Factor XII silencing using siRNA prevents thrombus formation in a rat model of extracorporeal life support

Abstract Background: Heparin anticoagulation increases the bleeding risk during extracorporeal life support (ECLS) and thus must be limited and monitored carefully. This study determined whether factor XII (FXII) silencing using short interfering RNA (siRNA) can provide ECLS circuit anticoagulation, maintain normal tissue coagulation, and reduce the need for careful anticoagulation monitoring. Methods: Adult male, Sprague-Dawley rats were randomized to four groups (n = 3 each) based on anticoagulant: (1) no anticoagulant, (2) heparin, (3) FXII siRNA, or (4) non-targeting siRNA. In group 1, no anticoagulant was administered. In group 2, heparin was administered intravenously before and during ECLS at an activated clotting time of 180–250 seconds. In groups 3 and 4, siRNA was administered intravenously three days before the initiation of ECLS via lipidoid nanoparticles. The rats were placed on pumped, arteriovenous ECLS with a small 3D-printed mock-oxygenator, and blood flow was maintained at 2 mL/min for eight hours or until the blood flow resistance reached three times its baseline resistance. Results: A single dose of 3 mg/kg siRNA led to a reduction of plasma FXII to 26% ± 3% (mean +/- standard error) of baseline levels three days after treatment. Without anticoagulant, mock-oxygenator resistance tripled within 7 ± 2 minutes. The resistance in the heparin group was significantly ( p < 0.05) elevated in the first hour of the experiment before returning to a lower, normal value for the rest of the experiment. The resistance in the FXII siRNA group did not change significantly with time ( p = 0.94). There were no significant differences in resistance or mock-oxygenator thrombus volume between the FXII siRNA and the heparin groups ( p > 0.99). However, the bleeding time in the FXII siRNA group (3.4 ± 0.6 minutes) was significantly shorter than that in the heparin group (5.5 ± 0.5 minutes, p < 0.05). Conclusions: FXII silencing using siRNA provided simpler anticoagulation of ECLS circuits with reduced bleeding risk as compared to heparin.