Sperm selection during ICSI treatments reduces single- but not double-strand DNA break values compared to the semen sample

DNA damage in prepared semen is negatively associated with semen quality and fertilisation rate in assisted reproduction technology (ART) treatment

Sperm DNA contains strand breaks and base damage that can potentially affect reproductive health. This study aims to determine to what extent sperm DNA integrity and alkylation is associated with semen quality and assisted reproduction technology (ART) treatment outcomes, in particular fertilisation and cleavage rates. Male partners of couples attending for infertility treatment were recruited. DNA integrity (% tail DNA, sperm with either low (LDD) or high (HDD) damage levels) was measured by a neutral Comet assay and N7-methyldeoxyguanosine (N7-MedG) DNA levels by an immunoslotblot in sperm prepared by density gradient centrifugation. Associations between DNA damage, semen quality and ART treatment outcomes were assessed. N7-MedG levels were lower and the proportion of LDD sperm higher in prepared than in neat sperm samples. The proportion of HDD sperm and % tail DNA were significantly negatively associated and the proportion of LDD sperm positively associated with semen quality. Fertilisation, but not cleavage, rate nor live birth, was significantly negatively associated with N7-MedG levels, the proportion of HDD sperm and % tail DNA and was positively associated with the proportion of LDD sperm. These results confirm that DNA damage, even in prepared sperm, is associated with adverse semen quality and suggest that sperm DNA damage affects the early stages of embryo formation.

The intricate "ART" of ICSI

This manuscript explores the intricacies and nuances of the Intracytoplasmic Sperm Injection (ICSI) procedure, drawing on insights from three decades of experience at a specialized center managing numerous cases of male factor infertility. Our center is comprised of an embryology laboratory, an andrology and assisted fertilization laboratory, and a Preimplantation Genetic Testing for Aneuploidy (PGT-A) laboratory, each fostering specialized expertise independently. Collaboration among these laboratories, alongside reproductive physicians and urologists, ensures comprehensive feedback and optimal care for patients undergoing infertility treatment. The manuscript specifically focuses on the andrology laboratory's pivotal role in evaluating and treating infertile patients, highlighting critical preparations for the ICSI procedure, and the key considerations essential to its successful implementation, including the selection of the ideal spermatozoon, oocyte dysmaturity, proper equipment, and most importantly the execution of the procedure itself.

Impact of Microfluidic Sperm Sorting on Embryonic Euploidy in Infertile Patients with Sperm DNA Damage: A Retrospective Study

BACKGROUND

Sperm DNA fragmentation is an important factor that affects male fertility. This study intends to evaluate the impact of sperm DNA damage [single-strand breaks (SSB) and double-strand breaks (DSB)] on fertilisation and embryonic euploidy after intracytoplasmic sperm injection (ICSI). Of the different sperm selection techniques, the novel microfluidic sperm sorting (MSS) ZyMōt™ ICSI device reduces both SSB and DSB in semen samples. The second objective is to study the impact of this MSS device on fertilisation and embryonic euploidy.

MATERIALS AND METHODS

This retrospective study included data from 167 ICSI treatments. The alkaline and neutral Comet assays were used to analyse SSB and DSB, respectively. Analysis of fertilisation and embryo euploidy rates was performed in four groups of patients with normal/altered SSB or DSB values. Density gradient centrifugation (DGC) and the ZyMōt™ ICSI MSS device were used for semen preparation.

RESULTS

Fertilisation rates in 167 ICSI cycles were higher when using sperm from patients with normal SSB values (70.84%) and patients with abnormal SSB whose samples were processed using the MSS device (69.71%) compared to patients with abnormal SSB values using DGC (58.49%). Preimplantation genetic testing for aneuploidies (PGTA) revealed a higher embryo euploidy rate in patients with normal DSB values (60.00%) and patients with abnormal DSB whose samples were processed using the MSS device (44.59%) compared to patients with abnormal DSB values using DGC (36.84%). When female age was considered, there were fewer euploid embryos in women ≥35 years of age compared to younger women, independently of SSB and DSB. The number of euploid embryos increased when the MSS device was used.

CONCLUSION

High SSB and DSB values in semen samples decreased fertilisation rates and embryonic euploidy, respectively. The ZyMōt™ ICSI device for semen preparation increased both rates, especially in couples that included women <35 years old.

