VWF-targeted thrombolysis to overcome rh-tPA resistance in experimental murine ischemic stroke models.

Recombinant human tissue plasminogen activator (rh-tPA) is an important thrombolytic agent for treatment of acute ischemic stroke. It requires fibrin binding for plasminogen activation. In contrast, Microlyse, a novel thrombolytic agent, requires von Willebrand factor (VWF) binding for plasminogen activation. We compared rh-tPA with Microlyse, administered 20 minutes after inducing thrombosis, in 2 randomized blinded acute ischemic stroke mouse models. Thrombosis was induced in the middle cerebral artery with different experimental triggers. Where thrombin infusion generates fibrin-rich thrombi, topical FeCl3 application generates platelet-rich thrombi. In the fibrin-rich model, both rh-tPA and Microlyse increased cortical reperfusion (determined by laser speckle imaging) 10 minutes after therapy administration (35.8 ± 17.1%; P = .001 39.3 ± 13.1%; P < .0001; 15.6 ± 7.5%, respectively, vs vehicle). In addition, both thrombolytic agents reduced cerebral lesion volume (determined by magnetic resonance imaging) after 24 hours (18.9 ± 11.2 mm3; P = .033; 16.1 ± 13.9 mm3; P = .018; 26.6 ± 5.6 mm3, respectively, vs vehicle). In the platelet-rich model, neither rh-tPA nor Microlyse increased cortical reperfusion 10 minutes after therapy (7.6 ± 8.8%; P = .216; 16.3 ± 13.9%; P = .151; 10.1 ± 7.9%, respectively, vs vehicle). However, Microlyse, but not rh-tPA, decreased cerebral lesion volumes (13.9 ± 11.4 mm3; P < .001; 23.6 ± 11.1 mm3; P = .188; 30.3 ± 10.9 mm3, respectively, vs vehicle). These findings support broad applicability of Microlyse in ischemic stroke, irrespective of the thrombus composition.