Studies in the expression and modulation of mucosal addressin cell adhesion molecule-1 (MAdCAM-1).
Doctoral thesis, UCL (University College London).
Introduction: The endothelial mucosal cell adhesion molecule (MAdCAM-1) is considered to be critically important in recruiting lymphocytes expressing the α4β7 cell surface integrin. In addition to its well-characterised role in the normal gastrointestinal tract, there is emerging evidence of its role in liver and gastrointestinal inflammation. The ability to detect MAdCAM-1 has thus far been challenging, hindering progress into studies to explore its modulation. Aims: (i) To characterise MAdCAM-1 in the liver and gut, (ii) establish an in vitro model system of MAdCAM-1 and (iii) investigate the factors leading to its expression and subsequent modulation. Methods: I have described novel methods of detecting MAdCAM-1 by: 1. Characterising its presence in the human liver, gut and associated tissues e.g. pancreas. 2. Developing a reverse transcriptase–polymerase chain reaction (RT-PCR) technique so as to detect MAdCAM-1 in the gastrointestinal system and thus quantify its expression using Real-Time RT-PCR analysis. 3. Developing an in vitro cell culture system using the endothelial SVEC4-10 cells to express and subsequently modulate the expression of MAdCAM-1. Results: Using immunohistochemical methodology I found that in end stage chronic liver disease, MAdCAM-1 is expressed primarily on the peribiliary plexus and lymphoid aggregates, where it may facilitate lymphocyte egress. MAdCAM-1’s constitutive expression was confirmed in histologically normal gut tissue and its upregulation was demonstrated in ulcerative colitis and Crohn’s disease, particularly localised to the venular endothelium of the lamina propria and follicular dendritic cells. MAdCAM-1 mRNA from human gut was measured by a RT-PCR technique in which a 94 base pair product consistent with human mucosal vascular MAdCAM-1 was detected in normal large bowel. Real Time analysis confirmed that MAdCAM-1 was upregulated in end stage liver disease. In a cell culture system MAdCAM-1 was shown to be upregulated by TNFα on SVEC4-10 using immunofluoresence studies and its expression was further modulated by steroids and anti-sense oligonucleotides. Conclusion: The importance of MAdCAM-1 in the gastrointestinal system is emphasised throughout. Our in vitro culture system utilising the SVEC endothelial cell line provides the basis for studying the modulation of MAdCAM-1 expression.
|Title:||Studies in the expression and modulation of mucosal addressin cell adhesion molecule-1 (MAdCAM-1)|
|Open access status:||An open access version is available from UCL Discovery|
|UCL classification:||UCL > School of Life and Medical Sciences > Faculty of Medical Sciences > Medicine (Division of)|
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