ABSTRACT
Oocyte, embryo and ovarian tissue cryopreservation are being increasingly proposed for fertility preservation among cancer patients undergoing therapy to enable them to have babies after the cancer is cured. Embryo cryopreservation is not appropriate for single girls without any spermpartner. It is impossible in cases requiring immediate cancer cure because oocyte retrieval is an extended procedure. Thus ovarian tissue cryopreservation has been suggested for fertility preservation especially in cancer patients. The main goal of ovarian cryopreservation is re-implanting the tissue into the body to restore fertility and the hormonal cycle. Different cryopreservation protocols have been examined and established for vitrification of biological samples. We have used Cryopin to plunge ovarian tissue into the liquid nitrogen and promising results have been observed. The possibility of recurrence of malignancy in the reimplanted tissue could be a problem. Xenografting-implantation of the preserved tissue in another species-also has its drawbacks such as molecular signaling from the recipient. In vitro follicle culturing is a safer method to obtain mature oocytes for fertilization and the various studies that have been carried out in this area are reviewed in this paper
ABSTRACT
Objective: Different cryoprotectants are used for cryopreservation of ovarian tissue in patients at risk of infertility. Ethylene glycol [EG], dimethyl sulfoxide [DMSO] and propanediol [PROH] have been chosen as the basic permeable cryoprotectants due to their decreased glass-formation characteristics compared to other cryoprotectants. In the present study, the effects of two different vitrification methods on whole mouse ovarian tissue by the use of a novel staining method [trypan blue] has been evaluated
Methods: Ovaries of 8 day-old NMRI mice were isolated and divided among the control, vitrification 1 [Vit1] and vitrification 2 [Vit2] groups. The Vit1 solution was composed of alpha-MEM+ 20% FBS + 15% EG + 15% DMSO. The Vit 2 solution was composed of alpha- MEM+ 15% FBS +20% EG + 20% PROH. Vit1 and Vit2 procedures were performed at 4°C and room temperature, respectively. Warming was performed in alpha-MEM+ 20% FBS supplemented with 1M sucrose in the Vit1 group and alpha-MEM+ 15% FBS with descending concentrations of sucrose [1, 0.5, 0.25 M] in the Vit2 group. Control and vitrified warmed ovaries were put in alpha-MEM supplemented by 0.4% trypan blue for 20 min, and then stained ovaries were fixed in Bouin's fixative, serially sectioned in paraffin wax and finally quantitatively evaluated under a light microscope
Results: The highest percentage of primordial follicles was observed in the control group. There was a significant difference between the control and Vit1 groups, and between the Vit1 and Vit2 groups [p<0.05]. No significant difference was observed in primary and preantral follicles between the control and vitrification groups
Conclusion: Vitrification with EG and PROH are more suitable for preservation of follicle reserves in ovaries. Trypan blue staining is a faster and easier method for evaluation of ovarian tissue