State of the art in in-vitro oocyte maturation

In-vitro maturation of oocytes: biological aspects

Natural cycle and in-vitro maturation (IVM) of oocytes are becoming interesting alternatives to classical assisted reproduction technology approaches for patients, especially in those at high risk for ovarian hyperstimulation syndrome or with poor ovarian reserve. More than for their clinical and biological indications, natural cycle and IVM of oocytes can also be considered as good social and economic alternatives to the classical IVF treatment, based on their financial cost-effectiveness with exclusion of expensive medications. To be successful, IVM must entail both nuclear and cytoplasmic maturation, and its maturation and success rates are affected by the number of collected cumulus layers, the degree of atresia and the maturation rate between 24 and 48 h. Endogenous regulation of oocyte maturation is a complex sequence of events regulated by endocrine parameters, oocyte/follicular cross-talk, and intra-oocyte kinase/phosphatase interactions. This complex process requires a better definition of each contributing factor affecting oocyte development and the resulting embryo quality. The clinical aspects of IVM have been documented earlier; the present paper will mainly focus on the biological aspect of oocyte maturation in vitro and the quality of derived embryos.

Oocyte Maturation in Assisted Reproductive Techniques

Human oocyte maturation is a long process during which nuclear maturation occurs resulting in germinal vesicle breakdown (transition from prophase I to metaphase II) and extrusion of the first polar body. During oocyte maturation, in parallel with nuclear maturation, a number of events take place in the oocyte cytoplasm that assist fertilization and early embryonic development. So far several attempts have been made to mature human oocytes in vitro. The main patient group to which in vitro maturation (IVM) has been applied is polycystic ovarian syndrome. In a concise review we present the techniques used for the IVM of oocytes and the role of hormones and growth factors in IVM and subsequent fertilization and early embryonic development.

Effects of in vitro maturation of monkey oocytes on their developmental capacity

The study of in vitro maturation (IVM) of rhesus monkey oocytes has important implications for biomedical research and human infertility treatment. In vitro-matured rhesus monkey oocytes show much less developmental potential than IVM oocytes of other species. Since about 1980 when rhesus monkey IVM, in vitro fertilization (IVF) and in vitro embryo culture (IVC) systems were established, numerous efforts have been made to improve the developmental competence of oocytes and to understand the mechanisms regulating oocyte maturation. This review describes recent progress in this area, particularly the effects of factors such as steroid hormones, energy substrates, amino acids, ovarian follicle status, maternal age and breeding season on the developmental competence, gene expression patterns and genome integrity of rhesus IVM oocytes.

In vitro maturation of human oocytes in a follicle-mimicking three-dimensional coculture

OBJECTIVE

To verify the hypothesis that a three-dimensional, follicle-mimicking structure enhances in vitro maturation yields without hormonal supplementation in an in vitro maturation program.

DESIGN

Feasibility study; 204 anonymous denuded germinal vesicles retrieved from gonadotropin-treated women were cultured for 48 hours without hormonal supplementation in microdrop culture or in a three-dimensional coculture with granulosa cells in a barium alginate membrane.

SETTING

An assisted reproduction center in Italy.

PATIENT(S)

One hundred twenty-two informed women.

INTERVENTION(S)

Germinal vesicles retrieved after ovarian stimulation were denuded and cultured without hormonal supplementation in microdrop culture or in a three-dimensional coculture with granulosa cells enclosed in the core of a barium alginate capsule.

MAIN OUTCOME MEASURE(S)

Oocyte maturation and morphological investigation of follicle-mimicking structures.

RESULT(S)

Statistically significantly higher oocyte maturation yields were obtained by using the three-dimensional coculture system enclosed in a barium alginate membrane (after 48 hours: coculture, 90.3%; microdrop, 52.0%; odds ratio, 8.51). Morphological investigation indicated that after 48 hours of coculture, the decumulated oocyte appeared to be surrounded by a pseudocumulus structure that lies on the inner surface of the alginate membrane and protrudes toward the capsule's lumen.

CONCLUSION(S)

The maturation yield of cocultured oocytes is eightfold higher than that achieved with a microdrop maturation technique, making a higher number of gametes available for IVF programs. Stereomicroscopic morphological survey indicates a reassembly of granulosa cells surrounding oocyte zona, mimicking an antral cumulus oophorus.

Effect of gonadotrophin stimulation on mouse oocyte quality and subsequent embryonic development in vitro

In-vivo-matured oocytes were collected from naturally ovulated and superovulated [pregnant mare's serum gonadotrophin (PMSG) + human chorionic gonadotrophin (HCG)] mice. Immature oocytes were retrieved from naturally cycling mice and from mice primed with PMSG. The percentages of cleavage and blastocyst formation were significantly different (P < 0.05) between in-vivo- and in-vitro-matured oocytes. Blastocyst formation rate was significantly higher (P < 0.05) in immature oocytes derived from PMSG-primed mice, and the percentages of oocytes with comet tails, and their length, were significantly higher and longer respectively in in-vitro-matured oocytes. Total cell numbers of blastocysts were also significantly different (P < 0.05) between in-vivo- and in-vitro-matured oocytes, but there were also no differences in ratio of trophectoderm (TE)/inner cell mass (ICM). In conclusion, in-vivo-matured mouse oocytes were more competent than those matured in-vitro, perhaps due to a lesser degree of DNA damage. Embryonic development capacity of in-vivo-matured oocytes is not promoted by ovarian stimulation. Gonadotrophin priming prior to immature mouse oocyte retrieval is beneficial to subsequent embryonic development.

