Sperm chromosome aneuploidy as related to male factor infertility and some ultrastructure defects

Detection of chromosome aberrations in 17 054 individuals with fertility problems and their subsequent assisted reproductive technology treatments in Central China

STUDY QUESTION

How do the types and frequency of chromosome aberrations in couples in central China affect fertility and ART treatment?

SUMMARY ANSWER

Men with chromosome aberrations or polymorphisms have an increased risk of semen quality impairment and infertility, and couples affected by reciprocal translocations had a lower pregnancy rate compared with other chromosome aberrations.

WHAT IS KNOWN ALREADY

Karyotyping is crucial for patients affected by infertility as chromosome aberrations play an important role in the etiology of male infertility. However, the influence of chromosome aberrations and polymorphisms on sperm motility and morphology remains controversial. Data on ART treatment outcomes in infertile couples affected by chromosome aberrations are insufficient.

STUDY DESIGN, SIZE, DURATION

We conducted a retrospective study involving 17 054 patients affected by infertility who underwent karyotyping in our center between January 2020 and May 2022.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Karyotyping was performed on 17 054 patients with reproductive failure. All patients were from the central regions of China. The following data were collected from a medical records system using patient identification numbers: couples' ages, history of pregnancy and childbirth, type of infertility, years of infertility, cause of infertility, chromosome karyotypes, semen analysis results, assisted reproductive techniques performed, and treatment outcomes of ART.

MAIN RESULTS AND THE ROLE OF CHANCE

The incidence of chromosome aberrations was 2.04%; 2.49% in men and 1.57% in women. By analyzing the relationships between chromosome aberrations/polymorphisms and abnormal semen parameters, we found that there were significantly higher rates of asthenozoospermia, oligospermia, and teratozoospermia among men with Robertsonian translocations and sex chromosomal structural aberrations compared with those with normal karyotypes. Higher rates of asthenozoospermia and teratozoospermia were also observed among men with autosomal reciprocal translocations. The incidence of chromosome aberrations in azoospermic men (13.75%), and in men with cryptozoospermia or severe oligospermia (6.97%) was significantly higher than that in men with mild oligospermia or normospermia (0.88-2.12%). In addition, we found that the progressive movement of sperm is impaired in men with Chromosome 21 polymorphisms compared with men with normal karyotypes (39.46% ± 20.51% vs 48.61% ± 18.76%, P = 0.026). The percentage of morphologically normal forms was lower in the chromosomal polymorphism group than in the normal karyotype group (5.01% ± 2.41% vs 5.59% ± 2.14%, P = 0.001), especially in men with polymorphisms on Chromosome 9 (enlarged Chromosome 9 heterochromatin [9qh+]: 4.48% ± 2.22% vs 5.59% ± 2.14%, P = 0.006; pericentric inversion of Chromosome 9 [inv(9)]: 5.09% ± 3.11% vs 5.59% ± 2.14%, P = 0.008). ART treatment was successful in 36.00% of couples affected by chromosome aberrations. However, couples affected by reciprocal translocations achieved a lower pregnancy rate (24.07%), which may be due to the lower euploidy rates (27.31%) when compared with that in other chromosome aberrations.

LIMITATIONS, REASONS FOR CAUTION

First, although the initial cohort was large, chromosome aberrations were identified in a small number of patients. Second, the observational nature of the study design is limiting. Third, the couples affected by infertility in this study were all outpatients that did not undergo identical comprehensive examinations except for karyotyping, leading to the incomplete collection of medical records. Also, the population included in this study mainly focused on couples affected by infertility, which may not be included in the European Association of Urology (EAU) recommendation on male infertility.

