CCL20+ macrophage in aortic wall drives vascular smooth muscle cell phenotypic switching via IL-17/SPP1 signalling leading to aortic dissection

Background Prominent macrophage infiltration in dissected aortic tissue observed in previous studies indicated a causal relationship between macrophage infiltration and aortic dissection. However, the underlying mechanism remains unclear. The present study aims to investigate the intermediate steps from macrophage infiltration to aortic dissection by using single-cell sequencing, biomolecular analysis and an animal model of aortic dissection, and to define a therapeutic target for blocking pathogenesis of aortic dissection. Methods Single-cell RNA sequencing was performed on ascending aortic tissues from patients with Type A Aortic Dissection (TAAD, n=8) and controls (organ donors, n=6), totally 145,704 cells. Trajectory and cell–cell communication analyses were conducted to define macrophage heterogeneity and intercellular crosstalk. Immunofluorescence validated spatial localization in human tissues. In vitro, THP-1–derived macrophages with CCL20 overexpression were co-cultured with VSMCs. IL-17 signalling activation, SPP1 expression, and VSMC phenotypic markers were assessed by qPCR, Western blotting and Elisa. Dual-luciferase reporter assays were used to determine NF-κB (p65)–mediated transcriptional regulation of SPP1. In vivo, a mouse model of aortic dissection was induced by β-aminopropionitrile (BAPN), with (n=20) and without (n=20) treatment of shCCL20 under incubation to evaluate therapeutic effects. Results A distinct CCL20+ macrophage subset was markedly expanded in TAAD and positioned at a terminal pro-inflammatory state enriched for IL-17 and NF-κB signalling pathways. Immunofluorescence confirmed accumulation of CCL20+CD68+ macrophages at dissection sites. Cell–cell communication analysis identified enhanced SPP1–integrin signalling toward VSMCs. In vitro, CCL20 overexpression activated IL-17RA–MAPK/NF-κB signalling and significantly upregulated SPP1 expression. Dual-luciferase assays demonstrated that p65 directly increased SPP1 promoter activity. Macrophage-VSMC co-culture induced VSMCs transition from a contractile phenotype (↓ACTA2, MYH11, MYL9, SM22a) to a synthetic phenotype (↑COL1A2, COL3A1, VCAN, FN1, IGFBP2), which was attenuated by IL-17RA or SPP1 silencing. In Vivo, BAPN-treated mice exhibited elevated CCL20 and SPP1 expression, medial elastin fragmentation, and higher incidence of aortic dissection than that with treatment (P=0.0235). shCCL20 treatment significantly reduced dissection incidence and improved survival by suppressing SPP1 levels and preserving VSMC contractile markers. Conclusions CCL20+ macrophages drive TAAD via orchestrating VSMC phenotypic switching through the IL-17/NF-kB/SPP1 signalling axis. Disrupting this immunomodulatory pathway effectively preserves aortic integrity and reduces dissection incidence, establishing it as a potential therapeutic target for blocking pathogenesis of aortic dissection.