Long-term ovarian function in sheep after ovariectomy and transplantation of autografts stored at -196 C

Follicular development, ovulation, and corpus luteum formation in cryopreserved human ovarian tissue after xenotransplantation

OBJECTIVE

To assess the competency of human frozen/thawed ovarian follicles matured in xenografts to form functioning corpora luteae after human chorionic gonadotropin (hCG) administration.

DESIGN

Prospective controlled animal study.

SETTING

University research laboratory.

PATIENT(S)

Three women (19, 28, and 36 years) who underwent oophorectomy.

ANIMAL(S)

Nineteen female severe combined immunodeficient (SCID) mice.

INTERVENTION(S)

Cryopreserved human ovarian tissues were grafted into the s.c. space of bilaterally oophorectomized SCID mice. All the animals were stimulated with pregnant mare's serum gonadotropin (PMSG) for 4 weeks starting from 16 weeks after transplantation. Twelve animals were injected with hCG at the end of gonadotropin stimulation.

MAIN OUTCOME MEASURE(S)

[1] The rate of grafts with growing follicles, with antral follicles, and/or with corpora luteae. [2] The histologic assessment of follicles and corpora luteae. [3] The serum progesterone and estradiol level in animals with corpus luteum in the grafts.

RESULT(S)

[1] The rate of grafts with growing follicles and with corpora luteae was 33% to 100%, and 28% to 50%, respectively. [2] Corpora luteae in xenografts were all morphologically normal. [3] The progesterone levels were all above 3.0 ng/mL.

CONCLUSION(S)

This study showed that the cryopreserved human ovarian follicles can be matured to a stage at which they can form functioning corpora luteae in the host animal.

Heterotopic autotransplantation of the ovary with microvascular anastomosis: a novel surgical technique

OBJECTIVE

To test the feasibility of transplanting an entire ovary with anastomosis of the ovarian vascular pedicle.

DESIGN

Long-term survival study.

SETTING

Biological Resources Unit, Cleveland Clinic Foundation.

ANIMAL(S)

Five adult, nonpregnant ewes.

INTERVENTION(S)

Laparoscopic bilateral oophorectomy was performed. Ovaries were autotransplanted into the abdominal wall, and microsurgical vascular anastomosis of the ovarian to the inferior epigastric vessels was performed. The transplant was removed and evaluated after 7 +/- 1 days.

MAIN OUTCOME MEASURE(S)

Blood flow, serum E2 and FSH levels, and histologic characteristics.

RESULT(S)

At follow-up three transplants were viable; they showed no signs of necrosis, and patency of the vascular anastomosis was confirmed. Serum E2 levels did not change significantly after transplantation in the patent vessel group (155.3 +/- 46.1 vs. 125.7 +/- 44.6 pg/mL) or the nonpatent vessel group (99 vs. 158 pg/mL). Serum FSH level in the patent vessel group did not change significantly from before to after transplantation (70.6 +/- 37.2 ng/mL vs. 95.1 +/- 17.7 ng/mL), whereas a large increase in FSH level was observed in the nonpatent vessel group (52.3 ng/mL vs. 522 ng/mL). The patent vessel group had significantly more follicles after transplantation than did the nonpatent vessel group (6 +/- 1 vs. 1 +/- 1).

CONCLUSION(S)

In conjunction with improved protocols for cryopreservation, ovarian autotransplantation with vascular anastomosis may be superior to current ovarian tissue banking and grafting techniques.

Restoration of fertility in oophorectomized rats after tubo-ovarian transplantation

Improved microsurgical techniques for en bloc vascularized adnexal isograft in the rat is described. The graft of the right ovary together with its fallopian tube and upper third of uterus was transplanted orthotopically with end-to-side anastomoses between the donor aortic segment and recipient aorta and between the donor vena cava segment and recipient inferior vena cava, with end-to-end anastomosis of the donor and recipient uterus in a syngeneic, bilaterally oophorectomized rat. All transplantations were successful in terms of immediate vascular patency rate (10/10, 100%). Evidence of resumed ovarian function was obtained in 9 out of 10 rats (9/10, 90.0%) by histological demonstration of the vaginal smear, in which pregnancies were achieved in six rats (6/10, 60.0%) and six litters of healthy offspring were delivered 9 weeks later after transplantation. These results suggest that microsurgical ovarian transplantation provide a new and potential experimental model for the study of fertility restoration in humans.

