Cell and molecular biological challenges of ICSI: ART before science?

Are we ready for genome editing in human embryos for clinical purposes?

Perhaps the two most significant pioneering biomedical discoveries with immediate clinical implications during the past forty years have been the advent of assisted reproductive technologies (ART) and the genetics revolution. ART, including in vitro fertilization (IVF), intracytoplasmic sperm injection and preimplantation genetic testing, has resulted in the birth of more than 8 million children, and the pioneer of IVF, Professor Bob Edwards, was awarded the 2010 Nobel Prize. The genetics revolution has resulted in our genomes being sequenced and many of the molecular mechanisms understood, and technologies for genomic editing have been developed. With the combination of nearly routine ART protocols for healthy conceptions together with almost error-free, inexpensive and simple methods for genetic modification, the question "Are we ready for genome editing in human embryos for clinical purposes?" was debated at the 5th congress on controversies in preconception, preimplantation and Prenatal Genetic Diagnosis, in collaboration with the Ovarian Club Meeting, in November 2018 in Paris. The co-authors each presented scientific, medical and bioethical backgrounds, and the debate was chaired by Professor Alan Handyside. In this paper, we consider whether genome editing is safe and ethical. We conclude that we are currently not ready for genome editing to be used in human embryos for clinical purposes, and we call for a global debate to determine if and when this technology could be used in ART. ‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬‬.

Human Sperm Centrosomal Function during Fertilization, a Novel Assessment for Male Sterility

In human fertilization, the sperm introduces the centrosome-the microtubule organizing center-and microtubules are organized within the inseminated egg from the sperm centrosome. These microtubules form a radial array, the sperm aster, the functioning of which is essential for pronuclear movement for the union of the male and female genomes. We established functional assay for human sperm centrosomal function, by using heterologus ICSI system with bovine and rabbit eggs. After human sperm incorporation into mammalian egg, we observed that the sperm aster was organized from sperm centrosome, and the sperm aster enlarged as the sperm nuclei underwent pronuclear formation. The normal human sperm aster formation rate at 6 h post-ICSI were 60.0% in bovine egg and 36.1% in rabbit egg, respectively. However, sperm aster formation rate following heterologus ICSI into bovine eggs with teratozoospermia (globozoospermia, dysplasia of fibrous sheath) were low. These data indicate that human sperm centrosomal function is low in abnormal shaped sperm. Wherus, elucidation of human sperm centrosomal function can lead us to find a new type of failure in "post ICSI events in fertilization".

Assessing centrosomal function of infertile males using heterologous ICSI

The human spermatozoal centrosome acts as a microtubule organizing center and is essential for male and female pronuclear migration and apposition. In this study, we assess centrosomal function of spermatozoa from infertile patients using heterologus intracytoplasmic sperm injection (ICSI) into bovine eggs. Spermatozoa from 15 infertile patients undergoing assisted reproductive technology (ART) treatment and 3 fertile donors were tested. Microtubules and DNA were imaged by immuocytochemistry and epifluorescence microscopy. Decondensed female chromosomes and sperm nuclei, pronuclear formation and sperm aster formation were examined. The average rate of sperm aster formation using spermatozoa from infertile individuals was lower (47.0%) than that with spermatozoa from fertile individuals (66.1%). We compared the sperm aster formation rates after ART with various clinical parameters, including semen characteristics, pronuclear formation rates, embryonic cleavage rates and pregnancy outcome. Clinical semen characteristics and the rate of pronuclear formation appeared independent of sperm centrosomal function. In contrast, the centrosomal function had a substantial effect on embryonic cleavage rate and pregnancy after ART. These results suggested that centrosomal function is essential for pregnancy and embryonic development. The method described using bovine eggs is suitable to assay human centrosome function and predict pregnancy after ART.

