Epigenetic changes in preimplantation embryos subjected to laser manipulation

Area of Science:

• Reproductive biology
• Epigenetics
• Assisted reproductive technology

Background:

• Laser-assisted hatching (LAH) is used in assisted reproductive technology (ART), but its impact on embryo epigenetics is unclear.
• Previous studies suggest laser manipulation may compromise genetic integrity.
• Thermal stress from LAH could potentially alter epigenetic signatures via de novo methyltransferases (Dnmt).

Purpose of the Study:

• To investigate the effect of LAH on the expression of de novo methyltransferases (Dnmt3a and Dnmt3b) and global DNA methylation in mouse embryos.
• To determine if thermal energy from LAH impacts epigenetic integrity.

Main Methods:

• Mouse embryos at 2-cell, 6-8-cell, and blastocyst stages were subjected to LAH using a 1480-nm diode laser.
• Two pulses of 350 μs were applied to the zona pellucida.
• Post-LAH embryos were assessed for Dnmt3a, Dnmt3b mRNA levels, and LINE-1 methylation at the blastocyst stage.

Main Results:

• LAH at the two-cell stage significantly reduced Dnmt3a and Dnmt3b mRNA transcripts (P < 0.01 and P < 0.05, respectively).
• LAH at later stages (6-8-cell and blastocyst) did not significantly alter Dnmt mRNA levels.
• Global LINE-1 methylation remained unchanged between LAH and control groups across all studied stages.

Conclusions:

• Two-cell stage LAH in mouse embryos can alter the expression of de novo methyltransferases (Dnmt).
• Global DNA methylation, assessed by LINE-1 methylation, is not significantly affected by LAH at any stage.
• Further research is needed to fully understand the long-term epigenetic consequences of LAH.