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Intestinal fibrosis, the most common complication of inflammatory bowel disease (IBD), is characterized by an uncontrolled deposition of extracellular matrix proteins leading to complications resolvable only with surgery. Transforming growth factor is the key player in the epithelial-mesenchymal transition (EMT) and fibrogenesis process, and some molecules modulating its activity, including peroxisome proliferator-activated receptor (PPAR)-γ and its agonists, exert a promising antifibrotic action. The purpose of this study is to evaluate the contribution of signaling other than EMT, such as the AGE/RAGE (advanced glycation end products/receptor of AGEs) and the senescence pathways, in the etiopathogenesis of IBD. We used human biopsies from control and IBD patients, and we used a mouse model of colitis induced by dextran-sodium-sulfate (DSS), without/with treatments with GED (PPAR-gamma-agonist), or 5-aminosalicylic acid (5-ASA), a reference drug for IBD treatment. In patients, we found an increase in EMT markers, AGE/RAGE, and senescence signaling activation compared to controls. Consistently, we found the overexpression of the same pathways in DSS-treated mice. Surprisingly, the GED reduced all the pro-fibrotic pathways, in some circumstances more efficiently than 5-ASA. Results suggest that IBD patients could benefit from a combined pharmacological treatment targeting simultaneously different pathways involved in pro-fibrotic signals. In this scenario, PPAR-gamma activation could be a suitable strategy to alleviate the signs and symptoms of IBD and also its progression.

Objectives Non-alcoholic fatty liver disease (NAFLD) has become the most common liver disease globally. It is caused by a complex network of factors, including diet. The hallmark of NAFLD is the benign accumulation of triacylglycerols, however, this condition may worsen into non-alcoholic steatohepatitis (NASH), a more severe form associated with inflammation and fibrosis. Currently, no therapies are available, and diet modifications are the only strategy. Although there is increasing evidence emerging about how an abuse of carbohydrates could be involved in the progression of liver injury, a comprehensive understanding of the damage induced by an enriched carbohydrate diet is still far from complete. The aim of this study was to investigate and compare the effects of a low-fat/high-carbohydrate diet (LF-HCD) with high-fat (HFD) and standard (SD) diets in a nutritional mouse model of NAFLD/NASH. Methods Histologic, real-time polymerase chain reaction, and immunohistochemical evaluations were performed. Results The results showed that the prolonged abuse of both LF-HCDs and HFDs induced a significant increase in hepatic steatosis, inflammation, and fibrosis scores compared with SD. At the same time, both LF-HCDs and HFDs led to significant increases in the expression of the molecules involved in the progression of NAFLD that we assessed (perilipin, CD68, TGF-β1, CTGF, leptin, leptin receptor, and α-SMA). Conclusions The present study highlighted that the simple substitution of fats with carbohydrates is not a proper strategy to prevent or mitigate the progression of NAFLD/NASH. Further studies are required to define the best nutritional strategy to prevent NAFLD and its related metabolic syndrome.

