Freezing of oocytes

Successful Pregnancies, Births, and Child Development Following Oocyte Cryostorage in Female Cancer Patients During 25 Years of Fertility Preservation

Simple Summary

The study goal is to demonstrate that oocyte cryopreservation is a feasible and efficient option for fertility preservation in cancer patients through the comparison of in vitro fertilization treatments in nononcological patients.

Abstract

The preservation of fertility in cancer patients is a crucial aspect of modern reproductive medicine. Amenorrhea and infertility often occur after cancer therapy, worsening the quality of life. Cryopreservation of oocytes in young cancer patients is a therapeutic option for preserving fertility. A prospective study was conducted on 508 cancer patients who underwent oocyte cryopreservation to preserve fertility between 1996 and 2021 including the COVID-19 pandemic period. Patients underwent ovarian stimulation, followed by egg retrieval, and oocytes were cryopreserved by slow freezing or vitrification. Sixty-four thawing/warming cycles were performed. Survival, fertilization, pregnancy, and birth rate over the thawing/warming cycles were obtained. The data were compared with those from a group of 1042 nononcological patients who cryopreserved supernumerary oocytes. An average of 8.8 ± 6.9 oocytes were retrieved per cycle, and 6.1 ± 4.2 oocytes were cryopreserved. With their own stored oocytes, 44 patients returned to attempt pregnancy. From a total of 194 thawed/warmed oocytes, 157 survived (80%). In total, 100 embryos were transferred in 57 transfer/cycles, and 18 pregnancies were achieved. The pregnancy rate per transfer and pregnancy rate per patient were 31% and 41%, respectively. No statistically significant differences were observed between oncological patients and nononcological patients. A total of 15 babies were born from oncological patients. Children born showed normal growth and development. One minor malformation was detected.

Chapter 1 Historical Background on Gamete and Embryo Cryopreservation

This chapter describes the development of the science of cryopreservation of gametes and embryos of various species including human. It attempts to record in brief the main contributions of workers in their attempts to cryopreserve gametes and embryos. The initial difficulties faced and subsequent developments and triumphs leading to present-day state of the art are given in a concise manner. The main players and their contributions are mentioned and the authors' aim is to do justice to them. This work also attempts to ensure that credit is correctly attributed for significant advances in gamete and embryo cryopreservation. In general this chapter has tried to describe the historical development of the science of cryopreservation of gametes and embryos as accurately as possible without bias or partiality.

Gonadotropin-releasing hormone agonist decreases chemotherapy-induced gonadotoxicity and premature ovarian failure in young female patients with Hodgkin lymphoma

OBJECTIVE

To minimize the gonadotoxic effect of chemotherapy by the cotreatment with a GnRH agonistic analogue (GnRH-a).

DESIGN

Prospective nonrandomized study with concurrent and historical controls.

SETTING

University medical center.

PATIENT(S)

One hundred fifteen female patients with Hodgkin lymphoma (HL).

INTERVENTION(S)

Sixty-five patients received a monthly injection of GnRH-a, administered before starting chemotherapy until its conclusion, up to a maximum of 6 months. Thirty-five patients were treated with ABVD and 76 with a procarbazine-containing regimen. This group was compared with a control group of 46 women who were treated concurrently with similar chemotherapy (n = 26) without GnRH-a or were historical controls (n = 20).

MAIN OUTCOME MEASURE(S)

Cyclic ovarian function (COF) versus premature ovarian failure (POF).

RESULT(S)

The ovarian function could be determined in 111 patients. In the GnRH-a/chemotherapy group, 63 out of 65 patients resumed ovulation and regular menses (96.9 %), compared with 63% of the 46 control subjects. Twenty of the 22 patients in the BEACOPP/escalated BEACOPP/GnRH-a cotreatment resumed cyclic ovarian function versus 9 of the 14 in the chemotherapy-only group. All 17 MOPP/ABV/GnRH-a cotreated patients resumed COF versus 11 of the 22 in the chemotherapy-only group. There was no significant effect of the GnRH-a cotreatment regarding COF in the ABVD group. There were no significant differences in the cumulative doses of the various alkylating agents between the two groups.

