Rethinking the application of nanoparticles in women's reproductive health and assisted reproduction

Nanoparticles and nanotechnology may present opportunities to revolutionize the prevention, treatment and diagnosis of a range of reproductive health conditions in women. These technologies are also used to improve outcomes of assisted reproductive technology. We highlight a range of these potential clinical uses of nanoparticles for polycystic ovary syndrome, endometriosis, uterine fibroids and sexually transmitted infections, considering in vitro and in vivo studies along with clinical trials. In addition, we discuss applications of nanoparticles in assisted reproductive technology, including sperm loading, gamete and embryo preservation and preventing preterm birth. Finally, we present some of the concerns associated with the medical use of nanoparticles, identifying routes for further exploration before nanoparticles can be applied to women's reproductive health in the clinic.

Determining the optimal time interval between sample acquisition and cryopreservation when processing immature testicular tissue to preserve fertility

The cryopreservation of immature testicular tissue (ITT) prior to gonadotoxic therapy is crucial for fertility preservation in prepubertal boys with cancer. However, the optimal holding time between tissue collection and cryopreservation has yet to be elucidated. Using the bovine model, we investigated four holding times (1, 6, 24, and 48 h) for ITTs before cryopreservation. Biopsies from two-week-old calves were stored in transport medium and cryopreserved following a standard slow-freezing clinical protocol. Thawed samples were then assessed for viability, morphology, and gene expression by haematoxylin and eosin (H&E) staining, immunohistochemistry and real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR). Analysis failed to identify any significant changes in cell viability when compared between the different groups. Sertoli (Vimentin+) and proliferating cells (Ki67+) were well-preserved. The expression of genes related to germ cells, spermatogenesis (STRA8, PLZF, GFRα-1, C-KIT, THY1, UCHL-1, NANOG, OCT-4, CREM), and apoptosis (HSP70-2) remained stable over 48 h. However, seminiferous cord detachment increased significantly in the 48-h group (p < 0.05), with associated cord and SSC shrinkage. Collectively, our analyses indicate that bovine ITTs can be stored for up to 48 h prior to cryopreservation with no impact on cell viability and the expression levels of key genes. However, to preserve the morphology of frozen-thawed tissue, the ideal processing time would be within 24 h. Testicular tissues obtained from patients for fertility preservation often need to be transported over long distances to be cryopreserved in specialist centres. Our findings highlight the importance of determining optimal tissue transport times to ensure tissue quality in cryopreservation.

Anin vitrothree-dimensional (3D) testicular organoid culture system for efficient gonocyte maintenance and propagation using frozen/thawed neonatal bovine testicular tissues

Fertility preservation in prepubertal boys with cancer requires the cryopreservation of immature testicular tissues (ITTs) prior to gonadotoxic treatment. However, the limited number of germ cells in small human ITT biopsies necessitates the development of anin vitroculture system for germ cell expansion using frozen-thawed ITTs. Here, we generated testicular organoids for thein vitromaintenance and expansion of gonocytes from frozen-thawed two-week-old neonatal bovine ITTs. We investigated the effects of different cell-seeding densities, culture serums, seeding methods, and gonadotropin supplementations, on the maintenance and proliferation of enriched gonocytes. Our results demonstrated that enriched gonocytes and testicular cells from frozen-thawed neonatal ITTs could self-assemble into spheroid organoids in three days in an appropriate Matrigel-based culture environment. For the optimal formation of prepubertal testicular organoids, a seeding density of 1 × 106cells/well is recommended over other densities. This strategy results in organoids with a mean diameter of 60.53 ± 12.12 μm; the mean number of organoids was 5.57 ± 1.60/105μm2on day 11. The viability of organoids was maintained at 79.75 ± 2.99% after being frozen and thawed. Supplementing the culture medium with glial cell-derived neurotrophic factor, fibroblast growth factor 2, and leukemia inhibitory factor, increased the proportion of KI67-positive proliferating cells in organoids, elevated the expression ofC-KITbut reduced the expression ofGFRα1at day 28 when compared to those without hormone supplements(p< 0.05). In addition, supplementing the culture medium with follicle-stimulating hormone and testosterone helped to maintain a significantly higher viability (p< 0.05) in ITT organoids at day 28. These organoids could be cryopreserved for storage and thawed as needed. The successful generation of ITT organoids provides a valuable tool for establishingin vitrospermatogenesis, propagating human germ cells, investigating testicular physiology and the origin of germ cell tumors, and testing the toxicity of new drugs in future clinical applications.

Dissociation, enrichment, and the in vitro formation of gonocyte colonies from cryopreserved neonatal bovine testicular tissues

Gonocytes play an important role in early development of spermatogonial stem cells and fertility preservation to acquire more high quality gonocytes in vitro for further germ cell-related research and applications, it is necessarily needed to enrich and in vitro propagate gonocytes from cryopreserved bovine testicular tissues. This study aimed to investigate the isolation, enrichment, and colony formation of gonocytes in vitro for germ cell expansion from cryopreserved neonatal bovine testicular tissues. The effects of several different in vitro culture conditions, including seeding density, temperature, serum replacement and extracellular matrices were investigated for the maintenance, proliferation and formation of gonocyte colonies in vitro. Frozen/thawed two-week-old neonatal bovine testicular tissues were digested and gonocytes were enriched using a Percoll density gradient. Cell viability was accessed by trypan blue staining and cell apoptosis was evaluated by TUNEL assays. Gonocytes were identified and confirmed by immunofluorescence with the PGP9.5 germ cell marker and the OCT4 pluripotency marker while Sertoli cells were stained with vimentin. We found that neonatal bovine gonocytes were efficiently enriched by a 30%-40% Percoll density gradient (p < 0.05). No significant differences were detected between neonatal bovine testicular cells cultured at 34 °C or 37 °C. The formation of gonocyte colonies was observed in culture medium supplemented with knockout serum replacement (KSR), but not fetal bovine serum (FBS), at a seeding density higher than 5.0 × 104 cells/well. A greater number of gonocyte colonies were observed in culture plates coated with laminin (38.00 ± 6.24/well) and Matrigel (38.67 ± 3.78/well) when compared to plates coated with collagen IV and fibronectin (p < 0.05). In conclusion, bovine neonatal gonocytes were able to be efficiently isolated, enriched and maintained in gonocyte colonies in vitro; the development of this protocol provides vital information for the clinical translation of this technology and the future restoration of human fertility.

Contribution of semen to early embryo development: fertilization and beyond

BACKGROUND

It has long been thought that the factors affecting embryo and foetal development were exclusively maternally derived; hence, if issues regarding fertility and embryo development were to arise, the blame has traditionally been placed solely on the mother. An escalating interest in how paternal factors influence embryo development, however, has begun to prove otherwise. Evidence suggests that both seminal plasma (SP) and sperm contribute multiple factors that shape embryogenesis. This review thus focuses on the role that semen has in driving early embryonic development, and describes how paternal factors, such as SP, sperm centriole, sperm proteins, sperm RNA, sperm DNA, and its integrity, together with epigenetics, may influence the female reproductive tract and post-fertilization events. The important contributions of paternal factors to embryo development highlight the imperative need for further research in this area, which is sure to bring forth breakthroughs leading to improvements in infertility diagnosis and ART as well as reducing the risk of miscarriage.

OBJECTIVE AND RATIONALE

This review provides a comprehensive overview of the role of human semen in development of the early embryo, with the aim of providing a better understanding of the influence of SP and sperm on early embryonic divisions, gene and protein expression, miscarriage, and congenital diseases.

SEARCH METHODS

PubMed searches were performed using the terms 'sperm structure', 'capacitation', 'acrosome reaction', 'fertilization', 'oocyte activation', 'PLCζ', 'PAWP', 'sperm-borne oocyte activation factor', 'oocyte activation deficiency', 'sperm centriole', 'sperm transport', 'sperm mitochondria', 'seminal plasma', 'sperm epigenetics', 'sperm histone modifications', 'sperm DNA methylation', 'sperm-derived transcripts', 'sperm-derived proteins', 'sperm DNA fragmentation', 'sperm mRNA', 'sperm miRNAs', 'sperm piRNAs', and 'sperm-derived aneuploidy'. The reviewed articles were restricted to those published in English between 1980 and 2022.

OUTCOMES

The data suggest that male-derived factors contribute much more than just the male haploid genome to the early embryo. Evidence indicates that semen contributes multiple factors that help shape the fate of embryogenesis. These male-derived factors include contributions from SP, the paternal centriole, RNA and proteins, and DNA integrity. In addition, epigenetic changes have an impact on the female reproductive tract, fertilization, and early stages of embryo development. For example, recent proteomic and transcriptomic studies have identified several sperm-borne markers that play important roles in oocyte fertilization and embryogenesis.

WIDER IMPLICATIONS

This review highlights that several male-derived factors are required to work in tandem with female counterparts to allow for correct fertilization and development of the early embryo. A deeper understanding of the contributions of paternal factors that are shuttled over from the sperm cell to the embryo can shed light on how to improve ART from an andrological perspective. Further studies may aid in preventing the passing on of genetic and epigenetic abnormalities of paternal origin, thus decreasing the incidence of male factor infertility. In addition, understanding the exact mechanisms of paternal contribution may assist reproductive scientists and IVF clinicians in determining new causes of recurrent early miscarriage or fertilization failure.

