The ability of sperm selection techniques to remove single- or double-strand DNA damage

DNA fragmentation of lymphocytes and sperm cells induced by nickel released from orthodontic archwires: A preliminary study

Orthodontic brackets and archwires placed intraorally are subject to corrosion, leading to the release of cytotoxic metal ions. The aim of this study was to determine whether the use of orthodontic NiTi archwires increases systemic Ni levels and cause alterations on the DNA of cells unrelated to the oral environment such as lymphocytes and sperm cells. Human urine, semen and blood samples were collected before (baseline) sham placement of orthodontic archwires and 15 and 30 days after placement. Lymphocytes and sperm cells cells were evaluated by comet assay. Ni concentration levels in urine increased significantly between baseline and 15 days (p<0.01) and 15 and 30 days of exposure (p<0.01). Progressive decrease in sperm viability and motility was observed between the sampling periods. Lymphocytes and sperm cells showed DNA fragmentation. The increase in systemic concentration of nickel induced structural damage in the DNA of lymphocytes and human sperm cells.

Advanced Sperm Selection Techniques for Assisted Reproduction

Male infertility accounts for approximately 40% of infertility cases. There are many causes of male infertility, including environmental factors, age, lifestyle, infections, varicocele, and cancerous pathologies. Severe oligozoospermia, cryptozoospermia, and azoospermia (obstructive and non-obstructive) are identified as severe male factor infertility, once considered conditions of sterility. Today, in vitro fertilization (IVF) techniques are the only treatment strategy in cases of male factor infertility for which new methodologies have been developed in the manipulation of spermatozoa to achieve fertilization and increase success rates. This review is an update of in vitro manipulation techniques, in particular sperm selection, emphasizing clinical case-specific methodology. The success of an IVF process is related to infertility diagnosis, appropriate choice of treatment, and effective sperm preparation and selection. In fact, selecting the best spermatozoa to guarantee an optimal paternal heritage means increasing the blastulation, implantation, ongoing pregnancy and live birth rates, resulting in the greater success of IVF techniques.

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.

Efficacy of density gradient centrifugation technique (DGC) in enhancing sperm cell DNA quality for assisted reproductive technique

Objective

Density gradient centrifugation (DGC) is commonly used for sperm preparation before assisted reproductive technology (ART) procedures. This technique separates superior motile spermatozoa with normal morphology from the total sperm population. However, there is still controversy as to the effects of this sperm separation technique on sperm cell DNA integrity which is a determining element in the process of fertilization and embryonic development.

The objective of this study was to determine the effects of DGC on sperm cell DNA integrity as assessed by a novel association between two cytogenetic tests.

Study designs

Semen samples were collected from 30 fertile donors and 40 patients being candidates for ART treatment. Each sample was divided into two parts: the first portion was subjected to selection by two layers of DGC (45% and 90%) and the second fraction was rinsed with phosphate-buffered saline solution and centrifuged without density gradient.

Abnormal sperm chromatin structure as evaluated by a sperm chromatin dispersion (SCD) test and DNA denaturation as assessed by an acridine orange (AO) test were monitored in the initially washed sample and in the different layers of the density gradient centrifugation.

Results

DGC significantly improved the proportion of sperm progressive motility, total motility, and sperm morphology. Moreover, following density gradient centrifugation, the proportion of spermatozoa with denaturated DNA significantly decreased when compared with whole semen (p < 0.001). In addition, we found that spermatozoa isolated in the 90% layer possessed a significantly lower percentage of sperm chromatin decondensation when compared with those remaining in the 45% layer and unprocessed semen (p < 0.001).

Conclusions

Using double cytogenetic tests, our study shows that semen processing by density gradient centrifugation is useful in selecting sperm with higher double-strand DNA integrity and recommended to be used in sperm preparation for assisted reproduction.

Sperm DNA damage in men with spinal cord injury: the relative incidence of single- and double-strand DNA breaks

BACKGROUND

Men with spinal cord injury (SCI) show a high proportion of sperm DNA damage in their ejaculate but the underlying pathology remains elusive.

OBJECTIVE

To investigate the relative incidence of single (SSBs) and double-strand DNA breaks (DSBs) and DNase activity in men with SCI.