The potential of ovarian tissue transplant to preserve fertility

Laboratory research on ovarian cryopreservation and transplantation began in the 1950s leading to clinical studies in the 2000s. The research that was performed during this half a century indicated that cryopreserved ovarian tissue has the potential to restore fertility in women who face premature ovarian failure due to chemotherapy, radiotherapy or surgery. Until today, ovarian function has been restored in at least four women. Even though no pregnancies have been reported to date from these clinical studies, animal studies indicate that this is a valid prospect for humans. Future clinical trials will determine in a larger number of patients the longevity of ovarian grafts, normalcy of hormone production and ovarian follicle development, possibility and safety of pregnancy and the safety of auto-transplantation in cancer patients. In addition, further basic research may be needed to develop better cryoprotectants and cryopreservation techniques. However, the major improvement in the efficiency of ovarian transplantation is anticipated to come from research exploring the revascularisation process.

Morphological alterations and DNA fragmentation in oocytes from primordial and primary follicles after freezing-thawing of ovarian cortex in sheep

OBJECTIVE

To evaluate DNA fragmentation in the oocyte of primordial and primary follicles and morphology of these follicles after freezing and thawing of ovarian cortex in sheep using two freezing protocols.

DESIGN

Fragmentation of DNA was evaluated by the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) technique.

SETTING

Fertility clinic in a large university hospital.

ANIMALS

Five- to 6-month-old lambs.

INTERVENTION(S)

Two-millimeter-thick slices of hemi-ovary cortex were prepared.

MAIN OUTCOME MEASURE(S)

Histological structure and DNA fragmentation.

RESULT(S)

In the frozen fragments, the percentage of morphologically normal follicles was significantly lower for both protocols compared with the case of the control group of fresh fragments. There was no significant difference between the two types of freezing protocols (60.4% +/- 13.2% vs. 68.4% +/- 13.7%). However, the distribution of abnormalities (nucleus, cytoplasm, and nucleus and cytoplasm) was dissimilar. The results of the TUNEL technique for the three groups showed no significant difference, but the percentage of the TUNEL-positive follicles was slightly lower for the frozen fragments for both protocols with respect to the control group.

CONCLUSION(S)

The freezing and thawing process of the ovarian cortex does not induce fragmentation of the DNA on the oocyte of primary and primordial follicles.

Heterotopic ovarian transplantation without vascular pedicle in syngeneic Lewis rats: long-term evaluation of effects on ovarian structure and function

OBJECTIVE

To assess the long-term efficacy of intraperitoneal (IP) and subcutaneous (SC) ovarian autotransplantation in rats.

DESIGN

Experimental animal study.

SETTING

Unit of Experimental Research, Barcelona University School of Medicine.

ANIMAL(S)

Female syngeneic Lewis rats aged 14 weeks.

INTERVENTION(S)

Group A, control group undergoing ovariectomy (n = 15); group B, undergoing ovariectomy and IP autologous heterotopic transplant (n = 15); and group C, ovariectomized with SC autologous heterotopic transplant (n = 15). In groups B and C, five animals were killed and their ovaries removed for morphometric analysis at 30 days after transplantation; five additional animals were killed at 180 days, and the remaining five animals were killed at 360 days.

MAIN OUTCOME MEASURE(S)

Ovarian morphometric analysis and serial measurement of E(2) and FSH serum levels. RESULT(S); The mean number of antral follicles in the control group A was significantly higher than that observed in the ovarian grafts collected and examined 30 days after grafting in rats from groups B and C, but the mean granulosa cell area was significantly higher in both transplantation groups than in controls because of ovarian follicular hyperplasia. Histological examination of ovaries removed at 6 and 12 months after grafting in groups B and C showed increasing degrees of fibrosis, loss of primordial follicles, and the presence of epithelial cysts. In groups B and C, from day 30 after surgery onward, serum E(2) was significantly higher and FSH significantly lower, respectively, than in group A. E(2) and FSH patterns in groups B and C were similar throughout the study period.

CONCLUSION(S)

Heterotopic ovarian transplantation without vascular pedicle in rats is characterized by follicular hyperplasia endocrinologically functional, followed by progressive loss of follicles in heterotopic ovarian autografts.

