Orthotopic and heterotopic autografts of frozen–thawed ovarian cortex in sheep

Abstract

Freezing ovarian cortex is a new option to preserve the fertility of young patients undergoing cancer treatment or in women facing premature menopause. However, the best way to use this banked tissue remains unclear. The function of heterotopic and orthotopic autografts of frozen-thawed ovarian cortex of sheep was compared in the present study. Fresh and frozen-thawed fragments of ovarian cortex were autografted on the uterine horn of six ewes (orthotopic grafts) and under the skin of the belly in nine ewes (heterotopic grafts). In both orthotopic and heterotopic grafts, the resumption of follicular growth and ovulation was monitored. In orthotopically grafted ewes, fertility was recorded. Oocytes from both types of grafts were collected, matured and fertilized in vitro. In both fresh and frozen-thawed grafts follicular growth resumed normally; preantral and antral follicles were first detectable 4 and 10 weeks respectively following grafting but only 5% of the primordial follicles appeared to have survived. This confirms that grafting procedures are more deleterious for follicle survival than cryopreservation. Although ovulation resumed in most ewes, none of the ewes grafted orthotopically became pregnant at a synchronized mating. Seven months following grafting, oocytes could be collected from heterotopic and orthotopic grafts, matured and some of them fertilized, but none developed to the blastocyst stage. Heterotopic grafting may be an alternative to orthotopic grafting to preserve fertility provided follicle survival in the grafts is markedly improved.

Blastocyst Development After Cryopreservation and Subcutaneous Transplantation of Mouse Ovarian Tissue

“…Aubard et al (16) performed subcutaneous transplantation of frozen ovarian tissue in sheep, but no embryos from IVF could be developed to the blastocyst stage. They concluded that the transplanted ovarian tissue yielded only poor oocytes.…”

Human oocyte and ovarian tissue cryopreservation and its application

“…In contrast to transplantation of large organs, in which reanastomosis of blood vessels is achieved surgically, transplantation of small ovarian fragments depends on the growth of new blood vessels for restoring adequate perfusion. It has been shown that more follicles die from ischemia during transplantation than from freeze-thaw injury during cryopreservation [91,122]. However, a recent study suggests that glutathione and uninastatin can improve the survival rate of follicles in cryopreserved human ovarian tissue after transplantation in nod-scid mice, and resting follicles could be recruited into growing follicles without exogenous gonadotrophin [123].…”

Beneficial effect of desialylated erythropoietin administration on the frozen-thawed canine ovarian xenotransplantation

“…The main drawback of ovarian cryopreservation followed by transplantation is that a large proportion of follicles are lost during the initial ischemia which occurs after transplantation [9][10][11][12][13][14][15][16]. Therefore, reducing the damage due to the ischemic interval between transplantation and revascularization is essential to maintaining both follicular reserve and the function of the graft.…”