Successful delivery after the transfer of embryos obtained from a cohort of incompletely in vivo matured oocytes at retrieval time

In vitro rescue immature oocytes - a literature review

Immature oocytes retrieved from in vitro fertilization (IVF) and clinical in vitro maturation (IVM) is a common problem, especially in patients with advanced age, poor ovarian response (POR), or polycystic ovary syndrome (PCOS). Considering there is no common name to describe this group of oocytes, we suggest naming all of immature oocytes retrieved from IVF and clinical IVM cycles as 'Medical Unusable Oocytes' (MUO) as none of them will be used for subsequent treatment and will eventually be discarded. Scientists attempt to improve the clinical utilization rate of MUO instead of discarding them. Rescue IVM and mitochondria supplementation may be available approaches to mature MUO. We propose a specific definition of rescue IVM, namely the cultivation and maturation of immature oocytes in vitro collected from IVF cycles with human chorionic gonadotropin (hCG) trigger. Rescue IVM is usually mixed up with clinical IVM. Clarification of the differences between rescue IVM and clinical IVM is necessary. This manuscript aims to clarify the rather confusing IVM procedures and review existing methods of improving rescue IVM, currently available information on the success rate, and explore the future possibility of rescue IVM serving as a promising tool in reproductive medicine.

Should metaphase 1 and 2 stages oocytes be vitrified in the same time for fertility preservation?

Aims: Could metaphase 1 (M1) and 2 (M2) stages oocytes from in vitro maturation (IVM) cycles and controlled-ovarian hyperstimulation (COH) cycles be frozen at the same time without any adverse effect of vitrification on further survival (SR) and maturation rates (MR)? Materials & methods: M1 from cancer patients were prospectively included in IVM/COH groups, and in study or control subgroups if they were vitrified or not. In each study subgroup, SR were compared with that of M2 oocytes vitrified/warmed from egg donors. MR were compared with those of fresh-M1 oocytes from control IVM/COH subgroups. Results: SR were not different between groups. MR compared respectively between survived- and fresh-M1 oocytes were similar when resulting from COH (85.2 vs 81.1%) but significantly lower after IVM (39.1 vs 73.3%). Conclusion: Simultaneous freezing of M1/M2 oocytes could be applied to COH but not to IVM during the course of fertility preservation.

Amino acid turnover by human oocytes is influenced by gamete developmental competence, patient characteristics and gonadotrophin treatment

STUDY QUESTION

Can amino acid profiling differentiate between human oocytes with differing competence to mature to metaphase II (MII) in vitro?

SUMMARY ANSWER

Oocytes which remained arrested at the germinal vesicle (GV) stage after 24 h of in vitro maturation (IVM) displayed differences in the depletion/appearance of amino acids compared with oocytes which progressed to MII and patient age, infertile diagnosis and ovarian stimulation regime significantly affected oocyte amino acid turnover during IVM.

WHAT IS KNOWN ALREADY

Amino acid profiling has been proposed as a technique which can distinguish between human pronucleate zygotes and cleavage stage embryos with the potential to develop to the blastocyst stage and implant to produce a pregnancy and those that arrest. Most recently, the amino acid turnover by individual bovine oocytes has been shown to be predictive of oocyte developmental competence as indicated by the gamete's capacity to undergo fertilization and early cleavage divisions in vitro.

STUDY DESIGN, SIZE, DURATION

The study was conducted between March 2005 and March 2010. A total of 216 oocytes which were at the GV or metaphase I (MI) stages at the time of ICSI were donated by 67 patients.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

The research was conducted in university research laboratories affiliated to a hospital-based infertility clinic. Oocytes were cultured for 24 h and the depletion/appearance of amino acids was measured during the final 6 h of IVM. Amino acid turnover was analysed in relation to oocyte meiotic progression, patient age, disease aetiology and controlled ovarian stimulation regime.

