Authors A. ACCARIE (1), J. TOTH (1), L. WAUTERS (1), R. FARRÉ (1), J. TACK (1), T. VANUYTSEL (1) / [1] KU Leuven, , Belgium, Translational Research Center for Gastrointestinal Disorders Introduction Functional gastro-intestinal disorders (FGID) such as IBS and FD are more prevalent in women than in men with a ratio of 2:1. Furthermore, stressful life events were reported as one of the triggers for FGID symptoms in patients. Recently our group identified the normoglycemic diabetes prone BioBreeding rat (BBDP rat) as a spontaneous model of FGID with increased jejunal permeability, immune cells infiltration and visceral hypersensitivity in the colon (Meleine, DDW 2017) in both males and females, but more pronounced in the latter. We also demonstrated stress-induced visceral hypersensitivity in females only (Accarie, DDW 2018). In this study we aimed to investigate the role of estrogens in GI symptoms at baseline and after maternal separation. Aim In this study we aimed to investigate the role of estrogens in GI symptoms at baseline and after maternal separation. Methods Newborn female rats were separated from the dams from day 2 to 15, 3 hours per day. Control animals were not handled until the weaning. Anxiety levels were determined with the marble burying test before testing the colonic sensitivity, which was assessed before and two weeks after ovariectomy (ovx; 8/group) by measuring the visceromotor response (VMR) to isobaric (15, 30, 45 and 60 mmHg) rectal distensions corrected to wall tension according to Laplace’s law. Two days after the sensitivity test rats were euthanized and tissue was mounted in Ussing chambers after removal of the muscle layer. Epithelial integrity was evaluated using cumulative transepithelial passage of fluorescein isothiocyanate-dextran of 20kDa (jejunum) or 4 kDa (colon) over 120 min. Mast cell and eosinophil density in the lamina propria were quantified by Mast Cell Protease type 2 immunostaining or Chromotrope 2R staining respectively. Results In non-stressed conditions, ovariectomy affected jejunal (598.4±167.3 (sham) vs 252.4±71.2 (ovx) pmol/cm² n=6 p=0.05) and colonic barrier function (65.4±13.4 (sham) 308.7±108.1 (ovx) pmol/cm² n=6 p=0.03) and induced an increase of immune cell density in the jejunum and a decrease in the colon while colonic sensitivity and anxiety were unaltered. In contrast, the exposure to an early life stress resulted in an increased VMR in female rats, suggesting colonic hypersensitivity, which was abolished after ovariectomy (p<0.01). In the same way, the increased number of marbles buried, reflecting anxiety, was reduced after ovariectomy (5.8±1.3 vs 2.5±0.7 p=0.05). However, the increased immune cells infiltration in the colonic and jejunal epithelial and permeability in both regions remained unaltered after ovariectomy. Conclusions Our results point out a different role for estrogens on FGID pathogenesis under stress and non-stress conditions. These observations highlight the necessity to focus on female animals in the context of FGID and stress-related alterations and further validate the BB-rat as an attractive model to characterize the gender-dependent pathophysiology of FGID.
