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In November 2021, NICE updated its clinical guideline that covers the management of threatened miscarriage in the first trimester. They recommended offering vaginal micronised progesterone twice daily until 16 completed weeks of pregnancy in those with a previous miscarriage. However, the duration of treatment is not evidence based. In the major clinical trial that informed the guideline, there was no benefit in starting progesterone after 9 weeks and the full effect of progesterone was present at 12 weeks of pregnancy. There are theoretical risks impacting offspring health in later life after maternal pharmaceutical progesterone treatment. As the effect of progesterone seems to be complete by 12 weeks of gestation, we should consider carefully whether to follow the guidance and treat up to 16 weeks of pregnancy.
Lay summary
In November 2021, new guidelines were published about the management of bleeding in early pregnancy. If someone who has had a previous miscarriage starts bleeding, they should now be treated with progesterone as this slightly reduces the chance of miscarriage. The guideline says progesterone should be given if the pregnancy is in the womb, and potentially normal, until 16 weeks of pregnancy. However, in the big studies looking at progesterone’s effect in reducing miscarriage the beneficial effects of progesterone were complete by 12 weeks of pregnancy. At that stage, it is the placenta and not the mother’s ovary that makes the progesterone to support the pregnancy. We do not know the long-term effects of giving extra progesterone during pregnancy on the offspring. Some research has raised the possibility that there might be some adverse effects if progesterone is given for too long. Maybe the guidance should have suggested stopping at 12 weeks rather than 16 weeks of pregnancy.
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Endometriosis is a chronic neuro-inflammatory disorder the defining feature of which is the growth of tissue (lesions) that resembles the endometrium outside the uterus. Estimates of prevalence quote rates of ~10% of women of reproductive age, equating to at least 190 million women world-wide. Genetic, hormonal and immunological factors have all been proposed as contributing to risk factors associated with the development of lesions. Twin studies report the heritable component of endometriosis as ~50%. Genome-wide association studies (GWAS) have identified single nucleotide polymorphisms (SNPs) that appear over-represented in patients with endometriosis, particularly those with more extensive disease (stage III/IV). In different sample populations, there has been replication of SNPs near genes involved in oestrogen and other steroid regulated pathways including ESR1 (oestrogen receptor alpha), GREB1, HOXA10, WNT4 and MAPK kinase signalling. Comparisons with GWAS conducted on other patient cohorts have found links with reproductive traits (age at menarche) and disorders (fibroids, endometrial and ovarian cancer) and common co-morbidities (migraine, depression, asthma). In summary, genetic analyses have provided new insights into the hormone-regulated pathways that may contribute to increased risk of developing endometriosis some of which may act in early life. New studies are needed to clarify the relationship between the many SNPs identified, the genes that they regulate and their contribution(s) to development of different forms of endometriosis. We hope that more advanced methods allowing integration between GWAS, epigenetic and tissue expression data will improve risk analysis and reduce diagnositic delay.
Lay summary
Endometriosis is a debilitating reproductive disorder affecting ~10% of reproductive-age women, and those assigned female at birth, which causes a range of symptoms including chronic pain and infertility. The reason why some, but not all these individuals, develop the lesions that characterise the disease are poorly understood, but recently attention has focused on genetic risk factors to explain why the incidence is higher in some families. Studies on large cohorts of patients with comparison of their DNA to women without endometriosis or with other disorders have documented changes in genes associated with steroid hormone production or action. The results provide further evidence that endometriosis shares genetic risk factors with other disorders of the reproductive system and a platform for new ideas related to risk, biomarkers and therapies.
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Objective
To present an overview of different approaches and recent advances for long-term preservation of germ cells and gonadal tissues at ambient temperatures.
Methods
Review of the existing literature.
