Transforming growth factor beta 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 b (TGFb) is a potent profibrogenic agent inducing collagen synthesis and regulating the balance between matrix-degrading matrix metalloproteinases (MMPs) and their inhibitors (TIMPs). TGFb 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 nonstrictured gut of patients with fibrostenosing CD. Isolated myofibroblasts were cultured with anti-TGFb blocking antibody or TGFb1. TGFb 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: TGFb transcripts, phosphorylated Smad2– Smad3 (pSmad2–3) and TIMP-1 proteins were higher in mucosa overlying strictures than in mucosa overlying nonstrictured 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 TGFb transcripts, a greater pSmad2–3 response to TGFb, increased TIMP-1, lower Smad7, increased collagen production and reduced migration ability compared with myofibroblasts from mucosa overlying non-strictured gut. TGFb 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-b signalling and MMP production were identified in the mucosa overlying strictures in CD which may give a window into the process of fibrosis.