DNA strand breaks in human sperm cells: a comparison between men with normal and oligozoospermic sperm samples

BACKGROUND: The aim of this report was to compare the degree of DNA strand breaks in known normal fertile men to those with oligozoospermia, and evaluate the presence of DNA strand breaks in normal raw sperm, after Percoll and swim-up and following conventional cryopreservation, as all these preparation methods might differ in selection of healthy sperm cells. METHODS: Sperm samples from proven fertile sperm donors (n=20) and infertile men with oligozoospermia (n=33) were tested for the presence of DNA strand breaks in the spermatozoa, by direct immunoperoxidase detection of digoxigenin-labeled genomic DNA. A correlation to other sperm parameters, sperm counts, motility and Krüger's strict criteria was performed. RESULTS: DNA strand breaks were found significantly more often in sperm samples from men with oligozoospermia compared to sperm samples of normal fertile men. The degree of spermatozoa with DNA strand breaks was correlated proportional with the degree of morphological pathological sperm cells judged by Krüger's strict criteria. The percentage of spermatozoa with DNA strand breaks in the samples was not influenced by procedures such as the swim-up technique, Percoll gradients or cryopreservation and thawing. CONCLUSION: DNA strand breaks were found significantly more often in men with oligozoospermia compared to normospermic men. The DNA strand breaks might play an important role for the maturation process of the spermatozoa in the same way as apoptosis is controlling the number of early meiotic germ cells in the testis, and hereby play an important role in advanced fertility treatments (ICSI).     

DNA strand breaks in human spermatozoa: correlation with fertilization in vitro in oligozoospermic men and in men with unexplained infertility

BACKGROUND: The purpose of this study was to examine the correlation between DNA strand breaks in human spermatozoa and semen quality, fertilization rate and IVF outcome. METHODS: A total of 50 men suffering from unexplained infertility and 50 men with oligozoospermia undergoing IVF treatment entered a prospective study. Sperm samples were assessed according to the WHO manual and for the presence of DNA strand breaks in spermatozoa. The study was blinded for the technician involved in assessment of DNA strand breaks. IVF was carried out according to a long down regulation protocol using GnRH, FSH and hCG. The ova were inseminated with 200,000 spermatozoa/ml. Embryos were transferred on day 2 after fertilization with a maximum of three embryos. RESULTS: This study demonstrates a negative correlation between the proportion of spermatozoa having DNA strand breaks and the proportion of oocytes fertilized after IVF. CONCLUSION: The number of human spermatozoa with DNA strand breaks is a good predictor for fertilization rate in couples suffering from unexplained infertility and undergoing IVF treatment.     

The role of DNA strand breaks in human spermatozoa used for IVF and ICSI

BACKGROUND: The objective of this study was to determine the incidence of spermatozoa with DNA strand breaks in four clinically different groups of infertile couples, and to correlate DNA damage with other semen analysis parameters, as well as fertilization rates and IVF outcome. METHODS: One group consisted of 75 men where the female partners had a tubal obstruction, Group A. Fifty sperm samples were collected from men in unexplained infertile couples, Group B. Fifty men with oligozoospermia and IVF made up Group C. Finally, 61 men with oligozoospermia and where ICSI was performed made up Group D. Sperm samples were assessed according to the WHO manual and for the presence of DNA strand breaks in spermatozoa. The study was blinded for the technician involved in the assessment of DNA strand breaks. IVF was carried out according to a long down regulation protocol using GnRH, FSH and hCG. Embryos were transferred on day 2 after fertilization with a maximum of three embryos. RESULTS: This study demonstrated a negative correlation between the proportion of spermatozoa having DNA strand breaks and the proportion of oocytes fertilized after IVF (p<0.01). Furthermore, the number of spermatozoa with DNA strand breaks was important for the pregnancy rate in the group of unexplained infertile couples. After ICSI no association was found between spermatozoa with DNA strand breaks and fertilization rates (p>0.05). CONCLUSION: DNA strand breaks in human spermatozoa impairs fertilization in both unexplained infertile couples and those with oligozoospermia and IVF. However, after ICSI, this impact of DNA strand breaks were not seen. This creates a specific indication and treatment for this new diagnosed group of otherwise unexplained infertile men.     

