Gremlin-1 (GREM1) is a member of the cystine knot superfamily and a bone morphogenetic protein (BMP) antagonist.5,6 GREM1 plays a critical role in embryogenesis, organ development and tissue differentiation through regulation of BMPs.7,8 In addition, GREM1 has been involved in diverse pathological conditions, such as renal9,10 or pulmonary fibrosis,11,12 renal inflammation13,14 and diabetic kidney disease15,16 in BMP-dependent or -independent manners. This evidence concerns the gene GREM1 and pulmonary fibrosis.