Perspectives on the development and future of oocyte IVM in clinical practice.

Oocyte in vitro maturation (IVM) is an assisted reproductive technology designed to obtain mature oocytes following culture of immature cumulus-oocyte complexes collected from antral follicles. Although IVM has been practiced for decades and is no longer considered experimental, the uptake of IVM in clinical practice is currently limited. The purpose of this review is to ensure reproductive medicine professionals understand the appropriate use of IVM drawn from the best available evidence supporting its clinical potential and safety in selected patient groups. This group of scientists and fertility specialists, with expertise in IVM in the ART laboratory and/or clinic, explore here the development of IVM towards acquisition of a non-experimental status and, in addition, critically appraise the current and future role of IVM in human ART.

FERTILITY PRESERVATION: Progress and prospects for developing human immature oocytes in vitro.

Ovarian cryopreservation rapidly developed from basic science to clinical application and can now be used to preserve the fertility of girls and young women at high risk of sterility. Primordial follicles can be cryopreserved in ovarian cortex for long-term storage and subsequently autografted back at an orthotopic or heterotopic site to restore fertility. However, autografting carries a risk of re-introducing cancer cells in patients with blood-born leukaemias or cancers with a high risk of ovarian metastasis. For these women fertility restoration could only be safely achieved in the laboratory by the complete in vitro growth (IVG) and maturation (IVM) of cryopreserved primordial follicles to fertile metaphase II (MII) oocytes. Culture systems to support the development of human oocytes have provided greater insight into the process of human oocyte development as well as having potential applications within the field of fertility preservation. The technology required to culture human follicles is extremely challenging, but significant advances have been made using animal models and translation to human. This review will detail the progress that has been made in developing human in vitro growth systems and consider the steps required to progress this technology towards clinical application.

Prospects for new oocyte-based assisted reproduction in animals and humans.

Procuring high-quality oocytes is the rate-limiting step for assisted reproduction technologies intended for embryo production. Although much is known about the intraovarian processes that dictate oocyte growth and maturation, subtleties in the process of oogenesis have yet to be replicated in invitro systems. In contrast with the mouse, in which functional oocytes have been derived from stem cells under ex vivo conditions, the generation of developmentally competent oocytes in other species has yet to be achieved. This paper reviews the principles and practices based on stem cell and organ culture strategies that hold promise for developing a technological base upon which future efforts to recapitulate or augment oogenesis in mammals could be realised.

Future developments: In vitro growth (IVG) of human ovarian follicles.

Removal and storage of ovarian cortical tissue is currently offered to young female cancer patients undergoing potentially sterilizing chemotherapy and/or radiotherapy. For patients at high risk of reintroduction of malignancy through auto-transplantation, the ultimate aim is to achieve complete oocyte development from this tissue in vitro. The ability to develop human oocytes from the earliest follicular stages through to maturation and fertilization in vitro would revolutionize fertility preservation practice. This has been achieved in mice where in vitro grown oocytes from primordial follicles have resulted in the production of live offspring. Systems that support growth and development of oocytes from human ovarian cortex are being developed by several groups. This review focuses on the steps required to recapitulate in vitro the process of human oocyte development from the primordial stage and the systems currently available to support this.

Assisted reproduction with gametes and embryos: what research is needed and fundable?

Principles for selecting future research projects include interests of investigators, fundability, potential applications, ethical considerations, being able to formulate testable hypotheses and choosing the best models, including selection of the most appropriate species. The following 10 areas of assisted reproduction seem especially appropriate for further research: efficacious capacitation of bovine spermatozoa in vitro; improved in vitro bovine oocyte maturation; decreasing variability and increasing efficacy of bovine superovulation; improved fertility of sexed semen; improving equine IVF; improving cryopreservation of rooster spermatozoa; understanding differences between males in success of sperm cryopreservation and reasons for success in competitive fertilisation; mechanisms of reprogramming somatic cell nuclei after nuclear transfer; regulation of differentiation of ovarian primordial follicles; and means by which spermatozoa maintain fertility during storage in the epididymis. Issues are species specific for several of these topics, in most cases because the biology is species specific.

Follicular fluid and supernatant from cultured cumulus-granulosa cells improve in vitro maturation in patients with polycystic ovarian syndrome.

