Human epididymis protein 4-annexin II binding promotes aberrant epithelial-fibroblast crosstalk in pulmonary fibrosis.

Invasive lung myofibroblasts are the main cause of tissue remodeling in idiopathic pulmonary fibrosis (IPF). A key mechanism contributing to this important feature is aberrant crosstalk between the abnormal/injured lung epithelium and pulmonary fibroblasts. Here, we demonstrate that lungs from patients with IPF and from mice with bleomycin (BLM)-induced pulmonary fibrosis (PF) are characterized by the induction of human epididymis protein 4 (HE4) overexpression in epithelial cells. HE4 knockdown primarily in epithelial cells attenuates BLM-induced PF in mice, whereas the administration of recombinant mouse HE4 exacerbates fibrosis after BLM stimulation. Mechanistic analysis shows that HE4 and annexin II (ANXA2) specific binding enhances the profibrotic phenotype in epithelial cells, and directly promotes lung fibroblast activation, leading to aberrant epithelial-fibroblast crosstalk and the persistent myofibroblast phenotype. The HE4 and ANXA2 binding site is located after the 30th amino acid at the N terminus of the HE4 molecule. Finally, intratracheal administration of HE4 shRNA lentivirus protects mice against BLM-induced PF. These data suggest that HE4 can serve as a potential therapeutic target in the treatment of IPF.