Reproductive behavior: Decrypting cryptic female choice.

Females in many species bias fertilization success and paternity after mating with multiple males. Two new studies uncover the mechanisms of this phenomenon, cryptic female choice, in Drosophila, linking it to pheromone-stimulated ejection of sperm and mating plug.

Calcium signaling in oocyte quality and functionality and its application.

Calcium (Ca2+) is a second messenger for many signal pathways, and changes in intracellular Ca2+ concentration ([Ca2+]i) are an important signaling mechanism in the oocyte maturation, activation, fertilization, function regulation of granulosa and cumulus cells and offspring development. Ca2+ oscillations occur during oocyte maturation and fertilization, which are maintained by Ca2+ stores and extracellular Ca2+ ([Ca2+]e). Abnormalities in Ca2+ signaling can affect the release of the first polar body, the first meiotic division, and chromosome and spindle morphology. Well-studied aspects of Ca2+ signaling in the oocyte are oocyte activation and fertilization. Oocyte activation, driven by sperm-specific phospholipase PLCζ, is initiated by concerted intracellular patterns of Ca2+ release, termed Ca2+ oscillations. Ca2+ oscillations persist for a long time during fertilization and are coordinately engaged by a variety of Ca2+ channels, pumps, regulatory proteins and their partners. Calcium signaling also regulates granulosa and cumulus cells' function, which further affects oocyte maturation and fertilization outcome. Clinically, there are several physical and chemical options for treating fertilization failure through oocyte activation. Additionally, various exogenous compounds or drugs can cause ovarian dysfunction and female infertility by inducing abnormal Ca2+ signaling or Ca2+ dyshomeostasis in oocytes and granulosa cells. Therefore, the reproductive health risks caused by adverse stresses should arouse our attention. This review will systematically summarize the latest research progress on the aforementioned aspects and propose further research directions on calcium signaling in female reproduction.

Assisted oocyte activation significantly improves zygote formation, cleavage, and implantation rates in patients with a history of fertilization failures.

Background: Fertilization check performed at the 18th hour following classic in vitro fertilization procedure (IVF) or intracytoplasmic sperm injection (ICSI) is a critical stage in assisted reproduction. The success of the treatment is significantly reliant on the quantity of zygotes exhibiting two pronuclei. Consequently, low fertilization rates or complete fertilization failure are highly undesirable outcomes for both patients and reproductive specialists. Applying additional calcium ionophore for oocyte activation subsequent to ICSI may offer benefits and potentially enhance treatment outcomes, particularly for patients who have experienced low or absent fertilization rates (FR) in previous treatment cycles. The aim of the study is to evaluate the efficacy of Ca2+ ionophore application for oocyte activation. Methods: A retrospective analysis of 924 oocytes obtained from 120 patients who underwent ICSI cycles with a history of low or no fertilization as a result of previous unsuccessful treatment rounds. The next ART cycle followed with additional oocyte Ca2+ ionophore activation applied in 57 of the cases in order to optimize the treatment process (Group 1), and 63 patients were included and their outcomes followed as a control group (Group 2).We conducted a comparative analysis of results in both groups. The study's primary outcomes encompassed fertilization, cleavage embryo quality, blastocyst rate, and established clinical pregnancies. Results: At day 1 fertilization check we had 274/386 zygotes (71%FR) in group 1 and 132/410 in group 2 (32.2%FR), (P < 0.0001). Twenty-two (34.9%) cycles in group 2 resulted in total fertilization failure (TFF). At the cleavage stage top-quality embryos from group 1 were significantly higher (P = 0.0021) in comparison to group 2. Forty-eight embryo transfers (ET) were performed in group 1 resulting in 41.67% clinical pregnancies versus 33 ET and only 4 pregnancies (12.12%) for group 2 (P = 0.0044). Conclusions: The results confirm the appropriateness of assisted oocyte activation as an additional method in cases of previous fertilization failure cycles.

Switching on lysosomes.

