Behçet’s disease (BD) is a chronic inflammatory disorder characterized by oral and genital ulcers, uveitis and skin lesions, with potential involvement of vital organs including the cardiovascular, nervous and gastrointestinal systems. Vascular BD (VBD) can lead to recurrent vascular events in veins and arteries of all sizes. Approximately one-third of VBD patients have multi-vessel lesions, which are prone to recurrence and associated with a higher incidence of postoperative complications. However, the underlying pathogenic mechanisms of VBD remain unclear. Identifying VBD-specific cell subsets and clarifying their roles in the aortic microenvironment is essential for deciphering the pathogenesis of VBD and developing targeted therapies.

Single-cell RNA sequencing was performed to generate a single-cell atlas of VBD ascending aorta and identify key pathogenic cell subsets. Immunofluorescence staining, bulk RNA sequencing, and functional co-culture systems were employed to explore the phenotypic characteristics of pathological population and potential intercellular interactions. A CaCl₂-induced humanized VBD model was established to investigate the pathogenic role of key subsets in vivo.

Single-cell RNA sequencing identified a THBS1^high macrophage subset which was significantly enriched in the VBD ascending aorta, with a particularly higher proportion in the aorta of active VBD. THBS1^high macrophages exhibited pro-inflammatory phenotype, highly expressed pro-inflammatory and chemotactic factors. Furthermore, THBS1^high macrophages showed active communication with smooth muscle cells, inducing phenotypic transition of  smooth muscle cells. In vivo studies showed that adoptive transfer of THBS1^high macrophages exacerbated vascular inflammation and aneurysm formation in VBD mice, which could be alleviated by TNF inhibitor adalimumab.

Our study comprehensively depicts the transcriptomic landscape of VBD ascending aorta at the single-cell level, identifying THBS1^high macrophages as a key pathogenic subset driving vascular inflammation and smooth muscle cell phenotypic transition. TNF inhibitor can mitigate THBS1^high macrophage-induced vascular injury. These findings provide new insights into the pathogenesis of VBD, highlighting the therapeutic potential of anti-TNF therapy in VBD.