Importance of Antioxidant Supplementation during In Vitro Maturation of Mammalian Oocytes.

The in vitro embryo production (IVEP) technique is widely used in the field of reproductive biology. In vitro maturation (IVM) is the first and most critical step of IVEP, during which, the oocyte is matured in an artificial maturation medium under strict laboratory conditions. Despite all of the progress in the field of IVEP, the quality of in vitro matured oocytes remains inferior to that of those matured in vivo. The accumulation of substantial amounts of reactive oxygen species (ROS) within oocytes during IVM has been regarded as one of the main factors altering oocyte quality. One of the most promising approaches to overcome ROS accumulation within oocytes is the supplementation of oocyte IVM medium with antioxidants. In this article, we discuss recent advancements depicting the adverse effects of ROS on mammalian oocytes. We also discuss the potential use of antioxidants and their effect on both oocyte quality and IVM rate.

Lycopene Reduces the In Vitro Aging Phenotypes of Mouse Oocytes by Improving Their Oxidative Status.

Postovulatory aging is a major problem that limits the success of many assisted reproductive technologies (ARTs). Oxidative stress is a leading cause of oocyte aging. This study investigated the effects of lycopene supplementation of in vitro maturation (IVM) medium during the aging of mouse oocytes on the oocytes' morphology and oxidative stress status. Mouse cumulus-oocyte complexes (COCs) were collected and cultured in the IVM medium either for 17 h, (freshly matured oocytes), or for 48 h, (in vitro-aged oocytes), with or without lycopene. The rate of fragmented and degenerated oocytes and the oocyte levels of hydrogen peroxide (H2O2), malondialdehyde (MDA), total antioxidant capacity (TAC), reduced glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD) were estimated and compared. Oocytes aged with 200 nM lycopene revealed significantly less fragmentation and degeneration, lower H2O2 and MDA levels, and higher TAC, GSH and SOD levels than those aged without lycopene. CAT levels were unchanged by lycopene treatment. Taken together, our data showed beneficial effects of lycopene during in vitro aging of mouse oocytes by reducing the oxidative stress damages that lead to their apoptosis. The present study introduces lycopene as a natural supplement to reduce the postovulatory aging-dependent abnormalities of mammalian oocytes.

Effect of E-64 Supplementation during In Vitro Maturation on the Developmental Competence of Bovine OPU-Derived Oocytes.

Recovery of bovine oocytes using the ovum pick-up (OPU) technique offers the advantage of rapid genetic improvement through propagation of desired genes from animals with high genetic qualities. However, the developmental competence of OPU-derived immature oocytes remains relatively poor. We previously found that cathepsin B gene expression and activity are increased in poor quality oocytes and embryos compared to good quality ones. In this study, we investigated the effect of E-64 (cathepsin B inhibitor) supplementation during in vitro maturation (IVM) on the developmental competence of OPU-derived immature oocytes and the quality of the produced blastocysts. Our results showed that supplementation of IVM medium with E-64 significantly improved the developmental competence of OPU-derived immature oocytes as evidenced by the significant increase of the blastocyst rate. Importantly, the presence of E-64 during IVM also significantly improved blastocyst quality by increasing the total cell number and decreasing the percentage of TUNEL positive cells. These results indicate that E-64 supplementation during IVM is a promising tool to improve the efficiency of OPU-IVF program by improving the developmental competence of OPU-derived immature oocytes.

The effect of cholesterol loaded cyclodextrins on post-thawing quality of buffalo semen in relation to sperm DNA damage and ultrastructure.

The cryopreservation of germ cells is a major tool for the propagation of animals with desired genetic traits. Although cryopreservation of spermatozoa in some animals is effective, its effectiveness is variable. For example, cryopreservation efficiency of buffalo bull spermatozoa remains very poor. In this study, we evaluated sperm DNA damage and ultrastructure in buffalo bull spermatozoa vitrified in the presence or absence of cholesterol-loaded cyclodextrins (CLC). Our results showed that cryopreserved buffalo spermatozoa had elevated levels of deteriorated plasma and mitochondrial membranes, which are the likely causes of DNA damage after vitrification. Accordingly, the levels of the activity of Alanine Aminotransferase (ALT), Alkaline phosphatase (ALP) and Aspartate Aminotransferase (AST) were also elevated following exposure of buffalo bull spermatozoa to a cycle of freezing-thawing. Importantly, supplementation of Tris-Egg Yolk-Glucose (TEYG) extender with (CLC) improved the quality of buffalo spermatozoa following cryopreservation. This protective effect of CLC is likely due to decreasing mitochondrial and plasma membrane deterioration with subsequent inhibition of DNA damage. These results suggest that cholesterol loss is the likely reason for poor semen quality in buffaloes following cryopreservation, and provide evidence that manipulating lipid content during cryopreservation is a promising strategy to improve the quality of buffalo semen.