SPP1-mediated crosstalk between macrophage and fibroblasts promotes benign airway stenosis

Objective: The aim of this study is to elucidate the role of M2 macrophages in the pathogenesis of benign airway stenosis using a Sprague Dawley (SD) rat model and in vitro macrophage-fibroblast co-culture systems.

Methods: Ligand-receptor interactions mediating cellular crosstalk between macrophages and fibroblasts were identified through single-cell RNA sequencing-based bioinformatics analysis. An airway stenosis model was established in SD rats, which were assigned to five experimental groups: normal control and post-modeling days 1 (D1), 4 (D4), 7 (D7), and 14 (D14). Temporal changes in M2 macrophage infiltration and their involvement in airway remodeling were assessed. Fibroblasts isolated from human granulation tissue and normal airway tissue were evaluated for differential activation of intracellular signaling pathways. In vitro macrophage-fibroblast co-culture systems involving M2 macrophages and fibroblasts were conducted to assess molecular signaling interactions.

Results: A progressive increase in M2 macrophage infiltration was observed during the development of airway stenosis, accompanied by upregulation of secreted phosphoprotein-1 (SPP1) and activation of the phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling pathway. Fibroblasts derived from granulation tissue exhibited higher levels of pathway activation compared to normal fibroblasts.In co-culture, M2 macrophages induced fibroblast activation and fibrogenesis via SPP1-mediated signaling. Administration of rapamycin, an mTOR pathway inhibitor, significantly reduced granulation tissue formation and improved airway patency in the rat model.

Conclusion: M2 macrophages contribute to fibrotic airway remodeling in benign airway stenosis through SPP1-mediated activation of the PI3K/Akt/mTOR signaling pathway in fibroblasts. Pharmacological targeting of this axis with rapamycin may represent a potential therapeutic strategy for mitigating fibrosis in benign airway stenosis.

Benign airway stenosis; M2 macrophages; PI3K/AKT/mTOR; Rapamycin; SPP1.