In a healthy body, ROS (reactive oxygen species) and antioxidants remain in balance When the balance is disrupted towards an overabundance of ROS, oxidative stress (OS) occurs OS influences the entire reproductive lifespan of a woman and even thereafter (ie menopause) OS results from an imbalance between prooxidants (free radical species) and the body's scavenging ability (antioxidants) ROS are a double-edged sword – they serve as key signal molecules in physiological processes but also have a role in pathological processes involving the female reproductive tract ROS affect multiple physiological processes from oocyte maturation to fertilization, embryo development and pregnancy It has been suggested that OS modulates the age-related decline in fertility It plays a role during pregnancy and normal parturition and in initiation of preterm labor Most ovarian cancers appear in the surface epithelium, and repetitive ovulation has been thought to be a causative factor Ovulation-induced oxidative base damage and damage to DNA of the ovarian epithelium can be prevented by antioxidants There is growing literature on the effects of OS in female reproduction with involvement in the pathophsiology of preeclampsia, hydatidiform mole, free radical-induced birth defects and other situations such as abortions Numerous studies have shown that OS plays a role in the pathoysiology of infertility and assisted fertility There is some evidence of its role in endometriosis, tubal and peritoneal factor infertility and unexplained infertility This article reviews the role OS plays in normal cycling ovaries, follicular development and cyclical endometrial changes It also discusses OS-related female infertility and how it influences the outcomes of assisted reproductive techniques The review comprehensively explores the literature for evidence of the role of oxidative stress in conditions such as abortions, preeclampsia, hydatidiform mole, fetal embryopathies, preterm labour and preeclampsia and gestational diabetes The review also addresses the growing literature on the role of nitric oxide species in female reproduction The involvement of nitric oxide species in regulation of endometrial and ovarian function, etiopathogenesis of endometriosis, and maintenance of uterine quiescence, initiation of labour and ripening of cervix at parturition is discussed Complex interplay between cytokines and oxidative stress in the etiology of female reproductive disorders is discussed Oxidant status of the cell modulates angiogenesis, which is critical for follicular growth, corpus luteum formation endometrial differentiation and embryonic growth is also highlighted in the review Strategies to overcome oxidative stress and enhance fertility, both natural and assisted are delineated Early interventions being investigated for prevention of preeclampsia are enumerated Trials investigating combination intervention strategy of vitamin E and vitamin C supplementation in preventing preeclampsia are highlighted Antioxidants are powerful and there are few trials investigating antioxidant supplementation in female reproduction However, before clinicians recommend antioxidants, randomized controlled trials with sufficient power are necessary to prove the efficacy of antioxidant supplementation in disorders of female reproduction Serial measurement of oxidative stress biomarkers in longitudinal studies may help delineate the etiology of some of the diosorders in female reproduction such as preeclampsia

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Role of oxidative stress in female reproduction

Oxidative stress occurs when the production of potentially destructive reactive oxygen species (ROS) exceeds the bodies own natural antioxidant defenses, resulting in cellular damage. Oxidative stress is a common pathology seen in approximately half of all infertile men. ROS, defined as including oxygen ions, free radicals and peroxides are generated by sperm and seminal leukocytes within semen and produce infertility by two key mechanisms. First, they damage the sperm membrane, decreasing sperm motility and its ability to fuse with the oocyte. Second, ROS can alter the sperm DNA, resulting in the passage of defective paternal DNA on to the conceptus. This review will provide an overview of oxidative biochemistry related to sperm health and will identify which men are most at risk of oxidative infertility. Finally, the review will outline methods available for diagnosing oxidative stress and the various treatments available.

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Oxidative stress and male infertility—a clinical perspective

Oxidative stress is involved in the aetiology of defective embryo development. Reactive oxygen species (ROS) may originate from embryo metabolism and/or embryo surroundings. Embryo metabolism generates ROS via several enzymatic mechanisms. The relative contribution of each source seems different depending on the species, the stage of development, and the culture conditions. Several exogenous factors and culture conditions can enhance the production of ROS by embryos. ROS can alter most types of cellular molecules, and also induce development block and retardation. Multiple mechanisms of embryo protection against ROS exist, and these have complementary actions. External protection, present in follicular and tubal fluids, mainly comprises non-enzymatic antioxidants such as hypotaurine, taurine and ascorbic acid. Internal protection mainly comprises antioxidant enzymes: superoxide dismutase, glutathione peroxidase and gamma-glutamylcysteine synthetase. Transcripts encoding for these enzymes are present in the oocyte, embryo and oviduct. It may be important that these transcripts are stored during oocyte maturation in order to allow the embryo to acquire the aptitude to develop. It is now common to add antioxidant compounds to culture media. Nevertheless, maintaining the pro-oxidant-antioxidant equilibrium in embryos through such supplementation is a complex problem. Further studies are necessary to limit oxidative stress during embryo culture.

