Does blastocyst culture eliminate paternal chromosomal defects and select good embryos?: inheritance of an abnormal paternal genome following ICSI

Chromosome microduplication in somatic cells decreases the genetic stability of human reprogrammed somatic cells and results in pluripotent stem cells

Human pluripotent stem cells, including cloned embryonic and induced pluripotent stem cells, offer a limitless cellular source for regenerative medicine. However, their derivation efficiency is limited, and a large proportion of cells are arrested during reprogramming. In the current study, we explored chromosome microdeletion/duplication in arrested and established reprogrammed cells. Our results show that aneuploidy induced by somatic cell nuclear transfer technology is a key factor in the developmental failure of cloned human embryos and primary colonies from implanted cloned blastocysts and that expression patterns of apoptosis-related genes are dynamically altered. Overall, ~20%–53% of arrested primary colonies in induced plurpotent stem cells displayed aneuploidy, and upregulation of P53 and Bax occurred in all arrested primary colonies. Interestingly, when somatic cells with pre-existing chromosomal mutations were used as donor cells, no cloned blastocysts were obtained, and additional chromosomal mutations were detected in the resulting iPS cells following long-term culture, which was not observed in the two iPS cell lines with normal karyotypes. In conclusion, aneuploidy induced by the reprogramming process restricts the derivation of pluripotent stem cells, and, more importantly, pre-existing chromosomal mutations enhance the risk of genome instability, which limits the clinical utility of these cells.

Reduction in exposure of human embryos outside the incubator enhances embryo quality and blastulation rate

Embryo quality is strongly dependent on the in-vitro culture environment. Conventionally, IVF/intracytoplasmic sperm injection (ICSI) embryos are examined microscopically every morning (from day 1 to day 6) to assess fertilization, cleavage and embryo quality. Consequently, the frequent exposure to non-optimal conditions outside the incubator may adversely affect embryonic viability and quality. Hence, this study investigated whether reduction of observation frequency outside the incubator can enhance blastocyst formation rate. A total of 285 IVF/ICSI cycles were divided into two groups. Embryos in the control group (103 cycles) were assessed out-of-incubator every day after insemination (day 1 to day 6; six times). In the experimental group (182 cycles), embryos were assessed four times, on days 1, 3, 5 and 6. The total blastocyst formation rate, day-5 blastocyst formation rate, proportion of good blastocysts and number of cryopreserved blastocysts per patient were significantly lower for the control group compared with the experimental group (42.5%, 31.4%, 50.7%, 1.72+/-1.55 versus 52.6%, 40.7%, 60.1%, 2.64+/-2.59, respectively, P<0.05); although there were no significant differences in the proportions of good embryos on day 3, blastocyst formation rate on day 6, clinical pregnancy rate and implantation rate. Hence, reduction of the observation frequency of embryos outside the incubator can enhance embryo quality and blastocyst formation rate.

Sperm chromatin structure assay parameters are not related to fertilization rates, embryo quality, and pregnancy rates in in vitro fertilization and intracytoplasmic sperm injection, but might be related to spontaneous abortion rates

OBJECTIVE

To investigate the relationship between sperm chromatin structure assay (SCSA) parameters, DNA fragmentation index (DFI) and high DNA stainability (HDS), and outcomes of IVF and intracytoplasmic sperm injection (ICSI).

DESIGN

Retrospective review and prospective study.

SETTING

Academic human reproduction laboratory.

PATIENT(S)

Two hundred twenty-three couples undergoing conventional IVF (n = 137) and ICSI (n = 86).

INTERVENTION(S)

Testing with SCSA on a semen aliquot taken from ejaculate used for assisted reproductive technology (ART).

MAIN OUTCOME MEASURE(S)

Conventional semen parameters, DFI, HDS, outcomes of IVF and ICSI.

