FOXJ1 and idiopathic pulmonary fibrosis: Since iron accumulation in IPF lung tissue has been implicated in pathological progression [20] and is partly controlled by FTL [13], healthy and IPF tissue sections were stained for FTL together with FOXJ1 in order to verify our single-cell RNA analysis at the protein level, since FTL is known to be post-transcriptionally regulated [21].