Comparison of mice born after intracytoplasmic sperm injection with in vitro fertilization and natural mating

The procedures of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) are routinely used in modern medicine to overcome infertility and, in animal husbandry, to propagate lines with compromised fertility. However, there remains concern that manual selection and injection of whole sperm into oocytes could contribute to pre- and postnatal developmental defects. To address this, we have used gene expression profiling and immunophenotyping to characterize offspring generated by these procedures. We used gametes from glutathione peroxidase 1 knockout (Gpx1-/-) mice as a sensitized screen responsive to oxidative stress from artificial reproduction technologies (ART). There were no differences between IVF and ICSI derived offspring in gene expression patterns, and minor differences in hematopoietic parameters. Furthermore there were only minor differences between these IVF and ICSI pups and those derived from natural mating. These data demonstrate for the first time in that there is no significant phenotypic affects of ICSI when compared to IVF and we identified a relatively minor influence of the artificial fertilization methods on phenotype of offspring compared with natural mating. These observations would support the use of ICSI for derivation of mutant mouse lines and may be of some importance for the use of this technique in human ART.

Intracytoplasmic sperm injection: a novel selection method for sperm with normal frequency of chromosomal aneuploidies

OBJECTIVE

To test a newly invented intracytoplasmic sperm injection (ICSI) sperm selection method based on sperm hyaluronic acid (HA) binding.

DESIGN

Comparison of chromosomal disomy and diploidy frequencies in sperm arising from semen and in HA-bound sperm.

SETTING

Academic andrology laboratory.

PATIENT(S)

Men presenting for semen analysis.

INTERVENTION(S)

Washed sperm fractions of 32 semen samples were applied to Petri dishes or glass slides coated with immobilized HA. The unbound sperm were rinsed gently, and the HA-bound sperm were removed with an ICSI pipette. The control sperm population was the unselected sperm. Both HA-selected and unselected sperm were treated with fluorescence in situ hybridization with centromeric probes for the X, Y, and 17 chromosomes.

MAIN OUTCOME MEASURE(S)

Chromosomal disomy and diploidy frequencies.

RESULT(S)

In the HA-bound sperm (495-2,079 per man, 41,670 in all) compared with unselected sperm (4,770 per man, 162,210 in all), the chromosomal disomy frequencies were reduced to 0.16% from 0.52%, diploidy to 0.09% from 0.51%, and sex chromosome disomy to 0.05% from 0.27% (a 5.4-fold reduction vs. 4-fold respective increase in ICSI offspring).

CONCLUSION(S)

The HA sperm selection method for ICSI, which is based on a relationship between sperm receptors for zona pellucida and HA, will likely reduce the potential genetic complications and adverse public health effects of ICSI.

Cytoskeletal dynamics during mammalian gametegenesis and fertilization: Implications for human reproduction

From gamete to neonate, human fertilization is a series of cell motilities (motion and morphological changes). Cytoskeletons play a role in cell motility as they work as a field worker in the cell. The present study is a review of dynamic motility of cytoskeletons (microfilaments and microtubules) during mammalian gamategenesis and fertilization. Dynamic and proper organization of cytoskeletons is crucial for the completion of oocyte maturation and spermatogenesis. By intracytoplasmic sperm injection, some difficulties in fertilization by sperm entry into the egg cytoplasm are overcome. However, the goal of fertilization is the union of the male and female genome, and sperm incorporation into an oocyte is nothing but the beginning of fertilization. Sperm centrosomal function, which introduces microtubule organization and promotes pronuclear apposition and first mitotic spindle formation, plays the leading role in the 'motility' of post-intracytoplasmic sperm injection events in fertilization. The present review introduces novel challenges in functional assessment of the human sperm centrosome. Furthermore, microtubule organization during development without the sperm centrosome (e.g. parthenogenesis) is mentioned. (Reprod Med Biol 2005; 4: 179-187).

Cloning and assisted reproductive techniques: Influence on early development and adult phenotype

Over the past 40 years, our increased understanding and development of cell and molecular biology has allowed even greater advances in reproductive biology. This is most evident by the development of various aspects of assisted reproductive techniques (ART), generation of transgenic animals, and most recently generation of mammals through somatic cell cloning. To date, cloning from adult somatic cells has been successful in at least 10 mammalian species. Although generating viable cloned mammals from adult cells is technically feasible and the list of successes will only continue to grow with time, prenatal and perinatal mortality is high and live cloned offspring have not been without health problems. The success of many of the proposed applications of the cloning technique obviously depends upon the health and survival of founder animals generated by nuclear transfer. This article summarizes the health consequences of cloning in mice, and discusses possible mechanisms through which these conditions may arise. In addition, we discuss the effects of ART in animal models and in humans. ART also involves some of the same procedures used in cloning, and there are reports that offspring generated by ART sometimes display aberrant phenotypes as well. It is important to point out that although these techniques do sometimes produce abnormalities, the majority of offspring are born apparently normal and survive to adulthood. Additionally, we must emphasize that the effects of ART and cloning observed in animal models do not necessarily indicate that they will occur in humans. In this article, we review studies examining the phenotype of animals generated by cloning and various ART, and discuss clinical implications of these findings.

