Kinetics of endothelial cell seeding

Endothelial cell seeding improves patency of small-diameter Dacron grafts and facilitates the development of a complete endothelial flow surface. However, the ideal number of cells relative to the length of graft to be seeded has not been determined. With a canine model previously shown to result in a well-endothelialized graft within 4 to 6 weeks, this study measured the quantity of autogenous endothelial cells labeled with indium 111-oxine that initially adhered to 10 cm long, experimental, porous 4 mm I.D. polytetrafluoroethylene grafts and then calculated their subsequent disappearance following implantation as carotid interposition grafts. Graft radioactivity was monitored with a gamma camera and compared with that of control vials of indium 111 implanted in the same animals. Counts were measured immediately at implantation and for up to 72 hours following restoration of flow. Data were analyzed by linear regression. The mean number of harvested endothelial cells was 6.2 × 10⁵. A mean of 19.8% of the harvested cells were adherent to the grafts initially after seeding. In the first 30 minutes following restoration of flow, there was a rapid loss of these cells to a mean value, which was 70.2% of those initially present. From 30 minutes to 24 hours, cell losses continued at a constant rate of 3.7%/hr (r = -0.922, p < 0.001). Beyond 24 hours, further loss was insignificant. Consequently, approximately 2.72 × 10⁴ cells, or only 4.4% of all cells originally harvested, appear adequate to seed 12.5 cm² of graft. Improvements in the efficiency of the various steps may eventually permit clinical endothelial seeding of longer bypass grafts with very small amounts of available donor veins.