TGF-beta1 gene transfer to the mouse colon leads to intestinal fibrosis

Intestinal fibrosis in IBD--a dynamic, multifactorial process

Intestinal fibrosis is a common and potentially serious complication of IBD that results from the reaction of intestinal tissue to the damage inflicted by chronic inflammation. The traditional view that fibrosis is inevitable or irreversible in patients with IBD is progressively changing in light of improved understanding of the cellular and molecular mechanisms that underlie the pathogenesis of fibrosis in general, and, in particular, intestinal fibrosis. These mechanisms are complex and dynamic, and involve multiple cell types, interconnected cellular events and a large number of soluble factors. In addition, owing to a breakdown of the epithelial barrier during inflammation of the gut, luminal bacterial products induce an innate immune response, which is triggered by activation of immune and nonimmune cells alike. Comprehension of the mechanisms of intestinal fibrosis will create a conceptual and practical framework that could achieve the specific blockade of fibrogenic pathways, allow for the estimation of risk of fibrotic complications, permit the detection of early fibrotic changes and, eventually, enable the development of treatments customized to the type and stage of each patient's IBD.

Smad3 loss confers resistance to the development of trinitrobenzene sulfonic acid-induced colorectal fibrosis

BACKGROUND

Transforming growth factor-beta (TGF-beta)/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 (alpha-SMA), collagen types I-III, TGF-beta1, 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-beta 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.

Degeneration of the pericryptal myofibroblast sheath by proinflammatory cytokines in inflammatory bowel diseases

BACKGROUND & AIMS

Inflammatory bowel diseases (IBDs) are characterized by remodeling of the intestinal mucosa, which is associated with excessive cytokine release. Previous studies have shown that the epithelium in the crypt region of the mucosa in patients with Crohn's disease is susceptible to proinflammatory cytokines. We investigated whether the subepithelial myofibroblasts in this region were affected by these inflammatory conditions.

METHODS

Immunofluorescence and immunohistochemistry were performed on inflamed and uninflamed specimens from patients with IBD to detect alpha-smooth muscle actin (alphaSMA), desmin, and tenascin-C. The effects of the proinflammatory cytokines interleukin-1beta, tumor necrosis factor-alpha, and interferon-gamma were analyzed in human intestinal myofibroblast cultures by immunoblotting and apoptosis assays.

RESULTS

Immunofluorescence analysis revealed decreased levels of the extracellular matrix molecule tenascin-C in pericryptal sheaths and alphaSMA in the immediate vicinity of the crypts in the inflamed specimens, indicating that the myofibroblast pericryptal sheath is affected by proinflammatory cytokines. Although individual cytokines did not affect myofibroblast proliferation or survival, cytokine combinations triggered caspase-dependent apoptosis. alphaSMA levels were reduced significantly in cells exposed to cytokines, either alone or in combination, suggesting dedifferentiation of myofibroblasts. Proinflammatory cytokines did not affect tenascin-C expression, suggesting that the decrease observed in the inflamed mucosa resulted from myofibroblast apoptosis.

CONCLUSIONS

The subepithelial myofibroblasts of the epithelial sheath are disrupted in the intestinal mucosa of patients with IBD. A loss of myofibroblasts appears to result from the susceptibility of these cells to proinflammatory cytokines.

BMP-7 does not protect against bleomycin-induced lung or skin fibrosis

Bone morphogenic protein (BMP)-7 is a member of the BMP family which are structurally and functionally related, and part of the TGFβ super family of growth factors. BMP-7 has been reported to inhibit renal fibrosis and TGFβ1-induced epithelial-mesenchymal transition (EMT), in part through negative interactions with TGFβ1 induced Smad 2/3 activation. We utilized in vivo bleomycin-induced fibrosis models in the skin and lung to determine the potential therapeutic effect of BMP-7. We then determined the effect of BMP-7 on TGFβ1-induced EMT in lung epithelial cells and collagen production by human lung fibroblasts. We show that BMP-7 did not affect bleomycin-induced fibrosis in either the lung or skin in vivo; had no effect on expression of pro-fibrotic genes by human lung fibroblasts, either at rest or following exposure to TGFβ1; and did not modulate TGFβ1 -induced EMT in human lung epithelial cells. Taken together our data indicates that BMP-7 has no anti-fibrotic effect in lung or skin fibrosis either in vivo or in vitro. This suggests that the therapeutic options for BMP-7 may be confined to the renal compartment.