Protocol for developing a core outcome set for male infertility research: an international consensus development study

STUDY QUESTION

We aim to develop, disseminate and implement a minimum data set, known as a core outcome set, for future male infertility research.

WHAT IS KNOWN ALREADY

Research into male infertility can be challenging to design, conduct and report. Evidence from randomized trials can be difficult to interpret and of limited ability to inform clinical practice for numerous reasons. These may include complex issues, such as variation in outcome measures and outcome reporting bias, as well as failure to consider the perspectives of men and their partners with lived experience of fertility problems. Previously, the Core Outcome Measure for Infertility Trials (COMMIT) initiative, an international consortium of researchers, healthcare professionals and people with fertility problems, has developed a core outcome set for general infertility research. Now, a bespoke core outcome set for male infertility is required to address the unique challenges pertinent to male infertility research.

STUDY DESIGN SIZE DURATION

Stakeholders, including healthcare professionals, allied healthcare professionals, scientists, researchers and people with fertility problems, will be invited to participate. Formal consensus science methods will be used, including the modified Delphi method, modified Nominal Group Technique and the National Institutes of Health's consensus development conference.

PARTICIPANTS/MATERIALS SETTING METHODS

An international steering group, including the relevant stakeholders outlined above, has been established to guide the development of this core outcome set. Possible core outcomes will be identified by undertaking a systematic review of randomized controlled trials evaluating potential treatments for male factor infertility. These outcomes will be entered into a modified Delphi method. Repeated reflection and re-scoring should promote convergence towards consensus outcomes, which will be prioritized during a consensus development meeting to identify a final core outcome set. We will establish standardized definitions and recommend high-quality measurement instruments for individual core outcomes.

STUDY FUNDING/COMPETING INTERESTS

This work has been supported by the Urology Foundation small project award, 2021. C.L.R.B. is the recipient of a BMGF grant and received consultancy fees from Exscentia and Exceed sperm testing, paid to the University of Dundee and speaking fees or honoraria paid personally by Ferring, Copper Surgical and RBMO. S.B. received royalties from Cambridge University Press, Speaker honoraria for Obstetrical and Gynaecological Society of Singapore, Merk SMART Masterclass and Merk FERRING Forum, paid to the University of Aberdeen. Payment for leadership roles within NHS Grampian, previously paid to self, now paid to University of Aberdeen. An Honorarium is received as Editor in Chief of Human Reproduction Open. M.L.E. is an advisor to the companies Hannah and Ro. B.W.M. received an investigator grant from the NHMRC, No: GNT1176437 is a paid consultant for ObsEva and has received research funding from Ferring and Merck. R.R.H. received royalties from Elsevier for a book, consultancy fees from Glyciome, and presentation fees from GryNumber Health and Aytu Bioscience. Aytu Bioscience also funded MiOXYS systems and sensors. Attendance at Fertility 2020 and Roadshow South Africa by Ralf Henkel was funded by LogixX Pharma Ltd. R.R.H. is also Editor in Chief of Andrologia and has been an employee of LogixX Pharma Ltd. since 2020. M.S.K. is an associate editor with Human Reproduction Open. K.Mc.E. received an honoraria for lectures from Bayer and Pharmasure in 2019 and payment for an ESHRE grant review in 2019. His attendance at ESHRE 2019 and AUA 2019 was sponsored by Pharmasure and Bayer, respectively. The remaining authors declare no competing interests.

TRIAL REGISTRATION NUMBER

Core Outcome Measures in Effectiveness Trials (COMET) initiative registration No: 1586. Available at www.comet-initiative.org/Studies/Details/1586.

TRIAL REGISTRATION DATE

N/A.

DATE OF FIRST PATIENT’S ENROLMENT

N/A.

Phospholipase C zeta (PLCζ) and the clinical diagnosis of oocyte activation deficiency

Oocyte activation deficiency (OAD) remains the predominant cause of total/low fertilization rate in assisted reproductive technology. Phospholipase C zeta (PLCZ1) is the dominant sperm-specific factor responsible for triggering oocyte activation in mammals. OAD has been linked to numerous PLCZ1 abnormalities in patients experiencing failed in vitro fertilization or intracytoplasmic sperm injection cycles. While significant efforts have enhanced our understanding of the clinical relevance of PLCZ1, and the potential effects of genetic variants upon functionality, our ability to apply PLCZ1 in a diagnostic or therapeutic role remains limited. Artificial oocyte activation is the only option for patients experiencing OAD but lacks a reliable diagnostic approach. Immunofluorescence analysis has revealed that the levels and localization patterns of PLCZ1 within sperm can help us to indirectly diagnose a patient’s ability to induce oocyte activation. Screening of the gene encoding PLCZ1 protein is also critical if we are to fully determine the extent to which genetic factors might play a role in the aberrant expression and/or localization patterns observed in infertile patients. Collectively, these findings highlight the clinical potential of PLCZ1, both as a prognostic indicator of OAD and eventually as a therapeutic agent. In this review, we focus on our understanding of the association between OAD and PLCZ1 by discussing the localization and expression of this key protein in human sperm, the potential genetic causes of OAD, and the diagnostic tools that are currently available to us to identify PLCZ1 deficiency and select patients that would benefit from targeted therapy.

ASPP2 maintains the integrity of mechanically stressed pseudostratified epithelia during morphogenesis

During development, pseudostratified epithelia undergo large scale morphogenetic events associated with increased mechanical stress. Using a variety of genetic and imaging approaches, we uncover that in the mouse E6.5 epiblast, where apical tension is highest, ASPP2 safeguards tissue integrity. It achieves this by preventing the most apical daughter cells from delaminating apically following division events. In this context, ASPP2 maintains the integrity and organisation of the filamentous actin cytoskeleton at apical junctions. ASPP2 is also essential during gastrulation in the primitive streak, in somites and in the head fold region, suggesting that it is required across a wide range of pseudostratified epithelia during morphogenetic events that are accompanied by intense tissue remodelling. Finally, our study also suggests that the interaction between ASPP2 and PP1 is essential to the tumour suppressor function of ASPP2, which may be particularly relevant in the context of tissues that are subject to increased mechanical stress.

The early embryo maintains its structure in the face of large mechanical stresses during morphogenesis. Here they show that ASPP2 acts to preserve epithelial integrity in regions of high apical tension during early development.

An investigation of mechanisms underlying mouse blastocyst hatching: a ribonucleic acid sequencing study

OBJECTIVE

To investigate the regulatory mechanisms and signaling molecules underlying hatching in mouse embryos.

DESIGN

Experimental laboratory study using a mouse embryo model.

SETTING

University-based basic scientific research laboratory.

ANIMALS

A total of 40 B6C3F1 × B6D2F1 mouse embryos were used in this study.

INTERVENTION(S)

Frozen/thawed mouse embryos, at the 8-cell stage, were cultured in vitro for 2 days. The resulting hatching and prehatching blastocysts were then used for complementary deoxyribonucleic acid (cDNA) library preparation and ribonucleic acid (RNA) sequencing analysis (n = 8 for each group). Differentially expressed genes were then used for downstream functional analysis. In addition, a list of genes related to developmental progression in humans was used to identify genes that were potentially related to the hatching of human embryos.

MAIN OUTCOME MEASURE(S)

Differentially expressed genes, enriched Gene Ontology terms and canonical pathways, clustered gene networks, activated upstream regulators, and common genes between a gene list of hatching-related genes in mice and a gene list associated with developmental progression in humans.

RESULT(S)

A total 275 differentially expressed genes were identified between hatching and prehatching blastocysts: 230 up-regulated and 45 down-regulated genes. Functional enrichment analysis suggested that blastocyst hatching in vitro is an adenosine triphosphate (ATP)-dependent process that involves protein biosynthesis and organization of the cytoskeleton. Furthermore, by regulating cell motility, the RhoA signaling pathway (including Arpc2, Cfl1, Gsn, Pfn1, Tpi1, Grb2, Tmsb10, Enah, and Rnd3 genes) may be a crucial signaling pathway during hatching. We also identified a cluster of genes (Krt8, Krt7, Cldn4, and Aqp3) that exerted functional roles in cell-cell junctions and water homeostasis during hatching. Moreover, some growth factors (angiotensinogen and fibroblast growth factor 2) and endocrine factors (estrogen receptor and prolactin) were predicted to be involved in the regulation of embryo hatching. In addition, we identified 81 potential genes that are potentially involved in the hatching process in human embryos.

CONCLUSION(S)

Our analysis identified potential genes and molecular regulatory pathways involved in the blastocyst hatching process in mice; we also identified genes that may potentially regulate hatching in human embryos. Our findings enhance our knowledge of embryo development and provide useful information for further exploring the mechanisms underlying embryo hatching.

OUP accepted manuscript

BACKGROUND

Oocyte activation deficiency (OAD) is attributed to the majority of cases underlying failure of ICSI cycles, the standard treatment for male factor infertility. Oocyte activation encompasses a series of concerted events, triggered by sperm-specific phospholipase C zeta (PLCζ), which elicits increases in free cytoplasmic calcium (Ca²⁺) in spatially and temporally specific oscillations. Defects in this specific pattern of Ca²⁺ release are directly attributable to most cases of OAD. Ca²⁺ release can be clinically mediated via assisted oocyte activation (AOA), a combination of mechanical, electrical and/or chemical stimuli which artificially promote an increase in the levels of intra-cytoplasmic Ca²⁺. However, concerns regarding safety and efficacy underlie potential risks that must be addressed before such methods can be safely widely used.

