Analysis of sperm function in globozoospermia: implications for the mechanism of sperm-zona interaction

The use of ICSI in ART: evidence for practice

This article reviews the evidence regarding the safety and efficacy of intra-cytoplasmic sperm injection (ICSI). It provides evidence-based clinical and laboratory guidelines and recommendations for use of ICSI within an assisted reproductive technology (ART) service. The guidelines address the evidence for the use of ICSI rather than conventional IVF (cIVF); the use of ART techniques supplementary to ICSI; and risks associated with ICSI. This article is not intended to be the only approved standard of practice or to dictate an exclusive course of treatment. Other plans of management may be appropriate, taking into account the needs and medical history of the patient, available resources, and institutional or clinical practice limitations.

Human globozoospermia-related genes and their role in acrosome biogenesis

The mammalian acrosome is a secretory vesicle attached to the sperm nucleus whose fusion with the overlying plasma membrane is required to achieve fertilization. Acrosome biogenesis starts during meiosis, but it lasts through the entire process of haploid cell differentiation (spermiogenesis). Acrosome biogenesis is a stepwise process that involves membrane traffic from the Golgi apparatus, but it also seems that the lysosome/endosome system participates in this process. Defective sperm head morphology is accompanied by defective acrosome shape and function, and patients with these characteristics are infertile or subfertile. The most extreme case of acrosome biogenesis failure is globozoospermia syndrome, which is primarily characterized by the presence of round-headed spermatozoa without acrosomes with cytoskeleton defects around the nucleus and infertility. Several genes participating in acrosome biogenesis have been uncovered using genetic deletions in mice, but only a few of them have been found to be deleted or modified in patients with globozoospermia. Understanding acrosome biogenesis is crucial to uncovering the molecular basis of male infertility and developing new diagnostic tools and assisted reproductive technologies that may help infertile patients through more effective treatment techniques. This article is categorized under: Reproductive System Diseases > Environmental Factors Infectious Diseases > Stem Cells and Development Reproductive System Diseases > Molecular and Cellular Physiology.

The stallion sperm acrosome: Considerations from a research and clinical perspective

During the fertilization process, the interaction between the sperm and the oocyte is mediated by a process known as acrosomal exocytosis (AE). Although the role of the sperm acrosome on fertilization has been studied extensively over the last 70 years, little is known about the molecular mechanisms that govern acrosomal function, particularly in species other than mice or humans. Even though subfertility due to acrosomal dysfunction is less common in large animals than in humans, the evaluation of sperm acrosomal function should be considered not only as a complementary but a routine test when individuals are selected for breeding potential. This certainly holds true for stallions, which might display lower levels of fertility in the face of "acceptable" sperm quality parameters determined by conventional sperm assays. Nowadays, the use of high throughput technologies such as flow cytometry or mass spectrometry-based proteomic analysis is commonplace in the research arena. Such techniques can also be implemented in clinical scenarios of males with "idiopathic" subfertility. The current review focuses on the sperm acrosome, with particular emphasis on the stallion. We aim to describe the physiological events that lead to the acrosome formation within the testis, the role of very specific acrosomal proteins during AE, the methods to study the occurrence of AE under in vitro conditions, and the potential use of molecular biology techniques to discover new markers of acrosomal function and subfertility associated with acrosomal dysfunction in stallions.

Molecular characterization, dynamic transcription, and potential function of KIF3A/KIF3B during spermiogenesis in Opsariichthys bidens

Spermiogenesis is the final phase of spermatogenesis, wherein the spermatids differentiate into mature spermatozoa via complex morphological transformation. In this process, kinesin plays an important role. Here, we observed the morphological transformation of spermatids and analyzed the characterization, dynamic transcription, and potential function of kinesin KIF3A/KIF3B during spermiogenesis in Chinese hook snout carp (Opsariichthys bidens). We found that the full-length cDNAs of O. bidens kif3a and kif3b were 2544 and 2806 bp in length comprising 119 bp and 259 bp 5' untranslated region (UTR), 313 bp and 222 bp 3' UTR, and 2112 bp and 2325 bp open reading frame encoding 703 and 774 amino acids, respectively. Ob-KIF3A/KIF3B proteins have three domains, namely N-terminal head, coiled-coil stalk, and C-terminal tail, and exhibit high similarity with homologous proteins in vertebrates and invertebrates. Ob-kif3a/kif3b mRNAs were ubiquitously expressed in all tissues examined, with the highest expression in the brain and stage-IV testis. Immunofluorescence results showed that Ob-KIF3A was co-localized with tubulin and the mitochondria. Particularly, in early spermatids, Ob-KIF3A, tubulin, and the mitochondrial signals were evenly distributed in the cytoplasm, whereas in middle spermatids, they were distributed around the nucleus. In the late stage, the signals were concentrated on one side of the nucleus, where the tail is formed, whereas in mature sperms, they were detected in the midpiece and flagellum. These results indicate that Ob-KIF3A/KIF3B may participate in nuclear reshaping, flagellum formation, and mitochondrial aggregation in the midpiece during spermiogenesis.

