Sperm chromatin structure assay high DNA stainability sperm as a marker of early miscarriage after intracytoplasmic sperm injection

Gaussian clustering and quantification of the sperm chromatin dispersion test using convolutional neural networks

Sperm DNA fragmentation is a sign of sperm nuclear damage. The sperm chromatin dispersion (SCD) test is a reliable and economical method for the evaluation of DNA fragmentation. However, the cut-off value for differentiation of DNA fragmented sperms is fixed at 1/3 with limited statistical justification, making the SCD test a semi-quantitative method that gives user-dependent results. We construct a collection of deep neural networks to automate the evaluation of bright-field images for SCD tests. The model can detect valid sperm nuclei and their locations from the input images captured with a 20× objective and predict the geometric parameters of the halo ring. We construct an annotated dataset consisting of N = 3120 images. The ResNet 18 based network reaches an average precision (AP50) of 91.3%, a true positive rate of 96.67%, and a true negative rate of 96.72%. The distribution of relative halo radii is fit to the multi-peak Gaussian function (p > 0.99). DNA fragmentation is regarded as those with a relative halo radius 1.6 standard deviations smaller than the mean of a normal cluster. In conclusion, we have established a deep neural network based model for the automation and quantification of the SCD test that is ready for clinical application. The DNA fragmentation index is determined using Gaussian clustering, reflecting the natural distribution of halo geometry and is more tolerable to disturbances and sample conditions, which we believe will greatly improve the clinical significance of the SCD test.

Sperm chromatin structure assay (SCSA®) and flow cytometry-assisted TUNEL assay provide a concordant assessment of sperm DNA fragmentation as a function of age in a large cohort of approximately 10,000 patients

BACKGROUND

Sperm DNA integrity is increasingly seen as a critical characteristic determining reproductive success, both in natural reproduction and in assisted reproductive technologies (ART). Despite this awareness, sperm DNA and nuclear integrity tests are still not part of routine examinations for either infertile men or fertile men wishing to assess their reproductive capacity. This is not due to the unavailability of DNA and sperm nuclear integrity tests. On the contrary, several relevant but distinct tests are available and have been used in many clinical trials, which has led to conflicting results and confusion. The reasons for this are mainly the lack of standardization between different clinics and between the tests themselves. In addition, the small number of samples analyzed in these trials has often weakened the value of the analyses performed. In the present work, we used a large cohort of semen samples, covering a wide age range, which were simultaneously evaluated for sperm DNA fragmentation (SDF) using two of the most frequently used SDF assays, namely the TUNEL assay and the sperm chromatin structure assay (SCSA®). At the same time, as standard seminal parameters (sperm motility, sperm morphology, sperm count) were available for these samples, correlations between age, SDF and conventional seminal parameters were analyzed.

RESULTS

We show that the SCSA® and TUNEL assessments of SDF produce concordant data. However, the SDF assessed by TUNEL is systematically lower than that assessed by SCSA®. Regardless of the test used, the SDF increases steadily during aging, while the HDS parameter (High DNA stainability assessed via SCSA®) remains unchanged. In the cohort analyzed, conventional sperm parameters do not seem to discriminate with aging. Only sperm volume and motility were significantly lower in the oldest age group analyzed [50-59 years of age].

CONCLUSIONS

In the large cohort analyzed, SDF is an age-dependent parameter, increasing linearly with aging. The SCSA® assessment of SDF and the flow cytometry-assisted TUNEL assessment are well correlated, although TUNEL is less sensitive than SCSA®. This difference in sensitivity should be taken into account in the final assessment of the true level of fragmentation of the sperm nucleus of a given sample. The classical sperm parameters (motility, morphology, sperm count) do not change dramatically with age, making them inadequate to assess the fertility potential of an individual.

Clinical parameters associated with altered sperm DNA fragmentation index among primary infertile men: Findings from a real-life cross-sectional study

BACKGROUND

Recurrent pregnancy loss and unexplained infertility are the current indications to test sperm DNA fragmentation according to the European Association of Urology Guidelines on sexual and reproductive health.

OBJECTIVE

To identify a novel and better performing model to diagnose primary infertile men presenting with altered sperm DNA fragmentation and to outline its predictive ability in respect to current European Association of Urology Guidelines' recommendations.

MATERIALS AND METHODS

Data from the latest 515 consecutive primary infertile men as for World Health Organization criteria were analyzed. Semen analysis, sperm DNA fragmentation (according to sperm chromatin structure assay), and serum hormones were considered in every patient. Altered sperm DNA fragmentation was defined with levels greater than 30%. Descriptive statistics was applied to compare patients with normal versus SDF > 30%. The new predicting model was identified through logistic regression analysis exploring potential predictors of SDF > 30% at first clinical presentation. Diagnostic accuracy between the two predictive models (European Association of Urology Guidelines vs. new) was assessed, and decision curve analyses tested their clinical benefit.

