In vitro maturation of porcine oocytes using a defined medium and developmental capacity after intracytoplasmic sperm injection

Increased ROS levels in mitochondrial outer membrane protein Mul1-deficient oocytes result in abnormal preimplantation embryogenesis

Reactive oxygen species (ROS) are associated with oocyte maturation inhibition, and N-acetyl-l-cysteine (NAC) partially reduces their harmful effects. Mitochondrial E3 ubiquitin ligase 1 (Mul1) localizes to the mitochondrial outer membrane. We found that female Mul1-deficient mice are infertile, and their oocytes contain high ROS concentrations. After fertilization, Mul1-deficient embryos showed a DNA damage response (DDR) and abnormal preimplantation embryogenesis, which was rescued by NAC addition and ROS depletion. These observations clearly demonstrate that loss of Mul1 in oocytes increases ROS concentrations and triggers DDR, resulting in abnormal preimplantation embryogenesis. We conclude that manipulating the mitochondrial ROS levels in oocytes may be a potential therapeutic approach to target infertility.

Comparison of ICSI, IVF, and in vivo derived embryos to produce CRISPR-Cas9 gene-edited pigs for xenotransplantation

Genome editing in pigs for xenotransplantation has seen significant advances in recent years. This study compared three methodologies to generate gene-edited embryos, including co-injection of sperm together with the CRISPR-Cas9 system into oocytes, named ICSI-MGE (mediated gene editing); microinjection of CRISPR-Cas9 components into oocytes followed by in vitro fertilization (IVF), and microinjection of in vivo fertilized zygotes with the CRISPR-Cas9 system. Our goal was to knock-out (KO) porcine genes involved in the biosynthesis of xenoantigens responsible for the hyperacute rejection of interspecific xenografts, namely GGTA1, CMAH, and β4GalNT2. Additionally, we attempted to KO the growth hormone receptor (GHR) gene with the aim of limiting the growth of porcine organs to a size that is physiologically suitable for human transplantation. Embryo development, pregnancy, and gene editing rates were evaluated. We found an efficient mutation of the GGTA1 gene following ICSI-MGE, comparable to the results obtained through the microinjection of oocytes followed by IVF. ICSI-MGE also showed higher rates of biallelic mutations compared to the other techniques. Five healthy piglets were born from in vivo-derived embryos, all of them exhibiting biallelic mutations in the GGTA1 gene, with three displaying mutations in the GHR gene. No mutations were observed in the CMAH and β4GalNT2 genes. In conclusion, in vitro methodologies showed high rates of gene-edited embryos. Specifically, ICSI-MGE proved to be an efficient technique for obtaining homozygous biallelic mutated embryos. Lastly, only live births were obtained from in vivo-derived embryos showing efficient multiple gene editing for GGTA1 and GHR.

Role of N-acetylcysteine treatment in women with advanced age undergoing IVF/ICSI cycles: A prospective study

Objective

The main objective of this study was to explore the efficacy of a new antioxidant N-acetylcysteine (NAC) supplementation in reproductive outcomes of advanced age women undergoing in vitro fertilization/intracytoplasmic sperm injection-embryo transfer (IVF/ICSI-ET), and the effect on the expression of L-glutathione (GSH) in follicular fluid (FF) and mitochondrial DNA (mtDNA) copy number of granulosa cells.

Methods

The present prospective randomized controlled study was conducted in 200 patients with advanced age women undergoing GnRH antagonist protocol. The treatment group (group A) consisted of 100 women who received N-acetylcysteine treatment from the menstrual phase of the previous cycle for about 45 days using the GnRH antagonist protocol. The control group (group B) consisted of 100 women who received the same protocol without N-acetylcysteine. Total gonadotrophin dosage the number of oocyte received, high-quality blastocysts, and pregnancy outcomes were compared between two groups. Pregnancy outcomes included biochemical pregnancy rate, clinical pregnancy rate, embryo implantation rate, ectopic pregnancy rate, multiple pregnancy rate, and ongoing pregnancy rate. Follicular fluid (FF) was collected after oocytes were gathered. The GSH content in the FF was tested with enzyme linked immunosorbent assay (ELISA). The mtDNA copy number of the granulosa cells was measured using real-time PCR techniques.

Results

Total doses of Gn in the NAC treatment group were less than those in the control group (2385.50 ± 879.19 vs. 2527.63 ± 1170.33, P = 0.047). Compared with the control, the number of high-quality blastocysts in NAC treatment increased significantly (1.82 ± 2.12 vs. 1.43 ± 1.58, p = 0.014). Clinical pregnancy rates did not differ in both groups (all P > 0.05). At the same time, the GSH content in the FF differed significantly between the two groups (1.88 ± 1.23 vs. 1.07 ± 0.70, p = 0.001). There was no significant difference in the mtDNA copy number between the two groups (P = 0.157).

Conclusion

A combination of NAC and Gn treatment is capable of improving the ovarian response to superovulation drugs in assisted reproductive technologies (ARTs) and also in aged populations. The addition of NAC during IVF can improve the quality of blastocysts in advanced age female subjects. However, more clinical trials are required to be designed to confirm this conclusion in future.

Ethics and dissemination

The experiment solicited approval from the Institutional ethics committee of the Affiliated Reproductive Hospital of Shandong University. All the participants provided written informed consent. This survey was conducted as per the Declaration of Helsinki and relevant amendments.

Trial registration number

www.chictr.org.cn, identifier ChiCTR2100048297.

