Structural, biochemical and functional aspects of sperm-oocyte interactions in pigs

Area of Science:

• Reproductive Biology
• Developmental Biology
• Biochemistry

Background:

• Polyspermic fertilization remains a significant challenge in swine in vitro fertilization (IVF).
• The zona pellucida (ZP) plays a critical role in regulating fertilization.
• Understanding ZP maturation is essential for improving IVF outcomes.

Purpose of the Study:

• To characterize the structural and biochemical changes of the porcine zona pellucida (ZP) during oocyte maturation.
• To correlate ZP maturation status with fertilization efficiency and sperm-egg interactions.

Main Methods:

• Scanning electron microscopy (SEM) for surface structure analysis.
• Confocal microscopy for glycoprotein distribution.
• 2D gel electrophoresis and mass spectrometry for biochemical analysis (acidity, sulfation, glycosylation).

Main Results:

• SEM revealed surface structure changes between immature, mature oocytes, and embryos.
• Sperm binding was tighter to in vivo-produced embryos' ZP compared to in vitro-produced.
• ZP acidity increased during maturation due to enhanced sulfation, with new glycosylation sites identified.
• Immature oocytes delayed sperm acrosome reaction induction.

Conclusions:

• Porcine ZP undergoes significant structural and biochemical modifications during oocyte maturation.
• These changes influence sperm-egg interaction and fertilization competence.
• Maturation status of the ZP is critical for successful porcine IVF and preventing polyspermy.