Highly effective method of human oocyte activation

Design of novel oocyte activation methods: The role of zinc

Oocyte activation occurs at the time of fertilization and is a series of cellular events initiated by intracellular Ca2+ increases. Consequently, oocytes are alleviated from their arrested state in meiotic metaphase II (MII), allowing for the completion of meiosis. Oocyte activation is also an essential step for somatic cell nuclear transfer (SCNT) and an important tool to overcome clinical infertility. Traditional artificial activation methods aim to mimic the intracellular Ca2+ changes which occur during fertilization. Recent studies emphasize the importance of cytoplasmic Zn2+ on oocyte maturation and the completion of meiosis, thus suggesting artificial oocyte activation approaches that are centered around the concentration of available Zn2+in oocytes. Depletion of intracellular Zn2+ in oocytes with heavy metal chelators leads to successful oocyte activation in the absence of cellular Ca2+ changes, indicating that successful oocyte activation does not always depends on intracellular Ca2+ increases. Current findings lead to new approaches to artificially activate mammalian oocytes by reducing available Zn2+ contents, and the approaches improve the outcome of oocyte activation when combined with existing Ca2+ based oocyte activation methods. Here, we review the important role of Ca2+ and Zn2+ in mammalian oocyte activation and development of novel oocyte activation approaches based on Zn2+ availability.

Fourteen babies born after round spermatid injection into human oocytes

During the human in vitro fertilization procedure in the assisted reproductive technology, intracytoplasmic sperm injection is routinely used to inject a spermatozoon or a less mature elongating spermatid into the oocyte. In some infertile men, round spermatids (haploid male germ cells that have completed meiosis) are the most mature cells visible during testicular biopsy. The microsurgical injection of a round spermatid into an oocyte as a substitute is commonly referred to as round spermatid injection (ROSI). Currently, human ROSI is considered a very inefficient procedure and of no clinical value. Herein, we report the birth and development of 14 children born to 12 women following ROSI of 734 oocytes previously activated by an electric current. The round spermatids came from men who had been diagnosed as not having spermatozoa or elongated spermatids by andrologists at other hospitals after a first Micro-TESE. A key to our success was our ability to identify round spermatids accurately before oocyte injection. As of today, all children born after ROSI in our clinic are without any unusual physical, mental, or epigenetic problems. Thus, for men whose germ cells are unable to develop beyond the round spermatid stage, ROSI can, as a last resort, enable them to have their own genetic offspring.

The combined treatment of calcium ionophore with strontium improves the quality of ovine SCNT embryo development

Poor embryo quality is a major problem that contributes to the failure of pregnancy in somatic cell nuclear transfer (SCNT). The aims of this study were to improve the quality of ovine SCNT embryos by modifying the conventional activation protocol with the addition of SrCl2. In order to achieve this objective we conducted a series of experiments with in vitro-matured oocytes to optimize conditions for oocyte activation with strontium, and subsequently applied the protocol to SCNT embryos. The results showed that in vitro-matured oocytes could be activated effectively by 10 mM SrCl2 + 5 mg/ml cytochalasin B (CB) for 5 h in the absence of Ca2+ and that the blastocyst rate on day 7 (33.2%) was similar to that in the control group (31.0%) (5 M calcium ionophore [IP] A23187 for 5 min and cultured in CB/cycloheximide [CHX] for 5 h; P > 0.05). In SCNT experiments, the total cell number/blastocyst (104.12 ± 6.86) in the IP + SrCl2/CB-treatment group was, however, significantly higher than that in the control group (81.07 ± 3.39; P < 0.05). Apoptotic index (12.29 ± 1.22%) was significantly lower than the control (17.60 ± 1.39%; P < 0.05) when a combination of IP and SrCl2/CB was applied to SCNT embryos. In addition, karyotyping of the SCNT embryos showed that the percentage of diploid blastocysts in the IP + SrCl2/CB-treatment group was slightly higher than that in the control (P > 0.05). We conclude that the modified activation protocol with IP + SrCl2/CB can improve significantly the quality of ovine SCNT embryos in terms of total cell number, apoptosis and ploidy.

The dynamics of in vitro maturation of germinal vesicle oocytes

OBJECTIVE

To evaluate the dynamics of the nuclear maturation (NM) of in vitro-matured (IVM) oocytes and to determine the most favorable duration of meiosis II (MII) arrest in relation to the normal activation response.

DESIGN

Experimental.

SETTING

University-affiliated infertility clinic.

PATIENT(S)

Donated immature germinal vesicle oocytes (GV).

INTERVENTION(S)

The GV underwent spontaneous IVM and the dynamics of NM studied by real-time monitoring. The IVM oocytes were parthenogenetically activated at different MII arrest points and their response assessed.