The formation of large endolysosomal structures in unfertilized eggs ensures that lysosomes remain dormant before fertilization, and then shift into clean-up mode after the egg-to-embryo transition.

Investigations into the role of platelet-activating factor in the peri-conception period of the mare.

In Brief: In many mammals, the lipid platelet-activating factor (PAF) has important functions in female reproduction and fertility. This study shows that PAF is present in the reproductive tissues of mares and is involved in processes related to ovulation and early pregnancy. Abstract: Platelet-activating factor (PAF) has been implicated in a number of reproductive processes ranging from ovulation to embryo motility but has not been widely explored in the mare. To identify the presence and examine the role of PAF in the equine periconception processes, targeted mass spectrometry coupled with chromatographic separation was performed on equine follicular fluid (FF), and PAF was quantitatively detected. Subsequently, untargeted high-resolution mass spectrometry-based lipidomic analysis was carried out to quantify PAF in different-sized pre-ovulatory follicles, whereby different molecular species of PAF, PAF (14:0) and PAF (16:1), were both seen to be increasing with follicle diameter. These findings suggest that PAF within FF is increasing as preovulatory follicles approach ovulation. Additionally, immunofluorescence staining identified the PAF receptor in the luminal pericellular, apical, and basal aspect of equine oviductal epithelial cells. Lastly, an equine oviductal epithelial organoid model was generated and showed that the addition of PAF significantly increased the ciliary beat frequency (CBF) (Hz), an action consistent with a role for PAF in embryo migration. It is proposed that the local action of PAF on the ciliated cells of the oviduct propels both the oocyte and the conceptus towards the uterus. In the mare, it appears that PAF is a contributor during the periconception period, potentially being a mediator in the mechanisms of ovulation and in the dialogue of very early pregnancy.

In Vivo Visualization of Calcium Transients during Fertilization and Early Development in C. elegans.

Calcium is an important signaling molecule during the oocyte-to-embryo transition (OET) and early embryogenesis. The hermaphroditic nematode Caenorhabditis elegans provides several unique advantages for the study of the OET as it is transparent and has an ordered gonad that produces one mature oocyte every ~23 min at 20 °C. We have modified the genetically encoded calcium indicator jGCaMP7s to fluorescently indicate the moment of fertilization within a living organism. We have termed this reporter "CaFE" for Calcium during Fertilization in C. elegans. The CaFE reporter was engineered into a safe harbor locus in single copy, has no significant impact on physiology or fecundity, and produces a robust signal upon fertilization. Here, a series of protocols is presented for utilizing the CaFE reporter as an in vivo tool for dissecting the OET and embryogenesis. We include methods to synchronize worms, examine the effects of RNAi knockdown, mount worms for imaging, and to visualize calcium in oocytes and embryos. Additionally, we present the generation of additional worm strains to aid in this type of analysis. Demonstrating the utility of the CaFE reporter to visualize the timing of fertilization, we report that double ovulation occurs when ipp-5 is targeted by RNAi and that only the first oocyte undergoes immediate fertilization. Furthermore, the discovery of single-cell calcium transients during early embryogenesis is reported here, demonstrating that the CaFE reporter persists into early development. Importantly, the CaFE reporter in worms is simple enough to use for incorporation into course-based undergraduate research (CURE) laboratory classes. The CaFE reporter, coupled with the ordered gonad and ease of RNAi in worms, facilitates inquiry into the cell-cell dynamics required to regulate internal fertilization and early embryogenesis.

Nutritional and exercise interventions to improve conception in women suffering from obesity and distinct nosological entities.