Transanal delivery of angiotensin converting enzyme inhibitor prevents colonic fibrosis in a mouse colitis model: development of a unique mode of treatment

BACKGROUND

We have previously shown that angiotensin converting enzyme-inhibitor (ACE-I) improved colonic inflammation and apoptosis in a dextran sodium sulfate (DSS)-induced colitis model. This study attempted to determine whether ACE-I could prevent the development of colonic fibrosis.

METHODS

Colitis was induced in C57BL/6 mice with 2.5% DSS water for 7 days, followed by 7 days without DSS (fibrosis development). Study groups: Control (naive or non-treated), DSS+Placebo (polyethylene glycol (PEG), and DSS+ACE-I (using enalaprilat and PEG which are not absorbed through intact mucosa). Placebo and ACE-I were delivered daily via transanal route. Colonic mucosal fibrosis and inflammation were evaluated based on histological findings and cytokine expression.

RESULTS

Transanal administration of ACE-I/PEG dose-dependently decreased the severity of fibrosis and pro-inflammatory cytokine expression. We next investigated if ACE-I acted on the TGF-beta/Smad signaling pathway as a mechanism of this anti-fibrosis action. Results showed a significant down-regulation of TGF-beta1 expression; as well, downstream signaling of the Smad family, known to mediate fibrosis, showed a decline in Smad 3 and 4 expression with ACE-I/PEG.

CONCLUSION

ACE-I/PEG is effective in preventing colonic fibrosis and pro-inflammatory cytokine expression in a DSS colitis model, most likely by down-regulating the TGF-beta signaling pathway. ACE-I/PEG may be a potential new option for treating inflammatory bowel disease.

Roles of TGF-β/CTGF in intestinal fibrosis

Intestinal fibrosis is a serious complication of many inflammatory bowel diseases and is mainly caused by excessive proliferation of intestinal mesenchymal cells and abnormal deposition of extracellular matrix (ECM). Transforming growth factor beta (TGF-β) plays a key role in the development of intestinal fibrosis. Connective tissue growth factor(CTGF) is the specific downstream mediator in many of the important fibroproliferative effects of TGF-β. TGF-β-induced CTGF expression is mediated through several signaling pathways. This paper reviewed the current knowledge about the formation mechanism of intestinal fibrosis and discussed roles of TGF-β/CTGF in this progression.

Intestinal fibrosis in inflammatory bowel disease: progress in basic and clinical science

PURPOSE OF REVIEW

Intestinal fibrosis is a potentially serious complication of inflammatory bowel disease and its pathophysiology is still unclear. This review will discuss recent developments relating to sources of fibroblasts in intestinal inflammation, mediators that modulate fibroblast activation and function, as well as new clinical, laboratory, endoscopic and radiological studies aimed at improving diagnosis and management of intestinal fibrosis in inflammatory bowel disease.

RECENT FINDINGS

The fibroblast remains the central cell responsible for intestinal fibrosis in inflammatory bowel disease and transforming growth factor-beta1 is still the most potent pro-fibrogenic cytokine. Novel mediators, however, are being identified that modulate fibroblast function, such as interleukin-13, interleukin-21, galectin-3, osteopontin, Wnt and toll-like receptor ligands, and anti-tumor necrosis factor-alpha agents. New fibroblast sources are being identified, such as fibrocytes, and new mechanisms of fibroblast generation, like epithelial- and endothelial-to-mesenchymal transition. Animal models of intestinal fibrosis are still few, but new ways to induce gut fibrosis are being explored. Serological markers indicating a clinically complicated course that includes intestinal fibrosis are promising and are being tested in adult and pediatric populations, particularly in Crohn's disease. Video capsule endoscopy, the Given Patency capsule, double balloon enteroscopy, and computed tomographic enteroscopy are some of the new modalities being developed to assess the risk and improve the diagnosis of intestinal fibrosis. Novel therapeutic approaches include endoscopic balloon dilatation with conventional and double balloon enteroscopy, and local injection of glucocorticoids and tumor necrosis factor-alpha blockers, showing partial but encouraging success.