Use of Mammalian Eggs for Assessment of Human Sperm Function: Molecular and Cellular Analyses of Fertilization by Intracytoplasmic Sperm Injection

PROBLEMS

Intracytoplasmic sperm injection (ICSI ) has been described as the 'cure' for male sterility because a single sperm can now be directly introduced into an egg with some chance of pregnancy. While ICSI has revolutionized the practice of assisted reproductive techniques (ART), there are few molecular and cellular studies about its safety and efficacy. Even by using ICSI, fertilization in humans succeeds only if the sperm effectively accomplishes a number of tasks including 'post-ICSI events' in fertilization. To assess the function of human sperm after ICSI, we used heterologous ICSI with human sperm into animal eggs. Egg activation, sperm decondensation and sperm centorosomal function were examined in sperm from fertile men and infertile patients.

METHODS

Sperm from fertile men and infertile patients were injected into hamster, rabbit and bovine eggs by Piezo micromanipulator, and studied in decondensation of sperm nuclei, egg activation and microtubule organization.

RESULTS

Decondensation human sperm head following ICSI into hamster eggs occurred initially form basal lesion, and apical portion of sperm nuclei which is surrounded by acrosome and perinuclear theca, still condensed in early pronuclear stage. Radial array of microtubules from sperm centrosome 'sperm aster' which is essential for pronuclear movement was observed in 30% rabbit eggs following ICSI with human sperm. By heterologous ICSI system with fertile human sperm and bovine eggs, 83.3% of eggs was activated and 60% eggs had sperm aster, indicating that bovine Piezo ICSI system is appropriate for assessing human sperm oocyte activation ability and human sperm centrosomal function. Oocyte activation and sperm centrosomal function were significantly low in sperm from men with globozoospermia and men with dysplasia of fibrous sheath.

CONCLUSION

These assays indicate differences of the process of fertilization between in vitro fertilization and ICSI, and reflect the human sperm function especially for the 'post-ICSI events' in fertilization. More molecular and cellular analyses in fertilization by ICSI are needed for improvement of ART.

Centrosomal function assessment in human sperm using heterologous ICSI with rabbit eggs: A new male factor infertility assay

Sperm centrosomal function was assessed by immunocytochemical analysis after the injection of human sperm into mature rabbit eggs. Three hours after intracytoplasmic sperm injection (ICSI), an astral microtubule array from the base of the human sperm was observed in the rabbit eggs. This sperm aster expanded in the egg cytoplasm, concomitant with pronuclear formation, and a dense microtubule array was organized at the time of pronuclear centration. Using fertile donor sperm, the sperm aster formation rate at 3 hr after ICSI was 35.0 +/- 1.5%. Using sperm from infertile patients, the average aster formation rate was lower (25.4 +/- 14.8%, P<0.05). Among infertile cases, there was no correlation between sperm aster formation rates and conventional parameters of semen analysis. However, the sperm aster formation rate correlated with the embryonic cleavage rate following human in vitro fertilization (IVF). These data suggest that this assay reflects sperm function during embryonic development after sperm entry and that reproductive success during the first cell cycle requires a functional sperm centrosome. Furthermore, sperm centrosomal function cannot be predicted from conventional parameters of semen analysis. We propose that insufficient centrosomal function could be the cause of certain cases of idiopathic infertility. These assays may lead to the discovery of new types of infertility, which have previously been treated as "unexplained infertility," and may also lead to the treatment of infertility incurable even by ICSI. Consequently, an accurate and relevant assay to help assure couples of the success of fertilization is warranted, perhaps prior to ICSI therapy.

