Practical points
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Mature oocyte cryopreservation can now
The ability to store biological material at very low temperatures over extended periods of time (cryopreservation) has provided potential solutions in a wide range of biological and clinical situations. Perhaps nowhere is this more evident than in its application in human assisted reproductive technologies (ARTs). In this chapter, the specific role of the cryopreservation of female reproductive potential in current clinical practice is reviewed.
Subzero storage of animal gametes, both male and female, was first reported in the 1950s, but it was not until the 1980s that the first birth from a frozen human oocyte were reported [12]. At this time, animal studies raised major concerns regarding the risk of generating aneuploid embryos, because of the temperature sensitivity of the meiotic spindle involved in anchoring chromosomes, and the potential for the formation of abnormal foetuses. However, there were also concerns that the
For prepubertal girls, young adolescent girls and those requiring urgent treatment, ovarian tissue storage is the only realistic fertility preservation option. It has, however, been suggested, based on the limited number of oocytes obtained from a single stimulation cycle, that cryopreserving ovarian tissue in young women may offer a higher prospect of future fertility than oocyte cryopreservation. Although an invasive procedure is required to remove ovarian tissue, this can be performed in
The relative risk of potential malignancy within the ovarian tissue has been reviewed for various cancers ([70]*) with high risk status identified in the cases of ovarian cancers and leukaemia (see later). However, the routine histological evaluation of ovarian tissue presenting for cryopreservation (irrespective of estimated risk) has detected malignancy in an area attached to the ovary that contained Hodgkin's lymphoma cells in one patient [71] and Ewing's sarcoma in the medullar area of the
Further research is necessary to establish the risk of malignant cells within tissue from patients with leukaemia and whether these can be eliminated selectively from the tissue. Isolation of follicles free of stromal cells may reduce contamination [80], and it has been postulated that, after the depletion of leukemic cells, the follicles could be reconstructed in a matrix to form a mini or artificial ovary and subsequently grafted to the patient. A number of matrix compositions are presently
Female fertility cryopreservation has evolved from the research phase into the present multi-faceted approach, thereby offering options to women presenting with anticipated loss of fertility. Although many questions remain to be investigated, a review of the technical advances in this field that underpin clinical application gives an important insight into the field of female fertility preservation and highlights the challenges ahead. Mature oocyte cryopreservation can nowPractical points
Internal funding by Melbourne IVF, Australia.
The authors have no conflict of interest.
Of these, ovarian tissue cryopreservation and transplantation is an optimal method for pre-pubertal and single female patients, and can be immediately applied before cancer therapy. To date, more than 130 live births from cryopreserved ovarian tissues have been reported [3]. Despite this progress, the most serious concern raised by the use of cryopreserved ovarian tissues in cancer patients is the possibility of re-introduction of malignant cells into the cured cancer patients.
Comparing the diameter of the oocytes between those which fertilized and those which did not fertilize after warming, we verified that only the non-fertilized oocytes had shown an increase in the total diameter and a decrease in the PS size during the cryopreservation process. For fertilization to occur naturally, the oocyte must preserve the integrity of its structural characteristics [13]. Oocytes tend to retain water and form intracellular ice when cryopreserved.