Spatially resolved proteomic landscape unveils the molecular dichotomy of distal stenosis and proximal dilation in pediatric type Ia congenital biliary dilatation

Congenital biliary dilatation (CBD) in children remains a disease of enigmatic origin. Prevailing theories focusing on anomalous pancreaticobiliary ductal union (APBDU) fail to explain the critical anatomical hallmark of Type Ia CBD: the coexistence of a distal stenotic segment (DSS) and a proximal dilated segment (PDS). We aimed to define region-specific molecular landscapes to bridge this fundamental gap. We conducted label-free proteomic and histomorphometric analyses on distinct surgical specimens-cystic duct (CD: as the least-affected internal reference), DSS, and PDS-from pediatric CBD patients (n = 5 proteomics; n = 12 validation). Key findings were rigorously validated using multiplex immunofluorescence, immunohistochemistry, and functional enrichment. Proteomic profiling established DSS and PDS as biologically distinct pathological entities. While both segments shared severe epithelial dysfunction and mechanosensory ciliary loss, a profound molecular dichotomy emerged in smooth muscle remodeling. The DSS was characterized by robust ferroptosis-associated fibrosis (TFR1/α-SMA co-localization) and β-amyloid-associated neural degeneration. Conversely, the PDS exhibited marked muscular atrophy and wall tension failure (CALD1 upregulation). This regional proteomic atlas reveals a pronounced spatial dichotomy, calling into question the adequacy of traditional uniform disease models. These findings suggest that ferroptosis may contribute to distal stenosis and highlight potential therapeutic targets to mitigate fibrosis and improve long-term surgical outcomes.