Reproduction, Fertility and Development
A major limitation of IVF success is failure of the embryo to successfully attach to the womb. We have identified a critical new mechanism of communication between the human embryo and endometrium (inner lining of the uterus). Overall it is likely that this bi-directional communication facilitates the critical adhesion process during the initiation of successful pregnancy.
The types and copy numbers of very short so-called miRNA molecules were measured in eggs and embryos of cattle. Results highlight the importance of a non-canonical miRNA during stages before embryonic transcription begins, the influence of the parental origin of miRNAs and the importance of measuring absolute as opposed to relative levels of these molecules.
The Kiss1 gene plays a major role in reproductive seasonality of sheep. This study aimed to confirm that epigenetic modification occurs in sheep during the reproductive cycle. A potential role of histone acetylation modification in altering Kiss1 expression, which may consequently regulate seasonal breeding in sheep, was found. This study may offer a theoretical basis for breeding year-round oestrous sheep.
The testis-specific protein, Y-encoded, 1 (TSPY1) gene is a newly confirmed regulator of sperm production, and dosage deficiency of the multicopy gene confers increased risk of spermatogenic failure. The aim of the present study was to evaluate whether the autosomal homologous genes originating from TSPY1 modify the spermatogenic phenotype of TSPY1. The results suggest that phenotypic expression of TSPY1 defects is independent of variations TSPY-like 1 (TSPYL1) and TSPY-like 5 (TSPYL5), highlighting the significance of TSPY1 in the modulation of spermatogenic efficiency.
Due to fetal and neonatal bone tissue calcification, the maternal calcium demand increases during pregnancy and lactation. To supply this calcium demand, female mammals undergo numerous physiological changes during reproduction. In the present study, we performed a meta-analysis of studies reporting changes in bone mineral density, serum calcium and calciotropic hormone concentrations during pregnancy and lactation in mammals. The results provide a quantitative background to better explain and understand these physiological adaptations.
Female sperm storage is known across many animal phyla, but the mechanism(s) remains elusive. Using the Indian garden lizard, Calotes versicolor as a model, we identified a unique abundant protein of ~55-kDa in the uterovaginal region that controls the motility of the spermatozoa. These studies are likely to unravel the secrets of sperm storage.
The molecules that are involved in actin-based oocyte polar body extrusion are still largely unknown. In the present study we showed that knockdown of Profilin caused aberrant actin distribution, the failure of polar body extrusion and altered the expression of Rho-associated kinase (ROCK) and myosin light chain (MLC) 2. The results indicate that Profilin is related to ROCK–MLC2 for actin assembly in mouse oocytes.
Although giant pandas have been described as mono-oestrus spring breeders, males exposed to oestrous females outside this timeframe exhibit breeding behaviours and interest in mating. Urinary androgens and sperm parameters were quantified for males exposed to females expressing oestrus during spring, autumn, or winter. The data from this study showed a rapid physiological readiness of male giant pandas to mate in response to female oestrous cues within or outside of the normal breeding season and may suggest a facultative seasonal reproduction with a “female-induced rut”.
In vitro growth of secondary follicles isolated from the vitrified ovarian cortex allows a better understanding of their complex development and of obtaining healthy follicles. The aim of this study was to investigate how the medium composition affects the viability and growth rate of the isolated secondary follicles. This technique could become a strategy to preserve the reproductive potential of females.
Reduced fetal growth can contribute to a greater risk of later metabolic disease, but the key mechanisms remain unknown. Herein we report findings from a large animal model (sheep) in which fetal growth was restricted by reducing maternal food intake and show that once the offspring become obese, they exhibit increased abundance of molecular markers of metabolic stress in the fat and liver. This could represent a primary mechanism by which growth-restricted offspring are at greater risk of metabolic ill health in later life.
Equine immature oocytes are classified as expanded or compact and are matured in the laboratory to obtain offspring; higher maturation rates are reported for expanded oocytes. The aim of this study was to assess whether differences in the maturation capacity of these oocytes is related to differences in glucose uptake, metabolism or apoptosis. Consistent metabolic and genomic differences were found between expanded and compact oocytes: compact oocytes consumed more glucose but matured less than expanded oocytes. This indicates that the maturation requirements vary for compact and expanded oocytes.
