Interestingly, incubation with M2 macrophages dramatically promoted myofibroblast differentiation of LR-MSCs evidenced by the expression of α-SMA (Fig. 3c and d), suggesting that M2 macrophages, rather than M1 macrophages, are able to promote myofibroblast differentiation of LR-MSCs in the pathogenesis of pulmonary fibrosis. This evidence concerns the gene ACTA1 and pulmonary fibrosis.