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Title: Pathological epithelial cell apoptosis and shedding in the murine small intestine
Author: Williams, Jonathan
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2013
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The intestinal epithelium represents a critical component of the gut barrier and is composed of a single layer of intestinal epithelial cells (IECs) held together by tight junctions. This epithelium prevents the entrance of harmful microorganisms, antigens and toxins from the gut lumen into the circulation. Small intestinal homeostasis is maintained by the rate of shedding of senescent enterocytes from the villus tip exactly matching the rate of generation of new cells in the crypt. However, in various localised and systemic inflammatory conditions, intestinal homeostasis may be disturbed as a result of increased IEC shedding. Such pathological IEC shedding may cause transient gaps to develop in the epithelial barrier and result in increased intestinal permeability. Although pathological IEC shedding has been implicated in the pathogenesis of inflammatory bowel disease, understanding of the underlying mechanisms remains limited. This thesis describes the development of a murine model to study this phenomenon, as IEC shedding in this species is morphologically analogous to humans. IEC shedding was induced by systemic lipopolysaccharide (LPS) administration in wild-type C57BL/6 mice, and mice deficient in TNF-receptor 1 (Tnfr1-/-), Tnfr2-/-, Nuclear Factor kappa B1 (Nfkb1-/-) or Nfkb2-/-. IEC apoptosis and cell shedding was quantified using immunohistochemistry for active Caspase-3 and gut lumen to systemic circulation permeability was assessed by measuring plasma fluorescence following fluorescein isothiocyanate-dextran gavage. LPS at doses ≥0.125mg/kg induced rapid villus IEC apoptosis and cell shedding which was maximal at 1.5h. This coincided with significant villus shortening, fluid exudation into the gut lumen and diarrhoea. A significant increase in gut to circulation permeability was observed at 5h. TNFR1 was essential for LPS-induced IEC apoptosis and shedding and the fate of the IEC was also dependent on NFκB, with signalling via NFκB1 favouring cell survival, and via NFκB2 favouring apoptosis. This model will enable investigation of the importance and regulation of pathological IEC apoptosis and cell shedding in intestinal and systemic diseases.
Supervisor: Pritchard, Mark; Campbell, Barry Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: RC Internal medicine