Sperm DNA Fragmentation in Male Infertility: Tests, Mechanisms, Meaning and Sperm Population to Be Tested

Sperm DNA fragmentation (sDF) is a DNA damage able to predict natural conception. Thus, many laboratories added tests for the detection of sDF as an adjunct to routine semen analysis with specific indications. However, some points related to sDF are still open. The available tests are very different each from other, and a direct comparison, in terms of the prediction of reproductive outcomes, is mandatory. The proposed mechanisms responsible for sDF generation have not yielded treatments for men with high levels of sDF that have gained the general consent in clinical practice, thus requiring further research. Another relevant point is the biological meaning to attribute to sDF and, thus, what we can expect from tests detecting sDF for the diagnosis of male infertility. SDF can represent the "tip of iceberg" of a more extended and undetected sperm abnormality somehow impacting upon reproduction. Investigating the nature of such a sperm abnormality might provide novel insights into the link between sDF and reproduction. Finally, several studies reported an impact of native sDF on assisted reproduction technique outcomes. However, to fertilise the oocyte, selected spermatozoa are used where sDF, if present, associates with highly motile spermatozoa, which is the opposite situation to native semen, where most sDF associates with non-viable spermatozoa. Studies comparing the impact of sDF, as assessed in both native and selected spermatozoa, are needed.

Developing and validating a prediction model of live birth following single vitrified-warmed blastocyst transfer

RESEARCH QUESTION

Can the developed clinical prediction model offer an accurate estimate of the likelihood of live birth, involving blastocyst morphology and vitrification day after single vitrified-warmed blastocyst transfer (SVBT), and therefore assist clinicians and patients?

STUDY DESIGN

Retrospective cohort study conducted at a Spanish university-based reproductive medicine unit (2017-2021) including consecutive vitrified-warmed blastocysts from IVF cycles. A multivariable logistic regression incorporated key live birth predictors: vitrification day, embryo score, embryo ploidy status and clinically relevant variables, i.e. maternal age.

RESULTS

The training set involved 1653 SVBT cycles carried out between 2017 and 2020; 592 SVBT cycles from 2021 constituted the external validation dataset. The model revealed that female age and embryo characteristics, including overall quality and blastulation day, is linked to live birth rate in SVBT cycles. Stratification by vitrification day and quality (from day-5A to day-6 C blastocysts) applied to genetically tested and untested embryos. The model's area under the curve was 0.66 (95% CI 0.64 to 0.69) during development and 0.65 (95% CI 0.61 to 0.70) in validation, denoting moderate discrimination. Calibration plots showed strong agreement between predicted and observed probabilities.

CONCLUSION

By incorporating essential predictors such as vitrification day, embryo morphology grade, age and preimplantation genetic testing for aneuploidy usage, this predictive model offers valuable guidance to clinicians and patients, enabling accurate forecasts of live birth rates for any given vitrified blastocyst within SVBT cycles. Additionally, it serves as a potentially indispensable laboratory tool, aiding in selecting the most promising blastocysts for optimal outcomes.

Microfluidic sperm sorting selects a subpopulation of high-quality sperm with a higher potential for fertilization

STUDY QUESTION

Is a microfluidic sperm sorter (MSS) able to select higher quality sperm compared to conventional methods?

SUMMARY ANSWER

The MSS selects sperm with improved parameters, lower DNA fragmentation, and higher fertilizing potential.

WHAT IS KNOWN ALREADY

To date, the few studies that have compared microfluidics sperm selection with conventional methods have used heterogeneous study population and have lacked molecular investigations.

STUDY DESIGN, SIZE, DURATION

The efficiency of a newly designed MSS in isolating high-quality sperm was compared to the density-gradient centrifugation (DGC) and swim-up (SU) methods, using 100 semen samples in two groups, during 2023-2024.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Semen specimens from 50 normozoospermic and 50 non-normozoospermic men were sorted using MSS, DGC, and SU methods to compare parameters related to the quality and fertilizing potential of sperm. The fertilizing potential of sperm was determined by measurement of phospholipase C zeta (PLCζ) and post-acrosomal sheath WW domain-binding protein (PAWP) expression using flow cytometry, and the chromatin dispersion test was used to assess sperm DNA damage.

MAIN RESULTS AND THE ROLE OF CHANCE

In both normozoospermic and non-normozoospermic groups, the MSS-selected sperm with the highest progressive motility, PLCζ positive expression and PLCζ and PAWP fluorescence intensity the lowest non-progressive motility, and minimal DNA fragmentation, compared to sperm selected by DGC and SU methods (P < 0.05).

LIMITATION, REASONS FOR CAUTION

The major limitations of our study were the low yield of sperm in the MSS chips and intentional exclusion of severe male factor infertility to yield a sufficient sperm count for molecular experiments; thus testing with severe oligozoospermic semen and samples with low count and motility is still required. In addition, due to ethical considerations, at present, it was impossible to use the sperm achieved from MSS in the clinic to assess the fertilization rate and further outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

Our research presents new evidence that microfluidic sperm sorting may result in the selection of high-quality sperm from raw semen. This novel technology might be a key to improving clinical outcomes of assisted reproduction in infertile patients.

STUDY FUNDING/COMPETING INTEREST(S)

The study is funded by the Iran University of Medical Sciences and no competing interest exists.

TRIAL REGISTRATION NUMBER

N/A.

