In vitro maturation of human preovulatory oocytes reconstructed by germinal vesicle transfer

OBJECTIVE: To describe a micromanipulation-electrofusion procedure for transferring germinal vesicles (GVs) between immature human oocytes. DESIGN: Pilot study to assess oocyte maturation after an invasive micromanipulation procedure. SETTING: Research laboratory at a university medical center. PATIENT(S): Immature oocytes were discarded from intracytoplasmic sperm injection (ICSI)-IVF cycles of patients 23-48 years of age. INTERVENTION(S): Initially, GV removal and transfer were performed on the same oocyte; these "self-reconstructed" oocytes were then cultured in vitro for up to 50 hours and examined periodically for maturation as judged by the extrusion of the first polar body. In a second study, GVs from oocytes of "old" patients (>38 years old) were successfully transferred into enucleated immature oocytes of "young" patients (<31 years old). MAIN OUTCOME MEASURE(S): Extrusion of the first polar body was monitored in "reconstructed" and control oocytes; karyotypes also were analyzed at meiosis II. RESULT(S): From 48 oocytes from old patients, 12 GVs were successfully removed, transferred, and fused into previously enucleated oocytes from young patients. After in vitro culture, 7 of these "reconstructed" oocytes matured to meiosis II, a maturation rate not significantly different from that observed in nonmanipulated controls. A normal, second meiotic metaphase chromosome complement was observed in 4 of 5 reconstructed oocytes. CONCLUSION(S): Normal meiosis can occur after the transfer of a GV into an enucleated host oocyte. Germinal vesicle transfer may be a valuable research procedure that generates cell models to characterize the cytoplasmic-nuclear interplay for cell cycle regulation, maturation, and fertilization in the human oocyte; it also may be a potentially attractive alternative to oocyte donation.     

Preservation of Fertility in Women Undergoing Chemotherapy: Current Approach and Future Prospects

Purpose: Anticancer treatment causes ovarian failure. Methods: Some hormones may have a protective effect on the ovary. Cryopreservation (freezing) of oocytes has had very limited success, and therefore, currently its use before chemotherapy is not a feasible option. However, cryopreservation of embryos is possible. Another solution is oocyte donation followed by in vitro fertilization (IVF). Results: Ovarian cortical slices containing primordial follicles have been cryopreserved successfully. To restore fertility, cryopreserved–thawed tissue taken from cancer patients before therapy could be replanted after recovery. The possible risk of malignancy restoration could be eliminated by obtaining unilaminar follicles from cryopreserved–thawed tissue and growing them in vitro, followed by routine IVF. Conclusions: Although women who undergo chemotherapy face limited options for fertility preservation, intensive studies in cryopreservation and in vitro maturation of follicles harbor hope for brighter prospects in the future.     

Oocyte-induced haploidization

This paper describes the technical approach to treatment of age-related oocyte aneuploidy. Although one solution can be oocyte/embryo selection, another is represented by the nuclear transplantation procedure. The efficiency of nuclear transplantation into immature oocytes is described as a way of generating embryos, and the possibility that viable female gametes can be constructed by transfer of diploid somatic cell nuclei into enucleated oocytes. Germinal vesicle (GV)-stage mouse oocytes were collected from unstimulated ovaries and somatic nuclei were obtained from mouse cumulus cells obtained after ovarian stimulation. Spare human GV-stage oocytes were donated from consenting patients undergoing intracytoplasmic sperm injection (ICSI) treatment, and human somatic cells were stromal cells coming from uterine biopsies performed on consenting patients undergoing endometrial cell co-culture. GV ooplasts, prepared by enucleation, were transplanted with either GV or somatic nuclei by micromanipulation. Grafted oocytes were electrofused and cultured to allow maturation, following which they were selected at random for insemination or cytogenetic analysis. GV transplantation was accomplished with an overall efficiency of approximately 80 and 70% in the mouse and the human respectively. The maturation rate of 96% (mouse) and 62% (human) following reconstitution was comparable to that of control oocytes, as was the incidence of aneuploidy among the reconstituted oocytes. The reconstituted human oocytes were successfully fertilized by ICSI at a rate of 52%. After the transfer of mouse cumulus or human endometrial cell nuclei into enucleated immature oocytes, a polar body was extruded in >40%. In a limited number of observations where the nucleus of an aged oocyte was transferred into a younger ooplasm, the chromosomes segregated normally at the time of polar body extrusion. The technique of nuclear transplantation itself did not increase the incidence of chromosomal anomalies in the mouse or human, since their oocytes reconstituted with homologous donor GV resumed meiosis to metaphase II and maintained a normal ploidy. In addition, immature mouse ooplasts induced haploidization of transplanted somatic cell nuclei. Although further evaluation of their genetic status is needed, the procedure may offer a realistic way of producing normal oocytes in cases of aged-related infertility. While the procedure is technically similar to cloning, it would generate a unique individual as a result of the contribution of both parental genomes.     

