Cytogenetic determinants of male fertility

BACKGROUND

Cytogenetic abnormalities have been known to be important causes of male infertility for decades.

METHODS

Research publications from 1978 to 2008, from PubMed, have been reviewed.

RESULTS

These studies have greatly improved our information on somatic chromosomal abnormalities such as translocations, inversions and sex chromosomal anomalies, and their consequences to the cytogenetic make-up of human sperm. Also, we have learned that infertile men with a normal somatic karyotype have an increased risk of chromosomally abnormal sperm and children. New techniques such as single sperm typing and synaptonemal complex analysis have provided valuable insight into the association between meiotic recombination and the production of aneuploid sperm. These meiotic studies have also unveiled errors of chromosome pairing and synapsis, which are more common in infertile men.

CONCLUSIONS

These studies allow us to provide more precise information to infertile patients, and further our basic knowledge in the causes of male infertility.

Urinary Bisphenol A Levels and Male Fertility

Bisphenol A (BPA) is a high-production volume industrial chemical found in many consumer products. BPA is a suspected potent endocrine disruptor, with endocrine-disrupting properties demonstrated in animal studies. Few human studies have examined bisphenol A exposure in relation to male fertility and, results are divergent. The aim of the study is to examine the associations between urinary BPA concentration and male fertility. Bisphenol A urinary concentrations were measured using gas chromatography coupled with tandem mass spectrometry in 315 men under 45 years of age with normal sperm concentration (⩾15 mln/ml) recruited from a male reproductive health clinic. Participants were interviewed and provided a semen sample. BPA was detected in 98.10% of urine samples, with a median concentration of 1.87 µg/l (1.63 µg/ g creatinine). A multiple linear regression analysis identified a positive association between the urinary concentrations of bisphenol A 25th–50th percentile and total sperm sex chromosome disomy (p = .004). Also when modeled as continuous variable urinary BPA concentration increased total sperm sex chromosome disomy (p = .01). Urinary concentration of BPA also increase the percentage of immature sperm (HDS) (p = .018) and decrease motility (p = .03). The study provides evidence that exposure to BPA is associated with poorer semen quality. Future studies are needed to confirm these findings.

Sperm aneuploidy in infertile male patients: a systematic review of the literature

Males with abnormal karyotypes and subgroups of fertile and infertile males with normal karyotypes may be at risk of producing unbalanced or aneuploid spermatozoa. Biological, clinical, environmental and other factors may also cause additional sperm aneuploidy. However, increased risk of sperm aneuploidy is directly related to chromosomally abnormal embryo production and hence to poor reproductive potential. This systemic literature review focuses on the identification of these males because this is an essential step in the context of assisted reproduction. This research may allow for a more personalised and, hence, more accurate estimation of the risk involved in each case, which in turn will aid genetic counselling for affected couples and help with informed decision-making.

Comparison of sperm morphology and nuclear sperm quality in SPATA16- and DPY19L2-mutated globozoospermic patients

The aim of this study was to compare the sperm morphology and nuclear sperm quality (sperm aneuploidy and DNA fragmentation) in two groups of globozoospermic patients: DPY19L2-mutated patients (n = 6) and SPATA16-mutated patients (n = 2). Results for these two groups were also compared to a group of fertile men (n = 25). Fluorescence in situ hybridisation was performed for chromosomes X, Y and 18. Sperm DNA fragmentation was evaluated by TUNEL assay. Sanger sequencing was performed for mutations screening of DPY19L2 and SPATA16 genes. Sperm analysis revealed a classic phenotype of total globozoospermia in DPY19L2-mutated group and a particular phenotype characterised by a predominance of double/multiple round-headed (39.00 ± 4.2%) and multi-tailed spermatozoa (26.00 ± 16.97%) in SPATA16-mutated group. FISH analysis showed a significantly higher aneuploidy rate in globozoospermic patients compared to controls (p < 0.05), and a higher rate was observed in SPATA16-mutated group compared to DPY19L2-mutated group (p < 0.05). DNA fragmentation index was significantly higher in globozoospermic men compared to controls (p < 0.001), and there is no statistically significant difference between the two globozoospermic groups. We showed that SPATA16 defects could be associated with an abnormal meiosis leading to a particular morphological sperm defect of double/multiple round-headed and multi-flagella and a higher sperm aneuploidy rate than in case of DPY19L2-defects in classic globozoospermia.

