Failed fertilization in vitro: second day micromanipulation of oocytes versus reinsemination

A comparison of the clinical outcomes of embryos derived from intracytoplasmic sperm injection after early fertilization check and conventional insemination using sibling oocytes

PURPOSE

In order to identify the real contribution of early fertilization check (EFC) for reproductive outcome, we compared the developmental potential of embryos derived from intracytoplasmic sperm injection (ICSI) after EFS with those from conventional insemination in sibling oocytes.

METHODS

Between April 2009 and April 2012, a total of 3249 oocytes in 386 patients were recruited following conventional insemination. Oocytes showing a second polar body (2ndPB) after an EFC were considered to be fertilized oocytes (IVF group), but, oocytes not showing a 2ndPB after EFC were placed into the ICSI group. The incidence of morphologically good embryos (MGE) on day 3, the blastocyst formation (BL), and the development of full blastocysts (full-BL) on day 5 were compared between the two groups. The clinical pregnancy rate was compared between the cycles with only conventional insemination or ICSI after EFC of the embryos being transferred.

RESULTS

The fertilization rates in both the IVF and the ICSI groups were 48.1 and 73.9 %, respectively. The percentage of MGE in the ICSI group (40.8 %) was significantly lower than that in the IVF group (56.1 %, p < 0.01). The percentages of BL and full-BL in the ICSI group were significantly lower than those in the IVF group. The pregnancy rates were similar in both the groups.

CONCLUSIONS

Checking fertilization earlier than the usual period contributed to an avoidance of lower fertilization. Moreover, the embryos derived from ICSI after EFC possessed a normal developmental potential.

Association between etiologic factors in infertile couples and fertilization failure in conventional in vitro fertilization cycles

The aim of this study was to investigate the relationship between the etiology of the couples and risk of fertilization failure (FF) in conventional in vitro fertilization (IVF) cycles and the effect of rescue intracytoplasmic sperm injection (ICSI) technique to offspring. A total of 2542 IVF cycles were divided into four groups according to infertile etiology: Group A - primary infertility with normal semen parameters; Group B - secondary infertility with oligoasthenozoospermia; Group C - primary infertility with oligoasthenozoospermia; and Group D - secondary infertility with normal semen parameters. The results showed that there were significant differences in incidence of FF among Group A (16.8%), Group B (20.9%), Group C (48.7%), and Group D (0.9%) (p < 0.001). Logistic regression models demonstrated that primary infertility (OR: 10.898, 95% CI: 4.651-25.583, p < 0.001) and oligoasthenozoospermia (OR: 12.215, 95% CI: 5.903-25.276, p < 0.001) were independent risk factors for FF. There were no significant differences in main outcomes between conventional ICSI and rescue ICSI. In conclusion, the patients with primary infertility and oligoasthenozoospermia might be at higher risk of FF. The rescue ICSI technique is safe and helpful for IVF cycles of FF.

Oxidative stress and ageing of the post-ovulatory oocyte

With extended periods of time following ovulation, the metaphase II stage oocyte experiences deterioration in quality referred to as post-ovulatory oocyte ageing. Post-ovulatory ageing occurs both in vivo and in vitro and has been associated with reduced fertilization rates, poor embryo quality, post-implantation errors and abnormalities in the offspring. Although the physiological consequences of post-ovulatory oocyte ageing have largely been established, the molecular mechanisms controlling this process are not well defined. This review analyses the relationships between biochemical changes exhibited by the ageing oocyte and the symptoms associated with the ageing phenotype. We also discuss molecular events that are potentially involved in orchestrating post-ovulatory ageing with a particular focus on the role of oxidative stress. We propose that oxidative stress may act as the initiator for a cascade of events that create the aged oocyte phenotype. Specifically, oxidative stress has the capacity to cause a decline in levels of critical cell cycle factors such as maturation-promoting factor, impair calcium homoeostasis, induce mitochondrial dysfunction and directly damage multiple intracellular components of the oocyte such as lipids, proteins and DNA. Finally, this review addresses current strategies for delaying post-ovulatory oocyte ageing with a particular focus on the potential use of compounds such as caffeine or selected antioxidants in the development of more refined media for the preservation of oocyte integrity during IVF procedures.

Oxidative stress and ageing of the post-ovulatory oocyte

With extended periods of time following ovulation, the metaphase II stage oocyte experiences deterioration in quality referred to as post-ovulatory oocyte ageing. Post-ovulatory ageing occurs both in vivo and in vitro and has been associated with reduced fertilization rates, poor embryo quality, post-implantation errors and abnormalities in the offspring. Although the physiological consequences of post-ovulatory oocyte ageing have largely been established, the molecular mechanisms controlling this process are not well defined. This review analyses the relationships between biochemical changes exhibited by the ageing oocyte and the symptoms associated with the ageing phenotype. We also discuss molecular events that are potentially involved in orchestrating post-ovulatory ageing with a particular focus on the role of oxidative stress. We propose that oxidative stress may act as the initiator for a cascade of events that create the aged oocyte phenotype. Specifically, oxidative stress has the capacity to cause a decline in levels of critical cell cycle factors such as maturation-promoting factor, impair calcium homoeostasis, induce mitochondrial dysfunction and directly damage multiple intracellular components of the oocyte such as lipids, proteins and DNA. Finally, this review addresses current strategies for delaying post-ovulatory oocyte ageing with a particular focus on the potential use of compounds such as caffeine or selected antioxidants in the development of more refined media for the preservation of oocyte integrity during IVF procedures.