Clinical significance of sperm DNA damage threshold value in the assessment of male infertility

Sperm DNA integrity is a prerequisite for normal spermatozoal function. The aim of the study was to evaluate the role of sperm chromatin damage, its cut-off level and its effect on sperm parameters in men with idiopathic infertility by analyzing 100 idiopathic infertile men and 50 fertile controls. Semen samples were analyzed as per WHO 1999 guidelines and sperm chromatin structure assay (SCSA) was applied to measure DNA fragmentation index (DFI) in sperm. The mean DFI of infertile men (35.75) was significantly (P < .0001) higher as compared to controls (26.22). The threshold level of 30.28% was obtained as cut-off value to discriminate infertile men from fertile controls. Sperm count, forward motility, and normal morphology found to be negatively associated with DFI in overall study subjects. Infertile men with severe oligozoospermia had higher mean DFI (40.01 ± 11.31) than infertile men with oligozoospermia (35.11 ± 10.05) and normal sperm count (33.99 ± 9.96). Moreover 64% of infertile men have DFI > 30 against 6% of fertile controls (P < .0001). Higher sperm DNA fragmentation may be the underlying cause for poor semen quality in idiopathic infertile men and the threshold value of 30.28% is a clear discriminator to distinguish infertile men from fertile men of Indian population. Thus, DFI is a good prognostic marker as cases with higher sperm DFI may have poor success rate even after assisted conception and may experience recurrent pregnancy loss (RPL) and should be counseled accordingly.     

Sperm morphology and IVF: embryo quality in relation to sperm morphology following the WHO and Krüger's strict criteria.

BACKGROUND: The aim of this study was to examine the correlation between sperm morphology and embryo quality/IVF outcome. METHODS: The implication of sperm morphology assessment before an IVF cycle was evaluated. A total of 100 IVF couples where the female partner had either tubal factor (n=50) or unexplained infertility (n= 50) entered a prospective study, and sperm samples for the actual cycle were assessed according to the strict criteria and WHO criteria. The study was blinded for the technician involved in sperm morphology analyzing. IVF was carried out according to a long down regulation protocol using GnRH/FSH/hCG and ova were inseminated with 200,000 spermatozoa/ml. Embryos were transferred on day 2 post fertilization in a maximum of three embryos. RESULTS: No significant differences were found between the groups regarding age of the female partner (mean=34.3), no. oocytes retrieved (mean=8.5), fertilization (66.5%), pregnancies (pos. S-hCG/transfer 39.6%) or 'Take home baby rate' (birth rate/transfer 30.0%). As to the score of Krüger's strict criteria and the WHO criteria, we found no correlation between this score and cleavage rate, embryo development or pregnancies. The WHO criteria were found to be a better predictor for fertilization rate than the Krüger's criteria (p<0.002). CONCLUSION: The strict criteria or sperm evaluation according to WHO have no better predictive value for the outcome of routine IVF.     

Morphology of spermatozoa used in IVF and ICSI from oligozoospermic men

The purpose of this study was to determine morphology in human spermatozoa from men with oligozoospermia and correlate with the fertilization rate, embryo score and pregnancy rate after IVF and intracytoplasmic sperm injection (ICSI) respectively. The study group consisted of 125 couples where the male partner suffered from oligozoospermia. Fifty of these had IVF (group A). Seventy-five couples in whom ICSI had been performed made up group B. Sperm samples were assessed according to the WHO manual. For each male, morphology of spermatozoa was judged according to Krüger's strict criteria, WHO criteria and the teratozoospermia index (TZI). Oocyte monitoring was carried out according to a long down-regulation protocol using gonadotrophin-releasing hormone, recombinant FSH and human chorionic gonadotrophin. Embryos were transferred on day 2 after fertilization, with a maximum of three embryos. This study demonstrated no correlation between any of the morphological assessments of spermatozoa and the fertilization rate, embryo score and pregnancy rate, either after IVF or ICSI. Morphology in human spermatozoa according to Krüger's strict criteria, WHO criteria and the TZI had no predictive value for the outcome after either IVF or ICSI.     

