Multi-omics reveals a novel Cxcr4<sup>+</sup> subpopulation of alveolar macrophages and therapeutic effect of AMD3100 in mice with advanced silicosis

<h4>Background</h4>Silicosis is a work-related condition resulting from breathing in crystalline silica particles, marked by persistent inflammation and abnormal healing mechanisms in the lungs. Our previous studies demonstrated that inhibition of Cxcr4 with Plerixafor (AMD3100) markedly attenuates pulmonary fibrosis.<h4>Methods</h4>By integrating single-cell RNA sequencing with spatial transcriptomics, we analysed lung tissues from a mouse model of pneumoconiosis. Using the Robust Cell Type Decomposition algorithm to deconvolve spatial transcriptomic data, we identified Cxcr4⁺ macrophages and Cxcl12⁺ fibroblasts as central drivers of pulmonary fibrosis progression, revealing a distinct spatial co-localisation pattern between these cell populations. To further delineate macrophage heterogeneity and functional specialisation during silicosis progression, we focused on key macrophage subpopulations.<h4>Results</h4>AMD3100 dynamically remodels the alveolar macrophages (AMs) niche, promoting the restoration of AM homeostasis and significantly reducing both co-expression and spatial co-localisation of Cxcr4/transforming growth factor-β (TGF-β) signalling within macrophages, thereby modulating the fibrotic immune microenvironment. Mechanistically, silica dust stimulation in vitro upregulates Cxcr4 expression in the AM cell line MH-S, which in turn promotes the release of TGF-β and pro-inflammatory factors, driving fibroblast activation. Activated fibroblasts further enhance the pro-fibrotic phenotype of macrophages via secretion of Cxcl12, reinforcing the Cxcr4 signalling axis and establishing a stable positive-feedback loop.<h4>Conclusion</h4>Our findings suggest that silicosis-associated fibrosis progresses through a positive feedback loop involving interactions between Cxcr4⁺ AM macrophages and Cxcl12⁺ fibroblasts. These findings highlight the therapeutic promise of targeting the Cxcl12/Cxcr4 axis with AMD3100 as an innovative approach for silicosis treatment.