Is there a relationship between sperm chromosome abnormalities and sperm morphology?

This review explores the relationship between sperm chromosomal constitution and morphology. With the advent of techniques for obtaining information on the chromosome complements of spermatozoa, this relationship has been studied in fertile men and in men with a high frequency of chromosomal abnormalities. Using human sperm karyotype analysis, no relationship between sperm chromosome abnormalities and morphology was found in fertile men, translocation carriers or post-radiotherapy cancer patients. Fluorescence in situ hybridization (FISH) analysis has not generally revealed a specific association between morphologically abnormal sperm and sperm chromosome abnormalities, but has indicated that teratozoospermia, like other forms of abnormal semen profiles (aesthenozoospermia, oligozoospermia) is associated with a modest increase in the frequency of sperm chromosome abnormalities. However, FISH studies on some infertile men and mouse strains have suggested that certain types of morphologically abnormal spermatozoa, such as macrocephalic multitailed spermatozoa, are associated with a very significantly increased frequency of aneuploidy. Thus, there may be an association between sperm morphology and aneuploidy in infertile men with specific abnormalities.     

Human sperm chromosome complements in chemotherapy patients and infertile men

Our studies of human sperm karyotypes and interphase sperm analyzed by fluorescence in situ hybridization (FISH) have both yielded estimates of disomy frequencies of approximately 0.1% per chromosome with an overall aneuploidy frequency in human sperm of approximately 5%–6%. However, the distribution of aneuploidy in sperm is not even, as our data from sperm karyotypes and multicolour FISH analyses both demonstrate a significant increase in the frequency of aneuploidy for chromosome 21 and the sex chromosomes. We have studied men at increased risk of sperm chromosomal abnormalities including cancer patients and infertility patients. Testicular cancer patients were studied before and 2–13 years after chemotherapy (CT) with BEP (bleomycin, etoposide, cisplatin). Sperm karyotype analysis on 788 sperm demonstrated no significant difference in the frequency of numerical or structural chromosomal abnormalities post-CT vs pre-CT. Similarly, multicolour FISH analysis for chromosomes 1, 12, XX, YY and XY in 161,097 sperm did not detect any significant differences in the frequencies of disomy before and after treatment. However, recent evidence has suggested a significant increase in the frequency of disomy and diploidy during CT. We have found that infertile men, who would be candidates for intracytoplasmic sperm injection, have an increased frequency of chromosomally abnormal sperm karyotypes. Also, FISH analysis for chromosomes 1, 12, 13, 21, XX, YY and XY in 255,613 sperm demonstrated a significant increase in chromosomes 1, 13, 21, and XY disomy in infertile men compared with control donors. Received: 4 July 1998; in revised form: 7 September 1998 / Accepted: 8 September 1998     

Genetic diagnosis in infertile men with numerical and constitutional sperm abnormalities

Infertile men having numerical or structural sperm defects may carry several genetic abnormalities (karyotype abnormalities, Y chromosome microdeletions, cystic fibrosis transmembrane conductance regulator (CFTR) gene mutations, androgen receptor gene mutations, and abnormalities seen in sperm cells) leading to this situation. First we aimed to investigate the relationship between the numerical and constitutional (morphological) sperm anomalies and the genetic disorders that can be seen in infertile males. Our other aim was to compare two different kinds of kits that we use for the detection of Y chromosome microdeletions. Sixty-three infertile males [44 nonobstructive azoospermic, 8 severe oligozoospermic, and 11 oligoasthenoteratozoospermic] were investigated in terms of somatic chromosomal constitutions and microdeletions of the Y chromosome. Sperm aneuploidy levels were analyzed by fluorescence in situ hybridization (FISH) in sperm cells obtained from the semen of six OAT patients. Microdeletion and sex chromosome aneuploidy (47,XXY) rates in somatic cells were found to be approximately 3.2% and 4.7%, respectively. Sperm aneuploidy rates were determined as 9%, 22%, and 47% in three patients out of six. Two of these three patients also had high rates of head anomalies in semen samples. High correlation was found between sperm aneuploidy rates and sperm head anomalies. Since the introduction of the assisted reproductive techniques for the treatment of severe male infertility, genetic tests and genetic counseling became very important due to the transmission of genetic abnormalities to the next generation. Thus in a very near future, for a comprehensive male infertility panel, it will be essential to include additional genetic tests, such as CFTR gene mutations, sperm mitochondrial DNA mutations, and androgen receptor gene mutations, besides the conventional chromosomal analyses, Y chromosome microdeletion detection, and sperm-FISH analyses.     