Programmed Cell Death 2-Like (Pdcd2l) Is Required for Mouse Embryonic Development

Globozoospermia is a rare form of male infertility where men produce round-headed sperm that are incapable of fertilizing an oocyte naturally. In a previous study where we undertook a whole exome screen to define novel genetic causes of globozoospermia, we identified homozygous mutations in the gene PDCD2L. Two brothers carried a p.(Leu225Val) variant predicted to introduce a novel splice donor site, thus presenting PDCD2L as a potential regulator of male fertility. In this study, we generated a Pdcd2l knockout mouse to test its role in male fertility. Contrary to the phenotype predicted from its testis-enriched expression pattern, Pdcd2l null mice died during embryogenesis. Specifically, we identified that Pdcd2l is essential for post-implantation embryonic development. Pdcd2l^−/− embryos were resorbed at embryonic days 12.5-17.5 and no knockout pups were born, while adult heterozygous Pdcd2l males had comparable fertility to wildtype males. To specifically investigate the role of PDCD2L in germ cells, we employed Drosophila melanogaster as a model system. Consistent with the mouse data, global knockdown of trus, the fly ortholog of PDCD2L, resulted in lethality in flies at the third instar larval stage. However, germ cell-specific knockdown with two germ cell drivers did not affect male fertility. Collectively, these data suggest that PDCD2L is not essential for male fertility. By contrast, our results demonstrate an evolutionarily conserved role of PDCD2L in development.

The Male Is Significantly Implicated as the Cause of Unexplained Infertility

Male infertility is recognized as a relatively common, complex condition, generated by a broad array of environmental and genetic factors. Historical reliance on the conventional semen profile has tended to underestimate the true contribution of "the male factor" to human infertility. This review highlights the importance of genetic and epigenetic factors in the etiology of male infertility, identifying a range of mutations responsible for primary testicular failure and impaired fertilizing potential. More than three quarters of all de novo mutations arise in the male germline via mechanisms that involve the inefficient or defective repair of DNA damage. Understanding the range of factors capable of creating genetic turmoil in the paternal germline is essential, if we are to gain a deep understanding of the causes of male infertility, rather than just the symptoms that characterize its presence. High levels of DNA fragmentation induced by oxidative stress are part of this equation. Oxidative stress is, in turn, driven by biological (age, ejaculation frequency, varicocele, infection), lifestyle (smoking, obesity), and environmental factors (heat, other forms of electromagnetic radiation, and toxins) that can impair the fertilizing potential of the spermatozoa and influence the incidence of spontaneous mutations that may cause infertility in the offspring.

Disruption in ACTL7A causes acrosomal ultrastructural defects in human and mouse sperm as a novel male factor inducing early embryonic arrest

Early embryonic arrest is a challenge for in vitro fertilization (IVF). No genetic factors were previously revealed in the sperm-derived arrest of embryonic development. Here, we reported two infertile brothers presenting normal in conventional semen analysis, but both couples had no embryos for transfer after several IVF and intracytoplasmic sperm injection (ICSI). Whole-exome sequencing identified a homozygous missense mutation of ACTL7A in both brothers. This mutation is deleterious and causes sperm acrosomal ultrastructural defects. The Actl7a knock-in mouse model was generated, and male mutated mice showed sperm acrosomal defects, which were completely consistent with the observations in patients. Furthermore, the sperm from ACTL7A/Actl7a-mutated men and mice showed reduced expression and abnormal localization of PLCζ as a potential cause of embryonic arrest and failure of fertilization. Artificial oocyte activation could successfully overcome the Actl7a-mutated sperm-derived infertility, which is meaningful in the future practice of IVF/ICSI for the ACTL7A-associated male infertility.

The Role of Genetics and Oxidative Stress in the Etiology of Male Infertility-A Unifying Hypothesis?

Despite the high prevalence of male infertility, very little is known about its etiology. In recent years however, advances in gene sequencing technology have enabled us to identify a large number of rare single point mutations responsible for impeding all aspects of male reproduction from its embryonic origins, through the endocrine regulation of spermatogenesis to germ cell differentiation and sperm function. Such monogenic mutations aside, the most common genetic causes of male infertility are aneuploidies such as Klinefelter syndrome and Y-chromosome mutations which together account for around 20-25% of all cases of non-obstructive azoospermia. Oxidative stress has also emerged as a major cause of male fertility with at least 40% of patients exhibiting some evidence of redox attack, resulting in high levels of lipid peroxidation and oxidative DNA damage in the form of 8-hydroxy-2'-deoxyguanosine (8OHdG). The latter is highly mutagenic and may contribute to de novo mutations in our species, 75% of which are known to occur in the male germ line. An examination of 8OHdG lesions in the human sperm genome has revealed ~9,000 genomic regions vulnerable to oxidative attack in spermatozoa. While these oxidized bases are generally spread widely across the genome, a particular region on chromosome 15 appears to be a hot spot for oxidative attack. This locus maps to a genetic location which has linkages to male infertility, cancer, imprinting disorders and a variety of behavioral conditions (autism, bipolar disease, spontaneous schizophrenia) which have been linked to the age of the father at the moment of conception. We present a hypothesis whereby a number of environmental, lifestyle and clinical factors conspire to induce oxidative DNA damage in the male germ line which then triggers the formation de novo mutations which can have a major impact on the health of the offspring including their subsequent fertility.

