CXCL12 and idiopathic pulmonary fibrosis: Among these, pro-fibrotic mediators such as transforming growth factor beta-1 (TGF-β1), platelet-derived growth factor (PDGF), tumor necrosis factor (TNF), endothelin-1, connective tissue growth factor (CTGF), osteopontin, and CXC chemokine ligand 12 (CXCL12) [52], which are overexpressed in the AECs of IPF lungs, modulate both the progression of fibrosis and the aberrant extracellular matrix deposition [24].