Intracytoplasmic sperm injection: stiletto conception or a stab in the dark

To describe the importance of molecular and cellular analyses in intracytoplasmic sperm injection (ICSI) the authors review the literature on biological challenges in ICSI and associated techniques. Several matters can be proposed in molecular and cellular challenges in ICSI for safety and efficacy: (1) a reliable and convenient animal model for understanding the molecular and cellular basis of human ICSI must be established, and molecular and cellular analysis of the first cell cycle of human fertilization should be better understood; (2) a proper assay for human sperm function that contributes to the indication for ICSI should be developed; and (3) de novo and transmitted genetic security in ICSI should be examined.

Fate of sperm components during assisted reproduction: implications for infertility

Studies in non-human primates highlight their suitability as preclinical models for investigating assisted reproduction techniques. The cytoskeletal events of fertilization in non-human primates are similar to those in humans in that they require a paternally derived centrosome. The centrosome, introduced by the sperm at fertilization, organizes a microtubule array that is responsible for bringing the parental genomes together at first mitosis. Incomplete functioning of the sperm centrosome during fertilization has been identified as a novel form of infertility that would not necessarily benefit from intracytoplasmic sperm injection (ICSI). The global use of ICSI to overcome male infertility has been very successful, although concerns remain regarding the long-term effects on children born after ICSI. The cytoskeletal events that occur during ICSI are quite different from the events of in vitro fertilization: a sperm selected for ICSI does not undergo typical oocyte interactions, and abnormal remodelling of the male pronucleus may result. The implications of these findings are discussed in relation to the safety of the ICSI technique.

The use of primates as models for assisted reproduction

Evidence from donated human oocytes and embryos demonstrates that the spermatozoon contributes the 'centrosome', which is critical to fertilization, and that some cases of infertility in couples are related to defects in the pathways that reconstitute the zygotic centrosome. A greater understanding of these microtubule-mediated motility events that ensure normal sperm-oocyte interactions has been made easier by the use of non-human primate gametes. Our studies using rhesus monkey gametes have shown that the cytoskeletal events during fertilization by IVF and intracytoplasmic sperm injection (ICSI) are very similar to those of human fertilization, and that manipulations of non-human primate gametes may help to test the safety and improve current strategies for reproduction, as well as develop new techniques. ICSI results in abnormal nuclear remodelling, in part due to the persistence of VAMP (vesicle-associated membrane protein), the acrosome and the perinuclear theca on the sperm head, all of which are normally removed at, or close to, the oocyte cortex during natural and in-vitro fertilization. Progression through the first cell cycle in ICSI oocytes cannot be completed until these structures have been removed from the forming male pronucleus, demonstrating unique differences between ICSI and IVF. While ICSI is of enormous therapeutic value for the treatment of male infertility, fundamental research using clinically relevant animal models is only now unravelling the cellular and molecular events that permit fertilization by sperm microinjection.

Rhesus offspring produced by intracytoplasmic injection of testicular sperm and elongated spermatids

OBJECTIVE

To establish pregnancies in rhesus monkeys using testicular sperm and elongated spermatids injected into oocytes.

DESIGN

Comparative animal study.

SETTING

Regional Primate Research Center.

ANIMAL(S)

Prime, fertile rhesus monkeys.

INTERVENTION(S)

Oocytes collected by laparoscopy from gonadotropin-stimulated female rhesus monkeys were injected with testicular sperm or elongated spermatids obtained from the testis of males. Cleavage stage embryos were transferred to surrogate females.

MAIN OUTCOME MEASURE(S)

Fertilization, embryo cleavage, and the establishment of pregnancies. Fertilization failures were fixed and processed for the detection of microtubules and chromatin configurations.

RESULT(S)

Fertilization, assessed by the presence of two pronuclei within 15 hours after injection, was 60% for intracytoplasmic sperm injection with testicular sperm and 47% for elongated spermatid injection. Fertilized zygotes co-cultured in Connaughts Medical Research Labs (CMRL) medium on a Buffalo Rat Liver cell monolayer resulted in hatched blastocysts after testicular sperm extraction-intracytoplasmic sperm injection and elongated spermatids. Embryos transferred at the 4- to 8-cell stage gave rise to three pregnancies: 2/3 from testicular sperm and 1/1 from an elongated spermatid. Three healthy infants were delivered by cesarean. Oocytes that failed to fertilize typically remained arrested in metaphase of meiosis.

CONCLUSION(S)

Testicular sperm and elongated spermatids can be used for fertilization in the rhesus monkey resulting in live births.

