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Human Fertility (Cambridge, England) Oct 2023Ovarian stimulation is a fundamental step in assisted reproductive technology (ART) with the intention of inducing ovarian follicle development prior to timed... (Review)
Review
Ovarian stimulation is a fundamental step in assisted reproductive technology (ART) with the intention of inducing ovarian follicle development prior to timed intercourse or intra-uterine insemination and facilitating the retrieval of multiple oocytes during a single in vitro fertilization (IVF) cycle. The basis of ovarian stimulation includes the administration of exogenous gonadotropins, with or without pre-treatment with oral hormonal therapy. Gonadotropin-releasing hormone agonist or antagonist is given in addition to the gonadotropins to prevent a premature rise of endogenous luteinizing hormone that would in turn lead to premature ovulation. With the advancement in technology, various stimulation protocols have been devised to cater for different patient needs. However, ovarian hyperstimulation syndrome and its serious complications may occur following ovarian stimulation. It is also evident that suboptimal ovarian stimulation strategies may have a negative impact on oogenesis, embryo quality, endometrial receptivity, and reproductive outcomes over recent years. This review describes the various forms of pre-treatment for ovarian stimulation and stimulation protocols, and aims to provide clinicians with the latest available evidence.
Topics: Female; Humans; Gonadotropin-Releasing Hormone; Ovulation Induction; Reproductive Techniques, Assisted; Gonadotropins; Fertilization in Vitro
PubMed: 37980170
DOI: 10.1080/14647273.2023.2261627 -
Development (Cambridge, England) Oct 2023Obesity is linked to reduced fertility in various species, from Drosophila to humans. Considering that obesity is often induced by changes in diet or eating behavior, it...
Obesity is linked to reduced fertility in various species, from Drosophila to humans. Considering that obesity is often induced by changes in diet or eating behavior, it remains unclear whether obesity, diet, or both reduce fertility. Here, we show that Drosophila females on a high-sugar diet become rapidly obese and less fertile as a result of increased death of early germline cysts and vitellogenic egg chambers (or follicles). They also have high glycogen, glucose and trehalose levels and develop insulin resistance in their fat bodies (but not ovaries). By contrast, females with adipocyte-specific knockdown of the anti-obesity genes brummer or adipose are obese but have normal fertility. Remarkably, females on a high-sugar diet supplemented with a separate source of water have mostly normal fertility and glucose levels, despite persistent obesity, high glycogen and trehalose levels, and fat body insulin resistance. These findings demonstrate that a high-sugar diet affects specific processes in oogenesis independently of insulin resistance, that high glucose levels correlate with reduced fertility on a high-sugar diet, and that obesity alone does not impair fertility.
Topics: Animals; Humans; Female; Drosophila melanogaster; Insulin Resistance; Trehalose; Obesity; Diet; Drosophila; Fertility; Glucose; Glycogen
PubMed: 37795747
DOI: 10.1242/dev.201769 -
BioEssays : News and Reviews in... Oct 2023The ovarian reserve defines female reproductive lifespan, which in humans spans decades. The ovarian reserve consists of oocytes residing in primordial follicles...
The ovarian reserve defines female reproductive lifespan, which in humans spans decades. The ovarian reserve consists of oocytes residing in primordial follicles arrested in meiotic prophase I and is maintained independent of DNA replication and cell proliferation, thereby lacking stem cell-based maintenance. Largely unknown is how cellular states of the ovarian reserve are established and maintained for decades. Our recent study revealed that a distinct chromatin state is established during ovarian reserve formation in mice, uncovering a novel window of epigenetic programming in female germline development. We showed that an epigenetic regulator, Polycomb Repressive Complex 1 (PRC1), establishes a repressive chromatin state in perinatal mouse oocytes that is essential for prophase I-arrested oocytes to form the ovarian reserve. Here we discuss the biological roles and mechanisms underlying epigenetic programming in ovarian reserve formation, highlighting current knowledge gaps and emerging research areas in female reproductive biology.
Topics: Humans; Pregnancy; Female; Mice; Animals; Meiosis; Ovarian Reserve; Oocytes; Chromatin; Epigenesis, Genetic
PubMed: 37417392
DOI: 10.1002/bies.202300069 -
ELife Nov 2023An animal's responses to environmental cues are critical for its reproductive program. Thus, a mechanism that allows the animal to sense and adjust to its environment...
