CREG1 and idiopathic pulmonary fibrosis: In our study, the following 18 genes were included in the extracellular region: PF4V1, NID1, PTHLH, CREG1, TFPI, FBN2, RSPO3, TSKU, EPDR1, BMP2, CCL26, POSTN, MYOC, CCL8, C1QTNF9B, CLEC18C, FGF7, and TUBA4A. Among them, FGF7 [36], POSTN [37], TSKU [38], and TFPI [39] have been suggested to be involved in the pathogenesis of IPF.