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Genus PLC/ABS, Mogi Mirim, SP, Brazil
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Department of Livestock Development, Bureau of Biotechnology in Livestock Production, Pathum Thani, Thailand
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The WNT inhibitory protein DKK1 has been shown to regulate the development of the preimplantation embryo to the blastocyst stage. In cattle, DKK1 increases the number of trophectoderm cells that are the precursor of the placenta. DKK1 can affect cells by blocking WNT signaling through its receptors KREMEN1 and KREMEN2. Here it was shown that the mRNA for KREMEN1 and KREMEN2 decline as the embryo advances in development. Nonetheless, immunoreactive KREMEN1 was identified in blastocysts using western blotting. DKK1 also decreased the amount of immunoreactive β-catenin in blastocysts, as would be expected if DKK1 was signaling through a KREMEN-mediated pathway. Thus, it is likely that KREMEN1 functions as a receptor for DKK1 in the preimplantation bovine embryo.
Lay summary
DKK1 is a molecule produced by the lining of the womb (uterus) that regulates the development of the early embryo. Here it was shown that a substance that responds to DKK1 called KREMEN1 is found in the embryos of cattle. In other cells, joining of DKK1 to KREMEN1 results in reduction in amounts of a protein called β-catenin. For the present study, it was shown that DKK1 treatment also reduced β-catenin in the cattle, which suggests that DKK1 can regulate the cattle embryo by attaching to KREMEN1.
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Bisphenol A (BPA) is an endocrine-disrupting compound, used as the key monomer of polycarbonate plastics and epoxy resins. BPA has been detected in both humans and farm animals and has been correlated with decreased sperm counts and motility. BPS and BPF are structural analogs of BPA and are increasingly being used in manufacturing as BPA substitutes. In this study, we aim to assess the direct outcomes of BPA, bisphenol S (BPS), and bisphenol F (BPF) exposure on bovine sperm parameters in vitro to elucidate how they affect sperm quality and fertilization potential, and to assess whether BPS and/or BPF are less harmful than BPA. Sperm from three or more bulls was obtained from either fresh samples or cryopreserved straws and exposed to 0.05 mg/mL of BPA, BPS, and BPF in vitro. After 4 h incubation, motility, capacitation, apoptosis/necrosis, and mitochondrial membrane potential levels were measured by computer-assisted sperm analysis or computational flow cytometry. Results showed that BPA exposure significantly reduced both fresh and cryopreserved sperm motility, capacitation, viability and mitochondrial membrane potential levels. Furthermore, BPF significantly decreased motility, capacitation and mitochondrial membrane potential in cryopreserved sperm only. BPS did not have any significant effects on any of the parameters measured. Our results suggest that BPA is the most harmful to sperm, while BPF is toxic under certain conditions, and BPS seems to be the least detrimental. Overall, this study provides an understanding of how the ubiquitous environmental chemicals, bisphenols, may impact male fertility even after ejaculation.
Lay summary
Bisphenol A (BPA) is a widespread man-made compound found in plastic products and the environment, and has been detected in human and animal biological fluids. BPA has been previously investigated for its negative effects on health, including its detrimental impacts on reproductive cells. Concerns over the use of BPA has led to its ban in some countries and has introduced the use of ‘BPA-free’ products, which typically contain substitutes such as bisphenols S and F (BPS and BPF). This current study investigates the effects of bull sperm exposure to BPA, BPS, and BPF to evaluate their impacts on sperm quality. After exposure, both BPA and BPF lowered sperm mobility, organelle function (by reducing mitochondrial activity), and overall survival; while BPS had no effects. Overall, this study shows that BPA and its common replacement, BPF, can both act on sperm directly, reducing their overall quality and function.
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Paediatric Oncology, Leeds Children’s Hospital, Leeds, UK
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In the context of a cancer diagnosis, fertility preservation interventions are used to mitigate the potential impact of gonadotoxic cancer treatment upon fertility. They provide patients with cancer the option to freeze their reproductive material to have their own biological child following treatment. The evidence suggests some clinicians are less likely to have fertility preservation discussions with patients who have an aggressive or metastatic cancer which has a poor prognosis. Although this is contrary to current policy recommendations, there is a lack of guidance relating to offering fertility preservation in the context of a poor prognosis to support clinicians. Controversy surrounds posthumous reproduction, and whether the wishes of the cancer patient, when living and deceased should take precedence over others’ well-being. We consider the question of whether cancer patients with a poor prognosis should be offered fertility preservation from an ethics perspective. We structure the paper around key arguments to which multiple ethical principles might pertain, first establishing a central argument in favour of offering fertility preservation based on respect for autonomy, before exploring counterarguments. We conclude by proposing that a defeasible assumption should be adopted in favour of offering fertility preservation to all cancer patients who might benefit from it. It is important to recognise that patients could benefit from fertility preservation in many ways, and these are not limited to having a parenting experience. The burden of proof rests on the clinician in collaboration with their multidisciplinary team, to show that there are good grounds for withholding the offer.
