Survival rate of preantral follicles derived from vitrified neonate mouse ovarian tissue by Cryotop and conventional methods

Two-Decade Experience of Royan Institute in Obtaining Mature Oocyte from Cryopreserved Ovarian Tissue: In Vitro and In Vivo Approaches

Ovarian tissue cryopreservation (OTC) holds promise for preservation of fertility among women who have lost their fertility due to diseases such as cancer. OTC has significantly assisted such cases by helping them maintain normal hormonal levels and menstrual cycles. Appropriate strategies to develop and extract mature oocytes from OTC could overcome a range of complications that are associated with ovarian dysfunction, caused by aging, and primary or secondary ovarian insufficiency. Scientists from different departments at The Royan Institute (Tehran, Iran) have been conducting studies to find the best way to extract mature oocytes from animal and human cryopreserved ovarian tissues. The various studies conducted in this area in the past 20 years, by researchers of the Royan Institute, are collated and provided in this review, in order to provide an idea of where we are now in the area of fertility preservation.

Three dimensional in vitro culture of preantral follicles following slow-freezing and vitrification of mouse ovarian tissue

To evaluate the effects slow-freezing and vitrification on three dimensional in vitro culture of preantral follicles, ovaries of 12-14 days old female NMRI mice were isolated and randomly assigned to fresh control, slow-freezing and vitrification groups. Slow-freezing was performed using programmable freezer. Vitrification was carried out in a medium consisting of ethylene glycol (EG) and dimethyl sulphoxide (Me2SO) by needle immersion method. middle sized preantral follicles were mechanically isolated and cultured for 12 days in 0.7% sodium alginate gel. The follicles development and quantitative expression of oocyte specific genes (Bmp15, Gdf9, Fgf8) and the growth related genes (Igf1, Kit, Kit-l) were assessed after 1, 8 and 12 days of culture. Both cryopreserved groups showed reduction of follicular survival rates compared to the control group on days 8 and 12 of culture (P < 0.05). Antrum formation rates reduced in slow-freezing after 12 days of culture (P < 0.05). Evaluation of gene expression showed reduction of Bmp15, Gdf9, Fgf8, Kit and Kit-l during 12 days of culture (P < 0.05). Kit and Kit-l expression in slow-freezing group significantly reduced on day 8 of culture (p < 0.05). Igf1 expression was lower in slow-freezing group on 1st day of culture than vitrification and control groups (P < 0.05). Finally, intergroup comparison showed same expression pattern of genes after 12 days of culture. Thus, cryopreservation of mouse ovaries by both methods can preserve most developmental parameters and expression of maturation genes. However, vitrification is a better method for cryopreservation of mouse ovaries due to greater antrum formation and expression of growth related markers.

Heterotopic autotransplantation of vitrified mouse ovary

Purpose

The aim of this study was to investigate the survival and development of premature follicles and oocytes from a vitrified-transplanted ovary in a murine experimental model.

Methods

The 14-day-old mice were unilaterally ovariectomized and the separated ovaries were vitrified by cryotop. After 2 weeks the ovaries were warmed and autotransplanted into the gluteus superfiscialis muscle. After 3 weeks, these ovaries (vit-trans), the ovaries from the opposite side (OPP), and 7-week fresh mouse ovaries as sham and control group (7 week-fresh), were recovered and examined histologically and by TUNEL test.

Results

All 4 vitrified-autotransplanted ovaries had developing follicles. Primordial, primary, preantral and antral follicles were found in all three groups (7 week-fresh, OPP and vit-trans). The rate of apoptosis by TUNEL test was similar in all groups and no significant difference was found between vitrified-transplanted ovarian tissue and controls.

Conclusions

These data demonstrate successful autotransplantation of vitrified whole mouse ovaries, manifested by the presence of all stages of folliculogenesis. According to the results of this experiment, heterotopic autotransplantation of whole cryopreserved ovary provides the opportunity for follicle development at all stages. However, further experiments are required to improve the efficiency of autotransplantation of cryopreserved ovaries to obtain better results.