Advanced Paternal Age: A New Indicator for the Use of Microfluidic Devices for Sperm DNA Fragmentation Selection

New social conditions and progress in ART have both contributed to the delay in parenthood in developed countries. While the effects of maternal age have been widely studied, paternal age is poorly understood, and there are no specific guides on ART techniques to treat its deleterious effects. It is known that there is an increase in sperm DNA fragmentation (SDF) in elderly men, and new sperm selection devices using microfluids have been developed. This study analyses 189 ICSI cycles with donor oocytes performed between January 2018 and February 2022. Spermatozoa were selected using an MSS device or density gradients, followed by ICSI fertilization and fresh/thawed embryo transfer. We assessed the association between the selection technique, paternal age (< or ≥45) and reproductive outcomes. Fertilization (FR), blastulation (BR), implantation (IR), live-birth (LBR) and miscarriage (MR) rates were calculated. The results showed significantly higher IR (57.7% vs. 42.5%) and LBR (42.9% vs. 30.3%) when applying MSS selection, and particularly higher BR, IR and LBR when the paternal age was equal to or over 45 years (BR: 64.4 ± 23% vs. 50.1 ± 25%, IR: 51.5% vs. 31.6% and LBR: 42.4% vs. 23.7%). We also found a negative correlation between BR and paternal age (r2 = 0.084). The findings show that MSS enhances success in assisted reproduction cycles with ICSI, especially in couples with advanced paternal age. We propose advanced paternal age as a new indicator for the application of sperm selection techniques that reduce fragmentation.

Fluorescent enzyme-based biosensor for sensitive analysis of DNA damage in cryopreserved sperm

The freeze-thaw process can induce irreversible structural and functional changes in human sperm, particularly sperm DNA damage. Selecting a more accurate and sensitive detection method for evaluating sperm DNA integrity is crucial. To accurately assess sperm DNA integrity following the freeze-thaw process and significantly improve the clinical and scientific utilization of cryopreserved sperm. In this study, we utilized a novel fluorescent biosensor, assisted by terminal deoxynucleotidyl transferase (TdT) and Endonuclease IV, to detect DNA breakpoints during sperm cryopreservation. We evaluated the biosensor's performance by comparing it with the conventional DNA fragmentation index (DFI) measured using sperm chromatin structure analysis (SCSA). The cryopreserved group exhibited a significantly higher sperm DFI compared to the fresh group. No significant difference was observed between the antioxidant group and the cryopreserved group. However, the new method revealed a significant reduction in the number of DNA breakpoints in the antioxidant group compared to the cryopreserved group. The novel biosensor demonstrated superior accuracy and effectiveness in assessing sperm DNA integrity during cryopreservation compared to the conventional SCSA method. We believe that the biosensor holds significant potential for widespread use in the field of reproductive medicine.

Innovative technology for evaluation of sperm DNA double-strand breaks diagnoses male factor infertility and prevents reproductive failures

Neutral comet assay has been available for two decades to evaluate sperm double-strand breaks (DSBs). However, its clinical usability is limited due to its complex and time-consuming procedure, as well as the lack of a standardized scoring system. The aim of this study was to: develop a rapid diagnostic method for DSBs, Sperm DNA Fragmentation Releasing Assay (SDFR), and explore the association between DSBs and reproductive outcomes. We pioneered the use of polyacrylamide (PA) for embedding sperm chromatin and optimized the porosity of PA to be between 10 and 13%. The refined PA network allowed the trapping of DSBs, which dispersed halo on an immunological slide; in contrast, intact chromatin failed to develop a halo. A strong correlation was showed between reproducible values obtained from SDFR and neutral comet assay. SDFR were responsive to dose-/time-dependent simulated DSBs, indicating high sensitivity and specificity. Furthermore, we conducted a retrospective study of couples with embryonic aneuploidy screening, and recording DSB profiles of the male partners. Our findings revealed that DSB enabled to predict embryonic aneuploidy whereas basic semen parameters did not. In conclusion, SDFR offers a rapid and user-friendly approach for evaluating DSBs, with potential implications for predictive healthcare in reproductive medicine.

The impact of female BMI on sperm DNA damage repair ability of oocytes and early embryonic development potential in intracytoplasmic sperm injection cycles

Background

Obesity adversely influences the quality of oocytes and embryos and can affect DNA repair in embryos, leading to reproductive issues. However, the effects of body mass index (BMI) on DNA repair ability in oocytes during intracytoplasmic sperm injection (ICSI) cycles have not yet been investigated. Therefore, this retrospective study aimed to analyze the influence of sperm DNA damage on embryo development and reproductive outcomes in overweight/obese and normal-weight women in ICSI cycles.

