Fibrostenotic Phenotype of Myofibroblasts in Crohn's Disease is Dependent on Tissue Stiffness and Reversed by LOX Inhibition.

BACKGROUND AND AIMS: Crohn's disease is a chronic inflammatory disorder of the intestine and often leads to fibrosis, characterized by excess extracellular matrix [ECM] deposition, increased tissue stiffness, and stricture formation. Here we evaluated the contribution of myofibroblast-ECM interactions to the development of intestinal fibrosis in Crohn's disease. METHODS: Matched primary human myofibroblasts were isolated from stenotic, inflamed and normal-appearing small intestine within the same Crohn's disease patient [n = 10]. Cells were analyzed by gene expression profiling, microscopy and functional assays, including matrix metalloproteinase [MMP] production and ECM contraction. RESULTS: We demonstrated that myofibroblasts isolated from stenotic intestine differed both in phenotype and function from those isolated from purely inflammatory or normal-appearing intestine of the same patient. Stenotic myofibroblasts displayed increased expression of genes associated with ECM modulation and collagen deposition. Upon culture in a fibrotic environment, normal myofibroblasts increased expression of MMPs to counteract the mechanical force exerted by the matrix. Interestingly, stenotic myofibroblasts showed a paradoxical response with decreased expression of MMP3. In addition, stenotic myofibroblasts expressed increased levels of the collagen crosslinking enzyme lysyl oxidase [LOX] and induced significantly more ECM contraction than both normal and inflamed myofibroblasts. Importantly, LOX inhibition completely restored MMP3 activity in stenotic myofibroblasts grown in a fibrotic environment, and prevented excessive ECM contraction. CONCLUSIONS: Together these data indicate aberrancies in the myofibroblast-ECM interaction in Crohn's disease, and identify LOX inhibition as a potential anti-fibrotic agent in this condition.

Intestinal fibrosis is associated with lack of response to Infliximab therapy in Crohn's disease.

INTRODUCTION: Overt fibrostenotic disease is a relative contraindication for anti-TNF therapy in Crohn's disease. We hypothesized that subclinical fibrosis may also contribute to an incomplete response to anti-TNF therapy before the onset of symptomatic stenosis. METHODS: In a previous trial, patients with ileocecal Crohn's disease were randomized to either immediate ileocecal resection or medical treatment with Infliximab. In case of insufficient response to Infliximab, the latter underwent secondary ileocecal resection. We compared specimens from those patients undergoing immediate resection (Infliximab naïve, n = 20) to those who failed Infliximab therapy (n = 20). RESULTS: Infliximab naïve and Infliximab failure patients had similar severity of inflammation when assessed by CRP levels (median 14 vs 9 mg/L) and histology (Geboes-D'Haens-score, median 10 vs 11 points). On immunohistochemistry, collagen-III and fibronectin depositions were increased in patients previously exposed to Infliximab compared to patients naïve to Infliximab. On mRNA level, procollagen peptidase showed significantly more mucosal mRNA expression in Crohn's disease patients who failed Infliximab. Infliximab responders showed no increase of this marker after 4 weeks of successful Infliximab treatment. DISCUSSION: Failure to Infliximab therapy is associated with subclinical fibrosis in Crohn's disease.