The zona pellucida (ZP) is an extracellular matrix formed by few glycoproteins that covers the oocyte and plays an important role during fertilisation. The identification of ZP glycoproteins in carnivores is relevant for an understanding of sperm–ZP interactions and species specificity. In this study, molecular and in silico analyses demonstrated the presence of the ZP1 gene in four families (Felidae, Mustelidae, Odobenidae and Ursidae), whereas in three families (Canidae, Otariidae and Phocidae) ZP1 is pseudogenised. This information could be relevant for the development of more specific and efficient contraceptive vaccines for carnivores.
Inflammation plays an important role in the initiation of preterm birth, which remains the largest cause of neonatal deaths. In the present study, components of the protein synthesis machinery were significantly increased with labouring compared to non-labouring fetal membranes and myometrium, and blockade of protein synthesis significantly reduced inflammation in the myometrium. These results may provide further insight into the pathways involved in the initiation of preterm birth.
One of the predominant causes of anoestrus is a low level of ovarian oestrogens. Herein, we investigated the association of the oestrogen biosynthesis regulator CYP19A1 with the risk of anoestrus in buffaloes and found three SNPs. The risk alleles in these SNPs were significantly associated with lower levels of estradiol and antioxidants and higher incidence of oxidative ovarian damage and anoestrus.
A prolonged inflammatory response to breeding severely decreases fertility in horses. The aim of the present study was to evaluate differences between fertile and subfertile mares in the expression of selected genes associated with the immune response. Three of the genes analysed proved to be very sensitive and specific diagnostic markers predicting prolonged inflammation, and likely reduced fertility, prior to breeding.
This research provides new insight into central molecular mechanisms regulating GnRH/LH secretion in anestrous sheep. To better explain this problem, herein, we demonstrated that RF-amide peptides are involved in dopamine-induced inhibition of GnRH/LH secretion. Studies expanded an important issue in the field of neuroendocrinology of reproduction, especially in cognitive appraisals of mechanisms participating in physiological regulation of GnRH/LH biosynthesis.
Ovum pick-up and in vitro embryo production can be used in dairy heifers. However, production results are often disappointing when animals are underfed. A short-term dietary supplement with propylene glycol (400 mL of PG or water/drench, daily drenching at 1600 hours for the first 9 days of the oestrous cycle), given to feed-restricted heifers, was able to restore the expression of selected genes in cumulus cells and blastocysts to levels seen in correctly fed heifers.
Intracytoplasmic sperm injection (ICSI) has been successfully applied to hybrid mice, but not to inbred mice due to low efficiency. Adding an activation step to ICSI of oocytes from juvenile mice results in the birth of healthy inbred pups. The results of this study show that the modified protocol can potentially improve the efficiency of ICSI in inbred mice.
N-carbamylglutamate (NCG) and arginine (ARG) supplementation can increase litter size in pigs and rats, but their effects on gonadotrophin-releasing hormone (GnRH) secretion are unknown. We found that NCG and ARG can increase cell numbers and decrease GnRH secretion in murine immortalized GT1-7 cells in vitro by regulating related gene expression. These findings help us to better understand nutritional control of reproduction.
Juvenile in vitro embryo transfer (JIVET) can increase the gain rate by reducing the generation interval, but the low quality of these oocytes leads to poor embryo production. In this study we hypothesised that oocyte quality could be related to omega 3 (linolenic acid, ALA) and omega 6 (linoleic acid, LA) concentrations in follicular fluid. No differences were found in ALA and LA concentrations in relation to follicle diameter. The addition of a high LA (omega 6) concentration to the IVM medium impaired oocyte competence to develop up to the blastocyst stage.
Toll-like receptors (TLRs) contribute to an exclusive protection system in the uterus during the oestrus cycle; however, the importance of TLRs in tissue repair within the involuting uterus is not known. Herein we show that TLRs are constitutively expressed in uterine cells and that the localisation pattern of TLRs in the endometrium varies with structural changes in the involuting uterus. These results suggest that TLRs have a physiological role in the uterine remodelling events during the post partum involution period.