Lay summary
When a person is diagnosed with cancer, they may wish to consider undergoing fertility preservation procedures. These procedures give patients a chance to have their own biological child after completing cancer treatment. However, research suggests that cancer patients who have a poor prognosis are less likely to be offered fertility preservation treatment. In this paper, we consider the ethical implications of offering (or not) fertility preservation to this patient group, including using their sperm or eggs to reproduce after their death. We conclude that fertility preservation treatments should be offered to all cancer patients who might benefit from it, and we outline the many ways that benefit from this treatment can be gained. The decision to withhold the offer of fertility preservation treatment should be made between the patient’s clinician and their wider care team. They must be able to provide good reasons to explain why it was withheld.
APC Microbiome Ireland, University College Cork, Cork, Ireland
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Many parts of the animal and human body host groups of bacteria, viruses, and fungi that together are known as the microbiome. Microbiomes do not cause disease but are important for the healthy working of many systems in the body, including for reproduction and fertility. While the microbiome that lives in a reproductive tract play the most direct role, microbiomes from other areas of the body may also affect reproductive health. However, not much is known about how these groups of microorganisms regulate fertility as well as the health of parents and offspring and help animals to cope with environmental changes. Furthermore, compared to the large amount of research in laboratory species and humans, there is less information about domestic or wild animal species. This special series of Reproduction and Fertility on microbiomes is aimed at filling this gap with articles from experts highlighting important evidence in reproductive microbiomes, current research gaps, and new directions.
Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa
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Mammal Research Institute, Faculty of Natural and Agricultural Sciences, University of Pretoria, Hatfield, South Africa
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Recent loss of rhinoceros subspecies has renewed interest in using more advanced assisted reproductive technologies (ART) in rhinoceroses and elephants. Currently, only semen collection, semen preservation and artificial insemination (AI) have been used repeatedly with success in these species. Although ovum pick-up (OPU) and intra-cytoplasmic sperm injection (ICSI) have been reported recently in rhinoceroses, the techniques are not yet optimised. In contrast, multiple ART applications are routinely used in the horse. Since elephants and rhinoceroses share some reproductive features with equids, we postulate that procedures such as OPU, ICSI, in vitro fertilisation (IVF) and embryo transfer (ET), which are well established in the horse, may represent a basis to develop protocols for endangered pachyderms. In this review, we summarise current knowledge on reproductive physiology relevant to ART. We discuss the current state of ART in all three families and the requirements for the successful implementation of OPU, ICSI, IVF and ET in these species.
Lay summary
Wild rhinoceros and elephant populations are facing ongoing threats; therefore, additional measures are required to protect these species for future generations. Assisted reproductive technologies (ART) include the collection of semen to directly inseminate females or to fertilise oocytes (eggs) in a laboratory to produce embryos, which can be transferred into a recipient female at a later date. While these techniques are routinely used in humans and domestic animals such as the horse, more research is needed to incorporate such technologies into the breeding of elephants and rhinoceroses. As the horse is the closest related domestic species to the rhinoceros, it may serve as the best possible role model. We discuss the current state of ART in the horse, elephant and rhinoceros and the possibilities for future use of these techniques in breeding such endangered animals.
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McMaster University Health Sciences Center, Hamilton, Ontario, Canada
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Endometriosis is a chronic disease associated with debilitating pain that affects many people assigned female at birth, from menarche through menopause, not just causing pain and infertility but also negatively impacting quality of life, participation in daily activities, productivity, and income. It is associated with increased incidence of obstetric and neonatal complications, anxiety, other chronic diseases, and substantial healthcare costs. Despite the profound negative impact of endometriosis on quality of life, current treatment options remain suboptimal and many patients express dissatisfaction with current care. The prevailing acute-care, single-provider model in which the provider works in relative isolation and thus with limited diagnostic and therapeutic strategies readily available proves inadequate for treating endometriosis. Patients would benefit from earlier diagnosis and referral to a center capable of providing a comprehensive and multimodal management plan that utilizes a chronic care model. Often this can only be achieved through multidisciplinary teams of providers with expertise in endometriosis. The authors acknowledge that many low- and middle-income countries do not have the resources to support such centers but could still benefit from any breakthroughs in treatment they bring about. Researchers need to agree on standardized core outcome measures, relevant to patients with endometriosis and the healthcare system as a whole. Only through increased societal and healthcare provider education and recognition of endometriosis as a chronic disease can we achieve better treatment outcomes.
