Journal of Reproduction and Development
Online ISSN : 1348-4400
Print ISSN : 0916-8818
ISSN-L : 0916-8818
Current issue
Displaying 1-12 of 12 articles from this issue
SRD Outstanding Research Award 2021
  • Fugaku AOKI
    Article type: SRD Outstanding Research Award 2021
    2022 Volume 68 Issue 2 Pages 79-84
    Published: 2022
    Released on J-STAGE: April 01, 2022
    Advance online publication: January 15, 2022
    JOURNAL OPEN ACCESS

    The zygotic genome is transcriptionally silent immediately after fertilization. In mice, initial activation of the zygotic genome occurs in the middle of the one-cell stage. At the mid-to-late two-cell stage, a burst of gene activation occurs after the second round of DNA replication, and the profile of transcribed genes changes dramatically. These two phases of gene activation are called minor and major zygotic gene activation (ZGA), respectively. As they mark the beginning of the gene expression program, it is important to elucidate gene expression regulation during these stages. This article reviews the outcomes of studies that have clarified the profiles and regulatory mechanisms of ZGA.

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SRD Young Investigator Award 2021
  • Natsumi ENDO
    Article type: SRD Young Investigator Award
    2022 Volume 68 Issue 2 Pages 85-89
    Published: 2022
    Released on J-STAGE: April 01, 2022
    Advance online publication: February 12, 2022
    JOURNAL OPEN ACCESS

    The reproductive performance of dairy cows has declined, along with an increase in their milk yield. First-service conception rates in lactating dairy cows are often lower than 50%. The precise detection of estrus is an important factor in the reproductive management of dairy cows for successful fertilization and pregnancy. However, estrus expression has been decreasing in modern dairy cows, affecting the detection rate of estrus. In addition to estrus, a high incidence of ovulation disorders affects the fertility of dairy cows. To address these problems, it is necessary to understand the changes in the endocrine functions that underlie estrus and ovulation disorders, and to develop effective treatment strategies. Recent studies have revealed that neurokinin B and neurokinin 3 receptor signaling play important roles in the regulation of the secretion of gonadotropin-releasing and luteinizing hormones, suggesting a potential clinical avenue for the stimulation of gonadal function. In this review, I have discussed the problems in estrus and ovulation disorders in modern dairy cows as well as the possible applications of neurokinin 3 receptor agonists in the treatment of these disorders.

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Review
  • Miki SAKATANI
    Article type: Review
    2022 Volume 68 Issue 2 Pages 90-95
    Published: 2022
    Released on J-STAGE: April 01, 2022
    Advance online publication: January 30, 2022
    JOURNAL OPEN ACCESS

    The livestock industry produces a large amount of greenhouse gases (GHG) that cause global warming. A high percentage of GHG emissions are derived from cattle and has been suggested to be a factor in global warming. With the global increase in the consumption of livestock products, the number of farm animals has increased. In addition, the reduction in productivity and reproductive capacity of cattle has resulted in accelerated GHG emissions. In a high-temperature environment, the pregnancy rate decreases, leading to an increase in animals that do not contribute to production. Consequently, GHG emission per unit product increases, thereby accelerating global warming. To reduce this environmental impact, it is important to improve the breeding efficiency of cattle by the use of reproductive technology and, thus, reduce the number of non-productive animals. Thus, reproductive biology plays a major role in mitigating global warming related to the livestock industry.

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  • Yasuhisa MATSUI, Yohei HAYASHI
    Article type: Review
    2022 Volume 68 Issue 2 Pages 96-103
    Published: 2022
    Released on J-STAGE: April 01, 2022
    Advance online publication: December 25, 2021
    JOURNAL OPEN ACCESS

    Metabolism is an important cellular process necessary not only for producing energy and building blocks for cells, but also for regulating various cell functions, including intracellular signaling, epigenomic effects, and transcription. The regulatory roles of metabolism have been extensively studied in somatic cells, including stem cells and cancer cells, but data regarding germ cells are limited. Because germ cells produce individuals of subsequent generations, understanding the role of metabolism and its regulatory functions in germ cells is important. Although limited information concerning the specific role of metabolism in germ cells is available, recent advances in related research have revealed specific metabolic states of undifferentiated germ cells in embryos as well as in germ cells undergoing oogenesis and spermatogenesis. Studies have also elucidated the functions of some metabolic pathways associated with germ cell development and the non-genomic heritable machinery of germ cells. In this review, we summarized all the available knowledge on the characteristic metabolic pathways in germ cells, focusing on their regulatory functions, while discussing the issues that need to be addressed to enhance the understanding of germ cell metabolism.

