Embryo apoptosis identification: Oocyte grade or cleavage stage?

Area of Science:

• Reproductive biology
• Cellular biology
• Developmental biology

Background:

• Programmed cell death (apoptosis) is crucial for tissue homeostasis.
• Embryo apoptosis is linked to fragmentation, a concern in in vitro fertilization (IVF).

Purpose of the Study:

• To investigate the relationship between embryo apoptosis and immature oocyte grade.
• To evaluate embryo apoptosis in relation to the cleavage stage of in vitro produced (IVP) cattle embryos.

Main Methods:

• Collected 345 oocytes, graded immature oocytes (A, B, C) based on cumulus cell characteristics.
• Performed in vitro maturation (IVM), in vitro fertilization (IVF), and classified embryo cleavage stages (2, 4, 8, >8-cell).
• Assessed apoptosis using annexin V-FITC staining at 48 and 72 hours post-insemination (hpi).

Main Results:

• No significant difference in apoptosis status was found among oocyte grades A, B, and C (p > 0.05).
• Apoptosis was observed across all oocyte grades, with varying percentages of early and late apoptosis.
• No significant difference in apoptosis status was observed across different embryo cleavage stages (p > 0.05).
• Grade A oocytes showed a significantly higher cleavage rate (p < 0.01) compared to grades B and C.

Conclusions:

• Embryo apoptosis can occur irrespective of oocyte quality.
• Apoptosis expression in embryos is not significantly influenced by the cleavage stage.
• Oocyte quality, while not affecting apoptosis, impacts cleavage rates in IVP cattle embryos.