolumn formation was disordered and the area of primary matrix front was catachromasis in the controls by histology examination. The number of adipocytes in both the bone marrow and the percentage of adipocyte accounting for the area of bone cavity increased (P<0.01) in the experiment group. In the experiment group, the expression of PPARγ mRNA was up-regulated (P<0.05) while Cbf&agr;1 mRNA was down-regulated (P<0.05) in double femur marrow. ConclusionIncreased expression of PPARγ mRNA and decreased expression of Cbf&agr;1 mRNA in the bone marrow may cause impaired fracture healing in rats with Type 2 diabetes.