La sélection des spermatozoïdes à fort grossissement permet-elle une diminution de la fréquence des aneuploïdies spermatiques?

Severe male infertility concerns two categories of men. Men with abnormal karyotype, who represent 2 to 14% of infertile men and who can produce sperm cells carrying unbalanced chromosomes related to the patients initial chromosomal reorganization inducing a variable risk of transmission of the abnormality to their conceptus. The second category is men with a normal karyotype but an increased rate of spermatic aneuploidy in a context of severe oligo- and/or asthenozoospermia and men from couples in implantation failure. ICSI is the standard Assisted Medical Reproductive technique for most of these 2 categories despite the obvious increased chromosomal risk. This raises the question of how to morphologically identify sperm cells with abnormal chromosome content during ICSI ? Unfortunately, no relationship has yet been found between sperm morphology in the ICSI sperm fraction (×200) and their chromosome content. Nevertheless, since the end of the 1990s, Bartoov’s team has developed MSOME (Motile Sperm Organelle Morphology Examination) consisting of high-power examination of sperm cells up to × 12,250. This technique was indicated for cases of repeated ICSI failures and appeared to increase pregnancy rates. But was this improvement due to better selection of the chromosomal content of sperm cells to be injected? The present study addressed this question by estimating the value of MSOME in the selection of euploid sperm cells in 2 groups of patients known to have an increased rate of sperm aneuploidy. Group 1 was composed of 2 patients with normal karyotype who presented a macrocephalic sperm syndrome with more than 99% of aneuploid sperm. Group 2 was composed of 11 patients with abnormal karyotype: 6 patients with reciprocal translocation and 5 patients with Robertsonian translocation. The purpose of this study was to compare spermatozoa aneuploidy rates in fresh semen, to those obtained after ICSI selection (×200) and MSOME selection (×6000). Three specific steps of the protocol were (1) all sperm cells selected in MSOME were “top sperm cells“ (2) fixation of selected sperm cell (average loss of 15% during FISH washes) (3) FISH results were validated by two different examiners. FISH analysis of X, Y and 18 chromosomes showed that MSOME eliminates polyploid and diploid sperm cells in patients with macrocephalic sperm syndrome, but the 6 sperm cells selected were all haploid and aneuploid. FISH analysis of X, Y and 18 chromosomes of all other patients did not show any influence of the selection method on the aneuploidy rate. For the 5 subjects with a Robertsonian translocation, the global results of FISH analysis paradoxically showed a significant decrease of the euploidy rate in MSOME selection. The global results of FISH analysis for the 6 patients with mutual reciprocal translocations, showed that the various mutual translocations were not modified between whole sperm and the 2 selection methods. On the other hand, a significant decrease of adjacent 1 and 2 segregation frequency was observed between whole sperm and MSOME selection, associated with a significant increase of 3:1 segregation frequency suggesting that the segregations which modify the structure of chromosomes, for example adjacent 1 and 2 segregations, would induce visible morphological modifications selected by MSOME. We hypothesized that the efficacy of spermatic apoptosis could be modulated by morphology but also by the chromosome contents of the sperm cell. In conclusion, MSOME does not provide any guarantee of the normal chromosome contents of the TOP selected sperm cell. However, these results obtained in a small series of patients suggest that MSOME can eliminate some chromosome abnormalities (adj1 and 2) which would alter sperm nuclear structures.     

Chromosomal evaluation in a group of Tunisian patients with non-obstructive azoospermia and severe oligozoospermia attending a Tunisian cytogenetic department

