P008 Whole-genome RNA sequencing in collagenous colitis: a subgroup analysis
C. Escudero-Hernández1, A. van Beelen Granlund2, T. Bruland3, A.K. Sandvik4, S. Koch5, A.E. Østvik3, A. Münch6
1Department of Biomedical and Clinical Sciences BKV, Linköping University, Linköping, Sweden, 2Centre of Molecular Inflammation Research and Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology NTNU, Trondheim, Norway, 3Department of Clinical and Molecular Medicine and Department of Gastroenterology and Hepatology, Norwegian University of Science and Technology NTNU, Trondheim, Norway, 4Centre of Molecular Inflammation Research, Department of Clinical and Molecular Medicine and Department of Gastroenterology and Hepatology, Norwegian University of Science and Technology NTNU, Trondheim, Norway, 5Department of Biomedical and Clinical Sciences BKV and Wallenberg Center for Molecular Medicine WCMM, Linköping University, Linköping, Sweden, 6Division of Gastroenterology and Hepatology, Department of Biomedical and Clinical Sciences BKV, Linköping University, Linköping, Sweden
Background
Collagenous colitis (CC) is a common inflammatory bowel disease that exhibits chronic watery diarrhoea. Treatment with the glucocorticoid budesonide is effective to induce and maintain clinical remission in most cases; however, few patients do not respond to treatment. To distinguish between different CC subgroups on a molecular level, we performed genome-wide RNA sequencing (RNAseq) analysis on mucosal samples.
Methods
We collected colonic biopsies from healthy controls (Hc) and CC patients with active disease. Additionally, we obtained matched samples from budesonide-responsive patients (clinical remission) under treatment with budesonide (9 mg/day, 8 weeks), and biopsies from budesonide-refractory patients (
Results
PCA of all samples identified three principal components which separated sample groups into distinct clusters of gene expression, explaining 31% of the transcriptional variation. PCA clearly demarcated UC samples from Hc and CC. Mucosal samples from budesonide-refractory patients exhibited a discrete RNA expression profile that was distinct from all other groups. Moreover, PCA of budesonide-responsive persons also separated active from treated CC. Subsequent DGE analysis revealed differential expression of 395 genes in patients with active CC compared with Hc, and that these genes were mainly involved in immune response, cell cycle and apoptosis, according to GSEA. Using IHC, we confirmed the impaired proliferation and immune response on the protein level. In samples from budesonide-treated patients, 75 genes were differentially regulated compared with controls. A paired comparison of matched samples from CC patients before and after induction of remission showed an expression change of 337 genes, mainly involved in DNA recognition.
Conclusion
CC is a transcriptionally homogeneous disease that can be characterised by differential gene expression. Unique gene expression profiles describe patient sub-populations, which could define budesonide-refractory CC as a distinct disease entity. Further study of the transcriptional landscape of CC may reveal pathogenic mechanisms and therapeutic targets for this common, debilitating inflammatory bowel disease.