Cellular-Resolution Spatial Transcriptomics Reveals Laminar VSMC Phenotypic Remodeling and a Hypoxic Medial Core in Human Thoracic Aortic Dissection

Abstract

Objectives: Acute aortic syndromes (AAS) carry high short-term mortality and long-term morbidity. Hypertension is the predominant risk factor, yet no established tools identify patients at imminent risk. Despite known vascular smooth muscle cell (VSMC) phenotype switching with hypertension, the medial role in sporadic AAS is given comparatively less emphasis, compared to heritable aortopathies. We sought to define the VSMC landscape in human AAS and identify spatial remodeling programs associated with interlamellar separation. Methods: We collected human ascending aorta specimens from 8 patients undergoing open surgical AAS repair and 5 donors after brain death. Using Xenium in situ spatial transcriptomic profiling, we generated cellular-resolution maps of human ascending aorta. Tissue sections were subsequently stained for histology and immunohistochemistry. Results: In AAS, we identified extensive VSMC remodeling organized into distinct laminar domains across the aortic media, with unique VSMC states supported by gene-expression module scoring. Across patients, we identified a reproducible mid-medial core of hypoxia-adapted VSMCs spatially distinct from acute injury-associated states bounding the false lumen which were characterized by carbonic anhydrase 9 immunoreactivity and reduced -smooth muscle actin expression. Comparatively, non-dissected donor ascending aortas contained fewer remodeled VSMC states, minimal transmural striation, and no discrete regions of hypoxia-adapted VSMCs. Conclusions: These findings define a spatially organized medial remodeling landscape in AAS and identify hypoxia-associated VSMC modulation as a potential feature of medial domains associated with heightened vulnerability to interlamellar separation. Defining these remodeling domains may inform improved risk stratification and experimental models that better recapitulate human AAS pathology.