Summary: Background: Increased collagen remodelling is a key pathophysiological component underlying intestinal stricture and fistula development in Crohn's disease (CD).Aims: To investigate associations between serological biomarkers of collagen turnover and disease behaviour according to the Montreal classification in patients with CD.Methods: Serological biomarkers of type III/IV collagen formation (PRO‐C3, PRO‐C4) and matrix metalloproteinase (MMP) or granzyme‐B (GrzB)‐mediated type I, III, IV and VI collagen degradation (C1M, C3M, C4M, C4G, C6Ma3) were measured using neo‐epitope protein fingerprint assays in 101 patients with CD (Montreal B1: n = 37; B2: n = 27; B3: n = 37) and 96 controls. Patients were followed up until their last outpatient visit to monitor stricturing/penetrating disease progression and recurrence and the occurrence of surgical interventions.Results: C1M, C3M and C4M were significantly reduced in patients with stricturing disease (Montreal B2) and accurately differentiated them from patients with either non‐stricturing, non‐penetrating (B1) or penetrating (B3) disease (all p < 0.001, multivariable analysis). Similarly, the type IV collagen formation/degradation (PRO‐C4/C4M) ratio demonstrated high discriminative capacity (B1/B2: AUC = 0.90; B1/B3: AUC = 0.87, both p < 0.001, multivariable analysis). Prospectively, higher baseline levels of C1M and C4G were associated with an increased risk of penetrating disease progression (C4G: hazard ratio [HR] 1.71 [1.05–2.81], p < 0.05).Conclusions: Elevated degradation of type I, III and IV collagen and excessive (relative) formation of type IV collagen strongly associates with stricturing CD. Type I and IV collagen fragments show predictive potential for the risk of penetrating disease progression. These biomarkers may become valuable tools for detection and prediction of stricturing and penetrating CD.

Crohn’s disease (CD) is a relapsing-remitting inflammatory disease of the gastrointestinal (GI) tract characterized by increased extracellular matrix (ECM) remodeling. The introduction of the α4β7-integrin inhibitor vedolizumab (VEDO) has improved disease management, although there is a high rate of primary non-response in patients with CD. We studied whether ECM biomarkers of neutrophil activity and mucosal damage could predict long-term response to VEDO in patients with CD. Serum levels of human neutrophil elastase (HNE)-derived fragments of calprotectin (CPa9-HNE), and matrix metalloproteinase (MMP)-derived fragments of type I (C1M), III (C3M), IV (C4M), and VI (C6Ma3) collagen, type III collagen formation (PRO-C3), basement membrane turnover (PRO-C4) and T-cell activity (C4G), were measured using protein fingerprint assays in patients with CD (n = 32) before VEDO therapy. Long-term response was defined as VEDO treatment of at least 12 months. CPa9-HNE was significantly increased at baseline in non-responders compared with responders (p < 0.05). C1M, C3M, C4M, C6Ma3, and PRO-C4 were also significantly increased at baseline in non-responders compared with responders (all p < 0.05). All biomarkers were associated with response to VEDO (all p < 0.05). To conclude, baseline levels of serum biomarkers for neutrophil activity and mucosal damage are linked to the pathology of CD, and are associated with long-term use of VEDO in patients with CD. Therefore, these biomarkers warrant further validation and could aid in therapeutic decision-making concerning vedolizumab therapy.

Background: Crohn’s disease (CD) is characterized by excessive protease activity and extracellular matrix (ECM) remodeling. To date, 30–50% of patients experience non-response to anti-TNF-α treatment. This study aimed to assess whether serological biomarkers of ECM turnover could monitor or predict response to infliximab (IFX) induction therapy in patients with and without a surgical history.Methods: Serum biomarkers of type I (C1M), III (C3M), IV (C4M), and VI (C6Ma3) collagen degradation, type III (PRO-C3) and VI (PRO-C6) collagen formation, basement membrane turnover (PRO-C4), and T-cell activity (C4G), were measured at baseline and week 14, in 63 patients with CD undergoing IFX induction therapy. Patients were stratified according to surgical history.Results: C4M was elevated at baseline in responders with a surgical history (n = 10) and associated with response at baseline (P < 0.05). Additionally, C6Ma3, PRO-C3, and PRO-C6 were elevated at week 14 in responders compared with non-responders (n = 8) and could differentiate between the two groups (P < 0.05). Two biomarker ratios (C4M/C4G and PRO-C4/C4G) were elevated at week 14 in non-responders (n = 5) without a surgical history compared with responders (n = 40) and could differentiate between the response groups (P < 0.05).Conclusion: Baseline levels of a serological biomarker for type IV collagen degradation associated with response to IFX induction therapy, and biomarkers of type III and VI collagen formation may be used to monitor response at the end of induction therapy in patients with a surgical history. Biomarker ratios of type IV collagen turnover demonstrated promising results in monitoring treatment response in patients without a surgical history.

