Maturation in vitro of human oocytes from unstimulated cycles: selection of the optimal day for ovum retrieval based on follicular size

In vitro maturation (IVM) of human immature oocytes: is it still relevant?

In vitro maturation (IVM) of human immature oocytes has been shown to be a viable option for patients at risk of ovarian hyperstimulation syndrome (OHSS), those seeking urgent fertility preservation and in circumstances where controlled ovarian stimulation is not feasible. Moreover, IVM techniques can be combined with ovarian tissue cryobanking to increase the chances of conception in cancer survivors. The clinical applications of IVM in the field of reproductive medicine are rapidly expanding and the technique is now classified as non-experimental. In contrast to conventional IVF (in vitro fertilization), IVM offers several advantages, such as reduced gonadotropin stimulation, minimal risk of ovarian hyperstimulation syndrome (OHSS), reduced treatment times and lower costs. However, the technical expertise involved in performing IVM and its lower success rates compared to traditional IVF cycles, still pose significant challenges. Despite recent advances, such as innovative biphasic IVM systems, IVM is still an evolving technique and research is ongoing to refine protocols and identify techniques to improve its efficiency and effectiveness. A comprehensive understanding of the distinct mechanisms of oocyte maturation is crucial for obtaining more viable oocytes through in vitro methods, which will in turn lead to significantly improved success rates. In this review, the present state of human IVM programs and future research directions will be discussed, aiming to promote a better understanding of IVM and identify potential strategies to improve the overall efficiency and success rates of IVM programs, which will in turn lead to better clinical outcomes.

Effect of dominant follicle status at the time of retrieval on the clinical outcomes in natural cycle IVF combined with immature oocyte treatment

Objective: It is commonly believed that the oocytes from small follicles are unhealthy when a dominant follicle (DF) is recruited in the ovaries, especially when the DF is ovulated. This study aims to confirm whether the presence or ovulation of DF at the time of retrieval affects the clinical outcome of the natural cycle IVF with in vitro maturation (NC-IVF/M) treatment.

Methods: Data were collected from 446 women with regular menstrual cycle and 536 retrieval cycles using NC-IVF/M treatment. The cycles were divided into three groups based on the results of the oocyte retrieval cycle. Group A covers the collection of oocytes from the DF and small follicles; Group B incorporates failed oocyte retrieval from DF and then the oocytes are retrieved only from small follicles; and Group C includes the retrieval of oocytes only from small follicles accompanied with an ovulated DF. Furthermore, Group B and C have subgroups to include whether in vivo matured oocytes were obtained from small follicles. Following aspiration of DF and small follicles, mature oocytes were inseminated on the date of retrieval by intracytoplasmic sperm injection (ICSI) and the immature oocytes were matured in vitro. If the immature oocytes were matured in vitro, they were inseminated using ICSI, and then the embryos obtained from in vivo and in vitro matured oocytes were transferred accordingly.

Results: The oocytes from DF were successfully retrieved in 445 cycles (83.0%), failed to be retrieved in 54 cycles (10.1%) and ovulated in 37 cycles (6.9%). In Group A, an average of 2.0 ± 1.7 mature oocytes were retrieved, which was significantly higher than the average of Group B, with 1.3 ± 1.3 matured oocytes and Group C, with an average of 1.1 ± 1.5 matured oocytes (P < 0.01). However, the average number of immature oocytes retrieved from each group show no difference among the three groups. There was no significant difference in maturation rates of immature oocytes, fertilization rates among the three groups. The clinical pregnancy rate per transfer cycle is 34.5%, 34.6% and 25.7% in Group A, B and C, respectively. No significant differences were observed in embryonic development and implantation capacity in Group B and C in comparison to Group A. And there was no significant difference in clinical pregnancy, implantation, live birth and miscarriage rates among the three groups. No significant differences were observed in the developmental and implantation capacity according to with or without in vivo matured oocytes were retrieved in Group B and Group C.

Conclusion: The presence or ovulation of the dominant follicle from the ovaries does not significantly influence the developmental and implantation capacity of immature oocytes retrieved from small follicles, suggesting that NC-IVF/M is a promising treatment option for women without ovarian stimulation.

Factors Influencing the In Vitro Maturation (IVM) of Human Oocyte

In vitro maturation (IVM) of oocytes is a promising assisted reproductive technology (ART) deemed as a simple and safe procedure. It is mainly used in patients with impaired oocyte maturation and in fertility preservation for women facing the risk of losing fertility. However, to date, it is still not widely used in clinical practice because of its underperformance. The influencing factors, such as biphasic IVM system, culture medium, and the supplementation, have a marked effect on the outcomes of oocyte IVM. However, the role of different culture media, supplements, and follicular priming regimens in oocyte IVM have yet to be fully clarified and deserve further investigation.

In vitro maturation: a committee opinion

The results of in vitro maturation (IVM) investigations suggest the potential for wider clinical application. This document discusses the efficacy of IVM as reported in the published literature to date. This document replaces the document of the same name, last published in 2013.

