Abstract
<title>Abstract</title> <p>Background Coarctation of the aorta (CoA) is a congenital narrowing of the aorta associated with persistent vascular morbidity even after anatomical repair. The molecular features of the stenotic aortic wall remain incompletely characterized. This study aimed to define protein abundance changes in pediatric CoA tissue and integrate proteomic findings with histopathological remodeling. Methods Aortic tissue was obtained from 14 pediatric patients undergoing resection and end-to-end anastomosis. Stenotic and macroscopically normal aortic segments were assessed using seven histopathological staining methods. After quality control, 15 stenotic (AoA) and 11 normal (AoN) tissue samples were retained for data-independent acquisition (DIA) proteomic quantification. Differential abundance was assessed using two-sided independent-samples t tests. Proteins with |log2 fold change| ≥ 0.58 and P < 0.05 were treated as exploratory differentially abundant proteins, with Benjamini-Hochberg false discovery rate (FDR) values reported separately. Downstream analyses included functional enrichment, protein-protein interaction analysis, mechanistic module annotation, exploratory candidate prioritization, cross-version stability review, and pathology-proteomics integration. Results Histopathology showed intimal thickening, extracellular matrix and collagen accumulation, elastic fiber fragmentation, smooth muscle cell loss and disorganization, and reduced proliferative staining in stenotic tissue. DIA proteomics identified 153 exploratory differentially abundant proteins, including 84 with higher and 69 with lower abundance in AoA; 15 met FDR < 0.05. Structural collagen scaffold proteins, including COL1A1, COL1A2, COL6A1, COL6A3, COL14A1, and OGN, were predominantly lower in AoA, whereas collagen maturation enzymes PLOD1, PLOD2, and P4HA2 and elastic fiber remodeling proteins were higher. Sixty-three proteins were shared across two internal analysis versions, all with concordant direction of change. An integrated evidence matrix identified collagen structural remodeling as the most internally concordant mechanistic theme. Conclusions Pediatric CoA stenotic tissue showed a coordinated but directionally heterogeneous extracellular matrix remodeling profile, characterized by lower abundance of several structural collagen proteins together with higher abundance of collagen hydroxylation and elastic fiber remodeling proteins. These findings provide a hypothesis-generating molecular framework for CoA aortic wall pathology. Because most proteins were nominally significant and no independent cohort or targeted protein validation was available, the results require external replication and functional confirmation.</p>