MATERIALS AND METHODS

This study included ejaculates of 20 men with SCI and 27 normozoospermic (sperm donors). A TwoTails comet assay (TTComet) allowed visualization of three categories of sperm DNA damage corresponding to SSBs, DSBs and those with a combination of SSBs and DSBs, facilitating accurate calculation of the total proportion of SSBs and DSBs. A subset of 15 individuals (sperm donors and SCI patients) was used to test for DNase activity in the seminal plasma.

RESULTS

While the proportion of DSBs in men with SCI (median-57.5%) was higher (P = 0.000) than normozoospermic samples (median-4.6%), the proportion of SSBs was higher (P = 0.022) in the normozoospermic ejaculates (median-6.0%) compared to men with SCI (median-2.5%). The relative proportion of the total DSBs with respect to the total SSBs was 3.3× in men with SCI but 0.9× in normozoospermic samples. We further confirmed the high DNase activity in the seminal plasma of men with SCI.

DISCUSSION

The TTComet assay provided new insights to the pathology of sperm DNA in men with SCI and may have diagnostic value in developing sperm selection methodologies to reduce DSBs prior to ART.

CONCLUSION

Men with SCI are characterized by a high proportion of sperm with DSBs and high levels of DNase activity in the seminal plasma compared to normozoospermic men.

Effects of sperm preparation techniques on sperm survivability and DNA fragmentation

OBJECTIVE

This study was performed to determine the effect of swim-up (SU) and density gradient centrifugation (DGC) on sperm survival and DNA fragmentation.

METHODS

Individual semen samples were analyzed before each was divided into two aliquots (half for SU and half for DGC) for calculation of sperm survival and the DNA fragmentation index (DFI). Sperm DNA fragmentation was determined using the sperm chromatin dispersion test.

RESULTS

The DFI of the 63 semen samples processed using both procedures was lower than that of the fresh semen samples. The DFI was significantly lower for samples processed using the SU than DGC method. In the sperm survival test, the SU technique was associated with increased sperm motility and vitality following preparation. After 24 hours, however, the concentration and percentage of surviving sperm were significantly lower in the SU than DGC group.

CONCLUSIONS

Both semen preparation techniques help to minimize sperm DNA fragmentation; however, when the DFI is <30%, the SU technique is more appropriate than DGC. While DGC may be superior for intrauterine insemination, the SU method may be preferable for in vitro fertilization or maturation.

Male age: negative impact on sperm DNA fragmentation

The main goal of semen processing in Assisted Reproductive Techniques (ART) is to select sperm with good viability and, at the same time, remove Reactive Oxygen Species (ROS) sources (such as leukocytes) and reduce the percentage of morphologically abnormal sperm for fertility treatment. We performed a comparative analysis on sperm DNA fragmentation after Density Gradient Centrifugation (DGC) using products sold by two competing companies. Our results showed comparable DNA Fragmentation Index (DFI) after treatment with both DGC products. However, in both cases, a comparable number of samples do not benefit from the treatment. Interestingly, increasing evidences indicated that male age has a negative impact on sperm DNA fragmentation, but the mechanisms underlying age-dependent patterns of sperm decline have not yet been fully understood. Thus, we performed a comparative analysis of DFI before and after treatment with DGC products in age-stratified sample populations. Our results showed a worsening of the baseline DFI in the eldest group and the benefits of DGC on sperm DNA were compromised. In conclusion, our work consolidates the current evidences suggesting that both paternal and maternal aging, critically affects reproductive success.

Single-cell sperm transcriptomes and variants from fathers of children with and without autism spectrum disorder

The human sperm is one of the smallest cells in the body, but also one of the most important, as it serves as the entire paternal genetic contribution to a child. Investigating RNA and mutations in sperm is especially relevant for diseases such as autism spectrum disorders (ASD), which have been correlated with advanced paternal age. Historically, studies have focused on the assessment of bulk sperm, wherein millions of individual sperm are present and only high-frequency variants can be detected. Using 10× Chromium single-cell sequencing technology, we assessed the transcriptome from >65,000 single spermatozoa across six sperm donors (scSperm-RNA-seq), including two who fathered multiple children with ASD and four fathers of neurotypical children. Using RNA-seq methods for differential expression and variant analysis, we found clusters of sperm mutations in each donor that are indicative of the sperm being produced by different stem cell pools. Finally, we have shown that genetic variations can be found in single sperm.

A treatment approach for couples with disrupted sperm DNA integrity and recurrent ART failure

OBJECTIVE

To test a novel method to select spermatozoa with high chromatin integrity.