In Vitro Maturation, Fertilization, and Culture of Pig Oocytes and Embryos

Assisted reproductive technologies in the pig are critical for the production of genetically modified pigs as models of human disease and to improve production agriculture. Methods of oocyte maturation, fertilization, and culture all play an extremely important role in how the embryo, fetus, and offspring will develop. In this chapter, we discuss the historical methods and recent advances that have been essential in promoting efficient and competent embryo development. Here we describe the procedures that can be used to mature, fertilize, and culture pig embryos to the blastocyst stage.

Analysis of meiotic spindle and zona pellucida birefringenceof IVM oocytes in PCOS patients

BACKGROUND/AIM

Polycystic ovarian syndrome (PCOS) is one of the most common causes of infertility. One of the best therapeutic options for PCOS patients is intracytoplasmic sperm injection (ICSI). In vitro maturation (IVM) can also be a useful technique for these women. The goal of this study was to evaluate both the zona pellucida (ZP) birefringence and meiotic spindle (MS) of in vivo- and in vitro-matured oocytes from PCOS patients using the PolScope system.

MATERIALS AND METHODS

Immature oocytes undergoing IVM and MII oocytes were obtained from PCOS patients in an ICSI program. Using PolScope, the presence of MS and ZP birefringence was assessed in both in vivo-matured oocytes (n = 32) and IVM oocytes (n = 24). Oocytes were classified as having highly birefringent (HB) ZP and lowly birefringent (LB) ZP. Furthermore, the rates of fertilization after ICSI were evaluated.

RESULTS

The maturation rate was 68.5% after IVM. The percentage of a HB-ZP was significantly higher in the IVM oocytes than in vivo-matured ones (58.3% vs. 31.2%, respectively; P = 0.04). There were similar outcomes for the fertilization rates and MS detection between the two groups (P = 0.80 and P = 0.53, respectively).

CONCLUSION

Clinical IVM is a safe technology for the maturation and maintenance of oocyte integrity in PCOS patients. The use of the noninvasive PolScope is recommended for detection of healthy oocytes in ICSI.

Chromosome constitution of human embryos generated after in vitro maturation including 3-isobutyl-1-methylxanthine in the oocyte collection medium

STUDY QUESTION

Do cleavage-stage embryos obtained from oocytes matured in vitro after pre-incubation with a phosphodiesterase inhibitor (IBMX) carry more chromosomal abnormalities than those generated from oocytes matured in vivo?

SUMMARY ANSWER

The rate and type of chromosomal abnormalities in normally developing cleavage-stage embryos generated with an in vitro maturation (IVM) system including pre-incubation with IBMX are not different from those observed in supernumerary embryos obtained from oocytes matured in vivo.

WHAT IS KNOWN ALREADY

Very limited information is available about the chromosomal constitution of IVM embryos. Previous studies were carried out using FISH on single biopsied blastomeres or arrested whole embryos and only provided fragmentary information on chromosomal abnormalities in IVM embryos. There is no systematic study of chromosomal abnormalities in all blastomeres of human Day 3 embryos with good morphology.

STUDY DESIGN, SIZE, DURATION

Between July 2012 and December 2012, 16 young (age <35 years old) egg donors underwent 18 IVM cycles for the generation of research embryos. Eighteen embryos developed to Day 3 and were analysed using array comparative genomic hybridization (aCGH).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Immature oocytes were retrieved from 2 to 10 mm follicles after mild ovarian stimulation with gonadotrophins but without hCG ovulation trigger. At collection, oocytes were pre-incubated with 3-isobutyl-1-methylxanthine (IBMX), a phosphodiesterase inhibitor and matured in vitro. After IVM culture, mature oocytes were microinjected with sperm from a single donor. Embryos were cultured to Day 3 after ICSI and all blastomeres of 18 good-morphology embryos were collected individually for aCGH.

MAIN RESULTS AND THE ROLE OF CHANCE

Oocyte maturation rate in vitro was 50.2% (120/239). The mean fertilization rate was 68.3% (82/120) and 30.5% (25/82) of fertilized oocytes developed into a morphologically good quality embryo on Day 3 after ICSI. Of these, 18 embryos that developed well up to Day 3 were analysed using aCGH. Eighty of the 123 blastomeres analysed showed at least one chromosomal abnormality. Three out of eighteen embryos had completely normal cells. A single embryo carried a meiotic abnormality, 11 embryos were mosaic and three were chaotic. Although the aneuploidy data of this study are too limited to allow statistical analysis, these data are comparable to our own published data on the chromosome constitution of whole day 3 and day 4 embryos after conventional ART.

LIMITATIONS, REASONS FOR CAUTION

Array CGH technology determines relative quantification of chromosomal domains but does not allow for the visualization of chromosomal rearrangements, assessment of ploidy or detection of uniparental isodisomy. Conclusions drawn on segmental abnormalities should be treated with caution. Although the limited number of embryos analysed here precludes firm conclusions, they provide valuable data on possible causes of the reduced potential of IVM embryos.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study to describe the complete chromosome complement of all single blastomeres of good-morphology day 3 embryos obtained with IVM (including the presence of IBMX in a pre-incubation medium). The results demonstrate that a high proportion of good-morphology embryos are aneuploid and that there is no obvious increase in aneuploidies as a result of IVM which seems to suggest that the reduced efficiency of IVM technology compared with standard IVF may be accounted for by factors other than aneuploidy, such as cytoplasmic defects or reduced endometrial receptivity.