Male infertility is the cause in half of all childless partnerships. Numerous factors contribute to male infertility, including chromosomal aberrations and gene defects. Few data exist regarding the association of these chromosomal aberrations with male infertility in Arab and North African populations. We therefore aimed to evaluate the frequency of chromosomal aberrations in a sample of 476 infertile men with non-obstructive azoospermia (n = 328) or severe oligozoospermia (n = 148) referred for routine cytogenetic analysis to the department of cytogenetics of the Pasteur Institute of Tunis. The overall incidence of chromosomal abnormalities was about 10.9%. Out of the 52 patients with abnormal cytogenetic findings, sex chromosome abnormalities were observed in 42 (80.7%) including Klinefelter syndrome in 37 (71%). Structural chromosome abnormalities involving autosomes (19.2%) and sex chromosomes were detected in 11 infertile men. Abnormal findings were more prevalent in the azoospermia group (14.02%) than in the severe oligozoospermia group (4.05%). The high frequency of chromosomal alterations in our series highlights the need for efficient genetic testing in infertile men, as results may help to determine the prognosis, as well as the choice of an assisted reproduction technique. Moreover, a genetic investigation could minimize the risk of transmitting genetic abnormalities to future generations.     

Aneuploid spermatozoa in infertile men: teratozoospermia.

We and others have demonstrated that infertile men who are candidates for intracytoplasmic sperm injection (ICSI) have an increased frequency of chromosomal abnormalities in their sperm. Reports based on prenatal diagnosis of ICSI pregnancies have confirmed the increased frequency of chromosomal abnormalities in offspring. Most studies to date have lumped various types of infertility together. However, it is quite likely that some subsets of infertility have an increased risk of sperm chromosomal abnormalities whereas others do not. We have studied nine men with severe teratozoospermia (WHO, 1992 criteria, 0-13% morphologically normal forms) by multicolour fluorescence in situ hybridisation (FISH) analysis to determine if they have an increased frequency of disomy for chromosomes 13, 21, XX, YY, and XY, as well as diploidy. All of the men also had aesthenozoospermia (< 50% forward progression) but none of the men had oligozoospermia (<20 x 10(6) sperm/ml). The patients ranged in age from 20 to 49 years (mean 33.2 years) in comparison to 18 normal control donors who were 23 to 58 years (mean 35.6 years). The control donors had normal semen parameters and no history of infertility. A total of 180,566 sperm were scored in the teratozoospermic men with a minimum of 10,000 sperm analyzed/donor/chromosome probe. There was a significant increase in the frequency of disomy in teratozoospermic men compared to controls for chromosomes 13 (.23 vs.13%), XX (.13 vs.05%), and XY (.50 vs.30%) (P <.0001, 2-tailed Z statistic). This study indicates that men with teratozoospermia and aesthenozoospermia but with normal concentrations of sperm have a significantly increased frequency of sperm chromosomal abnormalities.     

Quelle valeur attribuer à l’analyse morphologique des spermatozoïdes en microscopie optique?

The value of sperm morphology to predict the sperm fertilizing capacity is a subject of ongoing debate. However, it is clear that sperm morphological examination is essential to determine sperm quality as part of the assessment of male or couple infertility. Moreover, application of a new high-power magnification method, which allows the choice of spermatozoa with a preferred nuclear morphology, is positively correlated with a dramatic increase in IVF-IMSI pregnancy rates. Several detailed classification systems of sperm abnormalities have been proposed over the last fifty years and each revision of these classifications introduces stricter criteria. Three of these classifications are generally used as reference classifications: the Kruger/Tygerberg classification and the David classification, carefully revised by Auger and Eustache to ensure quality assurance in reproduction biology. However, the results of sperm analyses are very heterogeneous in terms of the overall percentage of morphological abnormalities and the respective frequencies of the various abnormalities. This examination must therefore be performed very carefully based on strictly defined criteria for the assessment of each abnormality with harmonization of these criteria between the various observers in the same laboratory and between laboratories. Various studies have examined the impact of isolated teratozoospermia on the results of IVF and ICSI, but once again with sometimes contradictory results. However, most studies show that the percentage of morphologically normal sperm is positively correlated with the results of ICSI, and many authors agree that a percentage of morphologically normal sperm less than 5% is predictive of low fertilization and pregnancy rates in IVF and ICSI. Over the last ten years, it has been shown that aneuploidy rates in the semen of populations of infertile men with moderate or severe oligospermia were higher than those in fertile men with normal sperm counts, and that sperm disomy rates were about 20-fold higher in ICSI than in IVF. However, the results of these various studies fail to demonstrate an obvious link between polymorphic teratozoospermia and the frequency of disomy and aneuploidy in sperm. Consequently, light microscopy sperm morphological examination, at the magnifications generally used for sperm counts (x 2000), is therefore not a good indicator of chromosomal abnormalities in human semen, except in the rare cases of monomorphic abnormalities. However, this is not the case for the link between sperm morphology and apoptosis, as a growing number of studies establish a positive correlation between male infertility and the presence of apoptotic markers on spermatozoa, and morphological parameters appear to be closely correlated with apoptosis. Finally, standardization of examination procedures and reporting of the results of sperm morphological examination is absolutely essential.     

