Epigenetic Programming of Macrophage Phenotypes by STING-IRF3 Drives Inflammation in Ascending Thoracic Aortic...

Ascending thoracic aortic dissection (ATAD) is characterized by extensive macrophage (MΦ) accumulation and profound inflammation; however, the mechanisms sustaining pro-inflammatory MΦ activation remain incompletely defined. Emerging evidence indicates that epigenetically generated immune memory drives innate immune cells toward persistent inflammatory states. In this study, we investigated whether epigenetic reprogramming governs MΦ phenotypic fate and contributes to ATAD pathogenesis.

We performed single-cell RNA sequencing of human ascending aortic tissues from controls, patients with ascending thoracic aortic aneurysm (ATAA), and patients with acute ascending thoracic aortic dissection (ATAD). We also performed integrated single-cell RNA sequencing, single-cell ATAC sequencing, and spatial transcriptomics in an angiotensin II (Ang II)-infused mouse model. The role of the STING-IRF3 signaling axis in MΦ epigenetic programming was examined using MΦ- Sting ^-/- and MΦ- Irf3 ^-/- mice.

In human and mouse aortic tissues, we identified multiple functional MΦ populations including pro-inflammatory, phagocytic/anti-inflammatory, proliferative, and reparative/healing MΦs. Aortic MΦs in both sporadic ATAD patients and Ang II-induced ATAD mice exhibited a pronounced pro-inflammatory bias with enhanced differentiation toward pro-inflammatory MΦs and impaired differentiation toward phagocytic/anti-inflammatory states. Pro-inflammatory MΦs were particularly abundant in dissection sites, whereas phagocytic MΦs were enriched in discrete adventitial niches. Origin analyses revealed a substantial increase in CCR2 ⁺ recruited MΦs within the aortic wall, which preferentially differentiated into pro-inflammatory MΦs. In contrast, LYVE1 ⁺ resident MΦs- predominantly biased toward phagocytic phenotypes-were markedly depleted in ATAD. Single-cell ATAC sequencing identified coordinated chromatin remodeling with increased accessibility at pro-inflammatory gene loci and decreased accessibility at phagocytic gene loci. Among candidate transcriptional regulators identified, IRF family TFs, including IRF3 emerged as unique factors capable of simultaneously promoting pro-inflammatory gene programs while suppressing phagocytic gene expression. Mechanistically, STING-IRF3 signaling orchestrates this biased transcriptional state, likely through coordinated BRG1-dependent chromatin opening at pro-inflammatory gene loci and chromatin closing at phagocytic/anti-inflammatory gene loci. MΦ specific Sting ^-/- and Irf3 ^-/- mice exhibited attenuated inflammatory reprogramming and reduced aortic destruction and dissection.

These findings identify STING-IRF3-mediated epigenetic programming of MΦs as a fundamental mechanism driving aortic inflammation and ATAD development. Targeting MΦ epigenetic programming may represent a promising therapeutic strategy to prevent aortic dissection.