PEI has an effect of alleviating the lung injury, which is bleomycin-induced in rats and of alleviating pulmonary fibrosis, which was associated with a reduction in the levels of connective tissue growth factor (CTGF), TGF-β, NF-κB, ERK1/2, and tumor necrosis factor ligand superfamily member 6 (FasL) in lung tissue (Guo et al., 2013). Here, CCN2 is linked to pulmonary fibrosis.