Results
Preserving viable spermatozoa, eggs, embryos, and gonadal tissues for the long term is critical in human fertility treatment and for the management of animal populations (livestock, biomedical models, and wild species). The need and number of banked germplasms are growing very fast in all disciplines, but current storage options at freezing temperatures are often constraining and not always sustainable. Recent research indicates that structures and functions of gametes or gonadal tissues can be preserved for the long term using different strategies based on dehydration and storage at supra-zero temperatures. However, more studies are needed in rehydration and reanimation of germplasms (including proper molecular and cellular evaluations).
Conclusions
While a lot of research is still warranted to optimize drying and rehydration conditions for each sample type and each species, alternative preservation methods will change the paradigm in fertility preservation and biobanking. It will transform the way we maintain and manage precious biomaterials for the long term.
Lay summary
Living sperm cells, eggs, embryos, and reproductive tissues can be preserved at freezing temperatures for human fertility treatments and used to manage breeding in livestock, laboratory animals, and wild species through assisted reproduction. These cells can be stored in cell banks and demand for them is growing fast. However, current long-term storage options at freezing temperatures are expensive. Instead of using low temperatures, recent research indicates that these cells can be dried and stored above freezing temperatures for an extended amount of time. While a lot of research is still needed to optimize how different samples are dried and rehydrated, alternative methods of preserving cells will make fertility preservation and cell banking easier. It will also transform the way we keep and manage samples for the long term.
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Sperm motility varies between ejaculates from different men and from individual men. We studied normozoospermic and asthenozoospermic ejaculates after density-gradient centrifugation washing (DCG, 80/40%) and compared high- (80%) and low (40%)-motility sperm populations within the same sample. Our objective was to identify differences in endogenous metabolomes and energy metabolism in relation to sperm motility. 1H-Nuclear Magnetic Resonance spectroscopy (NMR) measured the endogenous metabolome of live human sperm. Incubating sperm with 13C-labelled substrates detected energy metabolism by 13C-NMR. The study examined 850 ejaculates and diagnosed asthenozoospermia in 6.1%. DGC was used to wash 160 normozoospermic (N) and 52 asthenozoospermic (A) ejaculates to recover high-motility sperm from the pellet (80N/80A) and low motility from the interface (40N/40A). 1H-NMR spectra, 45(N) and 15(A), were binned and the integrals normalised by sperm concentration. Sperm from 126(N) and 36(A) ejaculates were incubated with either 13C-glucose, 13C-fructose or 13C-pyruvate. 13C-NMR lactate and bicarbonate integrals were normalised by motile or vital sperm concentrations. 1H-NMR spectra choline integrals from the 80A population were significantly lower than the 80N, P < 0.0001. 13C-substrate conversion to lactate was significantly higher for 40A sperm than 80A sperm when normalised by motile sperm concentration. Bicarbonate integrals were sporadically observed. Sperm from asthenozoospermic ejaculates had similar glycolytic requirements to normozoospermic ones, with larger differences observed between 40 and 80% sperm populations. Higher lactate levels produced by 40% sperm may indicate that impaired sperm motility is due to dysregulated energy metabolism. The alteration in choline metabolism provides opportunities to understand the aetiology of asthenozoospermia.
Lay summary
How well sperm swim (motility) varies between ejaculates from different men? Normal sperm motility is beneficial to conception and some men diagnosed with infertility have low sperm motility. Sperm metabolise molecules to produce the energy required for motility. We measured concentrations of molecules within sperm and metabolism of molecules given to sperm and related these to the proportion of motile sperm. The study examined 850 sperm samples and found low motility in 6.1%. Metabolism of molecules given to sperm was similar between low and normal motility sperm samples. However, when the most motile sperm were separated from the rest, they were more efficient in metabolising these molecules to achieve motility. Lower concentrations of a molecule called choline were found in low-motility sperm samples compared to normal samples. Choline is associated with cell membranes, energy metabolism and oxidative stress, which may give opportunities to understand the causes of low motility.
