Effects of light wavelength on oocyte maturation, parthenogenesis, and parthenogenetic embryo development in pigs

Assisted reproductive technologies (ART) to generate developmentally competent oocytes necessitates light exposure due to the use of microscopes. Previous studies in several species have reported that the wavelength of light during the light exposure period is a critical factor in embryo development. However, the effects of different light wavelengths on embryo development in pigs remain unexplored. This study aimed to identify the optimal light conditions to enhance oocyte maturation, parthenogenetic activation of mature oocytes, and pre-implantation development of parthenogenetic embryos in pigs. Conducted irradiation experiments during in vitro maturation (IVM), parthenogenesis (PG), and in vitro culture (IVC) using visible (390-750 nm), blue (445-500 nm), green (500-575 nm), yellow (575-585 nm), and red (620-750 nm) light. Variation in light wavelengths during IVM, PG, or IVC did not significantly influence oocyte maturation of cumulus-oocyte complexes (COCs) derived from median antral follicles (MAFs), developmental competence of in vitro-culture COCs after PG, and the production of blastocysts. However, continuous irradiation with green light throughout the entire process (IVM, PG, and IVC) significantly enhanced in vitro blastocyst production, and the resulting blastocysts showed significantly elevated HSP70 expression and a numerical increase in PCNA expression. We recommend conducting all in vitro procedures (IVM, PG, and IVC) for producing blastocysts from MAFs in porcine models under green light. This study will contribute to yielding higher success rates of porcine ART and reduce artificial stress to oocytes and embryos caused by in vitro manipulation under strong light exposure.