Effect of sperm entry on blastocyst development after in vitro fertilization and intracytoplasmic sperm injection - mouse model

Animal and vegetal materials of mouse oocytes segregate at first zygotic cleavage: a simple mechanism that makes the two-cell blastomeres differ reciprocally from the start

Recent advances in embryology have shown that the sister blastomeres of two-cell mouse and human embryos differ reciprocally in potency. An open question is whether the blastomeres became different as opposed to originating as different. Here we wanted to test two relevant but conflicting models: one proposing that each blastomere contains both animal and vegetal materials in balanced proportions because the plane of first cleavage runs close to the animal-vegetal axis of the fertilized oocyte (meridional cleavage); and the other model proposing that each blastomere contains variable proportions of animal and vegetal materials because the plane of the first cleavage can vary - up to an equatorial orientation - depending on the topology of fertilization. Therefore, we imposed the fertilization site in three distinct regions of mouse oocytes (animal pole, vegetal pole, equator) via ICSI. After the first zygotic cleavage, the sister blastomeres were dissociated and subjected to single-cell transcriptome analysis, keeping track of the original pair associations. Non-supervised hierarchical clustering revealed that the frequency of correct pair matches varied with the fertilization site (vegetal pole > animal pole > equator), thereby, challenging the first model of balanced partitioning. However, the inter-blastomere differences had similar signatures of gene ontology across the three groups, thereby, also challenging the competing model of variable partitioning. These conflicting observations could be reconciled if animal and vegetal materials were partitioned at the first cleavage: an event considered improbable and possibly deleterious in mammals. We tested this occurrence by keeping the fertilized oocytes immobilized from the time of ICSI until the first cleavage. Image analysis revealed that cleavage took place preferentially along the short (i.e. equatorial) diameter of the oocyte, thereby partitioning the animal and vegetal materials into the two-cell blastomeres. Our results point to a simple mechanism by which the two sister blastomeres start out as different, rather than becoming different.

Comparison of Development and Antioxidative Ability in Fertilized Crossbred (Yorkshire × Landrace × Duroc) Oocytes Using Duroc and Landrace Sperm

Pig production through crossbreeding methods is a pillar of the swine industry; however, research on the fertilization ability of male pigs in crossbreeds is lacking. Therefore, this study investigated the effects of Duroc sperm (DS) and Landrace sperm (LS) on fertility in Yorkshire × Landrace × Duroc (YLD) oocytes. Sperm were collected from the Duroc and Landrace species, and sperm characteristics, viability, and acrosome reactions were analyzed using flow cytometry. Oocytes were collected from YLD ovaries, and the fertility of DS and LS was determined using in vitro fertilization (IVF). Reactive oxygen species (ROS) and antioxidative abilities were analyzed using H2DCFDA and a Cell Tracker Red assay. Pluripotency (OCT4, SOX2, and NANOG), antioxidative (SOD1, SOD2, CAT, and GPx1), apoptotic (Bax and Bcl-2), and cell cycle-related (Cdc2 and CCNB1) genes were detected using quantitative reverse transcription polymerase chain reaction (qRT-PCR) in oocytes fertilized with sperm. The results showed no significant difference in viability or acrosome reaction between DS and LS. ROS levels were significantly lower in the LS group than in the DS group, whereas glutathione (GSH) levels in the embryo did not significantly differ between the DS and LS groups. The OCT4, GPx1, and Cdc2 mRNA expression levels were significantly higher in the LS than DS groups. Blastocyst formation was significantly higher in the LS than DS groups. ROS levels were reduced, and blastocyte formation was increased in LS-obtained embryos. In conclusion, these results provide a fundamental understanding of using Landrace semen in the three-way crossbreeding of YLD pigs.