Methods

A total of 1,141 patients who received the first fresh ICSI cycle treatments were recruited from July 2017 to July 2021. Based on the BMI of the women, all patients were divided into normal weight (18.5≤BMI<25 kg/m2; n=824; 72.22%) and overweight/obese (BMI≥25 kg/m2; n=317; 27.78%) groups. Furthermore, according to the sperm DNA fragmentation index (DFI), these two groups were subdivided into two subgroups: DFI<30% and DFI≥30%.

Results

In the normal-weight women group, the embryonic development and reproductive outcomes of ICSI cycles were not statistically different between the two subgroups (DFI<30% and DFI≥30%). However, in the overweight/obese women group, couples with a sperm DFI≥30% had a significantly lower fertilization rate (76% vs. 72.7%; p=0.027), cleavage rate (98.7% vs. 97.2%; p=0.006), and high-quality embryo rate (67.8% vs. 62.6%; p=0.006) than couples with a sperm DFI<30%.

Conclusion

When injected sperm with high DFI into the oocytes of overweight/obese women, resulting in lower fertilization, cleavage, and high-quality embryo rates in ICSI cycles, and the decreased early developmental potential of embryos from overweight/obese patients may be caused by the diminished capacity of oocytes to repair sperm DNA damage.

Research progress on the role and mechanism of DNA damage repair in germ cell development

In the complex and dynamic processes of replication, transcription, and translation of DNA molecules, a large number of replication errors or damage can occur which lead to obstacles in the development process of germ cells and result in a decreased reproductive rate. DNA damage repair has attracted widespread attention due to its important role in the maintenance and regulation of germ cells. This study reports on a systematic review of the role and mechanism of DNA damage repair in germline development. First, the causes, detection methods, and repair methods of DNA damage, and the mechanism of DNA damage repair are summarized. Second, a summary of the causes of abnormal DNA damage repair in germ cells is introduced along with common examples, and the relevant effects of germ cell damage. Third, we introduce the application of drugs related to DNA damage repair in the treatment of reproductive diseases and related surgical treatment of abnormal DNA damage, and summarize various applications of DNA damage repair in germ cells. Finally, a summary and discussion is given of the current deficiencies in DNA damage repair during germ cell development and future research development. The purpose of this paper is to provide researchers engaged in relevant fields with a further systematic understanding of the relevant applications of DNA damage repair in germ cells and to gain inspiration from it to provide new research ideas for related fields.

Should ICSI be implemented on patients with poor-quality embryos in the previous IVF cycle?

This study was to evaluate whether Intracytoplasmic sperm injection (ICSI) can improve the quality of embryo in patients with poor-quality embryos in the previous In-vitro fertilization (IVF) cycle, which was cancelled before transfer. This was a retrospective cohort study of 178 IVF and 158 ICSI cycles for patients with poor-quality embryos in the previous IVF cycle in the Center for Reproductive Medicine, Women and Children's Hospital of Chongqing Medical University from March 2016 to June 2022. The 2 PN rate, oocyte utilization rate , high-quality embryo rate and clinical pregnancy rate were compared between the two groups. Furthermore, the implantation rate, miscarriage rate and cycle cancelation rate were measured and compared. ICSI resulted in a comparable 2 PN rate, oocyte utilization rate and cycle cancelation rate with IVF. The high-quality embryo rate of ICSI group was significantly higher than that of IVF group (5.56% vs. 2.60%, P < 0.05). Eventually, a total of 239 patients performed embryo transfer. ICSI resulted in a significantly higher clinical pregnancy rate (55.56% vs. 40.98%, P < 0.05) compared with IVF, however, there were no notable differences in miscarriage rate and implantation rate. The present study suggested that ICSI significantly improved the high-quality embryo rate and clinical pregnancy of the patients with poor-quality embryos in the previous IVF cycle. Prospective randomized controlled trials are needed to further verify.

Double strand DNA breaks in sperm: the bad guy in the crowd

PURPOSE

The main objective of this opinion paper was to bring to light and enhance our understanding of the amount of double-strand DNA breaks in sperm and whether there is a threshold of no return when considering repair by the oocyte/embryo.

METHODS

A brief review of literature related to the theories proposed for the appearance of double-strand breaks in human spermatozoa. Further commentary regarding their detection, how oocytes or embryos may deal with them, and what are the consequences if they are not repaired. Finally, a strategy for dealing with patients who have higher levels of double-strand DNA breaks in sperm is proposed by reviewing and presenting data using testicular extracted sperm.

RESULTS

We propose a theory that a threshold may exist in the oocyte that allows either complete or partial DNA repair of impaired sperm. The closer that an embryo is exposed to the threshold, the more the effect on the ensuing embryo will fail to reach various milestones, including blastocyst stage, implantation, pregnancy loss, an adverse delivery outcome, or offspring health. We also present a summary of the role that testicular sperm extraction may play in improving outcomes for couples in which the male has a high double-strand DNA break level in his sperm.