WIDER IMPLICATIONS OF THE FINDINGS

Men with chromosome aberrations or polymorphisms have an increased risk of semen quality impairment and infertility. Constitutional chromosome analysis is recommended for men affected by infertility and severe oligospermia or azoospermia to facilitate early and appropriate guidance for the most suitable treatment. Carriers of chromosome aberrations can achieve acceptable pregnancy outcomes through IVF. However, couples affected by reciprocal translocations have lower pregnancy rates, and more treatment cycles are needed before a successful pregnancy. A possible explanation may be the fewer euploid embryos obtained.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by Grant 2021YFC2700603 from the National Key Research & Development Program of China. The authors declare no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Sperm and Oocyte Chromosomal Abnormalities

Gametogenesis, the process of producing gametes, differs significantly between oocytes and sperm. Most oocytes have chromosomal aneuploidies, indicating that chromosomal aberrations in miscarried and newborn infants are of oocyte origin. Conversely, most structural anomalies are of sperm origin. A prolonged meiotic period caused by increasing female age is responsible for an increased number of chromosomal aberrations. Sperm chromosomes are difficult to analyze because they cannot be evaluated using somatic cell chromosome analysis methods. Nevertheless, researchers have developed methods for chromosome analysis of sperm using the fluorescence in situ hybridization method, hamster eggs, and mouse eggs, allowing for the cytogenetic evaluation of individual sperm. Reproductive medicine has allowed men with severe spermatogenic defects or chromosomal abnormalities to have children. However, using these techniques to achieve successful pregnancies results in higher rates of miscarriages and embryos with chromosomal abnormalities. This raises questions regarding which cases should undergo sperm chromosome analysis and how the results should be interpreted. Here, we reviewed clinical trials that have been reported on oocyte and sperm chromosome analyses. Examination of chromosomal abnormalities in gametes is critical in assisted reproductive technology. Therefore, it is necessary to continue to study the mechanism underlying gametic chromosomal abnormalities.

Globozoospermia: A Case Report and Systematic Review of Literature

PURPOSE

Globozoospermia is a genetic syndrome characterized by the presence of round-headed spermatozoa and infertility due to the inability of these spermatozoa to fertilize the oocyte. In this article, we present the clinical case of a young globozoospermic patient with a new, not yet described mutation of the DPY19L2 gene. We also performed a systematic review of the literature on gene mutations, the outcome of assisted reproductive techniques, and the risk of transmission of abnormalities to the offspring in patients with globozoospermia and made recommendations to offer a more appropriate clinical management of these patients.

MATERIALS AND METHODS

We performed a systematic search in the PubMed, Google Scholar, and Scopus databases from their inception to December 2021. The search strategy included the combination of the following Medical Subjects Headings (MeSH) terms and keywords: "globozoospermia", "round-headed spermatozoa", "round head spermatozoa", "intracytoplasmic sperm injection", "ICSI", "offspring", "child health", "assisted reproductive technique outcome". All the eligible studies were selected following the PECOS (Population, Exposure, Comparison/Comparator, Outcomes, Study design) model. The quality of included studies was assessed by applying the "Cambridge Quality Checklists".

RESULTS

The main genes involved in the pathogenesis of globozoospermia are DPY19L2, SPATA16, PICK1, GGN, SPACA1, ZPBP, CCDC62, and CCNB3 genes. Other genes could also play a role. These include C2CD6, C7orf61, CCIN, DNH17, DNH6, PIWIL4, and CHPT1. Globozoospermic patients should undergo ART to achieve fertility. In particular, intracytoplasmic sperm injection with assisted oocyte activation or intracytoplasmic morphologically-selected sperm injection appears to be associated with a higher success rate. Patients with globozoospermia should also be evaluated for the high rate of sperm aneuploidy which appears to influence the success rate of ART but does not appear to be associated with an increased risk of transmission of genetic abnormalities to offspring.

CONCLUSIONS

This systematic review summarizes the evidence on the gene panel to be evaluated, ICSI outcomes, and the health of the offspring in patients with globozoospermia. Evidence-based recommendations on the management of patients with globozoospermia are provided.