Impact on testicular function of a single ablative activity of 3.7 GBq radioactive iodine for differentiated thyroid carcinoma

STUDY QUESTION

What are the consequences of radioactive iodine (RAI) therapy for testicular function?

SUMMARY ANSWER

A single activity of 3.7 GBq RAI for differentiated thyroid carcinoma (DTC) treatment in young men transiently altered Sertoli cell function and induced sperm chromosomal abnormalities.

WHAT IS KNOWN ALREADY

Few studies, mainly retrospective, have reported the potential impacts of RAI on endocrine and exocrine testicular function.

STUDY DESIGN, SIZE, DURATION

A longitudinal prospective multi-center study on testicular function performed in DTC patients before a single 131I ablative activity of 3.7 GBq (V0) and at 3 months (V3) and 13 months (V13) after treatment.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Forty male patients, aged 18-55 years, with DTC participated. Hormonal analysis included FSH, LH, testosterone and inhibin B serum levels at V0, V3 and V13. Furthermore, sperm parameters, DNA fragmentation and sperm chromosomal abnormalities were evaluated at each time points. The differences in all parameters, between V0-V3, V0-V13 and V3-V13, were analyzed, using a Wilcoxon test.

MAIN RESULTS AND THE ROLE OF CHANCE

Prior to RAI administration, all patients had normal gonadal function. At V3, a statistically significant increase in FSH levels and a decrease in inhibin B levels were observed and sperm concentration, as well as the percentage of morphologically normal spermatozoa, were significantly decreased (P < 0.0001). These modifications were transient as both sperm concentration and normal morphology rate returned to baseline values at V13. However, at this later time point, FSH and inhibin B levels were still impacted by RAI administration but remained in the normal range. Although no DNA fragmentation was observed at V3 nor V13, our study revealed a statistically significant increase in the number of sperm chromosomal abnormalities both at V3 (P < 0.001) and V13 (P = 0.01).

LIMITATIONS, REASONS FOR CAUTION

Among the 40 patients included in the study, only 24 had all the parameters available at all visits.

WIDER IMPLICATIONS OF THE FINDINGS

Prospective studies with longer term follow up would be helpful to determine whether the chromosome abnormalities persist. These studies would be required before sperm banking should be suggested for all patients. However, sperm preservation for DTC patients who require cumulative radioiodine activities higher than 3.7 GBq should be proposed.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Programme Hospitalier de Recherche Clinique, AP-HP (No. P040419). The authors report no conflict of interest in this work.

TRIAL REGISTRATION NUMBER

NCT01150318.

Aneuploidy frequency in spermatozoa of Egyptian men with normal and abnormal semen parameters using fluorescence in situ hybridisation

Chromosome anomalies were suggested to be more frequent in infertile males so our case-control study aimed at evaluating the incidence of spermatic aneuploidies in forty males with severe oligoasthenoteratozoospermia (OAT) and comparing it with that in another forty males having normal semen parameters. Semen samples were collected and analysed in the Clinical Pathology Department according to criteria of the World Health Organization (WHO laboratory manual for the examination and processing of human semen, 2010, WHO Press). Fluorescence in situ hybridisation (FISH) was performed on decondensed spermatozoa from fresh semen ejaculates, using dual coloured chromosome-specific DNA probes labelled with fluorochromes to study sperm aneuploidies in chromosomes 13, 21, X and Y. There was no statistical significant difference between cases and controls regarding disomy frequencies for chromosomes 13, 21 or both combined. However, 13, 21 diploidy frequency was significantly higher among OAT cases. Regarding chromosomes X and Y, both cases and controls showed similar results for disomy/diploidy frequency for both chromosomes; however, there was a statistical significant increase in YY disomy/diploidy frequency among OAT patients. X chromosome-bearing spermatozoa were found to be significantly higher among controls. Patients with severe OAT have a higher total sperm aneuploidy rate, regarding chromosomes 13, 21, X and Y but without a statistical significant difference.