OBJECTIVE AND RATIONALE

Recent advances in current AOA techniques warrant a review of the safety and efficacy of these practices, to determine the extent to which AOA may be implemented in the clinic. Importantly, the primary challenges to obtaining data on the safety and efficacy of AOA must be determined. Such questions require urgent attention before widespread clinical utilization of such protocols can be advocated.

SEARCH METHODS

A literature review was performed using databases including PubMed, Web of Science, Medline, etc. using AOA, OAD, calcium ionophores, ICSI, PLCζ, oocyte activation, failed fertilization and fertilization failure as keywords. Relevant articles published until June 2019 were analysed and included in the review, with an emphasis on studies assessing large-scale efficacy and safety.

OUTCOMES

Contradictory studies on the safety and efficacy of AOA do not yet allow for the establishment of AOA as standard practice in the clinic. Heterogeneity in study methodology, inconsistent sample inclusion criteria, non-standardized outcome assessments, restricted sample size and animal model limitations render AOA strictly experimental. The main scientific concern impeding AOA utilization in the clinic is the non-physiological method of Ca²⁺ release mediated by most AOA agents, coupled with a lack of holistic understanding regarding the physiological mechanism(s) underlying Ca²⁺ release at oocyte activation.

LIMITATIONS, REASONS FOR CAUTION

The number of studies with clinical relevance using AOA remains significantly low. A much wider range of studies examining outcomes using multiple AOA agents are required.

WIDER IMPLICATIONS

In addition to addressing the five main challenges of studies assessing AOA safety and efficacy, more standardized, large-scale, multi-centre studies of AOA, as well as long-term follow-up studies of children born from AOA, would provide evidence for establishing AOA as a treatment for infertility. The delivery of an activating agent that can more accurately recapitulate physiological fertilization, such as recombinant PLCζ, is a promising prospect for the future of AOA. Further to PLCζ, many other avenues of physiological oocyte activation also require urgent investigation to assess other potential physiological avenues of AOA.

STUDY FUNDING/COMPETING INTERESTS

D.G. was supported by Stanford University’s Bing Overseas Study Program. J.K. was supported by a Healthcare Research Fellowship Award (HF-14-16) made by Health and Care Research Wales (HCRW), alongside a National Science, Technology, and Innovation plan (NSTIP) project grant (15-MED4186-20) awarded by the King Abdulaziz City for Science and Technology (KACST). The authors have no competing interests to declare.

Dynamic shapes of the zygote and two-cell mouse and human

Mouse zygote morphokinetics were measured during interphase, the mitotic period, cytokinesis, and two-cell stage. Sequences of rounder-distorted-rounder shapes were revealed, as were changing patterns of cross section area. A calcium chelator and an actin-disrupting agent inhibited the area changes that occurred between pronuclear envelope breakdown and cytokinesis. During cell division, two vortices developed in each nascent cell and they rotated in opposite directions at each end of the cell, a pattern that sometimes persisted for up to 10 h. Exchange with the environment may have been promoted by these shape and area cycles and persisting circulation in the cytoplasm may have a similar function between a cell's interior and periphery. Some of these movements were sporadically also seen in human zygotes with abnormal numbers of pronuclei and the two-cell stages that developed from these compromised human zygotes.

Antigen unmasking does not improve the visualization of phospholipase C zeta in human spermatozoa

Phospholipase C zeta (PLCζ) is a sperm-specific protein that triggers oocyte activation. The analysis of PLCζ expression in human spermatozoa can be used as a diagnostic marker for oocyte activation deficiency. Our laboratory has previously optimized a standard “in-house” assay to determine PLCζ expression in human spermatozoa. However, one study has suggested that an antigen unmasking method (AUM) would be more efficient in visualizing PLCζ in human sperm. This study aimed to compare our established assay and AUM (involving HCl, acidic Tyrode's solution [AT], and heat). The mean relative fluorescence (RF) intensity of PLCζ in frozen-thawed spermatozoa from fourteen fertile donors stained with the in-house method was significantly higher than three other AUM groups (in-house [mean ± standard error of mean]: 18.87 ± 2.39 arbitrary units [a.u.] vs non-AUM: 11.44 ± 1.61 a.u., AT-AUM: 12.38 ± 1.89 a.u., and HCl-AUM: 12.51 ± 2.16 a.u., P < 0.05, one-way analysis of variance). The mean RF intensity of PLCζ in AT- and HCl-treated spermatozoa from 12 infertile males was not significantly different from that of the non-AUM group. However, the in-house method resulted in the highest RF intensity (12.11 ± 1.36 a.u., P < 0.01). Furthermore, specificity testing of antibody-antigen binding indicated that the in-house method showed more specific binding than spermatozoa treated by the AUM. In conclusion, our in-house method showed superior visualization and reliability than the AUM, thus supporting the continued use of our in-house assay for clinical research screening.

An investigation of the effects of laser-assisted zona pellucida drilling on the preimplantation mouse embryo and the competency of embryo implantation

OBJECTIVE

To investigate the impact of laser-assisted zona pellucida (ZP) drilling on the mouse embryo, with particular emphasis on molecular mechanisms, and the efficiency of embryo attachment capability using an in vitro model of implantation.

DESIGN

Experimental study.

SETTING

Academic research laboratory.

ANIMAL(S)

C57BL/6JOlaHsd mouse embryos and B6C3F1 × B6D2F1 mouse embryos.

INTERVENTION(S)

Eight-cell stage mouse embryos were randomly assigned to a laser-assisted ZP drilling group (n = 343), ZP partial drilling group (n = 312), ZP quarter thinning group (n = 289), and control group (n = 353). Embryos were cultured in vitro from E2.5 to E4.5 for 48 hours. To investigate the capacity to implant, E4.5 embryos (laser-assisted drilling group [n = 46], ZP partial drilling group [n = 28], ZP quarter thinning group [n = 26], and control group [n = 36]) were then transferred onto an attachment model on the basis of Ishikawa cells and cultured for another 72 hours.

MAIN OUTCOME MEASURE(S)

Blastocyst formation, hatching status, and hatching morphology at E4.5. Blastocyst cell components, the extent of apoptosis in embryonic cells (DNA fragmentation, caspase-3 activation, and expression of apoptosis-related genes), the expression of heat shock protein 70, and differentially expressed genes (DEGs) generated by RNA sequencing. Fully hatched embryo rate and stable attachment rate in the in vitro attachment model.

RESULT(S)

There were no significant differences between the laser-assisted ZP manipulation groups and control group with respect to the formation of blastocysts, cell number, embryonic cell apoptosis, and cellular stress. All 3 of the laser-assisted ZP manipulations significantly increased the hatching rate at E4.5 compared with the control group, especially the ZP drilling group. However, only the ZP drilling group was associated with a significantly higher proportion of "8"-shaped hatching blastocysts. Furthermore, RNA sequencing identified 48 DEGs between blastocysts from the laser-assisted drilling group and control group; the metabolic pathways were significantly enriched in these DEGs. In addition, there were no significant differences between the laser-assisted ZP manipulation groups and control group with respect to the rate of stable attachment at E7.5, although a significantly higher entrapment rate was observed in the ZP drilling group.

CONCLUSION(S)

Laser-assisted ZP manipulations did not induce cellular apoptosis or stress in mouse blastocysts. Nevertheless, for the first time, we found that laser-assisted ZP drilling could alter the embryonic transcriptome and may affect metabolic activity. Furthermore, although laser-assisted ZP manipulations can enhance the initiation of hatching, it is evident that ZP drilling comes with a potential risk of embryo entrapment.

P–182 The mechanism of mouse embryo hatching and the impact of laser drilling the zona pellucida: an RNA sequencing study

Study question

What is the mechanism of embryo hatching? Will laser-assisted zona pellucida (ZP) drilling alter the embryonic transcriptome?

Summary answer

Hatching is an ATP-dependent process. Hatching is also associated with Rho-mediated signaling. Laser-assisted ZP drilling might cause alternation in embryo metabolism.

What is known already

Embryo hatching is a vital process for early embryo development and implantation. Animal data suggests that hatching is the result of multiple factors, such as mechanical pressure, protease activation, and the regulation of maternal secretions. However, little is known about the regulatory signaling mechanisms and the molecules involved. In addition, despite the extensive use of laser-assisted ZP drilling in the clinic, the safety profile of this technique at molecular level is very sparse. The impact of this technique on the embryonic transcriptome has not been studied systematically.

Study design, size, duration

Eighty mouse embryos were randomly divided into a laser ZP drilling group (n = 40) and an untreated group (n = 40). After treatment, embryos were cultured in vitro for two days. Then, hatching blastocyst (n = 8) and pre-hatching blastocyst (n = 8) from the untreated group, and the hatching blastocyst from the treatment group (n = 8) were processed for RNA sequencing (RNA-seq).