Normal pregnancies and live births after autograft of frozen-thawed hemi-ovaries into ewes

OBJECTIVE

To evaluate long-term outcome of autotransplantation of cryopreserved hemi-ovaries into ewes.

DESIGN

Animal study.

SETTING

University fertility center, Hospices Civils de Lyon; and Ecole Nationale Vétérinaire de Lyon.

PATIENT(S)

Grivette ewes.

INTERVENTION(S)

Six hemi-ovaries from 6 ewes aged 6 to 12 months were frozen with a slow cooling protocol using 2 M of dimethyl sulfoxide as cryoprotectant. After dissection of the medulla, the hemi-ovarian cortex was stored at -196 degrees C in liquid nitrogen. Freezing procedure was performed with a programmable freezer. Semiautomatic seeding was performed before crystallization. Four to 6 weeks after the first laparotomy, the left ovary was removed and the frozen-thawed hemi-ovary was sutured.

MAIN OUTCOME MEASURE(S)

Mean plasma concentrations of FSH, LH, and progesterone after autotransplantation of frozen-thawed hemi-ovary. Ultrasonography was done to confirm pregnancy. Blood samples were collected weekly to measure FSH, LH, and progesterone. After the first birth, the autografted ovary was removed for histologic examination.

RESULT(S)

Plasma progesterone concentration increased in a regular manner in all ewes except one 4 weeks after the graft. Concentrations of FSH and LH did not reach the menopausal level. Four pregnancies occurred, from which 6 lambs were born. The first delivery of a normal lamb occurred after 135 days of gestation; the lamb died immediately after birth. The second delivery of two normal lambs occurred after 130 days of gestation. A caesarean section was performed on the third pregnant ewe the 110th days of gestation because the ewe had a vaginal prolapsus. The two normal lambs and the ewe died after surgery. The fourth birth of a normal lamb occurred after 132 days of gestation. Histologic examination of the grafted frozen-thawed ovary showed a regressing corpus luteum and few primordial and antral follicles.

CONCLUSION(S)

These four pregnancies in a ewe model may indicate that women who undergo preservation of their ovaries before chemotherapy or radiotherapy can have successful pregnancy.

Ovarian tissue harvested from lymphoma patients to preserve fertility may be safe for autotransplantation

BACKGROUND

Ovarian failure is a common sequel to chemo/radiotherapy in patients successfully treated for cancer. Harvesting, cryopreserving and subsequently re-implanting ovarian cortical grafts can be used to re-establish reproductive potential in women with cancer. The safety issue, however, is of great concern because residual disease in autografted ovarian tissues might cause recrudescence of disease.

METHODS

A total of 30 non-obese diabetic severe combined immunodeficient (NOD/LtSz-SCID) mice were individually xenografted s.c. with frozen-thawed ovarian tissue from 18 patients with lymphoma [13 Hodgkin's lymphoma (HL) and 5 non-Hodgkin's lymphoma (NHL)]. The animals were autopsied at 16 weeks, or earlier if cachectic. The xenograft, liver, spleen, sternum, para-aortic lymph nodes and thymus were prepared for histology, immunohistochemistry and human DNA microsatellite analysis.

RESULTS

None of the animals grafted with ovarian tissue from lymphoma patients developed disease. However, all 3 animals grafted with lymph node tissue from an NHL patient developed B-cell lymphomas that were confirmed as human in origin by DNA microsatellite analysis.

CONCLUSION

Ovarian tissue harvested before high-dose chemotherapy for HL or NHL may not carry a risk of disease transmission by autotransplantation, although the possibility is difficult to exclude completely.

Turner's syndrome

Before chromosomal analysis became available, the diagnosis of Turner's syndrome was based on the characteristics independently described by Otto Ullrich and Henry Turner, such as short stature, gonadal dysgenesis, typical, visible dysmorphic stigmata, and abnormalities in organs, which present in individuals with a female phenotype. Today, Turner's syndrome or Ullrich-Turner's syndrome may be defined as the combination of characteristic physical features and complete or part absence of one of the X chromosomes, frequently accompanied by cell-line mosaicism. The increasing interest in Turner's syndrome over the past two decades has been motivated both by the quest for a model by which the multi-faceted features of this disorder can be understood, and the endeavour to provide life-long support to the patient. New developments in research allow patients with Turner's syndrome to have multidisciplinary care.

