Use of oocytes selected by brilliant cresyl blue staining enhances rabbit cloned embryo development in vitro

Somatic Cell Nuclear Transfer in Rabbits

Somatic cell nuclear transfer (SCNT) is a technology that enables differentiated somatic cells to acquire a totipotent state, thus making it of great value in developmental biology, biomedical research, and agricultural applications. Rabbit cloning associated with transgenesis has the potential to improve the applicability of this species for disease modeling, drug testing, and production of human recombinant proteins. In this chapter, we introduce our SCNT protocol for the production of live cloned rabbits.

Lycopene Reduces the In Vitro Aging Phenotypes of Mouse Oocytes by Improving Their Oxidative Status

Simple Summary

Ovulation is the process of oocyte release from the ruptured mature ovarian follicle into the oviduct. Fertilization usually occurs within 10 h post-ovulation in most mammals. If fertilization is delayed, the oocyte viability and quality will decrease, with many deteriorative changes in oocyte phenotype due to oxidative stress. This process is termed postovulatory aging. Postovulatory aging is a major problem that limits the success of many assisted reproductive technologies. Lycopene is a red carotenoid dye found within tomatoes and other fruits and vegetables. Lycopene has been reported to have a strong free-radical scavenging ability. our data showed beneficial effects of lycopene supplementation of in vitro maturation media during in vitro aging of mouse oocytes by reducing the oxidative stress damages that led to their apoptosis. The present study introduces lycopene as a natural supplement to reduce the postovulatory aging of mammalian oocytes.

Abstract

Postovulatory aging is a major problem that limits the success of many assisted reproductive technologies (ARTs). Oxidative stress is a leading cause of oocyte aging. This study investigated the effects of lycopene supplementation of in vitro maturation (IVM) medium during the aging of mouse oocytes on the oocytes’ morphology and oxidative stress status. Mouse cumulus-oocyte complexes (COCs) were collected and cultured in the IVM medium either for 17 h, (freshly matured oocytes), or for 48 h, (in vitro-aged oocytes), with or without lycopene. The rate of fragmented and degenerated oocytes and the oocyte levels of hydrogen peroxide (H₂O₂), malondialdehyde (MDA), total antioxidant capacity (TAC), reduced glutathione (GSH), catalase (CAT), and superoxide dismutase (SOD) were estimated and compared. Oocytes aged with 200 nM lycopene revealed significantly less fragmentation and degeneration, lower H₂O₂ and MDA levels, and higher TAC, GSH and SOD levels than those aged without lycopene. CAT levels were unchanged by lycopene treatment. Taken together, our data showed beneficial effects of lycopene during in vitro aging of mouse oocytes by reducing the oxidative stress damages that lead to their apoptosis. The present study introduces lycopene as a natural supplement to reduce the postovulatory aging-dependent abnormalities of mammalian oocytes.

Extracellular vesicles from seminal plasma improved development of in vitro-fertilized mouse embryos

In vitro fertilization (IVF) has wide application in human infertility and animal breeding. It is also used for research on reproduction, fertility and development. However, IVF embryos are still inferior to their in vivo counterparts. Some substances in seminal plasma appear to have important roles in embryo development, and during the traditional IVF procedure, the seminal plasma is washed away. In this study, extracellular vesicles (EVs) were concentrated from seminal plasma by ultracentrifugation, visualized using transmission electron microscopy, and particle size distributions and concentrations were determined with a NanoSight particle analyzer. We found particles of various sizes in the seminal plasma, the majority having diameters ranging from 100 to 200 nm and concentrations of 6.07 × 10¹⁰ ± 2.91 × 10⁹ particles/ml. Addition of seminal plasma EVs (SP-EVs) to the IVF medium with mouse oocytes and sperm significantly increased the rate of blastocyst formation and the inner cell mass (ICM)/trophectoderm (TE) cell ratio, and reduced the apoptosis of blastocysts. Our findings provide new insights into the role of seminal plasma EVs in mediating embryo development and it suggests that SP-EVs may be used to improve the developmental competence of IVF embryos, which has important significance for assisted reproduction in animals and humans.

