Snail-shRNA in AAV9 inhibited EMT and pulmonary fibrosis in silica-instilled mice.

Our previous study in vitro has shown that targeting transcription factor Snail might be a strategy for the treatment of silicosis. In this study, we evaluated the feasibility of the strategy in vivo. Here we used CBG transgenic mice which could be used to track and isolate alveolar epithelial type II cells (AT II cells) to confirm that 2.5 mg silica could induce epithelial-mesenchymal transition (EMT) in AT II cells in vivo. Based on the results that 2.5 mg silica induced a rapid elevation of Snail in the lungs of mice and the optimal injection dose and stable expression time of adeno-associated virus (AAV) 9 vectors, we finally decided to inject AAV9-mediated Snail knockdown at 1.0 × 1011 vg/mouse 1 week before silica instillation to inhibit the levels of Snail increased by silica. The results showed that Snail-shRNA in AAV9 prevented silica-induced EMT in AT II cells in CBG transgenic mice and inhibited EMT and pulmonary fibrosis induced by silica in wild-type mice. Quantitative proteomic analysis combined with dbEMT database mapping further indicated that Snail knockdown suppressed silica-induced EMT and fibrosis through a Fibronectin (FN1)-centered interaction network involving proMMP8 activation and JUN kinase signaling. These findings suggested that Snail could be used as a target for the treatment of pulmonary fibrosis in the future.