A technique for laparoscopic transplantation of frozen-banked ovarian tissue

OBJECTIVE

To describe a laparoscopic technique for transplanting frozen-banked ovarian tissue.

DESIGN

Case study.

SETTING

Academic medical center.

PATIENT(S)

A patient whose ovarian tissue was previously frozen with the slow-freeze technique.

INTERVENTION(S)

Microsurgical reconstruction of ovarian cortex and its laparoscopic transplantation to the ovarian fossa.

MAIN OUTCOME MEASURE(S)

Blood flow to the grafts by doppler, follicle development and ovulation by ultrasound, E(2) and progesterone production, and resumption of spontaneous menses.

RESULT(S)

The patient ovulated and menstruated 4 months after the transplant in response to ovarian stimulation with menopausal gonadotropins.

CONCLUSION(S)

Laparoscopic transplantation of frozen-banked ovarian tissue beneath the pelvic peritoneum can restore ovarian function.

Orthotopic reimplantation of cryopreserved ovarian cortical strips after high-dose chemotherapy for Hodgkin's lymphoma

BACKGROUND

Infertility is a common late effect of chemotherapy and radiotherapy, and has a substantial effect on the quality of life for young survivors of cancer. For men, semen cryopreservation is a simple way of preserving reproductive potential but for women, storage of mature eggs rarely proves successful, and the alternative-immediate in vitro fertilisation with cryopreservation of embryos-is not always appropriate. Reimplantation of cryopreserved ovarian tissue has been shown to restore natural fertility in animals. We applied this technique in a woman who had received sterilising chemotherapy for lymphoma.

METHODS

A 36-year-old woman underwent a right oophorectomy with cryopreservation of ovarian cortical strips before receiving high-dose CBV chemotherapy for a third recurrence of Hodgkin's lymphoma. 19 months later, when serum sex steroid analysis confimed a postmenopausal state, two ovarian cortical strips were thawed and reimplanted-one onto the left ovary and another at the site of the right ovary.

FINDINGS

7 months after reimplantation of ovarian cortical strips, the patient reported resolution of hot flashes and, for the first time, oestradiol was detected in the serum. This finding was associated with a decrease in the concentrations of follicle-stimulating hormone and luteinising hormone, and ultrasonography revealed a 10 mm thick endometrium, a poorly visualised left ovary, and a 2 cm diameter follicular structure to the right of the midline. The patient had one menstrual period, but by 9 months after the implantation, her sex steroid concentrations had returned to those seen with ovarian failure.

INTERPRETATION

Orthotopic reimplantation of frozen/thawed ovarian cortical strips is a well tolerated technique for restoring ovarian function in women treated with sterilising chemotherapy for cancer.

Follicular viability and morphology of sheep ovaries after exposure to cryoprotectant and cryopreservation with different freezing protocols

OBJECTIVE

To test the toxicity of cryoprotectant in sheep ovarian tissue and to determine optimal conditions for freezing hemiovary cortex.

DESIGN

Small follicles (<60 microm in diameter) were isolated enzymatically for viability testing. Dead and live follicles were identified by using trypan blue staining, and follicle morphology was examined histologically.

SETTING

Centre hospitalo-universitaire de Biologie de la Reproduction, Hôpital Edouard Herriot, Lyon, France.

ANIMAL(S)

Lambs 5 to 6 months of age.

INTERVENTION(S)

Two-millimeter slices of hemiovarian cortex were prepared for cryoprotectant toxicity tests and freezing procedures.

MAIN OUTCOME MEASURE(S)

Follicular mortality and histologic structure.

RESULT(S)

For freezing procedures, the concentration of cryoprotectant was increased to 2 M on the basis of results of cryoprotectant toxicity tests in fresh tissues. Follicular mortality rates were 4.6% with of 2 M dimethyl sulfoxide (DMSO) and 3.8% with 2 M of propylene glycol (PROH). After freezing with semiautomatic seeding, follicular mortality rates were 8.4% (2 M of DMSO) and 12.4% (2 M of PROH). Tissue morphology was well preserved with 1.5 M of DMSO or PROH. With 1.5 M DMSO, results of the slow cooling protocol (2 degrees C/min) without seeding and the standard very slow cooling protocol (0.3 degrees C/min) were similar.