SUMMARY

More studies are needed to improve knowledge of the pathophysiology of intestinal fibrosis if better preventive, diagnostic and therapeutic measures are to be expected in the near future.

Prevention of colonic fibrosis by Boswellia and Scutellaria extracts in rats with colitis induced by 2,4,5-trinitrobenzene sulphonic acid

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.

Protein kinase B/Akt activity is involved in renal TGF-beta1-driven epithelial-mesenchymal transition in vitro and in vivo

The molecular pathogenesis of diabetic nephropathy (DN), the leading cause of end-stage renal disease worldwide, is complex and not fully understood. Transforming growth factor-β (TGF-β1) plays a critical role in many fibrotic disorders, including DN. In this study, we report protein kinase B (PKB/Akt) activation as a downstream event contributing to the pathophysiology of DN. We investigated the potential of PKB/Akt to mediate the profibrotic bioactions of TGF-β1 in kidney. Treatment of normal rat kidney epithelial cells (NRK52E) with TGF-β1 resulted in activation of phosphatidylinositol 3-kinase (PI3K) and PKB/Akt as evidenced by increased Ser⁴⁷³ phosphorylation and GSK-3β phosphorylation. TGF-β1 also stimulated increased Smad3 phosphorylation in these cells, a response that was insensitive to inhibition of PI3K or PKB/Akt. NRK52E cells displayed a loss of zona occludins 1 and E-cadherin and a gain in vimentin and α-smooth muscle actin expression, consistent with the fibrotic actions of TGF-β1. These effects were blocked with inhibitors of PI3K and PKB/Akt. Furthermore, overexpression of PTEN, the lipid phosphatase regulator of PKB/Akt activation, inhibited TGF-β1-induced PKB/Akt activation. Interestingly, in the Goto-Kakizaki rat model of type 2 diabetes, we also detected increased phosphorylation of PKB/Akt and its downstream target, GSK-3β, in the tubules, relative to that in control Wistar rats. Elevated Smad3 phosphorylation was also detected in kidney extracts from Goto-Kakizaki rats with chronic diabetes. Together, these data suggest that TGF-β1-mediated PKB/Akt activation may be important in renal fibrosis during diabetic nephropathy.

Chronic enteric salmonella infection in mice leads to severe and persistent intestinal fibrosis

BACKGROUND & AIMS

Intestinal fibrosis and stricture formation are serious complications of Crohn's disease, often requiring surgical intervention. Unfortunately, the mechanisms underlying intestinal fibrosis development are poorly understood, in part because of the lack of relevant animal models. Here, we present a novel murine model of severe and persistent intestinal fibrosis caused by chronic bacterial-induced colitis.

METHODS

Mice were treated with streptomycin 24 hours prior to oral infection with Salmonella enterica serovar Typhimurium. Tissues were analyzed for bacterial colonization and inflammation, and fibrosis was assessed by Masson's trichrome staining and collagen quantification. Expression of the profibrotic cytokines transforming growth factor-beta1, connective tissue growth factor and insulin-like growth factor-I was determined, and the cell types present in fibrotic tissues were assessed by immunohistochemistry.

RESULTS

Infection led to chronic Salmonella colonization of the cecum and colon followed by edema, mucosal ulcerations, and severe transmural inflammation. This pathology was accompanied by significantly elevated expression of transforming growth factor-beta1, connective tissue growth factor, and insulin-like growth factor-I along with extensive type I collagen deposition in the cecal mucosa, submucosa, and muscularis mucosa of infected mice. Fibrosis was evident by 7 days postinfection, peaking at day 21 and still present at day 70. The fibrotic regions were found to be rich in fibroblasts and myofibroblasts.

CONCLUSIONS

These data demonstrate that chronic Salmonella infection of the murine gastrointestinal tract leads to severe tissue fibrosis. Because this model is highly reproducible and easy to perform, it provides great potential for investigating both host and bacterial contributions to intestinal fibrosis.

Contrasting effects of pseudoephedrine and papaverine in dextran sodium sulfate-induced colitis

BACKGROUND

Dextran sodium sulfate (DSS) induces submucosal arteriolar constriction that reduces blood flow to the intestine, and the relevance of this decrease in flow needs further investigation. In the present study we examined the effects of a vasoconstrictor (pseudoephedrine) and a vasodilator (papaverine) on the outcome of DSS-induced colitis.