Optimization of in vitro embryo production and zygote vitrification for the indigenous Vietnamese Ban pig: The effects of different in vitro oocyte maturation systems

The Vietnamese Ban pig is a precious genetic resource that needs to be preserved. In vitro embryo production from in vitro matured (IVM) oocytes is an important tool for the utilization of cryopreserved porcine sperm. The aim of this study was to compare two media for the IVM of Ban pig oocytes. Immature oocytes were subjected to IVM either in a non-defined (TCM-199 + pig follicular fluid) or in a defined base medium (POM + epidermal growth factor). At the end of IVM, the oocytes were in vitro fertilized (IVF) with frozen Ban sperm. Ten hours after IVF, the oocytes were either subjected to orcein staining to check fertilization and maturation status or cultured in vitro for 7 days. There was no difference between the two IVM media in terms of percentages of oocyte maturation and blastocyst production. However, the percentage of male pronuclear formation after IVF and the total cell numbers in blastocysts were higher with the defined system. Zygotes obtained by the two IVM systems survived vitrification at similar rates. In conclusion, the two IVM systems were both effective for the production of Ban pig embryos; however, better embryo quality was achieved with the defined one.

Screening high-quality fetal bovine serum for porcine oocyte maturation in vitro

Fetal bovine serum (FBS) is widely used in cell cultures due to its high stability and easy access. It was also used as a substitute for porcine follicular fluid (PFF) in previous studies. However, FBS components are unclear, and the presence of FBS in culture media may introduce a variation from batch to batch. This study aimed to establish an effective method to screen FBS in place of PFF in the culture media for porcine oocytes in vitro. We screened FBS from different sources by using porcine fetal fibroblast cells. The effects of six FBS samples on porcine fetal fibroblast cell growth were tested via frozen cell survival assay, cell clone formation assay, cell growth curve, and cell passage activity assay. The best serum that we called GFBS (heat-inactivated FBS, cat. no. 10500-64; Gibco) showed a similar effect on the maturation and development of porcine oocytes to that of PFF and can be used as a good substitute for PFF. These results suggested that the porcine fetal fibroblast cell culture test can be used as a valuable method to screen FBS for porcine oocyte maturation and embryonic development in vitro.

Production of collared peccary (Pecari tajacu Linnaeus, 1758) parthenogenic embryos following different oocyte chemical activation and in vitro maturation conditions

To optimize the protocols for assisted reproductive techniques (ARTs) in collared peccary (Pecari tajacu Linnaeus, 1758), we evaluated various conditions for oocyte in vitro maturation (IVM) and chemical activation. Initially, we assessed the IVM rates, cumulus-oocyte complex (COC) quality, and oocyte morphometry in the absence or presence of epidermal growth factor (EGF). There was no difference between the COCs matured in absence or presence of EGF for the expansion of cumulus cells (97.6% ± 1.2 vs. 100% ± 0.0), presence of first polar body (65.9% ± 1.2 vs. 70.5% ± 1.8), nuclear status in second metaphase (62.5% ± 11.6 vs. 68.4% ± 4.9), cytoplasmic maturation (100.0% ± 0.7 vs. 75.0% ± 0.7), reactive oxygen species levels (0.5 ± 0.2 vs. 0.3 ± 0.1), and mitochondrial membrane potential (1.1 ± 0.2 vs. 1.1 ± 0.1). However, the zona pellucida thickness of matured COCs was reduced in the presence of EGF. Thus, the EGF group was used for further experiments. The oocytes were artificially activated with ionomycin and four secondary activator combinations [6-dimethylaminopurine (6D), 6D and cytochalasin B (6D + CB), cycloheximide (CHX), and CHX and CB (CHX + CB)]. The effect of immature COCs based on cumulus cell layers and cytoplasm homogeneity (GI and GII or GIII COCs) on embryonic development and quality was evaluated. There was no difference in the cleavage rates among the groups of secondary activators. The cleavage rates of embryos derived from GI/GII and GIII COCs were greater than 72.2% and 25.0%, respectively. Moreover, treatment with CHX showed a reduction in the cleavage rate of embryos derived from GIII COCs when compared to the cleavage rate of embryos derived from GI/GII COCs (P < 0.05). Nevertheless, higher rates of blastocyst/total GI and GII COCs were observed in the 6D group (27.6% ± 0.3) compared to CHX group (6.9% ± 0.3). Additionally, only 6D treatment resulted in the production of embryos derived from GIII COCs (25.0% ± 0.2). The percentage of the ICM/total cell ratio was also greater in blastocysts derived from 6D (42.5% ± 19.0), 6D + CB (37.9% ± 21.9), and CHX + CB (43.8% ± 19.6) groups when compared to CHX (3.6% ± 0.1) group. Thus, the combination of ionomycin and 6D could produce collared peccary embryos by activation of both GI/GII COCs and GIII COCs. These optimized IVM conditions using EGF and chemical activation using ionomycin and 6D in collared peccaries form the first steps for establishing ARTs to conserve this species.

Influence of N-acetyl-L-cysteine against bisphenol a on the maturation of mouse oocytes and embryo development: in vitro study

BACKGROUND

Bisphenol A (BPA), an endocrine disruptor, is a widely used chemical that has adverse effects on animal development and reproduction. The current research aimed to evaluate the effect of BPA on the in vitro maturation (IVM) and subsequent embryo development of mouse oocytes following in vitro fertilization (IVF).

