Keratin 7 protein presence in stool is indicative of active pediatric-onset inflammatory bowel disease

BackgroundInflammatory bowel disease (IBD) is associated with early structural changes in intestinal epithelial cells; however, the associated molecular alterations remain incompletely understood. The cytoskeletal protein keratin (K) 7 was recently found to be focally expressed in the colonic epithelium in IBD, while absent in the healthy colon. Here, we investigated the applicability of K7 as a noninvasive stool biomarker for pediatric IBD. MethodsIn this case-control study including adolescent patients with IBD (n=27) and healthy controls (n=15), stool lysates were analyzed by proteomics, immunoassay and qPCR to determine K7 protein and mRNA content, respectively. Additionally, stool mRNA levels of the simple epithelial keratins, K8, K18, K19 and K20, were measured. ResultsStool proteomic analysis identified focal K7 and K19 in IBD samples. Additionally, 23 differentially abundant proteins, of which 18 were higher in IBD, were identified and Gene Ontology enrichment analysis highlighted immune and inflammatory pathways. K7 specific immunoassay detected fecal K7 protein in all patients with active IBD, including both ulcerative colitis and Crohns disease, while K7 was near or below the detection limit in controls and IBD patients in remission (area under ROC curve=0.88, p<0.0001). While KRT7 mRNA levels were below the detection limit, KRT8 and KRT18 transcripts were elevated in IBD samples compared to controls (p<0.05). ConclusionsK7 protein is elevated in IBD patient stool, reflecting intestinal de novo expression and increased epithelial cell exfoliation. Fecal K7 may provide a novel, noninvasive marker for IBD diagnosis and monitoring.