The impact of cryopreservation on the morphology of spermatozoa in men with oligoasthenoteratozoospermia

The cryopreservation of ejaculate can reduce the viability, motility, and morphological characteristics of the spermatozoa of infertile men. Oligoasthenoteratozoospermia (OAT) is the most common cause of male subfertility. The aim of this study was to evaluate the morphological characteristics and viability of progressive motile sperm fraction before and after cryopreservation, and to determine whether cryopreservation of progressive motile sperm fraction is effective in eliminating morphologically abnormal sperm in men with OAT. An increased proportion of spermatozoa with normal morphology in fresh progressive motile sperm fraction compared with fresh ejaculate has been observed. After cryopreservation, the motility was 65.5 ± 8.8%; the proportion of spermatozoa with normal morphology increased non-significantly compared with freshly prepared motile sperm fraction (35.6 ± 5.5%). Concurrently, the proportion of cryopreserved spermatozoa with head defects increased significantly by 1.7 times (to 38.4 ± 4.7%) and the proportion of almost all morphologically abnormal sperm cells, particularly spermatozoa with multiple abnormalities, was reduced significantly. These data appear to be a novel finding in the context of patients with OAT. Using such spermatozoa for in vitro fertilization leads to a significant decrease in both a number of embryos at the cleavage stage and the blastocysts formation rate. High-magnification sperm morphology examination and selection, IMSI, post-cryopreservation significantly increased the likelihood of successful oocyte fertilization and subsequent embryo development.

High rates of aneuploidy, mosaicism and abnormal morphokinetic development in cases with low sperm concentration

Purpose

The aim of our study was to evaluate the impact of severe male infertility (SMF) on the chromosomal status of embryos and any possible correlation between chromosomal status and embryo morphokinetics in younger women using data obtained from comprehensive preimplantation genetic tests.

Methods

The trial was conducted in an ART and Reproductive Genetics Centre between 2011 and 2018. A total of 326 cycles in cases with SMF where the female partner’s age was ≤ 35 years were evaluated. SMF is defined as sperm concentration below 5 mil/ml (million per milliliter) and divided into three subgroups according to sperm concentrations: 1–5 mil/ml, < 1mil/ml and testicular sperm. The control group of 190 cycles had normal sperm parameters.

Results

Significantly lower chromosomal euploidy rates were found in the testicular sperm group compared with the normal sperm controls when the female age was ≤ 35 years. In SMF, statistically significantly affected chromosomes were 2, 10, 11, 17, 21 and sex chromosomes. The mosaicism and abnormal morphokinetic development rates were higher in the SMF group than in control group, and this difference was significant when testicular sperm was used.

Conclusion

Lower euploidy rates, higher mosaicism rates and a higher incidence of abnormal morphokinetic development were observed in cases with testicular sperm with female partners ≤ 35 years compared with normal sperm controls. These findings suggest that PGT-A may be advisable in severe male infertility cases. Furthermore, the correlation between morphokinetics and chromosomal status was greatly reduced or absent in these most severe forms of male infertility, thus the need for new morphokinetic models.

Electronic supplementary material

The online version of this article (10.1007/s10815-019-01673-w) contains supplementary material, which is available to authorized users.

Impact of sperm genome decay on Day-3 embryo chromosomal abnormalities from advanced-maternal-age patients

Infertile male patients often exhibit unconventional semen parameters, including DNA fragmentation, chromatin dispersion, and aneuploidy-collectively referred to as sperm genome decay (SGD). We investigated the correlation of SGD to embryo chromosomal abnormalities and its effect on clinical pregnancy rates in patients with advanced maternal age (AMA) (>40 years) who were undergoing intracytoplasmic sperm injection-preimplantation genetic screening (ICSI-PGS). Three groups were assessed: patients with AMA and male partners with normal sperm (AMA-N); AMA patients and male partners presenting with SGD (AMA-SGD); and young fertile female patients and male partners with SGD (Y-SGD). We found a significant increase in embryonic chromosomal abnormalities-polyploidy, nullisomy, mosaicism, and chaotic anomaly rates-when semen parameters are altered (76% vs. 67% and 66% in AMA-SGD vs. AMA-N and Y-SGD groups, respectively). Statistical analysis showed a correlation between SGD and aneuploidies of embryonic chromosomes 13, 16, 21, X, and Y, as well as negative clinical outcomes. Incorporation of molecular sperm analyses should therefore significantly minimize the risk of transmission of chromosomal anomalies from spermatozoa to embryos, and may provide better predictors of pregnancy than conventional sperm analyses. We also demonstrated that an ICSI-PGS program should be implemented for SGD patients in order to limit transmission of chromosomal paternal anomalies and to improve clinical outcome.

