Effect of cryopreservation and transplantation on the expression of kit ligand and anti-Mllerian hormone in human ovarian tissue

Although cryopreservation and transplantation of ovarian tissue represent a promising alternative to safeguard fertility in cancer patients, low recovery rates of oocytes aspirated from antral follicles and a significant number of empty follicles have been observed in women with transplanted frozenthawed ovarian tissue. In order to understand how freezing and/or grafting may affect follicular development, the follicular expression of kit ligand (KL) and anti-Mllerian hormone (AMH), two key factors activating and inhibiting follicle growth, were assessed after long-term grafting in severe combined immunodeficient (SCID) mice. Ovarian biopsies from eight patients were used for fresh and frozenthawed tissue xenografting in 13 SCID mice for a period of 28 weeks, including 2 weeks of gonadotrophin stimulation. KL, AMH and proliferating cell nuclear antigen (PCNA) immunostaining were quantified before and after grafting in the two treatment groups (fresh and frozenthawed grafted ovarian tissue). Lower expression of KL was found in primordial and primary follicles after grafting of both fresh and frozenthawed tissue. Consistent expression of AMH was found in most growing follicles at a similar rate in both graft types. In fresh and frozenthawed grafts, 1314 of primordial follicles were PCNA-positive, indicating a similar maintenance of quiescent follicles despite follicle activation. Grafting and/or gonadotrophin stimulation appear to affect the follicular expression of KL, which may alter oocyte quality. AMH expression in growing follicles after ovarian tissue transplantation may be one of the factors contributing to the preservation of resting follicles in 28-week-old grafts.