METHODS

Mice were given DSS in drinking water for 6 days, with enemas on days 0, 1, 3, and 5 containing pseudoephedrine, papaverine, or no drug. At the conclusion of the 6-day protocol a disease activity index comprising weight loss, stool consistency, and rectal bleeding was evaluated, along with intravital microscopy observations of submucosal venular leukocyte and platelet adherence in the proximal colon and terminal ileum.

RESULTS

Pseudoephedrine and papaverine had several contrasting effects on the outcome of DSS ingestion: pseudoephedrine induced the highest levels of weight loss, loose stools, venular platelet adherence, and overall disease activity index, while papaverine induced the highest levels of venular leukocyte adherence, but the lowest levels of rectal bleeding, loose stools, and overall disease activity index.

CONCLUSIONS

The results suggest that vasoconstriction worsens the pathological consequences of DSS in the mouse model of colitis.

The immunobiology of systemic sclerosis

OBJECTIVES

Systemic sclerosis (SSc) is a chronic connective tissue disease characterized by vascular damage, autoimmunity, and excessive collagen deposition. Despite advances in disease-specific treatment of other rheumatologic diseases, disease-targeted treatment in SSc continues to be elusive. In this review, our goal was to place the contemporary immunobiology of SSc in the perspective of clinical medicine.

METHODS

We performed a PubMed search for the period from 1989 to 2007, using the keyword, "systemic sclerosis," resulting in a total of 9099 publications, including 1252 reviews. Articles were then selected based on their discussion of recent advances in the elusive pathogenesis of SSc. A final total of 259 articles were chosen for the review.

RESULTS

The SSc hallmarks of vascular damage, immunologic activation, and collagen deposition can be traced to 4 major factors: T-cells, fibroblasts, B-cells, and cytokines/chemokines. T-cells are a major component of the infiltrate in skin and lung, exhibiting increased expression of activation markers and showing signs of antigen-driven expansion. Preliminary data indicate that induction of oral tolerance with collagen, a target of SSc T-cell responses, is associated with clinical benefits. Although this suggests that T-cells participate in the pathogenesis of SSc, their precise role and antigen specificity largely remain to be elucidated. Defective numbers and functions of certain T-cell subsets, such as natural killer and gammadelta T-cells, may be involved in the failure to maintain tolerance. Other data suggest that gammadelta T-cells may themselves be effector cells in endothelial cell cytotoxicity. There are several lines of evidence for a pathogenic role of B-cells in SSc, in particular, through the production of autoantibodies. Antibody-dependent cell-mediated cytotoxicity is a primary pathogenic event in an animal model of SSc and is likely to be involved in human SSc. Nonetheless, there is as yet no convincing evidence for the pathogenicity of SSc-specific antibodies. SSc fibroblasts exhibit a specific phenotype characterized not only by excessive collagen production but also by increased responsiveness to and production of cytokines and chemokines. This phenotype is induced by a complex network of cytokines and chemokines but appears to be maintained in the absence of exogenous stimuli via the autocrine production of some of these factors by SSc fibroblasts themselves, particularly transforming growth factor, platelet-derived growth factor, monocyte chemoattractant protein 1, and interleukin-1.

CONCLUSIONS

Significant variations in laboratory data among patients suggest that the pathology reflects a heterogeneous disease. Nonetheless, the possibility of achieving clinical benefits by inducing oral tolerance highlights the importance of characterizing SSc T-cell antigens. It is hoped that the identification of some of the key players in the induction and maintenance of the SSc fibroblast phenotype may yield new disease-targeted treatment regimens for patients with SSc.

Genetic susceptibility to late normal tissue injury

The outcome of all cancer therapies, including radiation, has greatly improved in the last 25 years, resulting in a doubling of the number of long-term cancer survivors. However, a subset of these survivors incurs adverse chronic side effects in unavoidably irradiated normal tissues, persisting long after treatment and compromising the quality of life of these patients. Interpatient variability in normal tissue radiation response is well documented and suggested to be under genetic control. Fibrosis, a clinically significant late effect in many irradiated tissues that results in tissue remodeling and loss of function, is a complex genetic trait making identification of the underlying genes difficult. Current clinical and animal studies are providing information on the genetics and molecular basis of late normal tissue injury in the radiation therapy setting, bringing us closer to our dual goal of individualizing treatment by genetic profiling and improving the quality of life of long-term survivors.

