A study by Zhang et al. found that, in the bleomycin-induced pulmonary fibrosis mouse model, the expression level of circHIPK3 was upregulated in lung fibroblast-derived myofibroblasts.circHIPK3 participated in regulating the differentiation of fibroblasts into myofibroblasts and the proliferation of fibroblasts through the circHIPK3-miR338-3p/SOX4/COL1A1 pathway (28). This evidence concerns the gene COL1A1 and pulmonary fibrosis.