Glutathione Peroxidase 3 in Mouse Oocytes, Preimplantation Embryos and Female Genital Organs During The Preimplantation Period Of Pregnancy

Abstract Objectives This study describes the presence of glutathione peroxidase 3 (GPx3) in mice oocytes, preimplantation embryos (O/PEs), and female genital organs during the preimplantation period of pregnancy. Background Glutathione peroxidase 3, the antioxidant enzyme, is important in protecting cells against the oxidative stress. Methods O/PEs were isolated from genital organs of superovulated females for the immunofluorescence analysis and these organs were used for the immunohistochemistry to detect GPx3. Results GPx3 was present in all O/PEs, where it formed clusters diffusely in the cytoplasm, or under the cytoplasmic membrane. Moreover, GPx3 was likely indicated in nucleoli. GPx3 was found in the cytoplasm of granulosa-lutein cells as well as in follicular cells. The oocyte cytoplasm inside the ovary was negative. Oviductal epithelial cells before and after fertilization had different positivity patterns. Uterine luminal epithelial cells were negative before fertilization. After fertilization, a few positive luminal epithelial cells and a few cells of uterine glands had positive cytoplasm. Conclusion The differences of the GPx3 signal intensity in nucleoli of the zygote and the 2-cell embryo, and the different localization of GPx3 in the cytoplasm of 2-cell and 4-cell embryos may be the signs of the maternal-zygotic genome transition. Moreover, GPx3 may be significant during the preimplantation period of pregnancy in O/PEs and female genital organs, where it could protect cells from oxidative stress during the hormone and protein synthesis, and during the cell metabolism. The presence of cytoplasmic granules in epithelial cells of fallopian tube may indicate their secretion into the lumen of the organ to protect gametes and preimplantation embryos passing through. To our knowledge, this is the first study investigating GPx3 occurrence in mammalian preimplantation embryos.