Correlations between two markers of sperm DNA integrity, DNA denaturation and DNA fragmentation, in fertile and infertile men

OBJECTIVE: To evaluate two different assays of human sperm DNA integrity, DNA denaturation (DD) and DNA fragmentation (DF), and to correlate these with standard semen parameters. DESIGN: Prospective, observational study. SETTING: University infertility clinic.Patient(s): Forty consecutive semen samples from 33 nonazoospermic men presenting for infertility evaluation and 7 fertile men presenting for vasectomy. Intervention(s): Assessment of sperm concentration, motility, morphology, DD and DF. MAIN OUTCOME MEASURE(S): Sperm DD and DF in fertile and infertile men. RESULT(S): The mean (+/-SE) rates of DD and DF were significantly higher in infertile subjects compared to fertile controls, respectively: 25.4 +/- 3.0 vs. 10.2 +/- 2.3 (P=.028) and 27.6 +/- 2.5 vs. 13.3 +/- 2.5% (P=.016). DF and DD correlated strongly (r = 0.71, P<.0001). Also, DD and DF correlated negatively with standard semen parameters (concentration, motility, and morphology), the strongest correlation being with sperm motility. CONCLUSION(S): The strong correlation between sperm DD and DF, and the higher levels of sperm DNA damage in infertile compared with fertile men, indicate that male infertility is associated with poor sperm DNA integrity. Although infertile men may father children with assisted conception, fertilization with DNA-damaged spermatozoa may increase the risk of genetic disease in the offspring.     

The presence of abnormal spermatozoa in the ejaculate: did apoptosis fail?

With the successful use of Assisted Reproduction, in particular intracytoplasmic sperm injection (ICSI), to treat infertile couples we have become less discriminating with the quality of spermatozoa we use to treat our patients. Numerous studies have shown the presence of nuclear DNA strand breaks in human ejaculated spermatozoa. The reason why human spermatozoa, in particular from men with abnormal semen parameters, possess these abnormalities in their nuclear DNA is still not clear. Two processes that have been linked to the presence of nuclear DNA strand breaks in spermatozoa are anomalies in apoptosis during spermatogenesis or problems in the packaging of the chromatin during spermiogenesis. Understanding the mechanisms responsible for producing abnormal spermatozoa in the human will improve our knowledge about certain causes of male infertility. More importantly, the impact of such sperm, if selected to perform ICSI, needs to be better understood so that any detrimental paternal effects can be avoided.     

DNA fragmentation in human spermatozoa: significance in the diagnosis and treatment of infertility

The integrity of the paternal genome is of paramount importance in the initiation and maintenance of a pregnancy in vivo and in vitro. The presence in the embryonic genome of chemical modifications at the level of DNA nucleotides and/or DNA strand breaks coming from the paternal genome (that have not been repaired by the oocyte after fertilization), is not compatible with normal embryo and fetal development. DNA fragmentation in human spermatozoa has been recently shown to be an important contributing factor to the etiology of unexplained infertility. In this review, the mechanisms responsible for DNA fragmentation in sperm, including defects in chromatin remodeling during the process of spermiogenesis, apoptosis and ROS-induced damage during sperm migration from the seminiferous tubules to the epididymis, are discussed. Also, the different methodologies used to determine DNA fragmentation in human sperm (with special emphasis on the SCSA test) and the applications of the SCSA test in the diagnosis and treatment of infertility, are presented. Finally, answers to common questions asked about the SCSA test are also included.     