DESIGN

Specimens with high sperm chromatin fragmentation (SCF) were selected by density gradient selection (DGS) and microfluidic sperm sorting (MSS).

SETTING

Academic medical center.

PATIENT(S)

Ejaculates from consenting men were processed by DGS/MSS. Couples underwent ICSI cycles with spermatozoa processed by DGS/MSS. Clinical outcomes were evaluated after embryo transfer.

INTERVENTION(S)

SCF was measured by TUNEL. ICSI with spermatozoa selected by DGS and MSS was performed.

MAIN OUTCOME MEASURE(S)

Fertilization, embryo implantation, and pregnancy outcomes were compared between DGS and MSS.

RESULT(S)

A total of 23 men had an average SCF of 20.7 ± 10%. After DGS and MSS, the SCF was 12.5 ± 5% and 1.8 ± 1%, respectively. In couples who underwent ICSI, the average SCF was 28.8 ± 9%, which fell to 21.0 ± 9% after DGS and 1.3 ± 0.7% after MSS. Four couples underwent 11 ICSI cycles with DGS and achieved one (25%) pregnancy that resulted in pregnancy loss. In four subsequent ICSI cycles with MSS, an ongoing clinical pregnancy rate of 50% was achieved. Five additional couples underwent 12 cycles of ICSI with DGS. After preimplantation genetic testing for aneuploidy, 30.3% of the embryos were euploid. One pregnancy was achieved, resulting in pregnancy loss. With MSS, 31.5% of the embryos were euploid and 4 couples obtained a pregnancy. Finally, sixteen couples underwent 20 ICSI cycles solely with MSS at our center. Of these couples, 8 had failed 13 ICSI cycles with DGS elsewhere. These couples achieved an overall implantation of 34.5% (10/29) and a pregnancy rate of 58.8% (10/17).

CONCLUSION(S)

Microfluidic selection yielded spermatozoa with optimal genomic integrity and improved chances of obtaining a euploid conceptus.

Evaluation of normal morphology, DNA fragmentation, and hyaluronic acid binding ability of human spermatozoa after using four different commercial media for density gradient centrifugation

Objective

Density gradient centrifugation (DGC) is frequently used to isolate high-motility fractions of spermatozoa. We compared the efficacy of four DGC media in terms of the percentage of morphologically normal spermatozoa, DNA fragmentation level, and hyaluronic acid (HA) binding ability.

Methods

Thirty men with a total motile spermatozoa count >80 million participated. Semen samples were divided into four aliquots, which were processed using PureSperm, PureCeption, Sidney, and SpermGrad media, respectively. The DNA fragmentation level was measured using the Halosperm assay kit and HA binding ability was measured using the HBA assay kit.

Results

The mean percentage of morphologically normal spermatozoa was significantly enhanced after DGC using all four media (10.3%, 9.9%, 9.8%, and 10.7%, respectively; p<0.05 for each when compared with 6.9% in raw semen). The DNA fragmentation level was significantly reduced after DGC using PureSperm, PureCeption, and SpermGrad media (6.0%, 6.5%, and 4.9%, respectively; p<0.05 for each when compared with 11.2% in raw semen), but not after DGC using Sidney media (8.5%, p>0.05). HA binding ability did not change after DGC using any of the four media.

Conclusion

The four media were equally effective for obtaining a sperm fraction with highly motile, morphologically normal sperm. PureSperm, PureCeption, and SpermGrad media were equally effective for acquiring a sperm fraction with less DNA fragmentation.

Sperm DNA fragmentation and sex chromosome aneuploidy after swim-up versus density gradient centrifugation

OBJECTIVE

The aim of this study was to compare the efficacy of swim-up and density gradient centrifugation (DGC) for reducing the amount of sperm with fragmented DNA, sex chromosome aneuploidy, and abnormal chromatin structure.

METHODS

Semen samples were obtained from 18 healthy male partners who attended infertility clinics for infertility investigations and were processed with swim-up and DGC. The percentages of sperm cells with fragmented DNA measured by the sperm chromatin dispersion test, normal sex chromosomes assessed by fluorescence in situ hybridization, and abnormal chromatin structure identified by toluidine blue staining were examined.