Infertility among women, particularly those living with obesity, presents a multifaceted challenge with implications for reproductive health worldwide. Lifestyle interventions, mainly focusing on weight loss, have emerged as promising strategies to improve fertility outcomes in this population. This review aims to explore the effectiveness of various lifestyle interventions, encompassing dietary modifications and exercise regimens, in enhancing fertility outcomes among women with obesity and associated conditions such as polycystic ovary syndrome, congenital adrenal hyperplasia, type 2 diabetes mellitus, premenopause, hypothyroidism and eating disorders. Methodology of study search encompass a broad spectrum, ranging from interventions targeting weight management through slow or rapid weight loss to dietary approaches emphasizing whole food groups, specific nutrients, and dietary patterns like low-carbohydrate or ketogenic diets, as well as the Mediterranean diet. By synthesizing existing findings and recommendations, this review contributes to the understanding of lifestyle interventions in addressing infertility, with an emphasis on the population of women of reproductive age with excess weight and known or unknown infertility issues, while promoting their integration into clinical practice to optimize reproductive health and overall well-being.

Anti-Mullerian Hormone Assessment in Assisted Reproductive Technique Outcome and Natural Conception.

In recent years, the prevalence of infertility has increased, and appears to affect approximately one in six couples. Some of them must perform assisted reproductive techniques (ART) in order to achieve pregnancy. As a result, growing interest has arisen about predictive factors of pregnancy and live birth with and without ART. Anti-Mullerian hormone (AMH) is a glycoprotein discovered in the 1950s in male embryonic sexual differentiation. Later, in 1984, its role in folliculogenesis was reported: secreted by granulosa cells, this hormone is involved in the regulation of the recruitment of primordial follicles and in follicular growth. AMH assays were developed for women in 1990s, and the serum AMH level has rapidly become a crucial element in managing women's fertility. Based mainly on its ability to be a quantitative but indirect marker of ovarian reserve, the serum AMH assay is widely used in reproductive medicine and ART. This review summarizes current knowledge of the AMH assessment in the field of reproductive medicine. We focus on the role of AMH level to predict spontaneous pregnancy occurrence, ART outcomes, and fertility preservation outcomes.

Melatonin improves fertilization rate in assisted reproduction: Systematic review and meta-analysis.

BACKGROUND: Melatonin is a hormone produced by the pineal gland and it has antioxidant properties. AIM: This study aimed to evaluate the effects of melatonin on assisted reproductive technologies through a systematic review and a meta-analysis. MATERIALS AND METHODS: Search strategies were used in PubMed and in other databases covering the last 15 years. After screening for eligibility, 17 articles were selected for the systematic review. For the meta-analysis statistics, two groups were formed, the treatment group (with melatonin) and the control group (without melatonin) for various assisted reproduction outcomes. RESULTS: The main results were that no statistical differences were found concerning the clinical pregnancy outcome (p = 0.64), but there was a statistical difference with respect to Mature Oocytes (MII) (p = 0.001), antral follicle count (p = 0.0002), and the fertilization rate (p ≤ 0.0001). CONCLUSIONS: Melatonin had beneficial effects such as the improvement in the fertilization rate, although the authors did not obtain significance in the clinical pregnancy rate.

Modeling Fertilization Outcome in a Changing World.

Marine organisms have complex life histories. For broadcast spawners, successful continuation of the population requires their small gametes to make contact in the water column for sufficiently long periods for fertilization to occur. Anthropogenic climate change has been shown to impact fertilization success in various marine invertebrates, including sea urchins, which are key grazers in their habitats. Gamete performance of both sexes declined when exposed to elevated temperatures and/or pCO2 levels. Examples of reduced performance included slower sperm swimming speed and thinning egg jelly coat. However, such responses to climate change stress were not uniform between individuals. Such variations could serve as the basis for selection. Fertilization kinetics have long been modeled as a particle collision process. Here, we present a modified fertilization kinetics model that incorporates individual variations in performance in a more environmentally relevant regime, and which the performance of groups with different traits can be separately tracked in a mixture. Numerical simulations highlight that fertilization outcomes are influenced by changes in gamete traits as they age in sea water and the presence of competition groups (multiple dams or sires). These results highlight the importance of considering multiple individuals and at multiple time points during in vivo assays. We also applied our model to show that interspecific variation in climate stress vulnerabilities elevates the risk of hybridization. By making a numerical model open-source, we aim to help us better understand the fate of organisms in the face of climate change by enabling the community to consider the mean and variance of the response to capture adaptive potential.