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Some human preimplantation embryos are chromosomally mosaic. For technical reasons, estimates of the overall frequency vary widely from <15 to >90% and the true frequency remains unknown. Aneuploid/diploid and aneuploid/aneuploid mosaics typically arise during early cleavage stages before the embryonic genome is fully activated and when cell cycle checkpoints are not operating normally. Other mosaics include chaotic aneuploid mosaics and mixoploids, some of which arise by abnormal chromosome segregation at the first cleavage division. Chimaeras are similar to mosaics, in having two genetically distinct cell populations, but they arise from more than one zygote and occur less often. After implantation, the frequency of mosaic embryos declines to about 2% and most are trisomic/diploid mosaics, with trisomic cells confined to the placenta. Thus, few babies are born with chromosomal mosaicism. This review discusses the origin of different types of chromosomal mosaics and chimaeras; their fate and the relationship between preimplantation chromosomal mosaicism and confined placental mosaicism in human conceptuses and animal models. Abnormal cells in mosaic embryos may be depleted by cell death, other types of cell selection or cell correction but the most severely affected mosaic embryos probably die. Trisomic cells could become restricted to placental lineages if cell selection or correction is less effective in placental lineages and/or they are preferentially allocated to a placental lineage. However, the relationship between preimplantation mosaicism and confined placental mosaicism may be complex because the specific chromosome(s) involved will influence whether chromosomally abnormal cells survive predominately in the placental trophoblast and/or placental mesenchyme.
Lay summary
Human cells normally have 23 pairs of chromosomes, which carry the genes. During the first few days of development, some human embryos are chromosomal mosaics. These mosaic embryos have both normal cells and cells with an abnormal number of chromosomes, which arise from the same fertilised egg. (More rarely, the different cell populations arise from more than one fertilised egg and these embryos are called chimaeras.) If chromosomally abnormal cells survive to term, they could cause birth defects. However, few abnormal cells survive and those that do are usually confined to the placenta, where they are less likely to cause harm. It is not yet understood how this restriction occurs but the type of chromosomal abnormality influences which placental tissues are affected. This review discusses the origin of different types of chromosomally abnormal cells, their fate and how they might become confined to the placenta in humans and animal models.
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Centre de Recherche du Centre Hospitalier de l’Université de Montréal (CRCHUM), CHUM Research Center, Montreal, Quebec, Canada
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Université Picardie Jules Verne, Médecine et Biologie de la Reproduction et Laboratoire PERITOX, CBH-CHU Amiens Picardie, Amiens, France
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Male Infertility Oxidative System (MiOXSYS) has been proposed as a rapid and promising technology for the evaluation of sperm oxidative stress. In this case–control study, 134 men with normal sperm parameters (NSP) and 574 men with abnormal sperm parameters (ASP), according to the World Health Organization sperm assessment references values established in 2010, were enrolled. Conventional sperm parameters were evaluated in all patients. Sperm static oxido-reduction potential (sORP) was assessed using the MiOXSYS. Sperm DNA integrity was measured in 604 patients. To ensure that sperm concentration was not a confounding factor in the sORP index ratio, sperm and seminal fluid sORP from 57 randomly selected additional patients were also measured using the MiOXSYS. sORP index (mV/106 sperm/mL) was higher in patients with ASP and seemed to correlate with conventional sperm parameters. Although receiver-operating characteristic analysis revealed that a sORP index cut-off of 0.79 could differentiate normal from ASP with 57.7% sensitivity and 73.1% specificity, these values are much lower than those found in the literature. These values also need to be higher to be applicable in a clinical setting. Furthermore, absolute sORP (mV) was not different in the presence or absence of spermatozoa. sORP index relationships with sperm parameters seem rather be due to sperm concentration, denominator of the sORP index ratio. The establishment of a reliable method using the absolute sORP value, independent of sperm concentration, needs to be addressed. Other oxidative stress biomarkers could be used to validate this method.