BACKGROUND Intestinal fibrosis is mainly associated with Crohn's disease and is defined as a progressive and excessive deposition of extracellular matrix components. No specific antifibrotic therapies are available. In this study, we evaluate the antifibrotic effect of a novel 5-ASA analog able to activate the peroxisome proliferator-activated receptor γ, named GED-0507-34 Levo. METHODS Colonic fibrosis was induced in 110 C57BL/6 mice by 3 cycles of 2.5% (wt/vol) dextran sulfate sodium administration for 6 weeks. The preventive effects of oral daily GED (30 mg · kg(-1) · d(-1)) administration were evaluated using a macroscopic and histological score and also through biological endpoints. Expression of main markers of myofibroblasts activation was determined in transforming growth factor (TGF-β)-stimulated intestinal fibroblasts and epithelial cells. RESULTS GED improved macroscopic and microscopic intestinal lesions in dextran sulfate sodium-treated animals and reduced the profibrotic gene expression of Acta2, COL1a1, and Fn1 by 1.48-folds (P < 0.05), 1.93-folds (P < 0.005), and 1.03-fold (P < 0.05), respectively. It reduced protein levels of main markers of fibrosis (α-SMA and Collagen I-II) and the main TGF-β/Smad pathway components. GED also decreased the interleukin-13 and connective tissue growth factor expression by 1.89-folds (P < 0.05) and 2.2-folds (P < 0.005), respectively. GED inhibited TGF-β-induced activation of both fibroblast and intestinal epithelial cell lines, by regulating mRNA expression of α-SMA and fibronectin, and restoring the TGF-β-induced loss of intestinal epithelial cell markers. GED treatment also reduced the TGF-β and ACTA1 expression in primary human intestinal fibroblasts from ulcerative colitis patients. CONCLUSIONS GED ameliorates intestinal fibrosis in dextran sulfate sodium-induced chronic colitis in mice and regulates major profibrotic cellular and molecular mechanisms.

Intestinal fibrosis is a process characterized by an excessive deposition of Extracellular Matrix (ECM) proteins by activated myofibroblasts and represents a consequence of a chronic inflammation that usually occurs during Inflammatory Bowel Disease (IBD). The relationship between inflammation and fibrosis in IBD remains still unclear and nevertheless the recent pharmacological progresses, currently the only resolutive therapeutic strategy is surgery, especially when complications (stricture, stenosis and obstruction of intestinal tracts) appear. As many different cellular types and molecular mechanisms are implicated in the pathogenesis of IBD, the identification of molecules able to counteract this process could be crucial.This is a literature review of several articles published on PubMed databases.A number of researches suggest that Proliferator-Activated Receptor-gamma (PPAR-γ) has both anti-inflammatory and anti-fibrotic effects in many organs. PPAR-γ has been demonstrated to be able to downregulate pro-inflammatory cytokines production such as Interleukin (IL)-4,-5,-6 but also to interfere with profibrotic molecules as Platelet-Derived Growth Factor (PDGF), IL-1 and Transforming Growth Factor Beta (TGF-β), the main promoter of fibrosis. In preliminary clinical trials and in experimental models of intestinal fibrosis, natural and chemical PPAR-γ ligands have ameliorated the fibrotic process.Since PPAR-γ could play a crucial role in the development of the disease, the research of new molecules, capable of ameliorating both inflammation and fibrosis lesions, as PPAR-γ agonists, could represent a valid and effective therapeutic approach for the prevention and treatment of IBD and intestinal fibrosis.

Background Hepatic fibrosis is characterized by a progressive accumulation of fibrillar extracellular matrix (ECM) proteins, produced by activated myofibroblasts which are modulated by both profibrotic and antifibrotic factors. Objective To evaluate in vivo the expression of pro-fibrotic molecules like avβ6 integrin, transforming growth factor-β (TGF-β), Smad3, connective tissue growth factor (CTGF) and mammalian target of Rapamycin (mTOR), as well as anti-fibrotic peroxisome proliferator-activated receptor-γ (PPARγ) in an experimental model of chronic hepatitis-associated fibrosis induced by intraperitoneal administration of dimethylnitrosamine (DMN) in mice. Methods Chronic hepatitis was induced in 12 Smad3 wild-type (WT) and 12 knock-out (KO) mice by intraperitoneal DMN administration. Histological, morphometric and immunohistochemical analyses using α-smooth muscle actin (α-SMA), collagen types I–III, TGF-β1, Smad3, avβ6 integrin, CTGF, mTOR and PPARγ antibodies were performed. Results The liver of DMN-treated Smad3 WT mice showed a higher degree of hepatic accumulation of connective tissue compared to KO mice. The expression of α-SMA, collagen I–III and CTGF was increased in Smad3 WT compared to KO mice treated with DMN, associated with a concomitant up-regulation of avβ6, TGFβ, Smad3, and mTOR and a reduction in PPARγ expression. Conclusions These results suggest a possible interaction between pro-fibrotic and anti-fibrotic molecules in the development of hepatic fibrosis.