Reasons that should prompt a referral to a reproductive urologist: guidelines for the gynecologist and reproductive endocrinologist

Obstetricians and gynecologists, and in particular reproductive endocrinologists (REIs), are typically the gatekeepers and first-line providers for couples initially seeking an infertility evaluation. A timely referral to a reproductive urologist may improve pregnancy outcomes in certain clinical scenarios. This review examines the evidence behind circumstances requiring referral and delivers practice-based recommendations on commonly encountered scenarios in the clinic. Scenarios that should prompt referral to a reproductive urologist include semen analysis (SA) abnormalities (e.g., asthenozoospermia, azoospermia, globozoospermia, leukocytospermia, necrozoospermia, oligospermia), recurrent intrauterine insemination (IUI)/in vitro fertilization (IVF) failure, and idiopathic recurrent pregnancy loss (RPL). Conversely, deferment is appropriate in the cases of isolated teratozoospermia and subclinical varicocele. Men with infertility are also at higher risk for other comorbid conditions and should have at least a baseline evaluation by a primary care physician. Coordination of care between a REI and reproductive urologist is critical in several clinical scenarios and expedient referral can improve reproductive outcomes.

Semen Quality is Associated with Sperm Aneuploidy and DNA Fragmentation in the United Arab Emirates Population

Background: Sperm chromosome aneuploidy and the extent of sperm DNA fragmentation (SDF) are contributing factors to male infertility. Their extent can be measured using platforms such as sperm chromatin dispersion (SCD) and sperm fluorescence in situ hybridization (sFISH). Additional studies, however, are needed to understand the clinical applicability of these in vitro tests based on statistically validated thresholds. Aim: The primary objective of this study was to report the incidence of SDF and chromosomal aneuploidy with respect to sperm quality in the United Arab Emirates (UAE) population. In addition, we wished to establish clinically useful SDF and aneuploidy cutoff values. Materials and Methods: A total of 302 subjects were enrolled in this study. The control group consisted of n = 100 (33.11%) reproductively-proven fertile men, and the case group consisted of n = 202 (66.89%) infertile men. The sperm quality of the cases was further subclassified as normospermia ("Normo," n = 88; 43.56%); teratozoospermia ("T," n = 40; 19.80%); oligoasthenoteratozoospermia ("OAT," n = 37; 18.32%); asthenoteratozoospermia ("AT," n = 19; 9.41%); or oligoteratozoospermia ("OT," n = 18; 8.91%). The assessments of SDF were done using SCD tests. Chromosomal aneuploidy (Chr 13, 18, 21, X, and Y) was investigated using sFISH. Furthermore, based on the fragmentation index, cases were divided into subfertile groups defined as low, medium, high, and severe. The Mann-Whitney test was used to set the upper threshold value for sFISH, and the odds ratio was used for SDF assessment. Results: Cases having sperm quality "AT," "OAT," and "OT" together with the moderate, high, and severe subfertile groups had the highest DNA fragmentation indices: 31.58%, 27.03%, and 22.22%, respectively. In the sFISH analyses, groups with sperm quality "OAT," "T," and "OT" exhibited high degrees of abnormalities: 86.49%, 52.50%, and 50%, respectively. The most common chromosomal abnormalities found were "sex chromosome hyperploidy (XY18)" and "diploid (Chr 13, 21)." The incidences of sperm quality with respect to SDF and sFISH are also reported in detail. Conclusions: This is the first study in the UAE which shows SDF and sFISH incidences together with sperm quality. This study also establishes SDF and sFISH cutoff values for the UAE population.

Polymorphic Rearrangements of Human Chromosome 9 and Male Infertility: New Evidence and Impact on Spermatogenesis

Chromosomal polymorphisms are structural variations in chromosomes that define the genomic variance of a species. These alterations are recurrent in the general population, and some of them appear to be more recurrent in the infertile population. Human chromosome 9 is highly heteromorphic, and how its rearrangement affects male fertility remains to be fully investigated. In this study, we aimed to investigate the association between the polymorphic rearrangements of chromosome 9 and male infertility via an Italian cohort of male infertile patients. Cytogenetic analysis was carried out, along with Y microdeletion screening, semen analysis, fluorescence in situ hybridization, and TUNEL assays using spermatic cells. Chromosome 9 rearrangements were observed in six patients: three of them showed a pericentric inversion, while the others showed a polymorphic heterochromatin variant 9qh. Of these, four patients exhibited oligozoospermia associated with teratozoospermia, along with a percentage of aneuploidy in the sperm of above 9%, in particular, an increase in XY disomy. Additionally, high values for sperm DNA fragmentation (≥30%) were observed in two patients. None of them had microdeletions to the AZF loci on chromosome Y. Our results suggest that polymorphic rearrangements of chromosome 9 might be associated with abnormalities in sperm quality due to incorrect spermatogenesis regulation.