Participants/materials, setting, methods

Cryopreserved 8-cell stage mouse embryos (B6C3F1 × B6D2F1) were thawed, and a laser was used to drill the embryo ZP in the treatment group. Next, the treated and untreated embryos were individually cultured in vitro to the E4.5 blastocyst stage. The resulting blastocysts were lysed individually and used for subsequent cDNA library preparation and RNA-seq. Following data quality control and alignment, the RNA-seq data were processed for differentially expressed gene analysis and downstream functional analysis.

Main results and the role of chance

According to the RNA-seq data, 275 differentially expressed genes (DEGs) (230 up-regulated and 45 down-regulated, adjusted P &lt; 0.05) were identified when comparing hatching and pre-hatching blastocysts in the control groups. Analysis suggested that the trophectoderm is the primary cell type involved in hatching, and revealed the potential molecules causing increased blastocyst hydrostatic pressure (Aqp3 and Cldn4). Functional enrichment analysis suggested that ATP metabolism and protein synthesis were activated in hatching blastocysts. DEGs were found to be significantly enriched in several gene ontology terms, particularly in terms of the organization of the cytoskeleton and actin polymerisation (P &lt; 0.0001). Furthermore, according to QIAGEN ingenuity pathway analysis results, Rho signaling was implicated in blastocyst hatching (Actb, Arpc2, Cfl1, Myl6, Pfn1, Rnd3, Septin9, z-score=2.65, P &lt; 0.0001). Moreover, the potential role of hormones (estrogen (z-score=2.24) and prolactin (z-score=2.4)) and growth factors (AGT (z-score=2.41) and FGF2 (z-score=2.213)) were implicated in the hatching process as indicated by the upstream regulator analysis. By comparing the transcriptome between laser-treated and untreated hatching blastocysts, 47 DEGs were identified (adjusted P &lt; 0.05) following laser-assisted ZP drilling. These genes were enriched in metabolism-related pathways (P &lt; 0.05), including the lipid metabolism pathway (Mvd, Mvk, Aacs, Gsk3a, Pik3c2a, Aldh9a1) and the xenobiotic metabolism pathway (Aldh18a1, Aldh9a1, Keap1, and Pik3c2a).

Limitations, reasons for caution

Findings in mouse embryos may not be fully representative of human embryos. Furthermore, the mechanism of hatching revealed here might only reflect the hatching process of embryos in vitro. Further studies are now necessary to confirm these findings in different conditions and species to determine their clinical significance. Wider implications of the findings: Our study profiled the mouse embryo transcriptome during in vitro hatching, identified potential key genes and mechanisms for future study. In addition, for the first time, we revealed the impact of laser-assisted ZP drilling on the transcriptome, this may help us to assess and improve the existing technique.

Trial registration number

Not applicable

P-798 Fertility preservation in pre-pubertal boys with cancer: A three-dimensional prepubertal testicular organoid for in vitro spermatogonial stem cell propagation and spermatogenesis

Study question

Can a three-dimensional (3D) prepubertal testicular organoid be formed and provide an in vitro microenvironment for spermatogonial stem cells (SSCs) maintenance and future spermatogenesis?

Summary answer

Primary cells extracted from immature testicular tissue (ITT) or SSCs can be grown long-term as 3D organoids, providing the potential for in vitro study.

What is known already

Aggressive cancer treatments, such as chemo- or radiotherapy, can leave young prepubertal boys infertile. Such patients are recommended to undergo the cryopreservation of testicular material to protect future fertility. Within the testes, the specialized 3D structure and direct cell-to-cell interactions play a critical role in the proliferation and development of SSCs. Over recent decades, 3D culture systems and organoids have been used to culture cells in vitro, however, a system that allows investigations into testicular organogenesis in vitro, and its impact on the SSC niche, has yet to be developed.

Study design, size, duration

This study aims to develop a 3D organoid culture system to support the proliferation of SSCs and spermatogenesis. Primary bovine ITT cells and enriched SSCs were isolated and 3D organoids were generated by in vitro culture for up to 40 days. Organoid formation was observed after using different foundation cells seeded at different densities and cultured in medium containing gonadotropic supplements.

Participants/materials, setting, methods

Post-thaw bovine ITTs (2 weeks-of-age) were dissociated using two-step enzymatic digestion. Enriched SSCs were selected by Percoll gradients and differential plating. Viability and apoptosis were evaluated by trypan blue staining and TUNEL assays, respectively. SSCs were evaluated immunocytochemically for germ-cell markers (PGP-9.5, PLZF) and Sertoli cell markers (Vimentin, Sox9). Expression levels of SSCs and spermatogenesis-related genes (Plzf, Gfrα-1, Nanog, Oct4, Stra8, Thy1) were determined by real-time quantitative polymerase chain reaction (RT-qPCR).

Main results and the role of chance

The viability of digested cells from thawed ITTs was 78.667% ± 2.03. Total testicular cells (&lt;10% SSCs) and enriched SSCs(&gt;50% SSCs) were observed to self-assemble into structurally complex organoids recapitulating the cell type compartmentalization of the testis, in a 3D Matrigel-based culture system with 10% knockout serum replacement (KSR) culture medium, but not with 10% fetal bovine serum(FBS) medium. Testicular organoids were found to exhibit either a grape-like structure and a round-shape structure. Cytoplasmic extensions of spermatogonia/Sertoli cells were in contact with each other within a forming colony. Organoids were formed faster and larger when seeded at a final concentration of 1.5 × 106 cells/ml, compared to 5 × 105 cells/ml and 1.5 × 105 cells/ml. Organoids grew to a diameter of 400 μm within 10 - 15 days and were passaged by mechanical disruption at a ratio of 1:3 every 7 - 10 days. Immunocytochemistry results showed that clusters of PGP9.5 and PLZF-positive cells were present within the organoids. The expression of selected germ cell and spermatogenesis markers in the testicular organoids closely resembled that of primary testicular cells for up to 20 days of culture.

Limitations, reasons for caution

We used calves (2 weeks-of-age) as an animal model to study testicular organoids. This tissue may act differently than human tissues and may not fully represent prepuberty. Furthermore, we only evaluated gene expression levels for selected markers that may not represent the full functional capability of germ cells.

Wider implications of the findings

Testicular organoids, as an in vitro bioengineering testicular model, could potentially be used to study testicular tissue development, cellular interactions, endocrinology, and spermatogenesis, in the laboratory but may also be applied for clinical purposes in the future.

Trial registration number

University of Oxford

P–798 Fertility preservation in pre-pubertal boys with cancer: A three-dimensional prepubertal testicular organoid for in vitro spermatogonial stem cell propagation and spermatogenesis

Study question

Can a three-dimensional (3D) prepubertal testicular organoid be formed and provide an in vitro microenvironment for spermatogonial stem cells (SSCs) maintenance and future spermatogenesis?

Summary answer

Primary cells extracted from immature testicular tissue (ITT) or SSCs can be grown long-term as 3D organoids, providing the potential for in vitro study.

What is known already

Aggressive cancer treatments, such as chemo- or radiotherapy, can leave young prepubertal boys infertile. Such patients are recommended to undergo the cryopreservation of testicular material to protect future fertility. Within the testes, the specialized 3D structure and direct cell-to-cell interactions play a critical role in the proliferation and development of SSCs. Over recent decades, 3D culture systems and organoids have been used to culture cells in vitro, however, a system that allows investigations into testicular organogenesis in vitro, and its impact on the SSC niche, has yet to be developed.

Study design, size, duration

This study aims to develop a 3D organoid culture system to support the proliferation of SSCs and spermatogenesis. Primary bovine ITT cells and enriched SSCs were isolated and 3D organoids were generated by in vitro culture for up to 40 days. Organoid formation was observed after using different foundation cells seeded at different densities and cultured in medium containing gonadotropic supplements.

Participants/materials, setting, methods

Post-thaw bovine ITTs (2 weeks-of-age) were dissociated using two-step enzymatic digestion. Enriched SSCs were selected by Percoll gradients and differential plating. Viability and apoptosis were evaluated by trypan blue staining and TUNEL assays, respectively. SSCs were evaluated immunocytochemically for germ-cell markers (PGP–9.5, PLZF) and Sertoli cell markers (Vimentin, Sox9). Expression levels of SSCs and spermatogenesis-related genes (Plzf, Gfrα–1, Nanog, Oct4, Stra8, Thy1) were determined by real-time quantitative polymerase chain reaction (RT-qPCR).

Main results and the role of chance

The viability of digested cells from thawed ITTs was 78.667% ± 2.03. Total testicular cells (&lt;10% SSCs) and enriched SSCs(&gt;50% SSCs) were observed to self-assemble into structurally complex organoids recapitulating the cell type compartmentalization of the testis, in a 3D Matrigel-based culture system with 10% knockout serum replacement (KSR) culture medium, but not with 10% fetal bovine serum(FBS) medium. Testicular organoids were found to exhibit either a grape-like structure and a round-shape structure. Cytoplasmic extensions of spermatogonia/Sertoli cells were in contact with each other within a forming colony. Organoids were formed faster and larger when seeded at a final concentration of 1.5 × 106 cells/ml, compared to 5 × 105 cells/ml and 1.5 × 105 cells/ml. Organoids grew to a diameter of 400 μm within 10 - 15 days and were passaged by mechanical disruption at a ratio of 1:3 every 7 - 10 days. Immunocytochemistry results showed that clusters of PGP9.5 and PLZF-positive cells were present within the organoids. The expression of selected germ cell and spermatogenesis markers in the testicular organoids closely resembled that of primary testicular cells for up to 20 days of culture.

