Inhibition of RNase L enhances the expression efficiency of mRNA-LNPs

mRNA-LNPs offer a promising platform for therapeutic protein expression, however, achieving efficient and sustained translation remains a significant challenge. One of the major barriers to mRNA-LNP efficacy is the activation of innate immune responses that recognize foreign RNA and suppress subsequent protein synthesis. Among these, the OAS-RNase L pathway, involved in degradation of cytoplasmic mRNA, plays a key role. This study examined the impact of RNase L and RNase L blockade on mRNA-LNP expression efficiency. In THP-1 cells, which express high endogenous levels of RNase L, both genetic ablation and pharmacological inhibition of RNase L led to a marked increase in protein expression. In contrast, HeLa cells, which exhibit low RNase L expression, showed minimal response to RNase L inhibition. In human peripheral blood mononuclear cells (PBMCs), RNase L inhibition also enhanced mRNA expression, while blocking other RNA sensors such as TLR7/8, RIG-I, TLR3, or MAVS, did not. Activation of the OAS-RNase L pathway may be driven by double-stranded secondary structure formed by therapeutic mRNA, resulting in mRNA recognition and degradation. RNase L acts as a key post-transcriptional regulator of mRNA stability and translation. Targeting this pathway offers a strategy to improve the performance of mRNA-based therapeutics.