MAIN OUTCOME MEASURE(S)

Moment of GV breakdown; extrusion of the first polar body; duration of MI and MII arrest; activation rate (AR) and type.

RESULT(S)

Two GV populations-early (E-IVM, 18.4 ± 2.7 hours) and late (L-IVM, 26.3 ± 3.8 hours) maturing-were defined according to the time required for extrusion of the first polar body. Significantly more E-IVM than L-IVM exhibited a normal activation response (61.3% vs. 34.6%), but AR were similar (average, 88.6%) in both groups. Duration of the GV stage differed between the two groups, but MI arrest (14.0 ± 0.3 hours) was constant. The E-IVM arrested at MII for at least 4.3 hours displayed significantly lower AR and similar normal activation rates (61.3%) to E-IVM arrested for a shorter time (83.9% vs. 100%). The L-IVM displayed a similar AR (80.8%), but lower normal activation rates than E-IVM (34.6%), regardless of when activation took place.

CONCLUSION(S)

The success of IVM depends on the NM timing rather than on the length of MII arrest.

An obscure rider obstructing science: the conflation of parthenotes with embryos in the Dickey-Wicker amendment

In 1996 Congress passed the Dickey-Wicker Amendment (DWA) as part of an appropriations bill; it has been renewed every year since. The DWA bans federal funding for research using embryos and parthenotes. In this paper, we call for a public discussion on parthenote research and a questioning of its inclusion in the DWA. We begin by explaining what parthenotes are and why they are useful for research on reproduction, cancer, and stem cells. We then argue that the scientific difference between embryos and parthenotes translates into ethical differences, and claim that research on parthenotes is much less ethically problematic. Finally, we contextualize the original passage of the DWA to provide an explanation for why the two were possibly conflated in this law. We conclude by calling for a public discussion on reconsidering the DWA in its entirety, starting with the removal of parthenogenesis from this prohibition of National Institutes of Health (NIH) funding.

Spontaneous in vitro maturation and artificial activation of human germinal vesicle oocytes recovered from stimulated cycles

PURPOSE

To define germinal vesicles (GV) by morphometric and morphologic examination and by chromatin compaction and to assess their spontaneous nuclear and cytoplasmic competence.

MATERIALS

131 GV were cultured for 42.7 ± 2.4 h. Nuclear maturation was evaluated at four time points. Sixty-seven in vitro and twenty-five in vivo metaphase II (MII) were activated. Parthenotes with 2 PB and one pronucleus (NA) were studied for ploidy.

RESULTS

A total of 74.8% GV matured to MII: 55% at 21.4 ± 2.4 h and 47.3% in the following 24 h. Artificial activation induced NA in 79.2% of in vivo-MII and in 22.4% of in vitro-MII. All NA were haploid.

CONCLUSIONS

GV spontaneously mature at the nuclear level. Their NA are haploid, but their cytoplasmic competence is compromised. Variables were not found to be predictors of oocyte competence, probably due to our population being homogeneous with respect to most of the variables studied.

Human parthenogenetic blastocysts derived from noninseminated cryopreserved human oocytes

OBJECTIVE

To report on the development of human parthenogenetic blastocysts and an in vitro attachment that was generated from noninseminated cryopreserved human oocytes for the first time.

DESIGN

Prospective study.

SETTING

Department of reproductive medicine in a medical institute in Buenos Aires, Argentina.

PATIENT(S)

Five healthy fertile donors.

INTERVENTION(S)

Artificial activation of noninseminated cryopreserved human oocytes after thawing, parthenote culture, and their in vitro attachment.

MAIN OUTCOME MEASURE(S)

Survival rate, activation rate, cleavage rate, and blastocyst formation.

RESULT(S)

Thirty-six of 38 cryopreserved noninseminated oocytes survived after thawing (survival rate, 94.7%). Thirty-one of 36 oocytes showed one pronucleus (activation rate, 86.1%). Thirty of 31 cleaved (cleavage rate, 96.8%). Five of 30 showed cavitation (blastocyst rate, 16.7%).

CONCLUSION(S)

Noninseminated cryopreserved human oocytes showed a high survival rate after thawing. They responded very satisfactorily to artificial activation, which was followed by a high rate of parthenogenetic embryos, which can develop into blastocysts. In the future, these could be a new source for development of human parthenogenetic stem cells.

Poor development of human nuclear transfer embryos using failed fertilized oocytes

Failed fertilized human oocytes from IVF were enucleated and used as recipients for somatic cell nuclear transfer. The reconstructed embryos frequently formed an expanded nucleus from the injected genome after activation. However, subsequent development beyond the 1-cell stage was poor, and the resulting embryos showed chromosomal abnormalities. Poor development of oocytes after nuclear transfer contrasted with that of control, sperm-injected oocytes, which often progressed to cleavage stages. These results suggest that failed fertilized oocytes are not effective recipients for somatic cell nuclear transfer.