Methyl 3,4-dihydroxybenzoate alleviates oxidative damage in granulosa cells by activating Nrf2 antioxidant pathway

Oxidative damage induced granulosa cells (GCs) apoptosis was considered as a significant cause of compromised follicle quality, antioxidants therapy has emerged as a potential method for improving endometriosis pregnancy outcomes. Here, we found that GCs from endometriosis patients show increased oxidative stress level. Methyl 3,4-dihydroxybenzoate (MDHB), a small molecule compound that is extracted from natural plants, reversed tert-butyl hydroperoxide (TBHP) induced GCs oxidative damage. Therefore, the aim of this study was to assess the protective effect of MDHB for GCs and its potential mechanisms. TUNEL staining and immunoblotting of cleaved caspase-3/7/9 showed MDHB attenuated TBHP induced GCs apoptosis. Mechanistically, MDHB treatment decreased cellular and mitochondria ROS production, improved the mitochondrial function by rescuing the mitochondrial membrane potential (MMP) and ATP production. Meanwhile, MDHB protein upregulated the expression of vital antioxidant transcriptional factor Nrf2 and antioxidant enzymes SOD1, NQO1 and GCLC to inhibited oxidative stress state, further beneficial to oocytes and embryos quality. Therefore, MDHB may represent a potential drug candidate in protecting granulosa cells in endometriosis, which can improve pregnancy outcomes for endometriosis-associated infertility.

Fertilization and Cleavage Axes Differ In Primates Conceived By Conventional (IVF) Versus Intracytoplasmic Sperm Injection (ICSI)

With nearly ten million babies conceived globally, using assisted reproductive technologies, fundamental questions remain; e.g., How do the sperm and egg DNA unite? Does ICSI have consequences that IVF does not? Here, pronuclear and mitotic events in nonhuman primate zygotes leading to the establishment of polarity are investigated by multidimensional time-lapse video microscopy and immunocytochemistry. Multiplane videos after ICSI show atypical sperm head displacement beneath the oocyte cortex and eccentric para-tangential pronuclear alignment compared to IVF zygotes. Neither fertilization procedure generates incorporation cones. At first interphase, apposed pronuclei align obliquely to the animal-vegetal axis after ICSI, with asymmetric furrows assembling from the male pronucleus. Furrows form within 30° of the animal pole, but typically, not through the ICSI injection site. Membrane flow drives polar bodies and the ICSI site into the furrow. Mitotic spindle imaging suggests para-tangential pronuclear orientation, which initiates random spindle axes and minimal spindle:cortex interactions. Parthenogenetic pronuclei drift centripetally and assemble astral spindles lacking cortical interactions, leading to random furrows through the animal pole. Conversely, androgenotes display cortex-only pronuclear interactions mimicking ICSI. First cleavage axis determination in primates involves dynamic cortex-microtubule interactions among male pronuclei, centrosomal microtubules, and the animal pole, but not the ICSI site.

Production of inbred offspring by intracytoplasmic sperm injection of oocytes from juvenile female mice

The aim of the present study was to determine whether the use of oocytes from juvenile female mice would improve the efficiency of intracytoplasmic sperm injection (ICSI). In the present study, 15 adult and 14 juvenile C57BL6/J female mice were superovulated, with 17.8 oocytes per mouse harvested from adults, significantly lower than the 40.2 harvested from juveniles (P<0.01). Sixty and 233 oocytes were harvested from C57BL/6J adult and juvenile mice respectively, activated in 10mM SrCl2+5μgmL-1 cytochalasin B for 5-6h and cultured in potassium simplex optimisation medium (KSOM) for 3.5 days, with no differences in morula and blastocyst rates between groups (91.7% vs 96.6%; P>0.05). Twelve hours after injection of human chorionic gonadotrophin, oocytes were harvested from C57BL/6J juvenile mice into KSOM, randomly divided into groups and activated with the same method mentioned above at 0, 2, 4 or 6h and then cultured in KSOM for 3.5 days. There was no significant difference in morula and blastocyst rates among the different groups (P>0.05). Oocytes from juvenile mice activated in 10mM SrCl2 for 2h were subjected to ICSI and the rates of pronuclear formation and Day 1 cleavage were significantly improved compared with the control group (P<0.01). ICSI combined with activation of oocytes from inbred mouse strains (C57BL/6J, C57BL/6N and 129Svev) successfully produced pups. The fertility of some these mice resulting from ICSI was tested, and the animals proved fertile. In conclusion, superovulated juvenile mice can yield more useable oocytes than adult mice, but additional activation is essential for full development of ICSI oocytes harvested from juvenile inbred mice.