Limitations, reasons for caution

We used calves (2 weeks-of-age) as an animal model to study testicular organoids. This tissue may act differently than human tissues and may not fully represent prepuberty. Furthermore, we only evaluated gene expression levels for selected markers that may not represent the full functional capability of germ cells.

Wider implications of the findings: Testicular organoids, as an in vitro bioengineering testicular model, could potentially be used to study testicular tissue development, cellular interactions, endocrinology, and spermatogenesis, in the laboratory but may also be applied for clinical purposes in the future.

Trial registration number

University of Oxford

P–265 Investigating the nanotoxicity of solid silica nanoparticles in gametes following in vitro exposure

Study question

Do solid silica nanoparticles qualify as a new research tool for the in vitro transfer of compounds into gametes prior to Assisted Reproductive Technology (ART).

Summary answer

Solid silica nanoparticles (SSNPs) could be used as an intra-gamete delivery system to deliver therapeutic biomolecules into gametes prior to ART.

What is known already

Sperm-mediated gene transfer (SMGT) results in the production of transgenic embryos; however, the success rate of this technique is low. Nanoparticles are an efficient intra-cellular delivery system in vitro. Naturally cell-secreted nanoparticles are involved in the development of gametes. Mesoporous silica nanoparticles have been shown to carry large amounts of compounds and to interact with gametes without toxic effects, thus providing an alternative to naturally secreted nanoparticles. However, this technique is associated with some limitations, such as the size of these nanoparticles. SSNPs can be synthesised on a smaller nanoscale, thus providing higher potential to penetrate gametes and delivering biomolecules.

Study design, size, duration

This was an experimental in vitro study that investigated the effects of SSNPs on the motility of boar sperm and the degeneration of hamster oocytes, as determined by ooplasm shrinkage.

Participants/materials, setting, methods

SSNPs (20 nm) were conjugated with fluorescein diacetate–5-maleimide (FDA5M), a fluorescent protein. FDA5M-labelled SSNPS were incubated with boar sperm (N = 3) at 10 and 30µg/ml/107 sperm for four-hours. Motility parameters were assessed by computer-assisted sperm analysis (CASA). Binding potential was evaluated by fluorescent microscopy. Hamster oocytes (7 oocytes/group) were incubated with FDA5M-labelled SSNPs at 100, 150, and 300µg/ml, for two-hours; ooplasm shrinkage was evaluated. Time/matched control sperm was incubated in phosphate-buffered saline and oocytes in KSOM.

Main results and the role of chance

Exposure to FDA5M-labelled SSNPs did not affect total or progressive sperm motility (P = 0.6735 and 0.9606, respectively), average-path velocity or straight-line velocity after 4-hours of incubation (P = 0.7459 and 0.8696, respectively) compared to controls. SSNPs at 10 µg/ml significantly increased sperm curvilinear velocity after 1-hour (P = 0.0495) and linearity and straightness after 4-hours (P = 0.0389 and 0.0312, respectively). SSNPs at 30 µg/ml significantly increased sperm linearity after 3- and 4-hours (P = 0.0384 and 0.005, respectively). The proportion of sperm showing green fluorescence was significantly higher in the 30µg/ml dose of SSNPs than the 10µg/ml dose after 4-hours (P &lt; 0.00001). In oocytes, the zona pellucida remained morphologically intact and the ooplasm exhibited green fluorescence. The ooplasm of 42% of the oocytes at 300µg/ml showed ooplasm shrinkage (a sign of degeneration); no oocytes showed shrinkage at doses of 100 and 150µg/ml of SSNPs. The green fluorescence in the sperm head and the ooplasm indicated the ability of SSNPs to spontaneously interact non-invasively with these gametes either by surface association or by cell-internalisation. This could provide a safe and non-invasive intra-gamete delivery system for research purposes and clinical therapy. This system could be used to deliver specific agents into gametes prior to ART to improve outcomes.

Limitations, reasons for caution

The SSNPs are non-biodegradable; it remains unknown as to how gametes or embryos might react with SSNPs over long time periods. The nanotoxicity of SSNPs has not yet been investigated over the long term. SSNPs have still to be tested with embryos to evaluate their effect on embryonic development.

Wider implications of the findings: SSNPs could be functionalised to target the nucleus of mammalian gametes and embryos to act as a carrier for oligonucleotides and genes to correct chromosomal abnormalities and to provide genetic therapy in these gametes and embryos to treat hereditary diseases before intra-uterine transfer.

Trial registration number

Not applicable

Use of phospholipase C zeta analysis to identify candidates for artificial oocyte activation: a case series of clinical pregnancies and a proposed algorithm for patient management

OBJECTIVE

To investigate the applicability of phospholipase C zeta (PLCζ) analysis in assisting the clinical decision-making process when considering artificial oocyte activation (AOA) for infertile males in assisted reproductive technology.

DESIGN

Fifty-six males (43 infertile/13 fertile) were screened using our PLCζ assay.

SETTING

Fertility unit/university laboratory.

PATIENT(S)

Infertile males with abnormal sperm morphology or total fertilization failure, low fertilization rate (<50%), or repeated fertilization failure in assisted reproductive technology.

INTERVENTION(S)

We analyzed PLCζ levels in sperm from fertile and infertile males. Eligible patients subsequently underwent intracytoplasmic sperm injection (ICSI)/artificial oocyte activation (AOA) with calcimycin (GM508).

MAIN OUTCOME MEASURE(S)

PLCζ localization and level and the proportion of sperm expressing PLCζ. Thresholds of PLCζ deficiency, fertilization rates, pregnancy rates, and live birth rates of AOA and non-AOA cycles.

RESULT(S)

Compared with 13 fertile controls, 34 of the 43 infertile males had significantly lower levels of PLCζ and/or a significantly lower proportion of sperm exhibiting PLCζ. Of these 34 patients, 15 showed a significant PLCζ reduction in both parameters, which we termed "PLCζ deficiency." Five PLCζ-deficient patients opted for AOA; all five achieved fertilization, and four achieved clinical pregnancies and live births. The fertilization rate improved significantly from 18.6% (ICSI) to 56.8% (ICSI/AOA). The clinical pregnancy rate and live birth rate with AOA were both 40% per initiated cycle. Youden index analysis revealed that the cutoffs below which infertile males were likely to benefit from AOA were 71% for the proportion of sperm expressing PLCζ and 15.57 arbitrary units for mean PLCζ level.

CONCLUSION(S)

PLCζ analysis is a useful diagnostic tool to determine patient eligibility for subsequent AOA treatment.

Advancing male age differentially alters levels and localization patterns of PLCzeta in sperm and testes from different mouse strains

Sperm-specific phospholipase C zeta (PLCζ) initiates intracellular calcium (Ca²⁺) transients which drive a series of concurrent events collectively termed oocyte activation. Numerous investigations have linked abrogation and absence/reduction of PLCζ with forms of male infertility in humans where oocyte activation fails. However, very few studies have examined potential relationships between PLCζ and advancing male age, both of which are increasingly considered to be major effectors of male fertility. Initial efforts in humans may be hindered by inherent PLCζ variability within the human population, alongside a lack of sufficient controllable repeats. Herein, utilizing immunoblotting, immunofluorescence, and quantitative reverse transcription PCR (qRT-PCR) we examined for the first time PLCζ protein levels and localization patterns in sperm, and PLCζ mRNA levels within testes, from mice at 8 weeks, 12 weeks, 24 weeks, and 36 weeks of age, from two separate strains of mice, C57BL/6 (B6; inbred) and CD1 (outbred). Collectively, advancing male age generally diminished levels and variability of PLCζ protein and mRNA in sperm and testes, respectively, when both strains were examined. Furthermore, advancing male age altered the predominant pattern of PLCζ localization in mouse sperm, with younger mice exhibiting predominantly post-acrosomal, and older mice exhibiting both post-acrosomal and acrosomal populations of PLCζ. However, the specific pattern of such decline in levels of protein and mRNA was strain-specific. Collectively, our results demonstrate a negative relationship between advancing male age and PLCζ levels and localization patterns, indicating that aging male mice from different strains may serve as useful models to investigate PLCζ in cases of male infertility and subfertility in humans.

Establishment of a relationship between blastomere geometry and YAP localisation during compaction

Precise patterning within the three-dimensional context of tissues, organs and embryos implies that cells can sense their relative position. During preimplantation development, outside and inside cells rely on apicobasal polarity and the Hippo pathway to choose their fate. Despite recent findings suggesting that mechanosensing might be central to this process, the relationship between blastomere geometry (i.e. shape and position) and the Hippo pathway effector YAP remains unknown. We used a highly quantitative approach to analyse information on the geometry and YAP localisation of individual blastomeres of mouse and human embryos. We identified the proportion of exposed cell surface area as most closely correlating with the nuclear localisation of YAP. To test this relationship, we developed several hydrogel-based approaches to alter blastomere geometry in cultured embryos. Unbiased clustering analyses of blastomeres from such embryos revealed that this relationship emerged during compaction. Our results therefore pinpoint the time during early embryogenesis when cells acquire the ability to sense changes in geometry and provide a new framework for how cells might integrate signals from different membrane domains to assess their relative position within the embryo.