DNA variants are an unlikely explanation for the changing quality of spermatozoa within the same individual

It has recently been suggested that the human sperm genome is highly unstable, which may be a reasonable explanation as to why men, even fertile men, produce defective spermatozoa. Furthermore, an unstable genome may also explain why the semen profile of the same man changes from one ejaculate to the next. As such, we took multiple ejaculates (between 3 and 6) from 7 individuals over a 6-month period and isolated sperm through density gradients. We then compared the DNA of: (i) good and poor-quality spermatozoa within the same ejaculate; and (ii) from multiple ejaculates from the same individual. Our results suggest that on a global level, DNA present within spermatozoa is actually quite stable and similar between both good and poor sperm. This is important information for the assisted reproductive community when it comes to sperm selection.

A successful healthy childbirth and an ongoing evolutive pregnancy in a case of partial globozoospermia by hyaluronic acid sperm selection

We here report a successful healthy childbirth and an ongoing evolutive pregnancy in a case of partial globozoospermia after selection of mature spermatozoa bound to hyaluronic acid (HA). The couple underwent two in vitro fertilisation (IVF) cycles. In the first attempt, 14 MII oocytes were retrieved. Randomly, seven oocytes were injected by conventional PVP-ICSI and seven by HA-ICSI. Fertilised oocytes were 2/7 and 4/7 after PVP-ICSI and HA-ICSI respectively. Transfer of two grade A embryos from HA-ICSI lead to birth of a healthy baby. The surplus embryo of the HA-ICSI group was vitrified at blastocyst stage. The two embryos from PVP-ICSI arrested their development. Two years after the childbirth, the vitrified blastocyst was transferred into the uterus, but implant failed. In the second cycle, 14 MII oocytes were retrieved and they were injected by HA-ICSI. Fertilised oocytes were 10 out of 14 injected oocytes. On day 5, two blastocysts were transferred into uterus and a single evolutive pregnancy is ongoing. On day 6, one blastocyst was vitrified. The remaining surplus embryos arrested their development. A healthy childbirth and an ongoing evolutive pregnancy in two consecutive ICSI attempts of the same couple suggest that HA sperm selection might assist in cases with partial globozoospermia.

Association between total globozoospermia and sperm chromatin defects

Globozoospermia is a severe sperm morphological anomaly leading to primary infertility and low fertilisation following intracytoplasmic sperm injection (ICSI). This phenotype is observed in less than 0.1% of infertile men and is determined by small, round-headed spermatozoa with absence of an acrosomal cap, acrosome protease and also cytoskeletal proteins. Failure of oocyte activation is considered as the main cause of fertilisation failure in these individuals post-ICSI. Therefore, artificial oocyte activation (AOA) along with ICSI is commonly implemented. However, based on previous report, fertilisation rate remains low despite implementation of ICSI-AOA. Therefore, other mechanisms like sperm chromatin packaging and DNA fragmentation may account for low fertilisation and development post-ICSI-AOA. Therefore, this study aims to assess and compare the degree of sperm protamine deficiency and DNA fragmentation in large population of infertile men with total globozoospermia (30 globozoospermic men presenting with 100% round-headed spermatozoa) with 22 fertile individuals using chromomycin A3 and TUNEL assay respectively. Results clearly show that mean of sperm concentration and percentage of sperm motility were significantly lower, while percentage of sperm abnormal morphology, protamine-deficient and DNA-fragmented spermatozoa were significantly higher in infertile men with globozoospermia compared to fertile men. Therefore, increased sperm DNA damage in globozoospermia is likely related to defective DNA compaction and antioxidant therapy before ICSI-AOA could be recommended as an appropriate option before ICSI-AOA.

