Effects of FGF10 on Bovine Oocyte Meiosis Progression, Apoptosis, Embryo Development and Relative Abundance of Developmentally Important GenesIn Vitro

Factors Influencing the Maturation and Developmental Competence of Yak (Bos grunniens) Oocytes In Vitro

The yak (Bos grunniens) is a unique breed living on the Qinghai-Tibet Plateau and its surrounding areas, providing locals with a variety of vital means of living and production. However, the yak has poor sexual maturity and low fertility. High-quality mature oocytes are the basis of animal breeding technology. Recently, in vitro culturing of oocytes and embryo engineering technology have been applied to yak breeding. However, compared to those observed in vivo, the maturation rate and developmental capacity of in vitro oocytes are still low, which severely limits the application of in vitro fertilization and embryo production in yaks. This review summarizes the endogenous and exogenous factors affecting the in vitro maturation (IVM) and developmental ability of yak oocytes reported in recent years and provides a theoretical basis for obtaining high-quality oocytes for in vitro fertilization and embryo production in yaks.

Beneficial effects of fibroblast growth factor 10 supplementation during in vitro maturation of buffalo cumulus-oocyte complexes

Fibroblast growth factor 10 (FGF10) is an important regulator of the mammalian cumulus-oocyte complex that plays a crucial role in oocyte maturation. In this study, we investigated the effects of FGF10 supplementation on the in vitro maturation (IVM) of buffalo oocytes and its related mechanisms. During IVM, the maturation medium was supplemented with a range of concentrations of FGF10 (0, 0.5, 5, and 50 ng/mL) and the resulting effects were corroborated using aceto-orcein staining, TUNEL apoptosis assay, detection of Cdc2/Cdk1 kinase in oocytes, and real-time quantitative PCR. In matured oocytes, the 5 ng/mL-FGF10 treatment resulted in a significantly increased nuclear maturation rate, which increased the activity of maturation-promoting factor (MPF) and enhanced buffalo oocyte maturation. Furthermore, it treatment significantly inhibited the apoptosis of cumulus cells, while simultaneously promoting its proliferation and expansion. This treatment also increased the absorption of glucose in cumulus cells. Thus, our results indicate that adding an appropriate concentration of FGF10 to a maturation medium during IVM can be beneficial to the maturation of buffalo oocytes and improve the potential of embryo development.

Population structure, genetic diversity and prolificacy in pishan red sheep under an extreme desert environment

Extreme environmental conditions are a major challenge for livestock production. Changes in climate conditions, especially those that lead to extreme weather, can reduce livestock production. The screening of genes and molecular markers is of great significance to explore the genetic mechanism of sheep prolificacy traits in Taklimakan Desert environment. We selected healthy adult Pishan Red Sheep (PRS) and Qira Black Sheep (QR) which live in Taklimakan Desert environment, collected blood from jugular vein, extracted DNA, and prepared Illumina Ovine SNP50 chip. For PRS, linkage disequilibrium (LD) was calculated using the ovine SNP50 Beadchip and the effective population size (Ne) was estimated using SMC++. The genetic characteristics of PRS were analyzed by integrated haplotype score (iHS) and fixation index (F _ST ). The result showed that r ² of PRS was 0.233 ± 0.280 in the range of 0-10 Kb and decreased with increasing distances. SMC++ tested that the Ne of PRS remained at 236.99 in recent generations. 184 genes were screened out under iHS 1% threshold, and 1148 genes were screened out with F _ST under the 5% threshold, and 29 genes were obtained from the intersection of the two gene sets. In this study, the genetic characteristics of PRS and QR were compared by ovine genome chip, and the related excellent genes were searched, providing reference for the protection of sheep germplasm resources and molecular breeding in a desert environment.

