NOX4 signatures in human abdominal aortic aneurysm reveal links to vascular cell plasticity, extracellular matrix remodeling and inflammation.

BACKGROUND

NADPH-oxidase 4 (NOX4) is the predominant isoform of NADPH oxidases in the vasculature. While global deletion of NOX4 protects against abdominal aortic aneurysm (AAA) formation in mice, cell-specific overexpression promotes disease development. However, the cellular sources of NOX4 and the associated transcriptional programs in human AAA remain incompletely understood.

METHODS

NOX4 was investigated using single-cell RNA sequencing and histopathological analyses of AAA tissue.

RESULTS

NOX4 mRNA expression was comparable between ruptured AAA (rAAA) and electively treated AAA (eAAA) and did not correlate with AAA size, AAA volume, or thickness of the intraluminal thrombus. In human AAA, NOX4 expression correlated with markers of inflammatory signaling, extracellular matrix (ECM) remodeling, and antioxidant responses, while showing an inverse relationship with the endothelial marker CD31. Single-cell RNA sequencing revealed predominant NOX4 expression in fibroblasts and smooth muscle cells (SMCs). In these populations, higher NOX4 levels were associated with transcriptional programs related to ECM synthesis and remodeling, SMC phenotypic modulation, myofibroblast differentiation, and pathways involved in proliferation, migration, and redox metabolism. Notably, NOX4+ SMCs were enriched for proteoglycan biosynthesis pathways, whereas NOX4+ fibroblasts were associated with iron ion transport processes. In contrast, NOX4 expression was low in endothelial cells (ECs), and pseudotime analysis suggested a transition from ECs toward myofibroblast-like states accompanied by increased NOX4 expression, consistent with endothelial-to-mesenchymal transition.

CONCLUSION

In human AAA, NOX4 is primarily expressed in fibroblasts and SMCs and is associated with transcriptional programs linked to inflammation, ECM remodeling, and cellular phenotype modulation. These findings indicate that NOX4 reflects disease activity and vascular remodeling rather than AAA size and highlight NOX4 as a potential target for cell type-specific therapeutic strategies in AAA.