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INTRODUCTION: A coeliac disease (CD) diagnosis is likely in children with levels of tissue transglutaminase autoantibodies (anti-TG2) >10 times the upper reference value, whereas children with lower anti-TG2 levels need an intestinal biopsy to confirm or rule out CD. A blood sample is easier to obtain than an intestinal biopsy sample, and stabilised blood is suitable for routine diagnostics because transcript levels are preserved at sampling. Therefore, we investigated gene expression in stabilised whole blood to explore the possibility of gene expression-based diagnostics for the diagnosis and follow-up of CD. DESIGN: We performed RNA sequencing of stabilised whole blood from active CD cases (n=10), non-CD cases (n=10), and treated CD cases on a gluten-free diet (n=10) to identify diagnostic CD biomarkers and pathways involved in CD pathogenesis. RESULTS: No single gene was differentially expressed between the sample groups. However, by using gene set enrichment analysis (GSEA), significantly differentially expressed pathways were identified in active CD, and these pathways involved the inflammatory response, negative regulation of viral replication, translation, as well as cell proliferation, differentiation, migration, and survival. The results indicate that there are differences in pathway regulation in CD, which could be used for diagnostic purposes. Comparison between GSEA results based on stabilised blood with GSEA results based on small intestinal biopsies revealed that type I interferon response, defence response to virus, and negative regulation of viral replication were identified as pathways common to both tissues. CONCLUSIONS: Stabilised whole blood is not a suitable sample for clinical diagnostics of CD based on single genes. However, diagnostics based on a pathway-focused gene expression panel may be feasible, but requires further investigation., Funding agencies: Futurum-the Academy for Health and Care, Region Jonkoping County; Medical Research Council of Southeast Sweden

Celiac disease (CD) is a chronic small intestinal immune-mediated enteropathy triggered by gluten. The only currently available treatment is complying with a lifelong gluten-free diet, which should not be commenced before a CD diagnosis has been established by diagnostic test results (including histopathologic assessment of small intestinal biopsies and CD-specific antibody levels). This makes diagnostic swiftness and accuracy important. In cases with low CD-specific antibody levels and/or low-grade intestinal injuries the diagnosis can be difficult to establish. The main objective of this thesis was to complement and improve CD diagnostics by identifying and implementing new biomarkers, mainly based on gene expression, in small intestinal biopsies and blood. In paper I, genes were selected to reflect villous height, crypt elongation, immune response, and epithelial integrity. The results showed that a subset of those genes could discriminate active CD mucosa from mucosa without CD-related changes and grade the intestinal injury. In paper III, an unbiased investigation of gene expression in CD mucosa was performed using transcriptome analysis. Active CD and non-CD mucosa showed differential expression in a subset of genes, and some were differentially expressed in CD mucosa before histopathologic assessment could confirm intestinal alterations compatible with a CD diagnosis. Gene set analysis revealed that there are many biological processes affected in CD mucosa, including those associated with immune response, microbial infection, phagocytosis, intestinal barrier function, metabolism, and transportation. In parallel, gene expression was investigated in stabilised whole blood. Blood is a more accessible sampling material than intestinal biopsies, and stabilised blood is suitable for routine diagnostics since transcript levels are preserved at sampling. In paper II, expressions from a selection of genes were quantified in stabilised whole blood (RNA) and/or plasma (

