Prostaglandin E2 stimulates the expression of cumulus expansion-related genes in pigs: the role of protein kinase B

Single-cell and spatiotemporal profile of ovulation in the mouse ovary

Ovulation is a spatiotemporally coordinated process that involves several tightly controlled events, including oocyte meiotic maturation, cumulus expansion, follicle wall rupture and repair, and ovarian stroma remodeling. To date, no studies have detailed the precise window of ovulation at single-cell resolution. Here, we performed parallel single-cell RNA-seq and spatial transcriptomics on paired mouse ovaries across an ovulation time course to map the spatiotemporal profile of ovarian cell types. We show that major ovarian cell types exhibit time-dependent transcriptional states enriched for distinct functions and have specific localization profiles within the ovary. We also identified gene markers for ovulation-dependent cell states and validated these using orthogonal methods. Finally, we performed cell-cell interaction analyses to identify ligand-receptor pairs that may drive ovulation, revealing previously unappreciated interactions. Taken together, our data provides a rich and comprehensive resource of murine ovulation that can be mined for discovery by the scientific community.

An Update on Physiopathological Roles of Akt in the ReprodAKTive Mammalian Ovary

The phosphoinositide 3-kinase (PI3K)/Akt pathway is a key signaling cascade responsible for the regulation of cell survival, proliferation, and metabolism in the ovarian microenvironment. The optimal finetuning of this pathway is essential for physiological processes concerning oogenesis, folliculogenesis, oocyte maturation, and embryo development. The dysregulation of PI3K/Akt can impair molecular and structural mechanisms that will lead to follicle atresia, or the inability of embryos to reach later stages of development. Due to its pivotal role in the control of cell proliferation, apoptosis, and survival mechanisms, the dysregulation of this molecular pathway can trigger the onset of pathological conditions. Among these, we will focus on diseases that can harm female fertility, such as polycystic ovary syndrome and premature ovarian failure, or women's general health, such as ovarian cancer. In this review, we report the functions of the PI3K/Akt pathway in both its physiological and pathological roles, and we address the existing application of inhibitors and activators for the balancing of the molecular cascade in ovarian pathological environments.

The effect of L-carnitine on oocyte mitochondrial health and biomarkers on cyclophosphamide chemotherapy drug in mice

Improving oocyte competence during chemotherapy is widely known as a contributing factor to increasing the probability of fertility. Additionally, the role of cumulus cells in oocyte quality is of utmost importance. Therefore, this study was designed to simultaneously probe into the relative gene expression of oocytes and cumulus cells as biomarkers of oocyte quality with cyclophosphamide and L-carnitine treatment. A total of 60 adult NMRI mice were divided into four groups: control, L-carnitine (LC), cyclophosphamide (CP), and cyclophosphamide+L-carnitine (CP+LC). The relative mRNA expression levels of oocyte quality genes including growth differentiation factor 9 (Gdf9), hyaluronan synthase 2 (Has2), and mitochondrial sirtuin 3 (Sirt3) in oocytes, and genes involved in bilateral communication between cumulus cells and between the oocyte and its neighboring cumulus cells including connexin 37 (Cx37) and connexin 43 (Cx43) were detected by Real-time-PCR. DCFH-DA staining analyzed the level of intracellular ROS in oocytes. Under the influence of L-carnitine, Gdf9, Has2, Cx43, and Cx37 were significantly up-regulated (p ≤ 0.05). However, cyclophosphamide considerably reduced the expression of all these genes (p ≤ 0.05). The expression of the Sirt3 gene in the CP group increased significantly compared to the other groups (p ≤ 0.05). Analysis of fluorescent images revealed that the level of intracellular ROS in the cyclophosphamide group was significantly increased compared to the other groups (p ≤ 0.05), while it plummeted in the L-carnitine group (p ≤ 0.05). L-carnitine as an antioxidant can reduce the destructive effects of cyclophosphamide and enhance bilateral communications between oocytes and cumulus cells, and it may ultimately lead to an increase in the fertility rate.

