Exceptional Uptake, Limited Protein Expression: Liver Macrophages Lost in Translation of Synthetic mRNA.

Most gene therapies exert their actions via manipulation of hepatocytes (parenchymal cells) and the reasons behind the suboptimal performance of synthetic mRNA in non-parenchymal cells (NPC) such as Kupffer cells (KC), and liver macrophages, remain unclear. Here, the spatio-temporal distribution of mRNA encoding enhanced green fluorescent protein (Egfp), siRNA, or both co-encapsulated into lipid nanoparticles (LNP) in the liver in vivo using real-time intravital imaging is investigated. Although both KC and hepatocytes demonstrate comparable high and rapid uptake of mRNA-LNP and siRNA-LNP in vivo, the translation of Egfp mRNA occurs exclusively in hepatocytes during intravital imaging.