pH Homeodynamics and Male Fertility: A Coordinated Regulation of Acid-Based Balance during Sperm Journey to Fertilization.

pH homeostasis is crucial for spermatogenesis, sperm maturation, sperm physiological function, and fertilization in mammals. HCO3- and H+ are the most significant factors involved in regulating pH homeostasis in the male reproductive system. Multiple pH-regulating transporters and ion channels localize in the testis, epididymis, and spermatozoa, such as HCO3- transporters (solute carrier family 4 and solute carrier family 26 transporters), carbonic anhydrases, and H+-transport channels and enzymes (e.g., Na+-H+ exchangers, monocarboxylate transporters, H+-ATPases, and voltage-gated proton channels). Hormone-mediated signals impose an influence on the production of some HCO3- or H+ transporters, such as NBCe1, SLC4A2, MCT4, etc. Additionally, ion channels including sperm-specific cationic channels for Ca2+ (CatSper) and K+ (SLO3) are directly or indirectly regulated by pH, exerting specific actions on spermatozoa. The slightly alkaline testicular pH is conducive to spermatogenesis, whereas the epididymis's low HCO3- concentration and acidic lumen are favorable for sperm maturation and storage. Spermatozoa pH increases substantially after being fused with seminal fluid to enhance motility. In the female reproductive tract, sperm are subjected to increasing concentrations of HCO3- in the uterine and fallopian tube, causing a rise in the intracellular pH (pHi) of spermatozoa, leading to hyperpolarization of sperm plasma membranes, capacitation, hyperactivation, acrosome reaction, and ultimately fertilization. The physiological regulation initiated by SLC26A3, SLC26A8, NHA1, sNHE, and CFTR localized in sperm is proven for certain to be involved in male fertility. This review intends to present the key factors and characteristics of pHi regulation in the testes, efferent duct, epididymis, seminal fluid, and female reproductive tract, as well as the associated mechanisms during the sperm journey to fertilization, proposing insights into outstanding subjects and future research trends.

CVAE-DF: A hybrid deep learning framework for fertilization status detection of pre-incubation duck eggs based on VIS/NIR spectroscopy.

Unfertilized duck eggs not removed prior to incubation will deteriorate quickly, posing a risk of contaminating the normally fertilized duck eggs. Thus, detecting the fertilization status of breeding duck eggs as early as possible is a meaningful and challenging task. Most existing work usually focus on the characteristics of chicken eggs during mid-term hatching. However, little attention has been paid to the detection for duck eggs prior to incubation. In this paper, we present a novel hybrid deep learning detection framework for the fertilization status of pre-incubation duck eggs, termed CVAE-DF, based on visible/near-infrared (VIS/NIR) transmittance spectroscopy. The framework comprises the encoder of a convolutional variational autoencoder (CVAE) and an improved deep forest (DF) model. More specifically, we first collected transmittance spectral data (400-1000 nm) of 255 duck eggs before hatching. The multiplicative scatter correction (MSC) method was then used to eliminate noise and extraneous information of the raw spectral data. Two efficient data augmentation methods were adopted to provide sufficient data. After that, CVAE was applied to extract representative features and reduce the feature dimension for the detection task. Finally, an improved DF model was employed to build the classification model on the enhanced feature set. The CVAE-DF model achieved an overall accuracy of 95.94 % on the test dataset. These experimental results in terms of four metrics demonstrate that our CVAE-DF method outperforms the traditional methods by a significant margin. Furthermore, the results also indicate that CVAE holds great promise as a novel feature extraction method for the VIS/NIR spectral analysis of other agricultural products. It is extremely beneficial to practical engineering.

A CatSper-Uninvolved Mechanism to Induce Forward Sperm Motility in the Internal Fertilization.