In-vitro-Maturation

The ability to rescue oocytes and mature them in vitro would provide invaluable information about folliculogenesis and oocyte maturation and could provide oocytes for infertile women. In vitro growth (IVG) of follicles and in vitro maturation (IVM) of oocytes are challenging especially in the human because folliculogenesis is a lengthy process with many complex cellular changes in the oocyte and its surrounding follicle cells. Reports have been published on live births in mice after maturation and fertilization. This technique is still in its infancy especially for use in humans. A few live births have resulted from IVM of immature human oocytes aspirated from small antral follicles. Furthermore, it is possible to grow primordial follicles to preantral stages in slices of ovarian tissue and support antrum formation in isolated preantral follicles. Today we are still a long way from growing and maturing preantral follicles to preovulatory stages in vitro, but these techniques may revolutionize assisted reproduction in the future.     

Cryopreserved Immature Mouse Oocytes: A Chromosomal and Spindle Study

Purpose: Cryopreservation of human oocytes might provide an alternative approach to freezing supernumerary embryos obtained during IVF. This process, performed on immature denuded prophase I mouse oocytes, was investigated. Methods: We first investigated the capacity of frozen, immature, murine oocytes to continue in vitro maturation after thawing. We then evaluated the risk to offspring from chromosomal damage by cytogenetical and cytological (spindle) analysis. Finally, we attempted to determine the reasons for and the stage of maturation failure. Results: A total of 700 immature oocytes was frozen, 629 (90%) were recovered intact after thawing, and 53% extruded the first polar body, versus 74% for the control group. Freezing was not accompanied by an increase in aneuploidy in maturing oocytes (18 and 15% for thawed and control oocytes, respectively). Consequently, the first meiotic division occurred normally, without an increase in nondisjunction. Spindle analysis demonstrated only a few abnormalities (15 and 2% for thawed and control oocytes, respectively) incompatible with further development. Oocytes arrested during in vitro maturation were mainly at the metaphase I stage (64 and 76% for thawed and control oocytes, respectively). Whereas 17% of thawed oocytes were blocked before the formation of the first meiotic spindle, this never occurred in the control group. Conclusions: Immature murine oocytes can withstand cryopreservation, which is encouraging for future human application of this technique.     

Interactions of the meiotic spindle with mitotic chromosomes in GV mouse oocytes

During mitosis, a spindle checkpoint detects chromosome misalignment and halts the cell cycle progression. In meiosis of female germ cells, however, it is debatable whether such a checkpoint is present. This research employed a unique model in the mouse, mitotic chromosomes transferred to meiotic cytoplasts to investigate whether a meiotic oocyte's microtubule apparatus can effectively separate mitotic metaphase chromosomes, and whether a spindle checkpoint exists during its division. The intact germinal vesicle (GV) oocytes, enucleated GV cytoplasts, and enucleated GV cytoplasts at 15 h in-vitro maturation were transferred with a metaphase fibroblast cell. When mitotic chromosomes were transferred into enucleated or intact mouse GV oocytes, the first bipolar meiotic spindles were established and the reconstructed oocytes were able to extrude polar bodies. However, none of the reconstructed oocytes showed complete and accurate alignment of chromosomes, except the enucleated GV cytoplasts reconstructed after maturation. The spindle formation and polar body extrusion suggest that the first meiotic spindle was functional, and the chromosome misalignment did not prevent the onset of anaphase. The data indicate that a spindle checkpoint, providing surveillance of misaligned chromosomes, was overridden or compromised by the incompatibility between somatic chromosomes and meiotic spindles during the first meiotic division.     