A Role of PI3K/Akt Signaling in Oocyte Maturation and Early Embryo Development

A serine/threonine-specific protein kinase B (PKB), also known as Akt, is a key factor in the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway that regulates cell survival, metabolism and proliferation. Akt phosphorylates many downstream specific substrates, which subsequently control the nuclear envelope breakdown (NEBD), centrosome maturation, spindle assembly, chromosome segregation, and cytokinesis. In vertebrates, Akt is also an important player during oogenesis and preimplantation development. In the signaling pathways regulating mRNA translation, Akt is involved in the control of mammalian target of rapamycin complex 1 (mTORC1) and thereby regulates the activity of a translational repressor, the eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1). In this review, we summarize the functions of Akt in mitosis, meiosis and early embryonic development. Additionally, the role of Akt in the regulation of mRNA translation is addressed with respect to the significance of this process during early development.

Sequential IVM by CNP preincubation and cooperating of PGE2 with AREG enhances developmental competence of SCNT reconstructs in goat

Developmental competence of in vitro matured cumulus oocyte complexes (COCs) in conventional IVM (C.IVM) is lower than in vivo maturated COCs and is related to unsynchronized nuclear and cytoplasmic maturation. To overcome this dearth, COCs can be exposed to granulosa secreted factors in a two-step system. Therefore, in the first experiment, 1000 nM of C-type natriuretic peptide for 8 h was determined (CAPA), as the best time and concentration to retain oocytes in germinal vesicle stage. This condition, also reduces lipid droplets and increases the expression of ATGL and PLIN2 involved in lipolysis and lipogenesis, respectively. In the second experiment, maturation was stimulated with prostaglandin E2 and amphiregulin for 18 h (CAPA-IVM), and their optimal concentrations based on blastocyst formation rates through in vitro fertilization (IVF) were determined as 1 and 600 nM, respectively. In the third experiment, the in vitro and in vivo developmental competency of SCNT embryos in CAPA-IVM group were determined. Despite similar blastocyst formation rates in IVF and SCNT between CAPA-IVM and C.IVM, the quality of blastocysts were quality was higher in CAPA-IVM, which reflected itself, as higher ICM/TE ratio and also expression of NANOG in SCNT blastocysts. Pregnancy rate, live births rate and SCNT efficiency were not significant between CAPA-IVM and C.IVM groups. Therefore, CAPA-IVM can improve the developmental competency of SCNT derived embryos.

The Role of MAPK3/1 and AKT in the Acquisition of High Meiotic and Developmental Competence of Porcine Oocytes Cultured In Vitro in FLI Medium

The developmental potential of porcine oocytes cultured in vitro was remarkably enhanced in a medium containing FGF2, LIF and IGF1 (FLI) when compared to a medium supplemented with gonadotropins and EGF (control). We analyzed the molecular background of the enhanced oocyte quality by comparing the time course of MAPK3/1 and AKT activation, and the expression of genes controlled by these kinases in cumulus-oocyte complexes (COCs) cultured in FLI and the control medium. The pattern of MAPK3/1 activation in COCs was very similar in both media, except for a robust increase in MAPK3/1 phosphorylation during the first hour of culture in the FLI medium. The COCs cultured in the FLI medium exhibited significantly higher activity of AKT than in the control medium from the beginning up to 16 h of culture; afterwards a deregulation of AKT activity occurred in the FLI medium, which was not observed in the control medium. The expression of cumulus cell genes controlled by both kinases was also modulated in the FLI medium, and in particular the genes related to cumulus-expansion, signaling, apoptosis, antioxidants, cell-to-cell communication, proliferation, and translation were significantly overexpressed. Collectively, these data indicate that both MAPK3/1 and AKT are implicated in the enhanced quality of oocytes cultured in FLI medium.

