Colonisation of prosthetic grafts by immunocompetent cells in a sheep model

The present study examined the distribution of immunocompetent cells in syn thetic vascular grafts in an experimental sheep model. Sixty-two adult Meri no sheep underwent synthetic patch closure of a longitudinal arteriotomy in the left common carotid artery. The synthetic patch materials used were ge latin sealed Dacron (n = 10), fluoropassivated Dacron (n = 10), Fluoropassi v (n = 12), polyurethane (n = 10), expanded polytetrafluoroethylene (n = 10 ) and carbon-lined expanded polytetrafluoroethylene (n = 10), The sheep wer e sacrificed after four weeks when the prosthetic patches were harvested an d fixed in 10% neutral buffered formalin. Transverse sections were taken al ong the graft and paraffin embedded. Serial sections were stained with cell type specific antibodies to identify T-lymphocytes (CD3(+)), dendritic cel ls (S-100(+)), endothelial cells (von Willebrand factor(+)) and smooth musc le cells (smooth muscle alpha-actin(+)), All six graft types contained CD3( +) and S-100(+) cells in the neointima, within the synthetic matrix and in the perigraft layer. Three different tissue responses to synthetic material s were observed and the grafts were classified accordingly into three group s: (1) gelatin sealed Dacron, fluoropassivated Dacron and Fluoropassiv; (2) expanded polytetrafluoroethylene and carbon-lined expanded polytetrafluoro ethylene; (3) polyurethane. The three synthetic materials in Group 1 showed almost identical reactions with least accumulation of immunocompetent cell s within the synthetic material but greater accumulation of immunoinflammat ory infiltrates in the perigraft vascular tissue. In this group, new vessel s penetrated into the synthetic material and there was prominent formation of foreign body (giant) cells, Group 2 showed greater accumulation of immun ocompetent cells within the synthetic material itself but only sparse immun e-inflammatory infiltrates in the perigraft tissue. Group 3 showed a high d egree of inflammatory response within both the synthetic material and the p erigraft vascular tissue, These observations demonstrate that immunocompete nt cells colonise the synthetic matrix of grafts and accumulate in the peri graft tissue, but inflammatory responses vary in different graft types. (C) 2001 The International Society for Cardiovascular Surgery. Published by El sevier Science Ltd. All rights reserved.