Genetic aspects of monomorphic teratozoospermia: a review

Teratozoospermia is characterized by the presence of spermatozoa with abnormal morphology over 85 % in sperm. When all the spermatozoa display a unique abnormality, teratozoospermia is said to be monomorphic. Two forms of monomorphic teratozoospermia, representing less than 1 % of male infertility, are recognized: macrozoospermia (also called macrocephalic sperm head syndrome) and globozoospermia (also called round-headed sperm syndrome). Macrozoospermia is defined as the presence of a very high percentage of spermatozoa with enlarged head and multiple flagella. Meiotic segregation studies in 30 males revealed that over 90 % of spermatozoa were aneuploid, mainly diploid. Sperm DNA fragmentation studies performed in a few patients showed an increase in DNA fragmentation index compared to fertile men. Four mutations in the AURKC gene, a key player in meiosis and more particularly in spermatogenesis, have been found to be responsible for macrozoospermia. Globozoospermia is characterized by round-headed spermatozoa with an absent acrosome, an aberrant nuclear membrane and midpiece defects. The rate of aneuploidy of various chromosomes in spermatozoa from 26 globozoospermic men was slightly increased compared to fertile men. However, this increase was of the same order as that commonly found in infertile men with altered sperm parameters. The majority of the studies found that globozoospermic males had a sperm DNA fragmentation index higher than in fertile men. Mutations or deletions in three genes, SPATA16, PICK1 and DPY19L2, have been shown to be responsible for globozoospermia. Identification of the genetic causes of macrozoospermia and globozoospermia should help refine diagnosis and treatment of these patients, avoiding long and painful treatments. Elucidating the molecular causes of these defects is of utmost importance as intracytoplasmic sperm injection (ICSI) is very disappointing in these two pathologies.

Pig Spermatozoa Defect in Acrosome Formation Caused Poor Motion Parameters and Fertilization Failure through Artificial Insemination and In vitro Fertilization

The selection of morphologically normal spermatozoa is critical to obtain high breeding performances in boar breeding farms and artificial insemination (AI) centers. Parameters for the selection of semen mainly include total sperm motility, concentration, and morphology. However, these primary parameters are often not reliable for discriminating between normal and abnormal, non-fertilizable spermatozoa. The present study was designed to compare the motion characteristics, fertilization ability using in vitro fertilization (IVF), and acrosome formation of the semen from boars having low (boar number 2012) and normal (boar number 2004 and 2023) breeding performances. The ultimate goal was to identify additional simple and easy criteria for the selection of normal sperm. There was no significant difference between boar 2004 and boar 2023 sperm total motility in computer assisted sperm analysis. However, boar number 2012 semen presented a significantly reduced population of rapid moving spermatozoa and an increased population of slow moving spermatozoa compared to boar numbers 2004 and 2023. Analysis of detailed motion characteristics revealed that sperm from boar number 2012 had significantly reduced motility in progressiveness, average path velocity, straight-line velocity (VSL), curvilinear velocity (VCL), straightness, and linearity. The assessment of the fertilizing ability by IVF also showed that sperm from boar number 2012 showed a fertility rate of 3.4%, whereas sperm from boar number 2023 had a fertility rate of 75.45%. Interestingly, most of the sperm nuclei were found on the peripheral area of the oocytes, suggesting that the sperm from boar number 2012 lacked penetration ability into the oocyte zonapellucida. The acrosome formation analysis using Pisum sativum agglutinin staining demonstrated that the sperm from boar number 2012 had a defect in acrosome formation. Consequently, primary parameters for selecting semen before AI such as motility are not sufficient to select normal and fertilizable spermatozoa. In conclusion, the present study suggests that the acrosome staining and detailed motion characteristics such as progressiveness, VCL, and VSL should be included in determining semen quality together with primary parameters for successful AI and high breeding performance in the swine industry.

Understanding fertilization through intracytoplasmic sperm injection (ICSI)

Since the establishment of in vitro fertilization, it became evident that almost half of the couples failed to achieve fertilization and this phenomenon was attributed to a male gamete dysfunction. The adoption of assisted fertilization techniques particularly ICSI has been able to alleviate male factor infertility by granting the consistent ability of a viable spermatozoon to activate an oocyte. Single sperm injection, by pinpointing the beginning of fertilization, has been an invaluable tool in clarifying the different aspects of early fertilization and syngamy. However, even with ICSI some couples fail to fertilize due to ooplasmic dysmaturity in relation to the achieved nuclear maturation marked by the extrusion of the first polar body. More uncommon are cases where the spermatozoa partially or completely lack the specific oocyte activating factor. In this work, we review the most relevant aspects of fertilization and its failure through assisted reproductive technologies. Attempts at diagnosing and treating clinical fertilization failure are described.

