Celiac.com 05/10/2018 - Most people who suffer from inflammatory bowel diseases (IBD) have either Crohn’s disease or ulcerative colitis. Some research has suggested that patients with Crohn's disease have an altered response to vitamin D, among other issues. The exact mechanism behind this is not well understood.
To get a better picture of the problem, a team of researchers recently set out to investigate disease-specific gene expression profiles of peripheral blood mononuclear cells (PBMCs) from Crohn’s disease patients in clinical remission. The research team included Holger Schäffler, Maria Rohde, Sarah Rohde, Astrid Huth, Nicole Gittel, Hannes Hollborn, Dirk Koczan, Änne Glass, Georg Lamprecht, and Robert Jaster, with the Department of Medicine II, Division of Gastroenterology, Rostock University Medical Center in Rostock, Germany.
Meanwhile the team isolated healthy donors for further analysis. The team then cultured the cells with vitamin D, peptidoglycan (PGN) and lipopolysaccharide (LPS) for defined periods of time before RNA was isolated and subjected to microarray analysis using Clariom S assays and quantitative real-time PCR. They assessed the NOD2- and disease-specific gene expression profiles with repeated measure ANOVA using a general linear model.
The team used microarray assays to find 267 genes that were significantly up- or downregulated in PBMCs of WT-NOD2 patients, compared to healthy donors after challenge with vitamin D and/or a combination of LPS and PGN (P < 0.05; threshold: ≥ 2-fold change). For further analysis by real-time PCR, the team selected genes with known impact on inflammation and immunity that fulfilled predefined expression criteria.
In a larger group of patients and controls, the team found a disease-associated expression pattern, with higher transcript levels in vitamin D-treated PBMCs from patients, in three of these genes, CLEC5A (P < 0.030), lysozyme (LYZ; P < 0.047) and TREM1 (P < 0.023). The team found six genes that were expressed in a NOD2-dependent manner (Crohn's disease101, P < 0.002; CLEC5A, P < 0.020; CXCL5, P < 0.009; IL-24, P < 0.044; ITGB2, P < 0.041; LYZ, P < 0.042).
Interestingly, the team saw the highest transcript levels in patients with heterozygous NOD2 mutations.
This study identifies CLEC5A and LYZ as Crohn's disease- and NOD2-associated genes of PBMCs and supports the need for further studies on their pathomechanistic roles. The team found that PBMCs of patients with Crohn's disease display alterations in their response to vitamin D and PAMPs.
Disease-associated and NOD2-dependent gene expression profiles are preserved even during clinical remission. The team’s data identifies CLEC5A, LYZ and TREM1 as good candidates for follow-up study. The researchers propose that these genes may act in a common network relevant to celiac disease development.
The research team remains committed to the longterm goal of biomarkers to that will accurately predict the clinical course of celiac disease.