CONCLUSIONS

Double-strand DNA breaks in sperm provide a greater stress on repair mechanisms and challenge the threshold of repair in oocytes. It is therefore imperative that we improve our understanding and diagnostic ability of sperm DNA, and in particular, how double-strand DNA breaks originate and how an oocyte or embryo is able to deal with them.

Sperm cryopreservation does not affect live birth rate in normozoospermic men: analysis of 7969 oocyte donation cycles

STUDY QUESTION

Does sperm cryopreservation influence the reproductive outcomes of normozoospermic patients in oocyte donation cycles?

SUMMARY ANSWER

After controlling for confounders, the use of cryopreserved semen from normozoospermic patients does not affect pregnancy and live birth rates after elective ICSI.

WHAT IS KNOWN ALREADY

Sperm cryopreservation by slow freezing is a common practice in ART. While frozen-thawed semen typically presents reduced motility and vitality, its use for ICSI is generally considered adequate in terms of reproductive outcomes. Nevertheless, most studies comparing reproductive outcomes between fresh and cryopreserved sperm include patients with severe male factor (testicular sperm, oligo-, and/or asthenozoospermia) or women of advanced maternal age, where the altered quality of the gametes can partially mask the full effect of freezing/thawing.

STUDY DESIGN, SIZE, DURATION

The study included a retrospective cohort of 7969 couples undergoing their first oocyte donation cycle between January 2013 and December 2019 in one large clinic, using normozoospermic semen from the male partner. All cycles involved elective ICSI, fresh oocytes, and a fresh embryo transfer, either at cleavage or blastocyst stage. Two study groups were established based on the sperm status: fresh (n = 2865) and cryopreserved (n = 5104).

PARTICIPANTS/MATERIALS, SETTING, METHODS

A slow freezing protocol was used for all sperm cryopreservation. Sperm washing, capacitation, and selection prior to ICSI were performed identically for fresh and frozen-thawed samples, using pellet swim-up. Fertilization rate (FR), pregnancy (biochemical and ongoing), and live birth rates were compared between study groups using univariate and multivariate regression analyses.

MAIN RESULTS AND THE ROLE OF CHANCE

Male and female age, sperm concentration and motility after ejaculation, and number of oocytes inseminated were similar between cycles using fresh or cryopreserved sperm. Analysis by Student's t-test did not indicate a significant difference in FR between fresh and cryopreserved sperm (P = 0.0591); however, after adjusting for confounders, this difference reached statistical significance: 74.65% FR for fresh (CI 95%: 73.92-75.38) versus 73.66% for cryopreserved sperm (CI 95%: 73.11-74.20), P = 0.0334. The adjusted regression analysis revealed higher odds of biochemical pregnancy when using fresh sperm (odds ratio (OR): 1.143, P = 0.0175), but no significant effects of sperm cryopreservation were observed for ongoing pregnancy (OR: 1.101, P = 0.0983) and live birth (OR: 1.082, P = 0.1805).

LIMITATIONS, REASONS FOR CAUTION

Caution should be exerted when extrapolating these results to different protocols for sperm cryopreservation and selection, or to IVM, advanced maternal age and classical IVF cycles, which were excluded from analysis. Owing to the retrospective nature of the study, some uncontrolled for variables may affect the results.

WIDER IMPLICATIONS OF THE FINDINGS

Sperm cryopreservation does not affect pregnancy and live birth rates in normozoospermic patients, and although it may lower FR s slightly, this would not be clinically relevant. In line with previous studies that included patients with an apparent male or female factor, sperm cryopreservation is a safe and convenient technique.

STUDY FUNDING/COMPETING INTEREST(S)

The study received no external funding and all authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

N/A.

Microfluidic sperm sorting improves ICSI outcomes in patients with increased values of Double-Strand Breaks in sperm DNA

BACKGROUND

Delays in embryo kinetics, implantation failures in ICSI treatments and recurrent miscarriages have been associated with high values of Double-Strand Breaks (DSB) in sperm DNA. While conventional methods for semen preparation have been shown to be inefficient reducing DSB values, Microfluidic Sperm Sorting (MSS) devices are promising tools to reduce this damage.

OBJECTIVE

To study the clinical utility of an MSS device in ICSI treatments when the male partner presents increased DSB values, as compared to the use of conventional methods based on sperm motility.

METHODS

This retrospective cohort study included 28 infertile couples undergoing ICSI treatments. Only couples where the male partner presented increased values of DSB were included. DSB values were evaluated in semen samples by the Neutral Comet assay. Couples performed a first ICSI cycle using conventional methods for semen preparation (Density Gradients and Swim-up) and a second ICSI cycle using the ZyMōt™ICSI (formerly named FertileChip®) microfluidic device. Embryology and clinical outcomes were compared between ICSI cycles.