RESULTS

Of 515, 268 (51.9%) patients had SDF > 30% at clinical presentation. Patients with SDF > 30% were older (median [interquartile range] 39 [35-43] vs. 37 [34-41] years), had lower mean testicular volume (Prader 15 [12-20] vs. 17.5 [13.5-20] and lower total motile sperm count (1.80 [0.7-13.2] vs. 11.82 [4.2-44.5] × 106 ), all p < 0.001. No other clinical differences were depicted. The two groups showed similar rates of history of recurrent pregnancy loss and unexplained infertility. At multivariable logistic regression analysis, age more than 38 years (odds ratio: 2.43) and baseline total motile sperm count less than 20 × 106 (odds ratio: 3.72) were associated with SDF > 30%, after adjusting for Prader < 15, history of miscarriages and unexplained infertility, all p < 0.0001. The newly identified model (unexplained infertility + history of poli-abortions + Prader < 15 + age ≥38 years + total motile sperm count <20 × 106 ) showed higher accuracy to identify SDF > 30% at baseline in respect to European Association of Urology Guidelines (area under the curve: 72.1 vs. 52.7), with superior clinical net benefit use.

CONCLUSIONS

The application of the European Association of Urology sexual and reproductive health guidelines does not ensure proper identification of primary infertile men with pathological sperm DNA fragmentation. We propose a novel and better performing predictive model to identify the infertile men with altered sperm DNA fragmentation at first clinical assessment.

DISCUSSION

As altered sperm DNA fragmentation has been widely linked with the inability to conceive, this second-level test could be further implemented over the diagnostic workup of a broader subset of patients presenting for male factor infertility. We propose a better performing model to identify this specific category of patients.

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.

Physiological intracytoplasmic sperm injection does not improve the quality of embryos: A cross-sectional investigation on sibling oocytes

OBJECTIVE

This study aimed to compare the efficacy of physiological intracytoplasmic sperm injection (PICSI) and intracytoplasmic sperm injection (ICSI) in terms of the fertilization rate and embryo quality using sibling oocyte cycles.

METHODS

This prospective, cross-sectional study collected data from 76 couples who underwent their first cycle at the Hue Center for Reproductive Endocrinology and Infertility, Vietnam, between May 2019 and November 2021. The inclusion criteria were cycles with at least eight oocytes and a sperm concentration of 5×106/mL. Sperm parameters, sperm DNA fragmentation (SDF), fertilization, and the quality of cleavage-stage embryos on day 2 and blastocysts on day 5 were examined.

RESULTS

From 76 ICSI cycles, 1,196 metaphase II (MII) oocytes were retrieved, half of which were randomly allocated to either the PICSI (n=592) or ICSI (n=604) treatment group. The results showed no significant difference between the two groups in terms of fertilization (72.80% vs. 75.33%, p=0.32), day 2 cleavage rate (95.13% vs. 96.04%, p=0.51), blastulation rate (52.68% vs. 57.89%), and high-quality blastocyst rate (26.10% vs. 31.13%, p=0.13). However, in cases where SDF was low, 59 cycles consisting of 913 MII oocytes produced a considerably higher blastulation rate with PICSI than with ICSI (50.49% vs. 35.65%, p=0.00). There were no significant differences between the pregnancy outcomes of the PICSI and ICSI embryo groups following embryo transfer.

CONCLUSION

Using variable sperm quality provided no benefit for PICSI versus ICSI in terms of embryo outcomes. When SDF is low, PICSI appears to be able to produce more blastocysts.

Density Gradient Centrifugation Alone or the Combination of DGC with Annexin V Magnetic-Activated Cell Sorting Prior to Cryopreservation Enhances the Postthaw Quality of Sperm from Infertile Male Patients with Poor Sperm Quality

Objective. To examine whether density gradient centrifugation (DGC) alone or its combination with annexin V magnetic-activated cell sorting (DGC-MACS) can be used to process semen samples from infertile male patients with poor sperm quality prior to subjecting these to freeze/thaw process in order to optimize the outcomes of sperm freezing. Methods. This study enrolled sixteen patients with sperm $\text{concentration}\ge 20\times {10}^6/\text{mL}$ , sperm $\text{motility}<30$ %, and/or <4% normal sperm morphology. Sperms were processed by DGC or DGC-MACS prior to the freeze/thaw process. Sperm motility, hyperosmotic swelling test (HOS), TUNEL test, and morphological analysis were performed before and after the freeze/thaw process. Results. The freeze/thaw process had a detrimental effect on sperm motility, viability, morphology, and DNA integrity in all three groups (RAW, DGC, and DGC + MACS groups). The DGC and DGC + MACS groups showed increased sperm motility, viability, and normal morphology following freeze/thaw than untreated frozen controls. The motility and viability were not significantly different between DGC-MACS-CPT (cryopreservation-thawing) and DGC-CPT groups. Moreover, almost no grade A or grade B sperm was observed in the DGC-MACS-CPT groups. The sperm selected by DGC or DGC + MACS showed decreased levels of sperm DNA fragmentation than RAW samples following freeze/thaw. Moreover, the sperm DNA fragmentation following freeze/thaw in the DGC-MACS-CPT group was significantly lower than that in the DGC-CPT group. Conclusions. Sperm preparation by DGC before cryopreservation improved the quality of sperm postthaw in infertile males with poor sperm quality. If the sperm quality following freeze/thaw is foreseen to be insufficient for artificial insemination with husband’s sperm or in vitro fertilization, or if there is high DNA fragmentation in RAW sperm, DGC + MACS should be used prior to cryopreservation to reduce sperm DNA fragmentation and improve the quality of sperm available for intracytoplasmic sperm injection.

