Mechanisms of healing in synthetic grafts.

In previous baboon studies we have shown that porous (60 micron mean internodal distance) polytetrafluoroethylene (PTFE) grafts heal by ingrowth of endothelium and smooth muscle cells from the adjacent artery and from capillaries penetrating through the interstices of the graft. However, porous grafts (principally made of Dacron) in humans do not heal. This has been attributed to a wound healing deficiency in humans; however, it might be due to an inhibitory effect of the Dacron itself. To examine the latter possibility, we undertook this study to compare the healing of 4 mm internal diameter porous Dacron grafts (USCI, Sauvage Filamentous Knitted) with that of Gore-Tex 60 micron PTFE grafts in baboons (the latter graft not available for clinical use). The grafts were harvested at 2, 4, and 12 weeks and assessed for (1) percentage of endothelial coverage, (2) endothelial cell (EC) proliferation (thymidine labeling index), (3) intimal area, and (4) smooth muscle cell (SMC) proliferation (thymidine labeling index). The PTFE grafts at all three time points were fully covered, whereas only one of five Dacron grafts was completely covered at 12 weeks. The intima of the PTFE grafts consisted of ECs and SMCs, whereas that of the Dacron grafts contained ECs and SMCs as well as focal accumulations of thrombus. The intimal cross-sectional areas in the Dacron grafts (3.0 +/- 1.2 mm2) were significantly greater than in the PTFE grafts (0.8 +/- 0.6 mm2) at 4 weeks; there was no difference at 12 weeks (Dacron, 2.6 +/- 2.3 mm2 and PTFE, 3.0 +/- 2.5 mm2).(ABSTRACT TRUNCATED AT 250 WORDS)