LIMITATIONS OF IN-VITRO LABELING OF ENDOTHELIAL-CELLS WITH IN-111 OXINE

Indium-111 oxine labeling is widely used as a marker of endothelial ce ll attachment to vascular prostheses. The long term effect of labeling human adult endothelial cells (HAECs) with this isotope has not been determined. In this study the viability of labeled HAECs, leakage of i sotope from labeled cells and adherence of circulating isotope to fibr onectin coated prostheses were investigated over 24 h. The effect of i ncubation time on labeling efficiency was also assessed. There were si gnificant differences in cell viability between the labeled and unlabe led groups beyond 4 h (p < 0.005, 2-tailed, unpaired t-test). In the c ontrol group cell numbers increased by 42% while in the labeled group this had decreased by 20% at 24 h. Spontaneous leakage increased with time but was maximal in the first 2 h. Adherence of circulating isotop e to fibronectin coated expanded polytetrafluoroethylene (ePTEE) graft s was minimal but was significantly greater to gelatin impregnated dac ron (GEL-SEAL) beyond 1 hour (p < 0.05). Incubation times greater than 5 minutes during labeling do not significantly improve labeling effic iency, and may contribute to toxicity by prolonging exposure to oxine. Indium-111 oxine labeling of HAECs is a suitable technique for acute studies of endothelial cell kinetics up to 4 h, but its use in chronic studies may lead to significant underestimations of cell retention.