Oxidative stress and protection against reactive oxygen species in the pre-implantation embryo and its surroundings

Oxidative stress (OS), a state characterized by an imbalance between pro-oxidant molecules including reactive oxygen and nitrogen species, and antioxidant defenses, has been identified to play a key role in the pathogenesis of subfertility in both males and females. The adverse effects of OS on sperm quality and functions have been well documented. In females, on the other hand, the impact of OS on oocytes and reproductive functions remains unclear. This imbalance between pro-oxidants and antioxidants can lead to a number of reproductive diseases such as endometriosis, polycystic ovary syndrome (PCOS), and unexplained infertility. Pregnancy complications such as spontaneous abortion, recurrent pregnancy loss, and preeclampsia, can also develop in response to OS. Studies have shown that extremes of body weight and lifestyle factors such as cigarette smoking, alcohol use, and recreational drug use can promote excess free radical production, which could affect fertility. Exposures to environmental pollutants are of increasing concern, as they too have been found to trigger oxidative states, possibly contributing to female infertility. This article will review the currently available literature on the roles of reactive species and OS in both normal and abnormal reproductive physiological processes. Antioxidant supplementation may be effective in controlling the production of ROS and continues to be explored as a potential strategy to overcome reproductive disorders associated with infertility. However, investigations conducted to date have been through animal or in vitro studies, which have produced largely conflicting results. The impact of OS on assisted reproductive techniques (ART) will be addressed, in addition to the possible benefits of antioxidant supplementation of ART culture media to increase the likelihood for ART success. Future randomized controlled clinical trials on humans are necessary to elucidate the precise mechanisms through which OS affects female reproductive abilities, and will facilitate further explorations of the possible benefits of antioxidants to treat infertility.

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The effects of oxidative stress on female reproduction: a review

A purified preparation of primate embryonic stem cells is disclosed. This preparation is characterized by the following cell surface markers: SSEA-1 (−); SSEA-4 (+); TRA-1-60 (+); TRA-1-81 (+); and alkaline phosphatase (+). In a particularly advantageous embodiment, the cells of the preparation are human embryonic stem cells, have normal karyotypes, and continue to proliferate in an undifferentiated state after continuous culture for eleven months. The embryonic stem cell lines also retain the ability, throughout the culture, to form trophoblast and to differentiate into all tissues derived from all three embryonic germ layers (endoderm, mesoderm and ectoderm). A method for isolating a primate embryonic stem cell line is also disclosed.

Primate embryonic stem cells

The aim of the present prospective study was to determine whether subtle sperm morphological characteristics affect the outcome of intracytoplasmic sperm injection (ICSI), and if so, to identify those that are relevant. For this purpose, we developed a new method, the motile sperm organelle morphology examination (MSOME). The examination is performed in real time using an inverted light microscope equipped with high-power Nomarski optics enhanced by digital imaging to achieve a magnification up to 6300x. MSOME was applied to the leftover sperm fraction selected for microinjection in 100 random couples referred for ICSI treatment at 3 major in vitro fertilization centers. We found that the morphological normalcy of the entire sperm cell, according to MSOME criteria, was positively associated with ICSI fertilization rate (area under the receiver operating characteristics [ROC] curve, 88%) but not with pregnancy outcome. The morphological normalcy of the sperm nucleus, defined by MSOME, was significantly and positively associated with both fertilization rate and pregnancy outcome (areas under the ROC curve, 72% and 74%, respectively). These findings indicate that ICSI-associated pregnancy rate may be affected by subtle morphological malformations of the sperm nucleus, which may remain undetected by the embryologist during the routine selection procedure.

Real-time fine morphology of motile human sperm cells is associated with IVF-ICSI outcome.

