258 Exosomes Derived From Pancreatic Stellate Cells: microRNA Signature and Effects on Pancreatic Cancer Cells

Background & Aims: Environmental enteropathy (EE) is a subclinical intestinal condition highly prevalent in lowand middle-income countries characterized, in part, by malabsorption, intestinal villous atrophy, and crypt hypertrophy. The pathogenesis of EE remains unclear, however supplementation with folate (a key source of one carbon units for DNA methylation) is an effective adjunct therapy for tropical sprue, i.e., persistent diarrhea on a background of EE. To determine the extent to which methyl donor deficiency (MDD) provokes features of EE in mice, we evaluated mechanistic links between dietary methyl donor deficiency and intestinal crypt hypertrophy in mice and in mouse small intestinal crypt cultures (enteroids). Methods: We randomized dams to a standard diet or an isocaloric MDD diet lacking folate, choline, and betaine when pups were 10-days-old. We then randomized weanlings to their dams' diet on day of life 21. Mice were sacrificed and the jejunum was harvested at 6 weeks of age for both histology (n=6/group) and generation of enteroids. Results: Histological comparisons of the jejunum revealed longer crypts in MDD versus control mice, moreso in the distal (85.6 +/13.7 μm vs. 69.3 +/7.2 μm; P<0.0001), vs. proximal (88.8 +/17 μm vs 80.7 +/10.7 μm; P=0.04) portions of the small intestine. Enteroids from control and MDD mice were both viable in standard minigut media; however, all enteroids maintained in MDD media displayed alterations in crypt morphology and decreased epithelial proliferation. Enteroid crypt neck width was 1.3-fold greater in standard vs. MDD media (P<0.001). The number of crypt buds per enteroid was 1.6-fold higher in standard media vs. MDD media (p = 0.0007). The ratio of EdU-positive, or proliferating, cells to Hoechst-positive cells was 2.2-fold higher in standard media vs. MDD media (P<0.0001). Qualitatively, enteroids in MDD media displayed longer crypt domains vs. enteroids in standard media. Conclusions: Complementary in vivo and in vitro findings of altered small intestinal crypt in the setting of methyl donor deficiency suggest that methyl donor deficiency plays a role in the pathogenesis of environmental enteropathy. Further studies are needed to determine whether prolonged methyl donor deficiency promotes epigenetic changes of intestinal stem cells and whether methyl donor supplementation prevents or reverses these changes to promote intestinal epithelial homeostasis in global settings of poverty.