Apport de l’exploration cytogénétique et ultrastructurale dans le pronostic de fertilité des sujets globozoospermiques

La globozoospermie est une forme sévère de tératozoospermie caractérisée par des spermatozoïdes à tête ronde avec absence ou présence d’un acrosome rudimentaire. L’objectif de cette étude est d’analyser les spermatozoïdes de six patients présentant un syndrome de globozoospermie et de rendre compte de l’inefficacité de plusieurs tentatives de fécondation in vitro avec ICSI. L’exploration de ces sujets a été réalisée par l’étude du taux d’aneuploïdies spermatiques par hybridation in situ fluorescente (sperm-FISH) pour les chromosomes X, Y et 18, du taux de fragmentation d’ADN par la technique TUNEL ainsi que par l’étude ultrastructurale détaillée de la morphologie spermatique en utilisant la microscopie électronique à transmission (MET). Onze tentatives d’ICSI ont été réalisées chez ces patients, avec un taux de fécondation faible (9,37 %), et aucune grossesse n’a été obtenue. Cette étude a permis de confirmer la variabilité des phénotypes spermatiques observés dans ce syndrome et de faible taux de fécondation après FIV-ICSI, et ce, quel que soit le phénotype.

Knobbed acrosome defect is associated with a region containing the genes STK17b and HECW2 on porcine chromosome 15

BACKGROUND

Male infertility is an increasing problem in all domestic species including man. Localization and identification of genes involved in defects causing male infertility provide valuable information of specific events in sperm development. Correct condensation of the sperm head and development of the acrosome are required for fertile sperm. In the Finnish Yorkshire pig population a knobbed acrosome defect (KAD) has been reported which appears to be of genetic origin. In previous studies we have shown that a large number of affected spermatozoa have a cystic swelling anterior to the apical part of the acrosome.

RESULTS

Characterization of the knobbed acrosome affected sperm revealed that both the acrosomal granules and chromatin are affected. This type of KAD appears to be a previously unknown and serious form of the defect. A genome wide scan with PorcineSNP60 Genotyping BeadChip defined the KAD associated region within 0.7 Mbp on porcine chromosome 15. Two genes, STK17b and HECW2, located within this region were sequenced. The expression of these genes appeared comparable in KA-affected and control boars. The known function of HECW2 in acrosome development highlighted this gene as a good candidate responsible for the KAD. One nonsynonymous SNP was identified within the HECW2 gene. However, as this mutation was found in homozygous state in individuals with normal sperm, this is not likely to be the causal mutation.

CONCLUSIONS

In this study we identified two candidate genes for a severe defect affecting both the sperm acrosome and chromatin that causes infertility. One of these genes, HECW2, plays an important role in ubiquitination, a prerequisite for chromatin remodelling and acrosome formation, highlighting the involvement of this gene in the knobbed acrosome defect and male infertility.

Higher proportion of haploid round spermatids and spermatogenic disomy rate in relation to idiopathic male infertility

OBJECTIVES

To investigate the possible association between the spermatogenic chromosomal aberrations and idiopathic male infertility with normal semen volume, sperm concentration, sperm number per ejaculum, and sperm motility. Male infertility can be considered as a syndrome that results from many congenital or acquired illness. Currently, there is an increasing awareness of the potential role of chromosomal factors in the idiopathic forms of male infertility.

METHODS

A total of 202 idiopathic infertile men and 41 normal fertile donors were recruited into this study, through eligibility screening procedures. Proportions and chromatin status of sperm were assessed by flow cytometry after staining the DNA with propidium iodide. Sperm chromosome aneuploidy rates for chromosome 13, 18, 21, X, and Y were evaluated by fluorescence in situ hybridization using five-color probes.

RESULTS

Infertile males showed a significantly lower percentage of mature haploid sperm cells and higher percentage of haploid round spermatids than the controls. A significantly higher frequency of disomy on spermatozoa was also detected in infertile males compared with the controls.

CONCLUSIONS

These findings suggest that higher frequencies of haploid round spermatids and spermatogenic disomy rate may contribute to elevated risk of idiopathic male infertility.

Male infertility caused by spermiogenic defects: lessons from gene knockouts

Spermiogenesis refers to the process by which postmeiotic spermatids differentiate into elongated spermatids and eventually spermatozoa. During spermiogenesis, round spermatids undergo dynamic morphologic changes, which include nuclear condensation and elongation, formation of flagella and acrosome, reorganization of organelles and elimination of cytoplasm upon spermiation. This cellular differentiation process is unique to male haploid germ cells, which may explain why approximately half of the testis-specific genes are exclusively expressed in spermiogenesis. The spermiogenesis-specific expression implies that these genes contribute to either structural or functional aspects of future sperm. Many such genes have been inactivated in mice and some of these gene knockout mice display male infertility due to nonfunctional sperm which display no or various degrees of structural abnormalities. Since the majority of these spermiogenesis-specific genes are highly conserved between mice and humans, findings from knockout mouse studies may be applicable to human infertility. Here, I briefly review some of these spermatid-specific gene knockouts. The mouse studies strongly suggest that sperm quality rather than quantity is a better indicator of male fertility and novel assays should be developed to determine sperm functionality.

