Selection of normal spermatozoa with a vacuole-free head (x6300) improves selection of spermatozoa with intact DNA in patients with high sperm DNA fragmentation rates

First-line infertility treatment in normal or subnormal sperm: Interest of a simplified pre-IMSI test

BACKGROUND

In the field of male infertility, when sperm is normal/subnormal, a few "add-on" routine tests can complete the basic semen examination.

OBJECTIVES

The aim of this study was to develop and evaluate a faster, simplified motile sperm organelle morphology examination (MSOME) technique for selected infertile patients with apparently normal/subnormal sperm and, in their background: failure of two or three intrauterine insemination (IUI) cycles, repeatedly fragmented embryos, embryonic development to blastocyst-stage failures, repeated miscarriages, a long period of infertility or 2 or more IVF attempts without pregnancy. Our test results were correlated with IUI, conventional in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI) and intracytoplasmic morphologically selected sperm injection (IMSI) outcomes.

MATERIALS AND METHODS

We validated an adapted version of the MSOME analysis called the pre-IMSI test (PIT), based on vacuole evaluation alone. 248 infertile patients from our assisted reproductive technology (ART) Center were retrospectively selected and split into three PIT score subgroups (patients with ≤8% (score I), 9 to 15% (score II) and ≥16% normal spermatozoa (score III)) based on the correlation between PIT results and each ART technique outcome. The choice of one or another of these ART techniques had been made according to the usual clinico-biological criteria.

RESULTS

Clinical outcomes for each of the three PIT subgroups were compared individually for the different ART techniques. For ICSI, the effect of the PIT score subgroup was significant for clinical pregnancies (p = 0.0054) and presented a trend for live births (p = 0.0614). Miscarriage rates of IVF attempts were statistically different depending on the PIT score (p = 0.0348). Furthermore, the odds ratios of clinical pregnancy rates were significantly different according to PIT score subgroup when comparing ICSI vs. IMSI or IVF vs. ICSI attempts.

DISCUSSION

IMSI appears to be recommended when sperm belongs to PIT score I, ICSI when it belongs to PIT score II and IVF or IUI when sperm is of PIT score III quality in selected infertile couples. The lack of statistical power in these PIT subgroups means that we must remain cautious in interpreting results.

CONCLUSION

Our results support the interest of this simplified test for certain couples with normal/subnormal sperm to help choose the most efficient ART technique, even as first-line treatment.

Human Sperm Morphology as a Marker of Its Nuclear Quality and Epigenetic Pattern

Background: Human sperm chromatin condensation is a sum of epigenetic events that allows for the near-complete replacement of histones with protamines. Under high-magnification microscopy, nuclear vacuoles have been described as thumbprints with poor chromatin condensation. The objective of this study is to examine whether vacuolated spermatozoa carry specific epigenetic marks, which may influence embryo development. Methods: The presence and three-dimensional distribution of ten epigenetic marks (protamine-P2, histone-H3, H3K4me1/me2/me3, H3K9me1/me2/me3, H3K27me3, H4k20me2) were evaluated and compared in morphometrically normal spermatozoa according to the presence or absence of a large vacuole occupying more than 15% of the head surface (n = 4193). Results: Vacuolated spermatozoa were significantly more frequently labelled with H3 and H3K4me3 than normal spermatozoa (88.1% ± 2.7 and 78.5% ± 5.2 vs. 74.8% ± 4.8 and 49.1% ± 7.4, respectively; p = 0.009 and p < 0.001) and significantly less marked by P2 and H3K27me3 (50.2% ± 6.2 and 63.9% ± 6.3 vs. 82.1% ± 4.4 and 73.6% ± 5.1, respectively; p < 0.001 and p = 0.028). In three dimensions, vacuoles are nuclear concavities filled with DNA carrying the H3K4me3 marker. Conclusion: High-magnification microscopy is a simple tool to estimate in real time the sperm epigenetic profile. The selection of normal spermatozoa without vacuoles and the deselection of spermatozoa with vacuoles appear to be epigenetically favorable to embryo development and safe offspring.