Sperm Chromatin Structure Assay (SCSA®) for Fertility Assessment

The Sperm Chromatin Structure Assay (SCSA^® ) is a federally registered protocol for simultaneous flow cytometric measures of sperm DNA integrity and chromatin structure. Fresh or frozen/thawed raw semen samples are diluted in buffer to a sperm concentration of ∼1-2×10⁶ /ml and then treated with a pH 1.20 buffer for 30 s to open the DNA strands at sites of DNA strand breaks. The sperm are then stained with acridine orange (AO) that intercalates into double-strand DNA and fluoresces green (515-530 BP filter) and stacks on single-strand DNA that fluoresces red (630 LP filter) upon excitation from a 488 nm laser. The extent of single and double DNA strand breaks (DNA fragmentation index, %DFI) and level of excess nuclear histones (high DNA stainable sperm, %HDS) are simultaneously measured in individual sperm. From the time a fresh or frozen/thawed semen sample is received at the site of a flow cytometer (FCM) programmed for the SCSA protocol, data can be obtained within about 10 min on 5-10×10³ sperm. The %DFI and %HDS can be determined by computer-gated regions on the green versus red cytogram. Alternatively, a determination is made by transforming the green versus red cytogram to a total DNA stainability (red + green fluorescence) versus red/red + green fluorescence cytogram from which a frequency histogram is produced and the %DFI calculated from it. The clinical threshold for human natural or IUI fertilization is 25% DFI at which point the ART lab should consider moving to ICSI fertilization. The clinical threshold for HDS is also 25%; values above this level may result in early embryo death due to abnormal gene readout caused by the abnormal tertiary structure of chromatin. Numerous lifestyle and environmental factors cause sperm DNA fragmentation. Reactive oxygen species (ROS) play a significant role in DNA breakage. © 2022 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Sperm Chromatin Structure Assay (SCSA®) Basic Protocol 2: SCSA data analysis: Calculations of %DFI and %HDS of semen samples by one of two methods Support Protocol 1: SCSA sample collection and shipping Support Protocol 2: Flow cytometer set up Support Protocol 3: Selection and use of reference samples.

Comparison of sperm preparation methods to improve the recovery of mature spermatozoa in sub-fertile males

The integrity of chromatin in the spermatozoon is essential for reproductive outcome. The aim of this study was to evaluate the most effective and cost-effective method to reduce the percentage of spermatozoa with defects in chromatin decondensation for use in assisted reproductive technologies (ART) procedures. Sperm samples from 15 sub-fertile males were examined at CFA Naples to determine the sperm decondensation index (SDI), using the aniline blue test, before and after preparation, comparing density gradients with two different swim-up approaches. All three techniques led to a reduction in decondensed spermatozoa with no statistical difference (P > 0.05) between the control and the treated sperm. In contrast, we found a highly significant decrease in SDI (P < 0.01) after the two swim-up methods in all the samples, confirming the efficacy of these methods in lowering the percentage of chromatin compaction damage. There was no statistical difference between the two swim-up methods, however swim-up from the pellet led to improved count, motility and the percentage of normal condensed spermatozoa. We suggest that swim-up from the pellet be used in ART on sub-fertile males, both to reduce cell stress by multiple centrifugation and improve the recovery rate of mature spermatozoa.

Beyond conventional sperm parameters: the role of sperm DNA fragmentation in male infertility

Infertility is a condition that widely affects the couples all over the world. In this regard, sperm DNA fragmentation can lead to harmful reproductive consequences, including male infertility and poor outcomes after assisted reproductive techniques. The investigation of SDF in male infertility diagnostics has constantly increased over time, becoming more common in clinical practice with the recent publication of several guidelines regarding its testing. This narrative review aims to provide a comprehensive overview of the pathogenesis and causes of sperm DNA fragmentation, as well as the assays which are more commonly performed for testing. Moreover, we discussed the most recently published evidence regarding the use of SDF testing in clinical practice, highlighting the implications of high sperm DNA fragmentation rate on human reproduction, and the therapeutic approaches for the clinical management of infertile patients. Our review confirms a significant harmful impact of sperm DNA fragmentation on reproduction, and points out several interventions which can be applied in clinics to reduce sperm DNA fragmentation and improve reproductive outcomes. Sperm DNA fragmentation has been shown to adversely impact male fertility potential. As high sperm DNA fragmentation levels have been associated with poor reproductive outcomes, its testing may significantly help clinicians in defining the best therapeutic strategy for infertile patients.

