Plasminogen activator-coated nanobubbles targeting cell- bound & beta; 2-glycoprotein I as a novel thrombus-specific thrombolytic strategy

132-glycoprotein I (132-GPI) is a serum protein widely recognized as the main target of antibodies present in patients with antiphospholipid syndrome (APS). 132-GPI binds to activated endothelial cells, platelets and leukocytes, key players in thrombus formation. We developed a new targeted thrombolytic agent consisting of nanobubbles (NB) coated with recombinant tissue plasminogen activator (rtPA) and a recombinant antibody specific for cell-bound 132-GPI. The therapeutic efficacy of targeted NB was evaluated in vitro, using platelet-rich blood clots, and in vivo in three different animal models: i) thrombosis developed in a rat model of APS; ii) ferric chloride-induced mesenteric thrombosis in rats, and iii) thrombotic microangiopathy in a mouse model of atypical hemolytic uremic syndrome (C3-gain-of-function mice). Targeted NB bound preferentially to platelets and leukocytes within thrombi and to endothelial cells through 132-GPI expressed on activated cells. In vitro, rtPA-targeted NB (rtPA-tNB) induced greater lysis of platelet-rich blood clots than untargeted NB. In a rat model of APS, administration of rtPA-tNB caused rapid dissolution of thrombi and, unlike soluble rtPA that induced transient thrombolysis, prevented new thrombus formation. In a rat model of ferric chloride triggered thrombosis, rtPA-tNB, but not untargeted NB and free rtPA, induced rapid and persistent recanalization of occluded vessels. Finally, treatment of C3-gain-of-function mice with rtPA-tNB, that target 132-GPI deposited in kidney glomeruli, decreased fibrin deposition, and improved urinalysis data with a greater efficiency than untargeted NB. Our findings suggest that targeting cell-bound 132-GPI may represent an efficient and thrombus-specific thrombolytic strategy in both APS-related and APS-unrelated thrombotic conditions.

Automated summary

A new targeted thrombolytic agent consisting of nanobubbles coated with recombinant tissue plasminogen activator (rtPA) and a recombinant antibody specific for cell-bound 132-GPI was developed. The targeted nanobubbles exhibited greater lysing capabilities for platelet-rich blood clots and induced rapid and persistent recanalization of occluded vessels in animal models. This study suggests that targeting cell-bound 132-GPI may be an effective and thrombus-specific thrombolytic strategy.