抑制Wnt／β-catenin愈合的影响信号通路对骨折

Effect of Wnt/β-catenin signals on the fracture healing in transgenic mice

目的探讨Wnt／β-catenin信号通路在骨折愈合中所起的作用。方法采用8周龄Col2al—ICAT转基因小鼠为实验组（转基因在软骨细胞中特异性表达后可竞争性阻断β—eatenin信号）和同窝出生WT小鼠（对照组）作为实验动物，分别制备右下肢胫骨中段截断骨折模型。于骨折后7、9、14、21、28d取材进行分析，通过X线片、组织学观察和组织形态计量学分析，比较两组软骨痂和骨性骨痂在骨折愈合不同时期所占的比例。结果通过X线片观察发现，骨折后第21天，WT小鼠骨折线已消失，而Col2a1-ICAT转基因小鼠骨折线仍可见。组织学观察发现，与WT小鼠相比，Col2al—ICAT转基因小鼠软骨痂出现延迟，软骨内骨化受阻，骨折的塑形改造延迟。组织形态计量学结果显示：Col2al—ICAT转基因小鼠软骨痂较晚出现高峰期，骨折后第14和第21天时骨性骨痂占总骨痂的比例明显低于WT小鼠，差异有统计学意义（P〈0．05）。结论抑制Wnt／β—catenin信号通路将抑制骨折愈合的软骨内骨化过程，最终导致骨折愈合延迟。

Objective To evaluate the effect of Wnt/β-catenin signals on the fracture healing in transgenie mice. Methods Col2al-ICAT transgenic mice were generated by the gene targeting technology with the ICAT transgene specifically expressed in chondrocytes as a competitive inhibitor to block Wnt/β-catenin signals. The 8-week-old Col2al-ICAT mice were used in the experimental group and the wild type （WT） littermates with the same age served as the control group, A transverse osteotomy was performed at the middle of the tibia and the fracture healing was evaluated on the 7th, 9th, 14th, 21th and 28th days respectively after fracture. Roentgenography and histology observations were performed to evaluate the fracture healing pattern and the histomorphometric analysis was used to quantitate the cartilage callus volume / total callus volume （CV/TV） or bony callus volume / total callus volume （BV/TV）. Results X-ray examination revealed that on the 21st day after fracture, callus appeared at the fracture gap to form a bony bridge in WT mice while a radiolucent zone was apparent in the fracture gap in the Col2al-ICAT transgenic mice. Histology observation revealed that compared with WT mice, the formation of cartilage callus and endochondral ossification were delayed in Col2al-ICAT transgenic mice, Histomorphometric analysis indicated that the peak value of CV/TV arrived later in CoI2al-ICAT transgenic mice than in WT mice. The BV/TV in Col2al-ICAT transgenic mice was significantly less than that in WT mice on 14th and 21st days after fracture （P 〈0. 05）. Conclusion The Wnt/β-catenin signals cause delayed fracture healing in Col2al-ICAT transgenic mice by affecting the cartilage callus formation and eudochondral ossification.