BACKGROUND: This study examined the ability of cryopreserved whole ovine ovaries to resume function in vivo following autotransplantation.
METHODS: Swaledale ewes had their left ovaries removed and either perfused but not cryopreserved (n = 4; control), or perfused and cryopreserved (n = 8; cryopreserved) before autotransplantation sub-cutaneously to the neck by microvascular anastomosis. Right ovaries were removed and fixed as non-grafted controls. Weekly jugular venous blood samples were analysed for plasma FSH, LH, inhibin A and progesterone levels, grafts were scanned transdermally and oestrus was detected. Vascular patency was assessed post-mortem and follicle populations were measured in recovered tissue.
RESULTS: Immediate vascular patency was achieved in all ewes and maintained in 7/8 cryopreserved and 3/4 control grafts. Functional corpora lutea were identified in three ewes (one control; two cryopreserved) 18-25 weeks after grafting. Inhibin A levels indicated resumption of follicular development in four cryopreserved and one control ewes, however, castrate gonadotrophin levels persisted in five cryopreserved and two control ewes. Primordial follicle density was reduced following grafting in both cryopreserved and non-frozen ovaries (P < 0.001).
CONCLUSIONS: In conclusion, these results demonstrate successful partial restoration of ovarian function following cryopreservation of the whole ovary and vascular pedicle in a large monovulatory species. The inability to restore full ovarian function was related to loss of primordial follicles rather than vascular patency in both frozen and fresh tissue, suggesting that factors associated with cannulation and perfusion may contribute to this depletion. Further work is therefore needed to elucidate these factors before the procedure could be considered a viable option for fertility preservation.