Effects of light wavelength exposure during in vitro blastocyst production on preimplantation development of mouse embryos

Context. Despite the absence of light within the body, the application of microscopy during stages of in vitro embryo production has led to the discovery of light irradiation effects on embryo preimplantation development. Aims, To determine the optimal light irradiation wavelengths at various embryo stages for improving the preimplantation development of mouse embryos and the quality (total cell number) of blastocysts. Method. All in vitro procedures of zygote or 2-cell embryo manipulation, embryo monitoring, and culture medium exchange were conducted under visible (390-750 nm), blue (445-500 nm), green (500-575 nm), yellow (575-585 nm), or red (620-750 nm) light irradiation wavelength. Key results. We found that blue, green, and yellow light irradiation during in vitro blastocyst production from zygotes significantly improved blastocyst production and quality, compared to visible and red light irradiation. However, 2-cell embryos exposed to yellow light during in vitro blastocyst production produced significantly more high-quality blastocysts than did 2-cell embryos exposed to visible, blue, green, or red light. After exposure to blue and green - but not yellow - light during in vitro zygote manipulation, yellow light irradiation during embryo monitoring and culture medium exchange triggered significant retardation of preimplantation development. Conclusion. These results demonstrate that yellow light irradiation during in vitro blastocyst production, regardless of embryo stage, improves preimplantation development of mouse embryos.