Sperm-specific cation channel (CatSper), sperm-specific Na + /H + exchanger (sNHE), and soluble adenylyl cyclase (sAC) are necessary in the signaling pathways to control sperm motility in many animals, whereas some animals have lost some or all of them. In the present study, we examined CatSper-uninvolved signaling for vigorous undulation of the undulating membrane that is attached to the sperm tail and gives thrust for forward motility in the internally fertilizing newt Cynops pyrrhogaster. Reverse-transcription PCR failed to detect sNHE in the newt sperm. However, the pH of sperm cytoplasm was raised under a high extracellular pH equivalent to that of egg jelly, where sperm motility is initiated by sperm motility-initiating substance (SMIS). Carbonic anhydrase XII/ XVI and SLC4A4/8 were suggested to be present in the sperm, and transported bicarbonates raised the intracellular pH. In egg jelly extract that contained SMIS, the anion transporter inhibitor DIDS weakened the undulation of the undulating membrane, while bicarbonates enhanced it. The cyclic AMP concentration was found to increase in sperm cytoplasm in the egg-jelly extract. An inhibitor of sAC (KH7) weakened the undulation of the undulating membrane, and dibutyryl cyclic AMP blocked the inhibitory effect. Inhibitor of transmembrane AC (DDA) limitedly affected the undulation. The undulation was weakened by an inhibitor of protein kinase A (H89), and by an inhibitor of transient receptor potential (TRP) channels (RN1747). Our results support the conclusions that the high pH of the egg jelly triggers a signaling pathway through sAC, PKA, and TRP channels, and coacts with SMIS to induce forward sperm motility.

Don't wait any longer, conceive in time: a systematic review and meta-analysis based on semen parameters after varicocelectomy.

BACKGROUND: Varicocelectomy was considered to be beneficial to patients with varicocele-related infertility. However, there are only a few researchers who have explored the relationship between better timing and postoperative semen improvement in patients. METHODS: We conducted this meta-analysis by enrolling published prospective studies to find out the best waiting time after varicocelectomy to wait for better improvement of semen quality. An extensive search was conducted in PubMed, Web of Science, and Cochrane Library to identify eligible studies. The included studies were then analyzed comprehensively using STATA software and standardized mean differences (SMDs) and their corresponding 95% confidence intervals were calculated. RESULTS: Our comprehensive analysis showed that after varicocelectomy, follow-up results within 3 months or longer showed a significant improvement in semen parameters compared to the preoperative period. Notably, no further improvement in semen parameters was observed when the follow-up period reached six months or longer (semen volume: WMD: - 0.07 (- 0.29, 0.16); sperm concentration: WMD: - 1.33 (- 2.33, - 4.99); sperm motility: WMD: 2.31 (- 0.55, 5.18); sperm morphology: WMD: 1.29 (- 0.66, 3.24); sperm total motile count: WMD: 3.95 (- 6.28, 14.19)). CONCLUSIONS: Three months after varicocelectomy may be the optimal time for semen parameters compared to six months or even longer, which means it is also the preferable time for conception. However, more well-designed prospective studies are needed in the future to validate our conclusion.

Determinants of Conception and Adverse Pregnancy Outcomes in Women with Endometriosis: A Longitudinal Study.

Endometriosis, affecting approximately 10% of reproductive-aged women globally, poses significant challenges, including chronic pelvic pain, dysmenorrhea, and infertility. In low- and middle-income countries like India, accessibility to affordable infertility care remains a concern. This multicenter prospective cohort study, conducted across six tertiary care hospitals in India from 2017 to 2022, aims to explore the natural progression of conception and pregnancy outcomes in women with endometriosis. Of the 257 participants, 19.1% conceived during the study, revealing significant geographic and income-based variations (p < 0.001, p = 0.01). Dysmenorrhea (p < 0.001) and dyspareunia (p=0.027) were correlated with conception, while no such associations were found with chronic pelvic pain or menstrual factors. Lesion type, number, and severity showed no conclusive link with conception. Natural conception occurred in 70% of cases, with an average post-surgery conception time of 282.1 days. Live birth rate was 85.7%, while complications included placenta previa (16.4%), preeclampsia (4.1%), and preterm births (4.1%). This study, one of the first in India on endometriosis-related fertility progression, emphasizes the need for comprehensive understanding and management of conception and pregnancy outcomes. Considering India's substantial endometriosis burden, the study recommends prioritizing larger multicenter investigations for a better understanding and effective strategies for infertility management.