STUDY FUNDING/COMPETING INTERESTS

This study was funded by the TBM (Applied Biomedical Research with Societal Finality) programme of the IWT (Agency for Innovation through Science and Technology - Flanders, 110680) and by a Methusalem grant of the Vrije Universiteit Brussel. C.S. is a post-doctoral fellow of the Fund for Scientific Research Flanders (FWO - Vlaanderen). K.J. is a PhD student funded by the FWO. The University of Adelaide owns a patent family associated with IVM technologies that is licensed to Cook Medical. R.B.G. and J.G.T. are inventors. The remaining authors have no conflict of interest to declare.

Comparison of blastocyst and Sage media for in vitro maturation of human immature oocytes

In vitro maturation (IVM) of human oocytes is an attractive alternative to conventional assisted reproductive technology (ART) treatment, as it involves no or minimal ovarian stimulation. Currently, commercialized media specifically designed for IVM are often used. These media are expensive, have limited shelf life, and must be ordered in advance. If standard culture media can be used in place of the specialized IVM media, it would simplify management and make IVM more feasible and more widely employed in ART centers around the world, especially in developing countries where resources are scarce. This study was, therefore, conducted to test the hypothesis that blastocyst medium was as good as commercial IVM medium to support maturation and developmental competence of human immature oocytes as previously shown in the mouse system. Immature oocytes were obtained by needle aspiration from 89 pregnant women during cesarean deliveries between April 2012 and February 2013. Sibling oocytes were allocated to Sage IVM media (512 oocytes) or blastocyst medium (520 oocytes) and assessed for maturation 36 hours later. Mature oocytes were inseminated by intracytoplasmic sperm injection and cultured up to 144 hours. There was no difference in maturation rate (65.0% vs 68.7%; P = .218) or fertilization rate (66.9% vs 66.4%; P = .872) of oocytes matured in vitro in both media. There was also no difference in the formation of good-quality blastocysts (46.6% vs 45.9%; P = .889) in the 2 groups. Further study should be done to ascertain implantation and pregnancy potential of these embryos.

Fertilization and embryo development with spermatozoa obtained from testicular sperm extraction into oocytes generated from human chorionic gonadotropin-primed in vitro maturation cycles

OBJECTIVE

To evaluate the fertilization rate and embryo development resulting from intracytoplasmic sperm injection (ICSI) of spermatozoa retrieved by testicular sperm extraction (TESE) in hCG-primed in vitro maturation (IVM) cycles.

DESIGN

Case-control study.

SETTING

University teaching hospital.

PATIENT(S)

Twenty-four IVM cycles were performed in 21 patients (mean age, 32.3 ± 2.4 years) with polycystic ovaries (PCO) whose partners were nonobstructive azoospermic. Twelve cycles where IVM oocytes were also retrieved were compared with a control group consisting of age-matched IVM cycles with ICSI using ejaculated spermatozoa (n = 12).

INTERVENTION(S)

In vitro maturation treatment with TESE sperm.

MAIN OUTCOME MEASURE(S)

Fertilization and embryo development between sibling oocytes matured in vivo and in vitro.

RESULT(S)

Eight singleton pregnancies and one twin pregnancy were obtained after ET (9/24, 37.5%). In the 12 IVM cycles where in vivo-matured oocytes were also obtained, the fertilization rate after TESE-ICSI was significantly higher in in vivo-matured oocytes than in sibling in vitro-matured oocytes (84.2% vs. 53.2%). The proportion of good quality embryos was also higher (63.5% vs. 40.2%). In the control group of cycles with ejaculated spermatozoa, there was no difference in fertilization rates between sibling oocytes matured in vivo and in vitro (84.6% vs. 79.6%).

CONCLUSION(S)

Our results suggest that IVM of immature oocytes combined with TESE-ICSI is an option for couples with PCO and azoospermia. However, there are lower fertilization and good quality embryo rates achieved when TESE-ICSI was done with in vitro-matured oocytes. Additional studies are necessary to determine the role of this treatment combination.

Developmental potential of human oocytes matured in vitro followed by vitrification and activation

Background

Oocyte in vitro maturation (IVM) and cryopreservation at the time of routine ovarian tissue freezing may be offered to cancer patients as an additional option for fertility preservation. This study aimed to investigate the developmental capacity of oocytes isolated from unstimulated ovaries.

Methods

Immature oocytes (n = 63) from seven consenting premenopausal patients were analysed. Oocytes were collected during routine laparoscopic examination with biopsy of an ovary (cystic adnexal mass, n = 3; cervical adenocarcinoma, n = 2) or oophorectomy (sex reassignment surgery, n = 2) without previous stimulation of the ovaries. The stage of the patient’s menstrual cycle was not considered. Oocytes in all visible antral follicles were aspirated from ovaries, cultured in IVM medium and vitrified at the MII stage before being kept in liquid nitrogen for at least one month. After warming, oocytes were subjected to parthenogenetic activation by chemical stimulus. Their further development was recorded at intervals of 24 hours for up to 6 days of culture.

Results

61.9% of oocytes matured in vitro within 48 hours. The survival rate after vitrification and warming was 61.5%. A total of 75% of surviving oocytes were able to respond to artificial activation, 44.4% of the parthenotes developed to early embryonic stage. However, only 1 in 18 (5.6%) of the resulting embryos reached blastocyst stage.

