THE EFFECTS OF POROSITY ON ENDOTHELIALIZATION OF EPTFE IMPLANTED IN SUBCUTANEOUS AND ADIPOSE-TISSUE

Healing of biomaterial implants varies depending on the type and struc ture of material and the tissue surrounding the implant. In this study we examined structural differences of 30 mu m, 60 mu m and 100 mu m e xpanded polytetra-fluoroethylene (ePTFE) using scanning electron micro scopy, and we also investigated differences in healing for these three different porosity ePTFE grafts implanted within subcutaneous tissue and adipose tissue. Scanning electron microscopic examination of 30 mu m, 60 mu m, and 100 mu m ePTFE revealed structural differences and di fferences in fiber density within the internodal space. Circular patch es (6 mm in diameter) of 30 mu m ePTFE were implanted within subcutane ous tissue and epididymal fat pads of male Sprague-Dawley rats. After 5 weeks, the implants were removed and analyzed for fibrous capsule fo rmation, endothelialization, and for activated monocytes and macrophag es in association with the material. Histological evaluation revealed dense fibrous capsule formation surrounding only the 30 mu m ePTFE sub cutaneous implants. From immunohistochemistry data obtained, we genera ted an Endothelialization Index (measure of neovascularization) and a Monocyte/Macrophage Index (measure of inflammatory response) for each sample. Consistently, 69 mu m ePTFE had the greatest Endothelializatio n Index at both implant sites while 100 mu m ePTFE generally had the l argest values for the Monocyte/Macrophage Index. These data indicate t hat both the structure of the material and the site of implant influen ce the healing characteristics of ePTFE and suggest that activated mon ocytes and/or macrophages associated with the implant may inhibit endo thelialization of ePTFE. (C) 1997 John Wiley & Sons, Inc.