Ovarian tissue cryopreservation and egg freezing are both fertility preservation methods, but they serve different patient groups and involve fundamentally different biological and technical processes.
Egg freezing involves retrieving mature oocytes from a stimulated ovarian cycle, vitrifying them using the standard IVF vitrification process, and storing them in liquid nitrogen. It is available to women who can undergo ovarian stimulation and who have time before their fertility-threatening treatment begins. The vitrified oocytes can be warmed and used in a future IVF cycle. The CBS High Security Vitrification Kits used for embryo vitrification are equally applicable to oocyte vitrification.
Ovarian tissue cryopreservation involves surgically removing a portion of ovarian cortex, the outer layer of the ovary that contains the primordial follicles, and cryopreserving the tissue rather than individual eggs. The tissue is typically slow frozen using a controlled rate freezer rather than vitrified, because the volume and structural complexity of cortical tissue requires a different thermodynamic approach than individual oocytes.
<blockquote><p>Ovarian tissue cryopreservation is the only fertility preservation option available to girls who have not yet reached puberty and to women who cannot delay cancer treatment for the two to three weeks required for ovarian stimulation. For these patients, it is not an alternative to egg freezing – it is the only available option.</p></blockquote>
The reimplantation of ovarian tissue after cancer treatment has resulted in over 200 live births globally, with the first UK birth from this procedure reported in 2016. The CBS DigitCool controlled rate freezer supports the slow freezing protocols used for ovarian cortex tissue. For further guidance, contact Cryolab.
