Study Of Prosthetic Graft Healing In A Primate Model Utilizing Autologous Indium-111 Labeled Platelets

In a primate model (Papio papio) whose coagulation system is similar to man, we have previously shown that Indium-111 labeled platelets (IN¹¹¹) are taken up acutely in the region of a synthetic graft. IN¹¹¹ uptake was maximal by 48 hours post-graft implantation and was no greater at 7 days. The purpose of the present study was to detail platelet-graft dynamics during later phases after graft implantation. IN¹¹¹ platelets were infused intravenously into animals two weeks after implantation of a 4 mm synthetic carotid artery interposition graft. The radioactivity in the region of the graft was contrasted to a comparable blood volume in a control artery and this activity was calculated by a computer algorithm which accounted for isotopic decay and tissue attenuation. Radioactivity was expressed as % of the total injected dose of IN¹¹¹ (%TID). The difference (%TID on graft - %TID on control artery) was calculated to determine platelet-graft associated activity. Histologic sections were subsequently examined to correlate graft morphology with in vivo dynamic changes. Results: The mean uptake of IN¹¹¹ platelet associated activity during the early post graft implantation phase ( <7 days) was 0.22%. By contrast at 14 days there was no appreciable uptake of IN¹¹¹ platelets within the region of the graft. Histologic sections of selected graft specimens removed at 2 weeks demonstrated no significant endothelialization. These findings may have important pharmacologic implications with respect to the platelet’s role in early synthetic graft healing.