METHODS

IVM was performed in the presence of different concentrations (0, 20, 50, or 100 μg/mL) of BPA. Nuclear maturation, IVF efficiency and embryonic development were determined. The levels of reactive oxygen species (ROS) and glutathione (GSH) in the BPA (50 μg/mL) group were evaluated. We explored the ability of N-acetyl-L-cysteine (NAC) in the IVM medium to rescue the BPA-induced damage by examining changes in nuclear maturation, IVF rate, blastocyst formation, ROS levels and GSH content.

RESULTS

Compared with the control, BPA (50 μg/mL) supplementation during oocyte IVM significantly inhibited nuclear maturation and decreased fertilization and blastocyst formation rates. In addition, BPA exposure increased ROS levels and decreased GSH content in oocytes. The addition of NAC weakened the BPA-induced suppression of nuclear maturation, relieved the BPA-induced downregulation of the fertilization and blastocyst formation rates, and mitigated the increased ROS levels and decreased GSH content.

CONCLUSION

BPA affects mouse oocyte maturation and subsequent early embryonic developmental competence following IVF by increasing intracytoplasmic oxidative stress in mature oocytes. NAC can reduce these harmful effects to a certain extent.

Detrimental effects of oxidative stress in bovine oocytes during intracytoplasmic sperm injection (ICSI)

Intracytoplasmic sperm injection (ICSI) is an essential technology in animal and human reproduction. However, the developmental competence and pregnancy rate of embryos derived from ICSI are still lower than that from the conventional in vitro fertilization technique. In this report, we focused on reactive oxygen species (ROS) as a potential detrimental factor for ICSI. Experiment 1 was conducted to evaluate the effect of oxidative stress by two different oxygen concentrations (20%: control vs. 5%) in ICSI on the developmental competence (blastocyst rate: day 7, DNA fragmentation rate: day 4) and, ROS concentration and mitochondrial membrane potential of oocytes in ICSI. In the 5% O₂ group, the blastocyst rate (29.5%) was higher and DNA fragmentation rate (4.8 ± 1.0%) was lower than those in the control group significantly (12.7% and 18.2 ± 2.4%, respectively, P < 0.05). Also, ROS concentration in the 5% O₂ group (12.8 ± 0.7) was significantly lower than that in the control group (47.8 ± 6.9, P < 0.05). In experiment 2, we examined the supplementation of media with reduced glutathione (GSH) during ICSI procedure in an attempt to reduce the oxidative stress. The addition of GSH to the culture medium improved the blastocyst rate (17.6% vs. 30.4%, P < 0.05), and decreased the ROS levels in the oocytes (70.0 ± 7.4 vs. 23.9 ± 4.0, P < 0.05). In conclusion, our present study revealed that oocytes are under oxidative stress in ICSI procedure. Reduction of the oxygen concentration to 5% in the culture environment, or the addition of GSH in to the medium during ICSI procedure can promote the normal embryo development following the ICSI.

A potential role of knockout serum replacement as a porcine follicular fluid substitute for in vitro maturation: Lipid metabolism approach

The use of supplements, such as porcine follicular fluid (pFF), fetal bovine serum and human serum albumin are widely used during in vitro maturation (IVM) in different species but these supplements contain undefined components that cause technical difficulties in standardization and influence the efficiency of IVM. Knockout serum replacement (KSR) is a synthetic protein source, without any undefined growth factors or differentiation-promoting factors. Therefore, it is feasible to use KSR as a defined component for avoiding effects of unknown molecules in an IVM system. In this study, the rates of oocyte maturation and blastocyst formation after parthenogenetic activation (PA), somatic cell nuclear transfer (SCNT) and in vitro fertilization (IVF) were significantly higher in the 5% KSR supplemented group than in the unsupplemented control group and more similar to those of the 10% pFF supplemented group. Moreover, the intensity of GDF9, BMP15, ROS, GSH, BODIPY-LD, BODIPY-FA, and BODIPY-ATP staining showed similar values between 5% KSR and 10% pFF, which have significant difference with control group. Most of the gene expression related to lipid metabolism with both supplements exhibited similar patterns. In conclusion, 5% KSR upregulated lipid metabolism and thereby provides an essential energy source to sustain and improve oocyte quality and subsequent embryo development after PA, SCNT, and IVF. These indications support the idea that KSR used as a defined serum supplement for oocyte IVM might be universally used in other species.

Use of Chemicals to Inhibit DNA Replication, Transcription, and Protein Synthesis to Study Zygotic Genome Activation

Maternal-to-zygotic transition is an event that developmental control of early embryos is switched from oocyte-derived factors to the zygotic genome. Ability to inhibit DNA replication, transcription, and translation is an important tool in studying events, such as zygotic genome activation, during embyogenesis. Here, we describe approaches to block DNA replication, transcription, and translation using chemical inhibitors. Then we also demonstrate how the transcript level of a maternally inherited gene, ten-eleven translocation methylcytosine dioxygenase 3, responses to the chemical treatments.

