No abstract

Compatibility with endothelial cell attachment and growth appears to be an important requisite of vascular prosthetic materials, possibly influencing thrombosis, pseudointimal hyperplasia, and accelerated atherosclerosis at the site of blood-material interaction. Since deposition of pyrolytic carbon (PC) on prosthetic surfaces has been associated with enhanced hemocompatibility, in the present study we assessed whether a thin layer (0.5 microns) of PC deposited onto materials such as knitted Teflon and Dacron enhanced endothelial cell attachment and growth. Cultured human umbilical vein endothelial cells (HUVEC) were seeded at a density of 4.5 x 10(4) cells/cm2 on PC-coated and uncoated grafts. In order to quantify endothelial cell attachment on the fabrics, the area of Teflon and Dacron fabrics covered by endothelial cells was estimated on day 2 after seeding using the point counting method in scanning electron micrographs. Subsequently, on days 2 and 4 after seeding, endothelial cell proliferation was measured both as number of endothelial cells and as total proteins of the endothelial cells covering the fabrics. On day 2 endothelial cell growth on PC-coated fabrics was greater (mean +/- SE; area 42.3 +/- 9.9 mm2, n = 6; cell number 3.9 x 10(4) +/- 3.03 x 10(3) cells, n = 4; total proteins 14.9 +/- 1.2 micrograms, n = 4) than on uncoated fabrics (area 10.6 +/- 4.6 mm2, n = 6; cell number 2.9 x 10(4) +/- 4.3 x 10(3) cells, n = 4; total proteins 11.3 +/- 1.7 micrograms, n = 4; P less than 0.001, less than 0.05 and less than 0.05, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

No abstract

5-lipooxygenase products have been identified from a variety of cells and may play a role in the progression of atherosclerosis and in its clinical manifestations (spasm, thrombosis). We investigated whether human vascular fragments, freshly obtained at surgery, are able to produce leukotriene (LT) B4, a definite end product of 5-lipooxygenase, provided with biological activity. Fragments obtained from human saphenous veins (n=21) or aorta (fibrous plaques, n=15, atheromas, n=16) were incubated in buffer at 37°C with mechanical agitation sequentially in the absence (15 min) and in the presence (15 min) of 10 jjM calcium ionophore A-23187. At the end of each incubation, the buffer was sampled to be assayed by a specific radioimmunassay (RIA) for LTB4 (sensitivity 4.3+0.9 pg). Validation of the assay was performed by comparison with a chemotactic bioassay in Boyden chambers, by interpolation of a standard curve evaluating the chemotactic response of neutrophils to a standard LTB4 preparation. RIA resulted the only practicable method to detect concentrations lower than 2.5 ng/ml, compared both to bioassay and to HPLC, all three performed in the incubation media from 8 vascular fragments. Incubations were also performed in a chamber with selective exposure of the endothelial surface in order to detect possible production of LTB4 on the luminal site of the vessel. Both unstimulated and ionophore-stimulated LTB4 were higher (P< 0.01) in atheromas (2.7±1.2 and 6.3±1.8) than in fibrous plaques (0.51±0.22 and 1.19±0.38) or saphenous veins (0.74±0.34 and 3.07±1.39) (ng/g wet weight, mean±SD). Detectable spontaneous and stimulated LTB4 productions were also found in the incubation media of the chamber with atheromas (40±14 and 324±85 pg/cm2 area, respectively). Histology of the fragments confirmed a higher cellularity (macrophages, atherocytes) in atheromas as compared to fibrous plaques and veins. The human vascular wall is a definite site of 5-lipooxygenase activity, possibly arising from white cell infiltration. LTB4 production, able to reach the inner vessel surface and the blood stream, is a possible factor in the progression of the lesion by increasing vascular permeability or recruiting white blood cells.