RESULTS

The percentage of sperm cells with fragmented DNA was significantly lower in the swim-up fraction (9.7%, p=0.001) than in the unprocessed fraction (27.0%), but not in the DGC fraction (27.8%, p=0.098). The percentage of sperm cells with normal X or Y chromosomes was comparable in the three fractions. The percentage of sperm cells with abnormal chromatin structure significantly decreased after DGC (from 15.7% to 10.3%, p=0.002). The swim-up method also tended to reduce the percentage of sperm cells with abnormal chromatin structure, but the difference was not significant (from 15.7% to 11.6%, p=0.316).

CONCLUSION

The swim-up method is superior for enriching genetically competent sperm.

ICSI significantly improved the pregnancy rate of patients with a high sperm DNA fragmentation index

Objective

Correlations between semen parameters and sperm DNA fragmentation index (DFI) were investigated to identify characteristics of sperm without DNA damage that could be used in selecting sperm for intracytoplasmic sperm injection (ICSI). Pregnancy outcomes were compared to determine whether in vitro fertilization (IVF) or ICSI is a better choice for patients who have sperm with a high-DFI.

Methods

Semen analysis was carried out in 388 patients who visited our IVF center for the first time to investigate correlations between sperm DFI and semen parameters. In addition, 1,102 IVF cycles in 867 patients were carried out in the present study; 921 cycles in the low-DFI group (DFI <30%) and 181 cycles in the high-DFI group (DFI ≥30%). Both the low- and high-DFI groups were subdivided into IVF and ICSI cycle groups.

Results

Sperm DFI showed significant inverse correlations with sperm motility (r=−0.435, p<0.001) and morphology (r=−0.153, p<0.05). Sperm DFI also showed significant correlations with rapid motility (r=−0.436, p<0.001), and the kinetic parameters of average-path velocity (r=−0.403) and linearity (r=−0.412). Although there was no significant difference in the pregnancy rates between IVF (48.6%) and ICSI (44.8%) in the low-DFI group, the pregnancy rate of ICSI cycles (44.8%, p<0.05) was significantly higher than IVF cycles (25.0%) in the high-DFI group. No significant difference was observed in the abortion rates between the low-DFI (52 of 921, 5.6%) and high-DFI groups (7 of 181, 3.8%).

Conclusion

ICSI is a better choice than IVF for improving the pregnancy outcomes of patients who have sperm with a high DFI.

Efficient isolation of sperm with high DNA integrity and stable chromatin packaging by a combination of density-gradient centrifugation and magnetic-activated cell sorting

OBJECTIVE

This study was carried out to investigate the correlations of the sperm DNA fragmentation index (DFI) with semen parameters and apoptosis, and to investigate the effects of density-gradient centrifugation (DGC) and magnetic-activated cell sorting (MACS) on reducing the proportion of sperm with DNA fragmentation and protamine deficiency.

METHODS

Semen analysis and a sperm DNA fragmentation assay were performed to assess the correlations between semen parameters and the DFI in 458 semen samples. Sperm with progressive motility or non-apoptosis were isolated by DGC or MACS, respectively, in 29 normozoospermic semen samples. The effects of DGC or MACS alone and of DGC and MACS combined on reducing the amount of sperm in the sample with DNA fragmentation and protamine deficiency were investigated.

RESULTS

The sperm DFI showed a significant correlation (r=-0.347, p<0.001) with sperm motility and morphology (r=-0.114, p<0.05) but not with other semen parameters. The DFI (11.5%±2.0%) of semen samples was significantly reduced by DGC (8.1%±4.1%) or MACS alone (7.4%±3.9%) (p<0.05). The DFI was significantly further reduced by a combination of DGC and MACS (4.1%±1.3%, p<0.05). Moreover, the combination of DGC and MACS (1.6%±1.1%, p<0.05) significantly reduced the protamine deficiency rate of semen samples compared to DGC (4.4%±3.2%) or MACS alone (3.4%±2.2%).

CONCLUSION

The combination of DGC and MACS may be an effective method to isolate high-quality sperm with progressive motility, non-apoptosis, high DNA integrity, and low protamine deficiency in clinical use.

