Epithelial cells, alveolar macrophages, immune cells, and fibroblasts contribute to the development of tissue fibrosis by producing various mediators, such as CTGF [28], TGF-β [5,6], and PDGF [29], and endothelial cells also produce such agents and participate in the pathogenesis of fibrosis. This evidence concerns the gene CCN2 and fibrosis.