Lack of calcium oscillation causes failure of oocyte activation after intracytoplasmic sperm injection in pigs

In pigs, the efficiency of embryo production after intracytoplasmic sperm injection (ICSI) is still low because of frequent failure of normal fertilization, which involves formation of two polar bodies and two pronuclei. To clarify the reasons for this, we hypothesized that ICSI does not properly trigger sperm-induced fertilization events, especially intracellular Ca²⁺ signaling, also known as Ca²⁺ oscillation. We also suspected that the use of in vitro-matured oocytes might negatively affect fertilization events and embryonic development of sperm-injected oocytes. Therefore, we compared the patterns of Ca²⁺ oscillation, the efficiency of oocyte activation and normal fertilization, and embryo development to the blastocyst stage among in vivo- or in vitro-matured oocytes after ICSI or in vitro fertilization (IVF). Unexpectedly, we found that the pattern of Ca²⁺ oscillation, such as the frequency and amplitude of Ca²⁺ rises, in oocytes after ICSI was similar to that in oocytes after IVF, irrespective of the oocyte source. However, half of the oocytes failed to become activated after ICSI and showed no Ca²⁺ oscillation. Moreover, the embryonic development of normal fertilized oocytes was reduced when in vitro-matured oocytes were used, irrespective of the fertilization method employed. These findings suggest that low embryo production efficiency after ICSI is attributable mainly to poor developmental ability of in vitro-matured oocytes and a lack of Ca²⁺ oscillation, rather than the pattern of oscillation.

The effects of N-acetyl-L-cysteine supplementation on in vitro porcine oocyte maturation and subsequent fertilisation and embryonic development

The effects of supplementation with 1.5 mM n-acetyl-l-cysteine (NAC) during in vitro oocyte maturation were studied. Oocytes were supplemented with 1.5 mM NAC during maturation for 0 to 24 h, 24 to 48 h, or 0 to 48 h then subjected to IVF and embryo development. Oocytes were evaluated after maturation for intracellular glutathione concentration, superoxide dismutase and glutathione peroxidase activities and DNA fragmentation. Fertilisation and embryonic development success were also evaluated. There was no effect of treatment on intracellular glutathione concentrations, enzyme activities or fertilisation success rates. Supplementing NAC during maturation significantly decreased (P < 0.05) the percentage of oocytes with fragmented DNA compared with no NAC supplementation. Supplementing NAC from 24 to 48 h or 0 to 48 h resulted in a significantly higher (P < 0.05) percentage of oocytes with male pronuclei than for oocytes from the other treatment groups. There was no difference in the percentage of embryos cleaved by 48 h after IVF between treatment groups. Supplementing NAC from 24 to 48 h or 0 to 48 h resulted in a significantly higher (P < 0.05) percentage of embryos reaching the blastocyst stage by 144 h after IVF compared with the other treatment groups. These results indicate that supplementation of the oocyte maturation medium with 1.5 mM NAC, specifically during the last 24 h, improves male pronucleus formation and blastocyst development in pigs.

In vitro maturation (IVM) of porcine oocytes

Oocyte maturation is a critical component of in vitro embryo production. If not carried out in a precise manner under optimal conditions, subsequent fertilization and embryo development will be compromised. Here, we describe collection and in vitro maturation procedures in swine that maintain oocyte competence, resulting in successful embryo development following fertilization. These procedures can be used both for basic research purposes and large-scale production of mature oocytes for use in subsequent assisted reproductive technologies.

Synergistic effects of glutathione and β-mercaptoethanol treatment during in vitro maturation of porcine oocytes on early embryonic development in a culture system supplemented with L-cysteine

Various methods have been used to remove reactive oxygen species (ROS) generated from in vitro culture (IVC) conditions that can cause cell injury or death, including the application of low oxygen (O(2)) tension and the addition of antioxidants. The beneficial effects of antioxidants and O(2) tension on IVC of porcine embryos, however, are controversial among researchers. In this study, we sought to determine the effects and optimal concentrations of antioxidants for the development of porcine embryos in an IVC system. Specifically, we examined the synergistic effects of antioxidants on development to the blastocyst stage in a culture system supplemented with L-cysteine during IVM. Of the antioxidants tested (melatonin, glutathione (GSH), β-mercaptoethanol (β-ME), N-acetylcysteine (NAC) and dithiothreitol (DTT)), addition of GSH (1 mM) or β-ME (25 µM) significantly increased development to the blastocyst stage compared with the controls without antioxidant treatment (22.2 ± 4.2% for 1 mM GSH, 25.9 ± 2.2% for 25 µM β-ME and 12-13% for the control, P<0.05). In addition, the mean cell number per blastocyst was increased by approximately 1.7-fold in the presence of GSH or β -ME. These GSH- and β-ME-induced increases in development to the blastocyst stage and total cell number, however, were not mimicked by melatonin, NAC or DTT, all of which are ROS scavengers. The combination of GSH or β-ME with L-cysteine significantly reduced high O(2) tension-induced ROS production (P<0.05). These results suggest that a combination of 1 mM GSH or 25 µM β-ME with 1 mM L-cysteine could be used for production of high quality porcine blastocysts in IVC systems.

Developmental competence of porcine oocytes selected by brilliant cresyl blue and matured individually in a chemically defined culture medium

The objective of this study was to investigate the effects of oocyte selection using brilliant cresyl blue (BCB) and culture density during individual in vitro maturation (IVM) on porcine oocyte maturity and subsequent embryo development using a chemically defined medium. Cumulus-oocyte complexes (COCs) were classified as BCB-positive or BCB-negative after exposure to a BCB solution for 90 min. The classified COCs were matured in a group (15 COCs per 100-microL droplet) or individually (1 COC per 1-, 2.5-, 5-, or 10-microL droplet). Meiotic competence, intraoocyte glutathione concentration, and developmental competence after intracytoplasmic sperm injection were monitored. The BCB selected oocytes competent for nuclear and cytoplasmic maturation. Furthermore, meiotic competence for oocytes matured individually in a 5-microL droplet was superior (P<0.05) to that of oocytes matured in a 1-microL droplet. Also, the culture density in a 5-microL droplet during IVM resulted in a higher (P<0.05) rate of cleaved embryos than that in a 1-microL droplet and produced a similar rate of blastocysts compared with that of a group culture system. Conversely, BCB selection did not improve cleavage and blastocyst formation. In conclusion, it was possible to predict porcine oocytes competent for maturation using oocyte selection with BCB. Moreover, a 5-microL droplet during the individual IVM culture was most suitable for oocyte maturation and subsequent embryo development, although every culture density used in this study supported development up to the blastocyst stage.