Globozoospermia revisited

Globozoospermia is a rare (incidence <0.1%) but severe disorder in male infertility. Total globozoospermia is diagnosed by the presence of 100% round-headed spermatozoa lacking an acrosome. It is still unclear whether patients whose ejaculate contains both normal and globozoospermic cells (partial globozoospermia) suffer from a variation of the same syndrome. Apart from the fact that affected males suffer from reduced fertility or even infertility, no other physical characteristics can be associated with the syndrome. ICSI is a treatment option for these patients, although low fertilization rates after ICSI show a reduced ability to activate the oocyte. In globozoospermic cells, the use of acrosome markers has demonstrated an absent or severely malformed acrosome. Chromatin compaction appears to be disturbed but is not consistently over- or undercondensed. In some cases, an increased number of cells with DNA fragmentation have been observed. The analysis of the cytogenetic composition revealed an increased aneuploidy rate in some cases. Nonetheless, no increased number of spontaneous abortions or congenital defects has been reported in pregnancies conceived after ICSI. The pathogenesis of globozoospermia most probably originates in spermiogenesis, more specifically in acrosome formation and sperm head elongation. In several knockout mouse models, a phenotype similar to that in humans was found. Together with the occurrence of affected siblings, these findings indicate a genetic origin, which makes globozoospermia a good candidate for genetic analysis. More research is needed to elucidate the pathogenesis of human globozoospermia to further understand globozoospermia as well as (abnormalities in) spermiogenesis and spermatogenesis in general.

Chromosome abnormalities in sperm from infertile men with normal somatic karyotypes: teratozoospermia

Teratozoospermia is characterized by the presence of spermatozoa with abnormal morphology in sperm. This condition is frequently associated with infertility and intracytoplasmic sperm injection (ICSI) is frequently used as the treatment of choice. However, the use of ICSI has created consequential debate concerning the genetic risk for the offspring. Fluorescence in situ hybridization technique (FISH), allowing the specific identification of human chromosomes in sperm nuclei, has been used to study chromosome abnormalities in sperm from men with teratozoospermia and a normal karyotype. In this review, we present studies that have tried to determine if men with a normal blood karyotype but suffering from teratozoospermia present a higher aneuploidy frequency. The literature is limited to three forms of teratozoospermia. The first group consists of "polymorphic teratozoospermia", where a majority of spermatozoa display more than one type of abnormality. In this case, only a slight increase in aneuploidy frequency is observed, which cannot be differentiated from the results observed in oligo-astheno-teratozoospermia (OAT). The second group, named "globozoospermia", is characterized by round spermatic heads, absence of acrosome and disorganization of mid-piece and tail. In this case, some studies have shown a significant, but moderate, increase in the aneuploidy frequency for acrocentrics and sex chromosomes. The aneuploidy frequency remains low, also ICSI can be proposed to these patients, but few successes occur. The third group consists of "enlarged head teratozoospermia", where almost all spermatozoa have an enlarged head, multiple tail and abnormal acrosome. In this case a very high level of missegregation is observed, leading to nearly 100% aneuploidy. In this particular group, ICSI must be refuted, and patients have to be redirected to other possibilities, like sperm donation.

The importance of diagnosis in the clinical management of infertility in the male

This paper examines the importance of a clinical diagnosis in the management of infertility in the male and discusses the reasons for this statement. The treatment of male infertility is now often carried out solely by gynaecologists. These specialists have frequently had little training in the examination of the male genital tract nor have they had any teaching in either urology or in the pathology of the lower genito-urinary tract. The routine application of IVF may be a consequence of these failings and should this form of treatment be shown to have been unnecessary or, especially, should it result in a clinical disaster, then a serious medico-legal problem may result. The degree of training that is given to the gynaecologist working in this field is also examined and suggestions are made as to how this could be improved.

Higher aneuploidy rates of chromosomes 13, 16, and 21 in a patient with globozoospermia

OBJECTIVE

To analyze rates of chromosomal anomalies in a patient with globozoospermia.

DESIGN

Case report.

SETTING

Tertiary-care infertility clinic.

PATIENT(S)

A 44-year-old man with 100% globozoospermia.

INTERVENTION(S)

Fixation of sperms and analysis of aneuploidies and diploidies by fluorescence in situ hybridization.

MAIN OUTCOME MEASURE(S)

Aneuploidy rates of chromosomes 13, 16, and 21 and diploidy rate in a patient with 100% globozoospermia.

RESULT(S)

The aneuploidy rates in spermatozoa from a patient with globozoospermia were significantly higher than in a normospermic man. The incidence of a disomy of the chromosomes 13, 16, and 21 was 4%, 5%, and 1%, respectively, and the nullisomy rates were 2%, 2%, and 3%, respectively.

CONCLUSION(S)

This study demonstrates a positive correlation between globozoospermia and higher chromosomal aneuploidies of the chromosomes 13, 16, and 21, suggesting a higher risk of creating aneuploid embryos after intracytoplasmic sperm injection treatment for globozoospermia patients.

