TISSUE FACTOR EXPRESSION BY CELLS USED FOR SODDING OF PROSTHETIC VASCULAR GRAFTS

Sodding of vascular grafts involves coating the biomaterial with cells prepared from collagenase-digested fat tissue after removal of the ad ipocytes by centrifugation. The goal of this study was to investigate the staining characteristics of the sodding cells as well as their abi lity to express the procoagulant protein tissue factor, and to compare these findings to those found with extensively purified microvascular endothelial cells (MEC) prepared from similar tissue. Sodding cells a nd MEC, isolated using immunomagnetic separation with anti-PECAM antib odies, were prepared from liposuction material and endothelial-specifi c staining was compared. The expression of tissue factor on these cell s was examined using both an ELISA and a chromogenic assay to assess t he rate of generation of factor Xa. Sodding cells expressed significan tly more tissue factor than the unstimulated MEC in which the expressi on was undetectable (sodding cells 2466 +/- 830 pg/mL, P < 0.05). Ther e was no further increase in tissue factor expression in the sodding c ells with stimulation with lipopolysaccharide (LPS); however, purified MEC expressed significantly more tissue factor after exposure to LPS (1247 +/- 356 pg/mL, P < 0.05). These results were confirmed by the de termination of procoagulant activity of the cells whereby the procoagu lant activity on unstimulated MEC was significantly less than that fou nd after stimulation of these cells, and it was also less than stimula ted and unstimulated sodding cells (absorbance at 405 nm: 0.423 +/- 0. 125, unstimulated MEC; 1.000 +/- 0.438, stimulated MEC; 1.129 +/- 0.39 6, unstimulated sodding cells; 1.171 +/- 0.254, stimulated sodding cel ls, P < 0.05). Staining of these two cell types also demonstrated sign ificant uptake of acetylated LDL (Ac-LDL) in the purified MEC which wa s essentially absent in the sodding cells. Further, vWf staining was f ound to a greater degree in the purified MEC than in the sodding cells . These experiments demonstrated that the cells prepared for cell sodd ing express large amounts of tissue factor. The sodding cells do not s tain for antigens known to be specific for endothelial cells, whereas MEC do and therefore the concentration of endothelial cells in the sod ding cells is small. The significance of the tissue factor expression on the surface of sodded grafts is not yet known. (C) 1997 Academic Pr ess.