The Function of Cumulus Cells in Oocyte Growth and Maturation and in Subsequent Ovulation and Fertilization

Cumulus cells (CCs) originating from undifferentiated granulosa cells (GCs) differentiate in mural granulosa cells (MGCs) and CCs during antrum formation in the follicle by the distribution of location. CCs are supporting cells of the oocyte that protect the oocyte from the microenvironment, which helps oocyte growth and maturation in the follicles. Bi-directional communications between an oocyte and CCs are necessary for the oocyte for the acquisition of maturation and early embryonic developmental competence following fertilization. Follicle-stimulation hormone (FSH) and luteinizing hormone (LH) surges lead to the synthesis of an extracellular matrix in CCs, and CCs undergo expansion to assist meiotic resumption of the oocyte. The function of CCs is involved in the completion of oocyte meiotic maturation and ovulation, fertilization, and subsequent early embryo development. Therefore, understanding the function of CCs during follicular development may be helpful for predicting oocyte quality and subsequent embryonic development competence, as well as pregnancy outcomes in the field of reproductive medicine and assisted reproductive technology (ART) for infertility treatment.

In vitro maturation using an agarose matrix with incorporated extracellular matrix proteins improves porcine oocyte developmental competence by enhancing cytoplasmic maturation

Here, we present a novel in vitro maturation (IVM) system comprising an agarose matrix supplemented with extracellular matrix (ECM) proteins for enhanced maturation of immature oocytes within cumulus-oocyte complexes (COCs) derived from porcine medium antral follicles (MAFs). Immunocytochemical analyses of integrin subunit α₂ , α₅ , α₆ , β₁ , and β₄ expression suggested that integrin α₂ β₁ , α₅ β₁ , α₆ β₁ , and α₆ β₄ play pivotal roles in IVM of porcine immature oocytes. Combinatorial supplementation of fibronectin interacting with integrin α₅ β₁ , collagen interacting with integrin α₂ β₁ , and laminin interacting with integrin α₆ β₁ and α₆ β₄ to the agarose matrix had no significant effect on nuclear maturation. However, the number of parthenogenetic embryos that developed into blastocysts increased when oocytes were matured using agarose IVM matrices supplemented with fibronectin, collagen, or laminin. Furthermore, significant increases in cytoplasmic maturation-related parameters (BMP15 level, cumulus cell expansion score, intra-oocyte ATP level, and index of cortical granule distribution) were observed in COCs matured in vitro using ECM protein-incorporated agarose matrices. Our data suggest that mature porcine oocytes with enhanced developmental competence and high-quality cytoplasm can be generated via IVM using agarose matrices supplemented with fibronectin, collagen, or laminin.

Molecular characteristics of oocytes and somatic cells of follicles at different sizes that influence in vitro oocyte maturation and embryo production

During the last 10 to 15 yr, in vitro research to predict antral follicle growth and oocyte maturation has delivered interesting advances in the knowledge of processes regulating follicle growth and developmental competence of oocytes. This review discusses the contribution of cumulus and mural granulosa cells in the process of oocyte maturation and cumulus expansion in cumulus-oocyte complexes (COCs) from follicles of different sizes and shows that differences in gene expression in oocytes, granulosa, and theca cells of small and large follicles impact the success of in vitro blastocyst development. In addition, the molecular mechanisms by which COC metabolism and antioxidant defense provide oocyte competence are highlighted. Furthermore, new insights and perspectives on molecular and cellular regulation of in vitro oocyte maturation are emphasized.

Estrogen improves the development of yak (Bos grunniens) oocytes by targeting cumulus expansion and levels of oocyte-secreted factors during in vitro maturation

The estrogen-signalling pathway is critical for normal follicular development; however, little is known about its importance during in vitro maturation (IVM) in large animals, particularly yaks (Bos grunniens). Through the present study, we aimed to determine the mechanisms underlying estrogen involvement in cumulus expansion and the subsequent development of cumulus-oocyte complexes (COCs). COCs were cultured in the maturation medium supplemented with different concentrations (10⁻⁶–10⁻³ mM) of 17β-estradiol (E2) or its receptor antagonist, fulvestrant, and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and western blot were performed to determine the expression of cumulus-expansion related factors and oocyte-secreted factors (OSFs). The cumulus expansion of COCs was observed using an inverted microscope, and COCs developmental ability were judged by the evaluation of cleavage and blastulation rates per inseminated oocytes by IVF, and the number of cells in the blastocyst. Cumulus expansion increased with 10⁻⁶–10⁻³ mM E2, but decreased with fulvestrant. HAS2, PTGS2, PTX3 and OSFs expression increased in the 10⁻⁶–10⁻³ mM E2 groups. Significantly higher cleavage and blastocyst rates were observed in the 10⁻⁴ mM E2 group than in the fulvestrant and 0 mM E2 groups. Moreover, in the 10⁻⁴ mM group, blastocysts at 7 days had higher cell counts than the other groups. In conclusion, the increase in cumulus expansion and subsequent oocyte development after the addition of E2 to IVM medium may have resulted from increased cumulus-expansion-related factor expression and OSF levels.

