Ovarian tissue cryopreservation: a practical option?

Novel gamete storage

The aim of this review is to outline recent advances in gamete storage that are beneficial for rescuing endangered species or for the breeding of companion animals. Much more information is available on the technical resolutions and practical applications of sperm cryopreservation in various species than of female gametes, reproductive tissues or organs. Mammalian sperm cryopreservation often works relatively efficiently; however, the ability of female gametes to be cryopreserved and still be viable for fertilisation is also essential for rescuing endangered species. For a proper evaluation of gamete cryopreservation possibilities in a given species, it is essential to understand the basic mechanism affecting the survival of cryopreserved cells, the technical and physical limitations, the available techniques and the new avenues to resolve the specific problems in that species. This paper is aimed to provide some help for this process. The limited length of this paper resulted in the omission of information on many important areas, including most data on teleosts, amphibian and insect cryopreservation.

Isolated ovine primordial follicles cryopreserved in different concentrations of ethylene glycol

Cryopreservation of primordial follicles represents an opportunity to preserve female gametes, and consequently to protect the reproductive capacity of humans and animals, as well as to safeguard genetic material from endangered animal species or rare breeds. The aim of this work was to assess the toxicity of different concentrations of ethylene glycol (EG) to primordial follicles, and verify the viability of these follicles after the freezing-thawing procedure. Primordial follicles were isolated from ovine ovaries and exposed to different EG concentrations to evaluate the cryoprotectant (CPA) toxicity before and after cryopreservation. After isolation of primordial follicle (control), the number (mean+/-S.E.M.) of viable primordial follicles/ml was 3764+/-795.21. The number of viable follicles in the toxicity test using EG at 0, 0.5, 1.0, 1.5, 2.0, and 2.5 M was 1096+/-447.9, 960+/-446.67, 948+/-366.14, 832+/-313.59, 856+/-280.67, and 700+/-255.02, respectively. The number of viable follicles at concentrations of 2.5 M was less than for controls. After cryopreservation, the numbers decreased to 0+/-0, 148+/-85.46, 764+/-246.69, 824+/-291.9, 844+/-296.27, and 588+/-200.65, respectively for 0, 0.5, 1.0, 1.5, 2.0, and 2.5 M EG. The number of viable follicles at 0, 0.5, and 2.5 M was less than for controls. In conclusion, after the freezing and thawing procedure, concentrations of 1.0, 1.5, and 2.0 M EG can be successfully used for the cryopreservation of isolated follicles in sheep.

Inhibin and follicular development in heterotopical ovary transplants without vascular pedicle in syngeneic Lewis rats

OBJECTIVE

To evaluate the role of inhibin in elevated base levels of FSH and follicular hyperplasia in ovarian autotransplantation in rats.

DESIGN

Experimental animal study.

SETTING

Unit of Experimental Research at the Barcelona University School of Medicine.

ANIMAL(S)

Female syngeneic Lewis rats aged 16 weeks.

INTERVENTION(S)

The animals were randomized into two groups: group A, control group undergoing only laparotomy (n = 5) and group B, oophorectomized with SC autologous heterotopic transplant (n = 5). The animals were killed and their ovaries removed for histologic, morphometric, and immunohistochemical analysis at 28 days after surgery in both groups.

MAIN OUTCOME MEASURE(S)

Serum levels of E2 and FSH were determined on day 0 (the day of surgery or baseline) and days 4, 7, 14, 21, and 28. Morphometric analysis of ovarian structure for evaluation of antral follicles and their granulosa cell area and immunohistochemistry for inhibin staining were also done.

RESULT(S)

The endocrinological function recovered at 28 days, and the FSH levels for the transplant group were significantly higher than for the group with normoinsert ovary. Morphometric analysis showed that the mean granulosa cell area was greater in group B when compared with the control group. Immunohistochemistry revealed almost null inhibin staining of the stroma in transplanted ovarian tissue.

CONCLUSION(S)

Tissue damage brought on by ischemia in the transplant of nonvascularized ovaries may bring about an inhibin deficit in the ovarian stroma, which might explain the increased levels of FSH. These increased levels, in turn, would be responsible for the follicular hyperplasia seen in this tissue when it recovers its function.

Female reproductive potential post-treatment for childhood cancer

Survival post-treatment for childhood malignancy is now in excess of 70%. Hence female reproductive potential following treatment must be addressed. Issues concerning subsequent uterine and ovarian function, fertility options and importantly the ethics and safety of treatment approaches are discussed herein.