Human sperm aneuploidy after exposure to pesticides

This study examined the effect of paternal environmental exposure to pesticides on the frequency of aneuploidy in human sperm. To determine if the chromosome number in germ cells was altered by paternal exposure, multicolor fluorescence in situ hybridization (FISH) analysis was utilized to measure aneuploidy frequencies in the sperm of 40 men (20 exposed, 20 controls). Samples were coded for "blind analysis" to eliminate scorer bias. Aneuploidy and diploidy frequencies were assessed for chromosomes 13, 21, X, and Y. A minimum of 10,000 sperm was scored per donor per chromosome probe with a total of 809,935 sperm scored. Hybridization efficiency was 99%. There were no significant differences in aneuploidy or diploidy frequencies between exposed and control groups, suggesting that the pesticides did not increase the risk of numerical chromosomal abnormalities in these men.     

Germ-cell nondisjunction in testes biopsies of men with idiopathic infertility.

Intracytoplasmic sperm injection (ICSI) has been used in combination with testicular sperm extraction to achieve pregnancies in couples with severe male-factor infertility, yet many of the underlying genetic mechanisms remain largely unknown. To investigate nondisjunction in mitotic and meiotic germ cells, we performed three-color FISH to detect numeric chromosome aberrations in testicular tissue samples from infertile men confirmed to have impaired spermatogenesis of unknown cause. FISH was employed to determine the rate of sex-chromosome aneuploidy in germ cells. Nuclei were distinguished as haploid or diploid, respectively. The overall incidence of sex-chromosome aneuploidy in germ cells was found to be significantly higher (P<.00001) in all three abnormal histopathologic patterns (range 39.0%-43.5%) as compared with normal controls (29.1%). The relative ratio of normal to aneuploid nuclei in the diploid cells of patients with impaired spermatogenesis was approximately 1.0, a >300% decrease when compared with the 4.42 ratio detected in patients with normal spermatogenesis. These results provide direct evidence of an increased incidence of sex-chromosome aneuploidy observed in germ cells of men with severely impaired spermatogenesis who might be candidates for ICSI with sperm obtained directly from the testis. The incidence of aneuploidy was significantly greater among the diploid nuclei, which suggests that chromosome instability is a result of altered genetic control during mitotic cell division and proliferation during spermatogenesis.     

Screening for microdeletions in human Y chromosome--AZF candidate genes and male infertility

About 30% of couple infertilities are of male origin, some of them caused by genetic abnormalities of the Y chromosome. Deletions in AZF region can cause severe spermatogenic defects ranging from non-obstructive azoospermia to oligospermia. The intracytoplasmatic sperm injection technique (ICSI) is rapidly becoming a versatile procedure for human assisted reproduction in case of male infertility. The use of ICSI allows Y chromosome defects to be passed from father. The goal of our study is to evaluate the frequency of microdeletions in the long arm of Y chromosome, within the AZF regions, in these cases of infertilities, using molecular genetics techniques. Thirty infertile men with azoospermia or oligozoospermia, determined by spermogram, were studied after exclusion of patients with endocrine or obstructive causes of infertility. Peripheral blood DNA was extracted from each patient, then amplified by multiplex PCR with STS genomic markers from the Y chromosome AZF zones. Each case was checked by multiplex PCR through coamplification with the SRY marker. Three men with microdeletions of the long arm of the Y chromosome were diagnosed among the 30 patients, corresponding to a proportion of 10%. The relatively high proportion of microdeletions found in our population suggest the need for strict patient selection to avoid unnecessary screening for long arm Y chromosome microdeletions. The molecular diagnostics was performed according to the current European Academy of Andrology laboratory guidelines for molecular diagnosis of Y chromosomal microdeletions.     

