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The review covers current options for ovarian tissue cryopreservation and transplantation and provides a systematic review of the existing literature from the last 10 years, taking into account all previously published reviews on the subject. The different cryopreservation options available for fertility preservation in cancer patients are embryo cryopreservation, oocyte cryopreservation and ovarian tissue cryopreservation. The choice depends on various parameters: the type and timing of chemotherapy, the type of cancer, the patient's age and the partner status. The different options and their results are discussed, as well as their putative indications and efficacy. The review concludes that advances in reproductive technology have made fertility preservation techniques a real possibility for patients whose gonadal function is threatened by premature menopause, or by treatments such as radiotherapy, chemotherapy or surgical castration.

Ovarian tissue cryopreservation is currently proposed to young cancer patients to preserve their fertility before radiochemotherapy. The potential risk is that the tissue might harbor malignant cells that could induce disease recurrence. We therefore decided to evaluate the presence of leukemic cells in cryopreserved ovarian tissue from 18 leukemic patients: 6 with chronic myeloid leukemia (CML) and 12 with acute lymphoblastic leukemia (ALL). In each case, histology, quantitative reverse-transcribed polymerase chain reaction (RT-PCR) and long-term (6 months) xenografting to immunodeficient mice were used. Histology did not identify any malignant cells in the ovarian tissue. By quantitative RT-PCR, 2 of 6 CML patients were positive for BCR-ABL in their ovarian tissue. Among the 12 ALL patients, 7 of the 10 with available molecular markers showed positive leukemic markers in their ovarian tissue (translocations or rearrangement genes). Four mice grafted with ovarian tissue from ALL patients developed intraperitoneal leukemic masses. In conclusion, this study demonstrates, by quantitative RT-PCR, ovarian contamination by malignant cells in acute as well as chronic leukemia, whereas histology fails to do so. Moreover, chemotherapy before ovarian cryopreservation does not exclude malignant contamination. Finally, reimplantation of cryopreserved ovarian tissue from ALL and CML patients puts them at risk of disease recurrence.

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Epidermal growth factor (EGF) has been shown to have a positive effect during in vitro maturation (IVM) and has been reported in follicular fluid at levels capable of stimulating meiosis in a variety of species. The aim of the present work was to study the effect on subsequent development of EGF present in defined medium during bovine 1) oocyte maturation or 2) embryo culture. The presence of EGF during IVM, irrespective of concentration (1, 10, 100 ng/mg), stimulated cumulus expansion and significantly increased the proportion of oocytes attaining metaphase II, the rate of cleavage, and the proportion of embryos reaching the 5- to 8-cell stage at 72 h postinsemination. Blastocyst rates on Days 7 and 9 were also significantly improved for oocytes matured in the presence of EGF (10% vs. 18-24% on Day 7 and 21% vs. 31-32% on Day 9, for Tissue Culture Medium 199 [M199] and M199 + EGF, respectively). The presence of fetal calf serum (FCS) during IVM resulted in similarly elevated rates of development. There was no cumulative effect when EGF and FCS were present together during IVM. The presence of EGF also altered the pattern of proteins neosynthesized during maturation. The maturation-promoting effect of EGF was evident for denuded oocytes also, suggesting that EGF may act, at least in part, directly on the oocyte. Immunofluorescence studies revealed the EGF receptor on immature cumulus-oocyte complexes. When present during postfertilization culture in defined medium (synthetic oviduct fluid), EGF stimulated development in comparison to that of the control but could not replace serum. The results suggest a physiological role for EGF in the regulation of bovine oocyte maturation and development.

The present study demonstrates that spermatogonia are able to survive and proliferate after cryopreservation and long-term transplantation. Complete regeneration of normal spermatogenesis was not observed since, beyond the pachytene stage, no adequate characterization of germ cells was obtained. Further studies are thus required to investigate the differentiation potential of cryopreserved germ cells.

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