OBJECTIVE: To study the effectiveness of a new in vitro maturation (IVM) approach based on heterologous follicular fluid (HFF) and supernatant of cumulus-granulosa cells (CGCs) mimicking the intact follicular microenvironment to rescue immature denuded oocytes (IDOs) of patients with polycystic ovary syndrome (PCOS) whose IVM or IVF outcomes remain poor. DESIGN: Randomized controlled trial. SETTING: University-affiliated private center. PATIENT(S): One hundred fifty-nine IDOs were obtained from 47 patients with PCOS. First, a simple IVM system (S-IVM; 40 IDOs; control group) was compared with different protocols based on the addition of autologous follicular fluid (AFF-IVM; 44 IDOs), HFF (HFF-IVM; 42 IDO), or HFF with CGC isolated from seven women without PCOS and presenting 100% in vivo oocyte maturation (HFF/CGC-IVM; 33 IDOs). INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): IVM outcomes were compared among the four groups (S-IVM, AFF-IVM, HFF-IVM, HFF/CGC-IVM); then the vitro and in vivo maturation results (from controlled ovarian stimulation of PCOS patients) were compared for each group. RESULT(S): The HFF/CGC-IVM method gave the best yield of developed blastocysts per IDO compared with S-IVM, AFF-IVM, and HFF-IVM (27% vs. 2%, 2%, and 12%, respectively). The IVM rate with the HFF/CGC-IVM method was even higher than that compared with the in vivo maturation rate (79% vs. 42%), with significant improvement in the cleavage rate (71% vs. 61%). CONCLUSION(S): This adapted IVM system could be used to reach an acceptable result in meiotic competence and competent metaphase II oocytes capable of developing into intact embryos after fertilization and before transfer.

Development of in vitro maturation techniques for clinical applications.

In vitro maturation (IVM) refers to maturation in culture of immature oocytes at different stages that may or may not have been exposed to short courses of gonadotropins. The source of immature oocytes is an important feature for subsequent embryonic development, pregnancy, and healthy live births. IVM is an effective treatment that has already achieved significant outcomes of acceptable pregnancy and implantation rates and has led to the births of several thousand healthy babies. As the development of IVM treatment continues, an attractive possibility for improving the already successful outcome is to combine a natural-cycle in vitro fertilization (IVF) treatment with immature-oocyte retrieval followed by IVM of those immature oocytes. If the treatment processes can be simplified for immature-oocyte retrieval, different types of infertile women may be able to take advantage of these treatments. Mild-stimulation IVF combined with IVM treatment may represent a viable alternative to the standard treatment. Although IVM treatment is still considered to be experimental, it is now time to reconsider the IVM technology and its development. Mild-stimulation IVF combined with IVM may prove to be not just alternatives to standard treatments, but potentially first-line treatment choices.

In vitro maturation remains an interesting procedure.

The number of live births from IVM oocytes has been increasing over the past two decades. Data concerning the health of IVM infants are reported by the authors of this Views and Reviews.

Human oocyte maturation in vitro.

Oocytes from medium-sized antral follicles have already completed their growth phase and, if released from the follicular environment and cultured in vitro, are able to resume the meiotic process and mature. However, in vitro maturation (IVM) does not entirely support all the nuclear and cytoplasmic changes that occur physiologically as an effect of the ovulatory stimulus. Regardless, oocyte IVM is widely applied for the breeding of agriculturally important species. In assisted reproduction technology, IVM has been proposed as an alternative treatment to circumvent the drawbacks of standard ovarian stimulation regimens. Initially introduced to eliminate the risks of ovarian hyperstimulation syndrome afflicting women presenting with polycystic ovaries, subsequently IVM has been suggested to represent an additional approach suitable also for normovulatory patients. So far, in children born from IVM cycles, no doubts of an increased incidence of congenital abnormalities have been raised. Many more births would be achieved if novel IVM systems, currently dominated by empiricism, could be conceived according to more physiological criteria. Recent findings shedding new light on the control of meiotic progression, the support of cumulus cells to the oocyte cellular reorganization occurring during maturation, and the modulation of the stimulus that promotes oocyte maturation downstream the mid-cycle gonadotropin signal are likely to provide crucial hints for the development of more efficient IVM systems.

Retrieving oocytes from small non-stimulated follicles in polycystic ovary syndrome (PCOS): in vitro maturation (IVM) is not indicated in the new GnRH antagonist era.

It has been two decades since pregnancies have been obtained through in vitro maturation (IVM) of germinal vesicle-stage oocytes retrieved from non-stimulated ovaries. This technique first offered in PCOS cannot be recommended today in this indication because the results do not match those of regular ART, and new GnRH antagonist and agonist-trigger protocols reliably prevent OHSS.