COL3A1 and idiopathic pulmonary fibrosis: Because reduced Col1a1 and Col3a1 mRNA expression has been reported following prophylactic (Cedilak et al., 2019; Higashiyama et al., 2007) and interventional (Jarman et al., 2014) ALK5i treatment in BLEO‐IPF mice, it may be speculated that ALK5i suppressed de novo collagen synthesis but was unable to enhance clearance of already deposited collagen fibers.