Abstract 26: Stroke Impairs Epithelial Microfold Cells in Intestinal Peyer’s Patches

Abstract

Introduction: Peyer’s patches (PP) are lymphatic tissue in the small intestine. Tissue-resident specialized epithelial cells [microfold (M) cells] are essential for immune surveillance in the gut by sensing pathogens and eliciting immune responses by lymphocytes. Emerging evidence highlights the importance of gut microbiota as an epicenter for post-stroke infection, however the role of PP and M cells in stroke is still undefined. Hypothesis: Ischemic stroke influences the antigen-sampling systems in intestinal PPs. Methods: Young (8-10 wks) and aged (18-20 months) C57BL/6N male mice were subjected to either sham or 60-minute middle cerebral artery occlusion (MCAO) followed by reperfusion. Mice were sacrificed at day 3 after stroke. The small intestines were isolated and PP tissue was obtained. The numbers and structure of the PP and M cells were assessed using whole-mounts and confocal microscopy. Gene expression in PP was examined using real-time qPCR. Finally, immune cells in PPs were evaluated using flow cytometry. Results: The number of PPs was dramatically reduced at day 3 after stroke. Sham mice had 7 to 10 PPs in their small intestines, whereas stroke mice only retained 2 to 5 PPs (n=4/group, P <0.05). Aging also decreased the numbers of PPs both in sham (5 to 6) and stroke mice (1 to 4) (n=4/group, P <0.05). Whole-mount assays revealed that stroke impaired the number of UEA-1 + WGA - M cells as well as the structure of the PP. Stroke induced the loss and shrinkage of villus and decreased both villus M cells and fucosylated epithelial cells in the distal ileum. Additionally, stroke abrogated the mRNA expression of Gp2 and RANKL pathway genes such as Tnfsf11 (RANK) and Tnfsf11a (RANKL) that are responsible for M cell maturation and function, respectively (1.95, 1.31 and 2.67 fold change in Gp2, Tnfsf11 and Tnfsf11a, respectively, n=4/group, P <0.05). However, we did not observe a significant change of immune cells in PP after stroke. Conclusions: The response of PP in stroke was highly epithelial M cell-specific. Although the understanding of interactions between luminal antigens including bacteria and PP is still needed, our data provides us with a new insight into how brain damage can alter antigen sampling and shape adaptive immunity in the host.