Lay summary
The World Health Organization (WHO) has recognized that oxidative stress may have a role in male infertility. Oxidative stress happens when there is an imbalance between the production of molecules containing oxygen and the antioxidants, molecules that neutralize the molecules containing oxygen. The molecules containing oxygen can cause damage to sperm DNA. This damage can be measured using a particular index and this study looked at whether the concentration of the sperm sample might have an impact on results and suggests this should be taken into consideration by clinicians and researchers.
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Endometriosis is a chronic, multisystemic disease often presenting with significant phenotypic variation amongst patients. The impact of race/ethnicity on the prevalence of endometriosis, as well as disease presentation, is a question of interest which has been explored for the last century. This narrative review explores the historical perspective of endometriosis and race/ethnicity as well as the evidence available to date. Furthermore, we discuss the potential implication of the bias perpetuated on this topic, specifically in the areas of medical education, research, and clinical care. In consideration of these intersecting realms, we suggest priorities for future consideration of race/ethnicity as it pertains to the delivery of care for endometriosis patients.
Lay summary
The relationship between race/ethnicity and endometriosis has been explored for over a century. Historical bias and poorly conducted research have led to the idea that this condition is less likely to be diagnosed in certain racial groups, such as Black women. We review the current state of evidence and highlight important limitations within medical education and research on this topic. Finally, we advocate for a shifting viewpoint as we strive to deliver equitable and outstanding care for all endometriosis patients.
Liverpool Women’s NHS Foundation Trust, Member of Liverpool Health Partners, Liverpool, UK
Hewitt Centre for Reproductive Medicine, Liverpool Women’s NHS Foundation Trust, Liverpool, UK
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Hewitt Centre for Reproductive Medicine, Liverpool Women’s NHS Foundation Trust, Liverpool, UK
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Liverpool Women’s NHS Foundation Trust, Member of Liverpool Health Partners, Liverpool, UK
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Liverpool Women’s NHS Foundation Trust, Member of Liverpool Health Partners, Liverpool, UK
Hewitt Centre for Reproductive Medicine, Liverpool Women’s NHS Foundation Trust, Liverpool, UK
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Graphical abstract
Abstract
Recurrent reproductive failure (RRF) encompasses recurrent implantation failure (RIF) and recurrent pregnancy loss (RPL). These highly prevalent, distressing conditions have many unanswered questions regarding aetiology and management. Oestrogen receptor beta (ERβ) is the predominant oestrogen receptor expressed in the vascular endothelium of the endometrium during the window of implantation (WOI). The establishment of normal endometrial receptivity is integrally associated with progesterone receptor (PR). Therefore, we aimed to investigate whether women with RRF have clinical, type-specific endometrial aberrations of ERβ, PR and Ki-67 expression during the WOI. Thirty-eight endometrial biopsies were collected; 29 RRF (10 RIF, 9 recurrent loss of early pregnancy (RLEP) and 10 recurrent fetal loss (RFL)) and 9 fertile controls (FC). Within RIF, RLEP and RFL groups, the perivascular compartment showed significantly lower levels of ERβ vs FC (P = 0.02, P = 0.03 and P = 0.01, respectively). Vascular endothelium also displayed significantly lower levels of ERβ within RIF and RFL cohorts vs FC (P = 0.03 and P = 0.003). The expression of Ki-67 was significantly lower within vascular endothelium of all RRF; RIF (P = 0.02), RLEP (P = 0.02) and RFL (P <0.01). PR was significantly reduced (P <0.001) in the perivascular area of women with RIF. These findings provide novel insights into biological correlates of clinical subtypes of RRF. The endometrium of women with RRF display significantly altered levels of ERβ, PR and Ki-67 during the WOI, furthering our understanding of the defective endometrial phenotype of women suffering from RRF, with possible impaired glandular function, angiogenesis and decidualisation.
