2021 Summer.Includes bibliographical references.The intestinal wall is a multicompartmental barrier tissue composed of over 25 distinct cell types with integrated and complex signaling both within and between compartments. The gut wall is also a large endocrine organ comprised of cells capable of producing dozens of peptides used for hormonal and other signaling functions. However, the mechanistic roles that neural secretions play in regulating the gut epithelial barrier in health and disease are not well known. Additionally, frequently used models available for studying intestinal function outside of the body lack the complexity to investigate neural – epithelial and neural – immune signaling interactions. Using a bifurcated approach to method development, we created two culture systems for maintaining the full thickness of the intestinal wall ex vivo. One method allows for culture of mouse or human organotypic intestinal slices that maintain the gut wall for 6 or 4 days, respectively. This system does not however, maintain a true luminal – epithelial barrier as seen in the in vivo gut. The second method, a microfluidic organotypic device (MOD) enables maintenance of explanted mouse or pig intestinal tissue for up to 3 days ex vivo, with an intestinal barrier intact. These two methods allow for investigating and cross-validating of numerous biological questions now previously possible using traditional culture models. Neuronal fiber proximity to gut epithelia has been shown, with goblet, tuft and enteroendocrine cells being closely opposed by fibers. Goblet cells secrete mucopolysaccharides, a first line of defense separating luminal microbiota from host tissue. I have recently shown that vasoactive intestinal peptide (VIP) can regulate goblet cell production in organotypic slices of mouse ileum. This peptide is also in close proximity to Paneth cells in the base of the crypt, and enteric mast cells. There were sex differences in baseline mast cell neuronal proximity, quantities, and cell size in mouse ileum. Further, mast cells showed a sex difference in responses to lipopolysaccharide challenge. Further investigation of neurosecretory factor regulation of immune and epithelial function is needed, both in goblet cells and other secretory epithelia like anti-microbial producing Paneth cells, and in immune components like mast cells. Graphical illustration of the dissertation project is included below