An Update on Oxidative Damage to Spermatozoa and Oocytes

On the one hand, reactive oxygen species (ROS) are mandatory mediators for essential cellular functions including the function of germ cells (oocytes and spermatozoa) and thereby the fertilization process. However, the exposure of these cells to excessive levels of oxidative stress by too high levels of ROS or too low levels of antioxidative protection will render these cells dysfunctional thereby failing the fertilization process and causing couples to be infertile. Numerous causes are responsible for the delicate bodily redox system being out of balance and causing disease and infertility. Many of these causes are modifiable such as lifestyle factors like obesity, poor nutrition, heat stress, smoking, or alcohol abuse. Possible correctable measures include foremost lifestyle changes, but also supplementation with antioxidants to scavenge excessive ROS. However, this should only be done after careful examination of the patient and establishment of the individual bodily antioxidant needs. In addition, other corrective measures include sperm separation for assisted reproductive techniques. However, these techniques have to be carried out very carefully as they, if applied wrongly, bear risks of generating ROS damaging the germ cells and preventing fertilization.

Sperm quality after density gradient centrifugation with three commercially available media: a controlled trial

BACKGROUND

Density gradient is the preferred technique for sperm processing for ART. However, no study has examined sperm quality using different processing media simultaneously and under identical conditions. Therefore, we evaluated semen quality following sperm preparation by three commonly used commercially available density gradient media in a well-designed controlled trial.

METHODS

We obtained semen samples from 20 healthy volunteers. Percent motility, total motile sperm (TMS), % recovery and DNA damage were assessed before and after separation in three different sperm density gradient media-PureCeption, ISolate and SpermGrad-125.

RESULTS

Percent motility was higher in the ISolate (81.4% ± 6.6%) and SpermGrad-125 samples (85.7% ± 8.0%) (P < 0.0001) than in the PureCeption samples (62.5% ± 13.2%) (P = 0.07). TMS was higher in the PureCeption(TM) and ISolate samples (14.2% ± 15.9% and 15.8% ± 18.2%) than in those prepared with SpermGrad-125 (10.6% ± 19.7%) (P < 0.0001). Percent recovery was significantly higher in the PureCeption(TM) and ISolate samples (45.3% and 48.9%) than in the SpermGrad-125(TM) samples (30.8%) (P < 0.01). DNA fragmentation was comparable across the three gradients (PureCeption = 8.8% ± 4.7%; ISolate = 7.2 ± 5.2% and SpermGrad-125 = 11.2% ± 7.4%).

CONCLUSIONS

Three different density gradient processing media PureCeption, ISolate, and SpermGrad-125 were examined for their effects on sperm quality. Sperm processed by ISolate and Sperm Grad 125 had better motility and TMS after processing. The extent of DNA damage was comparable in all three gradients.

Interpreting sperm DNA damage in a diverse range of mammalian sperm by means of the two-tailed comet assay

Key Concepts

The two-dimensional Two-Tailed Comet assay (TT-comet) protocol is a valuable technique to differentiate between single-stranded (SSBs) and double-stranded DNA breaks (DSBs) on the same sperm cell.

Protein lysis inherent with the TT-comet protocol accounts for differences in sperm protamine composition at a species-specific level to produce reliable visualization of sperm DNA damage.

Alkaline treatment may break the sugar–phosphate backbone in abasic sites or at sites with deoxyribose damage, transforming these lesions into DNA breaks that are also converted into ssDNA. These lesions are known as Alkali Labile Sites “ALSs.”

DBD–FISH permits the in situ visualization of DNA breaks, abasic sites or alkaline-sensitive DNA regions.

The alkaline comet single assay reveals that all mammalian species display constitutive ALS related with the requirement of the sperm to undergo transient changes in DNA structure linked with chromatin packing.

Sperm DNA damage is associated with fertilization failure, impaired pre-and post- embryo implantation and poor pregnancy outcome.

The TT is a valuable tool for identifying SSBs or DSBs in sperm cells with DNA fragmentation and can be therefore used for the purposes of fertility assessment.

Sperm DNA damage is associated with fertilization failure, impaired pre-and post- embryo implantation and poor pregnancy outcome. A series of methodologies to assess DNA damage in spermatozoa have been developed but most are unable to differentiate between single-stranded DNA breaks (SSBs) and double-stranded DNA breaks (DSBs) on the same sperm cell. The two-dimensional Two-Tailed Comet assay (TT-comet) protocol highlighted in this review overcomes this limitation and emphasizes the importance in accounting for the difference in sperm protamine composition at a species-specific level for the appropriate preparation of the assay. The TT-comet is a modification of the original comet assay that uses a two dimensional electrophoresis to allow for the simultaneous evaluation of DSBs and SSBs in mammalian spermatozoa. Here we have compiled a retrospective overview of how the TT-comet assay has been used to investigate the structure and function of sperm DNA across a diverse range of mammalian species (eutheria, metatheria, and prototheria). When conducted as part of the TT-comet assay, we illustrate (a) how the alkaline comet single assay has been used to help understand the constitutive and transient changes in DNA structure associated with chromatin packing, (b) the capacity of the TT-comet to differentiate between the presence of SSBs and DSBs (c) and the possible implications of SSBs or DSBs for the assessment of infertility.

