Abstract
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.
Highlights
Significant progress has been made in assisted reproduction techniques (ART) for the treatment of infertility ever since Louise Brown, the first test-tube baby, was successfully conceived by in vitro fertilization (IVF) in 1978.1 During the past 40 years, the number of infants conceived through IVF accounts for approximately 0.1% of the total global birth population.[2]
Recent research has highlighted that oviduct fluid plays an important role in the fertilization and development of preimplantation embryos.[31]
Normal embryonic development is disrupted under extremely high reactive oxygen species (ROS) levels, which can lead to mitochondria, cell membrane, and DNA damage as well abnormal gene expression.[33]
Summary
Significant progress has been made in assisted reproduction techniques (ART) for the treatment of infertility ever since Louise Brown, the first test-tube baby, was successfully conceived by in vitro fertilization (IVF) in 1978.1 During the past 40 years, the number of infants conceived through IVF accounts for approximately 0.1% of the total global birth population.[2]. We examined the presence of melatonin in oviduct fluid and EVs, after which we attempted to clarify the mechanisms underlying the potential beneficial effects of melatonin and EVs on in vitro embryo development with regard to reactive oxygen species (ROS) levels, epigenetic state, associated gene expression, and developmental competence of embryos. Embryos, and serum were collected at 20 hours postmating (5:00 am on day 4). Oviduct fluid was collected using a plastic pipette (2 mm diameter) connected to a 1-mL syringe, followed by transfer into a 1-mL centrifuge tube and incubation for 5 minutes. Serum was collected by centrifuging the blood samples, after which the supernatant was stored in the dark for subsequent experiments. 2.4 | Ultracentrifugation, transmission electron microscopy (TEM), and nanoparticle tracking analysis for EVs
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