Oocyte activation procedures and influence of serum on porcine oocyte maturation and subsequent parthenogenetic and nuclear transfer embryo development

The viability of SCNT embryos is poor, with an extremely low cloned piglet production rate. In the present work, we studied the effect of three activation protocols based on ionomycin treatment (5 μM ionomycin for 5 min and incubated in 2 mM 6-DMAP for 3.5 h) or electric stimuli (two square wave electrical DC pulses of 1.2 kV/cm for 30 μs) combined or not with 6-DMAP on parthenogenetic embryo development. Oocytes activated by ionomycin plus 6-DMAP showed lower cleavage (47.2 vs. 78.5–81.5; p < 0.05) and blastocyst rates (11.3 vs. 29.2–32.1; p < 0.05) than those activated by electrical and electrical plus 6-DMAP treatments. Also, we studied the effect of addition of serum to maturation medium (0% vs. 10%) on nuclear maturation and further parthenogenetic and SCNT embryo development. We observed in the parthenogenetic embryos that cleavage rates in the serum-free group were significantly higher than in the serum-supplemented group (81.8 vs. 69.6% respectively; p < 0.05), although these differences were not detected in blastocyst rates or blastocyst nuclei numbers. Regarding SCNT embryos, no significant differences were observed in cleavage or blastocyst rates between different experimental groups of SCNT embryos. In conclusion, electrical pulse followed or not by 6-DMAP was found to be an efficient procedure to artificially activate MII porcine oocytes. Moreover, the addition of serum to oocyte maturation media did not seem to improve parthenogenetic or SCNT porcine embryo development.

Intracytoplasmic sperm injection in livestock species: an update

Intracytoplasmic sperm injection (ICSI) is a powerful technique in the field of assisted reproduction (ART) and provides exciting opportunities for studying the basic mechanisms of fertilization and early embryo development. Nevertheless, its application in agriculture and conservation biology has been greatly hampered by the low success rate reported for this method in respect of economically important species. Specifically, the rates of blastocyst formation and live newborn are greatly reduced when zygotes are generated by ICSI. Except for humans, ICSI remains a low efficiency technology in comparison with alternatives such as in vitro fertilization (IVF) and its application is less widespread. In this paper, we discuss the present status, applications and factors affecting ICSI in pigs and other species.

PI3-kinase and mitogen-activated protein kinase in cumulus cells mediate EGF-induced meiotic resumption of porcine oocyte

Previous studies have shown that epidermal growth factor (EGF) has the ability to promote in vitro cultured porcine oocyte maturation. However, little is known about the detailed downstream events in EGF-induced meiotic resumption. We designed this study to determine the relationship of EGF, EGFR, phosphatidylinositol 3-kinase (PI3-kinase), MAPK, and germinal vesicle breakdown (GVBD) during oocyte maturation. Our results showed that GVBD in cumulus-enclosed oocytes (CEOs) but not in denuded oocytes (DOs) was induced by EGF in a dose-dependent manner, which indicated that cumulus cells but not oocyte itself were the main target for EGF-induced meiotic resumption. Furthermore, we found that MAPK in cumulus cells rather than in oocyte was activated immediately after EGF administration. To explore whether EGF exerts its functions through MAPK pathway, the activities of EGF receptor (EGFR) and MAPK were inhibited by employing AG1478 and U0126, respectively. Inhibition of MAPK blocked EGF-induced GVBD, whereas inhibition of EGFR prevented MAPK activation. Both AG1478 and U0126 could lead to the failure of EGF-induced GVBD singly. Notably, we found that LY294002, a specific inhibitor of PI3-kinase, effectively inhibited EGF-induced MAPK activation as well as subsequent oocyte meiotic resumption and this inhibition could not be reversed by adding additional EGF. Thus, PI3-kinase-induced MAPK activation in cumulus cells mediated EGF-induced meiotic resumption in porcine CEOs. Together, this study provides evidences demonstrating a linear relationship of EGF/EGFR, PI3-kinase, MAPK and GVBD and presents a relatively definitive mechanism of EGF-induced meiotic resumption of porcine oocyte.

Follicle size-dependent changes in follicular fluid components and oocyte diameter in Antarctic minke whales (Balaenoptera bonaerensis)