Conclusions

Oocytes matured in vitro from unstimulated ovaries seem to have limited developmental potential after cryopreservation and artificial activation. Although the outcome of IVM for non-stimulated oocytes is poor, it is currently the only chance besides cryopreservation of ovarian tissue for women for whom ovarian stimulation is not possible due to life circumstances. Based on our preliminary results, we suggest that the use of cryopreserved ovaries for fertility preservation in women with cancer warrants further investigation.

Controversies in IVM

PURPOSE

To explore four areas of controversy: the benefits of gonadotropin priming, benefits and timing of hCG trigger as well as the ideal protocols for endometrial preparation and luteal support.

METHODS

A literature review was performed to explore the current evidence

RESULTS

Current evidence suggests that Gonadotropin priming in combination with hCG prior to collection benefits patients with normal ovaries. In PCOS patients 10,000 IU hCG 38 h before retrieval increases the total number and rate of oocyte maturation. Gonadotropin priming may also benefit PCOS patients. The ideal timing of hCG trigger appears to be when the leading follicle is 10-12 mm. Sparse data exists regarding luteal support protocols.

CONCLUSIONS

There is still a need for well-designed studies to establish ideal methods for oocyte priming, timing of retrieval, endometrial preparation and luteal support. Further studies must incorporate both clinical and basic science principles of ovarian, follicular and endometrial physiology.

Xenotransplantation of cryopreserved human ovarian tissue into murine back muscle

BACKGROUND

Ovarian tissue (OT) cryopreservation and transplantation are options for fertility preservation in young female cancer patients.

METHODS

We investigated xenotransplantation of human OT into back muscle (B) of severe combined immunodeficiency mice. OT follicle content was evaluated by stereomicroscopy and pre-transplantation. Xenograft survival, follicular development (with/without FSH administration), apoptosis and vascularization were compared in B- versus K-site (under the kidney capsule) several times after grafting using histology, immunohistochemistry and magnetic resonance imaging. In vitro maturation (IVM) was also performed.

RESULTS

Anastomoses which developed from existing human and invading murine vessels were seen in OT at both sites, but angiogenesis was more prominent at the B- than K-site (P < 0.001). Vascularization and follicle size were correlated in the B-group (Spearman's coefficient 0.73; P < 0.001). FSH increased early (8 days) micro-vessel formation in B but not in K grafts (P < 0.0001, versus no FSH). B-site grafts showed a better histological morphology and survival (P = 0.0084), formation of larger antral follicles (P = 0.005), more metaphase-II (MII) oocytes, growing follicles (P = 0.028) and slightly fewer apoptotic follicles than K grafts. One MI oocyte from B underwent IVM and reached MII stage next day.

CONCLUSIONS

To our knowledge, this is the first report of MII and IVM-MII oocytes obtained from B xenografts. We report the largest oval-shaped antral follicles containing an MII oocyte obtained after OT xenotransplantation to date. Xenografting in the mouse B should be further explored as a method for human OT transplantation.

Healthy live birth from vitrified blastocysts produced from natural cycle IVF/IVM

Natural-cycle IVF combined with in-vitro maturation (natural-cycle IVF/IVM) was used as a treatment for a 27-year-old woman. She was administered 10,000 IU of human chorionic gonadotrophin intramuscularly about 36 h prior to oocyte collection and oocyte collection was performed on day 11 of her menstrual cycle. One mature oocyte was retrieved from the leading follicle and another five mature oocytes and six immature oocytes were retrieved from the rest of the follicles. Out of 10 fertilized zygotes, eight of them cleaved. Three day-3 embryos derived from in-vivo matured oocytes (one was from the leading follicle) were transferred but failed to conceive. The remaining five embryos were continuously cultured until day 6 and four of them developed to the expanded blastocyst stage and vitrified for the storage. Six months later, two vitrified-warmed blastocysts derived from the immature oocytes were transferred and resulted in the full-term delivery of a healthy female infant. This case report for the first time indicates that blastocysts produced from the immature oocytes retrieved from the small follicles, when a leading follicle exists in the ovaries, can be vitrified to produce a healthy live birth, suggesting that natural-cycle IVF/IVM is an efficient infertility treatment.

Exposure to human chorionic gonadotropin during in vitro maturation does not improve the maturation rate and developmental potential of immature oocytes from patients with polycystic ovary syndrome

OBJECTIVE

To investigate the effects of human chorionic gonadotropin (hCG) in culture medium on the in vitro maturation (IVM) and subsequent developmental potential of human immature oocytes.

DESIGN

Prospective, randomized study.

SETTING

Reproductive Medicine Center, First Affiliated Hospital of Wenzhou Medical College, People's Republic of China.

PATIENT(S)

62 women with polycystic ovary syndrome (PCOS) undergoing IVM treatment.

