Assessment of embryologist sufficiency and associated regional disparities in Japanese assisted reproduction facilities using nationwide survey data (IZANAMI project).

AIMS: This study aims to comprehensively examine the employment and practices of embryologists in Japan's assisted reproductive technology (ART) laboratories, focusing on the impact of various factors such as ART cycle numbers, add-ons, and regional differences. Additionally, it seeks to assess the extent to which Japanese ART facilities meet international minimum standards set by the American Society for Reproductive Medicine (ASRM). METHODS: A survey was conducted from December 2021 to February 2022 among 621 ART facilities in Japan. The study categorized facilities into five ART cycle groups and compared the number of embryologists across these groups. It also examined the correlation between the number of embryologists, ART cycles, add-ons, and regional differences. Data were analyzed using linear regression and multiple linear regression analyses. RESULTS: The study's findings revealed a significant correlation between the total number of embryologists at each facility and the ART cycles. Notably, there were significant differences in the number of embryologists across all ART cycle categories. Of the 435 facilities, only 44.6% met the ASRM minimum embryologist staffing requirement. The regression analysis further highlighted the significance of ART cycles and preimplantation genetic testing for aneuploidies as factors. Moreover, the number of embryologists stationed at urban facilities was significantly higher than at nonurban facilities, indicating a potential regional disparity. CONCLUSION: In Japan, it was first found that more than 50% of ART facilities do not have sufficient embryologists in place relative to the number of ART cycles. Furthermore, the add-ons and regional differences affect the placement of embryologists.

CD9 protects the sperm from cytotoxic factors in the epididymis as extracellular components.

The mechanism by which seemingly normal sperm cause infertility is still under debate. Although CD9 is expressed in male reproductive tissues, its role in male fertility remains unclear. To address this, we investigated the role of CD9 in analyzing Cd9 -deficient ( Cd9 -KO) male mice. The litter size of Cd9 -KO males was comparable, regardless of mating experience. When Cd9 -KO males experienced their first mating chance, a considerable number of neonates died 48 hours after birth. Electron microscopy reveals the presence of CD9 in the epididymal space. Our results suggest that CD9 contributes to male fertility as an extracellular component.

Fact-finding survey on assisted reproductive technology in Japan.

AIMS: In anticipation of the future development of assisted reproductive technology (ART) and to smoothly introduce new technology, it is necessary to understand the current staffing status of the medical system and the current state of treatment, as well as the status of in vitro fertilization add-ons, where the need for insurance coverage is currently a matter of debate. METHODS: ART facilities in Japan were surveyed (437 valid responses, response rate: 71%). Current staffing status of the medical system, implementation rates of ART, add-on treatments, and medical supplies were investigated. RESULTS: Despite the abundance of embryologists, nurses, and obstetricians and gynecologists in facilities, the majority of facilities lacked counselors, anesthesiologists, and other essential medical professionals. Conventional ovarian stimulation was widely adopted (median 120 [interquartile range 60-300] cycles), followed by mild ovarian simulation (60 [30-200]). Additionally, freeze-thaw embryo transfer cycles (300 [120-750]) were performed more frequently than fresh embryo transfer cycles (30 [30-60]). Among the add-ons, assisted hatching (85.1%), chronic endometritis examination (77.2%) and treatment (76.9%), artificial oocyte activation (67.3%), endometrial receptivity analysis (64.2%), and endometrial microbiome analysis (58.9%) were relatively widely employed. CONCLUSIONS: The implementation of frozen-thawed embryo transfer cycles, freeze-all strategies, and add-on treatments have become popular and widely accepted despite the lack of robust evidence regarding their safety and efficacy.

Fertility preservation after gonadotoxic treatments for cancer and autoimmune diseases.