Reconstruction of mammalian oocytes by germinal vesicle transfer: A systematic review

Nuclear transfer procedures have been recently applied for clinical and research targets as a novel assisted reproductive technique and were used for increasing the oocyte activity during its growth and maturation. In this review, we summarized the nuclear transfer technique for germinal vesicle stage oocytes to reconstruct the maturation of them. Our study covered publications between 1966 and August 2017. In result utilized germinal vesicle transfer techniques, fusion, and fertilization survival rate on five different mammalian species are discussed, regarding their potential clinical application. It seems that with a study on this method, there is real hope for effective treatments of old oocytes or oocytes containing mitochondrial problems in the near future.

Influence of the insemination method on the outcomes of elective blastocyst culture

Objective

The aim of this study was to explore the effects of the insemination method on the outcomes of elective blastocyst culture.

Methods

We retrospectively analyzed the outcomes of elective blastocyst culture performed between January 2011 and December 2014.

Results

There were 2,003 cycles of conventional in vitro fertilization (IVF) and 336 cycles of intracytoplasmic sperm injection (ICSI), including 25,652 and 4,164 embryos that underwent sequential blastocyst culture, respectively. No significant differences were found in the female patients' age, basal follicle-stimulating hormone level, basal luteinizing hormone level, body mass index, number of oocytes, maturity rate, fertilization rate, or good-quality embryo rate. However, the blastocyst formation rate and embryo utilization rate were significantly higher in the conventional IVF group than in the ICSI group (54.70% vs. 50.94% and 51.09% vs. 47.65%, respectively, p<0.05). The implantation/pregnancy rate (IVF, 50.93%; ICSI, 55.10%), miscarriage rate (IVF, 12.57%; ICSI, 16.29%), and live birth rate (IVF, 42.12%; ICSI, 44.08%) were similar (p>0.05). No cycles were canceled due to the formation of no usable blastocysts.

Conclusion

Although the fertilization method had no effect on clinical outcomes, the blastocyst formation rate and embryo utilization rate in the ICSI group were significantly lower than those observed in the conventional IVF group. Therefore, more care should be taken when choosing to perform blastocyst culture in ICSI patients.

Influence of radiofrequency-electromagnetic waves from 3rd-generation cellular phones on fertilization and embryo development in mice

The purpose of this study was to evaluate the effects of 3rd-generation (3G) cellular phone radiofrequency-electromagnetic wave (RF-EMW) exposure on fertilization and embryogenesis in mice. Oocytes and spermatozoa were exposed to 3G cellular phone RF-EMWs, 1.95 GHz wideband code division multiple access, at a specific absorption rate of 2 mW/g for 60 min, or to sham exposure. After RF-EMW exposure, in vitro fertilization and intracytoplasmic sperm injection were performed. Rates of fertilization, embryogenesis (8-cell embryo, blastocyst), and chromosome aberration were compared between the combined spermatozoa and oocyte groups: both exposed, both non-exposed, one exposed, and the other non-exposed. Rates of fertilization, embryogenesis, and blastocyst formation did not change significantly across the four groups. Considering that the degree of exposure in the present study was ≥100 times greater than daily exposure of human spermatozoa and even greater than daily exposure of oocytes, the present results indicate safety of RF-EMW exposure in humans. Bioelectromagnetics. 38:466-473, 2017. © 2017 Wiley Periodicals, Inc.

Performing ICSI with commercial microinjection pipettes enhanced pregnancy rates

BACKGROUND/AIM

Many technical factors can affect intracytoplasmic sperm injection (ICSI) outcomes. The role of the injection micropipette could be of vital importance in ICSI programs. The main goal was to compare ICSI pregnancy outcomes between commercial and home-made injection micropipettes in a large population with male factor infertility.

MATERIALS AND METHODS

Five-hundred and eleven ICSI cycles with severe male factor were included in this retrospective study. ICSI cycles were divided into two groups: A (home-made micropipettes, n = 267) and B (commercial micropipettes, n = 244). Rates of fertilization, embryo formation, and chemical and clinical pregnancies were compared between the groups. The independent samples t-test, chi-square test, and Fisher's exact test were used, whenever appropriate, for statistical analysis.