INTERVENTION(S)

Immature oocytes were retrieved from unstimulated ovaries of women with PCOS. We tried three different culture systems in this experiment. In group A, oocytes were cultured in the medium containing M199 + 20% fetal bovine serum (FBS) + 75 mIU/mL recombinant follicle-stimulating hormone (FSH) + 0.5 IU/mL recombinant hCG. In group B, oocytes were cultured in hCG-free IVM medium (M199 + 20% FBS + 75 mIU/mL recombinant FSH) for 10 hours, then transferred to the same medium as used for group A. In group C, oocytes were cultured only in hCG-free IVM medium. After the oocytes had matured in vitro, fertilization and embryo transfer were performed.

MAIN OUTCOME MEASURE(S)

Rates of maturation, fertilization, cleavage, implantation, clinical pregnancy, miscarriage, and live birth.

RESULT(S)

For groups A, B, and C, the maturation rates at 32 and 48 hours were 46.02% and 69.25%; 43.72% and 64.51%; and 51.87% and 67.51%, respectively. Relatively satisfactory clinical results and implantation rates were obtained in all three groups. No statistically significant differences among groups A, B, and C were found in the rates of maturation, fertilization, cleavage, implantation, clinical pregnancy, miscarriage, or live birth.

CONCLUSION(S)

The results of our study indicated that the addition of hCG to in vitro culture medium did not improve the maturation rate or development potential of immature oocytes. For the IVM and development of immature oocytes from women with PCOS, hCG appears to be unnecessary.

Influence of well defined protein source on in vitro maturation of human oocyte: human follicular fluid versus human serum albumin

OBJECTIVE

To compare developmental competency of immature human oocytes matured in vitro in G2 media supplemented by two different protein sources.

DESIGN

Retrospective comparative study.

SETTING

University Hospital IVF program.

PATIENT(S)

Sixty-five consecutive women from whom at least one immature oocyte was obtained during 76 cycles of ovarian hyperstimulation and IVF.

INTERVENTION(S)

G2 media containing human follicular fluid (hFF) (from January to August 2005) or human serum albumin (HSA) (from Sep 2005 to Aug 2006) were used for in vitro maturation of immature oocytes.

MAIN OUTCOME MEASURE(S)

In vitro maturation rate of immature oocytes and their fertilization rate.

RESULT(S)

A total of 231 immature oocytes including 107 germinal vesicle (GV) stage and 124 metaphase I (MI) were cultured in vitro and then fertilized by intracytoplasmic sperm injection. The in vitro maturation rate of GV (40.6% vs. 52.0%) and MI oocytes (84.4% vs. 70.0%) and the fertilization rate in GV (76.9% vs. 48.7%) and MI oocytes (70.4% vs. 73.4%) were not different between hFF- and HSA-supplemented G2 media. The cleavage rates of embryos generated from either GV or MI were similar between the two groups, but they were seldom used in embryo transfer.

CONCLUSION(S)

Developmental competency of immature oocytes was comparable when matured in vitro with G2 media supplemented by either hFF or HSA. Our results suggest that hFF as a protein supplement for human in vitro maturation can be replaced by highly defined HSA.

Clinical-pregnancy outcome after vitrification of blastocysts produced from in vitro maturation cycles

This study was conducted to report the clinical-pregnancy outcome after vitrification of the blastocysts produced from in vitro maturation cycles. The survival rate after thawing was 92.0% (92/100). The clinical-pregnancy and implantation rates were 43.8% and 23.6%, respectively. These results suggest that the blastocyst-stage embryos produced from in vitro maturation cycles can be safely cryopreserved through vitrification.

In-vitro maturation of eggs: is it really useful?

In in-vitro maturation (IVM), immature oocytes are collected from small antral follicles and allowed to mature in the laboratory before routine in-vitro fertilization or micro-injection. The authors' experience in IVM is based on the treatment of two main groups of patients: women with polycystic ovaries and women with normal ovaries. Patients with polycystic ovarian syndrome have irregular, mostly anovulatory cycles and are at increased risk for ovarian hyperstimulation syndrome because of their higher sensitivity to gonadotropins. Women with normal ovarian function may wish to avoid the side-effects of hormone injections, and therefore IVM has also been offered to couples with tubal, male factor and unexplained infertility. In all these groups of patients, immature oocytes have successfully been matured, fertilized and embryos transferred. Pregnancy rates have been reported to be between 4% and 54%. More than 300 children have been born and follow-up studies have reported no major concerns about the pregnancies, deliveries or health of the babies. There are still many questions concerning IVM. As the factors regulating follicle selection are poorly understood, no specific markers for the optimal time of immature oocyte collection have been defined. Furthermore, basic knowledge on the complex intracellular processes involved in the cytoplasmic maturation of human oocyte is lacking, making the design of optimal culture conditions for maturation difficult. The possible long-term effects of IVM on the health and development of children needs future study.

Controlled natural cycle IVF: a novel approach for a dominant follicle during an in-vitro maturation cycle

The objective of this retrospective analysis is to evaluate whether patients developing a dominant follicle in an in-vitro maturation (IVM) programme can be included in a natural cycle IVF (nIVF) programme. In a university teaching hospital, a total of 38 patients with polycystic ovarian syndrome were treated by metformin before undergoing an IVM cycle. Controlled nIVF was performed on seven patients with a dominant follicle. This paper reports three ongoing pregnancies from five embryo transfers in the latter group. Hence, nIVF can be a novel approach for women developing a dominant follicle during an IVM cycle.

