Cellular proliferation and macrophage populations associated with implanted expanded polytetrafluoroethylene and polyethyleneterephthalate

The chronic inflammatory response associated with the abluminal surface of polymeric vascular grafts has been suggested to affect adversely graft neov ascularization, the cellular response at the luminal surface of vascular gr afts, and overall graft patency. To better understand the source for this c hronic inflammation, this study examined two types of macrophages and the a mount of cellular proliferation around two widely used graft materials, exp anded polytetrafluoroethylene (ePTFE) and polyethyleneterephthalate (PET or Dacron) implanted in the rat for 3 and 5 weeks. Serial sections of explant s were analyzed for recruited macrophages (ED1), resident macrophages (ED2) , and proliferating cells (PCNA). Results show that Dacron is more inflamma tory than ePTFE and that there is a segregated macrophage response; the fir st 54 mu m of perigraft tissue were composed predominantly of recruited mac rophages (ED1+) while the more distal tissue consisted of resident macropha ges (ED2+). Proliferating cells were located predominantly in this same 54 mu m perigraft region. In subcutaneous tissue they accounted for 23% of all cells present around Dacron after 3 weeks of implantation and 8% after 5 w eeks. Conversely, cellular proliferation around ePTFE increased from 4% at 3 weeks to 21% at 5 weeks. In adipose tissue, proliferation levels around t he implanted polymers were lower and more similar after 3 and 5 weeks. Seri al sections revealed the coordinate expression of PCNA and ED1 antigens by the same individual cells, suggesting that proliferation is a mechanism use d to perpetuate the chronic inflammatory response. These results suggest a new target for designing treatments to alter inflammation and improve the h ealing associated with these biomaterials. (C) 2000 John Wiley & Sons, Inc.