Assisted reproduction techniques such as in vitro fertilisation and embryo culture have been shown to affect the size and anatomy of the newborn and the placenta in some species, but no information is available on this area in the horse. We evaluated foals and placentas from pregnancies resulting from natural conception, embryo transfer and transfer of in vitro-produced (intracytoplasmic sperm injection) embryos and found no significant differences between groups in size or weight of the foal or placenta and no differences in expression of 17 genes controlling placental function. Our findings suggest that the horse embryo differs from that of ruminants in its sensitivity to the in vitro environment, supporting the continued use of assisted reproduction techniques for commercial foal production.
Extravillous trophoblast cells are one of the main elements that are affected by maternal smoking during pregnancy. Quantitative changes in extravillous trophoblast cells could be evidence for the hypothesis that changes in these cells could affect fetal health by changes in normal placentation.
Humans may be exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an environmental pollutant, via contaminated food, inhalation or skin contact. The effects of TCDD are exerted via binding to aryl hydrocarbon receptors (AhR). In this study we investigated the possible protective effect of resveratrol, an AhR antagonist, against testicular damage caused by TCDD exposure during pregnancy. The findings suggest that TCDD in combination with resveratrol results in more severe toxicity than administration of either drug alone.
Adiponectin may be a potent therapeutic agent for recovery of the polycystic ovary syndrome (PCOS) condition. The aim of the present study was to unravel the role of adiponectin in regulating reproduction, metabolism and fertility status in mice in which PCOS had been induced. Reversal of PCOS-like features following adiponectin treatment in mice is a major breakthrough with regard to the effective management of PCOS.
The testis is the organ essential for spermatogenesis and male fertility. This paper profiles differences in DNA methylation levels during prepubertal porcine testis development, and provides new insights into mammalian testis development and represents a foundation for additional research using the pig as a model animal.
Do extracellular vesicles have a biological role in the communication between the embryo and its microenvironment during in vitro culture? In this study we showed that embryos were able to incorporate microvesicles obtained from endometrium and amnion, but only amniotic progenitor cell-derived microvesicles resulted in better blastocyst production rate and quality compared to control. This study could be a useful starting point for further studies related to paracrine mechanisms of communication between embryos and the culture medium.
Nutritional perturbation during early gestation has been shown to alter male reproductive development in rodents and sheep. This study examined the effects of dietary protein perturbation during the peri-conception and first trimester periods upon reproductive development in both fetal and pubertal male bovine progeny. Low maternal dietary protein negatively impacted reproductive development in pubertal and postpubertal offspring. This research highlights that further studies are warranted to explore causal relationships between gestational nutrition and consequent postnatal male reproductive development in cattle.
It is not known whether female accessory reproductive organs that play a major role in reproduction are vulnerable to chronic stress effects. This study revealed irreversible oxidative stress in the Fallopian tube following short or long-term chronic stress exposure, whereas uterus changes were reversible following short-term exposure but not after long-term exposure. This study indicates that stress-induced reproductive failure may also be due to alterations in the accessory reproductive organs.
Kisspeptin peptide is a major regulator of initiation of pubertal actions in the central nervous system, but its development in growing animals is obscure. The presence of kisspeptin neurons in the brain from birth to puberty in relation to luteinising hormone release pattern was analysed in female lambs. Activity of kisspeptin neurons increased gradually parallel with augmentation of luteinising hormone release and reached maturation several weeks before puberty. The participation of kisspeptin in the development of the ovine reproductive processes is suggested.
The placenta is a multifunctional link between mother and fetus vital for nutrient transport. In this study we determined when and where nucleobindin-2/nesfatin-1 were located in the placenta and found them particularly in secretory trophoblast cells of the mouse and human placenta. The placenta should be considered a source for nucleobindin-2/nesfatin-1 during pregnancy, with possible roles in maternal glucose control and nutrient sensing.
Some genes are involved in stallion semen tolerance to cryopreservation. This work evaluated the relationship between CRISP-3 protein and some of its single nucleotide polymorphisms, with post-thawing semen quality in stallions. This study demonstrated that different parameters of seminal quality are influenced by the CRISP-3 genotype and the concentration of this protein in seminal plasma.
The preimplantation period of pregnancy is a critical period for determining growth of the conceptus. This study examined the use of progesterone treatment as a means of overcoming maternal constraint effects on embryo growth. Exogenous progesterone was found to indirectly advance embryo growth via alteration of endometrial genes that encode for uterine structural and secretory activity and thereby overcome maternal constraint.