Nuclear Dynamics of Parthenogenesis of Human Oocytes: Effect of Oocyte Aging in vitro

We investigated in detail the nuclear kinetics of oocyte activation of aged human oocytes following combined activation treatment with calcium ionophore and puromycin. Two types of oocytes were used: (a) 1-day-old oocytes after 20-24 h retrieval, and (b) 2-day-old oocytes after 44-50 h retrieval. A total of 185 unfertilized aged oocytes, 91 1-day-old and 94 2-day-old oocytes, were fixed at 1, 2, 4, 6 and 8 h after activation treatment and then metaphase II (MII), anaphase or telophase II (A/T II) or pronuclear stage were recorded. We demonstrated that a combined calcium ionophore and puromycin treatment induced a high activation rate in both 1-day-old (95.6%) and 2-day-old oocytes (95.2%). Our results also demonstrated that the nuclear progression was faster in 2-day-old oocytes than in 1-day-old oocytes, although nuclear progression in parthenogenetically activated human oocytes requires the longer time periods compared with ICSI fertilization. It is concluded that combined treatment of the calcium ionophore and puromycin allows a high rate of parthenogenetic activation and the nuclear kinetics of parthenogenetically activated human oocytes appears to be more rapid in in vitro aging oocytes.

Parthenogenetic activation of marmoset (Callithrix jacchus) oocytes and the development of marmoset parthenogenones in vitro and in vivo

Mammalian oocytes can be induced to resume meiosis without fertilization, and the resulting parthenogenetic embryos carry only maternal chromosomes. Human oocytes can be activated by many chemical and physical stimuli, but postimplantation studies of human parthenogenetic embryos are not ethically acceptable. The common marmoset monkey (Callithrix jacchus) is a good model for studying primate parthenogenetic development postimplantation, since follicular aspiration, embryo transfer, and early postimplantation development of biparental embryos have already been described. Marmoset oocytes were either subjected to two series of six electrical pulses (DC; 2 kV/cm and 70 microsec) or were incubated in 7% ethanol in PBS. Ninety-two percent (68 of 74) and 20% (8 of 40) of marmoset oocytes were activated by electrical stimulus or ethanol, respectively. Parthenogenetic (n = 3) or in vitro-fertilized (n = 2) embryos were transferred at the 4-cell stage to synchronized recipient female marmosets (n = 5). Progesterone, chorionic gonadotropin, and inhibin in the peripheral plasma of recipient animals were measured. After 33 days of gestation, recipient animals were perfused and the uteri were collected. The 2 females that had received biparental embryos and 2 of the 3 females that had received parthenogenetic embryos displayed biochemical and histological evidence of implantation. This is the first report that a primate embryo comprising only parthenogenetic cells is capable of implantation. This highlights the need to scrutinize levels of parthenogenesis associated with human assisted reproductive technologies. Marmoset parthenogenones also provide a unique model for elucidating the roles of parental genomes in primate development.

Fertilization and pregnancy after assisted oocyte activation and intracytoplasmic sperm injection in a case of round-headed sperm associated with deficient oocyte activation capacity

OBJECTIVE

To investigate a method of assisted activation of human oocytes for the treatment of infertility resulting from globozoospermia associated with deficient oocyte activation capacity.

DESIGN

The mouse oocyte activation test was used to analyze the oocyte activation capacity of the sperm cells of a patient with globozoospermia. Fresh donor human oocytes were used for determining the most appropriate procedure for oocyte activation.

SETTING

Infertility Center, University Hospital of Ghent.

PATIENT(S)

A couple with infertility resulting from globozoospermia.

INTERVENTION(S)

Intracytoplasmic sperm injection, assisted oocyte activation, and embryo transfer.

MAIN OUTCOME MEASURE(S)

Oocyte activation and fertilization rates, implantation, and pregnancy.

RESULT(S)

Deficiency in oocyte activation capacity was found in the sperm of a patient with globozoospermia. This deficiency was proven by the mouse oocyte activation test and was confirmed further by lack of activation of human oocytes after simple sperm injection. Only human oocytes that were injected with sperm and subjected to calcium chloride and ionophore treatment underwent activation. Transfer of embryos obtained by this procedure of assisted oocyte activation resulted in an ongoing pregnancy.

CONCLUSION(S)

Assisted oocyte activation of human oocytes is useful when globozoospermia is associated with absence of oocyte activation capacity in the sperm. These cases can be identified by the mouse oocyte activation test.