Proceedings of The Physiological Society
University of Edinburgh (2011) Proc Physiol Soc 25, C14 and PC14
Vein graft neointima formation: chronic recruitment of circulating cells by dysfunctional endothelium in addition to smooth muscle cell proliferation
J. Wu1, C. L. Lawrence1, P. Maffia2, S. Kennedy2, R. M. Wadsworth1
1. University of Strathclyde, Glasgow, United Kingdom. 2. University of Glasgow, Glasgow, United Kingdom.
Background: Neointima hyperplasia has generally been considered to originate primarily from smooth muscle cell proliferation, and is the most important pathology in development of vein graft occlusion as well as other types of vascular disease. However, the dynamics of neointimal cell proliferation and vascular remodelling is not fully understood. Methods: To perform the vein graft surgery, a donor mouse was sacrificed by CO2 and the thoracic inferior vena cava harvested. The recipient mouse was anaesthetised by intra-peritoneal injection of 60mg/kg sodium pentobarbital. The vena cava from the donor mousewas then inserted into the common carotid artery of the recipient mouse. Buprenorphine (0.1mg/kg) was given by subcutaneous injection right after the surgery. 4 weeks after implantation, the recipient mouse was sacrificed by CO2. The vein graft was harvested and fixed with 4% formaldehyde for morphology or immunohistochemistry. Results: Neointima thickening developed progressively over 4 weeks following vein grafting. The smooth cell markers alpha-actin and smooth muscle myosin heavy chain were exclusively expressed in the neointima by 4 weeks; however cell proliferation (stained by anti-PCNA antibody) was observed throughout the whole vein graft wall (neoadventitia plus neointima). Interestingly, the most proliferative region was usually co-localised with the most inflamed neointimal or neoadventitial area, with less or no smooth muscle markers expression. Proliferating cells negative for smooth muscle cell markers were also observed located peripherally to mature neointima, which may contribute to the second wave of neointima thickening. Leukocytes or monocular cells originated from the blood stream were often observed rolling or firmly adherent to the regenerated endothelium. The neointima are usually less developed but more inflamed in the middle part of the vein graft, compared to the anastomosis area. The poorly developed neointimal area is often associated with poor endothelial regeneration and severe adventitial inflammation, which were of very high cell density with intensive proliferation and cell death. Summary: Our observations were consistent with published reports that a large portion of the neoinitma cells may originated from the circulation. The non-smooth muscle cell recruitment and proliferation may contribute to the vein graft chronic inflammation and neointima thickening even at a chronic remodelling stage. The inflamed neointimal area and regenerated dysfunctional/immature endothelium may attract continuous cell recruitment leading to accelerated atherosclerosis.
Where applicable, experiments conform with Society ethical requirements