BACKGROUND: The indications for fertility preservation (FP) have expanded. A few patients who underwent gonadotoxic treatment did not have the opportunity to receive FP, leading to concerns that these patients may develop premature ovarian insufficiency. However, the usefulness of FP in women with reduced ovarian reserve has also been questioned. Progestin-primed ovarian stimulation can improve the controlled ovarian stimulation (COS) protocol, but there is limited data on the efficacy of FP with progestin-primed ovarian stimulation. METHODS: We conducted a prospective study of 43 women with cancer or autoimmune diseases before and after gonadotoxic treatment at the reproductive unit of Keio University Hospital, counselled between 1 January 2018 and 31 December 2021. After counselling, informed consent was obtained for FP from 43 patients, with those who underwent gonadotoxic treatment of the primary disease being prioritised. Gonadotropin-releasing hormone analogue or progestin was used to suppress luteinising hormone in COS before or after gonadotoxic treatment. The number of cryopreserved mature oocytes was the primary outcome. RESULTS: Forty-three patients and 67 assisted reproductive technology cycles were included in the analysis. The median age at entry was 32 [inter quartile range (IQR), 29-37] years. All patients in the post-gonadotoxic treatment group had their oocytes frozen. Gonadotoxic treatment resulted in fewer oocytes [median 3 (IQR 1-4); pre-gonadotoxic treatment group: five patients, 13 cycles] vs. median 9 (IQR 5-14; pre-gonadotoxic treatment group: 38 patients, 54 cycles; P < 0.001). Although anti-Müllerian hormone levels were lower in the post-gonadotoxic treatment group (n = 5, 13 cycles, median 0.29 (IQR 0.15-1.04) pg/mL) than in the pre-gonadotoxic treatment group (n = 38, 54 cycles, median 1.89 (IQR 1.15-4.08) pg/mL) (P = 0.004), oocyte maturation rates were higher in the post-gonadotoxic treatment group [median 100 (IQR 77.5-100) %] than in the pre-gonadotoxic group [median 90.3 (IQR 75.0-100) %; P = 0.039]. Five patients in the pre-gonadotoxic treatment group had their cryopreserved embryos thawed, of which three had live births. CONCLUSIONS: Oocytes obtained for FP from women with cancer or autoimmune disease for FP are of satisfactory quality, regardless of whether they are obtained post-gonadotoxic treatment or COS protocols.

Identification of a syncytin gene in a non-rodent laboratory mammal, Suncus murinus.

An endogenous retrovirus-derived membrane protein, syncytin (SYN), contributes to placental function via trophoblast fusion. Multinuclear trophoblasts (syncytiotrophoblasts) physically and functionally mediate the interaction between fetal and maternal vessels in various ways. Suncus murinus (suncus) is a small mammalian species with a pregnancy duration of approximately 30 days, 1.5 times longer than mice. However, the molecular basis for the longer pregnancy duration is unknown. In this study, we first isolated two genes that encoded putative SYN proteins expressed in the suncus placenta, which were named syncytin-1-like proteins 1 and 2 (SYN1L1 and SYN1L2). When their expression vectors were introduced into cultured cells, suncus SYN1L2 was found to be active in cell fusion. Moreover, the SYN1L2 protein was homologous to a SYN1-like protein identified in greater mouse-eared bats (bat SYN1L) and was structurally compared with bat SYN1L and other SYN proteins, implying the presence of structural features of the SYN1L2 protein.

Sodium Hexametaphosphate Serves as an Inducer of Calcium Signaling.

In bacteria, polymers of inorganic phosphates, particularly linear polyphosphate, are used as alternative phosphate donors for adenosine triphosphate production. A six-chain form of sodium metaphosphate, sodium hexametaphosphate (SHMP), is believed to have no physiological functions in mammalian cells. In this study, we explored the possible effects of SHMP on mammalian cells, using mouse oocytes, which are useful for observing various spatiotemporal intracellular changes. Fertilization-competent oocytes were isolated from the oviducts of superovulated mice and cultured in an SHMP-containing medium. In the absence of co-incubation with sperm, SHMP-treated oocytes frequently formed pronuclei and developed into two-cell embryos owing to the increase in calcium concentration in the cytoplasm. We discovered an intriguing role for SHMP as an initiator of calcium rise in mouse oocytes, presumably in a wide variety of mammalian cells.

Artificial oocyte activation using Ca2+ ionophores following intracytoplasmic sperm injection for low fertilization rate.

