Human oocyte developmental potential is predicted by mechanical properties within hours after fertilization

Area of Science:

• Reproductive biology
• Developmental biology
• Biophysics

Background:

• Embryonic arrest during pre-implantation development lacks clear causes.
• Predicting early embryo viability is challenging due to the absence of reliable, non-destructive methods.
• Oocyte gene expression has been difficult to correlate with successful embryo development.

Purpose of the Study:

• To identify reliable and non-destructive predictors of early embryo viability.
• To investigate the relationship between zygote mechanical properties and blastocyst formation.
• To understand the role of oocyte quality and maturation in determining embryo potential.

Main Methods:

• Measurement of zygote viscoelastic properties shortly after fertilization in humans and mice.
• Analysis of zygote transcriptomes to identify differences between viable and non-viable embryos.
• Assessment of cortical granule release and zona hardening in oocytes.

Main Results:

• Zygote viscoelastic properties accurately predict blastocyst formation (>90% precision, 95% specificity, 75% sensitivity).
• Significant transcriptome differences exist between viable and non-viable zygotes, particularly in oocyte maturation genes.
• Low-quality oocytes exhibit altered mechanics due to insufficient cortical granule release and zona hardening.

Conclusions:

• Embryo potential is primarily determined by oocyte quality and maturation prior to fertilization.
• Zygote mechanical properties offer a predictive measure of embryo viability.
• Minimally invasive mechanical assessment at the zygote stage can predict blastocyst formation.