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  • Fernando LÓPEZ-GATIUS
    Article type: Review
    2022 Volume 68 Issue 2 Pages 104-109
    Published: 2022
    Released on J-STAGE: April 01, 2022
    Advance online publication: December 30, 2021
    JOURNAL OPEN ACCESS

    Prostaglandin F (PGF) and its analogs are used to induce luteolysis in estrus synchronization programs to terminate unwanted pregnancies or to promote ovulation in certain cow subpopulations. In the past few decades, the luteolytic dose of PGF has remained unchanged. This review explores the clinical implications of increasing the standard dose for these applications in high-producing dairy cows. Ultrasonography may assist in selecting the most appropriate PGF dose and improve the results. A reference has been used for PGF for promoting ovulation in herds showing poor reproductive performance.

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Original Article
  • Ayami YAMADA, Kaito OHTSUKI, Natsumi SHIGA, Jonathan A. GREEN, Yuta MA ...
    Article type: Original Article
    2022 Volume 68 Issue 2 Pages 110-117
    Published: 2022
    Released on J-STAGE: April 01, 2022
    Advance online publication: January 03, 2022
    JOURNAL OPEN ACCESS

    Epithelial-mesenchymal transition (EMT), which is common in cancer metastasis, is also observed during developmental processes such as embryo implantation into the maternal endometrium in humans and rodents. However, this process has not been well characterized in the non-invasive type of implantation that occurs in ruminants. To understand whether EMT occurs in ruminant ungulates, ovine conceptuses (embryo plus extraembryonic membranes) from days 15 (P15: pre-attachment), 17 (P17: during attachment), and 21 (P21: post-attachment, day 0 = day of estrus) were evaluated. RNA-seq analysis revealed that the expression of EMT-related transcripts increased on P21. Real-time PCR and western blotting analyses indicated that levels of transcripts and proteins indicative of mesenchyme-related molecules increased on P21, but a minor expression of epithelium-related molecules remained. Immunohistochemical analysis revealed that E-cadherin (CDH1) was localized in the elongated trophectoderm on P15 and P17. On P21, CDH1 was localized to the trophectoderm and on the conceptus cells undergoing differentiation. Vimentin (VIM) was localized in the uterine stroma on P15 and P17, and its expression was observed at the edge of elongating trophoblast on P21. Further, it was found that some bi-nucleated trophoblast cells were present on P17; however, numerous bi- and multi-nucleated trophoblast cells on the uterine epithelium or next to the uterine stroma were found on P21. A minor expression of pregnancy-associated glycoprotein (PAG) transcripts was found on P15 and P17, but a definitive expression of PAGs, transcripts, and proteins was found on P21. Although further investigation is required, these observations indicate that bi-nucleated trophoblast cell formation begins on the day conceptus implantation to the maternal endometrium is initiated, followed by EMT in trophoblast cells. These results suggest that these sequential events are required if pregnancy is to be established in ruminants.

    Editor's pick

    Cover Story:
    To understand the cellular processes associated with non-invasive mode of conceptus implantation to the maternal endometrium, Yamada
    et al. observed the conceptus implantation process via adhesion of trophoblast cells to the uterine epithelium (Yamada et al., Epithelial-mesenchymal transition and bi- and multi-nucleated trophoblast cell formation in ovine conceptuses during the peri-implantation period, pp. 110–117). Similar to human syncytiotrophoblast, ruminant trophoblasts form bi- and multi-nucleated trophoblast cells. Using pregnancy associated glycoproteins (PAGs) specific antibody, bi- and multi-nucleated trophoblast cells in cross sections of day 21 ovine uteri (day 0 = day of estrus), including elongated conceptuses, were observed, and it was found that bi- and multi-nucleated trophoblast cells existed on the uterine epithelium or next to the uterine stroma. These results suggest that the formation of bi- and multi-nucleated trophoblast cells facilitates the placental formation in ruminants.

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  • Erika HAYASHI, Sayaka WAKAYAMA, Daiyu ITO, Ayumi HASEGAWA, Keiji MOCHI ...
    Article type: Original Article
    2022 Volume 68 Issue 2 Pages 118-124
    Published: 2022
    Released on J-STAGE: April 01, 2022
    Advance online publication: January 04, 2022
    JOURNAL OPEN ACCESS