Oocyte diameter predicts the maturation rate of human immature oocytes collected ex vivo

PurposeTo study the impact of oocyte diameter and cumulus cell mass on the potential for final maturation of immature human oocytes in vitro.MethodsImmature oocytes (n = 1563) from 75 women undergoing fertility preservation by ovarian tissue cryopreservation (14–41 years) were collected. After preparation of the ovarian cortex for freezing, immature oocytes were collected from the surplus medulla. After collection, IVM was performed according to standard published methods. The mass of cumulus cell surrounding the immature oocyte was grouped according to size. After IVM, each oocyte was photographed, measured, and the diameter was calculated as a mean of two perpendicular measurements.ResultsThe diameter of the oocytes ranged from 60 to 171 µm with a mean of 115 µm (SD:12.1) and an interquartile range from 107 to 124 µm. The oocyte diameter was positively associated with a higher incidence of MII (p < 0.001). MII oocytes had a significantly larger mean diameter than MI, GV, and degenerated oocytes. The size of the cumulus cell mass was significantly associated with the MII stage (p < 0.001) and larger oocyte diameter (p < 0.001). The results further confirm that the diameter of the fully grown oocyte is reached relatively early in human follicular development and that the factors governing oocyte maturation in vitro are connected to the surrounding cell mass and the oocyte.ConclusionThe diameter of the oocyte is a highly determining factor in the nuclear maturation of the human oocyte during in vitro maturation, and the size of the cumulus cell mass is closely positively associated with a larger diameter.     

Recovery and Maturation of Immature Oocytes in Patients at Risk for Ovarian Hyperstimulation Syndrome

Purpose: Our purpose was to examine the rate of immature oocyte recovery and their potential for in vitro maturation from canceled human menopausal gonadotropin cycles due to the risk of having ovarian hyperstimulation syndrome develop. Methods: Patients underwent ultrasound-guided immature oocyte pickup. The number of oocytes recovered from these patients was recorded, and then cultured in vitro. Cumulus expansion and the stage of nuclear maturation were observed after 24 and 48 hr, respectively. Results: Seventeen patients underwent 20 immature oocyte recoveries. A total of 162 oocytes (8.1 oocytes/patient) was obtained. All of the oocytes were enclosed in dense layers of cumulus cells. Among them, 78.4% showed cumulus expansion after 24 hr and 66% completed meiotic maturation to metaphase II after 48 hr in culture. There was only one immature oocyte pickup in which no oocytes were recovered (95% recovery rate). None of the patients had ovarian hyperstimulation syndrome develop. Conclusions: Immature oocytes can be recovered from canceled human menopausal gonadotmpin cycles in patients who are at potential risk for severe hyperstimulation syndrome. These oocytes can be matured in vitro and can be used for clinical and research purposes as well.     

Pregnancy and delivery after in vitro maturation of naked ICSI GV oocytes with GH and transfer of a frozen thawed blastocyst: case report

Purpose : To determine if GV oocytes, collected at the time of ICSI, can be matured in vitro and rescued for therapeutic treatment. A patient for whom all the collected oocytes at the GV stage after a classical COH protocol were matured in vitro with GH. Method : All the naked oocytes were matured in a culture medium (ISM2) containing 15% patient serum +1.6 units of GH (Saizen) per millilitre. Oocytes were incubated overnight at 37°C. The MII oocytes obtained were micro-injected. A fresh transfer was performed and a supernumerary blastocyst was frozen. Results : The patient was pregnant and delivered a healthy girl after transfer of the frozen/thawed blastocyst. The baby girl is now 2 years old. Conclusion : In vitro maturation with GH allows rescuing naked GV oocytes collected at the time of ICSI. GH action does not pass through the cumulus cells. According to the possible lack of synchrony between the embryo and the uterus, we recommend to freeze the embryos obtained and to replace them in a controlled cycle.     