The zona pellucida (ZP) is an extracellular matrix formed by a few glycoproteins that covers the oocyte and plays an important role during fertilization. The identification of the components of the ZP in marsupials is relevant for the cellular understanding of female gamete formation, sperm interaction with the ZP and fertilisation. Molecular and in silico analyses demonstrated a different ZP composition between Australasian and South American marsupials, being formed from four to six proteins. The present findings have potential relevance from a biological, ecological and economic point of view, related to the development of new contraceptive vaccines for marsupials.
This article contributes to a better understanding of which transcripts are involved in early embryonic development, when the embryos still rely on the maternal genetic component and after they activate their own genome. We identified the thyroid hormone receptor, especially the β-subunit, as one of the few genes transcribed before major embryonic genome activation with an essential role for development.
Genetic background can help to explain idiopathic cases of recurrent pregnancy loss (RPL), which make up about 50% of total cases. Here, we have evaluated the genetic profiles of women experiencing RPL by analysing polymorphisms in the NOS2, PTGS2 and VEGFA genes. We found a higher incidence of a polymorphic variant in the NOS2 gene in the RPL group, suggesting a role for this gene in RPL risk, possibly due to oxidative stress mechanisms.
To improve current infertility treatments, it is necessary to evaluate uterine receptivity in each menstrual cycle. If this can be evaluated beforehand, when uterine receptivity is inadequate eggs could be stored using cryopreservation. In this study in a mouse model, we identified an electrophysiological parameter that can evaluate uterine receptivity prospectively.
Hormones in plants may provide an important trigger for activating breeding activity in Kākāpō, a critically endangered New Zealand parrot. By comparing native and Australian parrots for their ability to respond to steroid hormones, we discovered novel sequences in the receptivity of parrots to oestrogenic compounds. Receptor modeling revealed that altered interactions with plant oestrogens in parrots may enhance the physiological pathways linked to fertility and successful breeding.
For wild rodents such as the agoutis, the combination of gonadal tissue cryopreservation and xenotransplantation could help promote germplasm conservation and reproduction, especially in the case of genetically valuable individuals. The present study demonstrates that xenografted agouti ovarian tissue, fresh or vitrified, is able to promote the return of ovarian activity in ovariectomised SCID C57B1/6 mice.
Tumor suppressor protein p53, known widely as the guardian of genome preventing cancer formation, is also involved in physiological apoptosis of germ cells in testes. The study used a mouse model to reveal that germ cell apoptosis during the first round of spermatogenesis can be efficiently mediated by p53-independent mechanisms, but activation of these mechanisms requires engagement of multicopy Y-chromosome long arm genes. The role of Y-chromosome genes in regulation of testicular apoptosis was demonstrated for the first time.
Fertilisation and development of the mammalian egg is still not well understood, illustrated by low efficiencies of assisted reproductive technologies. The role of a cell membrane receptor for calcium (CASR) was studied, using pig spermatozoa and eggs as models. Significant effects were demonstrated by stimulating this receptor at different steps of the process. These findings are useful for future basic and applied research.
Angiogenesis is a vital process in the development and survival of lesions during endometriosis. In the present study we identified upregulation of several isoforms of vascular endothelial growth factor (VEGF) A in the endometrium of women with endometriosis during menstruation and, for the first time, identified the natural expression of the VEGF111 isoform in humans. These findings contribute to our understanding of how the endometrium differs in women with endometriosis, and indicates a dysregulation at the critical time of menstruation.
Activin C can delay the growth of mouse granulosa cell tumours, but little is known about its function in normal ovaries. This study shows that activin C protein is expressed in normal mouse and human ovaries, and can delay the development of abnormal follicles in mice lacking inhibin, but does not appear to alter normal follicle growth in the mouse. This study provides evidence of a role for activin C in the ovary.
Prostate development and function are altered by early postnatal exposure to prolactin imbalance. Prolactin modulation interferes with the determination of ventral prostate development and maturation through a mechanism of increasing the epithelial proliferative response and dynamics of cell differentiation. Changes in prostate morphophysiology after prolactin modulation could affect glandular function and the incidence of disorders associated with aging.