Comprehensive functional analysis reveals that acrosome integrity and viability are key variables distinguishing artificial insemination bulls of varying fertility

In vitro methods of assessing bull semen quality in artificial insemination (AI) centers are unable to consistently detect individuals of lower fertility, and attempts to reliably predict bull fertility are still ongoing. This highlights the need to identify robust biomarkers that can be readily measured in a practical setting and used to improve current predictions of bull fertility. In this study, we comprehensively analyzed a range of functional, morphological, and intracellular attributes in cryopreserved spermatozoa from a selected cohort of Holstein Friesian AI bulls classified as having either high or low fertility (n = 10 of each fertility phenotype; difference of 11.4% in adjusted pregnancy rate between groups). Here, spermatozoa were assessed for motility and kinematic parameters, morphology, acrosome integrity, plasma membrane lipid packing, viability (or membrane integrity), superoxide production, and DNA integrity. In addition, spermatozoa were used for in vitro fertilization to evaluate their capacity for fertilization and successful embryo development. The information collected from these assessments was then used to phenotypically profile the 2 groups of bulls of divergent fertility status as well as to develop a model to predict bull fertility. According to the results, acrosome integrity and viability were the only sperm attributes that were significantly different between high- and low-fertility bulls. Interestingly, although spermatozoa from low-fertility bulls, on average, had reduced viability and acrosome integrity, this response varied considerably from bull to bull. Principal component analysis revealed a sperm phenotypic profile that represented a high proportion of ejaculates from low-fertility bulls. This was constructed based on the collective influence of several sperm attributes, including the presence of cytoplasmic droplets and superoxide production. Finally, using the combined results as a basis for modeling, we developed a linear model that was able to explain 47% of the variation in bull field fertility in addition to a logistic predictive model that had a 90% chance of distinguishing between fertility groups. Taken together, we conclude that viability and acrosome integrity could serve as fertility biomarkers in the field and, when used alongside other sperm attributes, may be useful in detecting low-fertility bulls. However, the variable nature of low-fertility bulls suggests that additional, in-depth characterization of spermatozoa at a molecular level is required to further understand the etiology of low fertility in dairy bulls.

Selection of high-quality sperm with thousands of parallel channels

Sperm selection is essential for successful fertilization and embryo development. Current clinical sperm selection methods are labor-intensive and lack the selectivity required to isolate high-quality sperm. Microfluidic sperm selection approaches have shown promise but present a trade-off between the quality and quantity of selected sperm - clinicians demand both. The structure of the female reproductive tract helps to isolate a sufficient quantity of high-quality sperm for fertilization with densely folded epithelium that provides a multitude of longitudinally oriented pathways that guide sperm toward the fertilization site. Here, a three-dimensionally structured sperm selection device is presented that levers this highly parallelized in vivo mechanism for in vitro sperm selection. The device is inserted in a test tube atop 1 mL of raw semen and provides 6500 channels that isolate ∼100 000 high-DNA-integrity sperm for assisted reproduction. In side-by-side clinical testing, the developed approach outperforms the best current clinical methods by improving the DNA integrity of the selected sperm subpopulation up to 95%. Also, the device streamlines clinical workflow, reducing the time required for sperm preparation 3-fold. This single-tube, single-step sperm preparation approach promises to improve both the economics and outcomes of assisted reproduction practices, especially in cases with significant male-factors.

Predictive Significance of Sperm DNA Fragmentation Testing in Early Pregnancy Loss in Infertile Couples Undergoing Intracytoplasmic Sperm Injection

Objective

This study aimed to determine the role of sperm DNA fragmentation as a marker that could predict early pregnancy loss (EPL), either independently or in combination with another marker or markers, after intracytoplasmic sperm injection (ICSI) cycles.

Methods

This prospective descriptive cohort study retrieved data from 162 couples who underwent their first ICSI cycles at the Center for Reproductive Endocrinology and Infertility of Hue University Hospital in Vietnam from May 2018 to December 2019. General characteristics, semen parameters, sperm DNA fragmentation index (DFI), fertilization, embryo development, pregnancy rates, and EPL were assessed. The receiver-operating characteristic (ROC) method was performed to identify the threshold of DFI in EPL. Multivariate analysis was used to demonstrate the relationship between the sperm DNA fragmentation level and EPL.

Results

Of 162 ICSI cycles, 23 (14.2%) involved EPL. There was no significant difference between the sperm DNA fragmentation rate and the overall rate of pregnancy loss, although the negative pregnancy outcome group had a median DFI that was higher than that of the positive pregnancy outcome group (20% vs 17.8%). The ROC analysis indicated that a sperm DNA fragmentation rate of 16.6% was the priority cut-off that could be used to distinguish EPL with a sensitivity of 73.9% (95% confidence interval [CI], 67.15-80.67) and specificity of 47.48% (95% CI, 39.79-55.17). The multivariate analysis confirmed that in female factors such as age, body mass index (BMI), and sperm DNA fragmentation level affected the EPL rate. However, a combination of the sperm DNA fragmentation level and female age or female BMI could not sufficiently predict EPL.