    Mammalian embryos are most commonly cryopreserved in liquid nitrogen; however, liquid nitrogen is not available in special environments, such as the International Space Station (ISS), and vitrified embryos must be stored at −80°C. Recently, the high osmolarity vitrification (HOV) method was developed to cryopreserve mouse 2-cell stage embryos at −80°C; however, the appropriate embryo is currently unknown. In this study, we compared the vitrification resistance of in vivo-derived, in vitro fertilization (IVF)-derived, and intracytoplasmic sperm injection (ICSI)-derived mouse 2-cell embryos against cryopreservation at −80°C. The ICSI embryos had lower survival rates after warming and significantly lower developmental rates than the in vivo and IVF embryos. Further, IVF embryos had a lower survival rate after warming, but a similar rate to the in vivo embryos to full-term development. This result was confirmed by simultaneous vitrification of in vivo and IVF embryos in the same cryotube using identifiable green fluorescent protein-expressing embryos. We also evaluated the collection timing of the in vivo embryos from the oviduct and found that late 2-cell embryos had higher survival and developmental rates to full-term than early 2-cell embryos. Some early 2-cell embryos remained in the S-phase, whereas most late 2-cell embryos were in the G2-phase, which may have affected the tolerance to embryo vitrification. In conclusion, when embryos must be cryopreserved under restricted conditions, such as the ISS, in vivo fertilized embryos collected at the late 2-cell stage without long culture should be employed.

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  • Shinya IKEDA, Koki TANAKA, Reiko OHTANI, Akifumi KANDA, Yusuke SOTOMAR ...
    Article type: Original Article
    2022 Volume 68 Issue 2 Pages 125-136
    Published: 2022
    Released on J-STAGE: April 01, 2022
    Advance online publication: January 30, 2022
    JOURNAL OPEN ACCESS
    Supplementary material

    In the male germline, the machinery to repress retrotransposons that threaten genomic integrity via the piRNA pathway is established in gonocytes. It has been reported that disruption of the piRNA pathway leads to activation of retrotransposons and arrests spermatogenesis before it enters the second meiosis; however, its effects on gonocytes have not been fully elucidated. In this study, we analyzed the effects of Asz1 deletion, which is a crucial component of the piRNA pathway, on the gonocyte transcriptome. In Asz1-null gonocytes, MIWI2, which is responsible for introducing DNA methylation to retrotransposons in a piRNA-dependent manner, disappeared from the nuclei of fetal gonocytes. Transcriptome analysis revealed that retrotransposons targeted by the piRNA pathway and non-annotated transcript variants were upregulated in gonocytes from neonatal Asz1-/- mice. These non-annotated transcript variants were chimeras generated by joining exons transcribed from retrotransposons and canonical genes. DNA methylation analysis showed that retrotransposons that induce the expression of aberrant chimeric transcripts are not fully methylated. This was consistent with the impaired nuclear localization of MIWI2 in Asz1-null gonocytes. Furthermore, heterogeneity of DNA methylation status in retrotransposons was observed in both gonocytes and their descendants. This suggests that the piRNA system in gonocytes can potentially prevent spermatogenic cell populations bearing aberrant chimeric transcripts from propagating later in spermatogenesis. In conclusion, Asz1 is required to repress retrotransposons and retrotransposon-driven aberrant chimeric transcripts in gonocytes through the piRNA pathway.

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  • Chihiro EMORI, Takuya KANKE, Haruka ITO, Yuki AKIMOTO, Wataru FUJII, K ...
    Article type: Original Article
    2022 Volume 68 Issue 2 Pages 137-143
    Published: 2022
    Released on J-STAGE: April 01, 2022
    Advance online publication: January 18, 2022
    JOURNAL OPEN ACCESS

    The cooperative effects of estrogen and oocyte-derived paracrine factors (ODPFs) play critical roles in the normal development of ovarian follicles; however, the mechanism underlying this cooperation has not been well studied. The present study aimed to determine whether ODPFs affect estrogen signaling by regulating the expression of estrogen receptor (ESR) and its coregulators in mouse granulosa cells. Some transcripts encoding ESR coregulators were differentially expressed between cumulus and mural granulosa cells (MGCs). The transcript levels of ESR coregulators, including nuclear receptor corepressor 1 and activator 2, in cumulus cells were significantly suppressed by ODPFs; however, they increased when cumulus cell-oocyte complexes were treated with the transforming growth factor beta receptor I inhibitor, SB431542. Moreover, MGCs exhibited significantly higher ESR2 protein and transcript levels than those in cumulus cells. ODPFs promoted Esr2 expression in cumulus cells but had no effect on that in MGCs. Overall, regulation of the expression of ESR2 and its coregulators in cumulus cells by oocytes seems to be one of the mechanisms underlying estrogen-oocyte cooperation in well-developed antral follicles in mice.

