RESUMO
<p><b>OBJECTIVE</b>To establish a rabbit model of silicotic pulmonary fibrosis and to investigate the effect of cordyceps sinensis in this model.</p><p><b>METHODS</b>Thirty healthy male white rabbits were randomly divided into control group, silicosis model group, and intervention group. The rabbits in silicosis model group and intervention group received endotracheal perfusion of silicon dioxide suspension (120 mg/kg), and the control group was treated with the same volume of saline. All the rabbits were sacrificed 30 days later. The lung coefficient was calculated by comparing the lung weight and body weight; the right lung tissue was stained with hematoxylin-eosin (HE). The content of hydroxyproline in lung tissue was measured by alkaline hydrolysis. The mRNA levels of transforming growth factor beta 1 (TGF-β₁) and mothers against decapentaplegic homolog 7 (Smad7) in rabbit lung sections were determined by real-time PCR.</p><p><b>RESULTS</b>No abnormalities were observed by HE staining in the lung tissues of control group, while fibrosis and silicotic nodules were discovered in the silicosis model group and intervention group. The lung coefficient and the content of hydroxyproline in lung tissue were significantly higher in the silicosis model group than in the control group and intervention group (P < 0.05 or P < 0.01). Compared with the control group, the silicosis model group and intervention group had significantly increased TGF-β₁ mRNA levels but significantly reduced Smad7 mRNA levels (P < 0.02). Compared with the silicosis model group, the intervention group had a significantly reduced TGF-β₁ mRNA level but a significantly increased Smad7 mRNA level (P < 0.05).</p><p><b>CONCLUSION</b>Cordyceps sinensis is able to reduce the expression of TGF-β₁ mRNA and increase the expression of Smad7 mRNA in lung tissues of rabbits with silicotic pulmonary fibrosis, and thus postpone the progression of fibrosis.</p>