259 Specific Crohn's Disease (CD) Associated Risk Alleles Are Associated with the Composition of the Intestinal Microbiota in Healthy First Degree Relatives (FDR) of CD Subjects

Background/aim: Both enteric glial cells (EGCs) and neurons consist of enteric nervous system and play an important role in physiological neurotransmission.In particular for EGCs of the stomach, its regulatory mechanism(s) under various stresses (mental, physical, acute, and/or chronic) remains to be elucidated.We investigated changes in mRNA expression and structural plasticity of gastric EGCs in the time course of the stress overload in a maternal separation (MS) model, a model of early life stress affecting central glial cells.Methods: Male Wistar rat pups underwent MS for 3 hours starting on postnatal days 2-14.At 8 weeks of age, we used the water immersion method as an acute stress (AS) model and excised the whole stomach at 24 hours later.For the AS, MS, MS+AS, and control groups, we evaluated mRNA expressions of glial fibrillary acid protein (GFAP) using real time RT-RCR.Whole mount longitudinal muscle-myenteric plexus preparations were used for immunohistochemistry of EGCs (GFAP) with pan neuronal marker (HuC/D).Results: GFAP mRNA expression was increased by 2-fold at 1 hour after AS compared to the controls ( p , 0.05).However, in the MS+AS group, GFAP mRNA expression was decreased to about 50% of levels of the MS group at 8 hours after AS.For morphological analysis, we firstly found the structural changes of gastric glial processes from surrounding to concealing directed toward neuronal cell bodies, and the changes were gradually remarkable according to the time of AS overload.We divided enteric glial processes into 2 types based on terminal processes structure: A "filamentous'' process with no an obvious neck portion and bulging terminal, and a "leaflike" process with a neck portion and a bulging head.Mean ratio of leaf-like processes to total processes per ganglion was 4% in the control group, which was increased to 17% by AS for 8 hours.The mean ratio was 13% in the MS group, and began to increase from 1 hour in a time dependent manner in the MS+AS group and reached up to 25% at 8 hours.Mean bulging head area of leaf-like processes was not affected by AS alone (0.8 μm 2 ) compared to the controls (0.9 μm 2 ).However, its area in the MS group (1.3 μm 2 ) tended to be higher than the controls.Furthermore, additional AS to the MS group significantly increased the mean area compared to that of the AS group (1.9 vs. 0.8 μm 2 , p , 0.05).Conclusion: Early life stress (maternal separation) rather than additional acute stress in adulthood caused structural plasticity of gastric EGCs, which may be critically important for glio-neural dysfunction of functional gastrointestinal diseases.