Abstract Number: OC 02.2
Meeting: ISTH 2021 Congress
Background: Among its roles in numerous other systems, plasminogen is the primary driver of fibrinolysis. Plasmin inhibitors such as TXA have a short half-life, while murine models of plasminogen deficiency show deleterious phenotypes by five months of age. siRNA targeting plasminogen (siPLG) may provide a more flexible tool to knock down plasminogen and modulate fibrinolysis long-term.
Aims: To develop a tool to reduce plasminogen levels and achieve long-lasting control of fibrinolysis in diverse models.
Methods: Lipid nanoparticles were used to deliver siPLG in wild-type mice and dogs. To evaluate efficacy of knockdown, blood and tissues were collected for protein analysis, mRNA quantification, and coagulation assessment by thromboelastography. After eight months of sustained knockdown, mice were assessed for drug toxicity, and adverse effects of plasminogen knockdown, including fibrin deposition and periodontal bone loss. In dogs, a dose-titration study was performed to compare efficacy, duration of knockdown, and toxicity.
Results: Doses of 1.0 and 0.054 mg siRNA / kg body weight in mice and dogs, respectively, caused >90% knockdown of plasminogen for three weeks, and resulted in prolonged clot stability ex vivo (Figure 1).
Periodontal bone loss and fibrin deposition in the liver, pathological phenotypes that develop in plasminogen deficient mice by five months of age, were not observed in mice after eight months of plasminogen knockdown.
In dogs, a transient spike in liver toxicity markers (ALT, ALP) was observed; the intensity and duration of which could be reduced by decreasing the dose of siRNA. At the lowest doses tested, the efficacy of knockdown was not diminished, although the duration of knockdown was shortened.
Conclusions: siRNA targeting plasminogen is an effective and long-lasting tool to control fibrinolysis. In mice, long-term plasminogen knockdown does not show adverse effects associated with knockout. This work also represents the first use and optimization of lipid nanoparticles in canine models.
To cite this abstract in AMA style:W Strilchuk A, Leung J, S Hur W, Abrahams S, M Silva L, H Bugge T, R Cullis P, J Flick M, C Nichols T, J Kastrup C. Controlled Long-term Knockdown of Plasminogen in Mice and Dogs using siRNA: Assessment of Phenotype and Toxicity [abstract]. Res Pract Thromb Haemost. 2021; 5 (Suppl 2). https://abstracts.isth.org/abstract/controlled-long-term-knockdown-of-plasminogen-in-mice-and-dogs-using-sirna-assessment-of-phenotype-and-toxicity/. Accessed December 11, 2023.
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