RESULT(S)

There were no significant differences in IVF and ICSI fertilization rate, good embryo rate, and pregnancy rate (PR) between high, moderate, and low DFI or HDS groups. Men with HDS >15% had significantly higher IVF abortion rates. There was a statistically insignificant trend toward an increased abortion rate in the high DFI (>27%) group. The DFI correlated negatively with sperm motility, and HDS correlated negatively with sperm morphology and concentration.

CONCLUSION(S)

Neither DFI nor HDS scores can provide independent information about embryo quality, fertilization, and PRs for infertility patients undergoing ART. Sperm DNA fragmentation probably affects sperm motility. The relationship between HDS and IVF abortion rates provides preliminary evidence that ICSI may be indicated for men with HDS >15%. The potential adverse effect of sperm DNA damage on the quality of postimplantation embryo and spontaneous abortion should be a concern.

Extended embryo culture to increase implantation rate

Multiple pregnancies are a serious adverse event of IVF treatment. Several strategies have been developed to improve embryo selection and embryo developmental potential to increase pregnancy rates without increasing the risk of multiple pregnancies. The only way to effectively solve this problem is to reduce the number of embryos transferred to one. The introduction of extended embryo culture has provided IVF programmes with a valuable tool to select more accurately those embryos with a higher implantation potential. The concept of single embryo transfer presents a clinical dilemma with seemingly opposing sides: one seeking to maintain acceptable pregnancy rates and the other seeking to reduce the number of twin births or high order multiple pregnancies. The present review addresses the potential benefits and drawbacks of blastocyst transfer.

Oocyte dysmorphism is not associated with aneuploidy in the developing embryo

OBJECTIVE

Controlled ovarian hyperstimulation yields numerous oocytes with different morphologic features. The purpose of this study was to assess the effect of oocyte dysmorphism on the development and ploidy status of the derived embryo.

DESIGN

Retrospective study.

SETTING

Private assisted reproduction unit.

PATIENT(S)

A retrospective analysis was performed on 616 oocytes and 266 embryos of 65 infertile couples who had undergone preimplantation genetic diagnosis and aneuploidy screening for repeated implantation failures.

INTERVENTION(S)

Oocytes with normal and abnormal morphology and the derived embryos were compared in terms of fertilization, cleavage, and blastocyst formation rates as well as the ploidy status.

RESULT(S)

Oocyte dysmorphism did not have an adverse effect on fertilization and cleavage rates and quality of day 3 embryos. Single cytoplasmic and multiple abnormalities of the oocyte significantly decreased the blastocyst formation rate of the cleaving embryo. Oocyte dysmorphism did not have a significant association with embryonic aneuploidy.

CONCLUSIONS(S)

Oocyte dysmorphism was not associated with a higher risk of aneuploidy in the developing embryo. Cytoplasmic dysmorphism or multiple morphologic abnormalities of the oocyte adversely affects the blastocyst formation potential of the derived embryo.

Single blastocyst transfer after ICSI from ejaculate spermatozoa, percutaneous epididymal sperm aspiration (PESA) or testicular sperm extraction (TESE)

PURPOSE

To investigate the outcome of IVF following intracytoplasmic sperm injection (ICSI) from ejaculate, percutaneous epididymal sperm aspiration (PESA) and testicular sperm extraction (TESE), with subsequent blastocyst culture and single blastocyst transfer.

METHODS

Single blastocyst transfer was performed after ejaculate ICSI (oligozoospermia) in 587 patients, TESE/PESA (azoospermia) in 31 patients, and standard IVF in 680 women.

RESULTS

There were only minor differences in IVF characteristics between the standard IVF and the PESA-TESE couples. Couples where ejaculate ICSI were performed seemed to represent a slightly poorer prognostic group. A viable fetus after the 12th gestational week, i.e. ongoing pregnancy, was present in 41.4% after ICSI/ET, 51.6% after PESA-TESE/ET and in 40.4% after standard IVF/ET (no significant differences).

CONCLUSION

Single blastocyst transfer after ejaculate ICSI or after PESA/TESE appears to give similar results as conventional IVF blastocyst culture.