Milk fat globule-EGF factor 8 protein (MFGE8) is a protein that promotes cell to cell adhesion and is thought to play an essential role in embryo implantation in mice and humans. We have described the expression of MFGE8 in the equine uterus and found particular strong expression of the protein by the fetal portion of the placenta. These results imply a role for MFGE8 in maintaining an intact placenta during mare pregnancy.
The role of melatonin as an endocrine regulator of reproductive activity is well known; however, whether it stimulates or inhibits reproductive function varies across species. We demonstrated that in vitro exposure to melatonin reduced steroid production by ovarian theca cells in cattle, implicating melatonin as a regulator of reproductive function in cattle. Because reduced reproductive capacity leads to economic losses, an understanding of the effects of melatonin on ovarian function may lead to new ways to increase reproductive efficiency in cattle.
Juvenile in vitro embryo transfer (JIVET) can increase the genetic gain rate by reducing the generation interval, but the low quality of the oocytes and higher oxidative levels leads to poor embryo production. In the present study we hypothesised that melatonin could be a suitable tool for improving oocyte competence in juvenile goats. The results show that melatonin is present in the follicular fluid in juvenile goats and its addition to the in vitro maturation medium reduces oxidation and increases embryo development showing its potential role for JIVET.
Taking advantages of the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (Cas) 9 system, we achieved a precise single-nucleotide substitution in the growth differentiation factor 9 (GDF9) gene using a single-stranded oligo deoxynucleotide as a homology-dependent repair template with a relatively high efficiency in order to increase litter size in goats. The present study provides an alternative approach for introducing defined point mutations in large animal models for the improvement of significant traits, as well as for the functional validation of key variants.
The application of genome storage in conservation is severely constrained by our limited access to reliable assisted breeding techniques. This is particularly so for marsupials, in which the corpus luteum, and thus cycling, is not affected by agents used to control ovarian function in eutherian mammals. Herein we report progress on the use of a single-treatment long-acting suppressor of pituitary function to reset cycling and ovulation in a marsupial.
Signalling pathways responsible for follicular activation in the mare remain uncharacterised. Messenger RNA expression and protein localisation of members of the PI3K/AKT and JAK/STAT pathways were analysed using tissue from fetal and adult mare ovaries. Findings suggest that members of these pathways are indeed present and may serve as useful biomarkers for assessment of ovary development in the horse.
The forkhead box (Fox) gene family encodes multiple forkhead proteins that exhibit marked functional diversity and are involved in biological processes, especially sex differentiation. The identification, characterisation, selective pressure, protein structure and expression pattern of Fox genes in response to temperature were investigated in the present study in the Chinese giant salamander Andrias davidianus to enrich the sexual development and reproduction mechanism in amphibian.
During cryopreservation, spermatozoa undergo cryodamage because of membrane changes, including sterol loss, which results in diminished post-thaw fertilisation ability. The present study showed that loading of cholesterol and desmosterol into chicken spermatozoa prior to cryopreservation enhanced their post-thaw quality by inhibiting apoptotic changes and premature acrosome reaction, providing new mechanistic insight into cryodamage in chicken spermatozoa.
During preimplantation development, the bovine embryo is free floating in oviduct and uterine fluids. We aimed to mimic the physiological conditions of the maternal environment in the present study by supplementing serum-free embryo culture medium in vitro with both fluids sequentially. The results revealed that low concentrations of oviduct and uterine fluids support early embryo development and improve blastocyst quality.
Uncontrolled inflammation of the oviduct can result in tubal occlusion and infertility. This inflammation is often in response to infection with sexually transmitted bacterial pathogens. This study describes how the endotoxin from Escherichia coli-derived lipopolysaccharide affects the expression of inflammatory mRNAs and post-transcriptionally modifying miRNAs within the oviduct, providing novel insight into the molecular regulation of inflammation within this key reproductive organ.
The reason why some spermatozoa reach the site of fertilisation where others fail is not known, but interaction between spermatozoa and the female environment is key. We profiled ‘winner’ and ‘loser’ spermatozoa and found that the sugars on their surface and their susceptibility to immune cell attack differed significantly. This helps to explain both normal reproductive physiology and the consequences of human intervention.