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Crohn’s disease (CD) is an inflammatory bowel disease characterized by transmural inflammation and intestinal fibrosis. Mechanisms of fibrosis in CD are not well understood. Transmural inflammation is associated with inflammatory cell infiltration, stenosis, and distention, which present mechanical stress (MS) to the bowel wall. We hypothesize that MS induces gene expression of profibrotic mediators such as connective tissue growth factor (CTGF), which may contribute to fibrosis in CD. A rodent model of CD was induced by intracolonic instillation of TNBS to the distal colon. TNBS instillation induced a localized transmural inflammation (site I), with a distended colon segment (site P) proximal to site I. We detected significant fibrosis and collagen content not only in site I but also in site P in CD rats by day 7. CTGF expression increased significantly in sites P and I, but not in the segment distal to the inflammation site. Increased CTGF expression was detected mainly in the smooth muscle cells (SMCs). When rats were fed exclusively with clear liquid diet to prevent mechanical distention in colitis, expression of CTGF in sites P and I was blocked. Direct stretch led to robust expression of CTGF in colonic SMC. Treatment of CD rats with anti-CTGF antibody FG-3149 reduced fibrosis and collagen content in both sites P and I and exhibited consistent trends toward normalizing expression of collagen mRNAs. In conclusion, our studies suggest that mechanical stress, by upregulating profibrotic mediators, i.e., CTGF, may play a critical role in fibrosis in CD. [ABSTRACT FROM AUTHOR]

ObjectiveTo investigate the potential role of mucosal intestinal myofibroblasts (IMFs) in HIV and associated fibrosis in gut-associated lymphoid tissue.DesignProfibrotic changes within the secondary lymphoid organs and mucosa have been implicated in failed immune reconstitution following effective combination antiretroviral therapy (cART). Microbial translocation is believed to be sustaining these systemic inflammatory pathways. IMFs are nonprofessional antigen-presenting cells with both immunoregulatory and mesenchymal functions that are ideally positioned to respond to translocating microbial antigen.MethodsDuodenal biopsies, obtained from patients naive to cART, underwent trichrome staining and were examined for tissue growth factor-beta (TGF-β) expression. Combined immunostaining and second harmonic generation analysis were used to determine IMF activation and collagen deposition. Confocal microscopy was performed to examine IMF activation and Toll-like receptor (TLR)4 expression. Finally, primary IMF cultures were stimulated with lipopolysaccharide to demonstrate the expression of the inflammatory biomarkers.ResultsThe expression of the fibrosis-promoting molecule, TGF-β1, is significantly increased in duodenal biopsies from HIV patients naïve to cART, and negatively correlated with subsequent peripheral CD4(+) recovery. The increase in TGF-β1 coincided with an increase in collagen deposition in the duodenal mucosa in the tissue area adjacent to the IMFs. We also observed that IMFs expressed TLR4 and had an activated phenotype since they were positive for fibroblast activation protein. Finally, stimulation of IMFs from HIV patients with TLR4 resulted in significantly increased expression of profibrotic molecules, TGF-β1, and interleukin-6.ConclusionOur data support the hypothesis that activated IMFs may be among the major cells contributing to the profibrotic changes, and thus, the establishment and maintenance of systemic inflammation interfering with immune reconstitution in HIV patients.

Background: Previous studies implicated matrix metalloproteinases (MMPs), such as MMP-7, in inflammatory bowel diseases (IBD) by showing increased activity during inflammation of the gut. However, the pathophysiological roles of MMP-7 have not been clearly elucidated. Methods: The expression of MMP-7 was assessed in colonic biopsies of patients with ulcerative colitis (UC), in rodents with experimental colitis, and in cell-based assays with cytokines. Wild-type and MMP-7-null mice treated with dextran sulfate sodium (DSS) or trinitrobenzene sulfonic acid were used for determining the pro-inflammatory function(s) of MMP-7 in vivo. Results: MMP-7 was highly expressed in patients with UC and in rodents with experimental colitis. IL-1β, IL-4, IL-13, TNFα, or lipopolysaccharide enhanced MMP-7 expression in human colonic epithelial cells, rat colonic smooth muscle cells, and THP-1-derived macrophages. Active MMP-7 degraded tight junction protein Claudin-7 in epithelial cells, cleaved recombinant Claudin-7 in cell-free system, and increased Caco-2 monolayer permeability. Immunostaining of colon biopsies revealed up-regulation of MMP-7 and reduction of Claudin-7 in UC patients. Compared to wild-type mice, Mmp7-/- mice had significantly less inflammation in the colon upon DSS insult. DSS-induced alterations in junction proteins were mitigated in Mmp7-/- mice, suggesting that MMP-7 disrupts the intestinal barrier. MMP-7 antibody significantly ameliorated colonic inflammation and Claudin-7 reduction in 2 different rodent models of colitis. Summary: MMP-7 impairs intestinal epithelial barrier by cleavage of Claudin-7, and thus aggravating inflammation. These studies uncovered Claudin-7 as a novel substrate of MMP-7 in the intestinal epithelium and reinforced MMP-7 as a potential therapeutic target for IBD. [ABSTRACT FROM AUTHOR]