The putative roles of FSH and AMH in the regulation of oocyte developmental competence: from fertility prognosis to mechanisms underlying age-related subfertility

BACKGROUND

Fertility loss during female ageing is associated with increasing basal FSH and decreasing anti-Müllerian hormone (AMH) concentrations, together with compromised oocyte quality, presumably due to increased oxidative stress (OS) and DNA damage, as well as reduced metabolic and meiotic competences. Basal FSH and AMH circulatory concentrations have been broadly utilized as IVF success predictors, regardless of fluctuations in prognostic accuracy; basal FSH and AMH perform better in pre-advanced maternal age (AMA: >35 years) and AMA patients, respectively. The relationships between FSH and AMH intrafollicular levels and IVF outcomes suggest, nevertheless, that both hormones regulate oocyte competence, supporting the hypothesis that changes in FSH/AMH levels cause, at least in part, oocyte quality degradation during ageing. To understand the reasons behind the fluctuations in FSH and AMH prognostic accuracies and to clarify their participation in mechanisms determining oocyte competence and age-related subfertility, a deeper knowledge of the regulation of FSH and AMH intrafollicular signalling during the female reproductive lifespan, and of their effects on the cumulus-oocyte complex, is required.

OBJECTIVE AND RATIONALE

An extensive body of information on the regulation of FSH and AMH intrafollicular availability and signalling, as well as on the control of folliculogenesis and oocyte metabolism, has been accumulated. However, these datasets have been explored within the relatively narrow boundaries of their specific subjects. Given the aforementioned gaps in knowledge and their clinical relevance, herein we integrate clinical and basic data, within a wide biological perspective, aiming to shed light on (i) the reasons for the variability in the accuracy of serum FSH and AMH as fertility markers, and on (ii) the potential roles of these hormones in mechanisms regulating oocyte quality, particularly those associated with ageing.

SEARCH METHODS

The PubMed database encompassing the period between 1960 and 2021 was searched. Principal search terms were FSH, FSH receptor, AMH, oocyte, maternal age, cumulus, transzonal projections (TZPs), actin, OS, redox, reactive oxygen species, mitochondria, DNA damage, DNA repair, aneuploidy, spindle, meiosis, gene expression, transcription, translation, oocyte secreted factors (OSFs), cAMP, cyclic guanosine monophosphate, natriuretic peptide C, growth differentiation factor 9, bone morphogenetic protein 15 and fibroblast growth factor.

OUTCOMES

Our analysis suggests that variations in the accuracy of fertility prognosis reflect a modest association between circulatory AMH levels and oocyte quality as well as increasing basal FSH inter-cycle variability with age. In addition, the basic and clinical data articulated herein support the hypothesis that increased intrafollicular FSH levels, as maternal age advances, may override the physiological protective influences of AMH and OSFs against excessive FSH signalling in cumulus cells. This would result in the disruption of oocyte homeostasis via reduced TZP-mediated transfer of cumulus-derived molecules essential for meiotic competence, gene expression, redox activity and DNA repair.

WIDER IMPLICATIONS

In-depth data analysis, encompassing a wide biological perspective has revealed potential causative mechanisms of age-related subfertility triggered by alterations in FSH/AMH signalling during the female reproductive life. Insights from new mechanistic models arising from this analysis should contribute to advancing our comprehension of oocyte biology in humans and serve as a valuable reference for novel AMA subfertility treatments aimed at improving oocyte quality through the modulation of AMH/FSH action.

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.

The antioxidant dimethylthiourea improves IVF efficiency and decreases cumulus cell apoptosis in pigs