In vitro maturation of human oocytes for assisted reproduction

OBJECTIVE

To describe and evaluate the current practice of in vitro maturation of oocytes for assisted reproduction.

DESIGN

Review of the available and relevant literature regarding in vitro maturation of oocytes.

CONCLUSION(S)

In vitro maturation of human oocytes retrieved from antral ovarian follicles is an emerging procedure quickly being incorporated into the realm of assisted reproductive technologies. This new technology has several potential advantages over traditional controlled ovarian hyperstimulation for IVF, such as reduction of costs by minimizing gonadotropin and GnRH analogue use, elimination of ovarian hyperstimulation syndrome, and simplicity of protocol. In vitro maturation of oocytes for assisted reproduction in human beings still is undergoing refinement but currently is providing efficacy and safety outcome comparable to that of traditional IVF in recent selected studies. Implementing in vitro maturation into an established IVF practice is feasible and requires only a few simple adjustments. Crucial to the advancement and optimization of the technology is a better understanding of how to maximize immature oocyte developmental competence and endometrial receptivity.

Pronuclear synchronization and nuclear morphology of mature and in vitro matured oocytes in the rat: an ultrastructural study

The objective of this study was to evaluate synchronous and asynchronous pronucleus (PN) formation and the related patterns of juxtapositional nucleolus (n) formation in immature (prophase I [PI] and metaphase I [MI]) and mature (metaphase II [MII]) oocytes after fertilization, both ultrastructurally and at the level of light microscope. A single dose of 15 IU gonadotrophin was injected subcutaneously to twenty four 26-wk-old, female Wistar rats to induce ovulation. Human chorionic gonadotrophin (4 IU) was administered 40 h later, and after 4-6 h the ovaries were dissected, and the oocytes were aspirated. A total of 214 rat oocytes were classified according to a maturation index as follows: group I, 80 PI oocytes; group II, 50 MI oocytes; and group III, 84 MII oocytes. Immature oocytes were in vitro matured for 18-36 h. Spermatozoa were acquired by microepididymal sperm aspiration and processed using swim-up technique. Intracytoplasmic sperm injection was performed on mature oocytes after 2 h of incubation and on in vitro matured (IVM) oocytes 4 h after maturation. Pronuclear synchronization [both pronucleases (PNs) centrally located, equal sized, with equal numbers and sizes of juxtapositional nucleoli (Nn)] was observed in fertilized oocytes. Asynchronous PN formation (diversity between male and female PNs, related to dimensions, localization, and the number of Nn) in groups I, II, and III was found in 75, 86, and 47% of preembryos, respectively. There was a significant difference of synchronous pronuclear formation between mature and IVM oocytes (P < 0.05). In IVM oocytes, asynchronous PN formation is high, and juxtapositional pronucleolar patterns are observed to be low by transmission electron microscope (TEM).

Strategies in human in-vitro maturation and their clinical outcome

The basis of in-vitro maturation (IVM) is the maturing in vitro of oocytes from the germinal vesicle (GV) stage of development to the metaphase II stage. Experience in handling immature oocytes has been obtained from two main groups. The first group is women suffering from polycystic ovarian syndrome, who are extremely sensitive to stimulation with exogenous gonadotrophins in assisted reproduction, and have a significant risk of developing ovarian hyperstimulation syndrome (OHSS). The second group is regular cycling women with normal ovaries referred for IVF due to severe male infertility. In both groups, aspiration of immature oocytes has been performed in unstimulated cycles and after priming with human chorionic gonadotrophin or FSH respectively. Clinical pregnancy rates of 24% per aspiration have been obtained. Children born after IVM appear to be healthy. These data, taken together, suggest that in future, immature oocyte retrieval combined with IVM could replace conventional IVF in selected patients.

Immature oocyte in-vitro maturation: clinical aspects

The development of immature oocyte collection techniques for in-vitro maturation (IVM), combined with novel culture techniques, opens new possibilities for assisted reproductive technology. Optimization of clinical management of IVM cycles will enhance pregnancy outcome, so that IVM might become an effective alternative assisted reproduction treatment for infertile patients irrespective of the cause of infertility. Parameters such as age and baseline antral follicular count are predictive of outcome and should be used as selection criteria for IVM treatment. Women with polycystic ovary disease and normo-ovulatory patients at risk of developing ovarian hyperstimulation syndrome might benefit from earlier retrieval of oocytes followed by IVM and embryo transfer. HCG priming before oocyte retrieval seems beneficial in terms of oocyte yield and maturational competence, and may increase the harvest of mature oocytes and lead to better endometrial synchronization with the developing embryo. The timing of aspiration may be crucial in IVM and selection criteria for follicle size at aspiration need defining prospectively for infertility type. Finer calibre aspiration needles and low aspiration pressure yield more oocytes. A combination of natural cycle IVF with IVM is a promising, mild and inexpensive assisted reproduction treatment, widely accessible the infertile population.

In-vitro maturation of germinal-vesicle oocytes and cryopreservation in metaphase I/II: a possible additional option to preserve fertility during ovarian tissue cryopreservation

This study describes the possibility of combining two options in order to preserve female fertility: cryopreservation of human ovarian tissue and in-vitro matured germinal vesicle (GV) oocytes retrieved during tissue dissection. In contrast to ovarian tissue cryopreservation, the cryostorage of in-vitro matured unfertilized metaphaseI/II oocytes could be a more realistic option. This concept of preserving fertility before chemotherapy and/or radiotherapy without a long time delay could be an additional reason for favouring ovarian tissue cryopreservation. This concept is discussed in regard to two cases.

