Additionally, IPF fibroblasts stimulated with exogenous TGF-β1, interleukin (IL)-13 or CC-chemokine ligand 2 (CCL2) have significantly increased levels of connective tissue growth factor (CTGF), TGF-β1, and cell-surface receptors for TGF-β1, IL-13 and platelet-derived growth factor (PDGF) [11]. Here, CCN2 is linked to idiopathic pulmonary fibrosis.