Although Krt8 has been highlighted as a transitional state marker in mice (51, 54) and KRT17 in human IPF (58), KRT7, KRT8, KRT17, KRT18, and KRT19 were upregulated in the transitional state in the bleomycin, LPS, pneumonectomy (PNX), and organoid mouse models of regeneration and in human IPF (Figure 1A). Here, KRT18 is linked to idiopathic pulmonary fibrosis.