Testicular mRNA‐LNP Delivery: A Novel Therapy for Genetic Spermatogenic Disorders

ABSTRACT Uniform testicular maturation arrest is a severe form of male infertility characterized by the presence of germ cells that do not complete spermatogenic development. It is usually caused by meiotic arrest with genetic variants and is difficult to treat via drugs or surgery. mRNA‐lipid nanoparticle (LNP) delivery is a promising therapeutic option for maturation arrest with monogenic variants via protein replacement therapy. Herein, a spermatocytes‐tropic LNP (Pool1‐LNP3) was identified via a library of 30 ionizable lipids screening. And in vivo delivery of this novel LNP composition using rete testis microinjection was shown to be high spermatocytes targeting with high transfection efficiency. Thereafter, it was revealed that in vivo delivery of Pool1‐LNP3 encapsulating Msh5 mRNA could promote crossover formation and restore spermatogenesis in Msh5 ^D486Y/D486Y mouse models with DNA double‐strand break (DSB) recombination defects. Notably, the offspring without genomic integration was born using intracytoplasmic sperm injection (ICSI) derived from the rescue of Msh5 ^D486Y/D486Y mouse and embryo transfer. In addition, it was demonstrated that Maps mRNA‐LNP3 recovered spermatogenesis in Maps KO mouse with meiotic arrest. Altogether, these findings suggested that this spermatocyte‐tropic mRNA‐LNP delivery could become a viable and applicable strategy for the treatment of spermatogenic disorders with genetic defects, providing a foundation for future clinical application.