GPx8 Expression in Rat Oocytes, Embryos, and Female Genital Organs During Preimplantation Period of Pregnancy.

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

doi:10.3390/ijms21176313

Abstract

This study aimed to detect the presence of glutathione peroxidase 8 (GPx8) in rat during preimplantation period of pregnancy. Females were killed on first (D1), third (D3), and fifth (D5) day of pregnancy. The presence of GPx8 in embryos was detected under the confocal microscope, the presence of GPx8 in genital organs was confirmed immunohistochemically, and the amount of GPx8 was determined using densitometry. We found that GPx8 is dispersed in the cytoplasm of oocytes, while after fertilization, it is concentrated in granules. From 4-cell stage till blastocyst, GPx8 reaction was found in the perinuclear region. In the ovary, GPx8 was seen in granulosa-lutein cells, in plasma of blood vessels, and inside Graafian follicles. In oviduct, GPx8 was detected in the plasma and in the extracellular matrix (ECM). Moreover, epithelial cells of isthmus were positive. In uterus, GPx8 was observed in the uterine glands, in the plasma, and in ECM. On D5, the enzyme disappeared from the uterine glands and appeared in fibroblasts. Densitometry revealed that the highest amount of GPx8 was on D1 and subsequently declined. To our knowledge, this is the first paper describing GPx8 presence in the oocytes, preimplantation embryos, and female genital organs in mammals. Our results improve the understanding of antioxidant enzymes presence during pregnancy in defense against oxidative stress, which is considered to be one of the main causes of infertility.

Highlights

Infertility, which is defined as the inability to achieve pregnancy after one year of regular unprotected sexual intercourse [1], became a significant worldwide public health problem [2]
We found that glutathione peroxidase 8 (GPx8) is present in both oocytes and preimplantation embryos of rats
The fact that the GPx8 was found in oocytes/embryos and concurrently in all genital organs of the mother during the entire preimplantation phase of pregnancy suggests that glutathione peroxidases are important for the early development of a new individual

Summary

Introduction

Infertility, which is defined as the inability to achieve pregnancy after one year of regular unprotected sexual intercourse [1], became a significant worldwide public health problem [2]. The global average prevalence of infertility is estimated as 9% of reproductive-aged couples [3]. Current evidence links oxidative stress (OS) to male infertility, reduced sperm motility, sperm DNA damage, and increased risk of recurrent abortions and genetic diseases due to the large amounts of unsaturated fatty acids found in sperm cell membranes, which are highly susceptible to the harmful effects of reactive oxygen species (ROS) [4]. Many studies have linked the prevalence of female infertility with an increase in oxidative stress levels in the various critical micro- or macro-environments in the body. Studies have shown that OS causes the abnormal expression of several proteins, which could lead to the pathophysiology of female infertility [5]. ROS are necessary for the normal course of the reproductive process, such as sperm capacitation, acrosome reaction, or sperm-oocyte fusion, OS is detrimental to fertility, pregnancy, and genetic status of the newborns [6]

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