RNA interference is a naturally occurring specific method to silence genes with wide potential for treating human disease. Engineered RNA oligonucleotides targeting proprotein convertase subtilisin-kexin type 9 were recently shown to reliably lower LDL cholesterol, with a single injectable dose lasting 6 to 12 months.¹ Applying short interfering RNA (siRNA) therapy to livers via ex vivo machine perfusion before transplantation may open the door to using organs from extended criteria donors that would otherwise be discarded. Treating isolated livers would also reduce costs compared with systemic therapy. We show for the first time that siRNA against the Fas receptor added directly to perfusion solution is uptaken into rat livers during hypothermic (4°C) and normothermic (37°C) perfusion. The Fas receptor expressed in liver signals hepatocytes to apoptose after binding its respective ligand. In mice, reduced FAS expression via siRNA confers protection against chemically induced acute liver failure.² We aim to silence FAS during the ischemic period before transplantation and thus reduce or even reverse graft damage. Transfection into hepatocytes is achieved by coating siRNA with lipid nanoparticles, which facilitate endocytosis across cell membranes and release siRNA into the cytoplasm.³ SiRNA-lipid complexes were delivered in perfusion solution via portal vein cannulation, and distribution was observed with fluorescent confocal microscopy (Figure 1). Full methods are described in Supplemental Materials and Methods (SDC,http://links.lww.com/TP/B651). Further studies will quantify FAS knockdown and the effect of FAS in a rat transplant model. SiRNA therapy during organ machine perfusion is an exciting frontier with transformational potential to improve clinical transplant outcomes.