Animal models of inflammatory bowel disease

Serum albumin and body weight as biomarkers for the antemortem identification of bone and gastrointestinal disease in the common marmoset

The increasing use of the common marmoset (Callithrix jacchus) in research makes it important to diagnose spontaneous disease that may confound experimental studies. Bone disease and gastrointestinal disease are two major causes of morbidity and mortality in captive marmosets, but currently no effective antemortem tests are available to identify affected animals prior to the terminal stage of disease. In this study we propose that bone disease and gastrointestinal disease are associated disease entities in marmosets and aim to establish the efficacy of several economical antemortem tests in identifying and predicting disease. Tissues from marmosets were examined to define affected animals and unaffected controls. Complete blood count, serum chemistry values, body weight, quantitative radiographs, and tissue-specific biochemical markers were evaluated as candidate biomarkers for disease. Bone and gastrointestinal disease were associated, with marmosets being over seven times more likely to have either concurrent bone and gastrointestinal disease or neither disease as opposed to lesions in only one organ system. When used in tandem, serum albumin <3.5 g/dL and body weight <325 g identified 100% of the marmosets affected with concurrent bone and gastrointestinal disease. Progressive body weight loss of 0.05% of peak body weight per day predicted which marmosets would develop disease prior to the terminal stage. Bone tissue-specific tests, such as quantitative analysis of radiographs and serum parathyroid hormone levels, were effective for distinguishing between marmosets with bone disease and those without. These results provide an avenue for making informed decisions regarding the removal of affected marmosets from studies in a timely manner, preserving the integrity of research results.

A monoclonal antibody selection for immunohistochemical examination of lymphoid tissues from non-human primates

Non-human primates (NHPs) offer valuable animal models for basic research into human diseases and for the preclinical validation of new therapeutics. Detailed in situ examination of the involved cell types using immunohistochemistry is often hampered by the lack of cross-reactive antibodies (Abs). In the current study, we have tested a large panel of monoclonal antibodies raised against human leukocyte differentiation and activation markers for cross-reactivity on cryosections of lymphoid tissue from six NHP species. In total, we have tested 130 Abs against 69 antigens expressed in tissues from one great ape species (chimpanzee/Pan troglodytes), two Old World species (rhesus macaque/Macaca mulatta and cynomolgus macaque/Macaca fascicularis), and three New World species (common marmoset/Callithrix jacchus, cotton-top tamarin/Saguinus oedipus, and owl monkey/Aotus triviogatus). We have found a large panel of cross-reactive Abs: 93 of 102 (91%) in chimpanzee, 97 of 125 (78%) in rhesus macaque, 70 of 109 (64%) in cynomolgus macaque, 69 of 116 (60%) in common marmoset, 40 of 81 (49%) in cotton-top tamarin, and 35 of 80 (44%) in owl monkey. The availability of a reliable panel of cross-reactive markers is important to gaining further insight into immunological processes in disease-affected tissues from NHP species.

Inflammatory bowel disease: a model of chronic inflammation-induced cancer

Chronic inflammation is a well-recognized risk factor for the development of human cancer. Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, is a typical longstanding inflammatory disease of the colon with increased risk for the development of colorectal carcinoma. Several molecular events involved in chronic inflammatory process may contribute to multistage progression of human cancer development, including the overproduction of reactive oxygen and nitrogen species, overproduction/activation of key arachidonic acid metabolites and cytokines/growth factors, and immunity system dysfunction. Multiple animal models of IBD have been established, and in general, these models can be mainly categorized into chemically induced, genetically engineered (transgenic or gene knock-out), spontaneous, and adoptive transferring animal models. This chapter mainly focuses on (1) epidemiologic and molecular evidence on IBD and risk of colorectal cancer, (2) molecular pathogenesis of IBD-induced carcinogenesis, and (3) modeling of IBD-induced carcinogenesis in rodents and its application.

