Low-density polethylene disks with smooth or course surfaces were implanted
in the abdominal wall of rats, and the tissue response was evaluated after
1, 6, or 12 weeks. Cell damage was detected by two different methods. Cell
s with increased membrane permeability could be identified using fluorescen
ce microscopy by injection of propidium iodide prior to the killing of the
rats. Second, cell death was verified by detection of DNA fragmentation. At
1 week a considerable number of the interfacial cells was stained with pro
pidium iodide. Propidium-iodide-positive cells also were enriched at the ed
ges of the disks irrespective of surface texture. The numbers of positive i
nterfacial cells decreassed markedly over time. Cells with DNA fragmentatio
n initially displayed a scattered distribution; at later time points they a
ppeared mainly in the outer portion of the enveloping capsule. The reactive
capsule was thicker for the smooth surface, and there was a positive corre
lation between capsule thickness and propidium-iodide-positive cells at ear
lier implantation periods. The results suggest that the thickness of the re
active capsule is related to the extent of cell necrosis. It is suggested t
hat the major initiator for this cell necrosis is mechanical shear since ce
ll necrosis was found mainly in areas where mechanical shear could be expec
ted. (C) 1999 John Wiley & Sons, Inc.