Elevated mucosal interleukin-1 (IL-1) levels are frequently seen during acute and chronic intestinal inflammation, and IL-1 neutralization lessens the severity of inflammation. One major effect of IL-1 is the increased release of eicosanoid mediators via induction of cyclooxygenase-2 (COX-2). One site of COX-2-derived prostaglandin synthesis during acute and chronic intestinal inflammation is the intestinal myofibroblast. COX-2 expression has also been documented in these cells in colonic neoplasms. Thus an understanding of the regulation of COX-2 expression in human intestinal myofibroblasts is important. As an initial step toward this goal we have characterized IL-1[alpha], signaling pathways that induce COX-2 expression in cultured human intestinal myofibroblasts. IL-1 treatment resulted in a dramatic transcriptional induction of COX-2 gene expression. Activation of nuclear factor-[Kappa]B (NF-[Kappa]B), extracellular signal-regulated protein kinase (ERK), p38, and protein kinase C (PKC) signaling pathways was each necessary for optimal COX-2 induction. In contrast to what occurs in other cell types, including other myofibroblasts such as renal mesangial cells, PKC inhibition did not prevent IL-1-induced NF-[Kappa]B or mitogen activated protein kinase/stress-activated protein kinase activation, suggesting a novel role for PKC isoforms during this process. The stimulatory effects of PKC, NF-[Kappa]B, ERK-1/2, and presumably c-Jun N[H.sub.2]-terminal kinase activation were exerted at the transcriptional level, whereas p38 activation resulted in increased stability of the COX-2 message. We conclude that, in intestinal myofibroblasts, IL-1-mediated induction of COX-2 expression is a complex process that requires input from multiple signaling pathways. Each parallel pathway acts in relative autonomy, the sum of their actions culminating in a dramatic increase in COX-2 transcription and message stability. prostaglandins; eicosanoids; intestinal inflammation; intestinal carcinogenesis; stromal cells; epithelial-mesenchymal interactions

The biological functions of intestinal subepithelial myofibroblasts (ISEMF) and their role in intestinal physiology were analyzed in 18Co cells lines derived from human neonatal colonic mucosa. The 18Co cells exhibited similar biochemical and morphological functions compared to ISEMF. The human colonic cell line was also composed of bundles of cytoplasmic microfilaments with associated dense bodies and large numbers of subplasma membrane caveolae. Furthermore, 18Co cell exhibited a transition from discoid to stellate morphology and expressed the smooth muscle isoform of alpha-actin.

The secretagogue-stimulated Cl- transport activity of T84 colonocytes are enhanced by the interleukin-1alpha (IL-1alpha)-induced stimulation of the subepithelial myofibroblasts (SEMF) colonic and jejunal cell lines. Enhanced cyclooxygenase gene expression initiate the action of IL-1alpha-activated neurotransmitter and inflammatory mediators. Furthermore, IL-1alpha utilizes Ca2+ to activate the mediators that sensitizes Cl- secretion in enterocytes and stimulate the production of prostaglandin E2.

The number of gastroenterologists in the US could exceed the demand if current training programs proceed unchecked. The number of gastroenterologists rose 500% between 1974 and 1994 and in 1992, the number of gastroenterologists was 3.1 per 100,000 people. Over 1,100 gastroenterologists were enrolled in training programs in 1993. The American Gastroenterological Association believes the US will need 9,000 to 10,000 gastroenterologists and this could be achieved even with reductions in training programs. The Gastroenterology Leadership Council recommends cutting programs by 50% over the next 5 years., Objective.--To examine the current supply and distribution of gastroenterologists and project future supply under various scenarios to provide a paradigm for workforce reform. Design.--An analysis of current practices and distribution of gastroenterologists and a demographic model, using the 1992 gastroenterology workforce as a baseline. Main Outcome Measure.--Comparison of current supply, distribution, and practice profiles with past data and future projections, using analyses of data from the 1993 Area Resource File, 1992 Medicare Part B file, age- and sex-specific death and retirement rates from the Bureau of Health Professions, managed care staffing patterns, the National Survey of Internal Medicine Manpower, and the Bureau of the Census. Results.--Rapid growth in the number of US gastroenterologists has resulted in a gastroenterologist-to-population ratio double that used on average by health maintenance organizations. In addition, the work profile of gastroenterologists is shared significantly by primary care physicians and other specialists, with the exception of a few specific and uncommon procedures. Conclusions.--Empirical evidence suggests that, even in the absence of detailed models to describe the desired supply/need balance for gastroenterology, the US health care system and clinicians may benefit from a reduction in gastroenterology training programs. The Gastroenterology Leadership Council endorsed a goal of 25% to 50% reduction in trainee numbers over 5 years, and recent National Resident Matching Program data indicate that a voluntary downsizing process is in full force. This study illustrates a paradigm for workforce planning that could be useful for other medical specialties. JAMA. 1996;276:689-694