Cryopreservation of Human Ovarian Tissue: A Review

Abstract

Background: Cryopreservation of human ovarian tissue has been increasingly applied worldwide to safeguard fertility in cancer patients, notably in young girls and women who cannot delay the onset of their treatment. Moreover, it has been proposed to patients with benign pathologies with a risk of premature ovarian insufficiency. So far, more than 130 live births have been reported after transplantation of cryopreserved ovarian tissue, and almost all patients recovered their ovarian function after tissue reimplantation.

Summary: This review aims to summarize the recent results described in the literature regarding human ovarian tissue cryopreservation in terms of methods and main results obtained so far. To cryopreserve human ovarian tissue, most studies describe a slow freezing/rapid thawing protocol, which is usually an adaptation of a protocol developed for sheep ovarian tissue. Since freezing has been shown to have a deleterious effect on ovarian stroma and granulosa cells, various research groups have been vitrifying ovarian tissue. Despite promising results, only 2 babies have been born after transplantation of vitrified/warmed ovarian tissue. Optimization of both cryopreservation strategies as well as thawing/warming protocols is therefore necessary to improve the survival of follicles in cryopreserved ovarian tissue.

Key messages: Human ovarian tissue cryopreservation has been successfully applied worldwide to preserve fertility in patients with malignant or nonmalignant pathologies that have a detrimental effect on fertility. Human ovarian tissue cryopreservation could also be applied as an alternative to postpone pregnancy or menopause in healthy women. Slow freezing and vitrification procedures have been applied to cryopreserve human ovarian tissue, but both alternatives require optimization.

Keywords: Cancer; Fertility preservation; Freezing; Ovarian tissue; Vitrification.

Fig. 1

Cooling curve in slow freezing protocols for human ovarian tissue.

Fig. 2

A, B Computed tomography images of ovarian tissue samples inside cryovials at −140°C. The spatial resolution is 0.1 mm, and the color scale ranges from dark blue for low attenuation (1.2 CT) to intense red for high attenuation (3.0 CT). The pink cube is a volume of interest measuring 3 × 3 × 1 mm located within the tissue. C Tissue sample cryopreserved with 10% DMSO. The ice structure is shown in dark blue, surrounded by small islands of high DMSO concentration. The tissue cannot be distinguished from the solution around it, although the presence of ice is less pronounced in the sample area. D Tissue sample cryopreserved with 20% DMSO. The ice structure is shown in dark blue and the tissue area is green in color corresponding to a higher DMSO concentration than seen in 10% DMSO (C). Xenografted primordial and primary follicles from human ovarian tissue cryopreserved with 10% (C) and 20% DMSO (D). Reproduced with permission from Elsevier^© [53].