Highlighted Article: Localisation of YAP, a key factor during the first cell fate decision, is linked to individual blastomere geometry within the three-dimentional environment of the preimplantation embryo.

Exosomes derived from HEK293T cells interact in an efficient and noninvasive manner with mammalian sperm in vitro

Aim: To investigate exosomes as a noninvasive delivery tool for mammalian sperm. Materials & Methods: Exosomes were isolated from HEK293T cells and co-incubated with boar sperm in vitro. Results: Internalized exosomes were detected within 10 min of co-incubation. Computer-assisted sperm analysis and flow cytometry demonstrated that even after 5-h of exposure to exosomes, there were no significant deleterious effects with regard to sperm motility, viability, membrane integrity and mitochondrial membrane potential (p > 0.05), thus indicating that exosomes did not interfere with basic sperm function. Conclusion: HEK293T-derived exosomes interacted with boar sperm without affecting sperm function. Exosomes represent a versatile and promising research tool for studying sperm biology and provide new options for the diagnosis and treatment of male infertility.

The use of autologous platelet-rich plasma (PRP) versus no intervention in women with low ovarian reserve undergoing fertility treatment: a non-randomized interventional study

PURPOSE

To investigate the impact of a 3-month course of intracortical injections of autologous platelet-rich plasma (PRP) upon ovarian reserve markers versus no intervention in women with low ovarian reserve prior to undergoing assisted reproductive technology (ART).

METHODS

Prospective controlled, non-randomized comparative study conducted in a private fertility clinic, in Venezuela. Women with abnormal ovarian reserve markers (FSH, AMH and AFC) who declined oocyte donation were allocated to one of the following groups according to patient choice: monthly intracortical ovarian PRP injections for three cycles, or no intervention. Primary outcomes were the change in FSH, AMH and AFC pre- and post-treatment. Secondary outcomes included the number of oocytes collected and fertilized, biochemical/clinical pregnancy rates and miscarriage and live birth rates.

RESULTS

Eighty-three women were included, of which 46 received PRP treatment and 37 underwent no intervention. Overall median age was 41 years (IQR 39-44). There were no demographic differences between the study groups. At the 3-month follow-up, women treated with PRP experienced a significant improvement in FSH, AMH and AFC, whereas there was no change in the control group. Furthermore, overall rates of biochemical (26.1% versus 5.4%, P = 0.02) and clinical pregnancy (23.9% versus 5.4%, P = 0.03) were higher in the PRP group, while there was no difference in the rates of first trimester miscarriage and live birth between groups.

CONCLUSION

PRP injections are effective and safe to improve markers of low ovarian reserve prior to ART, although further evidence is required to evaluate the impact of PRP on pregnancy outcomes.

Nanomedicine applications in women's health: state of the art

State-of-the-art applications of nanomedicine have the potential to revolutionize the diagnosis, prevention, and treatment of a range of conditions and diseases affecting women’s health. In this review, we provide a synopsis of potential applications of nanomedicine in some of the most dominant fields of women’s health: mental health, sexual health, reproductive medicine, oncology, menopause-related conditions and dementia. We explore published studies arising from in vitro and in vivo experiments, and clinical trials where available, to reveal novel and highly promising therapeutic applications of nanomedicine in these fields. For the first time, we summarize the growing body of evidence relating to the use of nanomaterials as experimental tools for the detection, prevention, and treatment of significant diseases and conditions across the life course of a cisgender woman, from puberty to menopause; revealing the far-reaching and desirable theoretical impact of nanomedicine across different medical disciplines. We also present an overview of potential concerns regarding the therapeutic applications of nanomedicine and the factors currently restricting the growth of applied nanomedicine.

Oocyte Activation and Fertilisation: Crucial Contributors from the Sperm and Oocyte

This chapter intends to summarise the importance of sperm- and oocyte-derived factors in the processes of sperm-oocyte binding and oocyte activation. First, we describe the initial interaction between sperm and the zona pellucida, with particular regard to acrosome exocytosis. We then describe how sperm and oocyte membranes fuse, with special reference to the discovery of the sperm protein IZUMO1 and its interaction with the oocyte membrane receptor JUNO. We then focus specifically upon oocyte activation, the fundamental process by which the oocyte is alleviated from metaphase II arrest by a sperm-soluble factor. The identity of this sperm factor has been the source of much debate recently, although mounting evidence, from several different laboratories, provides strong support for phospholipase C ζ (PLCζ), a sperm-specific phospholipase. Herein, we discuss the evidence in support of PLCζ and evaluate the potential role of other candidate proteins, such as post-acrosomal WW-binding domain protein (PAWP/WBP2NL). Since the cascade of downstream events triggered by the sperm-borne oocyte activation factor heavily relies upon specialised cellular machinery within the oocyte, we also discuss the critical role of oocyte-borne factors, such as the inositol trisphosphate receptor (IP₃R), protein kinase C (PKC), store-operated calcium entry (SOCE) and calcium/calmodulin-dependent protein kinase II (CaMKII), during the process of oocyte activation. In order to place the implications of these various factors and processes into a clinical context, we proceed to describe their potential association with oocyte activation failure and discuss how clinical techniques such as the in vitro maturation of oocytes may affect oocyte activation ability. Finally, we contemplate the role of artificial oocyte activating agents in the clinical rescue of oocyte activation deficiency and discuss options for more endogenous alternatives.

Development of a laser-activated mesoporous silica nanocarrier delivery system for applications in molecular and genetic research

Nanoparticles have revolutionized medical research over the last decade. One notable emerging area of nanomedicine is research developments in the reproductive sciences. Since increasing evidence indicates links between abnormal gene expression and previously unexplained states of infertility, there is a strong impetus to develop tools, such as nanoparticle platforms, to elucidate the pathophysiological mechanisms underlying such states. Mesoporous silica nanoparticles (MSNPs) represent a powerful and safe delivery tool for molecular and genetic investigations. Nevertheless, ongoing progress is restricted by low efficiency and unpredictable control of cargo delivery. Here, we describe for the first time, the development of a laser-activated MSNP system with heat-responsive cargo. Data derived from human embryonic kidney cells (HEK293T) indicate that when driven by a heat-shock promoter, MSNP cargo exhibits a significantly increased expression following infrared laser stimulus to stimulate a heat-shock response, without adverse cytotoxic effects. This delivery platform, with increased efficiency and the ability to impart spatial and temporal control, is highly useful for molecular and genetic investigations. We envision that this straightforward stimuli-responsive system could play a significant role in developing efficient nanodevices for research applications, for example in reproductive medicine.

Does advancing male age influence the expression levels and localisation patterns of phospholipase C zeta (PLCζ) in human sperm?

Socio-economic factors have led to an increasing trend for couples to delay parenthood. However, advancing age exerts detrimental effects upon gametes which can have serious consequences upon embryo viability. While such effects are well documented for the oocyte, relatively little is known with regard to the sperm. One fundamental role of sperm is to activate the oocyte at fertilisation, a process initiated by phospholipase C zeta (PLCζ), a sperm-specific protein. While PLCζ deficiency can lead to oocyte activation deficiency and infertility, it is currently unknown whether the expression or function of PLCζ is compromised by advancing male age. Here, we evaluate sperm motility and the proportion of sperm expressing PLCζ in 71 males (22–54 years; 44 fertile controls and 27 infertile patients), along with total levels and localisation patterns of PLCζ within the sperm head. Three different statistical approaches were deployed with male age considered both as a categorical and a continuous factor. While progressive motility was negatively correlated with male age, all three statistical models concurred that no PLCζ–related parameter was associated with male age, suggesting that advancing male age is unlikely to cause problems in terms of the sperm’s fundamental ability to activate an oocyte.

Phospholipase C zeta (PLCζ) and male infertility: Clinical update and topical developments

The development of a mammalian embryo is initiated by a sequence of molecular events collectively referred to as 'oocyte activation' and regulated by the release of intracellular calcium in the ooplasm. Over the last decade, phospholipase C zeta (PLCζ), a sperm protein introduced into the oocyte upon gamete fusion, has gained almost universal acceptance as the protein factor responsible for initiating oocyte activation. A large body of consistent and reproducible evidence, from both biochemical and clinical settings, confers support for the role of PLCζ in this fundamental biological context, which has significant ramifications for the management of human male infertility. Oocyte activation deficiency (OAD) and total fertilisation failure (TFF) are known causes of infertility and have both been linked to abnormalities in the structure, expression, and localisation pattern of PLCζ in human sperm. Assisted oocyte activators (AOAs) represent the only therapeutic option available for OAD at present, although these agents have been the source of much debate recently, particularly with regard to their potential epigenetic effects upon the embryo. Consequently, there is much interest in the deployment of sensitive PLCζ assays as prognostic/diagnostic tests and human recombinant PLCζ protein as an alternative form of therapy. Although PLCζ deficiency has been directly linked to a cohort of infertile cases, we have yet to identify the specific causal mechanisms involved. While two genetic mutations have been identified which link defective PLCζ protein to an infertile phenotype, both were observed in the same patient, and have yet to be described in other patients. Consequently, some researchers are investigating the possibility that genetic variations in the form of single nucleotide polymorphisms (SNPs) could provide some explanation, especially since >6000 SNPs have been identified in the PLCζ gene. As yet, however, there is no consistent data to suggest that any of these SNPs influence the functional ability of PLCζ. Other laboratories appear to be focussing upon the PLCζ promoter, which is bi-directional and shared with the actin filament capping muscle Z-line alpha 3 gene (CAPZA3), or seeking to identify interacting proteins within the ooplasm. The aim of this review is to provide a synopsis of recent progress in the application of PLCζ in diagnostic and therapeutic medicine, to discuss our current understanding of how the functional ability of PLCζ might be controlled, and thus how PLCζ deficiency might arise, and finally, to consider the potential implications of alternative sperm protein candidates, such as post-acrosomal WW-domain binding protein (PAWP), which has caused much debate and confusion in the field over the last few years.