Defective sperm decondensation: a cause for fertilization failure

The study aimed to evaluate the role of chromatin packaging (CMA3 staining), sperm morphology during sperm-zona binding, sperm decondensation and the presence of polar bodies in oocytes that failed in vitro fertilization (IVF). The percentage CMA3 staining categorized the data into three groups, < 44%, n = 10; > or = 44-59%, n = 10; and > or = 60%, n = 29. Morphology groups were < or = 4% (n = 11); > 4-14% (n = 19); and > 4% (n = 19). One hundred and seventy-two oocytes that failed IVF were evaluated for sperm-zona binding, ooplasma penetration and sperm decondensation. Odds ratio analyses indicated that being in the > or = 60% CMA3 staining group resulted in a 15.6 fold increase in the risk of decondensation failure, relative to CMA3, staining of < 44%. For morphology, there was a 2.17 fold decrease in the risk of fertilization failure in the morphology group with > 4-14% normal cells, while it increased 2.45 fold for the morphology group with < or = 4% normal cells. Using CMA3 fluorescence to discriminate, 51% of the oocytes in the group with elevated CMA3 fluorescence had no sperm in the ooplasma compared to 32% and 16% penetration failure in the CMA3 staining groups > or = 44-59% and < 44%, respectively. Sperm chromatin packaging quality and sperm morphology assessments are useful clinical indicators of human fertilization failure. Immunofluorescence techniques could be used to provide a clear diagnosis of failed fertilization.

Chromatin packaging as an indicator of human sperm dysfunction

PURPOSE

Understanding the causes of fertilization failure is an important research field in assisted reproductive programs. The present study aimed to evaluated the possible relationship between chromatin packaging quality (CMA3 staining) and (i) normal morphology and (ii) its ability to predict the functional integrity of spermatozoa in both in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) treatment programs.

METHODS

Semen of 140 men from IVF and ICSI couples were analyzed for sperm concentration, motility, morphology, and chromatin packaging (CMA3). For CMA3 classification, two cutoff values were used, namely, 44.5% +/- 13 and 1 SD above the mean, i.e., 57.5% (rounded off to 60%). IVF and ICSI data were stratified using three basic cutoff values for CMA3 staining, namely, < 44%, > 44-60%, and > 60%.

RESULTS

Based on CMA3 results patients were divided into four groups, namely, group A, < 44% CMA3 (n = 15, IVF); group B, > or = 44% and < 60% CMA3 (n = 39, IVF); group C, > or = 60% CMA3 (n = 45 IVF); and group D, > or = 60% CMA3 (n = 41 ICSI). During receiver operator characteristic analyses the estimated cutoff value for CMA3 staining, to distinguish between < 4% and > or = 4% morphology groups, was 60%. The area under the curve was 0.89, sensitivity of 75%, and specificity of 100%. When IVF rates of > 60% and < 60% were used, the optimal CMA3 value for prediction of fertilization success again was recorded at 60%. The area under the curve was 0.76, sensitivity of 81.5%, and specificity of 63.6%.

CONCLUSIONS

Chromatin packaging assessments should be included as a complementary assay to the sequential diagnostic approach of the male-factor patients.

Atypical decondensation of the sperm nucleus, delayed replication of the male genome, and sex chromosome positioning following intracytoplasmic human sperm injection (ICSI) into golden hamster eggs: does ICSI itself introduce chromosomal anomalies?

OBJECTIVE

To examine nuclear decondensation, positioning of sex chromosomes, and the S-phase in human sperm nuclei following intracytoplasmic sperm injection (ICSI) into hamster eggs.

DESIGN

Prospective analysis of hamster eggs and human sperm following ICSI.

SETTING

Division of Reproductive Sciences, Oregon Health Sciences University and Oregon Regional Primate Research Center.

PATIENT(S)

Fertile donor sperm from a commercial source.

INTERVENTION(S)

Human sperm were examined by immunofluorescence stain, bromodioxyuridine (BrdU) uptake assay and fluorescence in situ hybridization following ICSI into hamster eggs.

MAIN OUTCOME MEASURE(S)

Immunostaining and fluorescence in situ hybridization.