RESULTS

Semen parameters and the number of obtained and fertilized oocytes did not show differences between ICSI rounds. Clinical outcomes were statistically better when MSS was used: the biochemical pregnancy rate increased 28.31%; the clinical pregnancy rate increased 35.56% and the number of live births increased 35.29%, as compared to the first ICSI cycle in this group of patients.

CONCLUSIONS

The ZyMōt™ICSI microfluidic device improved the reproductive outcomes in couples where the male partner presented increased DSB values, when compared to the use of conventional semen preparation techniques.

Sperm DNA integrity does play a crucial role for embryo development after ICSI, notably when good-quality oocytes from young donors are used

Based on the inconsistent literature published thus far involving infertile patients, whether intracytoplasmic sperm injection (ICSI) allows overcoming total fertilization failure due to sperm DNA fragmentation is still unclear. Related to this, female factors, which may have a significant impact on assisted reproduction outcomes, can mask male infertility. In this scenario, evaluating ICSI outcomes following cycles using healthy donor gametes could shed light on this realm, as it would avoid the influence of (un)known confounding factors present in infertile individuals. The present work, therefore, aimed to address whether single- and double-stranded sperm DNA fragmentation leads to impaired ICSI outcomes in double gamete donation cycles. The study also compared these double-gamete donation cycles to cycles in which only sperm were donated and oocytes were obtained from infertile patients. Two cohorts were included: (a) the Donor-Donor (DD) cohort, which included 27 semen donor samples used in 49 ICSI cycles with young healthy oocyte donors; and (b) the Donor-Infertile (DI) cohort, which involved 34 semen donor samples used in 57 ICSI cycles with oocytes from patients. Single- and double-stranded sperm DNA breaks were determined with alkaline and neutral Comet assays, respectively; ICSI was conducted following standard protocols and embryos were monitored through time-lapse microscopy. In the DD cohort, the percentage of sperm with high overall DNA damage correlated with fertilization rates (Rs = - 0.666; P < 0.001) and with the percentage of blastocysts per injected oocyte (Rs = - 0.414; P = 0.040). In addition, sperm DNA damage delayed the first embryo division (Rs = 0.421; P = 0.036), and development from the 8-cell to the morula stage (Rs = 0.424; P = 0.034). In contrast, double-stranded DNA breaks had no effect in this cohort. As far as the DI cohort is concerned, while overall sperm DNA damage was not found to be correlated to fertilization or blastocyst rates, pronuclei formation following ICSI was delayed when the incidence of double-stranded DNA breaks was high (Rs = 0.485; P = 0.005). In conclusion, this study, which is the first involving double donation cycles (i.e., a donor-donor cohort), supports that sperm DNA damage has a detrimental impact on fertilization rates after ICSI, and delays embryo development. Moreover, the use of oocytes from infertile individuals is suggested to hide the male-factor effect.

Evaluation Of The Clinical Results Of Using Microfluidic Channel System For Sperm Selection In IVF Cycles In Patients With Low Sperm Concentration

Objective: Microfluidic channel system (MAC), a new generation method, gives the chance to select better quality spermatozoa with lower DNA fragmentation indices. This study evaluated the treatment results in patients who underwent ICSI-ET due to the MAC technique's male factors. Methods: Sakarya University ART Center carried out this retrospective study. Patients with 35 male factor indications were included in our study. In these patients, swim-up (SU) was used in the first of two consecutive IVF cycles, and the MAC sperm preparation technique was used in the second. Our study compared fertilization, quality embryo counts, implantation after fresh embryo transfer, pregnancy rates, fifth-day embryo, and frozen embryo numbers. Results: Fertilization rate was higher in the MAC group than in the SU group (P=0.009). The number of 3rd and 5th Day Grade 1 embryo in the MAC group was statistically higher than in the SU group (p=0.000 for both parameters). The number of quality embryos frozen on day 5 was higher in the MAC group than in the SU group (P=0.000). Conclusions: It is thought that MAC application does not make a statistically significant contribution on implantation and pregnancy in IVF cycles performed due to the malefactor. However, it may positively affect fertilization rate and embryo quality. In addition, we think that it increases the number of embryos frozen at the end of the cycle, and for this reason, the MAC technique may provide positive benefits to IVF treatments.

Sperm deoxyribonucleic acid fragmentation (by terminal deoxynucleotidyl transferase biotin dUTP nick end labeling assay) does not impair reproductive success measured as cumulative live birth rates per donor metaphase II oocyte used

OBJECTIVE

To better study the effect of sperm deoxyribonucleic acid fragmentation (SDF) on intracytoplasmic sperm injection (ICSI) outcomes from an ovum donation program by assessing the cumulative live birth rates (CLBRs) per number of embryo transfers (ETs), embryos replaced (EmbR), and metaphase II (MII) oocytes required in consecutive treatments to achieve the first newborn.

DESIGN

A multicenter retrospective cohort study was conducted, and the Kaplan-Meier survival curves were generated to calculate the CLBR with regard to the SDF degree.

