MMP-12异常表达对放射性肺损伤大鼠肺内成纤维细胞转化的影响

Effects of matrix metalloproteinase-12 abnormal expression on the transformation of pulmonary fibroblasts in radiation damaged rats

目的观察放射性肺损伤过程中基质金属蛋白酶12(MMP-12)过表达对肺成纤维细胞转化的作用。方法32只雄性Wistar大鼠,体重250～280g,随机分为正常对照组(n=8)和照射组(n=24)。照射组用20Gy60Coγ射线进行全胸照射,分别于照射后1、2、4周行肺组织取材,每时间点8只。应用明胶酶谱法检测MMP-12酶活性变化,组织特殊染色法观察肺泡壁弹力纤维降解情况,透射电镜观察肺泡Ⅱ型上皮细胞与肺间质细胞间的"信号交流"(cross talking)现象,ELISA法检测肺组织中TGF-β1含量,免疫组化检测肺组织α-平滑肌肌动蛋白(α-SMA)表达情况。结果MMP-12酶活性在照射后1周开始增高,至照射后4周时有所下降;肺泡壁基底膜弹力纤维照射后1周开始出现降解断裂,4周时最为严重;肺组织TGF-β1含量和α-SMA免疫组化阳性信号在1～4周内随照后时间延长而逐渐升高。电镜观察肺泡Ⅱ型上皮细胞与肺间质细胞间出现"信号交流"现象。结论照射后肺组织MMP-12酶活性增高,可能通过降解基底膜弹力纤维促进成纤维细胞转化,启动肺纤维化的发生。

Objective To observe the effects of over-expression of matrix metalloproteinase-12 （MMP-12） on the transformation of pulmonary fibmblasts in radiation damaged rats. Methods Thirty two male Wistar rats （weighed 250--280g） were randomly assigned into control group and 1, 2 and 4 weeks after irradiation groups （8 each）. The whole lungs of rats in irradiation groups were irradiated by ^60Co y-ray at a dose of 20Gy, and the lung specimens were harvested 1, 2 and 4 weeks after radiation. The change of MMP-12 activity was detected by gelatin zymography, the degradation and collapse of elastic fibers were observed by tissue specific staining, the ＂cross talking＂ phenomenon between alveolar type Ⅱ cells and mesenchymal cells was observed by transmission electron microscopy, the content of TGF-β1 was determined by ELISA, and the expression of α-smooth muscle actin （α-SMA） was examined by immunohistochemistry. Results MMP12 activity began increasing 1 week after irradiation, and seemed to decrease 4 weeks after irradiation. Elastin, a part of the basement membrane of alveolar wall, began to degrade and collapse 1 week after radiation, and became worse 4 weeks after irradiation. The expressions of beth TGF -β1 and α-SMA were elevated gradually within 4 weeks after radiation. The ＂cross talking＂ phenomenon was found by electron microscopy between alveolar type Ⅱ cells and mesenchymal cells. Conclusions Increased activity of pulmonary MMP-12 has been found after radiation, which may promote the transformation of pulmonary fibroblasts by degrading elasfln and ultimately inflate the pulmonary fibrosis.