The aim of the present prospective study was to de- termine whether subtle sperm morphological characteristics affect the outcome of intracytoplasmic sperm injection (ICSI), and if so, to identify those that are relevant. For this purpose, we developed a new method, the motile sperm organelle morphology examination (MSOME). The examination is performed in real time using an in- verted light microscope equipped with high-power Nomarski optics enhanced by digital imaging to achieve a magnification up to 6300. MSOME was applied to the leftover sperm fraction selected for mi- croinjection in 100 random couples referred for ICSI treatment at 3 major in vitro fertilization centers. We found that the morphological normalcy of the entire sperm cell, according to MSOME criteria, was positively associated with ICSI fertilization rate (area under the re- ceiver operating characteristics (ROC) curve, 88%) but not with preg- nancy outcome. The morphological normalcy of the sperm nucleus, defined by MSOME, was significantly and positively associated with both fertilization rate and pregnancy outcome (areas under the ROC curve, 72% and 74%, respectively). These findings indicate that ICSI-associated pregnancy rate may be affected by subtle morpho- logical malformations of the sperm nucleus, which may remain un- detected by the embryologist during the routine selection procedure.

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Breakthroughs in Andrology Real-Time Fine Morphology of Motile Human Sperm Cells is Associated With IVF-ICSI Outcome

Reactive oxygen species (ROS) have a negative impact on sperm DNA, leading to the formation of oxidative products such as 8-oxo-7,8-dihydroxyguanosine. This compound causes fragmentation and, thus, has a mutagenic effect. Patient treatment with oral antioxidant vitamins is, therefore, standard practice for male infertility, in an attempt to decrease formation of ROS and improve fertility. In this study, the DNA fragmentation index and the degree of sperm decondensation were measured using the sperm chromatin structure assay before and after 90 days treatment with antioxidant vitamins associated with zinc and selenium. Antioxidant treatment led to a decrease in sperm DNA fragmentation (–19.1%, P < 0.0004), suggesting that at least part of the decay was linked to ROS. However, it also led to an unexpected negative effect: an increase in sperm decondensation with the same order of magnitude (+22.8%, P < 0.0009). The opening of interchain disulphide bridges in protamines may explain this aspect, as antioxidant vitamins, especially vitamin C, are able to open the cystin net, thus interfering with paternal gene activity during preimplantation development. This observation might explain the discrepancy observed concerning the role of these antioxidant treatments in improving male fertility.

https://www.rbmojournal.com/article/S1472-6483(10)60887-5/pdf

Antioxidants to reduce sperm DNA fragmentation: an unexpected adverse effect

In human in vitro fertilization (I.V.F.), it was first assumed that all the embryos obtained had the same developmental potential whatever the quality of sperm. However, this has not been confirmed. We have used the coculture technique and determined the blastocyst formation rate in three groups of patients: group 1: patients with normal sperm count (> 20 x 10(6)/ml), motility (> 30%), and morphology (> 50%); group 2: patients treated by I.V.F. with frozen donor sperm; group 3: patients with severely impaired sperm quality (< 3 x 10(6) forward motile and morphologically normal spermatozoa per ml). In group 1, we found a strong correlation between cleavage rate and blastocyst formation rate (P < 0.0001) with a blastocyst formation rate comprised between 40% and 50%. This was not true for the two other groups for which the overall number of blastocysts obtained and the number of patients having at least one blastocyst were severely reduced (P < 0.0001). These data are discussed in terms of DNA quality, timing of formation of the pronuclei, and delays in cell cycles at the time of genomic activation. These observations lead to a new approach to the study of fertilizing ability of poor quality sperm. It may help in the decision as to whether couples treated for male infertility should be excluded from I.V.F. protocols.

Yves Menezo

Papers

Oxidative stress and protection against reactive oxygen species in the pre-implantation embryo and its surroundings

Real-time fine morphology of motile human sperm cells is associated with IVF-ICSI outcome.

Breakthroughs in Andrology Real-Time Fine Morphology of Motile Human Sperm Cells is Associated With IVF-ICSI Outcome

Antioxidants to reduce sperm DNA fragmentation: an unexpected adverse effect

Evidence for a strong paternal effect on human preimplantation embryo development and blastocyst formation.