Impact of freezing and thawing of human ovarian tissue on follicular growth after long-term xenotransplantation

VEGF and bFGF increase survival of xenografted human ovarian tissue in an experimental rabbit model

PURPOSE

The aim of this study is to determine whether vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) could increase the survival of xenografted human ovarian tissue in an experimental rabbit model.

METHODS

Fresh human ovarian tissue was xenotransplanted into the back muscle of 25 castrated female New Zealand rabbits for 6 weeks with the immunosuppression of FTY720 (2 mg/kg/d). Rabbits were randomly divided into five experimental groups: (A) graft and host treatment with VEGF (50 ng/ml); (B) graft and host treatment with bFGF (100 ng/ml); (C) graft and host treatment with VEGF(50 ng/ml) + bFGF (100 ng/ml); (D) graft and host treatment with normal saline; (E) control group, no treatment. 4 weeks after transplantation, human menopausal gonadotropin (HMG) 10 IU was administered every second day in group A, group B, group C and group D for 2 weeks. Graft survival was assessed by graft recovery rate, histological analysis, immunohistochemical staining for CD31 and Ki-67expression, TUNEL assay.

RESULTS

After 6 weeks of grafting, the number of CD31-positive stained cells increased significantly in group A, group B and group C compared to the control group. All groups showed strong Ki-67 immunostaining in ovarian stroma. Only one rabbit in group C retained the grafts' follicles. Grafting resulted in relative lower fibrosis in group A and group C compared to the control group. Apoptosis was significantly lower in group C compared to the control group.

CONCLUSIONS

Fresh human ovarian cortex grafted into the back muscle of rabbit can sustain part of ovarian tissue function with the immunosuppression of FTY720, although follicle number diminishes significantly after grafting. The administration of VEGF and bFGF, especially the combination of them, may trigger angiogenesis, reduce apoptosis and fibrosis, increase survival in transplanted human ovarian tissue.

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

BACKGROUND

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 frozen-thawed ovarian tissue. In order to understand how freezing and/or grafting may affect follicular development, the follicular expression of kit ligand (KL) and anti-Müllerian hormone (AMH), two key factors activating and inhibiting follicle growth, were assessed after long-term grafting in severe combined immunodeficient (SCID) mice.

METHODS

Ovarian biopsies from eight patients were used for fresh and frozen-thawed 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 frozen-thawed grafted ovarian tissue).

RESULTS

Lower expression of KL was found in primordial and primary follicles after grafting of both fresh and frozen-thawed tissue. Consistent expression of AMH was found in most growing follicles at a similar rate in both graft types. In fresh and frozen-thawed grafts, 13-14% of primordial follicles were PCNA-positive, indicating a similar maintenance of quiescent follicles despite follicle activation.

CONCLUSIONS

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.