CONCLUSION(S)

Cotreatment with GnRH-a may reduce ovarian damage significantly in female patients treated for HL and should be considered in addition to assisted reproduction for women in reproductive age receiving gonadotoxic chemotherapy.

Cryopreservation of Human Oocytes and Ovarian Tissue

Oocyte cryopreservation has the potential to be an important adjunct to assisted reproductive technologies and bypasses some ethical, moral, and religious dilemmas posed by human embryo cryopreservation. The success of human oocyte cryopreservation depends on morphological and biophysical factors that could influence oocyte survival after thawing. Among the morphological factors, the maturity, quality, size of the oocyte, the presence or the absence of the cumulus oophorus seems to play an important role in oocyte survival after thawing. The main biophysical factor of cellular disruption during cryopreservation process in the intracellular ice formation that can be avoided by an adequate cell dehydration; thus reducing the intracellular water by increasing the dehydration process we can limit the damages of the cryopreservation procedure. The dehydration process can be affected by the presence and concentration of the cryoprotectants in the freezing solutions (equilibration and loading solutions), and by the freezing and thawing rate. Two additional properties of cryoprotectants help to protect cells during slow cooling, when the cells are very dehydrated and are surrounded by concentrated salts. The cryoprotectants appear to reduce damage caused by high levels of salt, a property known as salt buffering. Some events occurring to the oocyte during cryopreservation procedure has been found to be a premature exocitosis of cortical granules, leading to an intempestive zona hardening and consequently to a reduction of fertilization rate, and the cryoinjury to the zona pellucida leading to a polispermic fertilization. ICSI is an efficient method to by pass these two events and to achieve a satisfactory outcome in terms of normal fertilization of cryopreserved oocytes. The application of the ICSI to cryopreserved oocytes did not seem to increase the degeneration rate after insemination with respect to fresh oocytes. The increased oocyte survival rate and the use of ICSI have facilitated the recent increase in the number of pregnancies and live birth.

Ovarian function preservation in the cancer patient

OBJECTIVE

To review the clinical modalities that are available to women receiving potentially sterilizing cancer therapy.

DESIGN

The MEDLINE database was reviewed for all publications on medication, surgery, or assisted reproductive technology that could potentially preserve fertility in women who are receiving cancer therapy.

CONCLUSION(S)

There are many options available to a patient undergoing a treatment that will negatively impact her fertility. Many procedures and medical interventions have been proven successful both in terms of ovarian function and pregnancy rates. Other techniques have great potential but do not have long-term clinical data. It is important that the patient's primary care physician understand the methods available to preserve fertility in cancer patients and communicate this information to the patient.

An overview of oocyte cryopreservation

The ability to cryopreserve human oocytes and store them indefinitely would be beneficial for cancer patients at risk of becoming sterile after therapy, allow women to delay reproduction, and alleviate religious concerns associated with embryo storage. In 1986, Chen was the first to report a pregnancy originating from a frozen-thawed human oocyte. Although over 100 babies have been born from oocyte storage since then, pregnancy rates remain unacceptably low. Adapting embryo cryopreservation techniques to oocyte storage has had limited success and new reproducible methods are needed. Problem areas other than intracellular ice formation and osmotic effects need to be identified. A broad approach of critical analysis should be conducted regarding the entire cryopreservation process from pre-equilibration and cooling, to thawing and stepout. All established facets deserve reanalysis in order to assess which aspects can be optimized or changed so that cellular demise can be avoided and cellular viability enhanced. New methods, including the use of choline-based media and vitrification have proven useful in increasing survival and pregnancy rates in some clinics. Other methods yet untested, such as injection of complex carbohydrates into the oocyte, deserve further studies. Vitrification research has led to the formulation of new ideas and has demonstrated the flexibility of cells to survive cryopreservation. Although successful, vitrification protocols are potentially harmful and technically challenging, due to elevated cryoprotectant concentrations and rapid cooling rates. Bovine embryo vitrification methods have been used to store human oocytes and embryos, particularly blastocysts with some success. Vitrification solutions containing high molecular weight polymers have also proved beneficial by reducing solution toxicity. In general, further advances are needed to improve human oocyte storage before widespread routine clinical use.

