Culture of human adult endothelial cells on endarterectomy surfaces

Seeding of endothelial cells on the luminal surface of a sheet model of cold-stored (at 4°C) sheep carotid arteries

Cold-stored arteries are biomaterials that potentially represent an abundant "off-the-shelf" source of vascular grafts for use in vascular surgery. One of the keys to reestablishing the antithrombogenic endothelial cell (EC) lining of cold-stored arterial grafts is to maximize the number of ECs that attach following seeding. In this study, the cold-stored sheep carotid artery is used as a substrate to determine the conditions that maximize EC adherence following seeding. The effect of serum concentration, duration of seeding incubation, seeding density, and period of cold storage on attachment of ECs following seeding of 4-week cold-stored sheep carotid arteries (n = 5 arteries), 8-week cold-stored sheep carotid arteries (n = 5 arteries), and 12-week cold-stored sheep carotid arteries (n = 5 arteries) was examined. Three experiments (serum concentration, time of incubation, and seeding density) were conducted to determine the conditions that maximized the number of cultured sheep carotid artery ECs that attached to cold-stored sheep carotid artery following seeding. A flat sheet model was used. Serum concentration (0%, 10%, 20%, and 30%) in the seeding suspension did not have a significant effect on overall EC adherence on 4-, 8-, and 12-week cold-stored arteries. Time of seeding incubation (30, 60, and 90 min) did not have a significant effect on overall EC adherence on 4-, 8-, and 12-week cold-stored arteries. Seeding density (500,000 cells/ml, 1,000,000 cells/ml, and 2,000,000 cells/ml) had a significant effect (p = 0.036) on overall EC adherence on 4-, 8-, and 12-week cold-stored arteries. The period of cold storage (4, 8, and 12 weeks) of the artery had a significant effect (p = 0.002, p < 0.0001, p < 0.0001 in serum, time, and seeding density experiments, respectively) on overall EC adherence following seeding. Pairwise comparisons of EC adherence revealed the following. In the serum experiment, EC adherence on 4-week cold-stored arteries was significantly greater than on 8-week cold-stored arteries (p = 0.003) and 12-week cold-stored arteries (p = 0.002). This effect was due largely to the significant difference between EC adherence on 4-week and 8-week cold-stored arteries (p = 0.0002) and between EC adherence on 4-week and 12-week cold-stored arteries (p = 0.0091) at 20% serum. In the time experiment, EC adherence on 4-week cold-stored arteries was significantly greater than on 12-week cold-stored arteries (p < 0.0001). In the seeding density experiment, EC adherence on 4-week cold-stored arteries was significantly greater than on 8-week cold-stored arteries (p < 0.0001) and 12-week cold-stored arteries (p < 0.0001). In the same experiment, EC adherence following seeding at a density of 1,000,000 cells/ml and 2,000,000 cells/ml was significantly greater (p = 0.03 and p = 0.02, respectively) than EC adherence following seeding at a density of 500,000 cells/ml. Thus, it was determined that 4-week cold-stored arteries were superior to 8- and 12-week cold-stored arteries in terms of the number of ECs that adhered. It was also determined that a seeding density of 1,000,000 or 2,000,000 cells/ml was superior to a seeding density of 500,000 cells/ml in terms of producing maximal EC attachment. The ideal conditions, from those examined, for maximizing EC attachment to cold-stored arteries were 4 weeks of cold storage, a serum concentration of 20%, a seeding density of 2,000,000 cells/ml, and a duration of incubation of 30-90 min.

Effectiveness of endothelial cell seeding on patency of damaged vascular surfaces in a canine model

The effects of endothelial cell seeding, which is assumed to be an effective technique to improve patency rates of denuded vascular surfaces, were investigated in an experimental model. In this study, after anesthetic induction, jugular veins of 16 dogs were harvested bilaterally. Endothelial cells were extracted enzymatically by collagenase from these veins and were passaged into a culture medium until they grew to a reasonable number. After 3 weeks, dogs were anesthetized again in a similar fashion and bilateral femoral veins were exposed and experimental intimal denudation was performed. Subsequently, one femoral artery was injected with cell solution and the other with saline solution as a control. Two weeks after the injections, arteriographic studies of femoral arteries were performed and arterial specimens were taken for histological evaluation. Our results suggest that endothelial seeding might improve the patency rate in elective but urgent cases in which endarterectomy, percutaneous transluminal angioplasty, or similar vascular procedures are considered.

Production of plasminogen activator inhibitor-1 by human saphenous vein endothelial cells seeded onto endarterectomy surfaces in vitro

PURPOSE

Endothelial cells produce many biologically important factors that may be used as functional markers, including plasminogen activators and their inhibitors (PAI). PAI-1 is a common peptide with a central role in the balance of thrombosis and fibrinolysis in vivo, and its production by vascular endothelial cells has been demonstrated for many in vitro cell lines.

METHODS

The basal rate of PAI-1 release from cultured human adult endothelial cells was studied in both a well-plate-seeding model and after seeding onto human endarterectomy specimens. The effect of nonspecific stimulation with thrombin on PAI-1 release was examined in well-plate cultures. PAI-1 was measured by enzyme-linked immunosorbent assay.

RESULTS

Cultured human saphenous endothelial cells release PAI-1 constitutively at a steady rate, which can be increased in the short term by the addition of thrombin.

CONCLUSION

After seeding onto endarterectomy specimens, seeded endothelial cells release significant amounts of PAI-1, which suggests that they retain functional integrity and may potentially influence thrombosis in vivo after seeding.

Endothelial cell seeding of de-endothelialised human arteries: improvement by adhesion molecule induction and flow-seeding technology

OBJECTIVES

To assess re-endothelialisation of denuded human arteries by two different seeding techniques using adhesion molecule induction and a dynamic flow-seeding.

DESIGN

Prospective, open study.

SETTING

University Department of Cardiovascular Surgery.

MATERIALS AND METHODS

In the first group (I) segments of human common carotid arteries (n = 4) were balloon-denuded, short-time seeded with cultured adult human venous endothelial cells (EC) and exposed to a mock circulation. In the second group (II) (n = 4), EC were incubated with a synthetic RGD peptide (arginine-glycine-aspartate) prior to seeding with the aim of upregulating the cellular adhesion molecules and increasing EC attachment. In the third group (III) (n = 4), EC were seeded not using the common technique of instillating cells and sequentially rotating the graft but by a dynamic flow application. The percentage of EC-covered luminal surface was assessed by image analysis of scanning electron micrographs.

RESULTS

EC attachment was significantly increased in groups II (73%) and III (94%) compared with group I (34%). In group III, a preconfluent monolayer could be established immediately after seeding. One hour of artificial perfusion resulted in no significant EC loss in any of the study groups.

CONCLUSIONS

RGD-peptide preincubation improves EC seeding of biological surfaces. Because of accelerated seeding times it may have good potential for clinical applications. The flow-seeding technology may be indispensable if EC seeding of the vascular surface of complete organ systems is required.