Characterization of Glutathione Peroxidase 4 in Rat Oocytes, Preimplantation Embryos, and Selected Maternal Tissues during Early Development and Implantation.

Andrea Kreheľová,Peter Solár,Andriana Pavliuk-Karachevtseva,Silvia Rybárová,Jozef Mihalik,Ingrid Hodorová,Alena Pastornická,Veronika Kovaříková,Iveta Domoráková

doi:10.3390/ijms22105174

Abstract

This study aimed to describe glutathione peroxidase 4 (GPx4) in rat oocytes, preimplantation embryos, and female genital organs. After copulation, Sprague Dawley female rats were euthanized with anesthetic on the first (D1), third (D3), and fifth days of pregnancy (D5). Ovaries, oviducts, and uterine horns were removed, and oocytes and preimplantation embryos were obtained. Immunohistochemical, immunofluorescent, and Western blot methods were employed. Using immunofluorescence, we detected GPx4 in both the oocytes and preimplantation embryos. Whereas in the oocytes, GPx4 was homogeneously diffused, in the blastomeres, granules were formed, and in the blastocysts, even clusters were present mainly around the cell nuclei. Employing immunohistochemistry, we detected GPx4 inside the ovary in the corpus luteum, stroma, follicles, and blood vessels. In the oviduct, the enzyme was present in the epithelium, stroma, blood vessels, and smooth muscles. In the uterus, GPx4 was found in the endometrium, myometrium, blood vessels, and stroma. Moreover, we observed GPx4 positive granules in the uterine gland epithelium on D1 and D3 and cytoplasm of fibroblasts forming in the decidua on D5. Western blot showed the highest GPx4 levels in the uterus and the lowest levels in the ovary. Our results show that the GPx4 is necessary as early as in the preimplantation development of a new individual because we detected it in an unfertilized oocyte in a blastocyst and not only after implantation, as was previously thought.

Highlights

We found that glutathione peroxidase 4 (GPx4) was present throughout the entire preimplantation period of pregnancy from the unfertilized oocytes to the blastocysts
Fifteen female rats were used for Western blot (WB), and the oocytes and preimplantation embryos were isolated from the oviduct and uterus
The enzyme was present in all developmental stages of a new individual, from the unfertilized oocytes to the blastocysts, which testifies its high importance in the reproductive process

Summary

Introduction

10% of the human population is infertile [1]. Couple infertility is defined as the inability to conceive even after one year of unprotected sexual intercourse [2]. Infertility is caused by various etiologies, such as hormonal disorders or hypoxia, with subsequent oxidative stress (OS) [3]. In women, this condition is caused mainly by polycystic ovary syndrome [4], chemotherapy, and radiotherapy due to cancer treatment [5]. Several treatment possibilities exist for infertility, such as intrauterine insemination (IUI), in vitro fertilization (IVF), and intracytoplasmic sperm injection (ICSI) [7]

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Conclusion