Reproductive strategies for human survival

Reproductive strategies for the human species have basically remained unaltered since Homo sapiens first appeared, probably in the valleys of Africa: males have always attempted to pass their genes to the largest feasible number of females, selecting those females capable of providing the best quality of oocytes; females invariably have sought a male capable of providing the best means of survival for herself and her offspring. This meant that human sexuality has been essentially conceptive, although it is reasonable to suppose that it began to lose this 'exclusive' connotation early in the cultural evolution of the species. Then, during the 20th century, major revolutions occurred: first, with the advent of contraception, sex without reproduction became a reality; then, with assisted reproduction technology, humans devised reproduction without sex; finally, very recently, women have begun to reproduce even in menopause. Additional strategies will, no doubt, soon be available, although we cannot as yet clearly see whether, or when, reproduction without sex and gametes, or in-vitro gestations will become available.

Has clinical practice been changed by the Human Fertilisation and Embryology Act 1990?

The birth in 1978 of the first baby to be conceived through in vitro fertilization caused both wonder and controversy. Concerns that this technology would be abused led the Government of the United Kingdom to appoint a Committee of Enquiry into human fertilization and embryology, which led to the publication in 1984 of what has become known as the Warnock Report. This made recommendations on the creation of human embryos in vitro, the storage of human eggs, sperm and embryos, and research on human embryos. This report led eventually to the passing by Parliament of the Human Fertilisation and Embryology Act 1990 and the creation of the Human Fertilisation and Embryology Authority, which since 1991 has licensed and regulated all centres and practitioners of assisted reproductive technology. The effects of these regulations are considered in this article. Clinical practice has been affected by the Act, but it has generally led to higher standards of clinical and laboratory practice, improved patient information and care, and improved ethical standards.

Biotechnological applications of plant freezing associated proteins

Plants use a wide array of proteins to protect themselves against low temperature and freezing conditions. The identification of these freezing tolerance associated proteins and the elucidation of their cryoprotective functions will have important applications in several fields. Genes encoding structural proteins, osmolyte producing enzymes, oxidative stress scavenging enzymes, lipid desaturases and gene regulators have been used to produce transgenic plants. These studies have revealed the potential capacity of different genes to protect against temperature related stresses. In some cases, transgenic plants with significant cold tolerance have been produced. Furthermore, the biochemical characterization of the cold induced antifreeze proteins and dehydrins reveals many applications in the food and the medical industries. These proteins are being considered as food additives to improve the quality and shelf-life of frozen foods, as cryoprotective agents for organ and cell cryopreservation, and as chemical adjuvant in cancer cryosurgery.

Freezing immature oocytes

The establishment of a long-term preservation system for mammalian oocytes is important for the development of both biological and medical sciences. A number of efforts have been made to develop this system. In human reproductive medicine, the development of an oocyte cryopreservation system can improve the efficacy of the current assisted reproductive technology (ART) for infertile patients with severe reproductive disorders. In this article, the technical development of cryopreservation programs for human oocytes and its biological background were reviewed. Clinical outcome after the use of this technology was further introduced.

Triploid pregnancy after ICSI of frozen testicular spermatozoa into cryopreserved human oocytes: case report

Although freezing oocytes is ethically more acceptable than cryopreservation of embryos, variable oocyte survival, fertilization rate and possible risk of increased ploidy after cryopreservation have precluded the widespread clinical application of oocyte cryopreservation in assisted reproduction techniques. We report a triploid pregnancy from intracytoplasmic sperm injection of recombinant FSH-stimulated frozen/thawed testicular spermatozoa into cryopreserved oocytes in a hormone replacement cycle. To our knowledge, this is the first report of a pregnancy where both gametes have been frozen. It illustrates the need for further research when applying new techniques in assisted reproduction.