Strategies to Improve the Efficiency of Somatic Cell Nuclear Transfer

Mammalian oocytes can reprogram differentiated somatic cells into a totipotent state through somatic cell nuclear transfer (SCNT), which is known as cloning. Although many mammalian species have been successfully cloned, the majority of cloned embryos failed to develop to term, resulting in the overall cloning efficiency being still low. There are many factors contributing to the cloning success. Aberrant epigenetic reprogramming is a major cause for the developmental failure of cloned embryos and abnormalities in the cloned offspring. Numerous research groups attempted multiple strategies to technically improve each step of the SCNT procedure and rescue abnormal epigenetic reprogramming by modulating DNA methylation and histone modifications, overexpression or repression of embryonic-related genes, etc. Here, we review the recent approaches for technical SCNT improvement and ameliorating epigenetic modifications in donor cells, oocytes, and cloned embryos in order to enhance cloning efficiency.

Effects of changing culture medium on preimplantation embryo development in rabbit

Many studies have focused on the optimization of the composition of embryo culture medium; however, there are few studies involving the effect of a culture medium changing procedure on the preimplantation development of embryos. In this study, three groups were designed: a non-renewal group, a renewal group and a half-renewal group. The levels of reactive oxygen species (ROS), apoptotic index, blastocyst ratio and blastocyst total cell number were analyzed in each group. The results showed that the ROS level and the apoptotic index of blastocyst in the non-renewal group were significantly higher than in the renewal group and the half-renewal group (P < 0.05). The blastocyst ratio and blastocyst total cell number were significantly higher in the half-renewal group than that in non-renewal group and the renewal group (P < 0.05). These results demonstrated that the procedure of changing the culture medium influenced ROS level, apoptotic index, blastocyst ratio and total cell number of blastocysts. In addition, the result suggested that changing the culture medium may lead to a loss of important regulatory factors for embryos, while not changing the culture medium may lead to the accumulation of toxic substances. Half-renewal can alleviate the defects of both no renewal and renewal, and benefit embryo development. This study will be of high value as a reference for the optimization of embryo culture in vitro, and is very significant for assisted reproduction.

Sperm-borne small RNAs improve the developmental competence of pre-implantation cloned embryos in rabbit

The low efficiency of somatic cell nuclear transfer (SCNT) greatly limits its application. Compared with the fertilized embryo, cloned embryos display abnormal epigenetic modification and other inferior developmental properties. In this study, small RNAs were isolated, and miR-34c and miR-125b were quantified by real-time PCR; results showed that these micro-RNAs were highly expressed in sperm. The test sample was divided into three groups: one was the fertilized group, one was the SCNT control group (NT-C group), and the third group consisted of SCNT embryos injected with sperm-borne small RNA (NT-T group). The level of tri-methylation of lysine 9 on histone H3 (H3K9me3) at the 8-cell stage was determined by immunofluorescence staining, and the cleavage ratio, blastocyst ratio, apoptotic cell index of the blastocyst and total cell number of blastocysts in each group were analyzed. Results showed that the H3K9me3 level was significantly higher in the NT-C group than in the fertilized group and the NT-T group. The apoptosis index of blastocysts in the NT-C group was significantly higher than that in the fertilized group and the NT-T group. The total cell number of SCNT embryos was significantly lower than that of fertilized embryos, and injecting sperm-borne small RNAs could significantly increase the total cell number of SCNT blastocysts. Our study not only demonstrates that sperm-borne small RNAs have an important role in embryo development, but also provides a new strategy for improving the efficiency of SCNT in rabbit.