Successful live birth after rescue ICSI following failed fertilization

In a conventional IVF cycle unexpected complete fertilization failure may occur in 10-25% of infertile women. To overcome this barrier of fertilization failure, some investigators have suggested intracytoplasmic sperm injection (ICSI) on day 1 of an unfertilized mature oocyte, the so called “rescue ICSI”. We report a case of fertilization failure followed by rescue ICSI resulting in a live birth. Although the success of rescue ICSI is still questionable, this procedure is worth an attempt in order to give the best chance to the couple in that cycle.

Effects of cumulus cells removal after 6 h co-incubation of gametes on the outcomes of human IVF

PURPOSE

To investigate the effects of cumulus cells removal after 6 h co-incubation of gametes on the fertilization, polyspermy, multinucleation and clinical pregnancy rates in human IVF.

METHODS

A total of 1,200 IVF-ET cycles undergoing 6 h co-incubation of gametes in 2009 were included in this study. Inclusion criteria were: female age <38 years, first IVF treatment, with bi-ovary and normal ovarian response, e.g., 4 ~ 20 oocytes could be obtained. A 6 h period of co-incubation was applied in all IVF cycles. According to the history of infertility, cumulus cells were mechanically removed either 6 h post-insemination or 20 h post-insemination. For couples with primary infertility, or unexplained infertility, or mild oligospermia or asthenospermia, the cumulus cells were removed at 6 h of insemination for the polar body observation (6 h group, n = 565). Of these, 80 cycles received early rescue ICSI due to fertilization failure or low fertilization rate at 6 h of insemination. For couples with secondary infertility and normal semen analysis, the cumulus cells were removed at 20 h of insemination as routine (20 h group, n = 635). Of these, three cycles received late rescue ICSI due to fertilization failure at 20 h of insemination. Normal fertilization, polyspermy (≥3PN), multinucleation and clinical pregnancy rates were compared between the two groups (rescue ICSI cycles were not included in the comparison in both groups).

RESULTS

Significant difference (P < 0.05) was observed between the groups regarding polyspermy rates (7.48% in 6 h group and 9.22% in 20 h group). No difference was observed between the groups regarding normal fertilization rates (2PN rate) (64.89% in 6 h group and 65.74% in 20 h group). No difference was observed between the groups regarding multinucleation and clinical pregnancy rates (11.01% and 65.15% in 6 h group, 10.75% and 66.93% in 20 h group, respectively). The clinical pregnancy rate was 51.43% in cycles receiving early rescue ICSI, while no clinical pregnancy was obtained in cycles receiving late rescue ICSI.

CONCLUSION

The present results indicate that cumulus cells removal at 6 h of insemination is a relatively safe operation, which yielded comparable normal fertilization rate, multinucleation and clinical pregnancy rates compared with 20 h group. This protocol may be beneficial for early obsevation of fertilization failure and make early rescue ICSI possible.

How to improve the success rate of mouse cloning technology

It has now been 13 years since the first cloned mammal Dolly the sheep was generated from somatic cells using nuclear transfer (SCNT). Since then, this technique has been considered an important tool not only for animal reproduction but also for regenerative medicine. However, the success rate is still very low and the mechanisms involved in genomic reprogramming are not yet clear. Moreover, the NT technique requires donated fresh oocyte, which raises ethical problems for production of human cloned embryo. For this reason, the use of induced pluripotent stem cells for genomic reprogramming and for regenerative medicine is currently a hot topic in this field. However, we believe that the NT approach remains the only valid way for the study of reproduction and basic biology. For example, only the NT approach can reveal dynamic and global modifications in the epigenome without using genetic modification, and it can generate offspring from a single cell or even a frozen dead body. Thanks to much hard work by many groups, cloning success rates are increasing slightly year by year, and NT cloning is now becoming a more applicable method. This review describes how to improve the efficiency of cloning, the establishment of clone-derived embryonic stem cells and further applications.

Nuclear reprogramming to produce cloned mice and embryonic stem cells from somatic cells

Cloning methods in mice are now well described and are becoming routine. However, the frequency at which cloned mice are produced remains below 5%, irrespective of the nucleus donor species or cell type. Only a few laboratories have made clones from adult mouse somatic cells and most strains have never produced cloned mice. On the other hand, nuclear transfer can be used to generate human embryonic stem (ntES) cell lines from a patient's own somatic cells. It has been shown that such cells can be generated relatively easily from a variety of mouse genotypes and cell types of both sexes, even though it may be more difficult to generate clones directly. This technique could be used in regenerative medicine and, in theory, in infertility clinics to treat completely infertile individuals. However, these results suggest that the reprogramming integrity of each cloned embryo differs: some cloned embryos can be converted to ntES cells, but these embryos cannot achieve full term development. This review outlines the nature of genomic reprogramming potential and its application, and suggests new approaches to avoid the ethical problems of creating embryos by nuclear transfer.

Low blastocyst formation rates in day-2 fertilized oocytes

PURPOSE

To examine the blastocyst formation rates of day-2 fertilized oocytes.

METHODS

A retrospective study of the outcomes/blastocyst formation of day-2 fertilized oocytes was undertaken.

RESULTS

Fertilization rates of day-1 and -2 oocytes by intra-cytoplasmic sperm injection were similar. The development frequencies to four cells were similar. However, the blastulation rates were significantly lower from the day-2 fertilized eggs. The fertilization rates from day-2 conventional in vitro fertilization reinsemination were lower than the fertilization rates of day-1 oocytes. The blastulation rates from day-2 fertilized eggs were also lower than the rates from day-1 fertilized eggs in the in vitro fertilization group.

CONCLUSIONS

Fertilization is not a good indicator to predict the viability of fertilized oocytes. Day-2 fertilized oocytes had significantly lower blastocyst formation rates than the rates from day-1 fertilized oocytes.