Incomplete denudation of oocytes prior to ICSI enhances embryo quality and blastocyst development

BACKGROUND

Granulosa cells are essential mediators of oocyte maturation and fertilization. Because of the denudation of oocytes in preparation for ICSI, any potential positive effect of surplus cumulus cells (CCs) on further development would be unable to exert further effect. In order to evaluate the actual influence of adhering cumulus cells on further preimplantation development, this prospective study was carried out.

METHODS

Sibling cumulus-oocyte complexes for 57 ICSI patients were split into a study group (incomplete denudation, n = 314) and a control group (complete denudation, n = 336). According to the cumulus cell pattern after partial denudation, mature gametes from the study group were further subdivided into type A oocytes, which showed several prominent CC clusters (n = 202), and type B (n = 75), which showed a more homogeneous pattern with CC covering the whole surface of the gamete.

RESULTS

In immature oocytes, presence of adhered CCs led to a significant increase in resumption of meiosis (P < 0.01). Fertilization rate (P < 0.05) and ability to cleave (P < 0.01) was impaired in the study group, because of difficulties in ICSI of type B oocytes. By contrast, embryo morphology on days 2 (P < 0.01) and 3 (P < 0.05), as well as blastocyst formation, was better (P < 0.05) in the study group (55 blastocysts out of 88 zygotes) as compared to that in the control group (49/105).

CONCLUSION

These data indicate that co-culture of oocytes with attached CCs may enhance preimplantation development.

Predictive factors for embryo implantation potential

In spite of recent improvements in IVF, pregnancy rates have not increased significantly and one of the major problems remains the high multiple pregnancy rate. Better criteria are therefore necessary to establish the viability of a transferable embryo. Early prognosis of the developmental fate of the oocyte would help in selecting the best embryos to transfer, but non-invasive selection at the oocyte stage (extracytoplasmic and intracytoplasmic morphology) has proved to be of little prognostic value. Recently, it has been shown that follicular vascularization appears to be predictive of oocyte developmental fate, making it a good first-step approach for selection. Observation of pronuclei patterns at the zygote stage appears to offer an additional prognostic tool, correlating well with IVF outcome. Morphological evaluation of the embryo at days 2-3 remains the most used and valid method of selection, even though it is not sufficient to select embryos with the higher implantation potential. Blastocyst culture is another possible strategy for selecting the best embryos with reduced risk of aneuploidies, though not all major chromosomal aberrations are excluded by prolonged in-vitro culture. In summary, selecting the best embryo for transfer is a decision that should be based on choices made during the different stages of assisted reproductive technologies.

Intégrité de l'ADN des spermatozoïdes comme élément diagnostique et pronostique de la fertilité masculine

Recent progress in reproductive biology has improved comprehension physiology of the spermatozoa and on the fertilization mechanisms. This new knowledge has carried out the elaboration of tests on male fertility based on sperm genomic integrity. This review presents some of these techniques and brings a reflexion element on the application and use of sperm DNA integrity in the investigation of male fertility. The single cell gel electrophoresis (COMET assay), Sperm Chromatin Structure Assay (SCSA), In Situ Nick Translation (NT: Nick Translation) and Terminal Uridine Nick-End Labelling (TUNEL assay) are actually the most currently used techniques for the measure of sperm DNA integrity in research clinic. From a certain point of view, TUNEL assay, SCSA, COMET assay and NT assay are complementary. The TUNEL and COMET can measure single and double strand breaks of DNA, the SCSA can detect the abnormalities in the chromatin compaction and the NT assay can detect the single strand breaks of DNA. The exact origin of sperm DNA fragmentation is not established yet. However, several mechanisms have been proposed: defect in the chromatin compaction during spermiogenesis; reactive oxygen species production by immature spermatozoa; apoptosis during spermatogenesis. It becomes important to consider the possible consequences of the oocyte fertilization by a spermatozoon having a high degree of DNA fragmentation. The use in routine of some of these tests must however pass by a standardization of the inter laboratory protocols and obviously, by the establishment of both in vivo and in vitro discriminating threshold values in order for these tests to present a good predictive value for pregnancy outcome.