Lay summary
Recurrent reproductive failure (RRF) refers to a group of devastating conditions with many unanswered questions regarding their causes and treatment options. The lining of the womb, the endometrium, is primed and suitable for successful embryo implantation for a short time during the menstrual cycle; the window of implantation (WOI). Oestrogen is a key hormone that plays an important role in regulating the endometrium and its effects are exerted via two oestrogen receptor subtypes. Oestrogen receptor beta (ERβ) is the main oestrogen receptor present during the WOI. Progesterone receptor allows the other main hormone, progesterone, to influence the endometrial activity and Ki-67 reflects the proliferative activity of the cells within the endometrium. We investigated the expression of these markers in endometrial samples collected from women with RRF and proven fertility. We found that the endometrium of women with RRF has significantly lower levels of ERβ and Ki-67 during the WOI, possibly leading to unsuccessful pregnancies.
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We have previously shown that implantation of testis cell aggregates under the back skin of immunodeficient mice results in de novo regeneration of testis tissue. We used this unique model to investigate the effects of epidermal growth factor (EGF) and glial cell-derived neurotrophic factor (GDNF) on testis cord development. Neonatal piglet testis cells were briefly (<1 h) exposed to either low (L: 0.02 μg/mL) or high (H: 2 μg/mL) doses of EGF, GDNF, or vehicle (control), before implantation in recipient mice. Randomly selected implants were removed from each mouse at 1, 2, 4, and 8 weeks post-implantation. GDNF-L implants showed increased testis cord development over time, and EGF-L implants had increased cross-sectional area. The ratio of regular cords decreased over time in EGF-H and GDNF-H implants and was replaced by a higher ratio of irregular cords in GDNF-H. EGF-L and GDNF-H implants were quickest to display rete testis-like structures. Overall, the lower dose of each growth factor was more effective than its higher dose in improving the implantation outcomes. This is the first comprehensive assessment of these key growth factors on de novo formation (regeneration) of testis tissue.
Lay summary
In recent decades, testicular cancer rates have quadrupled in young men while sperm counts have dropped by half. Both conditions may be related to exposure of fetuses or infants to noxious substances causing disruption of normal testis development. To study the effects of any putative factor on testis development, we established an animal model of testis tissue regeneration. We collected newborn piglet testes after routine castration, used enzymes to completely dissociate testis cells, exposed the cells to two key growth factors (EGF or GDNF), and implanted the cells under the back skin of recipient mice, acting as live incubators. We then examined implant samples after 1, 2, 4, or 8 weeks and assessed testis regeneration. Overall, the high dose of each growth factor had adverse effects on the formation of normal testis. Therefore, this novel implantation model may also be used to study the effects of potentially harmful substances on testis development.
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Nuffield Department of Women’s and Reproductive Health, University of Oxford, Oxford, UK
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Lipids are dynamic biological molecules that play key roles in metabolism, inflammation, cell signalling and structure. They are biologically significant in the physiology of conception and reproduction. Many of the mechanisms surrounding equine conception and the early feto-maternal dialogue are yet to be understood at a biochemical level. Recently, lipidomic technologies have advanced considerably and analytical strategies have been enhanced and diversified. Consequently, in-depth lipidomic exploration now has the potential to reveal new lipid biomarkers and biochemical relationships that improve our understanding of the processes leading to efficient and successful reproduction. This review considers the role of lipids in conception and establishment of pregnancy, providing new insights into the enigmatic pathways governing early reproductive physiology of the mare.
Lay summary
This paper discusses the role that lipids play in the very early stages of pregnancy in the mare. Lipids are microscopic non-soluble molecules that are important components of living cells. The manuscript discusses how lipids influence the reproductive cycle of mares, including ovulation and the detailed biological process of becoming pregnant. It explains how lipids are identified in a laboratory setting with a newly developing technology known as ‘lipodomics’. The technology may lead to a more detailed understanding of how mares become pregnant. The focus of the paper is on mare reproduction, but it also draws on similarities with reproduction in other mammals. Remarkably there are gaps in much of our knowledge about the finer details of pregnancy in the horse, and the paper summarises what we already know about lipids, highlighting areas for further research.
