When exposed to bleomycin, a well-characterized model of lung injury and fibrosis, wild-type rodents develop pulmonary fibrosis (Figure 7), but fibronectin EDA knockouts are protected [107], representing one of the first studies directly testing the role of an ECM component in lung fibrosis in vivo and suggesting that the excess production of fibronectin EDA may drive disrepair. This evidence concerns the gene FN1 and pulmonary fibrosis.