Role of reactive oxygen species in gynecologic diseases

Free radicals derived from molecular oxygen and nitrogen are highly reactive metabolites called reactive oxygen species (ROS). Cells continuously produce free radicals and ROS as part of the metabolic process. They are involved in the various functions of the reproductive system. Antioxidants are enzymes or compounds that scavenge and reduce the presence of free radicals. Normally, a balance exists between concentrations of reactive oxygen species and antioxidant scavenging systems. The disruption of the delicate balance between pro- and antioxidants results in oxidative stress. Oxidative stress has been implicated in embryo fragmentation, DNA damage, apoptosis and poor pregnancy outcome. It has also been implicated in a large number of gynecologic diseases, such as endometriosis, pre-eclampsia and maternal diabetes. The use of antioxidants may be beneficial in combating the harmful effects of oxidative stress in many of these diseases. The present review outlines the importance of these species in the pathology of various gynecologic diseases. (Reprod Med Biol 2004; 3: 177 - 199).

Sperm chromatin structure assay (SCSA) parameters are related to fertilization, blastocyst development, and ongoing pregnancy in in vitro fertilization and intracytoplasmic sperm injection cycles

OBJECTIVE

To determine the relationship between sperm chromatin structure assay (SCSA) parameters (DNA fragmentation index [DFI] and high DNA stainability [HDS]), and conventional IVF and IVF/intracytoplasmic sperm injection (ICSI) outcomes.

DESIGN

Retrospective review and prospective study.

SETTING

Private IVF clinic.

PATIENT(S)

Two hundred forty-nine couples undergoing first IVF and/or ICSI cycle.

INTERVENTION(S)

IVF, ICSI, blastocyst culture.

MAIN OUTCOME MEASURE(S)

DFI, HDS, conventional semen parameters, IVF, ICSI.

RESULT(S)

IVF and ICSI fertilization rates were not statistically different between high- and low-DFI groups. More men with > or =15% HDS had lower (<25% and <50%) IVF fertilization rates. High DNA stainability was not related to ICSI fertilization rates. High DNA stainability did not affect blastocyst rates or pregnancy outcomes. Men with > or =30% DFI were at risk for low blastocyst rates (<30%) and no ongoing pregnancies. Men with > or =30% DFI had more male factors. World Health Organization thresholds were not predictive of ongoing pregnancy.

CONCLUSION(S)

The relationship between HDS and poor IVF fertilization rates provides preliminary evidence that ICSI may be indicated in men with > or =15% HDS. Men with high levels of DNA fragmentation (> or =30% DFI) were at greater risk for low blastocyst rates and failure to initiate an ongoing pregnancy. The SCSA provides valuable prognostic information to physicians counseling couples before IVF and/or ICSI cycles.

Pronuclear morphology predicts embryo development and chromosome constitution

The relationship between pronuclear morphology on the one hand, and embryo development and chromosomal status on the other, was evaluated in 68 couples scheduled to undergo preimplantation genetic diagnosis because of advanced maternal age or recurrent implantation failure. Zygotes were grouped according to their pronuclear (PN) morphology. During the period from fertilization to embryo transfer, cleavage rate, embryo quality, blastocyst formation and results of the chromosomal analysis of 240 embryos were recorded. Both embryo cleavage characteristics and chromosome constitution were related to PN morphology. Embryos developing from zygotes with the normal PN pattern (pattern 0) cleaved faster and formed embryos with better morphology as compared with zygotes with abnormal PN patterns. Aneuploidy rate of embryos derived from zygotes with the normal PN pattern, with a single PN anomaly and with a double PN anomaly was 25.6, 73 and 83% respectively. Chromosomally normal embryos with the normal PN pattern progressed to the blastocyst stage at a higher rate (90%) than chromosomally normal embryos with a single (61%) or a double (40%) PN anomaly. The same relationship applied to chromosomally abnormal embryos. It is concluded that PN morphology predicts both the risk of embryo developmental arrest and that of chromosomal abnormalities.