Conclusion

EPL can be affected by multiple factors including sperm DNA fragmentation; however, there is no sufficient evidence indicating that sperm DNA fragmentation, both as a single marker and combined with other markers, is a good predictor of EPL.

The effects of age on DNA fragmentation, the condensation of chromatin and conventional semen parameters in healthy nonsmoking men exposed to traffic air pollution

BACKGROUND

Numerous studies have investigated age-based declines in semen traits, but the impact of paternal age on semen parameter values remains inconclusive.

OBJECTIVES

The aim of this study was to detect an impact of age on semen quality was studied in healthy nonsmoking men exposed to traffic air pollution.

METHODS

Semen samples from 150 Prague City policemen aged 23 to 63 years were examined for standard semen parameters, sperm DNA fragmentation and high DNA stainability.

RESULTS

A significant positive correlation was found between age and %DFI (r = .359, P < .001), and negative correlations were found between age and sperm vitality (r = -.247, P < .001), the % acrosome-intact sperm (r = -.202, P = .013) and the % normal sperm heads (r = -.204, P = .012). A weak but significant negative correlation was found for high DNA stainability (% HDS) vs age (r = -.161, P = .050). No significant correlation was detected between male age and the other investigated semen quality parameters. At ages of 23 to 30, 31 to 40, 41 to 50, and 51 to 63 years, the mean %DFI values were 12.7 ± 7.18, 14.7 ± 7.42, 19.6 ± 11.25, and 34.2 ± 15.08, respectively.

CONCLUSION

Our study shows a strong relationship (P < .001) between the age of men and sperm DNA fragmentation in an occupational cohort at risk of exposure to heavy traffic-related air pollution in a large city center.

Elevated sperm DNA fragmentation does not predict recurrent implantation failure

In this study, we sought to determine whether sperm DNA fragmentation (DFI%) and high DNA stainability (HDS%) evaluated by sperm chromatin structure assay (SCSA) predict recurrent implantation failure (RIF) or pregnancy rate. A retrospective study was performed of consecutive cycles of ICSI treatment from 2009 to 2018. A total of 386 couples that underwent 1,216 frozen embryo transfer (FET) cycles were analysed. Mean female and male age was 34 ± 3.6 years and 37.3 ± 6.6 years, respectively, and a median total motile sperm count (TMSC) was 43.5 [9.9-105.5] million. Overall median DFI% and HDS% was 12 [7.1-18.9] and 9.6 [6.5-14.4] respectively. On multivariable analysis, DFI% and HDS% were not associated with RIF (DFI%: OR = 1.01, 95% CI: 0.98-1.04, p = .414; HDS%: OR = 0.97, 95% CI: 0.94-1.01, p = .107) or IVF success, defined as clinical pregnancy (DFI%: OR = 1.00, 95% CI: 0.99-1.01, p = .641; HDS%: OR = 1.01, 95% CI: 0.99-1.02, p = .565). We found that neither DFI% or HDS%, as assessed by SCSA, were predictive of RIF or pregnancy rate. This finding suggests that sperm DNA fragmentation does not predict RIF or pregnancy rate.

Sperm chromatin integrity in a man with macrocephaly syndrome

This study reports chromatin status and ICSI outcomes in a case of sperm macrocephaly syndrome(SMS), showing 100% of spermatozoa with abnormal morphology. Percentages of sperm DNA fragmentation for TUNEL (31.7% versus 6.5%), SCSA (33% versus 25%) assays, chromatin maturity tests, CMA3 (58% versus 29%) and aniline blue (63% versus 35%) staining were higher in case sample compared to the fertile sample. Artificial oocyte activation resulted in a similar fertilisation rate between case and control samples (71% versus 66.7%), but the case showed delayed embryo development on day 3 post-insemination. Unlike fertile case, no embryos reached the blastocyst stage. The result of this case study shows that macrocephaly is associated with reduced chromatin maturity and DNA integrity. Although both cases showed a similar chance for fertilisation through artificial chemical activation for only macrocephalic man, the developmental competency is jeopardised in such cases.

Clinical implications of sperm DNA damage in IVF and ICSI: updated systematic review and meta-analysis