The concentrations of various components of follicular fluid were compared among three groups of follicles (small, <5 mm; medium: 5-10 mm; large, >10 mm) with a control that consisted of the components of umbilical serum using seven pregnant Antarctic minke whales. Follicular oocytes recovered from the follicles were also used for measurement of oocyte diameter after removing the cumulus cells. The mean diameter of the ooplasm in the oocytes from the large follicles (143.2 microm) was significantly greater than those from the small (127.1 microm) and medium (131.7 microm) follicles, although there were no significant differences in diameter of the whole oocyte and thickness of the zona pellucida among the three follicular sizes. The osmolarity of the follicular fluid from the small follicles (363.3 mOsmol) was significantly lower than that of the medium follicles (388.9 mOsmol) and tended to be lower than that of large (381.9 mOsmol) follicles, respectively, both of which were similar to that of the umbilical serum (379.5 mOsmol). There was no significant difference in the concentrations of all components of the follicular fluid between the medium and large follicles. As compared with the values of the umbilical serum, the total-protein, glucose, albumin and chlorine concentrations of the follicular fluid from the medium and large follicles were significantly higher, and the total cholesterol and calcium concentrations were significantly lower. The concentrations of lactic acid (85.3-136.0 mg/dl) of the follicular fluid from the three groups of follicles were significantly lower than that of the umbilical serum (360.0 mg/dl). Among the follicles, the follicular fluid from the small follicles (136.0 mg/dl) contained a significantly higher concentration of lactic acid than that from the large follicles (85.3 mg/dl). The progesterone concentrations were not significantly different among the fluid from the three group of follicles and the umbilical serum: however, the estradiol 17-beta concentrations of the follicular fluid increased with the size of the follicle (14.3 and 34.6 ng/ml for small and large follicles, respectively). These results offer new information concerning whale reproductive physiology, especially for improvement of in vitro oocyte maturation and related technologies in whales.

Effect of human granulosa cell co-culture using standard culture media on the maturation and fertilization potential of immature human oocytes

OBJECTIVE

To determine whether culture of immature human oocytes with and without autologous cumulus cells (CC) in standard culture medium would provide additional oocytes for use in IVF procedures.

DESIGN

Prospective study.

SETTING

Hospital-based IVF practice.

PATIENT(S)

Sixty-one women undergoing 62 IVF-embryo transfer procedures between August 2004 and June 2005.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Oocyte maturation after culture with and without CC, oocyte fertilization, and zygote cleavage.

RESULT(S)

Culture with CC did not alter the maturation rate for metaphase I (M I) oocytes to the metaphase II (M II) stage. Germinal vesicle (GV) stage oocytes cultured with CC matured at a significantly higher rate than did GV oocytes cultured without CC. Although acceptable fertilization rates were obtained (62.1%), "usable" embryo yield was very low (13.0%).

CONCLUSION(S)

This study demonstrated good maturation of M I oocytes but poor maturation of GV oocytes in standard culture medium. Of the immature oocytes that did mature, were fertilized, and cleaved to embryos, only a very small number were actually suitable for patient use. Therefore, these extended culturing techniques were inefficient in maturing and providing additional oocytes/embryos for patient use. The use of specialized in vitro maturation medium may improve the utility of this process.

Blastocyst production by in vitro maturation and development of porcine oocytes in defined media following intracytoplasmic sperm injection

The present study was carried out to establish porcine defined IVP. In Experiments 1 and 2, we investigated the efficacy of additional 0.6 mM cystine and/or 100 µM cysteamine (Cys) to a defined TCM199 maturation medium with regard to the intracellular glutathione (GSH) concentration and the developmental competence of in vitro matured porcine oocytes following intracytoplasmic sperm injection (ICSI). The control medium was a modified TCM199 containing 0.05% (w/v) polyvinyl alcohol (PVA). Cys and/or cystine were added to the control medium. The control group and immature oocytes (presumptive germinal vesicle oocytes; GV) were prepared for GSH assay. In Experiment 3, the efficacy of epidermal growth factor (EGF) addition to a modified porcine zygote medium (mPZM) for in vitro culture (IVC) medium was investigated on embryonic development and the mean cell number of blastocysts following ICSI. As a positive or negative control, 0.3% BSA (mPZM-3) or 0.3% PVA (mPZM-4), respectively, was added to the base medium. The defined IVC medium was supplemented with 5 or 10 ng/ml EGF. In Experiment 1, no significant difference was found in the rates of cleavage (31.4–64.3%) and blastocyst formation (6.5–22.9%) among the treatment and control groups. The mean cell numbers per blastocyst ranged from 30 to 48 among the groups without significant differences. However, in Experiment 2, the intracellular GSH concentrations in the oocytes cultured in the medium supplemented with 100 µM Cys (9.6 pmol/oocyte) or Cys + cystine (9.9 pmol/oocyte) were significantly (p < 0.05) higher than the control (2.5 pmol/oocyte) and 0.6 mM cystine (6.5 pmol/oocyte) groups, but not different from the GV group (9.0 pmol/oocyte). The GSH concentration in the cystine group was also significantly (p < 0.05) higher than that in the control group, but not different from the GV group. In Experiment 3, the rates of cleavage and blastocyst formation and the mean cell numbers of blastocysts were not significantly different among the groups. However, the addition of 5 ng/ml EGF into the mPZM-4 resulted in a significantly (p < 0.05) higher blastocyst rate per cleaved embryo than the other two defined groups (mPZM-4 + 5 ng/ml: 48.6%, mPZM-4 and mPZM-4 +10 ng/ml: 23.4% and 23.1%, respectively).

The present results indicate that the addition of Cys to a defined medium for in vitro maturation (IVM) of porcine oocytes increases intracellular GSH concentration. Further addition of cystine into the IVM medium containing 100 µM Cys is not necessary and TCM199 plus Cys (100 µM) could be used as a defined IVM medium for porcine oocytes. The addition of 5 ng/ml EGF to a defined IVC medium has enhanced subsequent development after ICSI. This study shows that porcine blastocysts can be produced by defined media throughout the steps of IVP (IVM, ICSI and IVC).