[Fibrogenesis and inflammatory bowel disease]

A substantial proportion of patients with Crohn's disease develops intestinal stenosis due to anomalous fiber deposits. These patients frequently require resection of the affected segment. Despite its evident clinical significance, intestinal fibrogenesis has received little attention in comparison with research into hepatic, pulmonary, renal or cutaneous fibrosis. There seems to be a certain genetic predisposition to developing intestinal fibrosis. A meta-analysis has demonstrated that the three main variants of the NOD2/CARD15 gene are associated with this complication. In Crohn's disease, a series of alterations in collagen synthesis, expression of various pro- and anti-fibrogenic factors and intestinal fibroblast function have been described in the last few years. More recently, the development of intestinal fibrosis has been attenuated in several experimental models. Nevertheless, further studies are required to improve our understanding of intestinal fibrogenesis and to develop effective strategies for its prevention and treatment.

IDENTIFICATION OF LIGANDS BINDING SPECIFICALLY TO INFLAMMATORY INTESTINAL MUCOSA USING PHAGE DISPLAY

1. Even though current treatments for inflammatory bowel disease are effective, adverse reactions remain a problem. With the intention of developing a new drug delivery system, we attempted to identify molecules that are selectively adsorbed to inflamed bowel. 2. The PhD-C7C phage display peptide library was used for biopanning against mouse isolated bowel, either untreated (control) or with inflammation caused by ischaemia-reperfusion injury. One hundred clones were selected from among those obtained by two biopanning procedures and the amino acid sequences of these clones were identified by determination of the base sequences. 3. Then, 20 clones were selected by an alignment process, after which the three clones with the highest affinity for inflammatory bowel were identified. One of these three clones had significantly higher affinity for inflammatory bowel than for normal bowel. 4. In conclusion, biopanning against isolated bowel samples identified an amino acid sequence (SQSHPRH) with a specific high affinity for inflammatory bowel.

Fibrogenesis in Crohn's disease

INTRODUCTION

Over one-third of patients with Crohn's disease (CD) will develop an intestinal stricture and the great majority of these will require at least one surgical procedure. While the pathogenesis of inflammation in CD has been extensively investigated, knowledge of stricture pathogenesis remains limited. The aim of this review is to discuss the current understanding of fibrogenesis in CD and to outline potential directions in research and therapeutics.

METHODS

The electronic literature (January 1966 to May 2006) on CD-associated fibrosis was reviewed. Further references were obtained by cross-referencing from key articles.

RESULTS

CD-associated fibrosis results from chronic transmural inflammation and a complex interplay among intestinal mesenchymal cells, cytokines, and local inflammatory cells. The fibroblast is the key cell type mediating stricture formation. The cytoarchitecure of the bowel wall is altered with disruption of the muscularis mucosa, thickening of the muscularis propria, and deposition of collagen throughout. The cytokine TGF-beta appears critical in this process, acting to increase growth factor and extracellular matrix (ECM) production and dysregulate ECM turnover. Potential therapeutic interventions are likely to concentrate on modulating down-stream targets of TGF-beta.

CONCLUSIONS

Greater understanding of the biology of fibrostenosis is likely to yield significant advances in our ability to care for patients with stricturing CD. Potential dividends of this approach include identification of novel therapeutic targets and biomarkers useful for prognostication and therapeutic monitoring.

IL-4 gene transfer to the small bowel serosa leads to intestinal inflammation and smooth muscle hyperresponsiveness

