Flow cytometry of human semen: a preliminary study of a non-invasive method for the detection of spermatogenetic defects

Evaluation of Sperm DNA Fragmentation Using Two Different Methods: TUNEL via Fluorescence Microscopy, and Flow Cytometry

Background and Objectives: Sperm DNA fragmentation refers to any break in one or both of the strands of DNA in the head of a sperm. The most widely used methodologies for assessing sperm DNA fragmentation are the sperm chromatin structure assay (SCSA), the sperm chromatin dispersion assay (SCD), the single-cell gel electrophoresis assay (SCGE-comet), and the terminal-deoxynucleotidyl-transferase (TdT)-mediated dUTP nick end labelling (TUNEL) assay. The aim of this study was to compare the efficiency and sensitivity of the analysis of sperm DNA fragmentation using TUNEL via fluorescence microscopy, and flow cytometry. Materials and Methods: Semen samples were collected and analyzed for standard characteristics using light microscopy, and for sperm DNA fragmentation using both TUNEL via fluorescence microscopy, and flow cytometry. Results: There were no significant differences in the values of the sperm DNA fragmentation index (DFI) obtained when the analysis was performed using TUNEL or flow cytometry (p = 0.543). Spearman's correlation analysis revealed a significant negative correlation between sperm motility (%) and sperm DNA fragmentation (p < 0.01), as well as between sperm concentration and sperm DNA fragmentation (p < 0.05). The Mann-Whitney U test showed no significant difference in the DFI among couples with repeated implantation failure (RIF) and miscarriages (p = 0.352). Conclusions: Both methods (TUNEL via fluorescence microscopy, and flow cytometry) have a high efficiency and sensitivity in accurately detecting sperm DNA fragmentation, and can be effectively used to assess male fertility.

Does detection of DDX4 mRNA in cell-free seminal plasma represents a reliable noninvasive germ cell marker in patients with nonobstructive azoospermia?

This study aimed to investigate the potential application of DDX4 gene expression in cell-free seminal mRNA as a noninvasive biomarker for the identification of the presence of germ cells in men with nonobstructive azoospermia and to correlate this factor with testicular biopsy. Male reproductive organ-specific genes were chosen: DDX4, which is a germ cell-specific gene and transglutaminase 4, which is a prostate-specific gene that was used as a control gene. Thirty-nine azoospermic males and twenty-eight normospermic fertile males (serving as a control group) participated in the study. Histopathological examination of testicular biopsies categorised azoospermic males into 20.5% with maturation arrest, 17.9% with incomplete Sertoli cell-only syndrome and 61.5% with complete Sertoli cell-only syndrome. Using real-time polymerase chain reaction, positivity for DDX4 gene was detected in 17 of 39 males with NOA which was due to maturation arrest in 35.3% (n = 6/17) of cases, due to incomplete Sertoli cell only in 23.5% (n = 4/17) and due to complete Sertoli cell only in 41.2% (n = 7/17). The study recommends joint utilisation of molecular transcripts as noninvasive biomarkers and histopathological examination of testicular biopsies in management of cases with azoospermia of the nonobstructive type.

Molecular analysis of testis biopsy and semen pellet as complementary methods with histopathological analysis of testis in non-obstructive azoospermia

PURPOSE

Non-obstructive azoospermia (NOA) is one the many causes of male infertility (10 %) resulting from testicular failure. Multiple testicular biopsies fail to find mature sperm in at least 50 % of cases Therefore; hunting for sensitive and specific biomarkers of spermatogenesis that could better determine the fertility status in NOA can lead to improved management of male infertility. Therefore, we evaluated sperm production through analyses of germ cell-specific transcripts (DAZ, TSPY1, SPTRX3 and SPTRX1) in semen and testicular biopsies of men with azoospermia.