Abattoir ovaries, which are the main source of oocytes for reproductive biotechnologies, arrive at the laboratory under ischaemic conditions. Reoxygenation generates reactive oxygen species (ROS) in ischaemic tissues, which could affect oocyte quality. The aim of this study was to evaluate the effect of supplementation of media with dimethylthiourea (DMTU) during the collection and washing of cumulus-oocyte complexes (COC) on ROS levels, COC apoptosis and oocyte nuclear and cytoplasmic maturation. Thus, the collection (TCM-199) and washing (TCM-199 with 10% porcine follicular fluid, sodium pyruvate and antibiotics) media were supplemented with 1 and 10mM DMTU. In the control group, the media were not supplemented with DMTU. Intracellular ROS levels decreased significantly in the DMTU-treated groups (P<0.05). Although no effects on rate of nuclear maturation were observed, DMTU significantly increased sperm penetration rates without increasing polyspermy (P<0.05). The addition of 10mM DMTU to the collection and washing media enhanced IVF efficiency. DMTU did not modify the early or late apoptosis of oocytes. Both concentrations of DMTU significantly increased viability and decreased the apoptosis of cumulus cells (P<0.05). These results suggest that the addition of 1 or 10mM of DMTU to the media during the collection and washing of porcine COCs is useful for decreasing cumulus apoptosis mediated by ROS and for optimising the IVF of porcine oocytes.

Enzymatic activity of mouse group X-sPLA2 improves in vitro production of preimplantation bovine embryos

Assisted reproductive technologies (ART) are widely used for both humans and domestic animals. In bovine species, in vitro embryo production is increasingly used and significant efforts are being made to optimize media and culture conditions. Phospholipase A2 (PLA2) are lipolytic enzymes that hydrolyze glycerophospholipids to produce free fatty acids and lysophospholipids that have been found to be critical for many biological processes. Mouse group X secreted PLA₂ (mGX) is abundant in the male reproductive tract and its use during sperm capacitation has been shown to improve in vitro production of viable embryos in a mouse model. Here, we examined its effect in the bovine species, testing the impact of mGX on the three steps involved in vitro production of preimplantation embryos: oocyte maturation, fertilization and preimplantation development. We found that incubating cumulus oocyte complexes (COC) or gametes with mGX resulted in increased blastocyst hatching and blastocyst production, respectively. The increases of embryo production induced by the phospholipase mGX were not observed for the catalytically inactive mutant H48Q-mGX, suggesting that these effects require the enzymatic activity of mGX. We also tested bGIB, a bovine homolog of mGX. bGIB failed to improve blastocyst production, underlining the high specificity of mGX. In conclusion, the results presented show that the effects of mGX are not restricted to the mouse model and that it is potent in the bovine species as well. This result strengthens the potential of mGX as a "pro-fertility drug" for mammalian reproduction.

Prosurvival effect of cumulus prostaglandin G/H synthase 2/prostaglandin2 signaling on bovine blastocyst: impact on in vivo posthatching development

Apoptotic activity is a common physiological process which culminates at the blastocyst stage in the preimplantation embryo of many mammals. The degree of embryonic cell death can be influenced by the oocyte microenvironment. However, the prognostic significance of the incidence of apoptosis remains undefined. Prostaglandin E2 (PGE2) derived from prostaglandin G/H synthase-2 (PTGS2) activity is a well-known prosurvival factor that is mainly studied in oncology. PGE2 is the predominant PTGS2-derived prostaglandin present in the oocyte microenvironment during the periconceptional period. Using an in vitro model of bovine embryo production followed by transfer and collection procedures, we investigated the impact of periconceptional PGE2 on the occurrence of spontaneous apoptosis in embryos and on subsequent in vivo posthatching development. Different periconceptional PGE2 environments were obtained using NS-398, a specific inhibitor of PTGS2 activity, and exogenous PGE2. We assessed the level of embryonic cell death in blastocysts at day 8 postfertilization by counting total cell numbers, by the immunohistochemical staining of active caspase-3, and by quantifying terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling signals and apoptosis regulator (BCL-2/BAX) mRNA expression. Morphometric parameters were used to estimate the developmental stage of the embryonic disk and the extent of trophoblast elongation on day 15 conceptuses. Our findings indicate that periconceptional PGE2 signaling durably impacts oocytes, conferring increased resistance to spontaneous apoptosis in blastocysts and promoting embryonic disk development and the elongation process during preimplantation development.

