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

The chronic inflammatory response associated with the abluminal surface of polymeric vascular grafts has been suggested to affect adversely graft neovascularization, the cellular response at the luminal surface of vascular grafts, and overall graft patency. To better understand the source for this chronic inflammation, this study examined two types of macrophages and the amount of cellular proliferation around two widely used graft materials, expanded polytetrafluoroethylene (ePTFE) and polyethyleneterephthalate (PET or Dacron) implanted in the rat for 3 and 5 weeks. Serial sections of explants were analyzed for recruited macrophages (ED1), resident macrophages (ED2), and proliferating cells (PCNA). Results show that Dacron is more inflammatory than ePTFE and that there is a segregated macrophage response; the first 54 micrometer of perigraft tissue were composed predominantly of recruited macrophages (ED1+) while the more distal tissue consisted of resident macrophages (ED2+). Proliferating cells were located predominantly in this same 54 micrometer perigraft region. In subcutaneous tissue they accounted for 23% of all cells present around Dacron after 3 weeks of implantation and 8% after 5 weeks. Conversely, cellular proliferation around ePTFE increased from 4% at 3 weeks to 21% at 5 weeks. In adipose tissue, proliferation levels around the implanted polymers were lower and more similar after 3 and 5 weeks. Serial sections revealed the coordinate expression of PCNA and ED1 antigens by the same individual cells, suggesting that proliferation is a mechanism used to perpetuate the chronic inflammatory response. These results suggest a new target for designing treatments to alter inflammation and improve the healing associated with these biomaterials.