METHODS

We collected semen (N=83) and testis biopsies (N=31) from men with non-obstructive azoospermia. We later extracted RNA and synthesized cDNA using washed semen precipitate and testicular tissues. We also performed semi-nested PCR with designed specific primers. Using H&E method, an expert pathologist performed the histopathological evaluation. Having categorized the patients into three groups based on histopathological results, we calculated the agreement between molecular results of semen and tissues with histopathological findings for each patient using Kappa statistical test.

RESULTS

Molecular findings of precipitated semen and testicular tissues were in disagreement with histopathological results in most cases. Molecular analysis of testis biopsies showed significant difference (Kappa coefficient=0.009, P value=0.894) with histopathological results; TSPY1, DAZ, SPTRX3 and SPTRX1 were respectively detected in 94 %, 94 %, 17.6 % and 52.9 % of men diagnosed with germ cell aplasia.

CONCLUSIONS

Molecular analysis of semen does not provide sufficient sensitivity and specificity to be used as a screening test at the present time, but it is a useful adjunct to histopathological methods in men with NOA. Spermatid/sperm specific transcripts indicated the possibility to find mature sperm following repeated multiple testicular sperm extraction (TESE) or microdisection TESE (mTESE).

Sperm flow cytometric parameters are associated with ICSI outcome

The association of sperm nuclear chromatin condensation and ploidy with embryo development and outcome after intracytoplasmic sperm injection (ICSI) was explored. The study population consisted of 16 couples referred to Ioannina University Medical School In vitro Fertilization Unit with male factor infertility and serious impairments in sperm nuclear chromatin condensation and ploidy, according to sperm flow cytometry. Additionally, 20 couples with male factor infertility and relatively high sperm flow cytometry parameters participated as controls. The 35 cycles of the study population were characterized by a lower fertilization rate (P<0.001) as well as decreased grade A embryo rate (P=0.004) and increased grade C embryo rate (P=0.028), compared with the 29 cycles of the control group. Additionally, a significantly elevated arrested embryo rate (P<0.001) and a decreased clinical pregnancy rate (P<0.020) were observed in the couples of the study population. Consequently, high levels of sperm nuclear chromatin condensation abnormalities and sperm aneuploidies are probably associated with lower fertilization rates, impaired embryo quality, elevated arrested embryo rates and decreased pregnancy rates. These preliminary results strongly support the use of sperm flow cytometry as a potential prognostic tool of ICSI outcome.

Assessment of sperm chromatin condensation and ploidy status using flow cytometry correlates to fertilization, embryo quality and pregnancy following in vitro fertilization

PURPOSE

Sperm flow cytometry (SFC) was used to evaluate the association of sperm chromatin condensation and ploidy with fertilization, embryo development, pregnancy and abortion rates following IVF.

METHODS

Conventional semen analysis was performed in one hundred fifty men, as well as SFC analysis, after acridine orange and propidium iodide staining, for the evaluation of sperm maturity and ploidy respectively. Conventional IVF was performed in all couples.

RESULTS

Couples with low percentages of mature spermatozoa presented with lower fertilization rates (p < 0.005), lower rates of grade A embryos (p < 0.003) and lower pregnancy rates (p < 0.006), compared to couples with high percentages of mature spermatozoa. Couples with low total aneuploidy rates presented with higher fertilization rates (p < 0.007), higher rates of grade A embryos (p < 0.004) and higher pregnancy rates (p < 0.003), compared to couples with high total aneuploidy rates.

CONCLUSIONS

Sperm chromatin condensation and ploidy constitute critical parameters for the evaluation of semen samples before IVF and for the identification of cases in need of ICSI application.

