Fibroblasts derived from IPF lungs have distinct biological characteristics: a high percentage of apoptotic cells, and increased collagen, fibronectin, gelatinase B, TIMPs, β-FGF, and PDGF expression (i.e., a pro-fibrotic secretory phenotype) [42], and a reduced capacity to secrete anti-fibrotic molecules, such as prostaglandin E2 and hepatocyte growth factor [9]. Here, MMP9 is linked to idiopathic pulmonary fibrosis.