The effect of plasma-derived exosomes on cumulus expansion and fertility rate in mice in in vitro

Abstract

Infertility is one of the most common problems in the world. Women are responsible for half of all infertility cases. One of the main causes of female infertility is impaired oocyte maturation, ovulation and incomplete expansion of the cumulus-oocyte complex (COCs). Cumulus cell expansion plays a very important role in the ovulation process. Exosomes are nanosystems that are secreted by a wide range of cells. These small membrane vesicles with lipid bilayers can be obtained from a variety of body fluids and play an essential role in biological functions. Materials and Methods: The aim of this study was to investigate the effects of plasma-derived exosomes on cumulus expansion and in vitro maturation (IVM) of oocyte and fertility in mice in vitro. Exosomes were isolated from the plasma of female mice using ultracentrifugation. The morphology and size of the exosomes were analyzed by transmission electron microscopy (TEM) and dynamic light scattering (DLS). By Western blot analysis, CD63, CD81, CD9 and HSP70 proteins were examined as exosome markers. The expression of oocyte fertilization-related proteins such as MYH9, HSPA8 and annexin in exosomes was also examined by Western blotting. Expression of genes associated with cumulus cell expansion, including hyaluronan synthase 2 (Has2) and prostaglandin endoperoxide synthase 2 (Ptgs2), was examined in cumulus cells by Real-time PCR (Real-time polymerase chain reaction). Following IVF (In Vitro Fertilization), the percentage of different stages of embryonic development in 2-cell, 8-cell and morula stages was examined. Results: Plasma-derived exosomes labeled with DIL staining successfully entered cumulus cells during IVM. Plasma-derived exosomes significantly increased cumulus cell expansion and oocyte maturation. The percentage of oocytes that reached stage MII was significantly higher in the exosome treatment group compared to the other groups. Although treatment with epidermal growth factor (EGF) also significantly increased cumulus cell proliferation in the cumulus-oocyte complexs, this effect was lower than that seen in the treatment of plasma-derived exosomes. In addition, treatment of COCs with plasma-derived exosomes significantly increased the mRNA expression of Has2 and Ptgs2 genes. Our findings indicate a higher fertilization rate in mature oocytes in the body (MII oocytes) compared to in vitro mature oocytes (IVM oocytes). Also, under the same conditions of oocyte maturation, treatment with plasma-derived exosomes effectively affects and enhances the results of fertilization and embryonic development.