Significance and Expression of MMP7 in Paraquat-induced Murine Pulmonary Fibrosis / 中国医科大学学报

ABSTRACT

Objective To investigate the expression of matrix metalloproteinase 7(MMP7)in paraquat(PQ)?induced pulmonary fibrosis in rats. Methods Forty?eight SD rats were randomly divided into the control group and the pulmonary fibrosis model group(PQ model group),each group of twenty?four rats. Rats in the PQ model group received single intraperitoneal injection of 4 mg/mL PQ dilute solution and the control group were in?traperitoneal injected with the same dose of saline. Eight rats of each group were sacrificed on day 7,day14 and day 28 respectively. The pathological changes of lung tissues were observed and the hydroxyproline(HYP)content in lung tissues was determined. The severity of pulmonary fibrosis was observed. The expressions of MMP7 in lungs were observed by immunohistochemistry. Results The observation of general state of the experimental animals showed that except one rat died at day 28 d,all other rats survived to the end point of observation. After intraperitoneal injection with PQ,the weight of rats in the PQ model group gradually declined,and then increased around day 14,yet still much lower than that in the control group at day 28(P<0.05). After intraperitoneal injection with PQ,the pulmonary index in the model group increased gradually and then decreased after reach?ing the peak on day 14. The content of HYP in rat lung tissues in the PQ model group was remarkably higher than in the control group at day 7,day 14,and day 28,with statistical significance(P<0.01). In the PQ model group,the content of HYP was significantly up?regulated with the extension of infected time and reached the peak value at day 28. The results of HE staining showed significant pulmonary alveolitis at day 7,hyperplasia of abundant collagen fibers in alveolar septum at day 14,and obvious pulmonary fibrosis and collapse of alveolar structure on day 28 in the lung tissues of the PQ model group. A weak expression of MMP7 was measured in the lung tissues in the control group and the expression of MMP7 was higher in the PQ model group than in the control group at day 7,day 14,and day 28,with statistical significance(P<0.05). Conclusion Paraquat poison?ing was mainly manifested in inflammatory reactions of lung tissues in the early stage together with increase of fibroblasts and mainly in fibrosis in the late stage. The expression of MMP7was increased along with the severity of pulmonary alveolitis or fibrosis and showed significant changes compared to the control group at day 28 after poisoning,indicating that MMP7may be the marker of paraquat?induced pulmonary fibrosis.