Activation of Steroidogenesis, Anti-Apoptotic Activity, and Proliferation in Porcine Granulosa Cells by RUNX1 Is Negatively Regulated by H3K27me3 Transcriptional Repression

H3K27me3 is an epigenetic modification that results in the repression of gene transcription. The transcription factor RUNX1 (the runt-related transcription factor 1) influences granulosa cells' growth and ovulation. This research uses ELISA, flow cytometry, EDU, ChIP-PCR, WB and qPCR to investigate steroidogenesis, cell apoptosis, and the proliferation effect of RUNX1 in porcine granulosa cells (pGCs) as regulated by H3K27me3. Decreased H3K27me3 stimulates the expression of steroidogenesis-related genes, including CYP11A1, PTGS2, and STAR, as well as prostaglandin. H3K27me3 transcriptionally represses RUNX1 here, whereas RUNX1 acts as an activator of FSHR, CYP11A1, and CYP19A1, promoting the production of androgen, estrogen, and prostaglandin, as well as increasing anti-apoptotic and cell proliferation activity, but decreasing progesterone. Both the complementary recovery of the H3K27me3 antagonist with the siRUNX1 signal, and the H3K27me3 agonist with the RUNX1 signal to maintain RUNX1 lead to the activation of CYP19A1, ER1, HSD17β4, and STAR here. Androgen and prostaglandin are significantly repressed but progesterone is markedly increased with the antagonist and siRUNX1. Prostaglandin is significantly promoted with the agonist and RUNX1. Furthermore, H3K27me3-RUNX1 affects the anti-apoptotic activity and stimulation of proliferation in pGCs. The present work verifies the transcriptional suppression of RUNX1 by H3K27me3 during antral follicular development and maturation, which determines the levels of hormone synthesis and cell apoptosis and proliferation in the pGC microenvironment.

Granulosa secreted factors improve the developmental competence of cumulus oocyte complexes from small antral follicles in sheep

Oocyte in vitro maturation can be improved by mimicking the intra-follicular environment. Oocyte, cumulus cells, granulosa cells, and circulating factors act as meiotic regulators in follicles and maintain oocyte in the meiotic phase until oocyte becomes competent and ready to be ovulated. In a randomized experimental design, an ovine model was used to optimize the standard in vitro maturation media by Granulosa secreted factors. At first, the development capacity of oocyte derived from medium (>4 to 6 mm) and small (2 to ≤4 mm) size follicles was determined. Differential gene expression of granulosa secreted factors and their receptors were compared between the cumulus cells of the two groups. Then, the best time and concentration for arresting oocytes at the germinal vesicle stage by natriuretic peptide type C (CNP) were determined by nuclear staining in both groups. Oocyte quality was further confirmed by calcein uptake and gene expression. The developmental competence of cumulus oocyte complexes derived from small size follicles that were cultured in the presence of CNP in combination with amphiregulin (AREG) and prostaglandin E2 (PGE2) for 24 h was determined. Finally, embryo quality was specified by assessing expressions of NANOG, SOX2, CDX2, OCT4, and TET1. The cumulus oocyte complexes derived from small size follicles had a lower capacity to form blastocyst in comparison with cumulus oocyte complexes derived from medium size follicles. Prostaglandin E receptor 2 and prostaglandin-endoperoxide synthase 2 had significantly lower expression in cumulus cells derived from small size follicles in comparison with cumulus cells derived from medium size follicles. Natriuretic peptide type C increased the percentage of cumulus oocyte complexes arresting at the germinal vesicle stage in both oocytes derived from medium and small follicles. Gap junction communication was also improved in the presence of natriuretic peptide type C. In oocytes derived from small size follicles; best blastocyst rates were achieved by sequential exposure of cumulus oocyte complexes in [TCM+CNP (6 h), then cultured in TCM+AREG+PGE2 (18h)] and [TCM+CNP (6 h), then cultured in conventional IVM supplements+AREG+PGE2 (18h)]. Increased SOX2 expression was observed in [TCM+CNP (6 h), then cultured in TCM+AREG+PGE2 (18h)], while decreased OCT4 expression was observed in [TCM+CNP (6 h), then cultured in conventional IVM supplements+AREG+PGE2 (18h)]. It seems that the natriuretic peptide type C modulates meiotic progression, and oocyte development is probably mediated by amphiregulin and prostaglandin E2. These results may provide an alternative IVM method to optimize in vitro embryo production in sheep and subsequently for humans.