Simulating nature in sperm selection for assisted reproduction

Sperm selection in the female reproductive tract (FRT) is sophisticated. Only about 1,000 sperm out of millions in an ejaculate reach the fallopian tube and thus have a chance of fertilizing an oocyte. In assisted reproduction techniques, sperm are usually selected using their density or motility, characteristics that do not reflect their fertilization competence and, therefore, might result in failure to fertilize the oocyte. Although sperm processing in in vitro fertilization (IVF) and intrauterine insemination (IUI) bypasses many of the selection processes in the FRT, selection by the cumulus mass and the zona pellucida remain intact. By contrast, the direct injection of a sperm into an oocyte in intracytoplasmic sperm injection (ICSI) bypasses all natural selection barriers and, therefore, increases the risk of transferring paternal defects such as fragmented DNA and genomic abnormalities in sperm to the resulting child. Research into surrogate markers of fertilization potential and into simulating the natural sperm selection processes has progressed. However, methods of sperm isolation - such as hyaluronic acid-based selection and microfluidic isolation based on sperm tactic responses - use only one or two parameters and are not comparable with the multistep sperm selection processes naturally occurring within the FRT. Fertilization-competent sperm require a panel of molecules, including zona pellucida-binding proteins and ion channel proteins, that enable them to progress through the FRT to achieve fertilization. The optimal artificial sperm selection method will, therefore, probably need to use a multiparameter tool that incorporates the molecular signature of sperm with high fertilization potential, and their responses to external cues, within a microfluidic system that can replicate the physiological processes of the FRT in vitro.

Molecular Profiling of Spermatozoa Reveals Correlations between Morphology and Gene Expression: A Novel Biomarker Panel for Male Infertility

Choosing spermatozoa with an optimum fertilizing potential is one of the major challenges in assisted reproductive technologies (ART). This selection is mainly based on semen parameters, but the addition of molecular approaches could allow a more functional evaluation. To this aim, we used sixteen fresh sperm samples from patients undergoing ART for male infertility and classified them in the high- and poor-quality groups, on the basis of their morphology at high magnification. Then, using a DNA sequencing method, we analyzed the spermatozoa methylome to identify genes that were differentially methylated. By Gene Ontology and protein-protein interaction network analyses, we defined candidate genes mainly implicated in cell motility, calcium reabsorption, and signaling pathways as well as transmembrane transport. RT-qPCR of high- and poor-quality sperm samples allowed showing that the expression of some genes, such as AURKA, HDAC4, CFAP46, SPATA18, CACNA1C, CACNA1H, CARHSP1, CCDC60, DNAH2, and CDC88B, have different expression levels according to sperm morphology. In conclusion, the present study shows a strong correlation between morphology and gene expression in the spermatozoa and provides a biomarker panel for sperm analysis during ART and a new tool to explore male infertility.

Advances in sperm analysis: techniques, discoveries and applications

Infertility affects one in six couples worldwide, and fertility continues to deteriorate globally, partly owing to a decline in semen quality. Sperm analysis has a central role in diagnosing and treating male factor infertility. Many emerging techniques, such as digital holography, super-resolution microscopy and next-generation sequencing, have been developed that enable improved analysis of sperm motility, morphology and genetics to help overcome limitations in accuracy and consistency, and improve sperm selection for infertility treatment. These techniques have also improved our understanding of fundamental sperm physiology by enabling discoveries in sperm behaviour and molecular structures. Further progress in sperm analysis and integrating these techniques into laboratories and clinics requires multidisciplinary collaboration, which will increase discovery and improve clinical outcomes.

Sperm Oxidative Stress during In Vitro Manipulation and Its Effects on Sperm Function and Embryo Development

Reactive oxygen species (ROS) generated at low levels during mitochondrial respiration have key roles in several signaling pathways. Oxidative stress (OS) arises when the generation of ROS exceeds the cell's antioxidant scavenging ability and leads to cell damage. Physiological ROS production in spermatozoa regulates essential functional characteristics such as motility, capacitation, acrosome reaction, hyperactivation, and sperm-oocyte fusion. OS can have detrimental effects on sperm function through lipid peroxidation, protein damage, and DNA strand breakage, which can eventually affect the fertility of an individual. Substantial evidence in the literature indicates that spermatozoa experiencing OS during in vitro manipulation procedures in human- and animal-assisted reproduction are increasingly associated with iatrogenic ROS production and eventual impairment of sperm function. Although a direct association between sperm OS and human assisted reproductive techniques (ART) outcomes after in vitro fertilization (IVF) and/or intracytoplasmic sperm injection (ICSI) is still a matter of debate, studies in animal models provide enough evidence on the adverse effects of sperm OS in vitro and defective fertilization and embryo development. This review summarized the literature on sperm OS in vitro, its effects on functional ability and embryo development, and the approaches that have been proposed to reduce iatrogenic sperm damage and altered embryonic development.