Human inflammatory bowel disease does not associate with Lawsonia intracellularis infection

BACKGROUND

There is increasing evidence that bacterial infection of the intestinal mucosa may contribute to the pathogenesis of inflammatory bowel diseases (IBD). In pigs, an obligate intracellular bacterium, Lawsonia intracellularis (LI), was shown to cause proliferative enteropathy (PE) of which some forms display histological and clinical similarities to human IBD. Since LI-similar Desulfovibrio spp. may infect human cells, we hypothesized that LI might be associated with the development of human IBD.

RESULTS

In human intestinal tissue samples, PCR using LLG, 50SL27, LSA and strictly LI-specific 16SII primers, yielded either no amplicons or products with weak homology to human genomic sequences. Sequencing of these amplicons revealed no specificity for LI. However, amplification of DNA with less specific 16SI primers resulted in products bearing homology to certain Streptococcus species. These 16SI-amplified products were present in healthy and diseased specimens, without obvious prevalence.

CONCLUSION

LI is not associated with the pathogenesis of UC or CD. Whether an immunologic response to commensal bacteria such as streptococci may contribute to the chronic inflammatory condition in IBD, remained to be determined.

Beta-Catenin mutations in a mouse model of inflammation-related colon carcinogenesis induced by 1,2-dimethylhydrazine and dextran sodium sulfate

In a previous study, we developed a novel mouse model for colitis-related carcinogenesis, utilizing a single dose of azoxymethane (AOM) followed by dextran sodium sulfate (DSS) in drinking water. In the present study, we investigated whether colonic neoplasms can be developed in mice initiated with a single injection of another genotoxic colonic carcinogen 1,2-dimethylhydrazine (DMH), instead of AOM and followed by exposure of DSS in drinking water. Male crj: CD-1 (ICR) mice were given a single intraperitoneal administration (10, 20 or 40 mg/kg body weight) of DMH and 1-week oral exposure (2% in drinking water) of a non-genotoxic carcinogen, DSS. All animals were killed at week 20, histological alterations and immunohistochemical expression of beta-catenin, cyclooxygenase (COX-2) and inducible nitric oxide synthase (iNOS) were examined in induced colonic epithelial lesions (colonic dysplasias and neoplasms). Also, the beta-catenin gene mutations in paraffin-embedded colonic adenocarcinomas were analyzed by the single strand conformation polymorphism method, restriction enzyme fragment length polymorphism and direct sequencing. The incidences of colonic neoplasms with dysplastic lesions developed were 100% with 2.29+/-0.95 multiplicity, and 100% with 10.38+/-4.00 multiplicity in mice given DMH at doses of 10 mg/kg or 20 mg/kg and 2%DSS, respectively. Although approximately half of the mice given DMH at a dose of 40 mg/kg bodyweight were dead after 2-3 days after the injection, mice who received DMH 40 mg/kg and 2%DSS had 100% incidence of colonic neoplasms with 9.75+/-6.29 multiplicity. Immunohistochemical investigation revealed that adnocarcinomas, induced by DMH at all doses and 2%DSS, showed positive reactivities against beta-catenin, COX-2 and iNOS. In DMH/DSS-induced adenocarcinomas, 10 of 11 (90.9%) adenocacrcinomas had beta-catenin gene mutations. Half of the mutations were detected at codon 37 or 41, encoding serine and threonine that are direct targets for phosphorylation by glycogen synthase kinase-3beta. The present results suggests that, as in the previously reported model (AOM/DSS) our experimental protocol, DMH initiation followed by DSS, may provide a novel and useful mouse model for investigating inflammation-related colon carcinogenesis and for identifying xenobiotics with modifying effects.

Epstein-Barr virus infection in colorectal neoplasms associated with inflammatory bowel disease: detection of the virus in lymphomas but not in adenocarcinomas