One of the main mechanisms carried out by the cells to counteract several forms of stress is the activation of the nuclear factor erythroid 2-related factor (Nrf2) signaling. Nrf2 signaling controls the expression of many genes through the binding of a specific cis-acting element known as the antioxidant response element (ARE). Activation of Nrf2/ARE signaling can mitigate several pathologic mechanisms associated with an autoimmune response, digestive and metabolic disorders, as well as respiratory, cardiovascular, and neurodegenerative diseases. Indeed, several studies have demonstrated that Nrf2 pathway plays a key role in inflammation and in cancer development in many organs, including the intestine. Nrf2 appears to be involved in inflammatory bowel disease (IBD), an immune-mediated chronic and disabling disease, with a high risk of developing intestinal fibrotic strictures and cancer. Currently, drugs able to increase cytoprotective Nrf2 function are in clinical trials or already being used in clinical practice to reduce the progression of some degenerative conditions. The role of Nrf2 in cancer development and progression is controversial, and drugs able to inhibit abnormal levels of Nrf2 are also under investigation. The goal of this review is to analyze and discuss Nrf2-dependent signals in the initiation and progression of intestinal fibrosis and cancers occurring in IBD.

Background: Hepatic fibrosis is characterized by a progressive accumulationof fibrillar extracellular matrix (ECM) proteins including collagen, whichoccurs in most types of chronic liver diseases. Transforming growth factor-b(TGF-b)/Smad3signalling playsacentralroleintissuefibrogenesis,actingasapotent stimulus of ECM accumulation. Aim: To evaluate the potentialprotective role of Smad3 deficiency in the pathogenesis of liver fibrosisinduced by dimethylnitrosamine (DMN) in Smad3 null mice. Methods: -Chronic hepatitis-associated fibrosis was induced in 13 Smad3 null and 13wild-type (WT) mice by intraperitoneal DMN administration (10mg/g bodyweight/day) for three consecutive days per week for 6 weeks. The liver wasexcised for macroscopic examination and histological, morphometric andimmunohistochemical (IHC) analyses. For IHC, a-smooth muscle actin (a-SMA), collagen types I–III, TGF-b1, connective tissue growth factor (CTGF),Smad3, Smad7 and CD3 antibodies were used. Results: At macroscopicexamination, the liverofDMN-treated Smad3WTappearedharder with a darkbrown colouring and necrotic areas compared with that from null mice.Histologicalandmorphometricevaluationrevealedasignificantlyhigherdegreeof hepatic fibrosis and accumulation of connective tissue in the Smad3 WTcomparedwithnullmice.IHCevaluationshowed amarkedincrease ina-SMA,CTGF, collagen I-III, TGF-b and Smad3 staining in the liver of Smad3 WTcompared with that in null mice, whereas Smad7 was increased only in nullmice.Conclusions: TheresultsindicatethatSmad3lossconfersresistancetothedevelopment of DMN-induced hepatic fibrosis. The reduced fibrotic responseappears to be due to a reduction of fibrogenic myofibroblast activation andECMproductionandaccumulation.Smad3couldbeanoveltargetforpotentialtreatment of fibrosis complicating chronic hepatitis.Liver fibrosis is a progressive and excessive accumulationof fibrillar extracellular matrix (ECM) proteins thatoccurs during chronic liver tissue damage. Fibrosis is acommon response to chronic liver diseases because ofinfective[mostly hepatitis C virus (HCV) and hepatitis Bvirus (HBV)], toxic/drug-induced, metabolic and auto-immunecauses(1–3).TheaccumulationofECMproteinderanges the hepatic architecture by forming a fibrousscar, and the subsequent development of nodules ofregenerating hepatocytes defines liver cirrhosis. Fibrosisis currently considered an abnormal wound-healingresponse to chronic liver injury. Fibrosis is a chronicand progressive process acting through complex cell/matrix/cytokine and growth factor interactions, but maybe a reversible event (1–7). The cellular and molecularmechanisms underlying wound healing and fibrosis stillremain to be fully elucidated.Physiological fibrogenesis is initiated by parenchymalcell destruction owing to multiple harmful agents andmechanisms, followed by inflammation, which, in turn,activates ‘resting’ ECM-producing cells to produce andsecrete ECM molecules, cytokines, chemokines, matrixmetalloproteinases (MMPs) and their specific inhibitors[tissue inhibitors of metalloproteinases (TIMPs)] (1–6,8, 9). Activated ECM-producing cells participate both infibrogenesis and in fibrinolysis (degradation of ECM),and thus in tissue remodelling. Fibrogenesis may leadeither to tissue repair or to fibrosis depending on thebalance between ECM synthesis and degradation (1–6,8, 9). After an acute liver injury, parenchymal cells

