OC 46.4 - von Willebrand Factor-targeting thrombolysis to overcome tissue Plasminogen Activator resistance in vivo

Monday, July 11, 2022

3:30 PM – 3:45 PM

Location: ExCel Center, ICC Capital Suite Room 10&11

Presentation Format: In-Person

Co-Author(s)

Mv

Marc van Moorsel, MSc

PhD Candidate
UMC Utrecht
Utrecht, Utrecht, Netherlands
Coen Maas, PhD

Associate Professor
Department of CDL Research, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
Utrecht, Utrecht, Netherlands

Presenting Author(s)

Steven de Maat, PhD

Assistant Professor
Department of CDL Research, University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands.
Utrecht, Utrecht, Netherlands

Background: Intravenous administration of recombinant human tissue Plasminogen Activator (rh-tPA) is the standard-of-care for pharmacological treatment of Acute Ischemic Stroke (AIS), although it is only effective in < 33% of patients. rh-tPA requires binding to fibrin to activate plasminogen and initiate thrombolysis, limiting its applicability to fibrin-dependent thrombi.. In contrast, Microlyse is a thrombolytic agent that targets vWF rather than fibrin to initiate plasminogen activation. Microlyse effectively attenuates symptoms in a mouse model for thrombotic thrombocytopenic purpura, a VWF-driven form of microvascular thrombosis.

Aims: To compare rh-tPA with Microlyse in two AIS mouse models that are either fibrin- or vWF-dependent.

Methods: AIS was induced in the middle cerebral artery (MCA) by either direct infusion of thrombin or by topical application of FeCl3 (Fig. 1). Full vascular occlusion (stable for >20 minutes) was confirmed Laser Doppler flowmetry. Next, mice were intravenously administered vehicle, 0.8mg/kg Microlyse or 10mg/kg tPA by bolus-injection in- (10% of total dose) and infusion for 40 minutes via (90% of total dose) in the tail vein. Brain tissue reperfusion was monitored with Laser Speckle imaging, starting 10 minutes before- until 10 minutes after treatment. After 24 hours, the extent of ischemic injury was investigated by T2w-MRI.

Results: In the fibrin-dependent model, both rh-tPA (35.8±17.1%; p=0.001) and Microlyse (39.3±13.1%; p< 0.0001) increased early reperfusion (T=70min; vehicle=15.6±7.5%). Consequently, both rh-tPA (18.9±11.2 mm3; p=0.033) and Microlyse (16.1±13.9 mm3; p=0.018) reduced lesion volumes, indicating lowered ischemic injury (vehicle=26.6±5.6 mm3). In the vWF-dependent model, rh-tPA (7.6±8.8%; p=0.216) nor Microlyse (16.3±13.9%; p=0.151) increased early reperfusion (vehicle=10.1±7.9%). However, only Microlyse (13.9±11.4 mm3; p< 0.001) but not rh-tPA (23.6±11.1 mm3; p=0.188) significantly reduced lesion volumes (vehicle=30.3±10.9 mm3).

Conclusion(s): Altogether, whereas rh-tPA only reduced ischemic injury in a fibrin-dependent AIS model, Microlyse was effective in both models (table 1), supporting applicability irrespective of the thrombus composition.