Epstein-Barr virus (EBV) is associated with several lymphoid and epithelial human malignancies. The latter include gastric adenocarcinomas, while sporadic colorectal adenocarcinomas (CRCs) have been reported to be EBV-negative. Recently, increased numbers of EBV-infected B lymphocytes have been detected in intestinal mucosal samples affected by ulcerative colitis (UC) and, to a lesser extent, Crohn's disease (CD). Both CRC and colorectal non-Hodgkin's lymphoma (NHL) are recognized complications of inflammatory bowel disease (IBD), but it is unclear to what extent EBV contributes to the development of these neoplasms. Seventeen cases of IBD-associated CRC and nine cases of IBD-associated colorectal NHL were therefore studied for the presence of EBV by in situ hybridization. EBV-positive cases were further studied for the expression of the EBV-encoded nuclear antigen (EBNA) 2 and the latent membrane protein (LMP) 1 of EBV by immunohistochemistry. Four out of seven cases of colorectal NHL associated with UC were shown to be EBV-positive. In addition, two of two colorectal NHLs developing in patients with CD were EBV-positive. Of the EBV-positive lymphomas, three displayed a pattern of EBV latent gene expression consistent with type I latency (EBNA2(-)/LMP1(-)), two a type II pattern (EBNA2(-)/LMP1(+)), and one a type III pattern (EBNA2(+)/LMP1(+)). These findings suggest that EBV infection is involved in the pathogenesis of a proportion of colorectal NHLs developing in IBD. Iatrogenic immunosuppression may contribute to the development of these lymphomas. By contrast, all 17 IBD-associated CRCs were EBV-negative, including a case of CRC occurring synchronously with an EBV-positive NHL. In conjunction with previous reports on sporadic CRCs, this suggests that EBV is not involved in the pathogenesis of CRC.

Colorectal neoplasia in ulcerative colitis-recent advances

It is recognized that ulcerative colitis (UC) predisposes to the development of colorectal adenocarcinoma (CRC), and the molecular pathway for this process differs from that for sporadic CRCs. However, several important details regarding the risk factors for and the molecular changes underlying UC-related colorectal carcinogenesis have only come to light lately. First, recent data suggest environmental factors related to long-standing inflammation contribute more to this increased cancer risk than an inherited susceptibility. Second, molecular changes that may represent the first steps in the development of neoplasia are being increasingly identified in non-dysplastic, colitic mucosa. Third, there is now good evidence suggesting that UC-related CRC may develop along more than one molecular pathway. These emerging data will hopefully contribute to attempts to prevent the development of UC-related CRC, e.g. through refining surveillance programmes. Details of the molecular heterogeneity of UC-related dysplasia and CRC may also help develop reliable tools for diagnosing the former and for predicting the behaviour of the latter. Finally, there is increasing awareness of non-epithelial colorectal malignancies which are associated with UC and may potentially increase in incidence with changes in the medical management of this inflammatory disease.

Immune ablation and hematopoietic stem cell rescue for severe autoimmune diseases (SADS)

In addition to our center (Northwestern University, Chicago), several institutions in the United States (Fred Hutchinson Cancer Center, University of California at Los Angeles, and Medical College of Wisconsin) and Europe are activating protocols to transplant patients with SADS. In this age of cost-effectiveness, it will be difficult to arrange third-party reimbursement for a hematopoietic stem cell transplant that may lead to medical charges of between $100,000 and $200,000. However, the cost of standard medical care for patients with SADS is not trivial. Dialysis for an SLE patient with renal failure costs $40,000 per year, while the medical resources required to care for a patient with progressive multiple sclerosis may exceed $35,000 per year. Unique BMT regimen-related toxicities may occur, including intracranial hemorrhage in the SLE or rheumatoid arthritis patient who has vasculitis; acute neurologic decompensation in patients with multiple sclerosis, especially if the conditioning regimen contains neurotoxic agents that cross a compromised blood-brain barrier; respiratory failure in patients with myasthenia gravis; and increased renal or pulmonary toxicity in patients with scleroderma and parenchymal fibrosis. Scleroderma-associated gastrointestinal dysmotility and bacterial overgrowth may also lead to greater fungal and bacterial infections [76]. BMT is currently considered appropriate therapy for patients with chronic-phase Chronic myelogenous leukemia (CML) and indolent lymphomas who otherwise have a relatively long life expectancy of 5 and 10 years, respectively. The roughly similar long survival but greater functional impairment of patients with SADS may justify consideration of immune ablation and hematopoietic stem cell rescue.