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

The aim of aneuploidy evaluation in spermatozoa from patients presenting spermatogenesis defects is to identify a relationship between meiotic errors and quantitative or qualitative alterations of spermatogenesis. During the past ten years, the use of fluorescence in situ hybridization (FISH) has permitted the determination of the frequency of numerical chromosome aberrations in different clinical situations. It has been established that infertile males with reduced sperm count and a normal constitutional karyotype have a significantly high risk of aneuploidy in their spermatozoa particularly regarding sex chromosomes. Concerning sperm motility, the data are more controversial. However, patients of severe asthenozoospermia induced by specific morphological deformities involving sperm flagella have a significantly high risk of producing aneuploid spermatozoa.     

Chromosome abnormalities in sperm from infertile men with asthenoteratozoospermia

Research over the past few years has clearly demonstrated that infertile men have an increased frequency of chromosome abnormalities in their sperm. These studies have been further corroborated by an increased frequency of chromosome abnormalities in newborns and fetuses from pregnancies established by intracytoplasmic sperm injection. Most studies have considered men with any type of infertility. However, it is possible that some types of infertility have an increased risk of sperm chromosome abnormalities, whereas others do not. We studied 10 men with a specific type of infertility, asthenozoospermia (poor motility), by multicolor fluorescence in situ hybridization analysis to determine whether they had an increased frequency of disomy for chromosomes 13, 21, XX, YY, and XY, as well as diploidy. The patients ranged in age from 28 to 42 yr (mean 34.1 yr); they were compared with 18 normal control donors whose ages ranged from 23 to 58 yr (mean 35.6 yr). A total of 201 416 sperm were analyzed in the men with asthenozoospermia, with a minimum of 10 000 sperm analyzed per chromosome probe per donor. There was a significant increase in the frequency of disomy in men with asthenozoospermia compared with controls for chromosomes 13 and XX. Thus, this study indicates that infertile men with poorly motile sperm but normal concentration have a significantly increased frequency of sperm chromosome abnormalities.     

A comparison of the frequency of sperm chromosome abnormalities in men with mild,moderate, and severe oligozoospermia

Infertile men undergoing intracytoplasmic sperm injection have an increased frequency of chromosome abnormalities in their sperm. Men with low sperm concentration (oligozoospermia) have an increased risk of sperm chromosome abnormalities. This study was initiated to determine whether men with severe oligozoospermia (<10(6) sperm/ml) have a higher frequency of chromosome abnormalities in their sperm compared with men with moderate (1-9 x 10(6) sperm/ml) or mild (10-19 x 10(6) sperm/ml) oligozoospermia. Multicolor fluorescence in situ hybridization analysis was performed using DNA probes specific for chromosomes 13, 21, X, and Y (with chromosome 1 as an autosomal control for the sex chromosomes). Aneuploidy and disomy frequencies were assessed from a total of 603,011 sperm from 30 men: 10 in each of the categories. The mean frequencies of disomy for the patients with mild, moderate, and severe oligozoospermia were 0.17%, 0.24%, and 0.30%, respectively, for chromosome 13 and 0.22%, 0.44%, and 0.58%, respectively, for chromosome 21. For the sex chromosomes, the mean frequencies of disomy for mild, moderate, and severe oligozoospermia were 0.25%, 1.04%, and 0.68%, respectively, for XY, 0.047%, 0.08%, and 0.10%, respectively, for XX, and 0.04%, 0.06%, and 0.09%, respectively, for YY. The frequencies for diploidy also increased from 0.4% for mild to 1.20% for moderate to 1.24% for severe oligozoospermia. There was a significant inverse correlation between the frequency of sperm chromosome abnormalities and the sperm concentration for XY, XX, and YY disomy and diploidy. These results demonstrate that men with severe oligozoospermia have an elevated risk for chromosome abnormalities in their sperm, particularly sex chromosome abnormalities.     