This large multi-center retrospective study examined whether artificial oocyte activation (AOA) using Ca2+ ionophore following ICSI improves the live birth rate for couples with previous ICSI cycles of unexplained low fertilization rate. In this large-scale multi-center retrospective study conducted in Japan, data were collected from Keio University and 17 collaborating institutions of the Japanese Institution for Standardizing Assisted Reproductive Technology. Between January 2015 and December 2019, 198 couples were included in this study. Oocytes for both the intervention and control groups were procured from the same pool of couples. Oocytes obtained from ICSI cycles with no or low fertilization rate (<50%) with unknown causes were included in the control (conventional ICSI) group while oocytes procured from ICSI cycles followed by performing AOA were assigned to the intervention (ICSI-AOA) group. Those fertilized with surgically retrieved sperm were excluded. ICSI-AOA efficacy and safety were evaluated by comparing these two groups. Live birth rate was the primary outcome. The ICSI-AOA group (2,920 oocytes) showed a significantly higher live birth per embryo transfer rate (18.0% [57/316]) compared to that of the conventional ICSI group with no or low fertilization rate (1,973 oocytes; 4.7% [4/85]) (odds ratio 4.5, 95% confidence interval 1.6-12.6; P<0.05). A higher live birth rate was observed in younger patients without a history of oocyte retrieval. Miscarriage, preterm delivery, and fetal congenital malformation rates were similar between the two groups. ICSI-AOA may reduce fertilization failure without increasing risks during the perinatal period. AOA may be offered to couples with an ICSI fertilization rate < 50%.

Morphometric assessment of blastocysts: relationship with the ongoing pregnancy rate.

Objective: To explore a morphometric grading system for blastocysts that is associated with ongoing pregnancy. Design: Cross-sectional study. Setting: None. Patientss: All consecutive vitrified blastocysts at our center from July 2018 to November 2021 that were transferred in single blastocyst transfer cycles until January 2022. Interventions: None. Main Outcome Measures: The ongoing pregnancy rate after a single vitrified-warmed blastocyst transfer. Interobserver agreement on morphometric values among embryologists. Results: Three morphometric variables (blastocyst diameter, area of inner cell mass [ICM], and the estimated trophectoderm cell count) were used to evaluate the expansion, ICM, and trophectoderm morphology. During the study period, 585 blastocysts were involved in this study. Of the 3 morphometric variables, ICM area (per 500 µm2, adjusted odds ratio, 1.19; 95% confidence interval, 1.09-1.30) and estimated trophectoderm cell count (per 10 cells, adjusted odds ratio, 1.25; 95% confidence interval, 1.12-1.39) were significantly associated with the ongoing pregnancy rate after adjustment for confounding factors. The ongoing pregnancy rate was 2.0% (1/49) with an ICM area of <2,500 µm2 and the estimated trophectoderm cell count <70. The ongoing pregnancy rate reached 47.8% (22/46) when the ICM area and the estimated trophectoderm cell count were >3,500 µm2 and >110, respectively. Interobserver agreement on the blastocyst diameter, ICM area, and the estimated trophectoderm cell count was excellent-to-good among 5 embryologists (intraclass correlation coefficients: 0.99, 0.87, and 0.91, respectively). Conclusions: Morphometric values of ICM and trophectoderm are promising predictors of pregnancy success. The high reproducibility suggests that the morphometric variables will contribute to identifying blastocysts with the highest developmental potential as well as those that will not result in a successful pregnancy.

Embryonic ß-Catenin Is Required for Priming of the Uterus to Implantation.

Repeated implantation failure is a major cause of infertility among healthy women. Uterine ß-catenin (CTNNB1) plays a critical role in implantation. However, the role of embryonic CTNNB1 during implantation remains unclear. We addressed this topic by analyzing mice carrying Ctnnb1-deficient (Ctnnb1Δ/Δ) embryos. Ctnnb1Δ/Δ embryos were produced by intercrossing mice bearing Ctnnb1-deficient eggs and sperms. We found that Ctnnb1Δ/Δ embryos developed to the blastocyst stage; thereafter, they were resorbed, leaving empty decidual capsules. Moreover, leukemia inhibitory factor, a uterine factor essential for implantation, was undetectable in Ctnnb1Δ/Δ blastocysts. Furthermore, CDX2, a transcription factor that determines the fate of trophectoderm cells, was not observed in Ctnnb1Δ/Δ blastocysts. Intrauterine injection with uterine fluids (from control mice) and recombinant mouse leukemia inhibitory factor proteins rescued the uterine response to Ctnnb1Δ/Δ blastocysts. These results suggest that embryonic CTNNB1 is required for the secretion of blastocyst-derived factor(s) that open the implantation window, indicating that the uterine response to implantation can be induced using supplemental materials. Therefore, our results may contribute to the discovery of a similar mechanism in humans, leading to a better understanding of the pathogenesis of repeated implantation failure.

