Transforming growth factor β signalling and matrix metalloproteinases in the mucosa overlying Crohn's disease strictures

Background and Aims: In addition to its crucial role in dampening tissue-damaging immune responses in the gut, transforming growth factor beta (TGF beta) is a potent profibrogenic agent inducing collagen synthesis and regulating the balance between matrix-degrading matrix metalloproteinases (MMPs) and their inhibitors (TIMPs). TGF beta signalling was investigated by analysis of Smad proteins and MMPs/TIMPs in the mucosa overlying strictures in patients with Crohn's disease (CD). Methods: Specimens were collected from macroscopically normal mucosa overlying strictured and non-strictured gut of patients with fibrostenosing CD. Isolated myofibroblasts were cultured with anti-TGF beta blocking antibody or TGF beta 1. TGF beta transcripts were analysed by quantitative reverse transcription-PCR (RT-PCR). Smad proteins and MMPs were determined by immunoblotting. MMP-12 activity was measured by a real-time MMP-12 activity assay. An in vitro wound-healing scratch assay was used to assess myofibroblast migration. Results: TGF beta transcripts, phosphorylated Smad2-Smad3 (pSmad2-3) and TIMP-1 proteins were higher in mucosa overlying strictures than in mucosa overlying non-strictured areas. In contrast, mucosa overlying strictured gut had lower expression of Smad7, MMP-12 and MMP-3. Myofibroblasts from mucosa overlying strictured gut showed higher TGF beta transcripts, a greater pSmad2-3 response to TGF beta, increased TIMP-1, lower Smad7, increased collagen production and reduced migration ability compared with myofibroblasts from mucosa overlying non-strictured gut. TGF beta blockade increased myofibroblast MMP-12 production and migration, more obviously in myofibroblasts isolated from mucosa overlying non-strictured compared with strictured gut. Conclusions: Changes in TGF-beta signalling and MMP production were identified in the mucosa overlying strictures in CD which may give a window into the process of fibrosis.