Intestinal fibrosis is a progressive process characterized by de novo synthesis and uncontrolled deposition of extracellular matrix components (ECM) following a tissue chronic inflammation mainly regulated by Transforming Growth Factor (TGF)β/ Smads pathway. Frequently associated to Inflammatory Bowel Disease (IBD), intestinal fibrosis may lead to stenosis and obstructions that require surgery up to 75% of patients as drugs currently used in IBD are unable to improve fibrostenosis lesions (1). Peroxisome proliferator-activated receptor (PPAR)-γ is able to antagonize (TGF) β/Smads and could be an crucial target to develop novel antifibrotic therapeutic strategies (2). Aim of this study is to evaluate the antifibrotic action of a novel PPARγ agonist, GED 0507-34 levo, in colonic fibrosis in mice. Immunohistochemistry and immunoblotting evaluations, TGFβ1, CTGF, Collagen types I-III, Smad3, α-SMA, were performed in in three groups of C57BL/6 mice: Dextran Sulphate Sodium (DSS) colitis group, DSS+GED group and controls. Evident macroscopic and microscopic lesions in the most of colons of DSS treated mice were observed compared to DSS+GED mice and controls. The tissue levels of the main markers of fibrosis resulted significantly increased in DSS mice and restored by administration of GED. GED seems to prevents ECM colonic deposition and to improve the intestinal fibrotic lesions by its ability in controlling TGFβ/Smads pathway signalling activation., Italian Journal of Anatomy and Embryology, Vol 119, No 1 (Supplement) 2014

Background Intestinal fibrosis is characterized by abnormal production and deposition of extracellular matrix (ECM) proteins by activated myofibroblasts. The main progenitor cells of activated myofibroblasts are the fibroblasts and the epithelial cells, the latter through the epithelial-mesenchymal transition (EMT). Aim To evaluate the action of the new PPAR-γ modulator, GED-0507-34 Levo (GED) on the expression of EMT associated and regulatory proteins such as TGF-β, Smad3, E-cadherin, Snail, ZEB1, β-catenin, and GSK-3β, in a mouse model of DSS-induced intestinal fibrosis. Methods Chronic colitis and fibrosis were induced by oral administration of 2.5% DSS (w/v) for 6 weeks. GW9662 (GW), a selective PPAR-γ inhibitor, was also administered by intraperitoneal injection at the dose of 1 mg/kg/day combined with GED treatment. All drugs were administered at the beginning of the second cycle of DSS (day 12). 65 mice were randomly divided into five groups (H2O as controls n = 10, H2O+GED n = 10, DSS n = 15, DSS+GED n = 15, DSS+GED+GW n = 15). The colon was excised for macroscopic examination and histological and morphometric analyses. The level of expression of molecules involved in EMT and fibrosis, like TGF-β, Smad3, E-cadherin, Snail, ZEB1, β-catenin, GSK-3β and PPAR-γ, was assessed by immunohistochemistry, immunofluorescence, western blot and Real Time PCR. Results GED improved the DSS-induced chronic colitis and fibrosis. GED was able to reduce the expression of the main fibrosis markers (α-SMA, collagen I-III and fibronectin) as well as the pivotal pro-fibrotic molecules IL-13, TGF-β and Smad3, while it increased the anti-fibrotic PPAR-γ. All these GED effects were nullified by co-administration of GW with GED. Furthermore, GED was able to normalize the expression levels of E-cadherin and β-catenin and upregulated GSK-3β, that are all known to be involved both in EMT and fibrosis. Conclusions The DSS-induced intestinal fibrosis was improved by the new PPAR-γ modulator GED-0507-34 Levo through the modulation of EMT mediators and pro-fibrotic molecules and through GSK-3β induction.

