Identification and validation of fecal complement component 3 and fibronectin as potential biomarkers for monitoring disease activity in ulcerative colitis based on a mouse model

BACKGROUND: Ulcerative colitis (UC) is a typical inflammatory bowel disease requiring long-term management. Although fecal calprotectin (FC) is widely employed for assessing disease activity, it is still considered insufficient as a standalone tool. New biomarkers are needed to better predict risk and comprehensively reflect biological pathways. This study aimed to identify potential fecal biomarkers to monitor disease activity in UC. METHODS: C57BL/6J mice were exposed to dextran sulfate sodium (DSS) treatment for 7 days. Feces were collected and subjected to proteomic analysis and enzyme-linked immunosorbent assay (ELISA). Mouse colon tissues were subjected to histopathological and immunofluorescence analyses. The correlations between the selected fecal proteins and disease severity were evaluated and compared with FC. RESULTS: Proteomic analysis revealed increases in fecal complement component 3 (C3) and fibronectin (FN) in the DSS group. Next, we measured fecal C3 and FN levels in mice using ELISA. Significant elevation in C3 and FN levels was observed as early as day 1 after DSS treatment, preceding the increase in FC. Both fecal C3 and FN demonstrated significant correlations with disease activity, with C3 exhibiting a stronger correlation than FC. Using immunofluorescence, we observed distinct C3 and FN expressions in both the colonic tissues and the intestinal lumen. CONCLUSION: These findings demonstrate that fecal C3 and FN are promising candidate biomarkers for monitoring UC disease activity, and their utility requires further validation in other colitis models and human cohorts.