Equine sperm nuclei with different ploidy levels: relationship between the nuclear DNA content and the nuclear area

The aims of this study were to estimate the ability of the Feulgen reaction to identify equine sperm nuclei with different ploidy levels, to determine the frequency of haploid, diploid and polyploid sperm nuclei in the semen of fertile equines and to evaluate the relationship between the nuclear DNA content and the nuclear area. Determination of the ploidy level of Feulgen-stained spermatozoa using a scanning microspectrophotometer was very similar to the subjective estimations made with a light microscope. This indicates that the Feulgen reaction is a simple, inexpensive and reliable technique to recognise the ploidy level of equine spermatozoa. The incidence of diploid and polyploid spermatozoa, determined with a light microscope in 11 fertile equines, was 0.17 ± 0.08% and 0.027 ± 0.027% respectively. DNA content values obtained by microspectrophotometry in the only equine that presented polyploid spermatozoa allowed us to discriminate between haploid, diploid and polyploid subpopulations. Measurement of the nuclear area discriminated only two subpopulations: one including the haploid and diploid subpopulations and the other including the polyploid one. The similarity between the area of the haploid and diploid sperm nuclei suggests that the increase in DNA content is anisotropic, with a privileged direction of growth perpendicular to the nuclear flattening plane.

Effect of alcohol consumption on CpG methylation in the differentially methylated regions of H19 and IG-DMR in male gametes: implications for fetal alcohol spectrum disorders

BACKGROUND

Exposure to alcohol in utero is the main attributable cause of fetal alcohol spectrum disorders (FASD) which in its most severe form is characterized by irreversible behavioral and cognitive disability. Paternal preconception drinking is not considered to be a significant risk factor, even though animal studies have demonstrated that chronic paternal alcohol consumption has a detrimental effect on the physical and mental development of offspring even in the absence of in utero alcohol exposure. It has been documented that alcohol can reduce the levels and activity of DNA methyltransferases resulting in DNA hypomethylation and that reduced methyltransferase activity can cause activation of normally silenced genes. The aim of this study was to establish a link between alcohol use in men and hypomethylation of paternally imprinted loci in sperm DNA in genomic regions critical for embryonic development, thus providing a mechanism for paternal effects in the aetiology of FASD.

METHODS

Sperm DNA from male volunteers was bisulfite treated and the methylation patterns of 2 differentially methylated regions (DMRs), H19 and IG-DMR, analyzed following sequencing of individual clones. The methylation patterns were correlated with the alcohol consumption levels of the volunteer males.

RESULTS

There was a pattern of increased demethylation with alcohol consumption at the 2 imprinted loci with a significant difference observed at the IG-DMR between the nondrinking and heavy alcohol consuming groups. Greater inter-individual variation in average methylation was observed at the H19 DMR and individual clones were more extensively demethylated than those of the IG-DMR. CpG site #4 in the IG-DMR was preferentially demethylated among all individuals and along with the H19 DMR CpG site #7 located within the CTCF binding site 6 showed significant demethylation in the alcohol consuming groups compared with the control group.

CONCLUSION

This study demonstrates a correlation between chronic alcohol use and demethylation of normally hypermethylated imprinted regions in sperm DNA. We hypothesize that, should these epigenetic changes in imprinted genes be transmitted through fertilization, they would alter the critical gene expression dosages required for normal prenatal development resulting in offspring with features of FASD.

DNA flow cytometry of human spermatozoa: consistent stoichiometric staining of sperm DNA using a novel decondensation protocol

Rapid flow cytometric measurement of the frequency of aneuploid human sperms is in increasing demand but development of an exploitable method is hindered by difficulties of stoichiometric staining of sperm DNA. An aggressive decondensation protocol is needed after which cell integrity still remains intact. We used flow cytometry to examine the effect of lithium diiodosalicylate (LIS, chaotropic agent) on fluorescence intensity of propidium iodide-treated human spermatozoa from 10 normozoospermic men. When flow cytometric identification of diploid spermatozoa was achieved, validation was performed after sorting by three-color FISH. In contrast with the extremely variable histograms of nondecondensed sperms, consistent identification of haploid and diploid spermatozoa was possible if samples were decondensed with LIS prior to flow cytometry. A 76-fold enrichment of diploid sperms was observed in the sorted fractions by FISH. A significant correlation was found between the proportion of sorted cells and of diploid sperms by FISH. Application of LIS during the preparation of sperm for flow cytometry appears to ensure the stoichiometric staining of sperm DNA, making quantification of aneuploid sperm percentage possible. To our knowledge this is the first report in terms of separating spermatozoa with confirmedly abnormal chromosomal content. High correlation between the proportion of cells identified as having double DNA content by flow cytometry and diploid sperm by FISH allows rapid calculation of diploidy rate.