Background: Blood-based diagnostics has the potential to simplify the process of diagnosing celiac disease (CD). Although high levels of autoantibodies against tissue transglutaminase (anti-TG2) are strongly indicative of active CD, several other scenarios involve a need for additional blood-based CD markers. Methods: We investigated the levels of messenger RNA (mRNA) in whole blood (n = 49) and protein in plasma (n = 22) from cases with active CD (n = 20), with confirmed CD and normalized histology (n = 15), and without a CD diagnosis (n = 14). Group differences were analyzed using Kruskal-Wallis one-way analysis of variance by ranks. We also investigated correlations between levels of potential markers, histopathology according to the modified Marsh scale, and CD risk gradient based on HLA type, using Spearman rank correlation. The relation between HLA-DQ2 gene dose effect and the expression levels of selected blood-based markers was investigated using the Mann-Whitney U test. Finally, the diagnostic performance of anti-TG2, potential blood-based CD markers, and logistic regression models of combined markers was evaluated using receiver operating characteristic (ROC) curve analysis. Results: CXCL11 protein levels and TNFRSF9 and TNFSF13B mRNA levels were identified as potential CD markers. These are all affected by or involved in the regulation of the NF-kappa B complex. CXCL11 protein levels and IL21 and IL15 mRNA levels were correlated with histopathology according to the modified Marsh scale, as were the established CD markers. HLA genotype risk and HLA-DQ2 gene dose effect did not show any significant relations with either the potential CD markers or the established CD markers. ROC curve analysis revealed a slight, non-significant increase in the area under the curve for the combined use of anti-TG2 and different constellations of potential blood-based CD markers compared to anti-TG2 alone. Conclusions: The CD markers identified in this study further emphasize, Funding Agencies|Futurum - the Academy for Healthcare; Jonkoping County Council; Medical Research Council of Southeast Sweden

AIM: To investigate a possible genetic influence of claudin (CLDN) 1, CLDN2 and CLDN4 in the etiology of inflammatory bowel disease. METHODS: Allelic association between genetic regions of CLDN1, CLDN2 or CLDN4 and patients with inflammatory bowel disease, Crohn's disease (CD) or ulcerative colitis were investigated using both a case-control study approach (one case randomly selected from each of 191 Swedish inflammatory bowel disease families and 333 controls) and a family-based study (463 non-Swedish European inflammatory bowel disease-families). A nonsynonymous coding single nucleotide polymorphism in MORC4, located on the same linkage block as CLDN2, was investigated for association, as were two novel CLDN2 single nucleotide polymorphism markers, identified by resequencing. RESULTS: A single nucleotide polymorphism marker (rs12014762) located in the genetic region of CLDN2 was significantly associated to CD (case-control allelic OR = 1.98, 95% CI: 1.17-3.35, P = 0.007). MORC4 was present on the same linkage block as this CD marker. Using the case-control approach, a significant association (case control allelic OR = 1.61, 95% CI: 1.08-2.41, P = 0.018) was found between CD and a nonsynonymous coding single nucleotide polymorphism (rs6622126) in MORC4. The association between the CLDN2 marker and CD was not replicated in the family-based study. Ulcerative colitis was not associated to any of the single nucleotide polymorphism markers. CONCLUSION: These findings suggest that a variant of the CLDN2-MORC4 region predisposes to CD in a Swedish population.

Celiac disease (CD) is identified by histopathologic changes in the small intestine which normalize during a gluten-free diet. The histopathologic assessment of duodenal biopsies is usually routine but can be difficult. This study investigated gene expression profiling as a diagnostic tool. A total of 109 genes were selected to reflect alterations in crypt-villi architecture, inflammatory response, and intestinal permeability and were examined for differential expression in normal mucosa compared with CD mucosa in pediatric patients. Biopsies were classified using discriminant analysis of gene expression. Fifty genes were differentially expressed, of which eight (APOC3, CYP3A4, OCLN, MAD2L1, MKI67, CXCL11, IL17A, and CTLA4) discriminated normal mucosa from CD mucosa without classification errors using leave-one-out cross-validation (n = 39) and identified the degree of mucosal damage. Validation using an independent set of biopsies (n = 27) resulted in four discrepant cases. Biopsies from two of these cases showed a patchy distribution of lesions, indicating that discriminant analysis based on single biopsies failed to identify CD mucosa. In the other two cases, serology support class according to discriminant analysis and histologic specimens were judged suboptimal but assessable. Gene expression profiling shows promise as a diagnostic tool and for follow-up of CD, but further evaluation is needed.