COL1A1 and idiopathic pulmonary fibrosis: Interestingly, the SCGB3A2+ alveolar cells highly expressed collagen (COL1A1) and fibronectin (FN1) genes (Fig 5A and 5B), suggesting that, in addition to myofibroblasts, the SCGB3A2+ hyperplastic alveolar cells also contributed to the extracellular matrix deposition in IPF.