Background Transforming growth factor-β (TGF-β)/Smad3 signalling plays a central role in tissue fibrogenesis, acting as a potent stimulus of extracellular matrix (ECM) protein accumulation. The aim of this study was to evaluate the potential role of Smad3 in the pathogenesis of colonic fibrosis induced by trinitrobenzene sulfonic acid (TNBS) in Smad3 null mice. Materials and methods Chronic colitis-associated fibrosis was induced in 15 Smad3 null and 13 wild-type mice by intra-rectal administration of TNBS. Each mouse received an incremental dose of TNBS (0·5–1·0 mg per week) over a 6-week period. The colon was excised for macroscopic examination and histological, morphometric and immunohistochemical analyses. For immunohistochemistry, alpha-smooth muscle actin (α-SMA), collagen types I–III, TGF-β1, connective tissue growth factor (CTGF), Smad3, Smad7, and CD3 antibodies were used. Results At macroscopic examination, the colon of Smad3 wild-type mice appeared significantly harder, thicker and shorter than that of the Smad3 null mice. Of the wild-type mice, 50% presented colonic adhesions and strictures. Histological and morphometric evaluation revealed a significantly higher degree of colonic fibrosis and accumulation of collagen in the Smad3 wild-type compared to null mice, whereas the degree of colonic inflammation did not differ between the two groups of mice. Immunohistochemical evaluation showed a marked increase in CTGF, collagen I–III, TGF-β and Smad3 staining in the colon of Smad3 wild-type compared to null mice, whereas Smad7 was increased only in null mice. Conclusions These results indicate that Smad3 loss confers resistance to the development of TNBS-induced colonic fibrosis. The reduced fibrotic response appears to be due to a reduction in fibrogenic mesenchymal cell activation and ECM production and accumulation. Smad3 could be a novel target for potential treatment of intestinal fibrosis, especially in inflammatory bowel disease.

Background Currently, no effective preventive measures or medical therapies are available for intestinal fibrosis and, thus, surgery remains the only available strategy in the management of fibrostenotic enteropathies, especially Crohn's disease. The aim of this study was to evaluate the efficacy of a combined therapy of anti-inflammatory Boswellia and antifibrotic Scutellaria extracts on the development of colonic fibrosis in rats. Materials and methods Chronic colonic inflammation-associated fibrosis was induced in rats by intracolonic administration of 2,4,5-trinitrobenzene sulphonic acid (TNBS). Sixty-four healthy male Sprague-Dawley rats were assigned to five groups: 8 controls, 14 TNBS, 14 TNBS orally treated with Boswellia extracts (50 mg kg(-1) day(-1)), 14 TNBS orally treated with Scutellaria extracts (150 mg kg(-1) day(-1)), and 14 TNBS orally treated with both Boswellia (50 mg kg(-1) day(-1)) and Scutellaria extracts (150 mg kg(-1) day(-1)). The colon was removed after 21 days of treatment and assessed by macroscopic, histological, morphometric and immunohistochemical analyses. For immunohistochemical analysis, alpha-smooth muscle actin (alpha-SMA), collagen types I-III, connective tissue growth factor (CTGF), transforming growth factor-beta1 (TGF-beta1), Smad3, Smad7 and CD3 antibodies were used. Results Combined oral administration of Boswellia and Scutellaria significantly improved the course and macroscopic findings of TNBS-induced chronic colitis assessed by disease activity index, colon weight, length, adhesions, strictures, dilatation, thickness, oedema, ulcerations and extension of damage. The histological severity of the colonic fibrosis was also notably improved by the treatment and associated with a significant reduction in the colonic expression of alpha-SMA, collagen I-III, CTGF, TGF-beta1, Smad3, and Smad7. Conclusions These data demonstrate that the prophylactic administration of anti-inflammatory Boswellia and antifibrotic Scutellaria extracts is effective in preventing colonic fibrosis in TNBS-induced colitis. Their antifibrotic mechanism of action seems to be mediated by the inhibition of TGF-beta1/Smad3 pathway.