Semen Thresholds of Normality Established by the WHO Do Not Reveal Genome Instability-A Potential Occult Male Factor

Semen parameters are unable to inform on the function or fertilizing capacity of the male gamete. Standardized methods are provided by the WHO but, the lower reference limits have reduced sensitivity to predict chances of conception. Subfertile men may be falsely classified as "normal" and a male factor contributing to genome instability may be overlooked. Semen parameters, sperm DNA fragmentation (SDF), sperm chromatin maturity and stability, and sperm aneuploidy were assessed in fertile (F), subfertile normozoospermic (SN) and subfertile non-normozoospermic males (SN-N). Standardized assays employing flow cytometry were used to detect genome instability. Sperm DNA fragmentation did not differ significantly whether the semen samples were from a fertile (F), subfertile normozoospermic (SN) or subfertile non-normozoospermic male (SN-N). Chromatin decondensation was significantly reduced and hyperstability significantly increased in the SN group as compared to the F group. The frequency of diploidy was significantly different in the three study groups with significance between F and SN and between F and SN-N groups. Subfertile men with normal semen parameters are often excluded from extensive genetic testing. Genome instability might be an independent attribute of semen quality detecting problems not seen with semen analysis alone.

Klinefelter syndrome: etiology and clinical considerations in male infertility†

Klinefelter syndrome (KS) is the most prevalent chromosomal disorder occurring in males. It is defined by an additional X chromosome, 47,XXY, resulting from errors in chromosomal segregation during parental gametogenesis. A major phenotype is impaired reproductive function, in the form of low testosterone and infertility. This review comprehensively examines the genetic and physiological factors contributing to infertility in KS, in addition to emergent assisted reproductive technologies, and the unique ethical challenges KS patients face when seeking infertility treatment. The pathology underlying KS is increased susceptibility for meiotic errors during spermatogenesis, resulting in aneuploid or even polyploid gametes. Specific genetic elements potentiating this susceptibility include polymorphisms in checkpoint genes regulating chromosomal synapsis and segregation. Physiologically, the additional sex chromosome also alters testicular endocrinology and metabolism by dysregulating interstitial and Sertoli cell function, collectively impairing normal sperm development. Additionally, epigenetic modifications like aberrant DNA methylation are being increasingly implicated in these disruptions. We also discuss assisted reproductive approaches leveraged in infertility management for KS patients. Application of assisted reproductive approaches, along with deep comprehension of the meiotic and endocrine disturbances precipitated by supernumerary X chromosomes, shows promise in enabling biological parenthood for KS individuals. This will require continued multidisciplinary collaboration between experts with background of genetics, physiology, ethics, and clinical reproductive medicine.

Nuclear sperm integrity and ICSI prognosis in Tunisian patients with MMAF syndrome (multiple morphological abnormalities of the sperm flagella)

Multiple Morphological Abnormalities of the Sperm Flagella (MMAF) is a severe form of teratozoospermia associated with several sperm flagellar abnormalities. The study included 52 patients with MMAF syndrome and a control group of 25 fertile men. The impact of nuclear sperm quality on intracytoplasmic sperm injection (ICSI) results was studied in 20 couples. TUNEL assay was used to assess sperm DNA fragmentation and aniline-blue staining was used to assess chromatin condensation. To investigate chromosomal meiotic segregation, we used fluorescence in situ hybridization (FISH). Semen morphology analysis revealed a mosaic of multiple flagella morphological abnormalities, including 46.73% short flagella, 16.22% bent flagella, 22.07% coiled flagella, and 10.90% absent flagella, all of which were associated with a high percentage of sperm head abnormalities. The mean DNA fragmentation index was substantially higher in patients compared to controls (p = 0.001), whereas the rate of aniline blue-reacted spermatozoa was not significantly different. There was a significant difference in aneuploidy frequencies between the two groups (p < 0.05). Infertile males with MMAF syndrome had lower sperm nuclear quality, which affected ICSI results. As a result, better sperm selection procedures are being employed to increase the success rate of assisted reproductive technologies (ART).