Vitrification-warming delays preimplantation development and impairs mitochondrial function and cytoplasmic lattices...

Vitrification and warming of human embryos have become standard procedures in assisted reproduction over the past two decades. Although generally considered safe, their full impact on embryo development remains unclear. Epidemiological studies have raised concerns about differences in birth weight and long-term health outcomes between newborns from fresh versus frozen embryo transfers. Here, we present a descriptive study using mouse embryos to investigate the impact of vitrification and warming on developmental kinetics, mitochondrial function, and cytoplasmic lattice integrity. Time-lapse imaging revealed significant developmental delays across all preimplantation stages in vitrified embryos. Additionally, mitochondrial distribution, volume, and membrane potential exhibited signs of impairment. Ultrastructural analysis identified ruptured mitochondrial membranes, disrupted cytoplasmic lattices during early cell divisions, and underdeveloped mitochondrial cristae at the blastocyst stage. We hypothesize that embryo vitrification and warming disrupt mitochondrial function and compromise cytoplasmic lattices integrity, ultimately contributing to developmental delays in preimplantation mouse embryos.