Lay summary
Endometriosis is a disease that affects about one out of every women. It occurs when tissue like that which is normally located inside the uterus is present outside the uterus. The body’s reaction to this tissue causes inflammation and pain, usually so severe that it disrupts daily activities. Our current medical system does not serve these patients well. Patients with endometriosis often must see many different doctors over many years before learning of their disease and getting treatment. We need to increase awareness of endometriosis and think of it as a chronic disease like diabetes or heart disease. We can improve care by creating centers where experienced teams work together to treat patients and study treatment impacts on quality of life. It is time to adopt a new model for caring for patients with endometriosis.
Department of Medical Biotechnology, National Biotechnology Development Agency, Abuja, Nigeria
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Sickle cell disease (SCD) poses an increased risk of infertility, pregnancy complications and maternal and perinatal mortality among women of reproductive age. This risk is particularly higher for women in sub-Saharan Africa, where the disease burden is highest and access to comprehensive health care is limited, as well as in other countries with a high SCD prevalence due to migration. Disease-modifying treatments for SCD could directly and indirectly harm the ovaries, potentially compromising the quality and quantity of existing oocytes. Therefore, it is essential to explore alternative interventions, such as nutritional modifications that are less harmful and cost-effective in order to improve reproductive outcomes and enhance the overall well-being of both mother and child in this population. Maintaining optimal levels of B12 may possibly provide benefits to the ovaries and pregnancy by decreasing homocysteine levels, increasing nitric oxide (NO) bioavailability and promoting antioxidant and anti-inflammatory activities. Individuals living with SCD are more susceptible to vitamin B12 (B12) deficiency. However, there is a lack of clinical data investigating the relationship between systemic levels of B12, its supplementation, and reproductive outcome measures in SCD women. Therefore, this review aims to examine the current evidence regarding the impact of SCD on female reproductive health and the role of B12 in the reproductive biology of women living with SCD.
Lay summary
Poor reproductive health is a concern for patients with sickle cell disease (SCD). SCD can lead to damage to the ovaries. Most of the therapies for sickle cell disease are toxic to the ovaries, expensive and unavailable to affected women, particularly those living in resource-poor areas such as sub-Saharan Africa. There is a need to seek less harmful and affordable interventions such as nutrition to improve reproductive outcomes for women with SCD who are of child-bearing age. Good levels of vitamin B12 have been found to maintain ovarian health and pregnancy. Patients with SCD have been reported to have a high risk of vitamin B12 deficiency, but the impact of B12 on reproduction in this group of women is yet to be evaluated. The review explores current evidence of the impact of both SCD and B12 on female reproduction.
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Maternal and Fetal Health Research Centre, Saint Mary’s Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Sciences Centre, University of Manchester, Manchester, UK
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Maternal and Fetal Health Research Centre, Saint Mary’s Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Sciences Centre, University of Manchester, Manchester, UK
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Maternal and Fetal Health Research Centre, Division of Developmental Biology and Medicine, School of Medical Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
Maternal and Fetal Health Research Centre, Saint Mary’s Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Sciences Centre, University of Manchester, Manchester, UK
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Maternal and Fetal Health Research Centre, Saint Mary’s Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Sciences Centre, University of Manchester, Manchester, UK
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Genome-wide analysis of gene expression has been widely applied to study the endometrium, although to our knowledge no systematic reviews have been performed. Here, we identified 74 studies that described transcriptomes from whole (unprocessed) endometrium samples and found that these fitted into three broad investigative categories: endometrium across the menstrual cycle, endometrium in pathology and endometrium during hormone treatment. Notably, key participant information such as menstrual cycle length and body mass index was often not reported. Fertility status was frequently not defined and fertility-related pathologies, such as recurrent implantation failure (RIF) and recurrent pregnancy loss, were variably defined, while hormone treatments differed between almost every study. A range of 1307–3637 reported differentially expressed genes (DEGs) were compared in four to seven studies in five sub-categories: (i) secretory vs proliferative stage endometrium, (ii) mid-secretory vs early secretory stage endometrium, (iii) mid-secretory endometrium from ovarian stimulation-treated participants vs controls, (iv) mid-secretory endometrium from RIF patients vs controls, and (v) mid-secretory eutopic endometrium from endometriosis patients vs controls. Only the first two sub-categories yielded consistently reported DEG between ≥3 studies, albeit in small numbers (<40), and these were enriched in developmental process and immune response annotations. This systematic review, though not PROSPERO registered, reveals that limited demographic detail, variable fertility definitions and differing hormone treatments in endometrial transcriptomic studies hinder their comparison, and that the large majority of reported DEG do not advance the identification of underlying biological mechanisms. Future studies should apply network biology approaches and experimental validation to establish causal gene expression signatures.