Round-headed spermatozoa in semen specimens from fertile and subfertile men

OBJECTIVE: To investigate the frequency of round-headed, or acrosomeless, spermatozoa, determine the percentage and evaluate the possible correlation with other semen parameters. STUDY DESIGN: Semen specimens from 114 subfertile men aged 24-53 years (mean +/- SD 33.3 +/- 6.3) and from 60 fertile men aged 24-44 years (33.1 +/- 4.2) were studied. Two semen specimens were examined from each individual, with a six- to eight-week interval. Sperm morphology was evaluated from Papanicolaou-stained smears, and the classification of abnormal sperm forms was made according to WHO guidelines. RESULTS: The percentage of round-headed spermatozoa was 2.3% +/- 0.5 in subfertile and 0.5% +/- 0.1 in fertile men. Round-headed spermatozoa existed in semen specimens from 36.8% of subfertile and 25.0% fertile men. Of subfertile men, 14.9% had round-headed spermatozoa at a higher percentage than the highest normal limit found in sperm smears from fertile men. CONCLUSION: In some subfertile men with a high percentage of round-headed spermatozoa, infertility could be attributed to the cause of this morphologic abnormality. Moreover, morphologic abnormalities in the neck were significantly more frequent in round-headed spermatozoa than in spermatozoa with normal heads.     

Origin of DNA damage in ejaculated human spermatozoa

The molecular basis of many forms of male infertility is poorly defined. One area of research that has been studied intensely is the integrity of the DNA in the nucleus of mature ejaculated spermatozoa. It has been shown that, in men with abnormal sperm parameters, the DNA is more likely to possess strand breaks. However, how and why this DNA damage originates in certain males and how it may influence the genetic project of a mature spermatozoon is unknown. Two theories have been proposed to describe the origin of this DNA damage in mature spermatozoa. The first arises from studies performed in animal models and is linked to the unique manner in which mammalian sperm chromatin is packaged, while the second attributes the nuclear DNA damage in mature spermatozoa to apoptosis. One of the factors implicated in sperm apoptosis is the cell surface protein, Fas. In this review, we discuss the possible origins of DNA damage in ejaculated human spermatozoa, how these spermatozoa arrive in the ejaculate of some men, and what consequences they may have if they succeed in their genetic project.     

Clinical relevance of sperm DNA damage in assisted reproduction

Many studies have shown how a 'paternal effect' can cause repeated assisted reproduction failures. In particular, with increasing experience of intracytoplasmic sperm injection (ICSI), it became evident that spermatozoa from some patients repeatedly fail to form viable embryos, although they can fertilize the oocyte and trigger early preimplantation development. Many authors have shown how this paternal effect can be traced back to anomalies in sperm chromatin organization: the spermatozoa of subfertile men are characterized by numerical abnormalities in spermatozoal chromosome content, Y chromosome microdeletions, alterations in the epigenetic regulation of paternal genome and non-specific DNA strand breaks. In particular, pathologically increased sperm DNA fragmentation is one of the main paternal-derived causes of repeated assisted reproduction failures in the ICSI era. The intention of this review is to describe nuclear sperm DNA damage, with emphasis on its clinical significance and its relationship with male infertility. Assessment of sperm DNA damage appears to be a potential tool for evaluating semen samples prior to their use in assisted reproduction, helping to select spermatozoa with intact DNA or with the least amount of DNA damage for use in assisted conception.     

Headless spermatozoa in semen specimens from fertile and subfertile men.

OBJECTIVE: To investigate the frequency of headless, or unnucleated, spermatozoa, determine its percentage and evaluate its possible correlation with other semen parameters. STUDY DESIGN: Semen specimens from 94 subfertile men, aged 24-53 years (mean +/- SD 33.3 +/- 6.3) and from 52 fertile men, aged 24-44 (33.3 +/- 4.1) were studied. Two semen specimens were examined from each individual, with a six- to eight-week interval. Sperm morphology was evaluated from Papanicolaou-stained smears, and the classification of abnormal sperm forms was made according to the guidelines of the World Health Organization. RESULTS: The percentage of headless spermatozoa was 9.0% +/- 8.8 in subfertile and 2.7% +/- 3.1 in fertile men. Headless spermatozoa existed in semen specimens from 90% of subfertile and 70% of fertile men. Of subfertile men, 23.4% had headless spermatozoa at a higher percentage than the highest normal limit found in sperm smears from fertile men. CONCLUSION: In some cases of subfertile men with a high percentage of headless spermatozoa, their infertility can be attributed to the cause of this morphological abnormality. Moreover, tails but not heads were found in semen specimens from subfertile and fertile men.     

