Fig. 3. Supernatants from silica-treated macrophages promoted changes in ECM components in a dose-dependent manner in MRC-5 cells. MRC-5 cells were cultured in DMEM (NC) or the supernatants collected from Raw264.7 cells exposed to 0, 12.5, 25, 50 or 100 μg mL^–1 silica solution for 24 h. (a) Immunofluorescence staining of collagen1 (green) in silica 0 and silica 50 μg mL^–1 groups. Collagen1, mainly expressed in cytoplasm, was significantly increased following induction by supernatants from silica-treated macrophages. (b, c) qRT-PCR analyses of mRNA expression levels of collagen1 and collagen3, respectively. mRNA levels were up-regulated in a silica dose-dependent manner. The significant changes emerged in the silica 50 μg mL^–1 group. (d, e, f) Western blotting analyses of the protein expression levels of collagen1 and collagen3. Protein levels were increased in a silica dose-dependent manner as well. The data are presented as the means ± SD. *p < 0.05 versus the NC group, **p < 0.01 versus the NC group, ^p < 0.05 versus the silica 0 group, ^^p < 0.01 versus the silica 0 group.