CONCLUSION(S)

Optimal survival of primordial follicles in the sheep was obtained by using a slow cooling protocol with semiautomatic seeding at 2 M of DMSO.

Cryopreservation of human ovarian tissue

As survival rates for young cancer patients continue to improve, protection against iatrogenic infertility caused by chemotherapy and/or radiotherapy assumes a higher priority. As things stand, women patients have few options to preserve their fertility while children have none at all.

Cryopreservation of mouse ovarian tissue following prolonged exposure to an Ischemic environment

In cases in which ovarian tissue is to be cryopreserved for tissue or gene banking it is important to maintain its integrity and viability. This study examined how delays between the death of an animal and the collection/cryopreservation of its ovarian tissue influenced follicle viability. Mouse ovaries were placed in PBS+antibiotic (in vitro) or left within the body (in situ) at room temperature for 0, 3, 6, 12, or 24 h following the death of the donor. These ovaries were cryopreserved at 1 degrees C/min on dry ice or in a -84 degrees C freezer using a passive cooling device or by conventional slow cooling (0.3 degrees C/min). The ovaries were grafted under the kidney capsule of ovariectomized recipient mice and collected 2 weeks later, and the size and number of follicles were determined. Cryopreserved ovarian tissue grafted immediately after the death of the donor contained numerous viable and healthy follicles independent of the cooling procedure (dry ice, 134 +/- 32; -84 degrees C, 165 +/- 54; slow, 214 +/- 55 follicles per half ovary). Tissues stored in vitro before cryopreservation retained viable follicles up to 12 h after death (dry ice, 30 +/- 15; -84 degrees C, 86 +/- 45; slow, 93 +/- 33), whereas tissue left in situ had significantly reduced follicle numbers within 3 h of death (dry ice, 36 +/- 12; -84 degrees C, 19 +/- 6; slow, 28 +/- 7). No significant difference was found between the cooling rates tested, indicating that a passive cooling container which cools at 1 degrees C/min is a suitable alternative to conventional slow cooling. We conclude that ovarian tissues for cryobanking should be cryopreserved as soon as possible after collection or death of the animal to ensure maximal follicular survival.

Follicular development in transplanted fetal and neonatal mouse ovaries is influenced by the gonadal status of the adult recipient

OBJECTIVE(S)

To investigate the pattern of follicular development in transplanted fetal and neonatal mouse ovaries in the presence or absence of the recipient's own ovaries.

DESIGN

Controlled experiment.

SETTING

Academic research laboratory, Department of Physiology, Monash University, Clayton, Australia.

INTERVENTION(S)

Mouse ovaries from 16-day-old fetuses, 3-day-old neonates, and 10-day-old neonates were transplanted under the kidney capsule of adult female mice, which either retained their own ovaries in situ or were bilaterally ovariectomized.

MAIN OUTCOME MEASURE(S)

Histologic analysis.

RESULT(S)

By 4 weeks after transplantation, fetal and neonatal ovaries transplanted to ovariectomized recipients displayed a pattern of follicular development similar to that observed in in situ adult mouse ovaries. In contrast, follicular development did not progress beyond the early antral stage in fetal and 3-day-old ovaries transplanted to recipients that retained their in situ ovaries. However, 10-day-old ovaries transplanted to recipients that retained their in situ ovaries displayed full follicular development and corpora lutea formation by 8 weeks after transplantation.

CONCLUSION(S)

Follicular development in transplanted immature ovarian tissue is influenced by the age of the donor ovary and gonadal status of the recipient. (Fertil Steril(R) 2000;74:000-00. Copyright2000 by American Society for Reproductive Medicine.)