Fibroblast growth factor 10 markedly improves in vitro maturation of porcine cumulus-oocyte complexes

Growth factors synthesized by ovarian somatic cells affect cumulus cell expansion and oocyte maturation in vitro. Fibroblast growth factor 10 (FGF10), for example, is a known regulator of mammalian cumulus-oocyte complex maturation. In this study, we investigated the effects of 0, 5, 10, 50, and 100 ng/mL FGF10 (5F, 10F, 50F, and 100F, respectively) on in vitro cumulus cell expansion, oocyte maturation, and embryo development. The percentage of fully expanded cumulus cells at the oocyte's metaphase-II (MII) stage was significantly higher in the 10F-treated group than in the control. Transcript abundance of the cumulus cell expansion-related gene encoding hyaluronian synthase 2 (HAS2) in cumulus cells at oocyte germinal vesicle breakdown (GVBD) was significantly higher in the 10F- and 50F-treated groups compared to untreated controls, whereas the mRNA abundance of the protease cathepsin B (CTSB) at the oocyte MII stage was remarkably decreased in the 10F-treated group. The percentage of oocytes with normal spindles was greater in the 10F- and 50F-treated group at GVBD than in the other groups; the 5F-, 10F-, and 100F-treated groups were higher than the control; and the 50F-treated group was highest at MII. The abundance of GDF9 and BMP15 transcript at GVBD and BMP15 and CCNB1 transcripts at MII increased in the 10F-treated group. Cleavage rate, blastocyst formation rate, and total cell number were significantly higher in the 5F- to 50F-treated groups. These results demonstrate that FGF10 markedly improves cumulus cell expansion, oocyte maturation, and subsequent embryo development. Mol. Reprod. Dev. 84: 67-75, 2017. © 2016 Wiley Periodicals, Inc.

Bovine in vitro embryo production: the effects of fibroblast growth factor 10 (FGF10)

PURPOSE

In an attempt to improve in vitro embryo production, we investigated the effect of fibroblast growth factor 10 (FGF10) during in vitro maturation on the developmental capacity of bovine oocytes.

MATERIAL AND METHODS

Cumulus-oocyte complexes (COCs) were aspirated from follicles of 3-8 mm diameter. After selection, the COCs were matured in medium with or without 0.5 ng/mL of FGF10. The effect of FGF10 during in vitro maturation (IVM) on nuclear maturation kinetics and expansion of the cumulus cells was investigated. Oocyte competence was assessed by the production and development speed of embryos and the relative expression of genes associated with embryo quality.

RESULTS

FGF10 delayed the resumption of meiosis from 8 h onwards, but did not affect the percentage of oocytes reaching metaphase II, nor did it increase cumulus expansion at 22 h of maturation. We found no difference between treatments regarding embryo production, developmental speed, and gene expression.

CONCLUSION

In conclusion, the presence of FGF10 during IVM had no effect on embryo production, developmental speed, and gene expression.

Mechanisms of fibroblast growth factor signaling in the ovarian follicle

Fibroblast growth factors (FGFs) have been shown to alter growth and differentiation of reproductive tissues in a variety of species. Within the female reproductive tract, the effects of FGFs have been focused on the ovary, and the most studied one is FGF2, which stimulates granulosa cell proliferation and decreases differentiation (decreased steroidogenesis). Other FGFs have also been implicated in ovarian function, and this review summarizes the effects of members of two subfamilies on ovarian function; the FGF7 subfamily that also contains FGF10, and the FGF8 subfamily that also contains FGF18. There are data to suggest that FGF8 and FGF18 have distinct actions on granulosa cells, despite their apparent similar receptor binding properties. Studies of non-reproductive developmental biology also indicate that FGF8 is distinct from FGF18, and that FGF7 is also distinct from FGF10 despite similar receptor binding properties. In this review, the potential mechanisms of differential action of FGF7/FGF10 and FGF8/FGF18 during organogenesis will be reviewed and placed in the context of follicle development. A model is proposed in which FGF8 and FGF18 differentially activate receptors depending on the properties of the extracellular matrix in the follicle.