Role of mitotic control in spermatogenesis

OBJECTIVE: To study the correlation between the incidence of sex chromosome aneuploidies in the somatic cells and spermatozoa in karyotypically normal infertile men and fertile donors. DESIGN: A prospective, phase two, controlled study. SETTING: A teaching Hospital Reproductive Medicine and Medical Genetics Units. PATIENT(S): Ten patients with idiopathic oligozoospermia and 10 sperm donors with proven fertility, all with a normal karyotype 46, XY. INTERVENTION(S): Multicolor fluorescence in situ hybridization (FISH) of peripheral blood lymphocytes and spermatozoa using a probe cocktail containing the alpha satellite DXZ1 for the X centromere, DYZ1 for the heterochromatic region of the long arm of the Y, and cosmids D21S259, D21S341, and D21S342 for Down syndrome critical region of chromosome 21. MAIN OUTCOME MEASURE(S): The incidence of chromosome X, Y, and 21 aneuploidies in peripheral lymphocytes and spermatozoa in both groups. RESULT(S): The incidence of aneuploidies related to chromosomes X, Y, and 21 were significantly higher in peripheral lymphocytes and spermatozoa of infertile men compared with donors. There was a positive correlation between the incidence of chromosome aneuploidies in the somatic cells and sperm in all men. CONCLUSION(S): These findings provide suggestive evidence for the importance of mitosis in spermatogenesis and the role of mitotic instability in unexplained oligozoospermia.     

Assessment of DNA fragmentation of spermatozoa that were surgically retrieved from men with obstructive azoospermia

OBJECTIVE: To determine the degree of DNA fragmentation in spermatozoa of men with obstructive azoospermia or anejaculation compared with that of ejaculated spermatozoa from fertile donors. DESIGN: Observational study. SETTING; University Medical Center St. Radboud, Nijmegen. The Netherlands. PATIENT(S): Forty-one patients with obstructive azoospermia or anejaculation and 10 fertile donors. MAIN OUTCOME MEASURE(S): Sperm samples were obtained surgically from the epididymis or testis of men with azoospermia or anejeculation and by ejaculation in fertile patients. DNA fragmentation was analyzed in the total sample and in a motile fraction that was isolated as in routine ICSI procedures. DNA breaks were measured by using the TdT-mediated dUTP nick-end labeling assay. RESULT(S): A higher percentage of cells with DNA breaks was found in men with obstructive azoospermia or anejaculation compared with donors (mean, 18.9% vs. 6.2%). A significant lower degree of DNA fragmentation was observed in the motile fraction from patients compared with donors (0.4% vs. 0.6%). CONCLUSION(S): High percentages of cells with DNA damage were found in sperm samples from men with obstructive azoospermia or anejaculation, but a very low frequency of damage to the DNA was observed in the motile fraction. In an ICSI setting, the use of motile sperm retrieved from epididymis or testis of men with obstructive azoospermia does not seem to pose a higher genetic risk to the progeny than does use of motile ejaculated sperm.     

Extent of nuclear DNA damage in ejaculated spermatozoa impacts on blastocyst development after in vitro fertilization

