Impact of the cryopreservation technique and vascular bed on ovarian tissue transplantation in cynomolgus monkeys

The aim of this study was to determine the best combination in terms of cryopreservation techniques and vascular bed preparation before grafting in order to obtain functional ovarian tissue after transplantation. Five cynomolgus monkeys were used. Strips from 10 ovaries were cryopreserved, 5 by vitrification (V), and 5 by slow-freezing (SF). Pieces of fresh ovarian tissue were used for controls. After 1 month, the strips were autografted to two different vascular beds, healed (HB) or freshly decorticated (FDB), constituting four study groups: SF-HB, SF-FDB, V-HB, and V-FDB. These were compared to fresh tissue. After 6 months, the ovaries were removed and several parameters analyzed: follicle quality, stage, density, proliferation, apoptosis, functionality, vascularization, and fibrosis. Mixed effect linear regression models were built to assess the impact of cryopreservation and vascular bed preparation on ovarian tissue viability and functionality. p values were adjusted for multiple testing using the Benjamini-Hochberg method, and q values < 0.20 were considered significant in order to achieve a 20 % false discovery rate. Compared to fresh tissue, no difference was observed in the percentage of morphologically normal follicles, while a significant increase was noted in the follicle proliferation rate (41 %, q = 0.19), percentage of antral follicles (12 %, q = 0.14), and number of vessels per area (3.3 times, q = 0.07) in the V-FDB group. Vitrification associated with FDB vascular bed preparation is the best combination to obtain functional autografted ovarian tissue. Further studies are nevertheless required, with confirmed pregnancies and live births before introducing the procedure into clinical practice.