MAIN RESULTS AND THE ROLE OF CHANCE

The depletion/appearance of key amino acids was linked to the maturation potential of human oocytes in vitro. Oocytes which arrested at the GV stage (n = 9) depleted significantly more valine and isoleucine than those which progressed to MI (n = 32) or MII (n = 107) (P < 0.05). Glutamate, glutamine, arginine and valine depletion or appearance differed in MII versus degenerating oocytes (n = 20) (P < 0.05). Glutamine, arginine, methionine, phenylalanine, total depletion and total turnover all differed in oocytes from patients aged < 35 years versus patients ≥35 years (P < 0.05). MII oocytes obtained following ovarian stimulation with recombinant FSH depleted more isoleucine (P < 0.05) and more alanine and lysine (P < 0.05) appeared than oocytes from hMG-stimulated cycles. MII oocytes from patients with a polycystic ovary (PCO) morphology (n = 33) depleted more serine (P < 0.05) than oocytes from women with normal ovaries (n = 61).

LIMITATIONS, REASONS FOR CAUTION

Immature oocytes collected at the time of ICSI were used as the model for human oocyte maturation. These oocytes have therefore failed to respond to the ovulatory hCG trigger in vivo (they are meiotically incompetent), and have limited capacity to support embryo development in vitro. The lack of cumulus cells and stress of the conditions in vitro may have influenced turnover of amino acids, and owing to the small sample sizes further studies are required to confirm these findings.

WIDER IMPLICATIONS OF THE FINDINGS

The findings provide support for the hypothesis that oocyte metabolism reflects oocyte quality. Longitudinal studies are required to link these functional metabolic indices of human oocyte quality with embryo developmental competence. Oocyte amino acid profiling may be a useful tool to quantify the impact of new assisted reproduction technologies (ART) on oocyte quality.

STUDY FUNDING/COMPETING INTERESTS

This project was funded by the UK Biology and Biotechnology Research Council (BB/C007395/1) and the Medical Research Council (G 0800250). K.E.H was in receipt of a British Fertility Society/Merck Serono studentship. H.J.L. is a shareholder in Novocellus Ltd, a company which seeks to devise a non-invasive biochemical test of embryo health.

Prognosis for clinical pregnancy and birth after transferring embryos derived from a cohort of incompletely mature oocytes at retrieval time

The purpose of this retrospective study was to establish a prognosis for implantation, pregnancy and live birth rates in stimulated IVF cycles after transferring embryos derived from: 1/ retrieved immature oocytes that matured overnight in vitro (late mature group: LM); 2/ retrieved immature oocytes that matured overnight in vitro and were added to the embryos derived from retrieved mature oocytes (mixed embryos group: MX); and 3/ retrieved mature oocytes (mature group: M). The obtained implantation, clinical pregnancy and live birth rates for the LM group were: 5.6%, 11.4%, 11.4%; for the MX group were: 4.2%, 14.6%, 11.6%; and for the M group were: 14.6%, 45.2% and 33.3%, respectively. These measurements were significantly lower p<0.05 for the LM and MX groups in comparison to the M group. The number of oocytes retrieved and the number of embryos transferred were the lowest (p<0.001-0.05) for the LM group. It is concluded, that the retrieved immature oocytes are able to mature during overnight culture in vitro, be fertilized and provide developmentally competent embryos with the prognosis of 11% for the successful delivery.

Optimal timing for oocyte denudation and intracytoplasmic sperm injection

Objectives. To analyze the impact of oocyte denudation and microinjection timings on intracytoplasmic sperm injection (ICSI) outcomes. Study Design. We included ICSI cycles with the following parameters: rank 1 or 2, female age <36 years, male factor infertility, long protocol using GnRH agonist and rFSH for ovarian stimulation, and use of freshly ejaculated sperm (n = 110). Several ICSI parameters were analyzed according to the time between oocyte retrieval and denudation (T₁) and the time between denudation and ICSI (T₂) using a statistical logistic regression analysis. Results. Neither T₁ nor T₂ had a significant influence on the Metaphase II (MII) rate but the fertilisation rate (FR) showed a significant improvement when T₁ was longer (optimal results at T₁ = 3 hours) while FR significantly decreased with the increase of T₂. Optimal implantation (IR) and pregnancy (PR) rates were obtained when T₁ was around 2 hours. Conclusion. Incubation of oocytes around 2 hours between retrieval and denudation may not increase MII rate but appears to lead to the optimal combination of FR and IR.