The clinical effect of sperm DNA damage in assisted reproduction has been a controversial topic during recent decades, leading to a variety of clinical practice recommendations. While the latest European Society of Human Reproduction and Embryology (ESHRE) position report concluded that DNA damage negatively affects assisted reproduction outcomes, the Practice Committee of the American Society for Reproductive Medicine (ASRM) does not recommend the routine testing of DNA damage for in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). Herein, our aim was to perform a systematic review and meta-analysis of studies investigating whether sperm DNA damage affects clinical outcomes in IVF and ICSI, in order to contribute objectively to a consistent clinical recommendation. A comprehensive systematic search was conducted according to PRISMA guidelines from the earliest available online indexing year until March 2020, using the MEDLINE-PubMed and EMBASE databases. We included studies analysing IVF and/or ICSI treatments performed in infertile couples in which sperm DNA damage was well defined and assessed. Studies also had to include information about pregnancy, implantation or live birth rates as primary outcomes. The NHLBI-NIH quality assessment tool was used to assess the quality of each study. Meta-analyses were conducted using the Mantel-Haenszel method with random-effects models to evaluate the Risk Ratio (RR) between high-DNA-damage and control groups, taking into account the 95% confidence intervals. Heterogeneity among studies was evaluated using the I² statistic. We also conducted sensitivity analyses and post-hoc subgroup analyses according to different DNA fragmentation assessment techniques. We identified 78 articles that met our inclusion and quality criteria and were included in the qualitative analysis, representing a total of 25639 IVF/ICSI cycles. Of these, 32 articles had sufficient data to be included in the meta-analysis, comprising 12380 IVF/ICSI cycles. Meta-analysis revealed that, considering IVF and ICSI results together, implantation rate (RR = 0.74; 95% CI = 0.61-0.91; I²  = 69) and pregnancy rate (RR = 0.83; 0.73-0.94; I²  = 58) are negatively influenced by sperm DNA damage, although after adjustment for publication bias the relationship for pregnancy rate was no longer significant. The results showed a non-significant but detrimental tendency (RR = 0.78; 0.58-1.06; I²  = 72) on live birth rate. Meta-analysis also showed that IVF outcomes are negatively influenced by sperm DNA damage, with a statistically significant impact on implantation (RR = 0.68; 0.52-0.89; I²  = 50) and pregnancy rates (RR = 0.72; 0.55-0.95; I²  = 72), although the latter was no longer significant after correction for publication bias. While it did not quite meet our threshold for significance, a negative trend was also observed for live birth rate (RR = 0.48; 0.22-1.02; I²  = 79). In the case of ICSI, non-significant trends were observed for implantation (RR = 0.79; 0.60-1.04; I²  = 72) or pregnancy rates (RR = 0.89; 0.78-1.02; I²  = 44), and live birth rate (RR = 0.92; 0.67-1.27; I²  = 70). The current review provides the largest evidence to date supporting a negative association between sperm DNA damage and conventional IVF treatments, significantly reducing implantation and pregnancy rates. The routine use of sperm DNA testing is therefore justified, since it may help improve the outcomes of IVF treatments and/or allow a given couple to be advised on the most suitable treatment. Further well-designed controlled studies on a larger number of patients are required to allow us to reach more precise conclusions, especially in the case of ICSI treatments.

Recent advances and controversies in diagnosing and treating male infertility

Interest in male infertility has increased, as it plays an important role in up to 50% of couples struggling with infertility, which is an estimated 48.5 million couples globally. Despite recent advances, diagnosing and treating male infertility remain a significant clinical challenge owing to complex multifactorial pathways and the diversity of treatment options. This review will assess current controversial topics on male infertility such as the use of home-based semen testing, management of subclinical varicocele, and recent advances in the field of sperm proteomics.

Magnetic-Activated Cell Sorting (MACS): A Useful Sperm-Selection Technique in Cases of High Levels of Sperm DNA Fragmentation

Magnetic-activated cell sorting (MACS) can be used to separate apoptotic sperm with high proportions of fragmented DNA from the rest, thus improving the overall quality of the seminal sample. Therefore, the aim of this retrospective study was to investigate the efficiency of the MACS technique to increase reproductive outcomes in patients with high levels of sperm DNA fragmentation (SDF) undergoing intracytoplasmic sperm-injection (ICSI) cycles. In this study, we analyzed a total of 724 assisted-reproduction-technique (ART) cycles that were divided into two groups: the study group (n = 366) in which the MACS selection technique was performed after density-gradient centrifugation (DGC), and the control group (n = 358) in which only DGC was used for sperm selection. Reproductive outcomes were analyzed in both groups according to three different ART procedures: preimplantation genetic testing for aneuploidy (PGT-A), and autologous and oocyte-donation cycles. The MACS group showed significantly lower miscarriage rates in autologous ICSI cycles, higher pregnancy rates in oocyte-donation cycles, and a significant increase in live-birth rates in both autologous and oocyte-donation cycles. Overall, these results suggested that the MACS technique can be effectively used to eliminate sperm with high SDF levels, and therefore may help to improve reproductive outcomes in couples undergoing ART.

Semiquantitative promoter methylation of MLH1 and MSH2 genes and their impact on sperm DNA fragmentation and chromatin condensation in infertile men