Simultaneous detection of structural and numerical chromosome abnormalities in sperm of healthy men by multicolor fluorescence in situ hybridization

Both structural and numerical chromosome aberrations in sperm represent important categories of paternally transmitted genetic damage. Therefore, a new multiprobe fluorescence in situ hybridization (FISH) method, using DNA probes for three targets (centromere and telomere of chromosome 1, centromere of chromosome 8), was developed to detect human sperm carrying three types of chromosomal defects: (1) terminal duplications or deletions in chromosome 1p, (2) aneuploidy involving chromosomes 1 or 8, and (3) diploidy. Baseline frequencies were determined for three healthy donors who had been previously evaluated for sperm cytogenetics by the human-sperm/hamster-oocyte cytogenetic technique (hamster technique). Among ∼120 000 sperm analyzed by the new FISH method, the average baseline frequencies of sperm carrying telomeric duplications and deletions of 1p were 3.2 ± 1.9 and 2.9 ± 3.6 per 10⁴, respectively. Diploid sperm was found in an average frequency of 6.6 ± 4.0 per 10⁴. Average frequencies of disomic sperm for chromosomes 1 or 8 were 1.7 ± 2.2 and 1.9 ± 2.3 per 10⁴, respectively. Inter-individual differences were observed for deletions of 1p but not for the other sperm phenotypes. A good correlation was obtained between the frequencies of sperm with structural chromosome aberrations detected with the new assay and the frequency of sperm carrying premeiotic or meiotic cytogenetic damage detected with the hamster technique. The observed levels of numerical aberrations with the new FISH assay were within range of the baseline frequencies reported by the hamster technique. The newly developed FISH assay has promising applications in genetic, clinical, physiological and toxicological studies. Received: 26 February 1996 / Revised: 6 May 1996     

Necessity of nuclear and mitochondrial genome analysis prior to assisted reproductive techniques/intracytoplasmic sperm injection

Assisted reproductive technique (ART) has revolutionized the management of severe male factor infertility and in some countries 5% babies are conceived through ART/intra cytoplasmic sperm injection (ICSI). However, the carry-home live birth rate after several ART cycles is low (18-25%) and this is financially, physically and emotionally crippling for the couples. Genetic factors could lead to pre or post-implantation failure and thus explain for low ART success rate. Thus, this study was planned to understand, if infertile men harbour genetic abnormalities which may be iatrogenically transmitted by ART and adversely affect growth potential of embryo. Ninety infertile men underwent semen, cytogenetic, Yq microdeletion and mitochondrial mutation analysis. Of these, 14.4% cases harboured cytogenetic abnormality, and 8.89% Yq microdeletions. A high frequency of mitochondrial mutations was found in 23 men with asthenospermia. It is important to understand that through ART genetic abnormalities are transmitted to offspring, resulting in impaired growth and development potential of embryo and poor take-home live birth rate. Thus, genetic analysis is strongly recommend in all men with idiopathic infertility who opt for ART to counsel couples and provide them with most adapted therapeutics.     

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.     

Chromosomal Abnormality and Y Chromosome Microdeletion in Chinese Patients with Azoospermia or Severe Oligozoo-spermia

Chromosomal abnormality and Y chromosome microdeletion are regarded as two frequent genetic causes associated with spermatogenic failure in Caucasian population. To investigate the distribution of the two genetic defects in Chinese patients with azoospermia or severe oligozoospermia, karyotype analysis by G-banding was carried out in 358 idiopathic infertile men, including 256 patients with azoospermia and 102 patients with severe oligozoospermia, and screening of AZF region microdeletion of Y chromosome by multiplex PCR was performed in those patients without detectable chromosomal abnormality and 100 fertile controls. Of 358 patients, 39(10.9%) were found to have chromosomal abnormalities in which Klinefelters syndrome (47, XXY) was the most common chromosomal aberration. The incidence of sex chromosomal abnormality in patients with azoospermia was significantly higher than that in patients with severe oligozoospermia (12.1% vs 1%). Among the rest of the 319 patients with normal karyotype, 46 (14.4%) were found to have microdeletions in AZF region. The prevalence rates of AZF microdeletion was 15% and 13.1% in patients with azoospermia and severe oligozoospermia respectively. The microdeletion in AZFc was the most frequent deletion and all the microdeletions in AZFa were found in azoospermic patients. No microdeletion in AZF region was detected in fertile controls. In conclusion, chromosomal abnormality and AZF region microdeletion of Y chromosome might account for about 25% of Chinese infertile patients with azoospermia or severe oligozoospermia, suggesting the two abnormalities are important genetic etiology of spematogenic failure in Chinese population and it is essential to screen them during diagnosis of male infertility before in vitro assisted fertilization by introcytoplasmic sperm injection.     