Overdue Calcium Oscillation Causes Polyspermy but Possibly Permits Normal Development in Mouse Eggs.

In some non-mammalian eggs, the fusion of one egg and multiple sperm (polyspermy) induces a robust rise in intracellular calcium ion (Ca2+) concentration due to a shortage of inducers carried by a single sperm. Instead, one of the sperm nuclei is selected inside the egg for normal embryogenesis. Polyspermy also occurs during the in vitro fertilization of human eggs; however, the fate of such eggs is still under debate. Hence, the relationship between polyspermy and repetitive Ca2+ increases (Ca2+ oscillation) in mammals remains unknown. To address this issue, we used mouse sperm lacking extramitochondrial citrate synthase (eCS), which functions as a Ca2+ oscillation inducer; its lack causes retarded Ca2+ oscillation initiation (eCs-KO sperm). Elevated sperm concentrations normalize Ca2+ oscillation initiation. As expected, eCS deficiency enhanced polyspermy in both zona pellucida (ZP)-free and ZP-intact eggs despite producing the next generation of eCs-KO males. In conclusion, similarly to non-mammalian eggs, mouse eggs may develop normally under polyspermy conditions caused by problematic Ca2+ oscillation.

Trehalose Suppresses Lysosomal Anomalies in Supporting Cells of Oocytes and Maintains Female Fertility.

Supporting cells of oocytes, i.e., cumulus cells, control oocyte quality, which determines fertilization success. Therefore, the transformation of mature and immature cumulus cells (MCCs and ICCs, respectively) into dysmature cumulus cells (DCCs) with dead characteristics deteriorates oocyte quality. However, the molecular basis for this transformation remains unclear. Here, we explored the link between autophagic decline and cumulus transformation using cumulus cells from patients with infertility, female mice, and human granulosa cell-derived KGN cell lines. When human cumulus cells were labeled with LysoTracker probes, fluorescence corresponding to lysosomes was enhanced in DCCs compared to that in MCCs and ICCs. Similarly, treatment with the autophagy inhibitor chloroquine elevated LysoTracker fluorescence in both mouse cumulus cells and KGN cells, subsequently suppressing ovulation in female mice. Electron microscopy analysis revealed the proliferation of abnormal lysosomes in chloroquine-treated KGN cells. Conversely, the addition of an autophagy inducer, trehalose, suppressed chloroquine-driven problematic lysosomal anomalies and ameliorated ovulation problems. Our results suggest that autophagy maintains the healthy state of the supporting cells of human oocytes by suppressing the formation of lysosomes. Thus, our results provide insights into the therapeutic effects of trehalose on female fertility.

The possible effects of the Japan Society of Clinical Oncology Clinical Practice Guidelines 2017 on the practice of fertility preservation in female cancer patients in Japan.

Purpose: In 2017, the first guidelines for fertility preservation in cancer patients were published in Japan. However, the impact of the guidelines remains unknown. Therefore, the authors conducted a nationwide survey on cryopreservation procedures in the period from shortly before to after publication of the guidelines (2016-2019) and compared the results with our previous survey (2011-2015). The authors also surveyed reproductive specialists' awareness of the guidelines and implementation problems. Methods: The authors sent a questionnaire to 618 assisted reproductive technology facilities certified by the Japanese Society of Obstetrics and Gynecology. Results: The authors received responses from 395 institutions (63.8%). Among them, 144 institutions conducted cryopreservation for cancer patients (vs. 126 in 2011-2015) and performed 2537 embryo or oocyte and 178 ovarian tissue cryopreservation procedures (vs. 1085 and 122, respectively). Compared with the previous period, indications were more varied and protocols for controlled ovarian stimulation were more standardized. Reproductive specialists' interest in oncofertility was high, but many reported three main difficulties: selecting a treatment method, storing samples in the long term, and securing the necessary human resources. Conclusions: The practice of fertility preservation in cancer patients in Japan has been considerably affected by the first Japanese guidelines.

Identification of an antibacterial polypeptide in mouse seminal vesicle secretions.