To investigate the semiquantitative methylation alterations of MLH1 and MSH2 and the possible association among methylation of MLH1 and MSH2, sperm DNA fragmentation and sperm chromatin condensation in idiopathic oligoasthenoteratozoospermic men. Seventy-five idiopathic infertile men and 52 fertile and/or normozoospermic men were included in the study. SDF was analysed using the TUNEL assay in semen samples of 100 men. Promoter methylation of MLH1 and MSH2 genes was assessed by semiquantitative methylight analysis in semen samples of 39 and 40 men respectively. Sperm chromatin condensation was evaluated using aniline blue staining in 114 men. MLH1 promoter methylation was positively correlated with the percentage of aniline blue positive spermatozoa (r = 0.401, p = 0.0188). On the other hand, MSH2 promoter methylation was negatively correlated with sperm concentration and total sperm count (r = -0.421, p = 0.0068 and r = 0.4408, p = 0.009 respectively). The percentage of aniline blue positive spermatozoa in the control group was significantly lower than in the OAT group (p < 0.0001) and negatively correlated with total sperm count (r = -0.683, p < 0.0001), progressive sperm motility (r = -0.628, p < 0.0001), total motility (r = -0.639, p < 0.0001) and normal morphology (r = -0.668, p < 0.0001). Promoter methylation profile of MLH1 and MSH2 genes may play role on sperm DNA packaging and conventional semen parameters respectively.

Unravelling how in vitro capacitation alters ram sperm chromatin before and after cryopreservation

BACKGROUND

Sperm chromatin structure provides valuable information for the prediction of male fertility and can be altered during different procedures. Previous studies have shown that sperm chromatin condensation decreased during in vitro capacitation. Moreover, cryopreservation can affect sperm DNA integrity and chromatin compaction.

OBJECTIVES

This study aimed to investigate dynamic modifications produced in the chromatin structure of ram spermatozoa during in vitro capacitation before and after cryopreservation.

MATERIALS AND METHODS

Chromatin decondensation (AB+), DNA methylation, DNA fragmentation index (%DFI) and high DNA stainability (HDS) were evaluated in fresh and frozen-thawed ram spermatozoa incubated under capacitating (CAP) conditions at 1, 5, 15, 30, 60, 120, 180 and 240 minutes and under non-capacitating (NC) conditions at 0, 15 and 240 minutes.

RESULTS

Incubation in NC conditions did not induce significant changes in chromatin condensation (P > .05; AB + and HDS). However, incubation of fresh and cryopreserved ram spermatozoa under CAP conditions significantly increased chromatin decondensation (P < .05), reaching the highest percentage of AB + and HDS from 180 to 240 minutes in fresh samples and from 5 to 30 minutes in cryopreserved samples. Both variables (HDS and AB+) were positively correlated with tyrosine phosphorylation, total motility, progressive motility, curvilinear velocity and amplitude of lateral head displacement, as well as between them under CAP conditions in fresh and cryopreserved spermatozoa. DNA methylation significantly increased in cryopreserved spermatozoa (P < .05), but only after extended incubation under CAP conditions (60-240 minutes), while the %DFI, albeit higher in cryopreserved samples, remained constant under CAP and NC conditions in both types of sample (P > .05).

DISCUSSION AND CONCLUSIONS

Our results suggest that sperm chromatin condensation decreased progressively during in vitro capacitation of ram spermatozoa, while sperm DNA integrity remained intact. Such changes in chromatin condensation appeared faster after sperm cryopreservation.

Could high DNA stainability (HDS) be a valuable indicator of sperm nuclear integrity?

Background

The Sperm Chromatin Structure Assay (SCSA®), in addition to identifying the DNA Fragmentation Index (DFI) also identifies High DNA satiability (HDS), supposed to reflect the nuclear compaction of spermatozoa. However, data on what exactly this parameter reveals, its relevance and usefulness are contradictory. In order to shed light on this situation, spermatozoa of a cohort (N = 397) of infertile men were subjected to the SCSA®, TUNEL (terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling) and CMA3 (Chromomycin A3) tests. In a smaller subcohort (N = 100), aniline blue (AB) and toluidine blue (TB) staining were performed in addition. The objective of this study was thus to answer the question of whether HDS is a relevant and reliable parameter to be taken into account?

Results

HDS does not appear to be a reliable indicator of nuclear immaturity because it shows a weak correlation with the CMA3, AB and TB stains. The low correlation of HDS with sperm DNA fragmentation (TUNEL and SCSA®) and DNA condensation (CMA3, AB and TB) tests suggests that these two parameters could be decoupled. Unlike DFI and TUNEL, HDS has not been shown to correlate with classic clinical situations of male infertility (asthenozoospermia, teratozoospermia or astheno-teratozoospermia).

Conclusion

HDS correlates poorly with most tests that focus specifically on the level of maturity of the sperm nucleus. To our knowledge, this study is the first to compare SCSA®, TUNEL, AB, TB and CMA3 assays on identical samples. It shows the potency, consistency and limitations of each test and the care that must be taken in their interpretation.