Intestinal mucosal inflammation can lead to altered function of the underlying smooth muscle, which becomes hyperreactive to most contractile stimuli. Through nematode parasite infection models, T helper type 2 (Th2) cytokines have been implicated in intestinal muscle dysfunction; however, the mechanisms involved and the relevance of these findings to other forms of intestinal inflammation are unclear. Through gene transfer, we explored whether the Th2 cytokine IL-4 can mediate changes in longitudinal muscle function in the context of an adenoviral infection. Following abdominal surgery on mice, control beta-galactosidase-encoding recombinant adenoviruses and IL-4-encoding adenoviruses were applied to the serosal surface of the jejunum, leading to infection of cells in the serosa and in the mesentery. Marker transgene expression lasted for 3 wk and was accompanied by the recruitment of macrophages, lymphocytes, and neutrophils into the peritoneal cavity and mild inflammation at the site of infection. IL-4 transgene expression led to a stronger inflammatory response characterized by tissue eosinophilia and increased numbers of peritoneal mast cells and plasma cells. Whereas control virus infection had no effect on intestinal muscle function, infection with the IL-4 virus led to significant jejunal muscle hypercontractility, evident by day 7 postinfection. This modulation of smooth muscle function was shown to be IL-4 specific, since the application of an IL-5-encoding adenovirus induced tissue eosinophilia but did not alter muscle function. These results highlight an important causal role for IL-4 in the pathological regulation of enteric smooth muscle function and identify a novel strategy for gene transfer to the intestine.

Forced expression of PDX-1 induces insulin production in intestinal epithelia

BACKGROUND

In the developmental stage, pancreas derives from the endodermal cells where the transcription factor, pancreatic duodenal homeobox gene-1 (pdx-1) is expressed. In adulthood, pdx-1 expression is localized to pancreatic beta cells, which is necessary for maintenance of beta cell function. Recently, ectopic expression of pdx-1 in the liver successfully induced insulin production and ameliorated hyperglycemia. Our study was designed to investigate the effects of forced expression of pdx-1 in ileal epithelia by adenovirus-mediated gene transfer.

METHODS

The recombinant, replication-deficient adenovirus carrying the pdx-1 gene was constructed using the COS-TPC method. ICR mice were treated with intraperitoneal injection of 220 mg/kg streptozotocin (STZ). After determining the hyperglycemia, a loop of ileum was constructed and the adenovirus solutions (Ad-pdx-1 and Ad-lacZ 1 x 10(8) PFU/body) were injected into the lumen of the ileal loop. In this model, immunohistochemical or fluorescent analyses of PDX-1 and insulin in the adenovirus-infected ileal epithelia were carried out. Reverse transcription polymerase chain reaction of pdx-1 and other pancreatic markers were investigated. Blood glucose concentrations were measured by drawing blood from ocular veins. Immunoreactive insulin extracted from the adenovirus-infected ileum was measured.

RESULTS

Ad-pdx-1 induced ectopic PDX-1 expression in the ileum. The PDX-1 positive cells in the ileal epithelia were positive for insulin; mRNA of insulin-1, insulin-2 and pdx-1 were expressed in mice infected with Ad-pdx-1. Hyperglycemia was improved in STZ-treated mice infected with Ad-pdx-1. Immunoreactive insulin in the ileum extract was increased significantly in mice with Ad-pdx-1.

CONCLUSIONS

Gene transfer of PDX-1 in intestinal epithelia could be a promising strategy for diabetes mellitus by inducing ectopic insulin producing cells.

Fibrosis in heart disease: understanding the role of transforming growth factor-beta in cardiomyopathy, valvular disease and arrhythmia

The importance of fibrosis in organ pathology and dysfunction appears to be increasingly relevant to a variety of distinct diseases. In particular, a number of different cardiac pathologies seem to be caused by a common fibrotic process. Within the heart, this fibrosis is thought to be partially mediated by transforming growth factor-beta1 (TGF-beta1), a potent stimulator of collagen-producing cardiac fibroblasts. Previously, TGF-beta1 had been implicated solely as a modulator of the myocardial remodelling seen after infarction. However, recent studies indicate that dilated, ischaemic and hypertrophic cardiomyopathies are all associated with raised levels of TGF-beta1. In fact, the pathogenic effects of TGF-beta1 have now been suggested to play a major role in valvular disease and arrhythmia, particularly atrial fibrillation. Thus far, medical therapy targeting TGF-beta1 has shown promise in a multitude of heart diseases. These therapies provide great hope, not only for treatment of symptoms but also for prevention of cardiac pathology as well. As is stated in the introduction, most reviews have focused on the effects of cytokines in remodelling after myocardial infarction. This article attempts to underline the significance of TGF-beta1 not only in the post-ischaemic setting, but also in dilated and hypertrophic cardiomyopathies, valvular diseases and arrhythmias (focusing on atrial fibrillation). It also aims to show that TGF-beta1 is an appropriate target for therapy in a variety of cardiovascular diseases.