The in vitro maturation (IVM) of human oocytes for in vitro fertilization (IVF): is it time yet to switch to IVM-IVF?

The recent study by Li et al. observed that human oocytes from patients with polycystic ovary syndrome (PCOS) matured in vitro exhibited a higher proportion of abnormal spindle structures and disturbed chromosomal configurations compared with in vivo-matured oocytes from a control group of PCOS patients. This article discusses the obstacles that must be overcome and factors that must be monitored when attempting to optimize conditions for the in vitro maturation of human oocytes, with particular attention to the strengths and weaknesses of the study by Li et al.

Transient transfection of porcine granulosa cells after 3D culture in barium alginate capsules

Three-dimensional culture systems in barium alginate capsules can be employed to maintain primary granulosa cells in an undifferentiated state for almost 6 days. This is due to a self-organization of cells in a pseudofollicular structure. The transfection of primary granulosa cells is a necessary condition when employing these culture systems for several purposes, for example as an in vitro toxicity test or the development of oocytes or zygotes. In this work, the feasibility of two transient transfection techniques (liposome-mediated and electroporation) was assessed in primary porcine granulosa cells after a 6-day culture in an artificial extracellular matrix (barium alginate membrane). Human recombinant green fluorescent protein was chosen as a molecular readout, and protein expression was assessed after 48 hours from transfection. Liposome-mediated transfection gave low transfection levels, with increasing yields from 2 to 12 microgDNA/ml of medium; the maximum percentage (85.7%) was reached at 12 microgDNA/ml of medium. Electroporation-mediated transfection yields were higher: the best results (81.7% of transfected cells) were achieved with two 50V pulses and 12 microg/ml DNA. The application of a single or double pulse (50V) at 4 mgDNA/ml gave negligible results. These results indicate that primary granulosa cell cultured in barium alginate capsules can be transfected by electroporation with high transfection yields.

In vitro oocyte maturation and subsequent delayed fertilization is associated with increased embryo aneuploidy

Failed fertilization and the appearance of immature oocytes are common in IVF practice; rescue intracytoplasmic sperm injection can be used as a therapy. However, this study indicates that embryos created after in vitro maturation and delayed intracytoplasmic sperm injection contain an increase in aneuploidy (79.7%) over control embryos (60.5%). Therefore, patients should be informed of the possible risk when presented with delayed intracytoplasmic sperm injection.

Pregnancies and births resulting from in vitro matured oocytes fertilized with testicular spermatozoa

PURPOSE

In vitro maturation (IVM) of immature human oocytes is an attractive option for the treatment of infertility. Similarly, intracytoplasmic sperm injection (ICSI) followed by testicular fine needle aspiration (TEFNA) is an important treatment for primarily male-factor infertility. This report highlights the combination of these two advanced assisted reproduction techniques, namely IVM and fertilization with TEFNA-retrieved spermatozoa by ICSI to overcome both of male and female infertility problems.

METHODS

Before immature oocyte retrieval (IOR), gonadotropin stimulation was given for 3 or 5 days. Following IVM, and mature oocytes were inseminated by ICSI followed by TEFNA.

RESULTS

Four couples with five completed treatment cycles were performed, and total of 36 immature oocytes were retrieved. Following 36 to 48 h of culture, 32 (88.89%, 32/36) oocytes became mature. The mature oocytes were inseminated with TEFNA-retrieved sperm, and 18 (56.25%, 18/32) oocytes were fertilized normally following ICSI. Eleven embryos were transferred in five cycles and two pregnancies and two singleton births were achieved in two patients.

CONCLUSIONS

This result demonstrates that the successful pregnancies and live births can be established from embryos produced from in vitro matured oocytes that fertilized with testicular sperm.

Assisted reproduction: the epigenetic perspective

Developmental pathways in humans and other organisms are buffered against changes in genotype and environment. Therefore, it should not come as a surprise that most of the children conceived by assisted reproduction technology (ART) are healthy, although ART bypasses a lot of biological filters and subjects the gametes and the early embryo to environmental stress. If, however, the buffer breaks down, the development of certain tissues or organs may follow abnormal trajectories. We argue that both normal and abnormal development in children conceived by ART can be explained by epigenetic mechanisms, which control the establishment and maintenance of gene expression patterns in the placenta and fetus. Imprinted genes are of special importance in this respect. There is increasing evidence that genetic factors in infertile couples as well as environmental factors (hormones and culture media) can have adverse effects on epigenetic processes controlling implantation, placentation, organ formation and fetal growth. In addition, loss of epigenetic control may expose hidden genetic variation.

