Elsevier

Cardiovascular Surgery

Volume 8, Issue 4, June 2000, Pages 265-273
Cardiovascular Surgery

Identification of dendritic cells in ePTFE grafts explanted from humans

https://doi.org/10.1016/S0967-2109(00)00023-5Get rights and content

Abstract

Following implantation different cell types interact with synthetic vascular prostheses resulting in a complex immuno-inflammatory response. Dendritic cells are responsible for activating the primary T-lymphocyte immune response in various pathological conditions by their role as antigen-presenters. This study aimed at examining whether dendritic cells accumulate within small diameter expanded polytetrafluoroethylene (ePTFE, Goretex®) grafts explanted from humans. Segments of expanded polytetrafluoroethylene were explanted from 11 patients (6 male, 5 female), aged between 60 and 83 years (mean 70.7 years) at secondary or revision bypass operation. The graft implant duration varied from 4 months to 12 years (mean 40.5 months). Dendritic cells were identified immunohistochemically using S-100 antibody, as well as by electron microscopy. Immunohistochemical examination showed that all 11 explanted synthetic grafts contained S-100+ cells colonising both the synthetic matrix itself, and the adjacent perigraft tissue. Electron microscopic analysis confirmed the presence of cells with a characteristic dendritic cell morphology within the grafts. Dendritic cells which accumulated within synthetic grafts were found to co-localise with T-lymphocytes. Based on these observations, we speculate that dendritic cells may be involved in the immuno-inflammatory responses following the implantation of synthetic vascular prostheses through their interaction with T-lymphocytes.

Introduction

The clinical results with small diameter synthetic grafts remains inferior to that of autologous vein or artery for bypass procedures 1, 2, 3, 4. Many different synthetic materials have been used in recent years in both animal and clinical studies, however, their use is limited by occlusion due to thrombus formation and by the development of neointimal hyperplasia 5, 6, 7, 8, 9.

Following the implantation of a synthetic vascular prosthesis into the bloodstream, a sequence of events take place involving, in particular, the accumulation of immunocompetent cells, including lymphocytes and macrophages 10, 11, 12, 13, 14, 15, 16, 17. Theoretically, dendritic cells, which are potent antigen-presenting cells 18, 19, may also be involved in this immune response to synthetic grafts. However, the involvement of dendritic cells in this immuno-inflammatory response has not been studied previously.

The aim of this study was to examine small diameter synthetic ePTFE (Goretex®, WL Gore and Assoc, Inc., Flagstaff, AZ, USA) grafts explanted from humans for the presence of immuno-inflammatory cells and specifically for cells with dendritic morphology. We considered that dendritic cells may promote and regulate the inflammatory response by invading the vascular prostheses and may therefore contribute to graft failure.

Section snippets

Materials and methods

Materials were collected in accordance with the principles outlined in the Declaration of Helsinki [20]and this study was approved by the Institutional Review Board of St Vincent's Hospital, Sydney, Australia.

Characteristics of the luminal surface of the ePTFE grafts

Examination of haematoxylin stained sections showed that neointima was consistently present on the luminal surface of the grafts at the anastomotic regions. However, the thickness of the neointima gradually diminished at distances further from the anastomoses and the central regions of the grafts were consistently free of neointima in all cases.

Within the anastomotic areas and within the immediately adjacent areas, the thickness of the neointimal layer varied markedly, but in all grafts, the

Discussion

The main observation of the present study is that dendritic cells accumulate within the ePTFE vascular grafts. The finding of dendritic cells, associated with T-lymphocytes, within the synthetic vascular grafts suggests that dendritic cells may be important in immuno-inflammatory reactions associated with the implantation of foreign materials into the vascular system. Our immunohistochemical observations showed that the number of S-100+ dendritic cells accumulating within the synthetic grafts

Acknowledgements

We thank the St Vincent's Clinic Foundation, Sydney, Australia for financial support.

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