SETTING

Private university-affiliated in vitro fertilization centers.

PATIENT(S)

Data from 864 couples using donated eggs and undergoing ICSI from 2000 to 2019 were analyzed. Sperm deoxyribonucleic acid fragmentation was measured using terminal deoxynucleotidyl transferase biotin dUTP nick end labeling assay on their ejaculated sperm.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Live birth rate (LBR) per first ET and per all consecutive ETs within the same patient and CLBR per ET, per EmbR, and per MII oocyte used considering the SDF level.

RESULT(S)

A total of 1,903 ICSI cycles were considered, encompassing 6,340 donated oocytes, 2,543 embryos, and 1,145 ETs. Comparing ≤15% SDF (low) with >15% SDF (high) or by 10% SDF ranges, the LBRs per first ET and per all ETs did not significantly differ. The Kaplan-Meier curves of the CLBR per ET, per EmbR, and per donor oocyte consumed were similar between the SDF groups evaluated.

CONCLUSION(S)

Elevated SDF does not reduce the LBR or cumulative probability to obtain a child when calculated per ET, per EmbR, and per donated MII oocyte used in couples undergoing ICSI cycles.

Sperm DNA damage compromises embryo development, but not oocyte fertilisation in pigs

Background

The assessment of sperm DNA integrity has been proposed as a complementary test to conventional mammalian semen analysis. In this sense, single-strand (SSB) and double-strand (DSB) DNA breaks, the two types of sperm DNA fragmentation (SDF), have been reported to have different aetiologies and to be associated to different fertility outcomes in bovine and humans. Considering that no studies in porcine have addressed how SDF may affect sperm quality and fertility outcomes, the present work aimed to determine the impact of global DNA damage, SSB and DSB on sperm quality and in vitro fertilising ability. To this end, 24 ejaculates (one per boar) were split into three aliquots: the first was used to assess sperm quality parameters through a computer-assisted sperm analysis (CASA) system and flow cytometry; the second was used to perform in vitro fertilisation, and the third, to evaluate sperm DNA integrity using alkaline and neutral Comet assays.

Results

The results showed that global DNA damage negatively correlates (P < 0.05) with normal sperm morphology (R = − 0.460) and progressive motility (R = − 0.419), and positively with the percentage of non-viable sperm (R = 0.507). Multiple regression analyses showed that non-viable sperm were related to SSB (β = − 0.754). In addition, while fertilisation did not seem to be affected by sperm DNA integrity, global DNA damage, DSB and SSB were found to be correlated to embryo development outcomes. Specifically, whereas global DNA damage and DSB negatively affected (P < 0.05) the later preimplantation embryo stages (percentage of early blastocyst/blastocyst D6: for global DNA damage, R = − 0.458, and for DSB, R = − 0.551; and percentage of hatching/hatched blastocyst D6: for global DNA damage, R = − 0.505, and for DSB, R = − 0.447), global DNA damage and SSB had a negative impact (P < 0.05) on the developmental competency of fertilised embryos (R = − 0.532 and R = − 0.515, respectively). Remarkably, multiple regression analyses supported the associations found in correlation analyses. Finally, the present work also found that the inclusion of Comet assays to the conventional sperm quality tests improves the prediction of blastocyst formation (AUC = 0.9021, P < 0.05), but not fertilisation rates (P > 0.05).

Conclusion

Considering all these findings, this work sets a useful model to study how SDF negatively influences fertility.

Functional Aspects of Sperm Chromatin Organization

Sperm nuclei present a highly organized and condensed chromatin due to the interchange of histones by protamines during spermiogenesis. This high DNA condensation leads to almost inert chromatin, with the impossibility of conducting gene transcription as in most other somatic cells. The major chromosomal structure responsible for DNA condensation is the formation of protamine-DNA toroids containing 25-50 kilobases of DNA. These toroids are connected by toroid linker regions (TLR), which attach them to the nuclear matrix, as matrix attachment regions (MAR) do in somatic cells. Despite this high degree of condensation, evidence shows that sperm chromatin contains vulnerable elements that can be degraded even in fully condensed chromatin, which may correspond to chromatin regions that transfer functionality to the zygote at fertilization. This chapter covers an updated review of our model for sperm chromatin structure and its potential functional elements that affect embryo development.