Improved fertilization and embryo development resulting in birth of live piglets after intracytoplasmic sperm injection and in vitro culture in a cysteine-supplemented medium

The effects of cysteine treatment on fertilization rate, intracellular concentration of glutathione, and embryo development in vitro and after embryo transfer were examined following intracytoplasmic sperm injection (ICSI) of in vitro-matured porcine oocytes using a piezo drive unit. Culture of presumed zygotes after ICSI with 1.71-3.71 mM cysteine for 3-12h improved (P<0.05) fertilization rates as compared to treatment with 0.57 mM cysteine or to controls (0mM) (56 to 68%, 48%, 35%, respectively). Extension of treatment time with cysteine beyond 3h did not further increase fertilization rates, suggesting that cysteine promoted early developmental events after ICSI (e.g. decondensation of sperm chromatin). There was no effect of cysteine supplementation on oocyte glutathione levels after ICSI. Pretreatment of spermatozoa for 3h with 1.71 mM cysteine did not improve fertilization rates. The incidence of blastocysts formation when cultured in 1.71 mM cysteine for 3h after ICSI was 31%, which was higher (P<0.05) than controls (18%). Transfer of 20-38 embryos cultured with 1.71 mM cysteine for 3h after ICSI to each of seven recipients yielded three deliveries with an average litter size of 4.0. We concluded that cysteine supplementation for the first 3h after ICSI improved fertilization and embryo development rates, with no influence on glutathione levels in oocytes, and that the cysteine-treated ICSI embryos developed to full term. The study also showed that porcine oocytes matured in a chemically defined medium had the ability for full-term development after piezo-ICSI without additional treatments for oocyte activation.

In vitro maturation of pig oocytes with different media, hormone and meiosis inhibitors

This study evaluated in vitro maturation of pig oocytes in two maturation media (TCM199 and NCSU23) supplemented with 10% porcine follicular fluid (pFF) or 0.1% polyvinyl alcohol (PVA) and four hormonal treatments. The best media was then used to evaluate the effect of reversible meiosis inhibitors cycloheximide (5 microgram/ml) [DOSAGE ERROR CORRECTED]and butyrolactone I (12.5M) on the maturation of pig oocytes was evaluated. After maturation for 44 h, the oocytes were fixed, stained, and examined under epifluorescence microscopy. The comparison of the proportion of oocytes in metaphase II revealed that hormonal treatment 2(incubation for 22 h - 10 ng EGF/ml, 10 IU hCG/ml and 10 IU eCG/ml, followed by incubation for 22 h - 10 ng EGF/ml) presented higher repeatability percentages: TCM+ PVA (54.5% - 61/112); TCM+ pFF (65.0% - 63/97);NCSU23 + PVA (54.6% - 65/119), and NCSU23 + pFF (58.1% - 61/105). The comparison of maturation media showed that TCM199 presented more constant results than NCSU23. Regarding supplementation with pFF or PVA, TCM199 with pFF presented better results. The comparison between butyrolactone I and cycloheximide demonstrated that both drugs effectively inhibited meiosis; however, only cycloheximide presented metaphase II percentages similar to the control (70.29% and 75.49%, respectively). In conclusion, it is recommended the use of TCM199 medium supplemented with pFF and hormonal treatment with 10 ng EGF/ml, 10 UI hCG/mland 10 UI eCG/ml during the first 22 h and more 22 h with 10 ng EGF/ml for the pig oocytes maturation. Butyrolactone I and cycloheximide effectively arrested/resumpted maturation; however, the oocytes percentages in metaphase II was the same for both cycloheximide and the control groups.

Effects of in vitro maturation of monkey oocytes on their developmental capacity

The study of in vitro maturation (IVM) of rhesus monkey oocytes has important implications for biomedical research and human infertility treatment. In vitro-matured rhesus monkey oocytes show much less developmental potential than IVM oocytes of other species. Since about 1980 when rhesus monkey IVM, in vitro fertilization (IVF) and in vitro embryo culture (IVC) systems were established, numerous efforts have been made to improve the developmental competence of oocytes and to understand the mechanisms regulating oocyte maturation. This review describes recent progress in this area, particularly the effects of factors such as steroid hormones, energy substrates, amino acids, ovarian follicle status, maternal age and breeding season on the developmental competence, gene expression patterns and genome integrity of rhesus IVM oocytes.

Developmental capacity of Antarctic minke whale (Balaenoptera bonaerensis) vitrified oocytes following in vitro maturation, and parthenogenetic activation or intracytoplasmic sperm injection

The present study investigated the effects of the sexual maturity of oocyte donors on in vitro maturation (IVM) and the parthenogenetic developmental capacity of fresh minke whale oocytes. The effects of cytochalasin B (CB) pretreatment and two types of cryoprotectant solutions (ethylene glycol (EG) or ethylene glycol and dimethylsulfoxide (EG + DMSO)) on the in vitro maturation of vitrified immature whale oocytes were compared, and the developmental capacity of vitrified immature whale oocytes following IVM and intracytoplasmic sperm injection examined (ICSI). The maturation rate did not differ significantly with sexual maturity (adult, 60.9%; prepubertal, 53.1%), but the parthenogenetic activation rate of oocytes from adult donors (76.7%) was significantly higher (p < 0.05) than that of oocytes from prepubertal donors (46.4%). The maturation rates after vitrification and warming were not significantly different between the EG (22.2%) and EG + DMSO groups (30.2%), or between the CB-treated (30.4%) and non-CB-treated groups (27.3%). These results indicate that parthenogenetic activation of in vitro matured oocytes from adult minke whales was superior to that from prepubertal whales, but that the developmental capacity of the whale oocytes after parthenogenetic activation or ICSI was still low. The present study also showed that CB treatment before vitrification and two kinds of cryoprotectants did not improve the IVM rate following the vitrification of immature whale oocytes.

