ENHANCED IN-VIVO ANTITHROMBOTIC EFFECTS OF ENDOTHELIAL-CELLS EXPRESSING RECOMBINANT PLASMINOGEN ACTIVATORS TRANSDUCED WITH RETROVIRAL VECTORS

Background The effects of regulating endothelial cell (EC) plasminogen activator production on thrombus accumulation in vivo are incompletel y understood. By overexpressing plasminogen activators in ECs via gene transfer, the hypothesis was tested that increased levels of plasmino gen activators inhibit the accumulation of thrombus in vivo. Methods a nd Results Cultured baboon ECs transduced with human cDNAs for wild-ty pe tissue plasminogen activator (TPA) or for glycosylphosphatidylinosi tol-anchored urokinase-type plasminogen activator (a-UPA) were seeded onto collagen-coated segments of vascular graft (collagen segments) an d exposed overnight to flow using an in vitro perfusion circuit. The a ntigenic levels of TPA and UPA each increased 10-fold in the media per fusing the corresponding transduced ECs compared with untransduced ECs (P less than or equal to.05 in both cases). In baboons the antithromb otic effects of TPA-transduced or a-UPA-transduced ECs were measured a s In-111-platelet deposition and I-125-fibrin accumulation on collagen segments bearing sparsely attached ECs (transduced versus untransduce d) inter posed in exteriorized arteriovenous femoral shunts. Platelet- rich thrombus formed on the collagen segments with fibrin-rich thrombu s propagated distally. The presence of TPA-transduced or a-UPA-transdu ced ECs on collagen segments at a density of 25 000 ECs/cm(2) decrease d In-111-platelet deposition and I-125-fibrin accumulation on collagen surfaces compared with untransduced ECs present at equivalent density (P<.05 for platelet deposition with TPA-transduced ECs and P<.05 for platelet deposition on the propagated tail, as well as fibrin accumula tion on the graft with a-UPA-transduced ECs). The systemic levels of f ibrinopeptide A, thrombin-antithrombin complex, D-dimer, and both loca l and systemic levels of TPA and UPA were not increased by transduced ECs compared with untransduced ECs. The focal antithrombotic effects o f transduced ECs appear to be due to local enhancement of thrombolysis . Conclusions ECs transduced with recombinant TPA and a-UPA enhance lo cal antithrombotic activity in vivo. This strategy of attaching transd uced ECs overexpressing plasminogen activators may be therapeutically useful by preventing thrombo-occlusive failure of implanted cardiovasc ular devices or mechanically denuded vessels.