miR-33M/M–/– mice were protected from bleomycin-induced lung fibrosis, as indicated by a reduction in collagen content, measured by hydroxyproline assay (fold change, –2; P ≤ 0.0001) (Figure 2B) and expression of profibrotic genes including Col1a1 and Acta2 (fold change, –2.5; P ≤ 0.0001) (Figure 2, C and D). Here, ACTA2 is linked to pulmonary fibrosis.