Single-cell transcriptomic analysis identifies a MIF-driven keratinocyte-macrophage-Th2 axis as a key inflammatory circuit in atopic dermatitis.

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory skin disorder involving complex interactions among multiple cell types. The cellular heterogeneity and intercellular communication networks driving AD pathogenesis remain to be fully elucidated.

METHODS

Single-cell RNA sequencing datasets were employed to identify cell types in lesional skin of AD patients and analyze the transcriptomic characteristics of keratinocytes, T cells, and macrophages. Cell clusters were identified based on marker gene expression, and intercellular communication networks were analyzed to investigate cell-cell interactions. The findings were validated using in vitro cell models (HaCaT, HEK, primary keratinocytes, and THP-1 cells) and an MC903-induced AD mouse model, with MIF expression assessed by qPCR and Luminex. Immunofluorescence staining was used to evaluate the distribution and aggregation of macrophages. Functional studies were conducted using MIF098 to inhibit MIF signaling.

RESULTS

scRNA-seq revealed significant cellular remodeling in AD lesions, with marked enrichment of keratinocytes, T cells, and macrophages. The proportion of Th2 cells was increased in AD lesion tissues, and an MRC1+ macrophage subset (Cluster3-Mac) was specifically enriched in AD lesions. Intercellular communication analysis demonstrated that proliferative keratinocytes may interact with Cluster3-Macrophages via the MIF-CD74/CD44 signaling axis, with proliferative keratinocytes acting as senders and macrophages as receivers. Furthermore, MRC1+ macrophages may engage with Th2 cells through PTPRC. Consistent with these findings, MIF expression was significantly upregulated in the serum of AD patients, in IL-13-treated HaCaT and HEK cells, and in the epithelial tissues of AD model mice. In the MC903-induced AD mouse model, lesional skin showed epidermal thickening, inflammatory infiltration, and accumulation of M2-polarized macrophages (F4/80+CD206+). Functional validation using MIF098 showed that inhibition of MIF downregulated its expression in primary keratinocytes and reduced the ability of THP-1 cells to secrete CCL17, CCL22, and IL-10.

CONCLUSION

Our findings identify a critical role for the MIF signaling axis in mediating crosstalk between proliferative keratinocytes and M2-polarized macrophages, thereby promoting Th2-driven inflammation in AD. Targeting MIF may represent a potential therapeutic strategy for AD.