Extracellular vesicles and melatonin benefit embryonic develop by regulating reactive oxygen species and 5-methylcytosine

Embryo culture conditions are crucial as they can affect embryo quality and even offspring. Oviductal extracellular vesicles (EVs) long been considered a major factor influencing interactions between the oviduct and embryos, and thus its absence is associated with inferior embryonic development in in vitro culture. Herein, we demonstrated that melatonin is present in oviduct fluids and oviduct fluid-derived EVs. Addition of either EVs (1.87 × 10¹¹ particles/mL) or melatonin (340 ng/mL) led to a significant downregulation of reactive oxygen species (ROS) and 5-methylcytosine (5-mC), as well as an increase in the blastocyst rate of embryos, which was inhibited by the addition of luzindole-a melatonin receptor agonist. A combination of EVs (1.87 × 10¹⁰ particles/mL) and melatonin (at 34.3 pg/mL) led to the same results as well as a significant decrease in the apoptosis index and increase in the inner cell mass (ICM)/trophectoderm (TE) index. These results suggest that an EV-melatonin treatment benefits embryonic development. Our findings provide insights into the role of EVs and melatonin during cell communication and provide new evidence of the communication between embryos and maternal oviduct.

Melatonin Protects Rabbit Somatic Cell Nuclear Transfer (SCNT) Embryos from Electrofusion Damage

The study’s objectives were to examine the effects of electrofusion on rabbit somatic cell nuclear transfer (SCNT) embryos, and to test melatonin as a protective agent against electrofusion damage to SCNT embryos. The levels of reactive oxygen species (ROS), the epigenetic state (H3K9me3), and the content of endoplasmic reticulum (ER) stress-associated transcripts (IRE-1 and CHOP) were measured. Melatonin was added during the preimplantation development period. The total blastocyst cell numbers were counted, and the fragmentation rate and apoptotic index were determined and used to assess embryonic development. Electrofusion increased (1) ROS levels at the 1-, 2-, 4-, and 8-cell stages; (2) H3K9me3 levels at the 2-, 4-, and 8-cell stage; and (3) the expression of IRE-1 and CHOP at the 8-cell, 16-cell, morula, and blastocyst stages. The treatment of SCNT embryos with melatonin significantly reduced the level of ROS and H3K9me3, and the expression levels of IRE-1 and CHOP. This treatment also significantly reduced the fragmentation rate and apoptotic index of blastocysts and increased their total cell number. In conclusion, the electrofusion of rabbit SCNT embryos induced oxidative stress, disturbed the epigenetic state, and caused ER stress, while melatonin reduced this damage. Our findings are of signal importance for improving the efficiency of SCNT and for optimizing the application of electrical stimulation in other biomedical areas.

Tauroursodeoxycholic acid (TUDCA) enhanced intracytoplasmic sperm injection (ICSI) embryo developmental competence by ameliorating endoplasmic reticulum (ER) stress and inhibiting apoptosis

PURPOSE

The objective of this study was to examine the effect of tauroursodeoxycholic acid (TUDCA) on intracytoplasmic sperm injection (ICSI) embryos by evaluating endoplasmic reticulum (ER) stress, apoptosis, and embryo developmental competence in vitro and in vivo.

METHODS

ER stress-associated genes and apoptosis-associated genes were measured and apoptosis index was analyzed. Embryo developmental competence was assessed in vitro and in vivo via the inner cell mass (ICM)/trophectoderm (TE) index, pregnancy and implantation rates, and birth rate.

RESULTS

The relative mRNA and protein expression of binding immunoglobulin protein (BIP) was significantly higher in the ICSI embryo group without TUDCA treatment (ICSI-C) than in the in vitro fertilization (IVF) group and in the ICSI embryo group with TUDCA treatment (200 μM) (ICSI-T), while TUDCA ameliorated ER stress in ICSI embryos. Embryos in the ICSI-C group showed a higher apoptosis index than those in the IVF group and ICSI-T group, and there was no significant difference between the IVF group and ICSI-T group. TUDCA can significantly improve ICSI embryo developmental competence in vitro and in vivo based on the ICM/TE index, pregnancy and implantation rates, and birth rate.

CONCLUSION

ICSI embryos manifested high ER stress and high apoptosis, while TUDCA ameliorated ER stress and reduced apoptosis in ICSI embryos. TUDCA can significantly improve the developmental competence of ICSI embryos in vitro and in vivo. This study provides a new idea for improving the efficiency of ICSI, and it will also have a positive effect on the development of assisted reproduction technologies for humans and other animals.