Plasminogen activator-coated nanobubbles targeting cellbound β2-glycoprotein I as a novel thrombus-specific thrombolytic strategy

Haematologica. 2023 Jul 1;108(7):1861-1872. doi: 10.3324/haematol.2022.281505.

Abstract

β2-glycoprotein I (β2-GPI) is a serum protein widely recognized as the main target of antibodies present in patients with antiphospholipid syndrome (APS). β2-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 β2-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 β2-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 β2-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 β2-GPI may represent an efficient and thrombus-specific thrombolytic strategy in both APS-related and APS-unrelated thrombotic conditions.

MeSH terms

  • Animals
  • Antiphospholipid Syndrome*
  • Endothelial Cells
  • Fibrinolytic Agents / pharmacology
  • Fibrinolytic Agents / therapeutic use
  • Mice
  • Rats
  • Thromboembolism*
  • Thrombosis* / drug therapy
  • Thrombosis* / etiology
  • Tissue Plasminogen Activator / pharmacology
  • Tissue Plasminogen Activator / therapeutic use
  • beta 2-Glycoprotein I

Substances

  • Fibrinolytic Agents
  • ferric chloride
  • Tissue Plasminogen Activator
  • beta 2-Glycoprotein I

Grants and funding

Funding: This work was supported by funds from University of Trieste (to PM) and University of Turin (60% to MA and RC). KSJ is a Medical Research Council (MRC) clinical Fellow (MR/R001359/1). The paper was also supported in part by Ricerca Corrente 2019 and 2020 - Ministero della Salute, Italy (to PLM).