In vitro development of ovarian follicles

Tissue banking of ovarian material is being increasingly offered to a variety of patients as a means of fertility preservation. This tissue comprises thin cortical surface biopsies that contain predominantly primordial follicles, and currently the only option to restore fertility is by transplantation. However, this is not a viable option for all patients. The potential of this tissue could be realized by the development of in vitro systems to support complete growth from the early primordial stages through to maturity. This technology would have many therapeutic applications including the production of competent oocytes for assisted reproduction technologies, determination of toxicological effects on germ cell development, assessment of cryopreserved ovarian tissue before transplantation for fertility preservation as well as providing an experimental model to address basic scientific questions concerning human oocyte development. Complete oocyte development in vitro from the primordial stage has been achieved in mice, but the larger size and longer growth period of human follicles has made the interspecies translation of these techniques difficult. Recently progress has been made in defining conditions that support different stages of follicle development in vitro that make a complete in vitro system from primordial to maturation a possible reality. This article deals with our current understanding of in vitro development.     

Correlation between human follicular diameter and oocyte outcomes in an ICSI program

Purpose: To determine the correlation between the follicular sizes and oocyte recovery, metaphase II oocyte recovery, fertilization rate and good embryo quality from mature and immature oocytes in an intracytoplasmic sperm injection (ICSI) program. Methods: 991 follicles obtained from 72 ICSI cycles were classified into three groups according to their diameters as measured by transvaginal ultrasound including group A (<10 mm), group B (10–14 mm), and group C (>14 mm). All obtained oocytes were classified according to their nuclear maturation: germinal vesicle (GV), metaphase I (MI) and metaphase II (MII). Mature oocytes underwent ICSI while immature oocytes were further cultured until maturity before ICSI was performed. The rates of fertilization and good quality embryos at day 3 were evaluated. Results: A progressive and significant increase in the rates of oocyte recovery and MII oocyte recovery were observed from group A follicles compared to the other groups (p < 0.001). The fertilization rate of mature and in vitro matured oocytes, as well as the rate of good quality embryos showed a tendency to increase from group A to group C follicles, but not significantly. The corresponding fertilization rates were 78 and 55.3% (p < 0.001) for mature and in vitro matured oocytes, respectively. Conclusion: Collection of oocytes from small follicles, especially with a mean diameter less than 10 mm, and in vitro maturation of immature oocytes before fertilization may allow the total number of good quality and transferable embryos to be increased.     

Successful delivery following cryopreservation of zygotes produced by in vitro matured oocytes retrieved from a woman with polycystic ovarian syndrome-like disease: a case report

Purpose : To estimate frozen zygotes, which developed from in vitro matured oocytes retrieved from polycystic ovarian syndrome-like disease. Methods : Oocyte retrieval was performed on Day 15 following withdrawal bleeding. The oocytes were incubated for 24 h in TCM-199 maturation medium supplemented with follicle fluid, E2, FSH, and hCG. Results : A total of 12 immature oocytes were collected. Seven of the 12 oocytes (58.3%) developed to the metaphase-II stage, and subsequently, all seven fertilized oocytes were frozen at the pronuclear stage. The remaining five oocytes failed to develop to the metaphase-II stage after an additional 24 h of incubation. Three of seven cryopreserved oocytes were thawed and developed to 2–8-cell cleaved stage embryos. The first pregnancy failed. However, the second frozen–thawed embryo transfer resulted in the delivery of healthy twins. Conclusions : Successful delivery using frozen zygotes from an anovulatory woman with polycystic ovarian syndrome-like disease.     

In vitro maturation of baboon oocytes retrieved at the time of cesarean section

Objective: To investigate the feasibility of oocyte retrieval at the time of cesarean delivery and the potential of such oocytes to undergo nuclear maturation in vitro using a baboon model and an established culture system.

Design: Randomized, controlled animal study.