Microfluidic sperm sorting selects a subpopulation of high-quality sperm with a higher potential for fertilization.

STUDY QUESTION: Is a microfluidic sperm sorter (MSS) able to select higher quality sperm compared to conventional methods? SUMMARY ANSWER: The MSS selects sperm with improved parameters, lower DNA fragmentation, and higher fertilizing potential. WHAT IS KNOWN ALREADY: To date, the few studies that have compared microfluidics sperm selection with conventional methods have used heterogeneous study population and have lacked molecular investigations. STUDY DESIGN, SIZE, DURATION: The efficiency of a newly designed MSS in isolating high-quality sperm was compared to the density-gradient centrifugation (DGC) and swim-up (SU) methods, using 100 semen samples in two groups, during 2023-2024. PARTICIPANTS/MATERIALS, SETTING, METHODS: Semen specimens from 50 normozoospermic and 50 non-normozoospermic men were sorted using MSS, DGC, and SU methods to compare parameters related to the quality and fertilizing potential of sperm. The fertilizing potential of sperm was determined by measurement of phospholipase C zeta (PLCζ) and post-acrosomal sheath WW domain-binding protein (PAWP) expression using flow cytometry, and the chromatin dispersion test was used to assess sperm DNA damage. MAIN RESULTS AND THE ROLE OF CHANCE: In both normozoospermic and non-normozoospermic groups, the MSS-selected sperm with the highest progressive motility, PLCζ positive expression and PLCζ and PAWP fluorescence intensity the lowest non-progressive motility, and minimal DNA fragmentation, compared to sperm selected by DGC and SU methods (P < 0.05). LIMITATION, REASONS FOR CAUTION: The major limitations of our study were the low yield of sperm in the MSS chips and intentional exclusion of severe male factor infertility to yield a sufficient sperm count for molecular experiments; thus testing with severe oligozoospermic semen and samples with low count and motility is still required. In addition, due to ethical considerations, at present, it was impossible to use the sperm achieved from MSS in the clinic to assess the fertilization rate and further outcomes. WIDER IMPLICATIONS OF THE FINDINGS: Our research presents new evidence that microfluidic sperm sorting may result in the selection of high-quality sperm from raw semen. This novel technology might be a key to improving clinical outcomes of assisted reproduction in infertile patients. STUDY FUNDING/COMPETING INTEREST(S): The study is funded by the Iran University of Medical Sciences and no competing interest exists. TRIAL REGISTRATION NUMBER: N/A.

MARC-3, a membrane-associated ubiquitin ligase, is required for fast polyspermy block in Caenorhabditis elegans.

In many sexually reproducing organisms, oocytes are fundamentally fertilized with one sperm. In Caenorhabditis elegans, chitin layer formation after fertilization by the EGG complex is one of the mechanisms of polyspermy block, but other mechanisms remain unknown. Here, we demonstrate that MARC-3, a membrane-associated RING-CH-type ubiquitin ligase that localizes to the plasma membrane and cortical puncta in oocytes, is involved in fast polyspermy block. During polyspermy, the second sperm entry occurs within approximately 10 s after fertilization in MARC-3-deficient zygotes, whereas it occurs approximately 200 s after fertilization in egg-3 mutant zygotes defective in the chitin layer formation. MARC-3 also functions in the selective degradation of maternal plasma membrane proteins and the transient accumulation of endosomal lysine 63-linked polyubiquitin after fertilization. The RING-finger domain of MARC-3 is required for its in vitro ubiquitination activity and polyspermy block, suggesting that a ubiquitination-mediated mechanism sequentially regulates fast polyspermy block and maternal membrane protein degradation during the oocyte-to-embryo transition.