IGFBP7: A novel biomarker involved in a positive feedback loop with TGF-β1 in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease characterized by irreversible scarring of the lungs, predominantly affecting older adults. The limited therapeutic options available are largely due to an insufficient understanding of IPF etiology and pathogenesis. This study investigated potential biomarkers to enhance IPF diagnosis and treatment strategies. Through single-cell RNA sequencing (scRNA-seq) and bulk RNA sequencing analyses of public datasets, four hub genes-FTH1, FABP5, DCXR, and IGFBP7-were identified as strongly associated with IPF. Subsequent validation in in vivo and in vitro models confirmed IGFBP7 as a novel biomarker. Double immunofluorescence staining and scRNA-seq analysis revealed that IGFBP7 expression is elevated in IPF epithelial cells. IGFBP7 shows potential for early diagnosis of IPF and can differentiate IPF from other diseases. Gene set enrichment analysis revealed the involvement of IGFBP7 in IPF pathogenesis, particularly through its strong connection to the TGF-β signaling pathway, which drives inflammation and fibrosis. In vitro studies with the TGF-β inhibitor SB431542 showed that inhibition of the TGF-β pathway significantly reduced IGFBP7 expression. Furthermore, IGFBP7 knockdown decreased the expression of markers associated with epithelial-mesenchymal transition and fibrosis while suppressing TGF-β1 expression. These results suggest that IGFBP7 forms a positive feedback loop with TGF-β1. In conclusion, this research identified IGFBP7 as a promising biomarker with significant diagnostic and therapeutic potential for IPF. These insights pave the way for improved diagnostics and the development of targeted antifibrosis therapies, while deepening our understanding of IPF mechanisms.