Setting: Research foundation and university research laboratory.

Animal(s): Mature pregnant baboons.

Intervention(s): In vitro culture of aspirated oocytes with or without epidermal growth factor (EGF).

Main Outcome Measure(s): Oocyte yield, germinal vesicle breakdown, polar body extrusion.

Result(s): A total of 246 oocytes were retrieved (mean, 35; range, 14–67). Eighty-seven oocytes (35%) underwent germinal vesicle breakdown and 72 oocytes (29%) extruded a polar body. A χ² analysis revealed no significant effect of EGF on outcome parameters. No effect of gestational age or maternal age on oocyte yield or development was observed.

Conclusion(s): A sizeable proportion of oocytes obtained from puerperal primates exhibited the capacity to undergo nuclear maturation in vitro.     

Reduced In Vitro Fertilization of Human Oocytes Correlates with Raised Circulating FSH Levels During Ovarian Stimulation in Normogonadotropic Women Downregulated with GnRH-Analogues

Purpose: The possible effects of circulating FSH levels as used during IVF treatment on oocyte maturation and subsequent preembryo development were evaluated. Methods: Serum levels of FSH and LH on days 1 and 8 of ovarian stimulation and on the day of oocyte retrieval (OR) were correlated with subsequent preembryo development in vitro. After pituitary downregulation, 244 normogonadotropic women followed a fixed protocol for the first 7 days of stimulation. Results: The average FSH concentration on day 8 of stimulation was 11.5 IU/L and exceeded the expected midcycle surge of FSH by more than 25%. In contrast, levels of LH were below an average of 2 IU/L throughout the stimulation period. The concentration of FSH on day 8 and on the day of OR showed a significant inverse correlation with cleavage rate, whereas levels of LH, age, and body mass index showed no such correlation. Conclusions: Supraphysiologic levels of FSH seems to affect oocyte maturation negatively. Premature resumption of meiosis, leading to retrieval of postmature oocytes with a reduced developmental potential, is suggested as the underlying mechanism.     

Oncofertility case report: live birth 10 years after oocyte in vitro maturation and zygote cryopreservation

PurposeThis study aims to report a case of urgent fertility preservation in an oncological patient with collection of immature oocytes in the absence of ovarian stimulation that, through in vitro maturation (IVM), followed by ICSI and cryopreservation of zygotes resulted, 10 years later, in the live birth of a healthy baby.MethodsIn September 2008, our clinic performed IVM in a 32-year-old woman diagnosed with a ductal invasive carcinoma with positive estradiol receptors, negative progesterone receptors and positive human epidermal growth factor receptor 2. The retrieval of immature oocytes was performed in the absence of ovarian stimulation after a simple mastectomy and prior to any chemotherapy treatment. The compact cumulus-oocyte complexes (COCs) collected were placed in Lag medium for 2 h, followed by incubation in IVM medium, supplemented with heat inactivated patient serum, recombinant FSH, and recombinant LH. After 30 h in culture, cumulus cells were removed, the metaphase II oocytes were microinjected, and the zygotes obtained were cryopreserved. In 2017, the zygotes were thawed and cultured until day 3. One embryo was transferred and the other cryopreserved.ResultsFour compact COCs were collected and subjected to IVM. Two oocytes reached metaphase II and were microinjected. Two zygotes were obtained and were cryopreserved at the two pronuclear stage. Approximately 9 years later, the two zygotes were thawed and cultured until day 3. An embryo with 10 cells was transferred and implanted, resulting in the birth of a healthy baby.ConclusionsIn cases where urgency to start adjuvant therapy requires immediate oocyte collection, IVM may be the only option to obtain fully competent mature oocytes allowing for effective preservation of the reproductive potential.     