In both men and women, pathogenic bacteria enter the reproductive tract and cause harmful symptoms. Intrauterine and oviductal inflammation after copulation may have severe effects, such as infertility, implantation failure, oviduct obstruction, and robust life-threatening bacterial infection. Human seminal plasma is considered to be protective against bacterial infection. Among its components, Semenogelin-I/-II proteins are digested to function as bactericidal factors; however, their sequences are not conserved in mammals. Therefore, alternative antibacterial (bactericidal and/or bacteriostatic) systems may exist across mammals. In this study, we examined the antibacterial activity in the seminal plasma of mice lacking a gene cluster encoding Semenogelin-I/-II counterparts. Even in the absence of the majority of seminal proteins, antibacterial activity remained in the seminal plasma. Moreover, a combination of gel chromatography and liquid chromatography coupled with tandem mass spectrometry revealed that the prostate and testis expressed 4 protein as a novel antibacterial (specifically, bacteriostatic) protein, the sequence of which is broadly conserved across mammals. Our results provide the first evidence of a bacteriostatic protein that is widely present in the mammalian seminal plasma.

Using piggyBac transposon gene expression vectors to transfect Zscan5b gene into mouse pluripotent stem cells.

We recently demonstrated that the zygotic gene Zscan5b is involved in maintaining the genomic integrity of pluripotent stem cells (PSCs) during mitosis and that Zscan5b gene expression can prevent chromosomal abnormalities. Here, we provide a detailed protocol for the transfection of mouse embryonic stem cells (mESCs) and mouse-induced PSCs (miPSCs) with a Zscan5b constitutive expression plasmid, using the piggyBac transposon gene expression vector system. For complete details on the use and execution of this protocol, please refer to Ogawa et al. (2019).

Mitochondrial replacement by genome transfer in human oocytes: Efficacy, concerns, and legality.

BACKGROUND: Pathogenic mitochondrial (mt)DNA mutations, which often cause life-threatening disorders, are maternally inherited via the cytoplasm of oocytes. Mitochondrial replacement therapy (MRT) is expected to prevent second-generation transmission of mtDNA mutations. However, MRT may affect the function of respiratory chain complexes comprised of both nuclear and mitochondrial proteins. METHODS: Based on the literature and current regulatory guidelines (especially in Japan), we analyzed and reviewed the recent developments in human models of MRT. MAIN FINDINGS: MRT does not compromise pre-implantation development or stem cell isolation. Mitochondrial function in stem cells after MRT is also normal. Although mtDNA carryover is usually less than 0.5%, even low levels of heteroplasmy can affect the stability of the mtDNA genotype, and directional or stochastic mtDNA drift occurs in a subset of stem cell lines (mtDNA genetic drift). MRT could prevent serious genetic disorders from being passed on to the offspring. However, it should be noted that this technique currently poses significant risks for use in embryos designed for implantation. CONCLUSION: The maternal genome is fundamentally compatible with different mitochondrial genotypes, and vertical inheritance is not required for normal mitochondrial function. Unresolved questions regarding mtDNA genetic drift can be addressed by basic research using MRT.

Suppression of Non-Random Fertilization by MHC Class I Antigens.

Hermaphroditic invertebrates and plants have a self-recognition system on the cell surface of sperm and eggs, which prevents their self-fusion and enhances non-self-fusion, thereby contributing to genetic variation. However, the system of sperm-egg recognition in mammals is under debate. To address this issue, we explored the role of major histocompatibility complex class I (MHC class I, also known as histocompatibility 2-Kb or H2-Kb and H2-Db in mice) antigens by analyzing H2-Kb-/-H2-Db-/-ß2-microglobulin (ß2M)-/- triple-knockout (T-KO) male mice with full fertility. T-KO sperm exhibited an increased sperm number in the perivitelline space of wild-type (WT) eggs in vitro. Moreover, T-KO sperm showed multiple fusion with zona pellucida (ZP)-free WT eggs, implying that the ability of polyspermy block for sperm from T-KO males was weakened in WT eggs. When T-KO male mice were intercrossed with WT female mice, the percentage of females in progeny increased. We speculate that WT eggs prefer fusion with T-KO sperm, more specifically X-chromosome-bearing sperm (X sperm), suggesting the presence of preferential (non-random) fertilization in mammals, including humans.

