骨形态发生蛋白Ⅱ型在修复兔髋臼软骨发育不良过程中的表达

Expression of BMP-2 in repairing dysplasia of acetabular cartilage of rabbits

目的建立带缝匠肌的髂骨骨骺瓣治疗髋关节发育不良的动物模型,探讨骨形态发生蛋白Ⅱ型(bone morphogenetic proteins-2,BMP-2)及其mRNA在修复过程中的表达及意义。方法制备48只日本大耳白兔左侧髋关节发育不良模型,实验组通过带缝匠肌的髂骨骨骺瓣进行修复治疗,对照组不治疗。分别于术后第1、2、4、8周观察实验组和对照组家兔大体步态和髋关节活动度,并处死动物取髋臼和骨瓣组织进行HE染色,Western blot和实时定量PCR分别检测BMP-2蛋白及其mRNA的表达水平。结果对照组家兔髋关节活动恢复较慢,8周后仍为跛行步态;实验组家兔于术后8周内活动逐渐恢复,8周时步态基本正常。对照组术后1周可见髋臼软骨下骨质缺损,软骨细胞形态基本正常,术后2周髋臼软骨层薄厚不均,术后4周髋臼软骨细胞存在聚集或坏死,术后8周髋臼软骨层仍薄厚不均,但软骨细胞未见明显坏死现象;实验组术后1周可见缝匠肌骨瓣骨骺与髋臼骨组织间存在明显间隙,两者软骨层间距较大,术后2周骨瓣软骨与髋臼软骨间距逐渐缩短,术后4周骨瓣软骨与髋臼软骨间距消失,两者趋于融合,术后8周骨瓣软骨与髋臼软骨融合,两组髋臼组织中BMP-2蛋白的表达与其基因水平一致,对照组表达水平较低且无明显变化,实验组BMP-2蛋白及其m RNA的表达随时间逐渐升高,从术后2周开始高于对照组(P<0.05),术后4周时达到峰值(P<0.01)。结论实验组家兔髂骨骨骺软骨与髋臼软骨融合,髂骨骨骺瓣促进了髋臼中BMP-2的表达,BMP-2蛋白及基因表达的增加参与了修复髋臼软骨发育不良的过程。

Objective To establish developmental dysplasia of the hip（DDH） animal model treated by sartorius iliac flap with epiphysis, explore the expression and significance of bone morphogenetic proteins-2（BMP-2） and its m RNA during repair process. Methods A unilateral acetabular bone defect animal model was established with 48 Japanese white rabbits, and then the rabbits were divided into two groups. Rabbits in experimental group were treated by sartorius epiphyseal iliac flap, and rabbits in control group did not receive any related therapy. The general gait and hip motion were observed at 1, 2, 4 and 8 weeks after operation. Then they were sacrificed and their acetabular bone and cartilage tissues were taken for HE staining. The expression of BMP-2 and its m RNA were measured by Western Blot and Real-Time PCR, respectively. Results The hip motion of rabbits in control group recovered slowly, and they were still limping at 8 weeks after operation. Meanwhile, rabbits in experimental group recovered gradually and walked nearly normally at 8 weeks after operation. In control group, bone defects were found under acetabular cartilage. The morphology of cartilage cell was normal at 1 week after operation. At 2 weeks after operation, the acetabular cartilage layer showed uneven thickness and it lasted to 8 weeks after operation. Acetabular cartilage cells showed signs of degeneration or necrosis at 4 weeks postoperatively. In experimental group, it showed an obvious gap between flap cartilage and acetabular cartilage at 1 week after surgery. The distance between these two cartilages became shorter at 2, 4 weeks after surgery. At 8 weeks after surgery, the flap cartilage and acetabular cartilage almost fused together. The expression levels of BMP-2 and BMP-2 gene were consistent in acetabulum. In control group, it showed a low expression of BMP-2 and no significant changes over time. In experimental group, the expression of BMP-2 increased gradually over time. The BMP-2 expression was significantly higher when compared with control group since 2 weeks after surgery and it reached the peak at 4 weeks postoperatively. Conclusion The iliac flap cartilage and acetabular cartilage has fused together in the rabbits of experimental group. The epiphyseal iliac flap increases the expression of BMP-2 in acetabulum and the increasing expression of BMP-2 may participate in the physiological process of repairing dysplasia of acetabular cartilage.