To further understand more about how TRIB3 could be involved in the development of pulmonary fibrosis in vitro, we overexpressed TRIB3 in MRC5 cells for 48 h and demonstrated that TRIB3 significantly decreased the profibrotic genes expression, including ACTA2, COL1A1, and FN1 at the mRNA level and the protein level of collagen I, fibronectin, and α-SMA in MRC5 cells (Figure 4A,B). This evidence concerns the gene ACTA1 and pulmonary fibrosis.