Spermatozoa Production by Triploid Males in the New Zealand Freshwater Snail Potamopyrgus antipodarum

Asexual lineages derived from dioecious taxa are typically assumed to be all female. Even so, asexual females from a variety of animal taxa occasionally produce males. The existence of these males sets the stage for potential gene flow across asexual lineages as well as between sexual and asexual lineages. A recent study showed that asexual triploid female Potamopyrgus antipodarum, a New Zealand freshwater snail often used as a model to study sexual reproduction, occasionally produce triploid male offspring. Here, we show that these triploid male P. antipodarum 1) have testes that produce morphologically normal sperm, 2) make larger sperm cells that contain more nuclear DNA than the sperm produced by diploid sexual males, and 3) produce sperm that range in DNA content from haploid to diploid, and are often aneuploid. Analysis of meiotic chromosomes of triploid males showed that aberrant pairing during prophase I likely accounts for the high variation in DNA content among sperm. These results indicate that triploid male P. antipodarum produce sperm, but the extent to which these sperm are able to fertilize female ova remains unclear. Our results also suggest that the general assumption of sterility in triploid males should be more closely examined in other species in which such males are occasionally produced.

Telomere lengths in human pronuclei, oocytes and spermatozoa

Telomeres are chromosome ends that control functions related to cell division. Short telomeres are proposed to underlie infertility, female reproductive ageing and abnormal embryogenesis, but there is little direct evidence on telomere length in gametes and embryos. The aim of this study was to measure telomere lengths in individual human oocytes, spermatozoa, male and female pronuclei, in order to compare parental contributions to telomere lengths in the human zygote. Quantitative fluorescence in situ hybridization was used to measure average telomere length in pronuclei of oocytes fertilized for research using a known fertile sperm sample. Pronuclei derived from male and female gametes were distinguished by 5-methylcytosine staining. Results were compared with those for unfertilized mature and immature oocytes and individual spermatozoa decondensed in vitro. Fifty unselected men and one sperm donor provided semen samples and 32 women donated oocytes surplus to IVF treatment. Telomeres in mature oocytes and female pronuclei were significantly longer than those in individual spermatozoa and male pronuclei (P < 0.0001). Telomeres were longer in immature oocytes than in mature oocytes (P < 0.04). Sperm telomere length increased with male age (P < 0.05). Neither sperm nor oocyte telomere lengths were significantly associated with clinical parameters or outcome of treatment. In conclusion, telomere length measurements directly comparing human pronuclei under identical conditions show that male-derived telomeres are shorter on average than female-derived telomeres at fertilization. We propose that from this starting point, telomere lengths are probably modified by recombination events in the oocyte until telomerase increases at the blastocyst stage. Our findings do not support the use of gamete telomere lengths as a fertility diagnostic tool.

The use of fluorescent in situ hybridization in male infertility

Male factors are implicated in up to 50% of couples being evaluated and treated for infertility with advanced assisted reproductive technologies. Genetic abnormalities, including sperm chromosome aneuploidy as well as structural aberrations, are one of the major causes of infertility. The use of chromosome-specific DNA probes labeled with fluorochromes, particularly the combination with multiple probes, has been used to indirectly study the sperm chromosome by fluorescent in situ hybridization (FISH). Clinically, this technique is also used to assess the sperm of men recovering from gonadotoxic treatment. Recent advances in this technology facilitate the evaluation of sperm aneuploidy. Sperm FISH is a widely used screening tool to aid in counseling couples with severe male factor infertility, especially in cases of prior repeated in vitro fertilization/intracytoplasmic sperm injection failure or recurrent pregnancy loss. Automation of FISH imaging and analysis, as well as the development of emerging techniques such as comparative genomic hybridization, will all contribute to the promise of future diagnostic approaches aimed at improving the quality, ease, and efficiency of aneuploidy analysis.