Second polar body extrusion is highly predictive for oocyte fertilization as soon as 3 hr after intracytoplasmic sperm injection (ICSI)

Objective Our objective was to evaluate the time course and the predictive value of the extrusion of the second polar body after intracytoplasmic injection (ICSI) related to the fertilization rate, embryo cleavage and quality.Setting The setting was the in vitro fertilization program of a university hospital.Patients Twenty-one patients were treated with intracytoplasmic single sperm injection either for fertilization failure in IVF, low fertilization in IVF (<5%), or severe male factors.Design One hundred thirty-five of 205 metaphase 2 oocytes treated with intracytoplasmic single sperm injection were observed 1, 2, and 3 hr after the assisted fertilization procedure. Extrusion of the second polar body was recorded. For each of these oocytes, fertilization was noted 18 hr after ICSI and cleavage and embryo quality were assessed 24 hr later. The 70 remaining oocytes were used to assess a possible negative effect of repeated exposure to light microscopy.Results The extrusion of the second polar body 3 hr after injection was an observation with a sensitivity of 0.87, a specificity of 0.58, and a high positive predictive value (0.90) toward oocyte fertilization. Twenty-nine and four-tenths percent of the oocytes extruded a second polar body within the first hour, 56.6% within the first 2 hr, and 78.3% had a second polar body 3 hr after injection. This time course was related neither to the speed of embryo cleavage nor to the embryo quality. Fertilization, cleavage, and embryo quality were not affected by repeated observation as deduced from comparison with the control group and confirmed by a high pregnancy (62% per oocyte retrieval) and implantation rate (22% per replaced embryo).Conclusion Oocytes can be checked, in all safety, 3 hr after a single sperm injection for the presence of a second polar to predict oocyte fertilization with a high certainty.     

Downregulation of gene expression and activity of GRIM-19 affects mouse oocyte viability,maturation, embryo development and implantation

PurposeTo investigate the expression of GRIM-19 (Gene associated with retinoid-interferon-induced mortality 19) in mouse oocytes and preimplantation embryos, and to study the effect of GRIM-19 on the developmental competence of mouse oocytes and embryos.MethodsGRIM-19 was evaluated at both mRNA and protein levels. The expression of GRIM-19 gene was downregulated in mouse oocytes cultured in vitro by specific small interfering RNA (siRNA) injection, while the activity of GRIM-19 was decreased by microinjection of a GRIM-19 antibody into the cytoplasm of germinal vesicle (GV) oocytes. Oocytes matured in vitro were then fertilized by intracytoplasmic sperm injection (ICSI), followed by observation and evaluation of fertilization rate, cleavage rate, blastocyst formation rate and implantation rate.ResultsGRIM-19 is expressed throughout oocyte maturation and preimplantation embryo development stages. GRIM-19 was localized primarily in the cytoplasm of all cells examined. Downregulation of gene expression and activity of GRIM-19 resulted in decreased oocyte viability, potency of oocyte maturation, embryo development and implantation.ConclusionsGRIM-19 may play important roles in mouse oogenesis and early embryonic development and implantation.     

Improved maturation competence of ovarian tissue oocytes using a biphasic in vitro maturation system for patients with gynecological malignancy: a study on sibling oocytes

Purpose

To investigate the developmental competence of ovarian tissue oocytes from patients with gynecological tumors using a biphasic in vitro maturation system with capacitation (CAPA-IVM) in comparison with standard IVM.

Methods

This sibling pilot study included 210 oocytes in 10 patients with gynecological malignancies. After ovariectomies, ovaries were cut into even halves and immature cumulus-oocyte complexes (COCs) were retrieved from the ovarian tissue. COCs were separately cultured in either a biphasic CAPA-IVM system for 53 h or in standard IVM for 48 h. After IVM, all COCs were denuded and mature oocytes were either vitrified (N=5) or used for ICSI (N=5). Embryos were cultured for 5–6 days and obtained blastocysts were vitrified.

Results

Use of the CAPA-IVM system led to a higher meiotic maturation rate in ovarian tissue oocytes (OTO) compared to standard IVM (56 vs 35%, p=0.0045) and had a tendency to result in lower degeneration after IVM. Only the CAPA-IVM method supported blastocyst formation.

Conclusions

The biphasic in vitro maturation system improved the competence of OTO in comparison to the standard IVM method. The study suggests that fertility preservation programs could become more efficient using IVM after capacitation culture.