OBJECTIVE: To determine whether the extent of ongoing apoptotic cell death measured as the presence of DNA strand breaks in spermatozoa affects embryo development to the blastocyst stage in IVF. DESIGN: A prospective comparative study. SETTING: A university IVF clinic and a private IVF clinic. PATIENT(S): Men (n = 49) undergoing infertility treatment with IVF. INTERVENTION(S): After density gradient centrifugation preparation, part of the sperm sample was used for infertility treatment, and the rest was fixed in paraformaldehyde. Strand breaks in DNA that are indicative of apoptosis were detected by the in situ DNA nick end labeling (TUNEL) technique. A total of 15,000 spermatozoa from each sample were evaluated for TUNEL reactivity by flow cytometry. MAIN OUTCOME MEASURE(S): Percentage of ejaculated spermatozoa with DNA strand breaks indicative of apoptosis, blastocyst development rate, and pregnancy rate. RESULT(S): Blastocyst development showed a significant negative correlation with percentage TUNEL positivity in spermatozoa. When 20% was used as a cutoff for TUNEL positivity in sperm samples, the percentage of blastocyst development was 50% higher in the <20% TUNEL-positivity group (n = 27) compared with those with >/=20% TUNEL positivity (n = 22; 44.7% blastocyst development vs. 29.8%). Clinical pregnancy rates in these two groups were 52% vs. 44%, respectively. CONCLUSION(S): The extent of nuclear DNA fragmentation in prepared ejaculated spermatozoa used in IVF negatively correlates with blastocyst development. A larger series of patients needs to be assessed to determine whether this paternal effect on blastocyst development may also affect pregnancy outcome.     

Sperm acrosin activity and fluorescence microscopic assessment of proacrosin/acrosin in ejaculates of infertile and fertile men.

OBJECTIVE: To compare biochemically active with immunoreactive sperm acrosin in fertile and infertile men. SETTING: This study was conducted in a tertiary care center, the Andrology Clinic, Department of Internal Medicine, University of L'Aquila. PATIENTS: We evaluated the males in 40 infertile couples with no recognized cause of female infertility and 20 fertile men. INTERVENTIONS: Ejaculates were collected under standardized conditions of abstinence. MAIN OUTCOME MEASURES: Total sperm acrosin activity was measured on a spectrophotometer in washed sperm stored at -80 degrees C for 1 to 6 days. The percent of spermatozoa immunostained by an antiserum against proacrosin/acrosin by indirect immunofluorescence (IFL) was determined on methanol fixed sperm smears. RESULTS: Biochemically active acrosin was correlated to immunoreactive acrosin (P = 0.0028), and both were inversely correlated to the percent of spermatozoa with an abnormal head (P = 0.00024 for acrosin activity and P = 0.0013 for IFL). Biochemically active and immunoreactive acrosin were lower in infertile compared with fertile men (P = 0.0012 and P = 0.0009, respectively). Sixty-eight percent of ejaculates with an acrosin activity lower than the limit value observed in fertile men showed a normal sperm morphology and a normal immunoreactivity for acrosin. CONCLUSIONS: A low sperm acrosin activity in teratospermic ejaculates is because of a lack or a defect of the immunogenic and functional domains of the protein. A low sperm acrosin in infertile men with normal semen parameters results from a possible functional defect of the enzyme that is immunohistochemically detected in spermatozoa.     

Defective function of a nongenomic progesterone receptor as a sole sperm anomaly in infertile patients.

OBJECTIVE: To compare the function of a novel nongenomic progesterone (P) receptor on the human sperm surface (mediating the P-induced acrosome reaction) in spermatozoa from fertile donors and from infertile patients. To examine the possible implication of defective P receptor function as an etiologic factor in unexplained male infertility. DESIGN: Progesterone binding and P effects were assessed in sperm from infertile patients and compared with corresponding parameters for sperm from healthy donors. SETTING: Private hospital, medical research center, and a university-based andrological laboratory. PATIENTS, PARTICIPANTS: Sperm samples were from infertile patients (no pathology detected in their wives) attending our infertility clinic and from healthy sperm donors. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Progesterone binding sites were visualized with a fluorescein-labeled protein-P conjugate. Indo 1-AM (a fluorescent indicator of intracellular free Ca2+) was used to measure P-induced Ca2+ influx. Progesterone-induced acrosome reaction was monitored after acrosomal staining with Pisum sativum agglutinin. RESULTS: Among 8 patient sperm samples with normal spermiogram values (of 53 examined), 5 showed a reduced percentage of P-binding spermatozoa and an abnormal response to the hormone in terms of Ca2+ influx and the acrosome reaction. CONCLUSIONS: Defective function of a sperm surface P receptor is described in some cases of male infertility. The observed fluorescence microscopic patterns of hormone binding may be used to further investigate receptor activity in unexplained male infertility.     