Aneuploid sperm formation in rainbow trout exposed to the environmental estrogen 17{alpha}-ethynylestradiol

Environmental contaminants that mimic native estrogens (i.e., environmental estrogens) are known to significantly impact a wide range of vertebrate species and have been implicated as a source for increasing human male reproductive deficiencies and diseases. Despite the widespread occurrence of environmental estrogens and recognized detrimental effects on male vertebrate reproduction, no specific mechanism has been determined indicating how reduced fertility and/or fecundity is achieved. Previous studies show that male rainbow trout, Oncorhynchus mykiss, exposed to the environmental estrogen 17alpha-ethynylestradiol (EE2) before gamete formation and fertilization produce progeny with significantly reduced embryonic survival. To determine whether this observed decrease results from sperm chromosome alterations during spermatogenesis, male rainbow trout were exposed to 10 ng of EE2/l for 50 days. After exposure, semen was collected and sperm aneuploidy levels analyzed with two chromosome markers by fluorescent in situ hybridization. In vitro fertilizations were also conducted by using control and exposed sperm crossed to eggs from an unexposed female for offspring analysis. Evaluations for nucleolar organizer region number and karyotype were performed on developing embryos to determine whether sperm aneuploidy translated into embryonic aneuploidy. Results conclusively show increased aneuploid sperm formation due to EE2 exposure. Additionally, embryonic cells from propagated progeny of individuals possessing elevated sperm aneuploidy display high levels of embryonic aneuploidy. This study concludes that EE2 exposure in sexually developing male rainbow trout increases levels of aneuploid sperm, providing a mechanism for decreased embryonic survival and ultimately diminished reproductive success in EE2 exposed males.

Proteins involved in meiotic recombination: a role in male infertility?

Meiotic recombination results in the formation of crossovers, by which genetic information is exchanged between homologous chromosomes during prophase I of meiosis. Recombination is a complex process involving many proteins. Alterations in the genes involved in recombination may result in infertility. Molecular studies have improved our understanding of the roles and mechanisms of the proteins and protein complexes involved in recombination, some of which have function in mitotic cells as well as meiotic cells. Human gene sequencing studies have been performed for some of these genes and have provided further information on the phenotypes observed in some infertile individuals. However, further studies are needed to help elucidate the particular role(s) of a given protein and to increase our understanding of these protein systems. This review will focus on our current understanding of proteins involved in meiotic recombination from a genomic perspective, summarizing our current understanding of known mutations and single nucleotide polymorphisms that may affect male fertility by altering meiotic recombination.

Ultrastructural nuclear defects and increased chromosome aneuploidies in spermatozoa with elongated heads

BACKGROUND

Cellular and molecular mechanisms leading to elongated sperm heads are not known. We have analysed the nuclear status of spermatozoa with elongated heads.

METHODS

Fourteen men with at least 30% of spermatozoa with an elongated nucleus were studied and compared with five fertile men as controls. Sperm morphology was analysed by a quantitative ultrastructural analysis. Sperm chromosomal content was assessed by three-colour fluorescence in-situ hybridization (chromosomes X, Y, 18). Y chromosome microdeletion and karyotype were analysed.

RESULTS

Elongated sperm head rates of the patients were 46.9% (30-75 versus 0-2% in the control group) by light microscopy and 34.4% by electron microscopy. In all patients, the chromatin was poorly condensed in elongated sperm heads (50% of elongated nuclei). No anomalies of sperm biochemical markers were found. All the men showed normal karyotype (46,XY) and absence of Y chromosome microdeletion. Aneuploidy rates of gonosomes and chromosome 18 were significantly increased in patients (1.64- and 3.6-fold, P = 0.006 and 0.026, respectively).

CONCLUSIONS

This study demonstrates that impaired chromatin compaction and slightly increased chromosome aneuploidies are found in spermatozoa with an elongated head, suggesting possible mechanisms such as meiotic non-disjunctions or spermiogenesis anomalies.