RESULT(S)

Decondensation of human sperm nuclei occurred initially in the basal region, and perinuclear theca of sperm persisted around the condensed apical region. In some sperm nuclei, following ICSI the sex chromosomes were in the apical region, remaining condensed for longer than in the basal region. S-phase entry of human sperm nuclei following ICSI was delayed compared to the zona-free hamster egg penetration assay.

CONCLUSION(S)

These results force questions about the mechanism of male pronuclear formation after ICSI and suggest new strategies for understanding the basis of chromosomal anomalies leading to birth defects as well as continuing improvements in the safety and efficacy of infertility therapies.

Sperm aster formation and pronuclear decondensation during rabbit fertilization and development of a functional assay for human sperm

Microtubule organization and chromatin configurations in rabbit eggs after in vivo rabbit fertilization and after intracytoplasmic injection with human sperm were characterized. In unfertilized eggs, an anastral barrel-shaped meiotic spindle, oriented radially to the cortex, was observed. After rabbit sperm incorporation, microtubules were organized into a radial aster from the sperm head, and cytoplasmic microtubules were organized around the male and female pronuclei. The microtubules extending from the decondensed sperm head participated in pronuclear migration, and organization around the female pronucleus may also be important for pronuclear centration. Support for these observations was found in parthenogenetically activated eggs, in which microtubule arrays were organized around the single female pronucleus that formed after artificial activation. These observations support a biparental centrosomal contribution during rabbit fertilization as opposed to a strictly paternal inheritance pattern suggested from previous studies. In rabbit eggs that received injected human donor sperm, an astral array of microtubules radiated from the sperm neck and enlarged as the sperm head underwent pronuclear decondensation. gamma-Tubulin was observed in the center of the sperm aster. We conclude that the rabbit egg exhibits a blended centrosomal contribution necessary for completion of fertilization and that the rabbit egg may be a novel animal model for assessing centrosomal function in human sperm and spermatogenic cells following intracytoplasmic injection.

Cellular and molecular events after in vitro fertilization and intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) has heralded an era of tremendous improvements in treating male infertility leading to the births of thousands of babies. However, recent concerns over possible long-term effects of ICSI on offspring has prompted the development of a preclinical, nonhuman primate model to assess the safety of ICSI. Fluorescent imaging of rhesus macaque IVF zygotes revealed that this species shares many similarities with humans in terms of cytoskeletal and chromatin dynamics during fertilization. However, rhesus monkey zygotes fertilized by ICSI resulted in abnormal nuclear remodeling leading to asynchronous chromatin decondensation in the apical region of the sperm head, delaying the onset of DNA synthesis. The persistence of the acrosome and perinuclear theca on the apex of sperm introduced into the oocyte by ICSI may constrict the DNA in this region. Despite these differences, normal rhesus monkey ICSI embryos have been produced and have lead to several births after transfer. The irregularities described in this paper raise concerns that the ICSI procedure may result in chromatin damage during DNA decondensation and further highlight the need for devising improved pre-clinical assessment prior to global acceptance of this, and other, novel methods of assisted reproduction.

Unique checkpoints during the first cell cycle of fertilization after intracytoplasmic sperm injection in rhesus monkeys

Intracytoplasmic sperm injection has begun an era of considerable improvements in treating male infertility. Despite its success, questions remain about the dangers of transmitting traits responsible for male infertility, sex and autosomal chromosome aberrations and possible mental, physical and reproductive abnormalities. We report here the first births of rhesus monkeys produced by intracytoplasmic sperm injection at rates greater or equal to those reported by clinics. Essential assumptions about this process are flawed, as shown by results with the preclinical, nonhuman primate model and with clinically discarded specimens. Dynamic imaging demonstrated the variable position of the second meiotic spindle in relation to the first polar body; consequently, microinjection targeting is imprecise and potentially lethal. Intracytoplasmic sperm injection resulted in abnormal sperm decondensation, with the unusual retention of vesicle-associated membrane protein and the perinuclear theca, and the exclusion of the nuclear mitotic apparatus from the decondensing sperm nuclear apex. Male pronuclear remodeling in the injected oocytes was required before replication of either parental genome, indicating a unique G1-to-S transition checkpoint during zygotic interphase (the first cell cycle). These irregularities indicate that the intracytoplasmic sperm injection itself might lead to the observed increased chromosome anomalies.