Total levels, localization patterns, and proportions of sperm exhibiting phospholipase C zeta are significantly correlated with fertilization rates after intracytoplasmic sperm injection

OBJECTIVE

To study the relationship of total levels, localization patterns, and proportions of sperm exhibiting phospholipase C zeta, with fertilization rates after in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).

DESIGN

Laboratory study; controls vs. patients after IVF (n = 27) or ICSI (n = 17) treatment.

SETTING

Fertility center.

PATIENT(S)

A total of 44 semen samples, subjected to either IVF or ICSI treatment. Oocyte collection, ICSI or IVF, determination of sperm concentration and motility, and immunocytochemical analyses of phospholipase C zeta (PLCζ).

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Percentages of sperm exhibiting PLCζ.

RESULT(S)

Significant positive correlation between ICSI fertilization rates and total levels, localization patterns, and the proportion (percentage) of sperm exhibiting PLCζ. Total levels, localization patterns, and the proportion of sperm exhibiting PLCζ are correlated with fertilization rates for ICSI, but not for IVF.

CONCLUSION(S)

Evaluating total levels, localization patterns, and proportions of PLCζ may represent a useful diagnostic tool for clinical purposes in men for whom IVF is not advised or has previously failed. This clinical study further supports the fundamental role of PLCζ in the oocyte activation process.

Extracellular vesicle-mediated delivery of molecular compounds into gametes and embryos: learning from nature

BACKGROUND

Currently, even the most sophisticated methods of assisted reproductive technology (ART) allow us to achieve live births in only approximately 30% of patients, indicating that our understanding of the fine mechanisms underlying reproduction is far from ideal. One of the main challenges associated with studies of gamete structure and function is that these cells are remarkably resistant towards the uptake of exogenous substances, including 'molecular research tools' such as drugs, biomolecules and intracellular markers. This phenomenon can affect not only the performance of reproductive biology research techniques, but also the outcomes of the in vitro handling of gametes, which forms the cornerstone of ART. Improvement of intra-gamete delivery in a non-aggressive fashion is vital for the investigation of gamete physiology, and the advancement of infertility treatment. In this review, we outline the current state of nanomaterial-mediated delivery into gametes and embryos in vitro, and discuss the potential of a novel exciting drug delivery technology, based upon the use of targeted 'natural' nanoparticles known as extracellular vesicles (EVs), for reproductive science and ART, given the promising emerging data from other fields.

METHODS

A comprehensive electronic search of PubMed and Web of Science databases was performed using the following keywords: 'nanoparticles', 'nanomaterials', 'cell-penetrating peptides', 'sperm', 'oocyte', 'egg', 'embryo', 'exosomes', 'microvesicles', 'extracellular vesicles', 'delivery', 'reproduction', to identify the relevant research and review articles, published in English up to January 2015. The reference lists of identified publication were then scanned to extract additional relevant publications.

RESULTS

Biocompatible engineered nanomaterials with high loading capacity, stability and selective affinity represent a potential versatile tool for the minimally invasive internalization of molecular cargo into gametes and embryos. However, it is becoming increasingly clear that the translation of these experimental tools into clinical applications is likely to be limited by their non-biodegradable nature. To allow the subsequent use of these methodologies for clinical ART, studies should utilize biodegradable delivery platforms, which mimic natural mechanisms of molecular cargo trafficking as closely as possible. Currently, EVs represent the most physiological intracellular delivery tools for reproductive science and medicine. These natural mediators of cell communication combine the benefits of engineered nanomaterials, such as the potential for in vitro production, targeting and loading, with the essential feature of biodegradability.

CONCLUSION

We anticipate that future investigations into the possibility of applying EVs for the intentional intracellular delivery of molecular compounds into gametes and embryos will open new horizons for reproductive science and clinical ART, ultimately leading to improvements in patient care.

Nanomedicine and mammalian sperm: Lessons from the porcine model

Biomedical nanotechnology allows us to engineer versatile nanosized platforms that are comparable in size to biological molecules and intracellular organelles. These platforms can be loaded with large amounts of biological cargo, administered systemically and act at a distance, target specific cell populations, undergo intracellular internalization via endogenous uptake mechanisms, and act as contrast agents or release cargo for therapeutic purposes. Over recent years, nanomaterials have been increasingly viewed as favorable candidates for intragamete delivery. Particularly in the case of sperm, nanomaterial-based approaches have been shown to improve the efficacy of existing techniques such as sperm-mediated gene transfer, loading sperm with exogenous proteins, and tagging sperm for subsequent sex- or function-based sorting. In this short review, we provide an outline of the current state of nanotechnology for biomedical applications in reproductive biology and present highlights from a series of our studies evaluating the use of specialized silica nanoparticles in boar sperm as a potential delivery vehicle into mammalian gametes. The encouraging data obtained already from the porcine model in our laboratory have formed the basis for ethical approval of similar experiments in human sperm, thereby bringing us a step closer toward the potential use of this novel technology in the clinical environment.

Functionalization of mesoporous silica nanoparticles with a cell-penetrating peptide to target mammalian sperm in vitro

Aim: This study aimed to investigate the effects of actively targeting mesoporous silica nanoparticles (MSNPs) toward mammalian sperm with a cell-penetrating peptide (C105Y), with subsequent analysis of binding rates and nano-safety profiles. Materials & methods: Boar sperm were exposed in vitro to C105Y-functionalized MSNPs or free C105Y, in a series of increasing doses for up to 2 h, followed by the evaluation of sperm motility, kinematic parameters, acrosome morphology, MSNP-sperm binding and cell fluorescence levels. Results: C105Y-functionalized MSNPs preserved their biocompatibility with sperm, and exhibited an approximately fourfold increase in affinity toward gametes, compared with unmodified MSNPs, during the early stages of incubation. Conclusion: Our findings support the application of MSNPs and active targeting to sperm as valuable tools for reproductive biology.

Phospholipase C zeta (PLCζ): oocyte activation and clinical links to male factor infertility

Mounting scientific and clinical evidence supports the key role played by phospholipase C zeta (PLCζ), a sperm-specific protein, in the activation of oocytes following fertilisation. Lacking a pleckstrin homology domain, PLCζ remains the smallest known mammalian PLC and was first identified in 2002. Since then, PLCζ has been the target for a multitude of studies in both mammalian and non-mammalian species focused upon its fundamental biochemical activity and crucial role as the mediator of oocyte activation. The earliest event subsequent to gamete fusion is the onset of a series of intracellular calcium oscillations within the oocyte, which are known to modulate cortical granule exocytosis, release meiotic arrest, regulate gene expression, recruit maternal mRNA, and initiate embryogenesis. Collectively these processes are known as 'oocyte activation' and together, represent a fundamental mechanism for early embryonic development. Evidence suggests that these processes are initiated and controlled by calcium release from ooplasmic sources in response to PLCζ activity via the inositol-1,4,5-triphosphate (IP3) pathway. While the biochemical action of PLCζ has been extensively studied, especially in relation to the EF-hands, X-Y linker, and C2 domain, all of which play critical roles for in vivo activity, there are still key gaps in our knowledge, particularly in terms of regulation and interaction with other proteins within the oocyte. Moreover, increasing clinical evidence has revealed a strong correlation between certain types of male infertility and the aberrant expression, localisation, structure and function of PLCζ in human sperm, particularly in cases of recurrent intracytoplasmic sperm injection (ICSI) failure, globozoospermia, and oocyte activation deficiency (OAD). In addition, two heterozygous substitution mutations have been identified in the coding sequence of PLCζ in one particular patient causing disruption to the catalytic X and Y domains and resulting in infertility. Although, such cases can be treated via the use of artificial oocyte activators (AOAs) such as calcium ionophores, significant concern remains over the use of such chemical agents, largely due to the fact that calcium release manifests as a single transient, rather than a series of oscillations as observed during normal fertilisation. Current interest in PLCζ is thus to develop a series of prognostic, diagnostic and therapeutic approaches which could first identify male patients that are deficient in PLCζ and then rescue oocyte activation ability via assisted reproductive technology (ART) and a pure, functionally-active, recombinant human PLCζ protein. While significant progress has been made in such areas over recent years, there is a clear need to translate scientific findings to clinical settings in order to maximise successful outcome for patients.