Neutrophils play a significant role in sustaining chronic inflammation in Inflammatory Bowel Disease. The intestinal basement membrane acts as a barrier for immunological homeostasis, where the α3 and α4 chains of type IV collagen are expressed on the mucosal surface. We wanted to develop a biomarker reflecting early tissue injury, providing an opportunity for intervention. Two competitive enzyme-linked immunosorbent assays (ELISAs) quantifying human neutrophil elastase (HNE) degraded neo-epitopes of COL4A3 and COL4A4 were developed and investigated in two observational cohorts (n = 161, n = 100). A biomarker of MMP-mediated degradation of COL4A1 (C4M) was used for comparison. In Cohort 1, patients with mild endoscopic ulcerative colitis showed elevated levels of C4A3-HNE compared to those with severe disease. C4M had a strong positive correlation with disease activity. C4A3-HNE/C4M provided superior discrimination between mild and severe endoscopic disease and negatively correlated to disease activity. In Cohort 2, C4A4-HNE and C4A4-HNE/C4M showed similar trends. C4A3-HNE and C4A4-HNE possibly reflect early intestinal tissue injury. Combining the markers with a biomarker of another α-chain of the same collagen provides information on two distinct stages of mucosal damage. These biomarkers may be used to monitor disease flare-up in patients in remission, reducing the need for frequent endoscopic procedures.

Background and Aims: Crohn’s disease (CD) is characterized by progressive intestinal transmural damage, including fibrosis and strictures, which impair quality of life and require surgical intervention. No anti-stricture therapies are available, and no accurate biomarkers have been validated allowing prediction of strictures. Collagen fragments synthesis and remodeling show potential as markers of transmural disease activity. This study aimed to evaluate serum collagen markers for their accuracy in differentiating between stenosing and luminal CD and assessing their correlation with histopathology. Methods: Sixty-two patients undergoing resection for stricturing CD and 49 with luminal CD were prospectively included. Extracellular matrix (ECM) markers were quantified using ELISA, and histological assessments of fibrosis and inflammation were performed on full-thickness tissue samples. Clinical outcomes, biomarkers, and histology were analyzed over a 12-month follow-up. Results: Extracellular matrix markers, including PRO-C6, PRO-C3, PRO-C5, C4M, and PRO-C4, distinguished stenosing from luminal CD with and the combination of PRO-C6, PRO-C3, and PRO-C5 achieved the highest discriminative power of (AUC 0.91). Significant changes in levels of the collagen biomarker were observed post-resection. Histological analysis revealed extensive intestinal fibrosis in the submucosa of the stenotic segments, which correlated with PRO-C6 levels. C4M and PRO-C4 positively correlated with neutrophils in the lamina propria. CTX-III correlated negatively with the D’Haens score and neutrophils and mononuclear cells in the lamina propria and in the epithelium. Conclusions: Collagen markers distinguished stenosing from luminal CD, and they correlated with histological fibrosis and chronic inflammation, promising for understanding ECM remodeling. This study highlights the need for extended follow-up to assess long-term stenosis-related outcomes.

Chronic inflammation in inflammatory bowel disease (IBD) triggers significant extracellular matrix remodeling, including elastin remodeling, leading to severe clinical complications. Novel methods to assess intestinal tissue destruction may act as surrogate markers of endoscopic disease activity, relieving patients of invasive endoscopy. We explored the noninvasive blood-based biomarkers ELP-3 and ELM-12, measuring elastin degradation in IBD. In a study involving 104 Crohn’s disease (CD), 39 ulcerative colitis (UC), and 29 healthy donors, we assessed these biomarkers’ association with endoscopic and clinical disease activity using ELISA. Patients were evaluated based on the SES-CD and CDAI for CD patients and modified MES and partial Mayo for UC patients. ELP-3 and ELM-12 were elevated in patients with IBD. Discerning CD patients in endoscopic remission and mild from moderate to severe, ELP-3 provided an AUC of 0.69 and ELM-12 an AUC of 0.73. The ELP-3 biomarker was associated with UC patients and provided the highest diagnostic power of 0.87 for remission vs. active clinical disease. The data suggest an association of ELP-3 with active CD and ELM-12 with endoscopic remission in CD patients. Additionally, ELP-3 could identify UC patients with active clinical disease from patients in remission. The noninvasive biomarkers ELP-3 and ELM-12 could be potential surrogate biomarkers of elastin degradation and endoscopic and clinical disease markers.