Enhancing LipidNanoparticle-Mediated Circular RNAand mRNA Expression in the Placenta through Inhibition of IFNAR-JAK-STATSignaling

The placenta has emerged as a promising target for RNA lipid nanoparticle (LNP)-based therapies to treat obstetric complications, yet efficient extrahepatic RNA transfection remains a challenge. Here, we identify innate immune signaling as a regulator of placental RNA translation and demonstrate that inhibition of IFN-α/β receptor (IFNAR) and JAK-STAT signaling enhances LNP-mediated transgene expression in the placenta for both messenger RNA (mRNA) and circular RNA (circRNA). While a placenta-tropic LNP enabled robust and durable circRNA expression in trophoblasts in vitro, circRNA translation was substantially decreased in vivo compared to mRNA in pregnant mice. Inhibition of IFNAR-JAK-STAT signaling enhanced circRNA translation up to 12-fold in maternal organs and increased circRNA and mRNA translation in the placenta up to 17.5- and 4-fold, respectively. JAK-STAT inhibition also enhanced translation of therapeutically relevant VEGF-encoding circRNA and mRNA in pregnant mice, suggesting innate immune modulation as a broadly applicable strategy to improve RNA therapeutics during pregnancy.