Antioxidant therapy counteracts the disturbing effects of diamide and maternal ageing on meiotic division and chromosomal segregation in mouse oocytes

Abstract

This study aims (i) to ascertain whether oxidative-stress-induced disturbances in chromosomal distribution in the metaphase-II spindle of mouse oocytes can be counteracted by supplementing culture medium with antioxidants; and (ii) to determine whether supplemental intake of antioxidants neutralizes the disturbing effects of maternal ageing on segregation of chromosomes during the first meiotic division and distribution of chromosomes in the metaphase-II spindle. (i): Germinal vesicle oocytes from unstimulated 10-12 week old mice were matured in vitro in the presence or absence of diamide and/or dithiothreitol. Metaphase-II oocytes were fixed and stained with 4',6-diamidino-2-phenylindole (DAPI) to detect abnormalities in chromosomal distribution. The percentage of oocytes arrested in metaphase I (12.9% vs 28.4%; P < or = 0.05) or with a telophase-I chromosome configuration (0.0% vs 8.2%; P < or = 0.0005) was decreased in diamide-DTT-treated oocytes when compared to diamide-treated oocytes. (ii): Mice were fed, from the first day of weaning until their death, a diet supplemented or not with an antioxidant mixture of vitamin C and vitamin E. Ovulated oocytes were fixed and stained with DAPI or C-banded for chromosome analysis. The percentage of abnormal (chromosome scattering and nulloploidy) or asynchronous (anaphase I or telophase I) oocytes was 2.7-fold higher in controls than in females fed an antioxidant diet (24.4% vs 8.9%, P < or = 0.05). Furthermore, the percentage of aneuploidy (2.2% vs 0.0%; P < or = 0.01) and diploidy (5.8% vs 1.7%; P < or = 0.05) was significantly higher in controls than in females fed an antioxidant diet. These findings support Tarin's oxidative stress hypothesis of aneuploidy and have clinical implications for preventing both laboratory-induced and maternal-age-associated aneuploidy in human beings.

Deficit of mitochondria-derived ATP during oxidative stress impairs mouse MII oocyte spindles

“…This hypothesis has been partially supported by several studies demonstrating the role of oxidants in regulating MT polymerization and cytoskeleton re-formation [9]. In addition, antioxidants can protect meiotic divisions from disorders that occur either in an oxidative stress situation or during maternal aging [10][11][12], further demonstrating that oxidative stress is involved in fertility senescence.…”

“…Only those spindles which that lay in a horizontal plane were evaluated for oocyte spindle length (pole-to-pole distance) and width. Dispersed chromosome distributions were defined as one or more individual chromosomes and were separated from the chromosomal plate by a distance greater than or equal to chromosomal length [10].…”

Effect of aging on follicular function may be relieved by exogenous gonadotropin treatment in a sheep model

“…The causes of morphological defects within oocytes from aged females are not known. Mutations in mitochondrial DNA and production of reactive oxygen species have been postulated to have a detrimental effect on oocytes from older females (Cummins 2000, Thouas et al 2005 with the potential to compromise chromosomal segregation in the oocyte (Tarin et al 1998, Schon et al 2000.…”

The Future of Human Embryo Culture Media – Or Have We Reached the Ceiling?

“…For example, increases in reactive oxygen species (ROS) in oocytes has been linked to increasing maternal age and it has been hypothesised that oocytes may be particularly susceptible to ROS damage while dormant in the ovary, potentially damaging lipids, proteins and DNA (Eichenlaub-Ritter et al 2010;Miquel and Fleming 1984;Tarin et al 1998a;Tarin 1996). This increase in ROS is proposed to be due to 'leaky mitochondria' as high energy electrons are transported along the electron transport chain and are leaked into the cytoplasm resulting the the formation of ROS such as superoxide anion (O 2-), hydrogen peroxide (H 2 O 2 ) and hydroxyl free radical (OH·) which can then damage the oocyte (Tarin et al 1998a;Tarin et al 1998b). …”

“…Vitamin supplementation has also been demonstrated to be of benefit when administered orally as in the aged mouse model, oral supplementation with vitamins C and E reduces age associated perturbations in segregation of chromosomes and spindle arrangement (Tarin et al 1998b).…”