Direct but Not Indirect Methods Correlate the Percentages of Sperm With Altered Chromatin to the Intensity of Chromatin Damage

Although sperm chromatin damage, understood as damage to DNA or affectations in sperm protamination, has been proposed as a biomarker for sperm quality in both humans and livestock, the low incidence found in some animals raises concerns about its potential value. In this context, as separate methods measure different facets of chromatin damage, their comparison is of vital importance. This work aims at analyzing eight techniques assessing chromatin damage in pig sperm. With this purpose, cryopreserved sperm samples from 16 boars were evaluated through the following assays: TUNEL, TUNEL with decondensation, SCSA, alkaline and neutral sperm chromatin dispersion (SCD) tests, alkaline and neutral Comet assays, and chromomycin A3 test (CMA3). In all cases, the extent of chromatin damage and the percentage of sperm with fragmented DNA were determined. The degree of chromatin damage and the percentage of sperm with fragmented DNA were significantly correlated (p < 0.05) in direct methods (TUNEL, TUNEL with decondensation, and alkaline and neutral Comet) and CMA3, but not in the indirect ones (SCD and SCSA). Percentages of sperm with fragmented DNA determined by alkaline Comet were significantly (p < 0.05) correlated with TUNEL following decondensation and CMA3; those determined by neutral Comet were correlated with the percentage of High DNA Stainability (SCSA); those determined by SCSA were correlated with neutral and alkaline SCD; and those determined by neutral SCD were correlated with alkaline SCD. While, in pigs, percentages of sperm with fragmented DNA are directly related to the extent of chromatin damage when direct methods are used, this is not the case for indirect techniques. Thus, the results obtained herein differ from those reported for humans in which TUNEL, SCSA, alkaline SCD, and alkaline Comet were found to be correlated. These findings may shed some light on the interpretation of these tests and provide some clues for the standardization of chromatin damage methods.

Comparison of fresh and frozen ejaculated spermatozoa in sibling oocyte recipient cycles

RESEARCH QUESTION

Do IVF and intracytoplasmic sperm injection cycles using fresh and frozen ejaculated spermatozoa result in similar pregnancy outcomes in couples with non-male factor infertility?

DESIGN

Retrospective cohort study; patients undergoing donor egg recipient cycles, in which oocytes from a single ovarian stimulation were split between two recipients, were reviewed. Two recipients of oocytes from a single donor were paired and categorized based on the type of ejaculated spermatozoa (fresh/frozen). Outcomes included delivery rate, implantation, pregnancy, pregnancy loss and fertilization rates.

RESULTS

Of the 408 patients who received oocytes from a split donor oocyte cycle, 45 pairs of patients used discrepant types of ejaculated spermatozoa and were included in the study. Fertilization rate: fresh (74.8%); frozen (68.6%) (P = 0.13). Pregnancy rate: fresh (76%); frozen (67%); delivery rate: fresh (69%); frozen (44%); implantation rate was significantly higher: fresh (64%); frozen (36%) (P = 0.04). Rate of pregnancy loss was significantly higher in the frozen group compared with the fresh group (33% versus 5.9%, P = 0.013). Adjusted odds for delivery was 67% lower in the frozen group (95% CI 0.12, 0.89). Adjusted odds of pregnancy (adjusted OR 0.67, 95% CI 0.20, 2.27) and implantation (adjusted OR 0.5, 95% CI 0.12, 2.12) were not significantly different between the frozen and fresh sperm groups.

CONCLUSION

In this model that controls for oocyte quality by using paired recipients from the same donor, frozen ejaculated spermatozoa resulted in lower delivery rates than those using fresh spermatozoa.

A microfluidic sperm-sorting device reduces the proportion of sperm with double-stranded DNA fragmentation

Sperm DNA fragmentation can be produced in one (ssSDF) or both (dsSDF) DNA strands, linked to difficulties in naturally achieving a pregnancy and recurrent miscarriages, respectively. The techniques more frequently used to select sperm require centrifugation, which may induce sperm DNA fragmentation (SDF). The objective of this study was to assess whether the microfluidic-based device FertileChip® (now ZyMot®ICSI) can diminish the proportion of sperm with dsSDF. First, in a blinded split pilot study, the semen of nine patients diagnosed with ≥60% dsSDF, was divided into three aliquots: not processed, processed with FertileChip®, and processed with swim up. The three aliquots were all analyzed using neutral COMET for the detection of dsSDF, resulting in a reduction of 46% (P < 0.001) with FertileChip® (dsSDF: 34.9%) compared with the ejaculate and the swim up (dsSDF: 65%). Thereafter, the FertileChip® was introduced into clinical practice and a cohort of 163 consecutive ICSI cycles of patients diagnosed with ≥60% dsSDF was analyzed. Fertilization rate was 75.41%. Pregnancy rates after the first embryo transfer were 53.2% (biochemical), 37.8% (clinical), 34% (ongoing) and the live birth rate was 28.8%. Cumulative pregnancy rates after one (65.4% of patients), two (27.6% of patients) or three (6.4% of patients) transfers were 66% (biochemical), 56.4% (clinical), 53.4% (ongoing) and the live birth rate was 42%. The selection of spermatozoa using Fertile Chip® significantly diminishes the percentage of dsSDF, compared with either the fresh ejaculate or after swim up. Its applicability in ICSI cycles of patients with high dsSDF resulted in good laboratory and clinical outcomes.