骨骺损伤修复过程中骺板形态及VEGF表达的变化

Morphosis of the epiphyseal plate and expression of vascular endothelial growth factor during healing of injured epiphyses

目的探讨大鼠骨骺损伤修复过程中骺板形态结构及骺板内血管内皮细胞生长因子（vascular endothelial growth factor，VEGF）表达的变化。方法取4-5周龄SD大鼠30只，制作胫骨近端骨骺损伤动物模型。随机分为五组，每组6只，分别于术后2、4、6、10、21天处死，取双侧胫骨。测量双侧胫骨长度，计算实验侧长度和对照侧长度比值。行双侧胫骨X线摄片、Micro CT扫描，观察骺板大体形态及骺板内骨桥形成情况。通过组织切片HE染色及免疫组织化学染色，观察骺板内软骨细胞变化及VEGF表达。结果双侧肢体长度于术后第4天出现差异，第10天差异最大，第21天肢体长度差异缩小。术后第6天开始骺板内逐渐出现纤细骨质，终至骨桥形成。HE染色提示伤后早期出现静止区软骨细胞聚集成团，细胞规律性排列丧失、分化加速。免疫组织化学染色显示术后生长板内出现VEGF高反应区，阳性表达区逐渐扩大，跨越骺板全层，直后血管长入、骨化。结论骨骺损伤修复过程中，骺板形态早中期表现为干骺端肥大，肢体短缩，骺板内纤细骨质形成；随修复进展，骺板内VEGF表达反应性增强，出现贯通骺板的表达带，与骨桥形成相关。

Objective To investigate morphosis of the epiphyseal plate and the expression of vascular endothelial growth factor （VEGF） in the epiphyseal plate during healing of injured epiphysis. Methods Thirty SD rats aged 4-5 weeks were used to make models of proximal tibia epiphysis injury. These models were equally divided into 5 groups in random, with 6 rats in each group, and these groups of rats were killed separately at 2, 4, 6, 10, 21 days postoperatively to harvest the proximal tibia epiphysis, in order to explore the morphosis of the epiphyseal plate and VEGF expression pattem in the epiphyseal plate at different healing phase. The structure of the epiphyseal plate was evaluated by measuring the length of the limb and radiographic examination of the limb. The ratio of length of injured tibia and that of the other side was used to describe the tibia length discrepancy. The micro structure of the epiphyseal plate and situation of the bone bridge in the epiphyseal plate were measured by using Micro CT. By using HE stain and VEGF immunohistochemistry, the changing of ehondrocyte and VEGF expression pattern in the epiphyseal plate were observed at different healing phase. Results The limb discrepancy appeared at 4 days postoperatively, became biggest at 10 days postoperatively, and tended to decrease at 21 days postoperatively. Micro CT demonstrated the fibrous bone tissue formation in the epiphyseal plate at about 6 days postoperatively, which became bone bridge finally. HE stain showed chondroeyte in the rest zone had the tendency to aggregate after injury, and the highly ordered structure of chondrocyte in the epiphyseal plate no longer existed, chondrocyte differentiation was accelerated. VEGF immunohistochemistry stain showed the high reaction of VEGF in the epiphyseal plate appeared after surgery, and the positive zone of VEGF expanded through the physis with time, which finally led to angiogenesis and ossification. Conclusion A serial alteration of morphosis of the epiphyseal plate occurred during the healing process. Fibrous bone tissue formation in the epiphyseal plate could be observed in the early and mid-term of the healing process. With progress of healing, VEGF expression zone gradually expanded across the epiphyseal plate, which is related to the formation of bone bridge.