中国无精症、严重寡精症患者的染色体异常和Y染色体微缺失

染色体异常和Y染色体微缺失被认为是两个白种人群中常见的生精障碍相关遗传因素。为了解中国无精症、严重寡精症患者中的染色体异常和Y染色体微缺失,运用染色体G显带技术,在358个原发无精症（256人）和严重寡精症（102人）不育患者中进行染色体核型分析;同时运用多重PCR技术,在核型正常的患者和100个正常生育男性中,对Y染色体AZF区微缺失进行筛查。在358个患者中,39人（10．9％）发现有染色体异常,Klinefelter（47,XYY）最为常见。无精症患者性染色体异常频率明显高于严重寡精症患者（12．1％VS1％）。在319个核型正常的患者中,46（14．4％）发现有AZF区微缺失,无精症和寡精症患者中Y染色体微缺失频率分别为15％和13．1％,AZFc区的微缺失最为常见,AZFa区的微缺失只见于无精症患者,正常生育男性中未发现AZF区的微缺失。结果显示,在中国无精症、严重寡精症患者中,大约25％的患者有染色体异常或Y染色体AZF区微缺失,提示这两种遗传异常是中国人群生精障碍的重要相关遗传病因,有必要在男性不育的诊断以及利用细胞浆内精子注射技术进行辅助生育时,对患者的这些遗传异常进行筛查。     

Variation in the frequency and type of sperm chromosomal abnormalities among normal men

Summary The chromosomal constitution of 1582 human sperm from 30 normal men of proven fertility was investigated after sperm penetration of hamster eggs. A minimum of 30 sperm chromosome complements were analysed per donor so that the distribution and variation in the frequency and type of sperm chromosomal abnormalities could be assessed. The mean frequency of sperm chromosomal abnormalities in individual men was 10.4% (±6.0%) with a range of 0–24.7%. For numerical abnormalities the mean was 4.7% (±2.9%) with a range of 0–10% and for structural abnormalities the mean was 6.2% (±6.0%) with a range of 0–23.1%. The 95% confidence intervals for the mean of an individual male were 0–10.5% for numerical abnormalities, 0–18.2% for structural abnormalities, and 0–22.4% for total abnormalities. There was a significant excess of hypohaploid complements compared with hyperhaploid complements. Since hypohaploid complements could be caused by technical artefact, a conservative estimate of aneuploidy was obtained by doubling the frequency of hyperhaploid sperm, yielding an estimate of 2.4% aneuploidy. The proportion of X-bearing (53%) and Y-bearing (47%) sperm did not differ significantly. These results were compared to the other two large studies of sperm chromosome complements from normal men.     

Increase of ICSI efficiency with hyaluronic acid binding sperm for low aneuploidy frequency in pig

The present study was designed to evaluate the ability of hyaluronic acid binding sperm (HABS) in increasing the efficiency of intracytoplasmic sperm injection (ICSI) in terms of the production of chromosomally normal porcine embryos. Porcine embryos were produced by in vitro fertilization (IVF), ICSI and ICSI using hyaluronic acid binding sperm (ICSI-HABS). Chromosome aneuploidy in sperm and embryos was evaluated using chromosome 1 submetacentric probe for fluorescence in situ hybridization (FISH) analysis. No significant differences were observed in the blastocysts rates (18.6, 23.6 and 23.8%) and cell numbers (61.8+/-12.5, 55.5+/-7.3 and 59.3+/-9.6) among embryos derived from IVF, ICSI, and ICSI-HABS. However, the frequency of normal diploidy in ICSI-HABS (75.5%) was significantly higher (P<0.05) than that in IVF (57.0%) and ICSI (68.2%). Embryos from ICSI-HABS showed significantly lower chromosome abnormality rate (P<0.05). Both ICSI and IVF embryos showed higher rates of polyploidy, and hence chromosomally abnormal embryos, in comparison to ICSI-HABS embryos. In addition, we investigated the chromosomal complement of porcine spermatozoa by FISH. The rate of chromosome number abnormality in porcine sperm was found to be 6.25% (70/1120). Thus, we conclude that the use of hyaluronic acid binding sperm is superior to morphological sperm selection for ICSI in producing chromosomally normal embryos and increasing the ICSI efficiency by lowering the aneuploidy frequency. Our results indicate that the selection of normal sperm with hyaluronic acid binding assay might help to reduce the early embryonic mortality due to chromosomal aneuploidy thereby increasing the success rate of embryo transfer technology in pigs.