Single Layer Centrifugation with 20% or 30% Porcicoll separates the majority of spermatozoa from a sample without adversely affecting sperm quality

Centrifugation of boar semen through one layer of 40% colloid (Porcicoll) was previously shown to separate spermatozoa from bacteria without having a detrimental effect on sperm quality. However, some spermatozoa were lost. The purpose of the present study was to determine whether 20% or 30% Porcicoll could be used to recover most of the spermatozoa without impacting on sperm quality. Insemination doses (n = 10) from a commercial boar station were sent to the laboratory at the Swedish University of Agricultural Sciences and processed by Single Layer Centrifugation with 20% and 30% Porcicoll approximately 7 hr after semen collection. The resulting sperm samples and controls were evaluated for sperm quality immediately and again after storage at 16-18°C for 4 and 7 days. Sperm recovery was 94 ± 18% and 87 ± 15% for 20% and 30% Porcicoll, respectively (p > .05). Sperm mitochondrial membrane potential and chromatin integrity were unaffected (p > .05). The proportion of live spermatozoa producing superoxide (9 ± 8%, 7 ± 6% and 3 ± 1%; p < .05), and the proportion of spermatozoa with high stainability DNA (0.68 ± 19%, 0.61 ± 0.22% and 0.96 ± 0.23%; p < .05- <0.01), were marginally increased whereas membrane integrity, although high, was lower in the centrifuged samples than in the controls (82 ± 8%, 83 ± 5% versus 92 ± 4%; p < .05). In conclusion, centrifugation through 20% or 30% Porcicoll enables most spermatozoa to be recovered, without having a major effect on sperm quality. These results are encouraging for further studies involving microbiological investigation of the processed samples, and scaling-up to process larger volumes of boar ejaculates.

Seminal oxidation-reduction potential and sperm DNA fragmentation index increase among infertile men with varicocele

Varicocele is a common cause of male infertility. It is reported that low sperm concentration, motility and morphology are indicative of increased sperm DNA fragmentation index (DFI) in men with varicocele. Although research has been conducted into the relationship between varicocele and DFI, little is known about seminal oxidation-reduction potential (ORP) in varicocele patients. We assessed the relationship between varicocele with seminal ORP and sperm DFI in both fertile and infertile men. This prospective case-control study compared the findings from infertile men with varicocele to those of men with normal spermatogenesis without varicocele. Semen samples were collected and assessed using the WHO (2010) guidelines. ORP was measured (mV) and normalized to sperm concentration (mV/10⁶ sperm/mL). DFI was measured using the sperm chromatin structure assay (SCSA) method. For group comparisons, only samples with a concentration >1 × 10⁶ sperm/mL were included. Infertile men with varicocele had significantly lower mean sperm concentration, motility and total sperm count. Conversely, infertile men with varicocele had a significantly higher mean serum FSH level, and higher ORP and DFI values than fertile controls. ORP was higher in patients with varicocele and positively correlated with DFI (p < 0.01). ORP and DFI showed significant negative correlations with semen parameters (sperm concentration, motility and total sperm count) in infertile men with a varicocele.

Novel Techniques of Sperm Selection for Improving IVF and ICSI Outcomes

Almost 50% of the infertility cases are due to male factors. Assisted reproductive technologies (ARTs) allow to overcome the incapacity of these patients' spermatozoa to fertilize the oocyte and produce a viable and healthy offspring, but the efficiency of the different techniques has still the potential to improve. According to the latest reports of the European Society of Human Reproduction and Embryology (ESHRE) and the Centers for Disease Control and Prevention of the United States (CDC), the percentages of deliveries per ART cycle in 2014 and 2016 were 21 and 22%, respectively. Among the reasons for this relatively low efficiency, the quality of the spermatozoa has been pointed out as critical, and the presence of high percentages of DNA-damaged spermatozoa in patients' ejaculates is possibly one of the main factors reducing the ARTs outcomes. Thus, one of the main challenges in reproductive medicine is to ensure the highest quality of the spermatozoa used in ARTs, and specifically, in terms of genetic integrity. The latest techniques for the preparation and selection of human spermatozoa are herein discussed focusing on those proven to improve one or several of the following parameters: sperm genetic integrity, fertilization capacity, embryo production, and in vitro survival, as well as pregnancy and delivery rates following in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). In addition, we discuss the potential of techniques developed in non-human mammals that could be further transferred to the clinic.

Utility and Predictive Value of Human Standard Semen Parameters and Sperm DNA Dispersion for Fertility Potential

Because the assessment of sperm DNA fragmentation (SDF) plays a key role in male fertility, our study was designed to find the relationships between SDF and standard semen parameters. The receiver operating characteristic (ROC) curve showed that 18% SDF is a prognostic parameter for discriminating between men with normal and abnormal standard semen parameters (n = 667). Men with > 18% SDF had significantly lower quality semen, a higher prevalence of abnormal semen characteristics, and a higher odds ratio for abnormal semen parameters compared to men with ≤ 18% SDF. An ROC analysis provided predictive values for age and semen parameters to distinguish between men with SDF > 18% and men with ≤ 18% SDF. SDF was positively correlated with male age and teratozoospermia index but negatively with sperm concentration, total number of spermatozoa, sperm morphology, progressive motility, and vitality. Our study shows that 18% SDF has a predictive value for distinguishing between men with normal and abnormal semen characteristics. Men with >18% SDF have a higher risk for abnormal semen parameters, while age and obtained semen parameters have a predictive value for SDF. There is a relationship between SDF and conventional sperm characteristics, and thus, SDF can be incorporated into male fertility assessment.