Cysteamine or β-mercaptoethanol added to a defined maturation medium improves blastocyst formation of porcine oocytes after intracytoplasmic sperm injection

The present study was carried out to investigate the effect of adding 100 microM cysteamine (Cys) or 100 microM beta-mercaptoethanol (beta-ME) to a defined maturation medium on in vitro maturation (IVM), and fertilization and developmental competence of in vitro matured porcine oocytes following intracytoplasmic sperm injection (ICSI). The two control media for IVM culture were modified TCM199 containing 10% (v/v) porcine follicular fluid (pFF) or 0.05% (w/v) polyvinyl alcohol (PVA), and Cys or beta-ME was supplemented to the PVA-control medium. There was no significant difference in the proportions of in vitro matured oocytes among the four treatment groups (94.5-98.4%). The percentages of pronuclear formation (51.0-64.2%) after ICSI were also not significantly different among the four groups. The cleavage rate (72.8%) in the oocytes treated with Cys showed no significant difference compared with those of the two control media containing pFF (72.2%) or PVA (61.5%), but was higher (P<0.05) than that in the oocytes treated with beta-ME (56.3%). However, the rates of blastocyst formation of Cys (36.7%), beta-ME (27.1%) and pFF (31.4%) were higher (P<0.05) than that using the control medium containing PVA (15.6%). The mean cell number of blastocysts ranged from 42 to 52 among the four groups, without significant differences. In conclusion, the addition of Cys or beta-ME to a defined maturation medium enhanced blastocyst formation after ICSI, to a level similar to that achieved by adding pFF.

Effects of dithiothreitol and boar on pronuclear formation and embryonic development following intracytoplasmic sperm injection in pigs

The objective of this study was to improve normal fertilization, male pronuclear formation and embryonic development following intracytoplasmic injection of dithiothreitol (DTT)-treated boar spermatozoa. To determine the effect of DTT treatment, frozen-thawed boar spermatozoa were treated with DTT for 0, 10, 30, and 60 min, and injected into porcine oocytes. The effects of DTT and male difference on normal fertilization and embryonic development were investigated. The mean normal fertilization rate in the groups treated with DTT for 30 min (73.8%) and 60 min (74.9%) was higher (P < 0.05) than that in the control group (49.3%). The mean blastocyst formation rate in the group treated with DTT for 30 min (23.2%) was higher (P < 0.05) than that in the other groups (8.7-10.9%). Among boars there was no difference in normal fertilization, but there was a significant difference between the non-treated and the DTT-treated groups. The mean rate of blastocyst formation was different (P < 0.05) among boars, and between the non-treated and DTT-treated groups. The mean number of cells in blastocysts was similar among the boars and between the non-treated and the DTT-treated groups. In conclusion, DTT treatment for 30 min increased the rate of normal fertilization and embryonic development to the blastocyst stage. Furthermore, the rate of blastocyst formation of oocytes injected with spermatozoa differed among boars.

In Vitro Culture Conditions Using Chemically Defined Media for In Vitro Matured and Intracytoplasmically Inseminated Porcine Oocytes

The present study investigated in vitro culture methods [droplet and Well of the Well (WOW)] using semi-defined and defined media [modified porcine zygote medium (mPZM)] and the additional effects of insulin on in vitro matured and intracytoplasmically inseminated porcine oocytes. In Experiment 1, in vitro matured and intracytoplasmically inseminated porcine oocytes were cultured for 6 days in the following four groups: 1) mPZM-3 (containing bovine serum albumin) + droplet (30 mul), 2) mPZM-3 + WOW, 3) mPZM-4 (containing polyvinyl alcohol) + droplet, and 4) mPZM-4+ WOW. The culture media (mPZM-3 and mPZM-4) and methods (droplet and WOW) did not significantly affect the cleavage rate, but the blastocyst rate of the oocytes cultured in mPZM-3 was significantly (P<0.01) higher than that of mPZM-4 (20.1 and 9.4%, respectively). The blastocyst rates as percentages of the cleaved oocytes (51.8 and 16.9%) and the hatched blastocyst rate as percentages of the number of blastocysts (12.3 and 2.2%) were also significantly (P<0.01) higher in mPZM-3 compared with those in mPZM-4. There was significant interaction (P<0.05) between the two main factors; the effects of the culture media and methods on the rate of hatched blasyocysts as percentages of the blastocysts produced and, the hatched blastocyst rate (20.3%) as percentages of the number of blastocysts produced in mPZM-3 were significantly (P<0.05) higher than in the other groups. In Experiment 2, the additional effects of insulin (100 ng/ml) in mPZM-3 and mPZM-4 media was investigated in the WOW culture system. Insulin addition did not improve cleavage, blastocyst formation, or the number of cells in blastocysts. However, as in Experiment 1, mPZM-3 resulted in a significantly higher blastocyst rate as percentages of the cleaved oocytes than mPZM-4 (33.9 and 18.4%). These results indicate that a chemically defined medium (mPZM-4) needs to be improved to provide more suitable culture conditions for in vitro development of in vitro matured and intracytoplasmically inseminated porcine oocytes. However, the WOW system may be a useful IVC method for blastocyst development of in vitro matured porcine oocytes following ICSI when a semi-defined medium (mPZM-3) is used.