Effects of EPA on bovine oocytes matured in vitro with antioxidants: Impact on the lipid content of oocytes and early embryo development

The eicosapentaenoic acid (EPA) is an n-3 polyunsaturated fatty acid (PUFA) present in the lipid composition of bovine oocytes. Little is known about the importance of EPA in bovine oocyte maturation and embryo development in vitro. Although previous work suggest that n-3 PUFAs may inhibit oocyte maturation, the available data are inconsistent. In this study, we evaluated the effect of EPA (1, 10, 100 nM) during in vitro maturation (IVM) of bovine oocytes, alone and in combination with vitamin E (VE) or cysteamine (CYS). EPA treatment in IVM decreased oocyte lipid content and affected lipid droplets pattern (P < 0.05). EPA 100 nM reduced oocytes maturation rate (P < 0.05), without affecting cumulus expansion. At the concentrations tested, EPA did not modify embryo development. However, the addition of antioxidants during IVM reduced the levels of reactive oxygen species in the culture system by increasing intracellular glutathione content (P < 0.05). Besides, the combination of EPA with VE or CYS reduced the percentages of MI oocytes after 24 h of IVM (P < 0.05). EPA reduced oocyte lipid content without any detrimental for embryo development.

Temporal changes in the transcriptomic profile of granulosa cells of pigs treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin

The 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) compound is an environmental chemical adversely affecting reproductive processes. Intracellular TCDD effects are mediated via aryl hydrocarbon receptor (AhR). The aim of the current study was to identify genes linking the AhR pathway with phenotypic consequences of TCDD action in granulosa cells of pigs. By applying multifactorial analysis, with TCDD and incubation time as factors, it was possible to determine temporal changes induced by TCDD in the cell transcriptome. Among the identified 144 differentially expressed genes (DEGs; P_adjusted<0.05, log2 fold change (FC)≥1), 111 DEGs were classified as sustained genes (FC values changing between 3 and 24 h). Eighty six DEGs were classified as early genes and only nine as late genes (FC changes observed between 3 and 12 h or 12 and 24 h, respectively). The sustained gene category included genes related to TCDD mechanism of action (AHR, ARNTL, CYP1A1), cell proliferation (TGFβ3), follicular development and ovulation (PTGS2) as well as stress response (NR3C1). The early gene category contained DEGs associated with cell proliferation (DUSP4, TAB1) and cellular response to stress (DHX34). The CYP1A1 gene was the only DEG classified as an early, late and sustained gene. The multifactorial approach allowed for statistically analyzing TCDD-induced changes over time in the gene expression in granulosa cells of pigs. Changes over time in the granulosal transcriptome profile indicated the involvement of stress related molecules in the cellular response to TCDD and TCDD effects on ovulation. The TCDD effects were particularly evident during the early stage of action by this compound.

Fibroblast growth factor 2 regulates cumulus differentiation under the control of the oocyte

PURPOSE

We first assessed regulation of FGF2 expression in cumulus cells by FSH and oocyte-secreted factors during in vitro maturation (IVM). Then, we tested the hypothesis that FGF2 regulates meiotic progression, cumulus expansion, and apoptosis in cumulus-oocyte complexes (COC) undergoing IVM.

