Abstract: Pulmonary fibrosis (PF) is a disease that with high mortality, poor prognosis and unclear pathogenesis. To investigate the expression of MMP-7, KL-6, SP-A, SP-D in bleomycin-induced PF mice, to discuss the application of target-specific near-infrared fluorescent MMP-7 probe and combined detection of 4 markers in bleomycin-induced PF mice to provide the foundation of diagnosis, progress and prognosis of the disease. Forty C57BL/6 male mice were randomly divided into bleomycin group (n=30) and control group(n=10), the different concentrations (2.0,3.5,5.0 mg·kg^-1) of bleomycin were given via trachea to induce the pulmonary fibrosis model in bleomycin group, the control group were given the same dose of saline. At day 28 after administration, histopathological score was use to evaluated the severity of pulmonary fibrosis and alveolitis. The expressions of MMP-7，KL-6，SP-A，SP-D were detected by ELISA, RT-PCR, immunohistochemistry and Western blot. The mice were subjected to NIR imaging at different time after injection of MMP-7 probe to observed the distribution and targeting effect of the probes in vivo. The concentration of BLM was correlated with alveolitis pathological score (P=0.008) and fibrosis pathological score(P=0.03). The expressions of MMP-7，KL-6，SP-A，SP-D were significantly different between bleomycin group and control group(P<0.05). Near-infrared fluorescence probe can specifically target on MMP-7 with stable signal. The abnormal expressions of MMP-7，KL-6，SP-A，SP-D were correlated with PF, they may be a biomarkers of bleomycin-induced pulmonary fibrosis. The combined detection of these four markers can improve the diagnosis ability in PF and provide a strong reliability in diagnosis in clinical use. Noninvasive MMP-7 probe can be used on the PF disease of dynamic monitoring.

Key words: bleomycin, pulmonary fibrosis, mice model, biomarker, near-infrared fluorescent probe