P101 Functional translation of IBD-associated genetic variation in patient-derived intestinal epithelial cells
W. Vanhove*1, K. Nys1, I. Arijs1, I. Cleynen2, G. Van Assche1, M. Ferrante1, S. Vermeire1
1KU Leuven, Translational Research Centre for Gastrointestinal Disorders (TARGID), Department of Clinical and Experimental Medicine, Leuven, Belgium, 2KU Leuven, Department of Human Genetics, Leuven, Belgium
In contrast to the general acceptance that IBD represents a spectrum of disease phenotypes with distinct behavioural features, overall management of IBD is quite homogenous. With the imminent introduction of new therapeutic classes for IBD patients, adequate characterisation and improved stratification of patients based on the underlying disease mechanisms will be essential. Large-scale studies have identified bacterial recognition and handling, autophagy, and ER stress signalling as interlinked inflammatory signalling pathways driving IBD pathogenesis. Genetic variation in these pathways may affect normal (immune) function of the intestinal epithelium, responsible for conserving host-microbial interactions and tissue homeostasis. We studied if genetic variation in IBD-associated pathways translates into distinct epithelial cell functional activity. These functional read-outs could in turn be used for an improved stratification of IBD patients.
Endoscopically derived mucosal biopsies were obtained from the colon of 35 IBD patients, all genotyped by immunochip. Intestinal epithelial crypts were isolated in collagen-coated wells, resulting in a monolayer of intestinal epithelial cells (IECs). We recently developed and validated a short-term culture system for deriving IECs from IBD patients. These cells were assessed for correlation of autophagic activity and/or ER stress level with 8 IBD-associated SNPs linked to ER stress (XBP1; ORMDL3) and autophagy (ATG16L1, IRGM, ULK1, MTMR-3, and LRRK2). ER stress level and autophagic activity were evaluated by ELISA-based quantification of BiP/GRP78 (with[out] thapsigargin) and p62/SQSTM1 (after addition of chloroquine).
All patients were selected based on the distribution of risk alleles (Q1 or Q4): patients in Q1 (3 ≤ autophagy- or ≤ 1 ER stress-related risk alleles) were considered to have a low genetic risk for IBD-associated pathway perturbation while patients in Q4 (≥ 5 autophagy- or ≥2 ER stress-related risk alleles) were considered to be at high genetic risk. Presence of a high autophagic genetic risk score showed a trend of increased ER stress (low 1.8 to high 2.7 ng/ml BiP) and decreased autophagic activity (low 1.4 to high 1.2 ng/ml p62) compared with low autophagic genetic risk patients. Epithelial cell cultures of high ER stress-related genetic risk patients showed a trend of increased ER stress (low 1.9 to high 2.5 ng/ml BiP) and increased autophagic activity (low 1.2 to high 1.5 ng/ml p62).
Genetic variation in IBD-pathways (ER stress, autophagy) tends to affect the level of ER stress and the autophagic activity measured in patient-derived epithelial cell cultures and supports the potential of translating molecular clues into personalised management of IBD.