CONSERVATION OF THE FOLLICULAR POPULATION IN IRRADIATED RATS BY THE CRYOPRESERVATION AND ORTHOTOPIC AUTOGRAFTING OF OVARIAN TISSUE

Aim: To preserve the follicular population in rats prior to abdominal irradiation by the orthotopic autografting of ovarian cortical slices (frozen/thawed) in one of two cryoprotective agents (CPAs). The propor tion of follicular survival will be quantified at autopsy and a compar ison will be made of the two CPAs. Method: Thirty Wistar rats, aged 38 -39 days; were unilaterally ovariectomised. The ovaries of twenty anim als were slow-cooled in either 1.5 M dimethylsulphoxide (DMSO, group B ) or 1.5 M ethylene glycol (EG; group C). The ovaries of the remaining ten animals (group A) were fixed and histologically examined to deter mine a fresh follicle count. The contralateral ovary was irradiated wi th a single dose of 2.5 Gy. Frozen tissue (from groups B and C) was th awed rapidly and autografted into the irradiated ovarian bursa. All an imals were mated eighteen days after grafting and were sacrificed eigh teen days later. At autopsy, the number of embryos was counted and the ovarian weights recorded, before the tissue was prepared histological ly for quantification of follicular survival. Results: There was no si gnificant difference in the pregnancy rate in the three groups and, al though there was a higher number of embryos in the irradiated control group A compared with groups B and C, the difference was not significa nt. The follicle count in groups B and C was significantly higher than in group a. In group A, the percentage of growing follicles was highe r than in groups B and C and the fresh ovary. Conclusions: Autograftin g frozen/thawed ovarian tissue preserved a proportion of the follicula r population in irradiated rats. There was no significant difference i n the numbers of follicles surviving cryopreservation in the two CPAs. Since the irradiated rats were not totally sterilised, we cannot conc lude that cryopreserved grafts can restore fertility. (C) 1998 Elsevie r Science Ireland Ltd.