Background Transforming growth factor-β (TGF-β)/Smad's signalling pathway plays a pivotal role in organogenesis, oncogenesis, inflammation, repair and fibrosis. The aim of this study was to evaluate the morphology of muscle layers and the density and distribution of interstitial cells of Cajal (ICC) in the colon of Smad3 knockout mice. Materials and methods Eighteen Smad3 wild-type mice and 12 null mice were sacrificed at age 4 months and the colons were collected for histology (Haematoxilin-Eosin, Masson thrichrome and Gomori silver staining), morphometry and immunohistochemistry (IHC) analysis. For IHC we used the c-Kit, α-smooth muscle actine (α-SMA), vimentin, desmin and neuronal cocktail (S-100, NSE, neurofilament 200) antibodies. Results When sacrificed, 40% of the null mice showed different degrees of colon dilatation when compared with the wild-type. Histological and morphometric evaluation revealed a significant reduction in muscle layer thickness of the colon in all the null mice when compared with the wild-type. Immunohistochemistry evaluation showed a marked reduction, or even absence, of c-Kit immunoreactivity, which identifies ICC, in the colon of all the null mice, compared with the wild-type. Conclusions Smad3 null mice showed a marked reduction, or even absence, of ICC in the colon together with a concomitant reduction of intestinal smooth muscle layer thickness. This data could account for the colonic dilation observed in approximately 40% of the Smad3 null mice. Alteration of intestinal smooth muscle layers and ICC could also be involved in the resistance of the Smad3 null mice to develop colonic fibrosis.

AIM: To evaluate the possible differences in morphology and immunohistochemical expression of CD3, transforming growth factor β1(TGF-β1), Smad7, α-smooth muscle actin (α-Sma), and collagen types I-VII of small and large intestine in Smad3 null and wild-type mice. METHODS: Ten null and ten wild-type adult mice were sacrifi ced at 4 mo of age and the organs (esophagus, small and large bowel, ureters) were collected for histology(hematoxylin and eosin, Masson thrichrome, silver staining), morphometry and immunohistochemistry analysis. TGF-β1 levels of intestinal tissue homogenates were assessed by ELISA. RESULTS: No macroscopic intestinal lesions were detected both in null and wild-type mice. Histological and morphometric evaluation revealed a signifi cant reduction in muscle layer thickness of small and large intestine in null mice as compared to wild-type mice. Immunohistochemistry evaluation showed a signifi cant increase of CD3+T cell, TGF-β1 and Smad7 staining in the small and large intestine mucosa of Smad3 null mice as compared to wild-type mice. α-Sma and collagen I-VII staining of small and large intestine did not differ between the two groups of mice. TGF-β1 levels of colonic tissue homogenates were signifi cantly higher in null mice than in wildtype mice. In preliminary experiments a signifi cant reduction of TNBS-induced intestinal fi brosis was observed in null mice as compared to wild-type mice. CONCLUSION: Smad3 null mice are a useful model to investigate the in vivo role of the TGF-β/Smad signalling pathway in intestinal infl ammation and fi brosis.

