Dynamic expression of pulmonary YKL-40 protein in rats with bleomycin-induced pulmonary fibrosis / 第二军医大学学报

ABSTRACT

Objective To observe the expression of YKL-40 protein in the pulmonary tissues of rats with bleomycin-induced pulmonary fibrosis (PF). Methods The PF model group was induced with intratracheal instillation of bleomycin solution (7. 5 mg/kg) and the control group was treated with normal saline. On day 7, 14, 21 after bleomycin challenge, rats were sacrificed and the pulmonary tissues were harvested. H-E staining, Masson staining and Szapiel score were employed to determine alveolitis and pulmonary fibrosis. Expressions of YKL-40 in lung tissues were detected by real-time RT-PCR, Western blotting analysis and immunohistochemistry method. Results Bleomycin instillation induced alveolitis in the lung of rats, with inflammation score being significantly higher on day 7 (2. 8 ± 0. 45, P<0. 01) and on day 21 (1. 8 ± 0. 84, P<0. 05) compared with that of control group (0. 42± 0. 25). Pulmonary fibrosis degrees in model group was significantly higher on day 14 (1.7 ± 0.73, P<0.05) and on day 21 (2.9± 0.56, P<0. 01) compared with that of control group (0.2 ± 0.45). YKL-40 mRNA (YKL-40/p-actin) expression was significantly increased on day 7 (3. 71 ± 0. 25) after bleomycin treatment compared with the control group (P<0. 05). Western blotting analysis showed that YKL-40 protein expression was significantly increased on day 14(0. 56 ±+ 0. 24,P<0. 05) and on day 21(1. 15 ± 0. 19, P<0. 01) after bleomycin treatment compared with the control group (0. 23 ± 0. 07). The results of immunohistochemistry showed that bleomycin up-regulated YKL-40 expression in a time-dependent manner, and YKL-40 expression was mainly located in the smooth muscle cells, alveolar macrophages, alveolar epithelium and fibroblasts. Conclusion YKL-40 expression may contribute to the pulmonary fibrosis, and may participate in the pathogenesis of pulmonary fibrosis.