An animal's responses to environmental cues are critical for its reproductive program. Thus, a mechanism that allows the animal to sense and adjust to its environment should make for a more efficient reproductive physiology. Here, we demonstrate that in specific sensory neurons influence onset of oogenesis through insulin signaling in response to food-derived cues. The chemosensory neurons ASJ modulate oogenesis onset through the insulin-like peptide (ILP) INS-6. In contrast, other sensory neurons, the olfactory neurons AWA, regulate food type-dependent differences in fertilization rates, but not onset of oogenesis. AWA modulates fertilization rates at least partly in parallel to insulin receptor signaling, since the insulin receptor DAF-2 regulates fertilization independently of food type, which requires ILPs other than INS-6. Together our findings suggest that optimal reproduction requires the integration of diverse food-derived inputs through multiple neuronal signals acting on the germline.
Topics: Animals; Caenorhabditis elegans; Insulin; Receptor, Insulin; Caenorhabditis elegans Proteins; Sensory Receptor Cells; Fertilization
PubMed: 37975568
DOI: 10.7554/eLife.83224 -
ELife Dec 2023Changes in the intracellular concentration of free calcium (Ca) underpin egg activation and initiation of development in animals and plants. In mammals, the Ca release...
Changes in the intracellular concentration of free calcium (Ca) underpin egg activation and initiation of development in animals and plants. In mammals, the Ca release is periodical, known as Ca oscillations, and mediated by the type 1 inositol 1,4,5-trisphosphate receptor (IPR1). Another divalent cation, zinc (Zn), increases exponentially during oocyte maturation and is vital for meiotic transitions, arrests, and polyspermy prevention. It is unknown if these pivotal cations interplay during fertilization. Here, using mouse eggs, we showed that basal concentrations of labile Zn are indispensable for sperm-initiated Ca oscillations because Zn-deficient conditions induced by cell-permeable chelators abrogated Ca responses evoked by fertilization and other physiological and pharmacological agonists. We also found that chemically or genetically generated eggs with lower levels of labile Zn displayed reduced IPR1 sensitivity and diminished ER Ca leak despite the stable content of the stores and IPR1 mass. Resupplying Zn restarted Ca oscillations, but excessive Zn prevented and terminated them, hindering IPR1 responsiveness. The findings suggest that a window of Zn concentrations is required for Ca responses and IPR1 function in eggs, ensuring optimal response to fertilization and egg activation.
Topics: Male; Animals; Mice; Oocytes; Semen; Oogenesis; Fertilization; Spermatozoa; Calcium; Calcium Signaling; Mammals
PubMed: 38099643
DOI: 10.7554/eLife.88082 -
Life (Basel, Switzerland) Jun 2024The phosphoinositide 3-kinase (PI3K)/Akt pathway is a key signaling cascade responsible for the regulation of cell survival, proliferation, and metabolism in the ovarian... (Review)
Review
The phosphoinositide 3-kinase (PI3K)/Akt pathway is a key signaling cascade responsible for the regulation of cell survival, proliferation, and metabolism in the ovarian microenvironment. The optimal finetuning of this pathway is essential for physiological processes concerning oogenesis, folliculogenesis, oocyte maturation, and embryo development. The dysregulation of PI3K/Akt can impair molecular and structural mechanisms that will lead to follicle atresia, or the inability of embryos to reach later stages of development. Due to its pivotal role in the control of cell proliferation, apoptosis, and survival mechanisms, the dysregulation of this molecular pathway can trigger the onset of pathological conditions. Among these, we will focus on diseases that can harm female fertility, such as polycystic ovary syndrome and premature ovarian failure, or women's general health, such as ovarian cancer. In this review, we report the functions of the PI3K/Akt pathway in both its physiological and pathological roles, and we address the existing application of inhibitors and activators for the balancing of the molecular cascade in ovarian pathological environments.