High rate of premature chromosome condensation in human oocytes following microinjection with round-headed sperm: Case report

A young couple proceeded to three ICSI treatment cycles because of male infertility. The semen samples varied between 10 x 10(6) and 36 x 10(6)/ml, 38 and 51% progressive motility but 0% normal morphology. Different types of sperm heads, mostly round-headed with varying spherical appearance (86%) were presented beside acephalic sperm (pinheads; 12%), both one- or two-tailed and the former also without a tail. Very few sperm (2%) exhibited slightly oval-shaped heads. Electron microscopy revealed the absence of the acrosome combined with disturbance of the chromatin condensation among the round-headed sperm. In all three cycles, the fertilization rate using the round-headed sperm fraction was very low with the best result of 2/18 (11%) two-pronucleate oocytes and one one-pronucleate oocyte obtained in the second ICSI cycle. The three oocytes cleaved and were transferred in the 3-4-cell stage without achieving a pregnancy. Of the 29 unfertilized and prepared oocytes from the last two cycles, 27 were informative and revealed the maternal metaphase II chromosomes in the haploid range and a high rate (85%) of premature chromosome condensation (PCC) of the sperm nucleus with remarkable variation in the degree of condensation. Thus, it appears that nearly all round-headed sperm from this patient were incapable of oocyte activation after ICSI, which could be due to non-release (or absence) of an activating factor. As a consequence, PCC was induced in the sperm nuclei by the chromosome condensing factors which were still active in the oopasm of the arrested oocytes.

Search for mutations involved in human globozoospermia*

BACKGROUND

Globozoospermia is a severe form of teratozoospermia characterized by round-headed sperm with an absence of acrosomes. Family cases of globozoopermia suggest that this pathology has genetic origins, but the mode of inheritance remains unknown. So far, no responsible genes have been identified. Recently, a mouse lacking the casein kinase IIalpha' (encoded by the Csnk2a2 gene) was described. This mutant mouse presents a single phenotype reminiscent of that seen in human globozoospermia. Interestingly, the fission yeast orthologue (orb5) exhibits, when mutated, a spherical phenotype. Casein kinase II is a heterotetramer, composed of two catalytic subunits alpha or alpha' and two regulatory beta subunits (encoded by the Csnk2b gene).

METHODS AND RESULTS

Based on the evolution conservation, phenotypes observed in mouse and yeast mutant and the structure of casein kinase II, we analysed Csnk2a2 and Csnk2b genes in six patients with globozoospermia and 10 fertile controls. Genomic DNA was extracted from peripheral blood and PCR was performed to amplify Csnk2a2 and Csnk2b genes before sequencing.

CONCLUSION

No mutation was identified among these six patients. Further work is needed, with a larger patient data set, to identify putative genes involved in this form of male infertility.

Evaluation and treatment of familial globozoospermia in five brothers

OBJECTIVE

To document the pathology of five siblings with complete globozoospermia and to report the effectiveness of repeated intracytoplasmic sperm injection (ICSI) treatment as therapy.

DESIGN

Case report.

SETTING

A tertiary center for assisted reproduction.

PATIENTS(S)

Five siblings with globozoospermia.

INTERVENTION(S)

Twenty cycles of repeated ICSI treatment. Detailed light and electron microscopy studies were performed on three of the globozoospermic brothers.

MAIN OUTCOME MEASURE(S)

Clinical pregnancy and live birth after ICSI treatment.

RESULT(S)

Light and electron microscopy showed that all spermatozoa had round heads and no acrosome. Of 129 metaphase-II oocytes injected, 49 fertilized normally, giving an overall fertilization rate of 38% (range, 0-100%). No pregnancies resulted from 13 cycles in brothers 1-3. Brothers 4 and 5 had three pregnancies after seven ICSI cycles, with one live birth and two first-trimester losses.

CONCLUSION(S)

Despite variable fertilization rates, pregnancies and a live birth can be achieved after repeated ICSI treatment cycles in globozoospermic siblings. No apparent pattern was manifest that reflected the true pathology or determined the outcome of ICSI treatment.

Physiological and proteomic approaches to studying prefertilization events in the human

This research aims firstly to understand, in cellular and molecular terms, how a mature human spermatozoon is prepared for fertilization, and secondly, to identify what factors are involved in the initial signalling interactions between the egg and spermatozoon. In order to achieve these objectives, a combination of approaches is being used, including single-cell imaging, patch clamping and proteomics. Single-cell imaging reveals hidden complexity and heterogeneity in signalling responses in spermatozoa. Characterization of cell physiology at the single-cell level must be a future aim, including the study of ion channel expression and function by patch clamping. Proteomic experiments are aimed at identifying defects in protein expression in specific subgroups of men, e.g. those with globozoospermia. A better understanding of prefertilization events will allow the development of non-assisted reproductive therapy, drug-based treatments for male infertility.

