Misbalance in type III collagen formation/degradation as a novel serological biomarker for penetrating (Montreal B3) Crohn's disease

BACKGROUND: Misbalances in extracellular matrix turnover are key factors in the development of stricturing (Montreal B2) and penetrating (Montreal B3) Crohn's disease. AIM: To determine whether serological markers for collagen formation and degradation could serve as biomarkers for complications of Crohn's disease. METHODS: Serum biomarkers for type I, III, V and VI collagen formation (P1NP, Pro‐C3, Pro‐C5, Pro‐C6) and matrix metalloproteinase mediated degradation (C1M, C3M, C5M and C6M) were measured in a retrospective, single centre cohort of 112 patients with Crohn's disease in the terminal ileum (nonstricturing/nonpenetrating: n=40, stricturing: n=55, penetrating: n=17) and 24 healthy controls. Active inflammation was defined as CRP >5 mg/L. RESULTS: C3M and Pro‐C5 levels were higher in penetrating vs nonpenetrating/nonstricturing and stricturing disease (33.6±5 vs 25.8±2.2 [P=.004] and 27.2±2.3 [P=.018] nmol/L C3M, 1262.7±259.4 vs 902.9±109.9 [P=.005] and 953.0±106.4 [P=.015] nmol/L Pro‐C5). C1M (71.2±26.1 vs 46.2±6.2 nmol/L [P<.001]), C3M (31.6±3.9 vs 26.1±1.6 nmol/L [P=.002] and Pro‐C5 levels (1171.7±171.5 vs 909.6±80.4 nmol/L [P=.002]) were higher in patients with active inflammation vs without active inflammation. Pro‐C3/C3M‐ratios were best to differentiate between penetrating vs nonstricturing/nonpenetrating and stricturing disease with area under the curves of 0.815±0.109 (P<.001) and 0.746±0.114 (P=.002) respectively. CONCLUSIONS: Serological biomarkers show that penetrating Crohn's disease is characterised by increased matrix metalloproteinase‐9 degraded type III collagen and formation of type V collagen. Active inflammation in Crohn's disease is characterised by increased formation of type V collagen and increased matrix metalloproteinase mediated breakdown of type I, III collagen. Pro‐C3/C3M ratios are superior in differentiating between penetrating Crohn's disease vs inflammatory and stricturing Crohn's disease.