PubMed: 38929705
DOI: 10.3390/life14060722 -
International Journal of Molecular... Dec 2023The oocyte transcriptome follows a tightly controlled dynamic that leads the oocyte to grow and mature. This succession of distinct transcriptional states determines... (Meta-Analysis)
Meta-Analysis Review
The oocyte transcriptome follows a tightly controlled dynamic that leads the oocyte to grow and mature. This succession of distinct transcriptional states determines embryonic development prior to embryonic genome activation. However, these oocyte maternal mRNA regulatory events have yet to be decoded in humans. We reanalyzed human single-oocyte RNA-seq datasets previously published in the literature to decrypt the transcriptomic reshuffles ensuring that the oocyte is fully competent. We applied trajectory analysis (pseudotime) and a meta-analysis and uncovered the fundamental transcriptomic requirements of the oocyte at any moment of oogenesis until reaching the metaphase II stage (MII). We identified a bunch of genes showing significant variation in expression from primordial-to-antral follicle oocyte development and characterized their temporal regulation and their biological relevance. We also revealed the selective regulation of specific transcripts during the germinal vesicle-to-MII transition. Transcripts associated with energy production and mitochondrial functions were extensively downregulated, while those associated with cytoplasmic translation, histone modification, meiotic processes, and RNA processes were conserved. From the genes identified in this study, some appeared as sensitive to environmental factors such as maternal age, polycystic ovary syndrome, cryoconservation, and in vitro maturation. In the future, the atlas of transcriptomic changes described in this study will enable more precise identification of the transcripts responsible for follicular growth and oocyte maturation failures.
Topics: Female; Humans; Pregnancy; Cell Nucleus; Gene Expression Profiling; Oocytes; Oogenesis; Transcriptome
PubMed: 38203203
DOI: 10.3390/ijms25010033 -
Reproductive Sciences (Thousand Oaks,... Feb 2024Mitochondria are energy provider organelles in eukaryotic cells that contain their own specific genome. This review addresses structural and functional properties of... (Review)
Review
Mitochondria are energy provider organelles in eukaryotic cells that contain their own specific genome. This review addresses structural and functional properties of mitochondria, focusing on recent discoveries about the changes in quality and number of mitochondria per cell during oocyte development. We highlight how oocyte mitochondria exhibit stage-specific morphology and characteristics at different stages of development, in sharp contrast to the elongated mitochondria present in somatic cells. We then evaluate the latest transcriptomic data to elucidate the complex functions of mitochondria during oocyte maturation and the impact of mitochondria on oocyte development. Finally, we describe the methodological progress of mitochondrial replacement therapy to rescue oocytes with developmental disorders or mitochondrial diseases, hoping to provide a guiding reference to future clinical applications.
Topics: Oocytes; Oogenesis; Mitochondria; DNA, Mitochondrial
PubMed: 37605038
DOI: 10.1007/s43032-023-01331-8 -
Developmental Cell Nov 2023In multicellular lives, the differentiation of stem cells and progenitor cells is often accompanied by a transition from glycolysis to mitochondrial oxidative...
In multicellular lives, the differentiation of stem cells and progenitor cells is often accompanied by a transition from glycolysis to mitochondrial oxidative phosphorylation (OXPHOS). However, the underlying mechanism of this metabolic transition remains largely unknown. In this study, we investigate the role of mechanical stress in activating OXPHOS during differentiation of the female germline cyst in Drosophila. We demonstrate that the surrounding somatic cells flatten the 16-cell differentiating cyst, resulting in an increase of the membrane tension of germ cells inside the cyst. This mechanical stress is necessary to maintain cytosolic Ca concentration in germ cells through a mechanically activated channel, transmembrane channel-like. The sustained cytosolic Ca triggers a CaMKI-Fray-JNK signaling relay, leading to the transcriptional activation of OXPHOS in differentiating cysts. Our findings demonstrate a molecular link between cell mechanics and mitochondrial energy metabolism, with implications for other developmentally orchestrated metabolic transitions in mammals.
Topics: Animals; Drosophila; Germ Cells; Energy Metabolism; Cell Differentiation; Drosophila Proteins; Mammals
PubMed: 37647895
DOI: 10.1016/j.devcel.2023.08.007 -
Journal of Molecular Biology Feb 2024Autophagy is used to degrade cytoplasmic materials, and is critical to maintain cell and organismal health in diverse animals. Here we discuss the regulation,... (Review)
Review
Autophagy is used to degrade cytoplasmic materials, and is critical to maintain cell and organismal health in diverse animals. Here we discuss the regulation, utilization and impact of autophagy on development, including roles in oogenesis, spermatogenesis and embryogenesis in animals. We also describe how autophagy influences postembryonic development in the context of neuronal and cardiac development, wound healing, and tissue regeneration. We describe recent studies of selective autophagy during development, including mitochondria-selective autophagy and endoplasmic reticulum (ER)-selective autophagy. Studies of developing model systems have also been used to discover novel regulators of autophagy, and we explain how studies of autophagy in these physiologically relevant systems are advancing our understanding of this important catabolic process.
PubMed: 38311234
DOI: 10.1016/j.jmb.2024.168473