Cryopreservation

Oocyte

Zona pellucida

Cell biology

In vitro fertilisation

Biology

Human fertilization

Biomedical engineering

Animal science

Blastocyst

Hatching

Embryo

Anatomy

Embryogenesis

Andrology

Medicine

Proceedings of the National Academy of Sciences

Significance Blastocyst hatching is crucial for implantation of mammalian embryos and a common failure point during in vitro fertilization (IVF). We have little knowledge of the mechanical basis whereby an embryo hatches out of the zona pellucida. We have developed a technique to measure blastocyst pressure, allowing us to quantify physiological parameters and providing additional measures of efficiency in IVF optimization. We find that mechanical stretching of the zona by the blastocyst is essential for efficient hatching. Cryopreservation and thawing of embryos is common during IVF. Our technique reveals significant differences in microphysiology between fresh and thawed embryos. Our experimental and associated mathematical techniques are also applicable to other biological systems involving cavity formation, providing an approach for measuring forces in diverse contexts.

Mechanics of mouse blastocyst hatching revealed by a hydrogel-based microdeformation assay