The significance of sperm nuclear DNA strand breaks on reproductive outcome

PURPOSE OF REVIEW: A growing body of evidence indicates that ejaculated spermatozoa from men being treated with intracytoplasmic sperm injection contain nuclear abnormalities. Many of these nuclear anomalies manifest themselves as breaks in the sperm nuclear DNA. This review examines the mechanisms involved in generating DNA strand breaks during spermatogenesis in the human, the main techniques used to assess the sperm nucleus and the evidence, in relation to assisted reproduction, showing that sperm nuclear DNA strand breaks may impact on reproductive outcome. RECENT FINDINGS: Techniques such as the TUNEL assay and the sperm chromatin structure assay both show increased levels of DNA abnormalities in spermatozoa from men who have poor semen parameters. The reproductive parameters affected by an increased presence of DNA abnormalities in ejaculated spermatozoa include fertilization, blastocyst development, and pregnancy rates. SUMMARY: There is accumulating evidence linking sperm nuclear DNA anomalies to poor reproductive outcome in relation to assisted reproduction technologies. The tests currently available only provide an inkling of the impact of sperm nuclear DNA abnormalities on reproductive outcomes. Although the impact an abnormal paternal genome may have on reproductive outcome is unquestionably less than that of its female counterpart, it cannot be ignored.     

Efficacy of a sperm-selection chamber in terms of morphology,aneuploidy and DNA packaging

Since most current techniques analysing spermatozoa will inevitably exclude these gametes from further use, attempts have been made to enrich semen samples with physiological spermatozoa with good prognosis using special sperm-processing methods. A particular sperm-selection chamber, called the Zech-selector, was found to be effective in completely eliminating spermatozoa with DNA strand breaks. The aim of this study was to further analyse the subgroup of spermatozoa accumulated using the Zech-selector. In detail, the potential of the chamber to select for proper sperm morphology, DNA status and chromatin condensation was tested. Two samples, native and processed semen, of 53 patients were analysed for sperm morphology (×1000, ×6300), DNA packaging (fragmentation, chromatin condensation) and chromosomal status (X, Y, 18). Migration time (the time needed for proper sperm accumulation) was significantly correlated to fast progressive motility (P = 0.002). The present sperm-processing method was highly successful with respect to all parameters analysed (P < 0.001). In particular, spermatozoa showing numeric (17.4% of patients without aneuploidy) or structural chromosomal abnormalities (90% of patients without strand-breaks) were separated most effectively. To summarize, further evidence is provided that separating spermatozoa without exposure to centrifugation stress results in a population of highly physiological spermatozoa.Since most current techniques analysing sperm quality will inevitably destroy the gamete, attempts have been made to enrich semen samples with physiological spermatozoa with good prognosis using special sperm-processing methods. A particular sperm-selection chamber, called Zech-selector, has been found to be effective in completely eliminating spermatozoa with DNA strand breaks. The study was set up in order to further analyse the subgroup of spermatozoa accumulated using the Zech-selector. In detail, the potential of the chamber to select for proper sperm morphology, DNA status and chromatin condensation was tested. Two samples, native and processed semen, from 53 patients were analysed for sperm morphology (×1000, ×6300), DNA packaging (DNA fragmentation, chromatin condensation), and chromosomal status (X, Y, 18). Migration time (the time needed for proper sperm accumulation) was found to be related to fast progressive motility. The present sperm-processing method was highly successful with respect to all parameters analysed. In particular, spermatozoa showing numeric (17.4% of patients without aneuploidy) or structural chromosomal abnormalities (90% of patients without strand breaks) were separated most effectively. To summarize, further evidence is provided that separating spermatozoa without exposure to centrifugation stress results in a population of highly physiological spermatozoa.