Sperm morphology and aneuploidies: defects of supposed genetic origin

As individuals with genetic sperm defects are intracytoplasmic sperm injection candidates, the study of the chromosomal constitution of their spermatozoa is of great interest. This study is a review of the current literature concerning fluorescence in situ hybridisation studies in spermatozoa with genetic sperm defect as 'round head', 'dysplasia of fibrous sheath' (DFS), 'primary ciliary dyskinesia' (PCD), the 'detached tail' and the 'absence of fibrous sheath'. Regarding sperm head defects, elevated XY disomy and diplodies were detected. Genetic defects affecting the sperm tail seemed to have a different correlation with chromosome meiotic segregation. Only chromosome 18, among the autosomes, was studied and the percentage of frequency of disomy was generally within the normal range. In the more frequently studied defect, DFS, the alterations in gonosome disomy and diploidy were recorded by different groups. Regarding PCD defects, elevated frequencies of disomy of sex chromosomes and diploidy were observed, whereas the absence of the fibrous sheath and the detached tail did not show any meiotic disturbance. The problem of genetic sperm defects should be seriously considered when these sperm are used for assisted reproduction, owing to the high risk of transmission of chromosomal imbalance and of mutations that could cause genetic sperm defects in offspring.

Morphology assessment and fluorescence in situ hybridization of the same spermatozoon using a computerized cell-scanning system

BACKGROUND

Poor sperm morphology is statistically associated with an increase in the incidence of chromosome abnormalities. Our aim was to examine the possible correlation between chromosomal aberrations and sperm morphology in the same cell.

METHODS

12349 spermatozoa from 7 teratozoospermic and one globozoospermic patients, and from 3 fertile donors were analyzed using a system which scans for cell morphology and chromosomal ploidy in the same cell using digital technology.

RESULTS

Chromosomal aberrations were detected in 5.3% of teratozoospermic cases and in 6.7% in the globozoospermic patient compared with 1.6% in donors (P < 0.0001). Chromosomal aberrations were more common in abnormally formed sperm compared with normal spermatozoa: 4.5% vs 1.3% in the teratozoospermic group and 2.0% vs 0.3% in the control group (NS), especially frequent among sperm with two heads or two tails (52.1-77.2%) or extreme head deformations (10.6-11.1%) irrespective of grouping, and in mild amorphous heads in the globozoospermic patients (20.2%). The frequency of chromosomal aberrations in morphologically normal sperm was comparable whether derived from teratozoospermic or normospermic patients.

CONCLUSIONS

The computerized cell-scanning system demonstrated the relationship between chromosomal aberrations and sperm morphology in the same spermatozoon. The incidence of chromosomal aberrations was positively linked to abnormal sperm morphology, the more severe the abnormality, the higher the incidence of aneuploidy.

The effect of epigenetic sperm abnormalities on early embryogenesis

Sperm are a highly specialized cell type derived to deliver the paternal haploid genome to the oocyte. The epigenetic, or gene regulatory, properties and mechanisms of the sperm assist in preparation of the paternal genome to contribute to embryogenesis and the genome of the zygote. Many recent studies have addressed the issue of altered epigenetic processes in the sperm. This review evaluates the current understanding of DNA damage, chromosome aneuploidy, reduced telomere length, malformations of the centrosome, genomic imprinting errors, altered mRNA profiles, and abnormal nuclear packaging in the sperm prior to fertilization and the observed effects on embryogenesis. Attention has also been given to understanding the underlying etiology of sperm with altered epigenetic mechanisms in humans.

Does the presence of nuclear vacuoles in human sperm selected for ICSI affect pregnancy outcome?

BACKGROUND

To verify whether or not microinjection of sperm with a normal nuclear shape but large vacuoles affects IVF-ICSI pregnancy outcome.

METHODS

A comparative study testing IVF outcome parameters of IVF-ICSI, based on morphological selection of spermatozoa with normal nuclei against those based on microinjection of sperm with a normal nuclear shape but large vacuoles. An experimental group, including 28 IVF-ICSI cycles, where only embryos obtained from microinjection of spermatozoa with a normal nuclear shape but large vacuoles were transferred, was matched with a control group, including 28 IVF-ICSI cycles, where only embryos obtained from microinjection of spermatozoa with a strictly defined morphologically normal nuclear shape and content were transferred. The main outcome was IVF-ICSI pregnancy rate.