Functional competence of abnormal spermatozoa

The processes of abnormal sperm penetration and incorporation into human oocytes during IVF and after sperm microinjection, assessed by TEM, are reviewed. A spectrum of morphologically abnormal sperm with head, neck and midpiece defects penetrate the egg vestments of oocytes (1-3 h after insemination with sperm from normal donors) in both unfertilized and normally fertilized oocytes. Sperm with aberrant head shapes, acrosomal and nuclear defects penetrate the outer zona pellucida but are rarely encountered in the inner zona and perivitelline space, showing that the zona prevents abnormal sperm penetration. Grossly abnormal sperm are, however, incorporated into the ooplasm of zona-denuded oocytes. Microinjection of poor-quality sperm from male-factor patients into the perivitelline space or directly into the ooplasm of oocytes also reveals a variety of structural defects conforming to those observed in washed sperm pellets, highlighting the difficulties of selection of 'normal' sperm for microinjection. Abnormal sperm have been seen to interact and fuse with the oocyte in the perivitelline space, and to be incorporated into the ooplasm. Those with nuclear and neck (centriolar) defects are of particular significance, as they might contribute to aberrant development. The functional competence of immotile, round-headed and epididymal sperm is also briefly discussed.

Association between human in vitro fertilization rate and pregnancy outcome: a possible involvement of spermatozoal quality in subsequent embryonic viability

A conventional view of mammalian fertilization is that the active component of the process: the spermatozoon, by virtue of its progressive motility and acrosomal enzymes, penetrates an otherwise passive oocyte. This concept has placed bias on spermatozoal normality as largely determining the outcome of fertilization; once this has been achieved then the contribution of the spermatozoon is often forgotten, and attention switches to the maternally derived "blue-print" for early embryonic development. Paternal genomic contribution is known to start at the eight-cell stage in the human, but this is usually after the time when early cleavage stage (2 to 8-cell stage) embryos are replaced in human assisted reproductive technologies (ART) procedures such as in vitro fertilization and embryo transfer (IVF-ET). Hence, fundamental abnormal contributions to embryogenesis derived from the fertilizing spermatozoon have often been ignored. Human IVF-ET has permitted far greater powers of analysis of the fertilization event, and fertilization success appears to be determined in such a system by three main factors: spermatozoal quality, oocyte quality, and quality of in vitro culture conditions (the gamete environment). If the second two factors are more carefully controlled than the first, as is the usual emphasis in routine human IVF practice, then any large variation in fertilization rates that are also significantly related to embryonic viability and ultimately pregnancy outcome, may be thought to be more directly associated with original quality of the fertilizing spermatozoon. An analysis of results of 758 IVF cases provides preliminary evidence to show that there is a close association between human in vitro fertilization rate and subsequent embryo viability following replacement. In accepting this hypothesis as a possibility, we should drastically change our attitude from one of the spermatozoon as a robust, simple initiator of embryonic development, and embrace the idea of the vulnerability of such germ cells both during and after their production, and how detrimental influences on this might profoundly affect embryogenesis after successful fertilization.

Reactive oxygen species and human spermatozoa: analysis of the cellular mechanisms involved in luminol- and lucigenin-dependent chemiluminescence

We have shown that human spermatozoa generate and release reactive oxygen species that can be detected by chemiluminescence techniques. Analysis of the cellular mechanisms responsible for this activity suggests that the probe, luminol, undergoes an intracellular dioxygenation reaction mediated by hydrogen peroxide and a sperm peroxidase located within the acrosome. Support for this model included the following observations: (1) the luminol-dependent signal could be suppressed with peroxidase inhibitors, phenylhydrazine and sodium azide; (2) this suppression could be reversed by the addition of an azide-insensitive peroxidase, horse radish peroxidase (HRP); (3) inhibition of intracellular superoxide dismutase (SOD) with potassium cyanide (KCN) suppressed the luminol signal; (4) peroxidase activity could be detected in purified populations of human spermatozoa with 3,3',5,5' tetramethylbenzidine (TMB); (5) this peroxidase was active at the pH prevailing within the acrosomal vesicle; and (6) peroxidase activity and luminol-dependent chemiluminescence were minimal in spermatozoa exhibiting a congenital absence of acrosomes. Human spermatozoa could also generate lucigenin-dependent chemiluminescent signals that could neither be suppressed with peroxidase inhibitors nor enhanced by the addition of peroxidase. However, these signals could be enhanced by suppression of intracellular SOD with KCN or inhibited by exogenous SOD, suggesting that lucigenin was responding to superoxide anion released into the extracellular space. The ability of chemiluminescent techniques to detect and discriminate the production of superoxide and hydrogen peroxide by spermatozoa should facilitate the further analysis of reactive oxygen species as mediators of normal and abnormal human sperm function.