Lipid Nanoparticles (LNPs) made from Cholesterol-Amino-Phosphate (CAP) CAP2 can deliver traditional mRNA and self-amplifying RNA (saRNA) encoding DNA Meiotic Recombinase 1 (Dmc1) protein in spermatocytes. A single injection of CAP2 LNPs–saRNA can produce Dmc1 protein for an extended period and restore spermatid production in the Dmc1 gene knockout mouse model.