METHODS

In vitro maturation of bovine COC was utilized as a model to assess regulation of FGF2 expression by FSH and oocyte-secreted factors (via microsurgical removal of the oocyte), as well as effects of graded doses of FGF2 on meiotic progression, degree of cumulus expansion, dissociation of cumulus cells, and cumulus cells apoptosis. Expression of genes regulating functional endpoints altered by FGF2 treatment was assessed in cumulus cells by real-time PCR. Cultures were replicated 4-5 times and effects of treatments were tested by ANOVA.

RESULTS

FGF2 mRNA expression was increased by FSH and oocyte-secreted factors during IVM. Addition of FGF2 to the IVM medium advanced meiosis resumption, decreased the ease with which cumulus cells were dissociated, and inhibited cumulus cells apoptosis. Decreased cumulus dissociation was accompanied by decreased expression of TNFAIP6.

CONCLUSIONS

This is the first study showing that FGF2 expression is regulated by the oocyte in cumulus cells. Moreover, we report novel effects of FGF2 on cumulus cell survival and extracellular matrix (ECM) quality during IVM that may favor acquisition of developmental competence and suggest physiological roles during the final steps of COC differentiation.

Action mechanisms of n-3 polyunsaturated fatty acids on the oocyte maturation and developmental competence: Potential advantages and disadvantages

Infertility is a growing problem worldwide. Currently, in vitro fertilization (IVF) is widely performed to treat infertility. However, a high percentage of IVF cycles fails, due to the poor developmental potential of the retrieved oocyte to generate viable embryos. Fatty acid content of the follicular microenvironment can affect oocyte maturation and the subsequent developmental competence. Saturated and monounsaturated fatty acids are mainly used by follicle components as primary energy sources whereas polyunsaturated fatty acids (PUFAs) play a wide range of roles. A large body of evidence supports the beneficial effects of n-3 PUFAs in prevention, treatment, and amelioration of some pathophysiological conditions including heart diseases, cancer, diabetes, and psychological disorders. Nevertheless, current findings regarding the effects of n-3 PUFAs on reproductive outcomes in general and on oocyte quality more specifically are inconsistent. This review attempts to provide a comprehensive overview of potential molecular mechanisms by which n-3 PUFAs affect oocyte maturation and developmental competence, particularly in the setting of IVF and thereby aims to elucidate the reasons behind current discrepancies around this topic.

Prostaglandin E2 involvement in mammalian female fertility: ovulation, fertilization, embryo development and early implantation

BACKGROUND

Infertility in mammalian females has been a challenge in reproductive medicine. The causes of female infertility include anovulation, ovulated oocyte defects, abnormal fertilization, and insufficient luteal support for embryo development, as well as early implantation. Ovulation induction, in vitro fertilization and luteal support regimens have been performed for decades to increase fertility rates. The identification of proteins and biochemical factors involved in female reproduction is essential to further increase female fertility rates. Evidence has shown that prostaglandins (PGs) might be involved in the female reproductive process, mainly ovulation, fertilization, and implantation. However, only a few studies on individual PGs in female reproduction have been done so far. This review aimed to identify the pivotal role of prostaglandin E2 (PGE2), a predominant PG, in female reproduction to improve fertility, specifically ovulation, fertilization, embryo development and early implantation.

RESULTS

Prostaglandin E2 (PGE2) was shown to play a relevant role in the ovulatory cascade, including meiotic maturation, cumulus expansion and follicle rupture, through inducing ovulatory genes, such as Areg, Ereg, Has2 and Tnfaip6, as well as increasing intracellular cAMP levels. PGE2 reduces extracellular matrix viscosity and thereby optimizes the conditions for sperm penetration. PGE2 reduces the phagocytic activity of polymorphonuclear neutrophils (PMNs) against sperm. In the presence of PGE2, sperm function and binding capacity to oocytes are enhanced. PGE2 maintains luteal function for embryo development and early implantation. In addition, it induces chemokine expression for trophoblast apposition and adhesion to the decidua for implantation.

CONCLUSION

It has been shown that PGE2 positively affects different stages of female fertility. Therefore, PGE2 should be taken into consideration when optimizing reproduction in infertile females. We suggest that in clinical practice, the administration of non-steroidal anti-inflammatory drugs, which are PGE2 synthesis inhibitors, should be reasonable and limited in infertile women. Additionally, assessments of PGE2 protein and receptor expression levels should be taken into consideration.