RESULTS

A total of 3621 MII oocytes were retrieved, of which 2003 were fertilized. The rate of normal fertilization was significantly higher in group A (57.9%) compared to group B (52.5%). However, the rate of embryo formation showed an increase in group B compared to group A (90.4% and 85.9%, respectively, P = 0.002). In addition, the clinical pregnancy outcomes improved in group B.

CONCLUSION

Our findings indicate that clinical pregnancy improves when commercial injection micropipettes are used in ICSI programs.

In vitro fertilization (IVF) in mammals: epigenetic and developmental alterations. Scientific and bioethical implications for IVF in humans

The advent of in vitro fertilization (IVF) in animals and humans implies an extraordinary change in the environment where the beginning of a new organism takes place. In mammals fertilization occurs in the maternal oviduct, where there are unique conditions for guaranteeing the encounter of the gametes and the first stages of development of the embryo and thus its future. During this period a major epigenetic reprogramming takes place that is crucial for the normal fate of the embryo. This epigenetic reprogramming is very vulnerable to changes in environmental conditions such as the ones implied in IVF, including in vitro culture, nutrition, light, temperature, oxygen tension, embryo-maternal signaling, and the general absence of protection against foreign elements that could affect the stability of this process. The objective of this review is to update the impact of the various conditions inherent in the use of IVF on the epigenetic profile and outcomes of mammalian embryos, including superovulation, IVF technique, embryo culture and manipulation and absence of embryo-maternal signaling. It also covers the possible transgenerational inheritance of the epigenetic alterations associated with assisted reproductive technologies (ART), including its phenotypic consequences as is in the case of the large offspring syndrome (LOS). Finally, the important scientific and bioethical implications of the results found in animals are discussed in terms of the ART in humans.

Deposition of the spermatozoon in the human oocyte at ICSI: impact on oocyte survival, fertilization and blastocyst formation

PURPOSE

To evaluate whether the deposition of the spermatozoon in the human oocyte at ICSI has any effect on oocyte survival, fertilization, blastocyst development and quality.

METHODS

In a prospective study, including 78 ICSI cycles, sibling oocytes were injected with "no intention" (group A, standard ICSI, n = 393) or "intention" to deposit the spermatozoon under the cortex (group B, n = 354). Outcome parameters were oocyte survival and fertilization, as well as blastocyst formation and quality.

RESULTS

Depositing the sperm under the cortex of the oocyte was not always successful for its final position, therefore, group B was divided into three subgroups: B1 successful deposition (119 oocytes, 33.6 % of oocytes in group B); B2 initially successful but spermatozoon spontaneously relocated after 2 min (136 oocytes, 38.4 %); and B3 unsuccessful deposition (99 oocytes, 28.0 %). Group A and B were compared on an intention-to-treat basis. Additionally, A, B1, B2 and B3 were also compared. The oocyte survival and fertilization, blastocyst and top-quality blastocyst developmental rates were not significantly different.

CONCLUSIONS

The procedure of depositing the spermatozoon intentionally under the oocyte cortex demanded high technical skills. Successful positioning was only obtained in 34 % of the attempts. We obtained no evidence of improved oocyte survival and fertilization, blastocyst formation and quality when the spermatozoon was permanently positioned under the oocyte cortex. Taken together, depositing the spermatozoon under the oocyte cortex is not recommended for routine ICSI application.

Assessment of nuclear transfer techniques to prevent the transmission of heritable mitochondrial disorders without compromising embryonic development competence in mice

To evaluate and compare mitochondrial DNA (mtDNA) carry-over and embryonic development potential between different nuclear transfer techniques we performed germinal vesicle nuclear transfer (GV NT), metaphase-II spindle-chromosome-complex (MII-SCC) transfer and pronuclear transfer (PNT) in mice. No detectable mtDNA carry-over was seen in most of the reconstructed oocytes and embryos. No significant differences were seen in mtDNA carry-over rate between GV NT (n=20), MII-SCC transfer (0.29 ± 0.63; n=21) and PNT (0.29 ± 0.75; n=25). Blastocyst formation was not compromised after either PNT (88%; n=18) or MII-SCC transfer (86%; n=27). Further analysis of blastomeres from cleaving embryos (n=8) demonstrated undetectable mtDNA carry-over in all but one blastomere. We show that NT in the germ line is potent to prevent transmission of heritable mtDNA disorders with the applicability for patients attempting reproduction.