Assisted reproduction in the treatment of polycystic ovarian syndrome

Treatment of patients with polycystic ovary syndrome (PCOS) with assisted reproductive techniques is a great challenge for the infertility specialist. Patients with PCOS demonstrate many problems, such as excessive body weight and hyperinsulinaemia, that render management more complex. Prior to treatment with IVF, the PCOS patient should be thoroughly evaluated for disclosure of endometrial neoplasia, hyperinsulinaemia, and other general health related problems. Ovarian stimulation for IVF carries the risks of overstimulation and severe hyperstimulation, which should be avoidable in most cases with preventive measures. The outcome in terms of pregnancy and implantation rates is similar for patients with PCOS when compared with patients undergoing IVF for other indications. There are some questions regarding oocyte and embryo quality in women with PCOS. This manifests itself in lower fertilization rate and decreased embryo quality in some studies. However, increased numbers of oocytes available for insemination or ICSI compensate for decreased fertilization rates and embryo quality. More recent studies suggest higher cumulative conception rates in women with PCOS when compared with controls. In-vitro maturation (IVM) of oocytes retrieved from non-stimulated or minimally stimulated cycles represents a viable option that should be considered seriously when assisted conception is attempted. Results of IVM, however, should be improved further and generalized before the technique can be advocated as the initial treatment approach in these patients.

Maturation in vitro des ovocytes : bilan et perspectives dans l’espèce humaine

Mature oocytes are rare and highly specialized cells. In vitro maturation of human oocytes is an emerging assisted reproductive technology allowing to produce more mature oocytes without ovarian stimulation. Whereas in vitro maturation is technically more demanding than conventional in vitro fertilization for the laboratory, it carries many potential advantages, for example, in terms of lower treatment heaviness and removal of risk of severe ovarian hyperstimulation syndrome for the patients. Although the technology is still experimental, oocytes in vitro maturation has been successfully used and pregnancies and live births have been reported. Despite these successes, the overall efficiency of in vitro maturation remains low and this procedure must still be improved. The different steps of in vitro maturation process are shown and discussed as well as results in terms of pregnancy and live birth rates.

In-vitro maturation of oocytes from unstimulated polycystic ovaries

In-vitro fertilization (IVF), an established treatment for infertility, may result in pregnancy and live-birth rates higher than following natural conception in fertile couples. However, IVF is associated with two major complications, namely, multiple pregnancy and ovarian hyperstimulation syndrome. The latter is a consequence of the ovarian stimulation required for IVF. Women with polycystic ovaries (PCO) are at increased risk of developing this complication. Ovarian stimulation is not required for in-vitro maturation (IVM) of immature oocytes. This approach is therefore both cheaper and safer than IVF, particularly for women with PCO. It has been found that the IVM pregnancy rate is correlated with the number of antral follicles present, the peak ovarian stromal blood flow velocity at the baseline ultrasound scan, the number of immature oocytes collected, absence of a dominant follicle at the time of immature oocyte retrieval, and endometrial thickness at embryo transfer. The indications for IVM at present would include women requiring IVF who have PCO, those with primarily poor quality embryos in repeated previous IVF cycles for no apparent reason, poor responders to high dose gonadotrophin stimulation for IVF, and finally, women with PCO who are considering egg donation.

Maternal serum supplementation in culture medium benefits maturation of immature human oocytes

This study compared the rates of maturation, fertilization, cleavage and pregnancy among oocytes matured in medium containing either human serum albumin (HSA) or maternal serum. Immature oocytes were obtained from 51 consecutive regularly cycling women <38 years of age. Immature oocytes were aspirated transvaginally on cycle day 8-9 after priming with FSH (Gonal-F 150 IU/day for 3 days, initiated on day 3). Oocytes were matured in Dyrkningsmedie til IVM supplemented with recombinant FSH (rFSH) 0.075 IU/ml and HCG 0.5 IU/ml for 28-30 h. In group I (n = 63 oocytes obtained from the first 23 cycles) the culture medium was supplemented with 2% (w/v) HSA. In group II (n = 74 oocytes obtained from the following 28 cycles) the medium was supplemented with 10% (v/v) heat-inactivated maternal serum. Intracytoplasmic sperm injection (ICSI) was performed on all methaphase II oocytes. Significantly increased rates of maturation 47/74 (63%) vs. 26/63 (41%) (P < 0.05), pregnancy 6/28 (21%) vs. 0/23 (0%) (P < 0.05) and implantation 6/20 (30%) vs. 0/15 (0%) (P < 0.05) were obtained from oocytes matured in culture medium with maternal serum supplementation compared with oocytes matured in medium supplemented with HSA. These results indicate that factors other than albumin in maternal serum play an important role in maturation and subsequent developmental capacity of human oocytes.

