Showing papers by "Matthew B. Grisham published in 2015"

Use of Humanized Mice to Study the Pathogenesis of Autoimmune and Inflammatory Diseases

Abstract: Animal models of disease have been used extensively by the research community for the past several decades to better understand the pathogenesis of different diseases and assess the efficacy and toxicity of different therapeutic agents. Retrospective analyses of numerous preclinical intervention studies using mouse models of acute and chronic inflammatory diseases reveal a generalized failure to translate promising interventions or therapeutics into clinically effective treatments in patients. Although several possible reasons have been suggested to account for this generalized failure to translate therapeutic efficacy from the laboratory bench to the patient's bedside, it is becoming increasingly apparent that the mouse immune system is substantially different from the human. Indeed, it is well known that >80 major differences exist between mouse and human immunology; all of which contribute to significant differences in immune system development, activation, and responses to challenges in innate and adaptive immunity. This inconvenient reality has prompted investigators to attempt to humanize the mouse immune system to address important human-specific questions that are impossible to study in patients. The successful long-term engraftment of human hematolymphoid cells in mice would provide investigators with a relatively inexpensive small animal model to study clinically relevant mechanisms and facilitate the evaluation of human-specific therapies in vivo. The discovery that targeted mutation of the IL-2 receptor common gamma chain in lymphopenic mice allows for the long-term engraftment of functional human immune cells has advanced greatly our ability to humanize the mouse immune system. The objective of this review is to present a brief overview of the recent advances that have been made in the development and use of humanized mice with special emphasis on autoimmune and chronic inflammatory diseases. In addition, we discuss the use of these unique mouse models to define the human-specific immunopathological mechanisms responsible for the induction and perpetuation of chronic gut inflammation.

Application of Comparative Transcriptional Genomics to Identify Molecular Targets for Pediatric IBD

Abstract: Experimental models of colitis in mice have been used extensively for analyzing the molecular events that occur during inflammatory bowel disease (IBD) development. However, it is uncertain to what extent the experimental models reproduce features of human IBD. This is largely due to the lack of precise methods for direct and comprehensive comparison of mouse and human inflamed colon tissue at the molecular level. Here we use global gene expression patterns of two sets of pediatric IBD and two mouse models of colitis to obtain a direct comparison of the genome signatures of mouse and human IBD. By comparing the two sets of pediatric IBD microarray data, we found 83 genes were differentially expressed in a similar manner between pediatric Crohn’s disease (CD) and ulcerative colitis (UC). Up regulation of the chemokine (C-C motif) ligand 2 (CCL2) gene that maps to 17q12, a confirmed IBD susceptibility loci, indicates that our comparison study can reveal known genetic associations with IBD. In comparing pediatric IBD and experimental colitis microarray data, we found common signatures amongst them including: 1) up regulation of CXCL9 and S100A8; 2) cytokine-cytokine receptor pathway dysregulation; and 3) over-represented IRF1 and IRF2 transcription binding sites in the promoter region of up regulated genes, and HNF1A and Lhx3 binding sites were over-represented in the promoter region of the down regulated genes. In summary, this study provides a comprehensive view of transcriptome changes between different pediatric IBD populations in comparison with different colitis models. These findings reveal several new molecular targets for further study in the regulation of colitis.

Abstract 1557: The iron-overload genetic disease hemochromatosis potentiates colonic inflammation and colon carcinogenesis

Abstract: Hemochromatosis is a highly prevalent genetic disease associated with excessive iron accumulation in a variety of tissues in an age-dependent manner. In a majority of patients (>85%) with hemochromatosis, mutations in the iron-regulatory gene HFE are the cause. Iron, when present in excess, is an inducer of oxidative stress and suppresses mitochondrial function. Patients with hemochromatosis show evidence of colonic inflammation. Further, some studies have shown increased risk for colon cancer associated with genetic mutations known to cause hemochromatosis. Based on these findings in the literature, we hypothesized that hemochromatosis is an important determinant of disease progression in patients with colitis and colon cancer. We tested this hypothesis by comparing progression of experimentally induced colitis and colon cancer between wild type mice and Hfe-null mice, a model for hemochromatosis. We also compared the transcriptome profile between wild type and Hfe-null colonic epithelial cells. In addition, we analyzed fecal bacteria in wild type mice and Hfe-null mice because colonic microbiome is an important determinant of colonic inflammation and colon cancer. With dextran sulfate sodium-induced colitis, Hfe-null mice suffered more weight loss and exhibited more severe bleeding and diarrhea scores than wild type mice. With ApcMin-driven colon and intestinal cancer, Hfe-null mice had more polyps in the small intestine and colon than wild type mice. Transcriptome analysis showed that Hfe-null colonic epithelial cells, compared to wild type cells, had increased expression of the cytokines Ccl3 and Ccl5 and the interferon-stimulated gene 15 (ISG15 or Usp18), which are all known to promote inflammation and cancer. Hfe-null colonic epithelial cells also had decreased expression of Erdr1 (erythroid differentiation regulator 1), whose expression is known to suppress tumor cell proliferation, invasion, migration and metastasis. Analysis of fecal microbiome indicated that the prevalence of Bacteroidetes and Firmicutes decreased while that of Proteobacteria increased in Hfe-null mice compared to wild type mice, a finding particularly striking in male mice. These studies demonstrate that hemochromatosis enhances the progression of colonic inflammation and colon carcinogenesis. This conclusion is further supported by xenograft studies using the colon cancer cell line HCT116 with and without shRNA-induced downregulation of HFE. When HFE was silenced, there was a significant increase in the growth of HCT116 cells in mouse xenografts, demonstrating that inactivation of HFE promotes colon cancer progression. Based on these data, we conclude that the iron-overload disease hemochromatosis is a promoter of disease progression in colitis and colon cancer, and that use of iron chelators might have a logical basis for inclusion in therapeutic modalities in the treatment of colonic inflammation and colon cancer. Citation Format: Vadivel Ganapathy, Ashish Gurav, Jaya P. Gnanaprakasam, Ellappan Babu, Yangzom D. Bhutia, Cynthia Reinoso Webb, Matthew B. Grisham. The iron-overload genetic disease hemochromatosis potentiates colonic inflammation and colon carcinogenesis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1557. doi:10.1158/1538-7445.AM2015-1557