Rapid selection of sperm with high DNA integrity

Sperm selection is essential to assisted reproductive technology (ART), influencing treatment outcomes and the health of offspring. The fundamental challenge of sperm selection is dictated by biology: a heterogeneous population of ~10(8) sperm per milliliter with a short lifetime in vitro. However, conventional sperm selection approaches result in less than 50% improvement in DNA integrity. Here, a clinically applicable microfluidic device is presented that selects sperm based on the progressive motility in 500 parallel microchannels. The result is a one-step procedure for semen purification and high DNA integrity sperm selection from 1 mL of raw semen in under 20 minutes. Experiments with bull sperm indicate more than 89% improvement in selected sperm vitality. Clinical tests with human sperm show more than 80% improvement in human DNA integrity, significantly outperforming the best current practices. These results demonstrate the presence of a sub-population of sperm with nearly intact chromatin and DNA integrity, and a simple clinically-applicable lab-on-a-chip method to select this population.

Can DNA fragmentation of neat or swim-up spermatozoa be used to predict pregnancy following ICSI of fertile oocyte donors?

This study compared the potential of assessing sperm DNA fragmentation (SDF) from neat semen and the subsequent swim-up (SU) procedure to predict pregnancy when conducting ICSI of fertile donor oocytes. Infertile females (n=81) were transferred embryos resulting from intracytoplasmic sperm injection (ICSI) of their partner's spermatozoa and proven donor oocytes. This model normalized the impact of female factor in putative sperm DNA repair. Semen was blindly assessed for SDF using Halosperm immediately following ejaculation (NS) and after swim-up at the time of ICSI fertilisation. There was a decrease in SDF values of the ejaculated semen sample following the swim-up protocol (P=0.000). Interestingly, pregnancy could be equally predicted from SDF values derived from either neat or swim-up semen samples. Receiver operator curves and the derived Youden's indices determined SDF cutoff values for NS and SU of 24.8% and 17.5%, respectively. Prediction of pregnancy from NS SDF had a sensitivity of 75% and a specificity of 69%, whereas for SU SDF was 78% and 73%, respectively. While increased levels of SDF negatively impact reproductive outcome, we have shown that a reduction in SDF following sperm selection using ICSI with proven donor oocytes is not mandatory for achieving pregnancy. This suggests that a certain level of DNA damage that is not detectable using current technologies could be impacting on the relative success of assisted reproductive technology (ART) procedures. Consequently, we propose a modification of the so called 'iceberg model' as a possible rationale for understanding the role of SDF in reproductive outcome.

Intracytoplasmic morphologically selected sperm injection outcomes: the role of sperm preparation techniques

PURPOSE

To compare the results of intracytoplasmic morphologically selected sperm injection (IMSI) between cycles in which the swim-up (SUP) or the density gradient centrifugation (DGC) techniques were used for sperm preparation.

METHODS

We evaluated 70 IMSI cycles performed in women with age ≤ 37 years, undergoing IMSI as result of male factor. The couples were divided into two groups: DGC group (n = 26) and SUP group (n = 44). The groups were compared with regard to IMSI outcomes.

RESULTS

There were no significant differences between SUP and DGC groups regarding the number of follicles, oocytes, mature oocytes, oocyte yield and mature oocyte rate. Fertilization rate and high-quality embryos rate on day 5 of development were similar between SUP and DGC groups. Implantation, pregnancy and miscarriage rates were not statistically different between SUP and DGC groups (28.8 vs 33.3 %, 46.2 vs 57.1 % and 8.3 vs 4.2 %, respectively).

CONCLUSIONS

Both the SUP and the DGC techniques recover improved sperm fractions and result in similar IMSI outcomes. Further randomized trials analyzing both the quality of sperm through MSOME and the IMSI outcomes are needed to elucidate the role of sperm preparation techniques and morphology on IMSI outcomes.