Comparative biology of sperm factors and fertilization-induced calcium signals across the animal kingdom

Fertilization causes mature oocytes or eggs to increase their concentrations of intracellular calcium ions (Ca²⁺) in all animals that have been examined, and such Ca²⁺ elevations, in turn, provide key activating signals that are required for non-parthenogenetic development. Several lines of evidence indicate that the Ca²⁺ transients produced during fertilization in mammals and other taxa are triggered by soluble factors that sperm deliver into oocytes after gamete fusion. Thus, for a broad-based analysis of Ca²⁺ dynamics during fertilization in animals, this article begins by summarizing data on soluble sperm factors in non-mammalian species, and subsequently reviews various topics related to a sperm-specific phospholipase C, called PLCζ, which is believed to be the predominant activator of mammalian oocytes. After characterizing initiation processes that involve sperm factors or alternative triggering mechanisms, the spatiotemporal patterns of Ca²⁺ signals in fertilized oocytes or eggs are compared in a taxon-by-taxon manner, and broadly classified as either a single major transient or a series of repetitive oscillations. Both solitary and oscillatory types of fertilization-induced Ca²⁺ signals are typically propagated as global waves that depend on Ca²⁺ release from the endoplasmic reticulum in response to increased concentrations of inositol 1,4,5-trisphosphate (IP₃). Thus, for taxa where relevant data are available, upstream pathways that elevate intraoocytic IP3 levels during fertilization are described, while other less-common modes of producing Ca²⁺ transients are also examined. In addition, the importance of fertilization-induced Ca²⁺ signals for activating development is underscored by noting some major downstream effects of these signals in various animals.

Motile sperm organelle morphology evaluation-selected globozoospermic human sperm with an acrosomal bud exhibits novel patterns and higher levels of phospholipase C zeta

STUDY QUESTION

Does motile sperm organelle morphology examination (MSOME) affect levels and localization patterns of the oocyte activation factor phospholipase C zeta (PLCζ) in globozoospermic sperm with and without an acrosomal bud?

SUMMARY ANSWER

MSOME identified round-headed globozoospermic sperm with increased levels of PLCζ relative to sperm from the same sample that did not undergo MSOME, and identified novel patterns of PLCζ localization in sperm exhibiting an acrosomal bud.

WHAT IS KNOWN ALREADY

Absence or reduction in the level of PLCζ in the sperm head, abnormal localization patterning, or defective functional ability as a result of PLCζ gene mutation, have been linked to certain types of human male factor infertility in which oocyte activation is deficient. It has been determined that a subpopulation of sperm (1%) from a patient exhibiting 100% globozoospermia presented with an acrosome bud upon MSOME. A cycle of intracytoplasmic morphologically selected sperm injection, carried out with sperm exhibiting an acrosomal bud led to pregnancy and birth of a healthy baby boy, without the use of assisted oocyte activation (AOA).

STUDY DESIGN, SIZE, DURATION

Immunofluorescent analysis of PLCζ in globozoospermic sperm from three patients, before and after MSOME.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Quantitative immunofluorescence was used to investigate PLCζ levels and localization patterns in individual sperm (n = 1 patient) identified by MSOME and isolated by micromanipulation, and presenting with and without the acrosomal bud. A secondary aim was to investigate levels and localization patterns of PLCζ in sperm before and after MSOME from two other globozoospermic men.

MAIN RESULTS AND THE ROLE OF CHANCE

Non-globozoospermic control sperm exhibited characteristic localization patterns of PLCζ immunofluorescence. Completely round-headed globozoospermic sperm from patients 1-3 were either devoid of PLCζ immunofluorescence, or exhibited an abnormal, punctate, pattern of PLCζ localization. PLCζ immunofluorescence in sperm exhibiting an acrosomal bud was observed in the midpiece with varying fluorescent intensity and was detected in 28.5% of such sperm. The majority of sperm with an acrosomal bud (43.0%) exhibited punctate patterns of PLCζ localization within the sperm head. A further 28.5% of sperm exhibited PLCζ in both the head and the midpiece. Total levels of PLCζ, and the proportions of sperm exhibiting PLCζ immunoreactivity, showed significant variance (P ≤ 0.05) amongst control [45.8 arbitrary units (a.u.) and 95.7%, respectively], non-MSOME-selected (25.9 a.u. and 46.1%, respectively) and MSOME-selected globozoospermic sperm (33.4 a.u. and 65.0%, respectively). Total levels of PLCζ immunofluorescence, and proportions of sperm exhibiting PLCζ immunoreactivity, in control sperm was significantly higher (P≤ 0.05) compared with non-MSOME-selected sperm, but not significantly different from MSOME-selected sperm.

LIMITATIONS, REASONS FOR CAUTION

The low numbers of sperm analysed may not be ideal for conclusive statistical analysis. Evaluation of the effects of MSOME on morphologically normal sperm would confirm conclusions.

WIDER IMPLICATIONS OF THE FINDINGS

The present findings provide hope for the future treatment of globozoospermia without the need for AOA, and provide further evidence for the clinical application of PLCζ as a therapeutic and prognostic tool.

STUDY FUNDING/COMPETING INTEREST(S)

The research described herein was funded by the Nuffield Department of Obstetrics and Gynaecology, University of Oxford. The authors report no conflict of interest.

Oocyte activation and phospholipase C zeta (PLCζ): diagnostic and therapeutic implications for assisted reproductive technology

Infertility affects one in seven couples globally and has recently been classified as a disease by the World Health Organisation (WHO). While in-vitro fertilisation (IVF) offers effective treatment for many infertile couples, cases exhibiting severe male infertility (19-57%) often remain difficult, if not impossible to treat. In such cases, intracytoplasmic sperm injection (ICSI), a technique in which a single sperm is microinjected into the oocyte, is implemented. However, 1-5% of ICSI cycles still fail to fertilise, affecting over 1000 couples per year in the UK alone. Pregnancy and delivery rates for IVF and ICSI rarely exceed 30% and 23% respectively. It is therefore imperative that Assisted Reproductive Technology (ART) protocols are constantly modified by associated research programmes, in order to provide patients with the best chances of conception. Prior to fertilisation, mature oocytes are arrested in the metaphase stage of the second meiotic division (MII), which must be alleviated to allow the cell cycle, and subsequent embryogenesis, to proceed. Alleviation occurs through a series of concurrent events, collectively termed 'oocyte activation'. In mammals, oocytes are activated by a series of intracellular calcium (Ca2+) oscillations following gamete fusion. Recent evidence implicates a sperm-specific phospholipase C, PLCzeta (PLCζ), introduced into the oocyte following membrane fusion as the factor responsible. This review summarises our current understanding of oocyte activation failure in human males, and describes recent advances in our knowledge linking certain cases of male infertility with defects in PLCζ expression and activity. Systematic literature searches were performed using PubMed and the ISI-Web of Knowledge. Databases compiled by the United Nations and World Health Organisation databases (UNWHO), and the Human Fertilization and Embryology Authority (HFEA) were also scrutinised. It is clear that PLCζ plays a fundamental role in the activation of mammalian oocytes, and that genetic, molecular, or biochemical perturbation of this key enzyme is strongly linked to human infertility where oocyte activation is deficient. Consequently, there is significant scope for our understanding of PLCζ to be translated to the ART clinic, both as a novel therapeutic agent with which to rescue oocyte activation deficiency (OAD), or as a prognostic/diagnostic biomarker of oocyte activation ability in target sperm samples.

Characterization of two heterozygous mutations of the oocyte activation factor phospholipase C zeta (PLCζ) from an infertile man by use of minisequencing of individual sperm and expression in somatic cells

OBJECTIVE

To examine the underlying factors leading to infertility in a male patient from whom phospholipase C zeta H398P (PLCζ(H398P), histidine > proline) and PLCζ(H233L) (histidine > leucine) mutations were previously identified.

DESIGN

Laboratory-based study.

SETTING

University laboratory.

PATIENT(S)

An infertile 38-year-old man with significantly impaired oocyte activation ability.

INTERVENTION(S)

Minisequencing of individual sperm for PLCζ(H398P) and PLCζ(H233L), and investigation of localization patterns arising from the expression of fluorescently tagged PLCζ isoforms in HEK293T cells.

MAIN OUTCOME MEASURE(S)

The presence/absence of PLCζ(H398P) and PLCζ(H233L) determined in individual sperm (n = 12 sperm), and localization of fluorescent mutant PLCζ isoforms quantified in HEK293T cells.

RESULT(S)

Sperm possessed either PLCζ(H233L) or PLCζ(H398P), but never both at the same time. Fluorescent PLCζ(H233L) and PLCζ(H233L+H398P) (both mutations together) localized to discrete regions in HEK293T cytoplasm but not the plasma membrane. Fluorescence statistically significantly varied between constructs such that PLCζ(WT) > mutant isoforms at both 48- and 56-hour time points. Fluorescent-PLCζ(H233L+H398P) exhibited a statistically significantly reduced level of fluorescence compared with PLCζ(H398P) at 48 hours but not 56 hours.

CONCLUSION(S)

Both H398P and H233L mutations are present on different alleles and do not alter PLCζ localization in HEK293T cells. Loss-of-activity mutations in PLCζ may contribute not only toward male infertility but also male subfertility in cases where PLCζ is mutated on a single allele.