S100A4 and pulmonary fibrosis: A high tidal volume increased lung fibrosis, as found by qualitative detection of peribronchiolar and parenchymal fibrosis via Masson's trichrome stain and fibrosis scoring, quantitative measurement of the collagen level via hydroxyproline assay, and FSP1 staining for fibroblasts via immunohistochemistry (Figures 1b, 2, and 4).