mRNA-LNP hydrogels promote skeletal muscle regeneration in situ.

Skeletal muscle has an innate capacity for self-regeneration, but may permanently lose its structure and function following extensive injury. Herein, we develop injectable biocomposite hydrogels embedded with mRNA-loaded lipid nanoparticles for skeletal muscle regeneration. Through construction and screening of a combinatorial library of aromatic ring-based ionizable lipids with varying aliphatic chain lengths and substitution patterns, we identify a lead lipid featuring two n-dodecane chains tethered to the meta position of benzenedimethanamine for efficient mRNA delivery. Embedding the top-performing mRNA nanoformulations in thermosensitive polyethylene-polypropylene glycol hydrogel scaffolds allows mRNA release and subsequent mRNA translation in situ. The implantation of hydrogel networks carrying lipid nanoparticles-encapsulated therapeutic mRNA encoding human nicotinamide phosphoribosyltransferase into injury sites promotes substantial vascularized and innervated muscle formation, accompanied by reduced fibrosis in a rat model of volumetric muscle loss, which provides a potential therapeutic option for muscle regeneration.