Lay summary
The endometrium lines the inner wall of the uterus and is the site where the fertilised egg implants to establish pregnancy. Disorders of the endometrium cause infertility and chronic pain. Techniques to measure genetic activity, termed transcriptomics, have been applied to better understand the endometrium in health and disease. We collated all studies, totalling 74, that describe transcriptomics of endometrial samples from non-pregnant women and compared study designs and genetic activity measurements. The studies generally looked at small numbers of samples, with most focussing on fertility rather than endometrial disorders. Study designs were variable, comparing women under different definitions of fertility and disease, and under different treatments. Additionally, key participant factors such as BMI were mostly not reported. These and other limitations produced genetic activity measurements that were inconsistent, especially in cases of infertility and endometrial disorders. Addressing these limitations could improve how transcriptomic approaches are used to advance endometrial health.
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Department of Metabolism, Digestion and Reproduction, Imperial College London, London, UK
LogixX Pharma, Theale, Reading, Berkshire, UK
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Graphical abstract
Abstract
Infertility affects millions of couples worldwide. Oxidative stress (OS) causes peroxidation of lipids and damage to spermatozoa, thus, reducing the quality of seminal parameters. In addition, the differences in the levels of antioxidants and reactive oxygen species (ROS) caused by intrinsic and extrinsic variables linked to lifestyle, diet, genetics, and OS also contribute to male infertility. High levels of ROS result in sperm damage of sperm parameters due to lipid peroxidation and oxidation of proteins. Other significant causes of ROS include changes in sex hormone levels, sperm DNA damage, including mutations, and immature spermatozoa. Treating the root causes of OS, by changing one’s lifestyle, as well as antioxidant therapy, may be helpful strategies to fight OS-related infertility. However, the determination of male infertility induced by OS is currently a challenge in the field of reproductive health research. This review intends to describe the role of oxidative stress on male infertility and the current understanding of its management.
Lay summary
The inability to conceive affects many couples globally. Oxidative stress refers to imbalances between different oxygen species which can lead to male fertility problems by damaging sperm and semen. Oxidative stress may be caused by several factors, including diets high in fats, sugars and processed foods, lifestyle (including smoking, alcohol consumption and having a sedentary lifestyle), and genetics. Treatment that focuses on the root cause may help combat male infertility. However, there is currently no consensus on the best way to treat male fertility problems, particularly those associated with oxidative stress. This paper describes the role of oxidative stress on male infertility and discusses the current techniques employed in treating male fertility issues.
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Monash IVF Group, Sydney, NSW, Australia
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Graphical abstract
Abstract
Sperm cryopreservation is a valuable tool for the long-term preservation of male fertility. Thus, determining the optimal technique for isolating spermatozoa post-thaw is vital to ensure recovery of the highest quality spermatozoa with minimal iatrogenic damage. This not only enhances the chances of successful conception but also reduces the risk of genetic damage in the embryo. To address this issue, human semen samples were cryopreserved using a slow freezing protocol and Quinn's Advantage™ Sperm Freeze medium. The samples were subsequently thawed and subjected to three types of sperm isolation procedures: direct swim-up, density gradient centrifugation, and electrophoretic separation using the Felix™ device. Cryopreservation led to the anticipated loss of sperm motility and vitality in association with increases in lipid peroxidation and DNA damage. Following sperm selection, all three isolation techniques resulted in an increase in sperm motility which was particularly evident with the swim-up and Felix™ procedures. The latter also significantly improved sperm vitality. There were no differences between sperm separation techniques with respect to morphology, and mitochondrial reactive oxygen species generation remained essentially unchanged when cell vitality was taken into account. By contrast, major differences were observed in DNA integrity and lipid aldehyde formation, where Felix™ isolated cells exhibiting significantly less DNA damage than the other isolation procedures as well as lower levels of 4-hydroxynonenal formation. Electrophoretic sperm isolation, therefore, offers significant advantages over alternative separation strategies, in terms of the quality of the gametes isolated and the time taken to achieve the isolation.
Lay Summary
Long-term storage of sperm is vital to assisted reproductive technology because it permits the preservation of fertility that might be compromised as a result of factors such as chemotherapy or vasectomy. This goal can be achieved via cryopreservation – the freezing of cells to −196°C. When the sperm are subsequently required for conception, they must be carefully separated from the cryopreservation medium in a manner that maximizes the chances of successful conception and minimizes the risk of genetic defects in the offspring. In this paper, three isolation techniques were compared for their ability to separate ideal sperm from semen and media following cryopreservation. It was found that cryopreservation led to lower levels of motility and vitality and created higher levels of DNA and cell membrane damage. Of the three techniques compared, only cells separated on the basis of their size and electric charge (electrophoretic isolation) exhibited significantly lower levels of DNA fragmentation.