Influence of the dominant follicle on in-vitro maturation of human oocytes: a prospective non-randomized study

The present study was designed to examine the influence of timing of aspiration and the influence of a dominant follicle on maturation and fertility potential of immature oocytes aspirated in unstimulated cycles. The study included 81 regularly cycling women. In group I (n = 53), oocyte retrieval was scheduled the day after a follicle of 10 mm and an endometrium of at least 5 mm were observed. In group II (n = 28), aspiration was scheduled the day after observation of the same ultrasound criteria plus a detected increase (100%) in the level of oestradiol compared with the level on day 3. The maturation rate was significantly higher in group I compared with group II (107/184, 58.2% versus 56/124, 45.2%, P < 0.05), whereas the rates of fertilization and cleavage did not differ between the two groups. The clinical pregnancy rate per aspiration was significantly higher in group I compared with group II (9/53, 17% versus 0/28, 0%, P < 0.05). When comparing oocytes originating from the ovary with the dominant follicle (ipsilateral ovary) with oocytes originating from the ovary without a dominant follicle (contralateral ovary) an increased fertilization rate was observed in group I, and an increased maturation rate was observed in group II. When the data from the two groups were pooled, an increased maturation rate was observed in oocytes originating from the ipsilateral ovary compared with oocytes originating from the contralateral ovary. No difference was found with respect to rates of fertilization and cleavage rates when all oocytes originating from the ipsilateral ovary were compared with all oocytes originating from the contralateral ovary.

Ongoing twin pregnancy after vitrification of blastocysts produced by in-vitro matured oocytes retrieved from a woman with polycystic ovary syndrome: Case report

This case report describes an ongoing pregnancy after cryopreservation of blastocysts produced by in-vitro matured oocytes retrieved from a woman with polycystic ovary syndrome (PCOS). Oocyte retrieval was performed on day 18. The patient was administered 10 000 IU of hCG s.c. 36 h prior to oocyte collection. A total of 61 immature oocytes was obtained. Following incubation for 24-72 h in the YS maturation medium supplemented with 30% follicular fluid (hFF), 1 IU/ml FSH, 10 IU/ml hCG and 10 ng/ml rhEGF, 65.6% (40/61) of the oocytes were at the metaphase II stage. Thirty-eight oocytes (38/40, 95.0%) were fertilized after ICSI with the patient's husband's sperm and the 2PN oocytes were co-cultured with cumulus cells in YS medium supplemented with 10% hFF. Four embryos were transferred into the uterus on day 4 following oocyte retrieval but this failed to result in pregnancy. Eight embryos were developed to expanded blastocyst stage. The blastocysts were vitrified on electron microscope grids. Two years after cryopreservation, four blastocysts were thawed, three re-expanded and these frozen-thawed blastocysts were transferred to the uterus. A viable twin pregnancy was confirmed by ultrasound scan.

Oocyte maturation in vitro

In contrast to conventional assisted reproduction techniques in which metaphase II oocytes are retrieved for fertilization in vitro, during the in-vitro maturation of oocytes, immature germinal vesicle stage oocytes are retrieved and matured in the laboratory before fertilization and embryo transfer. Whereas in-vitro maturation is technically more demanding than in-vitro fertilization it carries many potential advantages in terms of lower treatment costs and greater safety, as a result of reducing both the number of clinical consultations and the amount of pharmacological intervention. Although the technology is still experimental, in-vitro maturation has been successfully used for the treatment of patients with polycystic ovarian syndrome, and a number of pregnancies and live births have been reported. Despite these successes and much continuing research effort, the overall efficiency of in-vitro maturation remains low, and neither clinical nor laboratory procedures can be considered to be as robust and routinely feasible as conventional in-vitro fertilization techniques. The immediate goals for in-vitro maturation programmes are therefore to increase germinal vesicle oocyte recovery rates, optimize culture conditions, improve oocyte maturation potential, and after fertilization to produce pregnancy rates that are at least equivalent to those obtained using conventional in-vitro fertilization. This review focuses on the physiology and application of human oocyte maturation in vitro, and will detail the recent advances reported in this rapidly advancing field.

In vitro maturation and fertilization of oocytes from unstimulated ovaries: predicting the number of immature oocytes retrieved by early follicular phase ultrasonography

OBJECTIVE

To select women who will benefit most from in vitro maturation (IVM) of oocytes treatment, this study was undertaken to examine the ability of a transvaginal ultrasonography to predict the number of immature oocytes collected from unstimulated ovaries.

STUDY DESIGN

The relationship between the number of immature oocytes retrieved and the pregnancy rate was assessed in 189 IVM treatment cycles. In 96 consecutive cycles, an early follicular phase transvaginal ultrasonographic measurement of the antral follicle count (AFC), ovarian volume, and peak ovarian stromal blood flow velocity (Vmax) was performed, and the results were correlated with the number of immature oocytes.

RESULTS

The clinical pregnancy rate increased significantly with the number of oocytes retrieved (P =.02) and was 26.8% (15/56) in those with >10 immature oocytes. The AFC, ovarian volume, and ovarian stromal Vmax were all predictive of the number of oocytes retrieved, but when the other factors were controlled by multiple regression analysis the AFC was the only significant predictor (P <.001).

CONCLUSIONS

Pregnancy rates after IVM correlate with the number of immature oocytes retrieved. This is best predicted by an ultrasonographic assessment of the AFC.