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  • Kohei KAWANO, Yojiro YANAGAWA, Masashi NAGANO, Seiji KATAGIRI
    Article type: Original Article
    2022 Volume 68 Issue 2 Pages 144-151
    Published: 2022
    Released on J-STAGE: April 01, 2022
    Advance online publication: January 28, 2022
    JOURNAL OPEN ACCESS
    Supplementary material

    The endometrial epidermal growth factor (EGF) profile is an indicator of uterine function and fertility in cattle. The present study aimed to investigate the effects of heat stress on the endometrial EGF profile and fertility in lactating Holstein cows. The endometrial EGF profiles of 365 cows in the Hokkaido and Kyushu regions were examined between June and September (heat stress period, n = 211) and between October and January (control period, n = 154). EGF profiles were investigated using uterine endometrial tissues obtained by biopsy 3 days after estrus (Day 3). The proportion of cows with an altered EGF profile was higher between June and September than between October and January (41.2 vs. 16.2%, P < 0.05). The effects of rectal temperature on Days 0 and 3 on the endometrial EGF profile were also assessed in cows (n = 79) between June and September in the Kyushu region. A single embryo was transferred to cow on Day 7 to evaluate fertility (n = 67). Regardless of the rectal temperature on Day 3, the proportion of cows with an altered EGF profile was higher (64.1 vs. 30.0%, P < 0.05) and the pregnancy rate after embryo transfer (ET) was lower (26.7 vs. 51.4%, P < 0.05) in cows with a rectal temperature ≥ 39.5°C on Day 0 than in cows with a rectal temperature < 39.5°C on Day 0. The present results indicate that alterations in the endometrial EGF profile induced by an elevated body temperature on Day 0 contributed to reductions in fertility in lactating dairy cows during the heat stress period.

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  • Dimas Arya ABDILLAH, Onalenna KEREILWE, Raihana Nasrin FERDOUSY, Risa ...
    Article type: Original Article
    2022 Volume 68 Issue 2 Pages 152-159
    Published: 2022
    Released on J-STAGE: April 01, 2022
    Advance online publication: January 27, 2022
    JOURNAL OPEN ACCESS
    Supplementary material

    Coronavirus disease (COVID-19), the ongoing global pandemic, is caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Recent evidence shows that the virus utilizes angiotensin-converting enzyme 2 (ACE2) as a spike protein receptor for entry into target host cells. The bovine ACE2 contains key residues for binding to the spike protein receptor-binding domain. This study evaluated the hypothesis that bovine gonadotroph expresses ACE2, and spike protein suppresses luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion from cultured bovine anterior pituitary (AP) cells. ACE2 mRNA expression and ACE2 protein expression were detected in the bovine AP cells using reverse transcription PCR and western blot analysis. Immunofluorescence microscopy analysis with the anti-ACE2 antibody revealed the co-localization of ACE2 and gonadotropin-releasing hormone (GnRH) receptor on the gonadotroph plasma membrane. Approximately 90% of GnRH receptor-positive cells expressed ACE2, and approximately 46% of ACE2-positive cells expressed the GnRH receptor. We cultured bovine AP cells for 3.5 days and treated them with increasing concentrations (0, 0.07, 0.7, or 7 pM) of recombinant spike protein having both S1 and S2 regions. The spike protein (0.07–7 pM) suppressed both basal and GnRH-induced LH secretion (P < 0.05). Spike protein (0.7–7 pM) suppressed GnRH-induced (P < 0.05), but not basal FSH secretion. In contrast, pre-treatment with ERK 1/2/5 inhibitor (U0126) partially restored the GnRH-induced LH and FSH secretion from the spike protein suppression. Collectively, the results indicate that gonadotrophs express ACE2, a receptor for coronavirus 2 spike protein, which in turn suppresses LH and FSH secretion from AP cells.

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Technology Report
  • Takumi YOSHIDA, Md Emtiaj ALAM, Keisuke HANAFUSA, Yasunori TSUJIMOTO, ...
    Article type: Technology Report
    2022 Volume 68 Issue 2 Pages 160-164
    Published: 2022
    Released on J-STAGE: April 01, 2022
    Advance online publication: January 07, 2022
    JOURNAL OPEN ACCESS
    Supplementary material

    We examined the effectiveness of saline, Euro-Collins solution (EC), and ET-Kyoto solution (ET-K) as preservation media for the cold storage of feline ovaries. Ovaries were maintained in these media at 4°C for 24, 48, or 72 h until oocyte retrieval. The ET-K group exhibited a higher oocyte maturation rate than the saline group after 72 h of storage. Moreover, ET-K could sustain the competence of the feline oocytes to cleave after 48 h, and the morula formation rate of the ET-K group was higher than that of the other groups after 24 and 48 h. Furthermore, the ET-K group exhibited a higher blastocyst formation rate than the other groups after storage for 24 h, and only ET-K retained the developmental competence in blastocysts after 48 h of storage. In addition, regarding the cell numbers of the blastocysts, there was no significant difference among the tested groups. In conclusion, our results indicate that ET-K is a suitable preservation medium for feline ovaries.

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