In vitro maturation of human oocytes and cumulus cells using a co-culture three-dimensional collagen gel system

BACKGROUND

Deficiencies remain in the ability of in vitro-matured human oocytes to acquire full developmental competence and give rise to a healthy pregnancy. A clear deficiency of current systems utilizing human oocytes has been the absence of cumulus cells. In the present study, a three-dimensional (3D) co-culture system exploiting an extracellular matrix was developed and compared to conventional methods for its ability to support maturation of human oocytes.

METHODS AND RESULTS

Cumulus cells were embedded into a 3D collagen gel matrix with individual oocytes added to each gel. Oocytes from the same patient cultured in the gel matrix matured to metaphase II at rates similar to those of cumulus-free oocytes cultured in individual microdrops. Following maturation of oocytes and fixation of intact gels, chromatin and cytoskeletal elements were assessed in oocytes and cumulus cells. The activities of the key cell cycle kinases, maturation-promoting factor (MPF) and mitogen-activated protein kinase (MAPK), were compared in oocytes matured under the two culture conditions. Compared with denuded oocytes, co-cultured oocytes exhibited increased MAPK activity, but no difference in MPF levels.

CONCLUSIONS

This work characterizes a novel and efficacious culture system that takes advantage of the unique properties of the extracellular matrix, a 3D microenvironment, and the presence of cumulus cells for maturing human oocytes in vitro.

Fertilization of in vitro matured human oocytes by intracytoplasmic sperm injection (ICSI) using ejaculated and testicular spermatozoa

AIM

To evaluate the fertilization competence of spermatozoa from ejaculates and testicle when the oocytes were matured in vitro following intracytoplasmic sperm injection (ICSI).

METHODS

Fifty-six completed cycles in 46 women with polycystic ovarian syndrome were grouped according to the semen parameters of their male partners. Group 1 was 47 cycles that presented motile and normal morphology spermatozoa in ejaculates and Group 2 was the other nine cycles where male partners were diagnosed as obstructive azoospermia and spermatozoa could only be found in testicular tissue fragment. All female patients received minimal stimulation with gonadotropin. Immature oocytes were matured in vitro and inseminated by ICSI. The spermatozoa from testes were retrieved by testicular fine needle aspiration.

RESULTS

A total of 449 and 78 immature oocytes were collected and cultured for 48 hours, 75.5 % (339/449) and 84.6 % (66/78) oocytes were matured in Groups 1 and 2, respectively. The percentage of oocytes achieving normal fertilization was significantly higher in Group 1 than that in Group 2 (72.9 % vs. 54.5 %, P 0.05). There were no significant differences in the rates of oocytes cleavage and clinical pregnancies in these two groups [87.4 % (216/247) vs. 88.9 % (32/36); 21.3 % (10/47) vs. 44.4 % (4/9)]. A total of 15 babies in the two groups were healthy delivered at term.

CONCLUSION

It appears that IVM combined with ICSI using testicular spermatozoa can produce healthy infants, while the normal fertilization rate of in vitro matured oocytes after ICSI using testicular spermatozoa was significantly lower than using the ejaculated spermatozoa.

Fertility in female cancer survivors: pathophysiology, preservation and the role of ovarian reserve testing

The improved long-term survival of adolescents and young women treated for cancer has resulted in an increased focus on the effects of chemotherapy on ovarian function and its preservation. These women may seek advice and treatment regarding their reproductive status, including ways of preserving their fertility and preventing a premature menopause--factors that can have a profound impact on their quality of life. This article comprehensively reviews ovarian reserve testing (ORT) in general. Special emphasis is placed on patients with cancer, including the pathophysiology of gonadal damage following chemotherapy, fertility preservation and the potential role of ORT. Baseline parameters of ovarian reserve [FSH LH, estradiol, inhibin B and anti-Mullerian hormone (AMH)] have not yet performed sufficiently well in predicting poor outcome in assisted reproduction, but biochemical markers of ovarian reserve appear to be better than chronological age. Inhibin B and AMH show potential for future use. Dynamic testing appears to show much promise, especially stimulated levels of inhibin B and estradiol. The most promising tests of ovarian reserve are the biophysical markers, where total antral follicle count was found to be most discriminatory followed by ovarian volume. Combination of biochemical, biophysical and clinical markers of ovarian reserve may also improve predictive capacity. However, there is a lack of data pertinent to ORT in cancer. As yet there is no single clinically useful test to predict ovarian reserve accurately. Patients with cancer represent a distinct cohort who have particular concerns about their future fertility and the possibility of a premature menopause, they can benefit greatly from knowledge of their functional ovarian reserve. Large, prospective, randomized, adequately controlled studies specific to different geographical areas are required in a control population of comparable reproductive age to determine the potential role of ORT in clinical practice.

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.