The presence of germ cells in the semen of azoospermic, cryptozoospermic and severe oligozoospermic patients: stringent flow cytometric analysis and correlations with hormonal status

OBJECTIVE

To understand the clinical significance of immature germ cells commonly found in ejaculates with low sperm counts by a novel and stringent flow cytometric quantitative method. PATIENTS/MEASUREMENTS: A total of 65 azoospermic, 38 cryptozoospermic and 42 severe oligozoospermic patients underwent routine hormone and semen analysis. Cells from each ejaculate were stained for DNA and mitochondria and analysed as spermatozoa (HC), round spermatids (1N), primary spermatocytes (4N) or diploid cells (2N).

RESULTS

About 90% of HC particles were eliminated as contaminants of the spermatozoa population by the analysis of their laser light scatter pattern and mitochondria staining intensity. Ploidy identification accuracy was improved by selection of singlets and elimination of cell aggregates for analysis. Distribution peaks for HC, 1N and 4N cells were displayed in 53%, 56% and 25% ejaculates, respectively, with prevalence in severe oligozoospermia > cryptozoospermia > azoospermia. 1N cell numbers were correlated with 4N and HC cells. For HC and 1N cells, the number/ejaculate and the incidence of distribution peaks were correlated with serum testosterone levels, and inversely with FSH for HC, 1N and 4N cells, suggesting that the abnormal shedding of 1N and 4N germ cells is the consequence rather than the cause of spermatogenic failure in these patients. Ploidy data bear no association with clinical diagnosis except for Klinefelter patients.

CONCLUSION

Whereas incidence of HC cells in azoospermic ejaculates may suggest minimal spermatogenic activity which evades detection by routine semen analysis, the presence of 1N and 4N cells in semen of patients provides noninvasive information about their spermatogenic status.

A new multiparameter flow cytometric method for human semen analysis

BACKGROUND

The objectives of this study were (i) to evaluate whether the combined use of Syto 16 and 7-amino-actinomycin-D (7-AAD) allows the detection of sperm apoptosis and (ii) to describe a new multiparameter flow cytometric method to assess simultaneously sperm concentration (SC), viability and apoptosis as well as leukocyte concentration.

METHODS

Semen samples from 68 patients were evaluated according to World Health Organization (WHO) criteria (normal, n=26; abnormal, n=42). The detection of activated caspases before and after betulinic acid (BA) incubation was carried out in 13 semen samples by flow cytometry using fluorescein-labelled inhibitors of caspases (FLICA). A multiparameter flow cytometric analysis was performed in 55 semen samples. Fluorescent microspheres were used to assess SC. Sperm apoptosis was detected by staining sperm with Syto 16 and 7-AAD. Leukocytes were counted using monoclonal anti-CD45.

RESULTS

A significant correlation between the percentage of the spermatozoa with low Syto 16 fluorescence and the percentage of spermatozoa containing activated caspases was found (r=0.68, P=0.0106; n=13). After incubation with BA, an increase of the percentage of apoptotic cells was observed in all samples, using both the Syto 16/7-AAD and the caspase activation methods. There was a good correlation between flow cytometry and optical microscopy for sperm (r=0.98, P < 0.0001) and leukocyte counting (r=0.64, P <0.0001). The percentage of apoptotic sperm was inversely correlated with both SC (r=-0.303, P=0.0246) and morphology (r=-0.384, P=0.0050) but not with motility.

CONCLUSIONS

The combination of Syto 16/7-AAD provides a sensitive assay to detect sperm apoptosis. The multiparameter flow cytometric method described offers the possibility of a simultaneous, simple, rapid and accurate assessment of several semen parameters.