Background Hepatocellular carcinoma (HCC) is the most common malignant tumor of the liver. Non-alcoholic fatty liver disease (NAFLD) is a frequent chronic liver disorder in developed countries. NAFLD can progress through the more severe non alcoholic steatohepatitis (NASH), cirrhosis and, lastly, HCC. Genetic and epigenetic alterations of coding genes as well as deregulation of microRNAs (miRNAs) activity play a role in HCC development. In this study, the C57BL/6J mouse model was long term high-fat (HF) or low-fat (LF) diet fed, in order to analyze molecular mechanisms responsible for the hepatic damage progression. Methods Mice were HF or LF diet fed for different time points, then plasma and hepatic tissues were collected. Histological and clinical chemistry assays were performed to assess the progression of liver disease. MicroRNAs’ differential expression was evaluated on pooled RNAs from tissues, and some miRNAs showing dysregulation were further analyzed at the individual level. Results Cholesterol, low and high density lipoproteins, triglycerides and alanine aminotransferase increase was detected in HF mice. Gross anatomical examination revealed hepatomegaly in HF livers, and histological analysis highlighted different degrees and levels of steatosis, inflammatory infiltrate and fibrosis in HF and LF animals, demonstrating the progression from NAFLD through NASH. Macroscopic nodules, showing typical neoplastic features, were observed in 20 % of HF diet fed mice. Fifteen miRNAs differentially expressed in HF with respect to LF hepatic tissues during the progression of liver damage, and in tumors with respect to HF non tumor liver specimens were identified. Among them, miR-340-5p, miR-484, miR-574-3p, miR-720, whose expression was never described in NAFLD, NASH and HCC tissues, and miR-125a-5p and miR-182, which showed early and significant dysregulation in the sequential hepatic damage process. Conclusions In this study, fifteen microRNAs which were modulated in hepatic tissues and in tumors during the transition NAFLD-NASH-HCC are reported. Besides some already described, new and early dysregulated miRNAs were identified. Functional analyses are needed to validate the results here obtained, and to better define the role of these molecules in the progression of the hepatic disease. Electronic supplementary material The online version of this article (doi:10.1186/s12885-015-2007-1) contains supplementary material, which is available to authorized users.

A simultaneous action of several pro-fibrotic mediators appears relevant in the development of fibrosis. There are evidences that transforming growth factor-β (TGF-β)/Smad3 pathway forms with αvβ6 integrin, mammalian target of Rapamycin (mTOR) and peroxisome proliferator-activated receptor-γ (PPARγ) a complex signalling network with extensive crosstalk and strong effects on fibrosis development. The present study evaluated the expression of TGFβ, Smad3, αvβ6 integrin, mTOR and PPARγ in 2, 4, 6-trinitrobenzenesulphonic acid (TNBS)-induced colorectal fibrosis in Smad3 wild-type (WT) and null mice. Smad3 WT mice treated with TNBS developed a marked colorectal fibrosis and showed a concomitant up-regulation of TGFβ, Smad3, αvβ6 and mTOR and a reduction of PPARγ expression. On the other hand, Smad3 Null mice similarly treated with TNBS did not develop fibrosis and showed a very low or even absent expression of TGFβ, Smad3, αvβ6 and mTOR and a marked over-expression of PPARγ. At the same time the expression of α-smooth muscle actin (a marker of activated myofibroblasts), collagen I-III and connective tissue growth factor (a downstream effector of TGFβ/Smad3-induced extracellular matrix proteins) were up-regulated in Smad3 WT mice treated with TNBS compared to Null TNBS-treated mice. These preliminary results suggest a possible interaction between these pro-fibrotic molecules in the development of intestinal fibrosis.