Novel proteomic signatures of stricturing Crohn disease using a treatment-naive cohort.

BACKGROUND: Crohn disease (CD) is frequently complicated by intestinal strictures, which require early recognition and management. This study aimed to identify biomarkers associated with CD-related strictures by use of serum and intestinal proteomics and to develop diagnostic and predictive models for potential clinical application. METHODS: Serum samples from treatment-naive CD patients and paired intestinal samples from stricturing intestine were subjected to proteomic analysis. Machine learning approaches were employed to select stricture-related biomarkers and develop models. The candidate protein was validated using external cohorts and molecular experiments. RESULTS: The discovery cohort included 62 patients. A diagnostic model for intestinal stricture was developed using serum levels of 5 proteins from 30 nonstricturing, nonpenetrating (B1) phenotype and 20 stricturing (B2) phenotype patients, achieving an area under the curve of 0.754. A predictive model for stricture progression, based on another set of 5 proteins in 10 B1 progressors, achieved an AUC of 0.947 internally. Serum enzyme-linked immunoassay (ELISA) validation in the First Affiliated Hospital of Sun Yat-sen University (FAH-SYSU) and Sir Run Run Shaw Hospital (SRRSH) cohorts (n = 62) confirmed elevated glypican-6 (GPC6) levels in the stricturing (B2) group, with a similar trend observed in intestinal tissue in the progression group of the RISK cohort (n = 237). Single-cell transcriptomic analysis and immunofluorescence staining further confirmed higher GPC6 expression and protein levels in the fibrostenotic mucosa and submucosa, particularly in fibroblasts. CONCLUSIONS: We developed serum-based diagnostic and predictive models for intestinal strictures in CD, which may be suitable for clinical use once externally adequately validated. GPC6 emerged as a candidate biomarker closely associated with intestinal fibrosis, offering promising implications for its diagnosis and prognosis.