Robust Thrombolytic and Anti-Inflammatory Action of a Constitutively Active ADAMTS13 Variant in Murine Stroke Models.

Advances in our understanding of ADAMTS13 structure, and the conformation changes required for full activity, have rejuvenated the possibility of its use as a thrombolytic therapy. We have tested a novel Ala1144Val ADAMTS13 variant (caADAMTS13) which exhibits constitutive activity, characterised using in vitro assays of ADAMTS13 activity, and greatly enhanced thrombolytic activity in two murine models of ischaemic stroke, the distal FeCl3 MCAo model and tMCAO with systemic inflammation and ischaemia/reperfusion injury. The primary measure of efficacy in both models was restoration of rCBF to the MCA territory which was determined using laser speckle contrast imaging. The caADAMTS13 variant exhibited a constitutively active conformation and a 5-fold enhanced activity against FRETS-VWF73 compared to wild type (wt)ADAMTS13. Moreover, caADAMTS13 inhibited VWF-mediated platelet capture at sub-physiological concentrations and enhanced t-PA/plasmin lysis of fibrin(ogen), neither of which were observed with wtADAMTS13. Significant restoration of rCBF and reduced lesion volume was observed in animals treated with caADAMTS13. When administered 1 h after FeCl3 MCAo the caADAMTS13 variant significantly reduced residual VWF and fibrin deposits in the MCA, platelet aggregate formation and neutrophil recruitment. When administered 4 h after reperfusion in the tMCAo model the caADAMTS13 variant induced a significant dissolution of platelet aggregates and a reduction in the resulting tissue hypoperfusion. The caADAMTS13 variant represents a potentially viable therapeutic option for the treatment of acute ischaemic stroke, amongst other thrombotic indications, due to its enhanced in vitro and in vivo activities that result from its constitutively active conformation.