RESULTS

The experimental group exhibited a significantly lower pregnancy rate per cycle and significantly higher abortion rate per pregnancy compared to the control group (18 versus 50%, and 80 versus 7%, respectively, P=0.01).

CONCLUSION

Microinjection of vacuolated sperm appears to reduce the pregnancy rate and appears to be associated with early abortion.

How to improve IVF–ICSI outcome by sperm selection

In previous studies, a new IVF method of intracytoplasmic morphologically selected sperm injection (IMSI) was introduced, based on motile sperm organellar morphology examination (MSOME). It was concluded that microinjection of morphologically selected sperm cells with strictly normal nucleus, defined by MSOME, improves IVF-ICSI outcome. The aim of the present study was to confirm this conclusion in new, enlarged study groups. Comparison between 80 couples, who underwent an IVF-IMSI trial, with matched couples, who underwent a standard IVF-ICSI procedure, confirmed that pregnancy rate following IVF-IMSI was significantly higher, and abortion rate significantly lower than in the routine IVF-ICSI (60.0 versus 25.0%, and 14 versus 40% respectively, P <or= 0.05). Another comparison was performed between matched IMSI groups, where embryos were obtained from microinjection by spermatozoa with a morphologically normal nucleus ('best' group, n = 70) and a 'second best' group was selected, where embryos were obtained from microinjection of spermatozoa with minimal morphological impairment, since no other sperm cells were available. It was confirmed that microinjection by 'second best ' spermatozoa result in significantly lower pregnancy and delivery rates and significantly higher abortion rates than microinjection with 'best' spermatozoa (25.7 versus 58.2%, P <or= 0.01; 17.1 versus 52.8%, P <or= 0.01, and 33.3 versus 9.7%, P <or= 0.02 respectively). The present study has strengthened previous conclusions.

Comparison of the sperm aneuploidy rate in severe oligozoospermic and oligozoospermic men and its relation to intracytoplasmic sperm injection outcome

OBJECTIVE

To determine the incidence of disomy and diploidy for chromosomes 18, X, and Y in the sperm samples of severe oligozoospermic (<5 x 10(6) spermatozoa/mL) and oligozoospermic (5-20 x 10(6) spermatozoa/mL) men undergoing intracytoplasmic sperm injection (ICSI) and to evaluate the influence of sperm aneuploidy on pregnancy outcome.

DESIGN

Prospective study.

SETTING

Infertility clinic and genetic laboratory.

PATIENT(S)

Fifteen patients with severe oligozoospermia, 15 patients with oligozoospermia, and 10 normal fertile donors.

INTERVENTION(S)

Fluorescence in-situ hybridization (FISH) performed on sperm samples.

MAIN OUTCOME MEASURE(S)

The frequency of disomy and diploidy for chromosomes 18, X, and Y was analyzed using FISH, and the clinical outcome after ICSI was correlated.

RESULT(S)

Significantly greater frequencies of XY, YY disomy and diploidy were observed in severe oligozoospermic men compared with oligozoospermic and normozoospermic men. Although the fertilization rate was similar, the pregnancy rate was higher in the group with oligozoospermia versus severe oligozoospermia.

CONCLUSION(S)

This study demonstrated the presence of an elevated sperm aneuploidy rate in patients with low semen quality. Additionally, the data show a negative influence of sperm chromosome abnormalities on ICSI outcome.

Spermatozoal nuclear determinants of reproductive outcome: implications for ART

A male factor is implicated in more than 50% of couples treated with IVF. However, neither the routine testing of male fertility potential nor its treatment address the specific mechanisms by which spermatozoal factors may impact upon reproductive outcome. An important function of spermatozoa is to deliver the paternal genome to the oocyte. Recently, a number of acquired spermatozoal nuclear factors that may have implications on reproductive outcome have been described. These include non-specific DNA strand breaks, numerical abnormalities in spermatozoal chromosome content, Y chromosome microdeletions and alterations in the epigenetic regulation of paternal genome. The exact mechanisms by which these factors affect reproduction are unknown and their implications for assisted reproduction technology outcome need to be further investigated. These recent findings point to the need for novel and more personalized approaches to test and treat male factor infertility.