Introduction: 12,000 infrainguinal bypass grafts are performed annually in the UK. Despite improvements in surgical technique, outcomes remain suboptimal: 20% of above knee grafts require intervention to maintain patency by 3 years. Only antiplatelet agents have been demonstrated thus far to improve graft survival. 80% of graft failure is as a result of intimal hyperplasia, an inflammatory process characterised by the proliferation and migration of vascular smooth muscle cells. Toll Like Receptors (TLR), part of the innate immune system, have been implicated in atherosclerosis formation but not investigated in a model of infrainguinal graft failure. When a vein is used as a conduit for infrainguinal bypass graft it has been exposed to ischaemic and hypoxic conditions: preliminary data has demonstrated that ischaemic vascular smooth muscle cell explants are hyperproliferative. Phospholipase C γ (PLC γ) is a signalling pathway with potential links to innate immune pathways and pathways induced by hypoxia and ischaemia. Methods: Human vein tissue was obtained from patients undergoing amputation and coronary artery bypass surgery and used for immunohistochemistry and to obtain vascular smooth muscle cells by explant method. Immunohistochemistry was used to determine the presence of TLR4 and PLC γ in human vein tissue. Specific TLR Ligands were used to determine the functional response of TLR’s in vascular smooth muscle cells as measured by Interleukin 8 ELISA. Radiolabelled Thymidine incorporation was used to measure proliferation of vascular smooth muscle cells in response to TLR4 activation, hypoxia and PLC γ inhibition. Results: TLR4 was demonstrated to be present in human vein tissue, and functionally active in human vascular smooth muscle cells. Furthermore stimulation with the specific ligand of TLR4 caused enhanced proliferation of vascular smooth muscle cells. Hypoxia (5% and 10% Oxygen) significantly enhanced proliferative responses of vascular smooth muscle cells. PLC γ was demonstrated to be present in human vein tissue, and inhibition, using U73122 in vascular smooth muscle cells reduced proliferation. Conclusion: TLR activation and hypoxia appear to enhance the proliferative responses of human vascular smooth muscle cells, a key cellular pathway of intimal hyperplasia formation and infrainguinal graft failure. Inhibition of PLC γ reduces proliferative responses. Further research is required to confirm that PLC γ is a key common pathway mediating enhances of proliferation caused by TLR activation and hypoxia.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:559907 |
| Date | January 2011 |
| Creators | Jackson, Andrew John |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/2417/ |
Page generated in 0.0015 seconds