Restoration of a normal reproductive lifespan after grafting of cryopreserved mouse ovaries

Fresh and frozen ovaries from 10 day old C57BL/6J-Gpi-1(a) mice were grafted orthotopically into ovariectomized B6CBF1 (homozygous Gpi-1(b)) recipients. The recipients were mated with B6CBF1 males. The birth and size of each litter was recorded. The electrophoretic variant of glucose phosphate isomerase was determined for each neonate. Twelve of 13 recipients of fresh ovary and 10 of 12 recipients of frozen ovary were fertile. Of these, 10 (fresh) and eight (frozen) had litters derived from the ovarian grafts only, or from the graft and native ovary. The breeding characteristics of recipients of fresh and frozen grafts were similar. The reproductive lifespan of the recipients of fresh (6.2 litters) and frozen (8.4 litters) grafts was similar to that of unoperated C57BL/6-Gpi-1(a) control females mated with B6CBF1 males (6.3 litters). Litter size was similar in recipients of grafted ovaries (fresh, 5.4 pups/litter; frozen, 6.3 pups/litter) and C57BL/6-Gpi-1(a) females (6.3 pups/litter). The results suggest that cryopreservation per se does not affect the long-term viability of ovarian tissue and provides an option for storing female germ cells. This is the first unequivocal demonstration that a normal reproductive lifespan can be restored by orthotopic grafting of frozen ovary.

Hodgkin's Lymphoma

This review focuses on the different treatment options available for the treatment of Hodgkin's disease, with an emphasis on the importance of the long-term sequelae of these therapies.

In Section I, Dr. Linch reviews the current status of Hodgkin's disease treatment. Survival rates have improved over the last three decades due both to better initial therapies and associated supportive care and to the success of salvage therapy. Unlike most other malignancies, a similar survival endpoint can be achieved by different means, e.g., intensive initial therapy resulting in a low relapse rate or less intensive initial therapy and more reliance on salvage therapy. Overall survival has thus become a difficult end-point for clinical trials of primary therapy, and the value of disease-free survival as an end-point can also be questioned. Quality-of-life issues are to the fore of clinical decision and include the psychological trauma of relapse and fertility status. Patient choice is increasingly important. The high level of success in treating Hodgkin's disease also means that attention must be focused on the very long term results and in this context the occurrence of second malignancies is a major issue.

In Section II, Dr. Gosden with Dr. Tulandi and Dr. Tan review the risks of infertility following radio-therapy and chemotherapy and address the actions that can be taken to overcome this problem, particularly for females and prepubertal boys and girls. Particular attention is paid to the recent developments in ovarian cryopreservation and harvesting immature germ cells.

In Section III, Dr. Hancock gives a comprehensive update of the incidence of secondary acute leukemia, non-Hodgkin's lymphoma and solid tumors in a large population of patients treated for Hodgkin's disease. The roles of radiotherapy, chemotherapy and combined modality treatment as risk factors contributing to the development of these secondary malignancies are reviewed. The importance of efforts to prevent late-occurring solid tumors such as lung cancer through smoking cessation programs and early detection by screening for cancers of the breast, thyroid and skin are emphasized.

Hodgkin's Lymphoma

This review focuses on the different treatment options available for the treatment of Hodgkin's disease, with an emphasis on the importance of the long-term sequelae of these therapies.

In Section I, Dr. Linch reviews the current status of Hodgkin's disease treatment. Survival rates have improved over the last three decades due both to better initial therapies and associated supportive care and to the success of salvage therapy. Unlike most other malignancies, a similar survival endpoint can be achieved by different means, e.g., intensive initial therapy resulting in a low relapse rate or less intensive initial therapy and more reliance on salvage therapy. Overall survival has thus become a difficult end-point for clinical trials of primary therapy, and the value of disease-free survival as an end-point can also be questioned. Quality-of-life issues are to the fore of clinical decision and include the psychological trauma of relapse and fertility status. Patient choice is increasingly important. The high level of success in treating Hodgkin's disease also means that attention must be focused on the very long term results and in this context the occurrence of second malignancies is a major issue.

In Section II, Dr. Gosden with Dr. Tulandi and Dr. Tan review the risks of infertility following radio-therapy and chemotherapy and address the actions that can be taken to overcome this problem, particularly for females and prepubertal boys and girls. Particular attention is paid to the recent developments in ovarian cryopreservation and harvesting immature germ cells.

In Section III, Dr. Hancock gives a comprehensive update of the incidence of secondary acute leukemia, non-Hodgkin's lymphoma and solid tumors in a large population of patients treated for Hodgkin's disease. The roles of radiotherapy, chemotherapy and combined modality treatment as risk factors contributing to the development of these secondary malignancies are reviewed. The importance of efforts to prevent late-occurring solid tumors such as lung cancer through smoking cessation programs and early detection by screening for cancers of the breast, thyroid and skin are emphasized.

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

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.