Mitochondrial Genetic Drift after Nuclear Transfer in Oocytes.

Mitochondria are energy-producing intracellular organelles containing their own genetic material in the form of mitochondrial DNA (mtDNA), which codes for proteins and RNAs essential for mitochondrial function. Some mtDNA mutations can cause mitochondria-related diseases. Mitochondrial diseases are a heterogeneous group of inherited disorders with no cure, in which mutated mtDNA is passed from mothers to offspring via maternal egg cytoplasm. Mitochondrial replacement (MR) is a genome transfer technology in which mtDNA carrying disease-related mutations is replaced by presumably disease-free mtDNA. This therapy aims at preventing the transmission of known disease-causing mitochondria to the next generation. Here, a proof of concept for the specific removal or editing of mtDNA disease-related mutations by genome editing is introduced. Although the amount of mtDNA carryover introduced into human oocytes during nuclear transfer is low, the safety of mtDNA heteroplasmy remains a concern. This is particularly true regarding donor-recipient mtDNA mismatch (mtDNA-mtDNA), mtDNA-nuclear DNA (nDNA) mismatch caused by mixing recipient nDNA with donor mtDNA, and mtDNA replicative segregation. These conditions can lead to mtDNA genetic drift and reversion to the original genotype. In this review, we address the current state of knowledge regarding nuclear transplantation for preventing the inheritance of mitochondrial diseases.

Analysis of 122 triplet and one quadruplet pregnancies after single embryo transfer in Japan.

RESEARCH QUESTION: What is the prevalence of triplet and quadruplet pregnancies after single embryo transfer (SET) in Japan. DESIGN: A retrospective observational study was conducted on 274,605 pregnancies after 937,848 SET cycles in registered assisted reproductive technology (ART) data from the Japanese ART national registry database between 2007 and 2014. A questionnaire survey of ART centres was also conducted. Data on pregnancies with embryo division into three or more after SET were analysed. RESULTS: According to the Japanese ART national registry database, SET resulted in 109 triplet pregnancies (0.04% of pregnancies), and the questionnaire reports from 31 centres revealed 33 triplet and one quadruplet pregnancies. After exclusion of 20 duplicated cases, 122 triplet and one quadruplet pregnancies included 46 monochorionic (one gestational sac [37.4%]), 18 dichorionic (two gestational sacs [14.6%]) and 59 trichorionic pregnancies (three gestational sacs [48.0%]). Compared with singleton pregnancies, patients with monozygotic triplet or quadruplet pregnancies were less frequently diagnosed with unexplained infertility (P = 0.004), more often received gonadotrophin injections for ovarian stimulation in 39 cases with information available (P = 0.021) and underwent more blastocyst transfers and assisted hatching (P = 0.002 and P < 0.001, respectively). The proportion of live birth, defined as at least one baby born, excluding induced abortion, was 64.6% (73/116 pregnancies) of monozygotic triplet or quadruplet pregnancies. CONCLUSIONS: Combined Japanese ART national registry and survey data revealed 122 triplet and one quadruplet pregnancies, the majority after cryopreserved embryo transfer. Most were conceived after blastocyst transfer and often after assisted hatching, which are potential risk factors for zygotic splitting.

Zscan5b Deficiency Impairs DNA Damage Response and Causes Chromosomal Aberrations during Mitosis.

Zygotic genome activation (ZGA) begins after fertilization and is essential for establishing pluripotency and genome stability. However, it is unclear how ZGA genes prevent mitotic errors. Here we show that knockout of the ZGA gene Zscan5b, which encodes a SCAN domain with C2H2 zinc fingers, causes a high incidence of chromosomal abnormalities in embryonic stem cells (ESCs), and leads to the development of early-stage cancers. After irradiation, Zscan5b-deficient ESCs displayed significantly increased levels of γ-H2AX despite increased expression of the DNA repair genes Rad51l3 and Bard. Re-expression of Zscan5b reduced γ-H2AX content, implying a role for Zscan5b in DNA damage repair processes. A co-immunoprecipitation analysis showed that Zscan5b bound to the linker histone H1, suggesting that Zscan5b may protect chromosomal architecture. Our report demonstrates that the ZGA gene Zscan5b is involved in genomic integrity and acts to promote DNA damage repair and regulate chromatin dynamics during mitosis.