Biodistribution of Small Interfering RNA at the Organ and Cellular Levels after Lipid Nanoparticle-mediated Delivery

Abstract

Chemically stabilized small interfering RNA (siRNA) can be delivered systemically by intravenous injection of lipid nanoparticles (LNPs) in rodents and primates. The biodistribution and kinetics of LNP–siRNA delivery in mice at organ and cellular resolution have been studied using immunofluorescence (IF) staining and quantitative polymerase chain reaction (qPCR). At 0.5 and 2 hr post tail vein injection of Cy5-labeled siRNA encapsulated in LNP, the organ rank-order of siRNA levels is liver > spleen > kidney, with only negligible accumulation in duodenum, lung, heart, and brain. Similar conclusions were drawn by using qPCR to measure tissue siRNA levels as a secondary end point. siRNA levels in these tissues decreased by more than 10-fold after 24 hr. Within the liver, LNPs delivered siRNA to hepatocytes, Kupffer cells, and sinusoids in a time-dependent manner, as revealed by IF staining and signal quantitation methods established using OPERA/Columbus software. siRNA first accumulated in liver sinusoids and trafficked to hepatocytes by 2 hr post dose, corresponding to the onset of target mRNA silencing. Fluorescence in situ hybridization methods were used to detect both strands of siRNA in fixed tissues. Collectively, the authors have implemented a platform to evaluate biodistribution of siRNA across cell types and across tissues in vivo, with the objective of elucidating the pharmacokinetic and pharmacodynamic relationship to guide optimization of delivery vehicles.

Mechanisms of Nanoparticle-Mediated siRNA Transfection by Melittin-Derived Peptides

“…IVIS imaging of resected organs reveals minimal uptake in traditional clearance organs such as the liver and spleen, but suggest renal clearance, as previously observed with some polyplexes and lipoplexes. 62–63 The shift in clearance away from the liver and spleen suggests a potential role for albumin coating in protecting p5RHH/siRNA nanoparticles from opsonization in accordance with albumin’s previously described ability to act as a disopsonin. 64–65 …”

Technologies for Investigating the Physiological Barriers to Efficient Lipid Nanoparticle–siRNA Delivery

“…3). The majority of Cy5-labeled siRNA was trapped in sinusoids at 0.5 hr after intravenous injection and translocated into hepatocytes at 2 hr, as observed by collagen IV-outlined sinusoids in mouse liver sections (Shi et al 2011). The extrahepatic distribution of LNP-siRNA has also been reported in tumor xenograft models (Liu et al 1992;Medarova et al 2007;Li SD and Huang 2009;Schadlich et al 2011), monocytes (Leuschner et al 2011), and peritoneal macrophages and splenic dendritic cells (Basha et al 2011).…”

“…The drawbacks are low throughput, inability to detect metabolites, and difficulty in achieving precise quantification of fluorescence intensity on IF-stained tissue sections. There are examples of applying such histological methods to investigate siRNA deposition in the liver (Shi et al 2011), tumor (Yoshizawa et al 2008;Mikhaylova et al 2009), lung (Tayyari et al 2011), or even subcellular compartments (Akita et al 2010;Basha et al 2011;Pittella et al 2011). …”

RNA interference-based technology: what role in animal agriculture?

“…The relative difficulty of gene silencing with exogenous siRNA varies greatly across organs. The liver, kidneys, spleen, and phagocytic cells can be affected by many delivery formulations, with little or no targeting required (Shi et al 2011). Although many other organs are difficult to target with systemic siRNA administration, there has been some success in targeting muscle tissue (Kinouchi et al 2008) and adipocytes (Won et al 2014).…”