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

PURPOSE

To detect a possible bias in sperm DNA fragmentation (SDF) testing when performed on semen samples or on those few spermatozoa selected for Intracytoplasmic Sperm Injection (ICSI) treatments.

METHODS

A multimethodological analysis of Single- and Double-Strand DNA Breaks (SSB and DSB, respectively) was performed through the Neutral Comet, the Alkaline Comet, the Sperm Chromatin Dispersion (SCD) and the Terminal deoxynucleotidyl transferase dUTP Nick End Labelling (TUNEL) assays. SDF was evaluated in (i) semen samples from 23 infertile patients (not achieving pregnancy or suffering recurrent miscarriage); (ii) samples after a Swim-up and (iii) spermatozoa microselected for ICSI (ICSI-S).

RESULTS

The analysis of 3217 ICSI-S revealed a significant reduction of SSB values compared to the Ejaculate and the Swim-up samples. On the contrary, DSB values were not reduced after any sperm selection method. The No-pregnancy group presented poorer semen parameters and higher SSB values. The Recurrent miscarriage group presented better semen parameters but also higher DSB values.

CONCLUSION

The analysis of SDF on semen samples may not be fully representative of those few spermatozoa selected for ICSI. Since oxidative stress impairs sperm motility and causes SSB, selecting a motile sperm may intrinsically imply choosing a sperm not affected by this damage. DSB have an enzymatic origin which does not affect motility, making it difficult to select a sperm without this damage. Therefore, ICSI treatments could be effective in patients presenting high SSB values. Patients presenting high DSB values should expect bad ICSI results if this damage is not reduced through other specific methods.

Sperm DNA Fragmentation: A New Guideline for Clinicians

Sperm DNA integrity is crucial for fertilization and development of healthy offspring. The spermatozoon undergoes extensive molecular remodeling of its nucleus during later phases of spermatogenesis, which imparts compaction and protects the genetic content. Testicular (defective maturation and abortive apoptosis) and post-testicular (oxidative stress) mechanisms are implicated in the etiology of sperm DNA fragmentation (SDF), which affects both natural and assisted reproduction. Several clinical and environmental factors are known to negatively impact sperm DNA integrity. An increasing number of reports emphasizes the direct relationship between sperm DNA damage and male infertility. Currently, several assays are available to assess sperm DNA damage, however, routine assessment of SDF in clinical practice is not recommended by professional organizations. This article provides an overview of SDF types, origin and comparative analysis of various SDF assays while primarily focusing on the clinical indications of SDF testing. Importantly, we report four clinical cases where SDF testing had played a significant role in improving fertility outcome. In light of these clinical case reports and recent scientific evidence, this review provides expert recommendations on SDF testing and examines the advantages and drawbacks of the clinical utility of SDF testing using Strength-Weaknesses-Opportunities-Threats (SWOT) analysis.

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.

Magnetic-activated cell sorting of non-apoptotic spermatozoa improves the quality of embryos according to female age: a prospective sibling oocyte study

PURPOSE

The main aim of our study was to evaluate the benefit of the use of non-apoptotic spermatozoa selected by magnetic-activated cell sorting (MACS) for ICSI procedures for couples in which the women had good prognoses and the male factor of infertility was teratozoospermia.

METHODS

Twenty-six couples were treated with ICSI after MACS selection of non-apoptotic spermatozoa following a sibling oocyte approach. Half of the oocytes were microinjected with conventionally prepared spermatozoa, and the other half were microinjected with non-apoptotic, MACS-selected spermatozoa. To assess the influence of MACS selection of spermatozoa on the outcomes of the ICSI cycles, the fertilization, embryo quality, pregnancy, and delivery rates were evaluated and compared between the sibling oocyte groups.

RESULTS

When subpopulations of couples according to female age were analyzed, a significant difference in quality of blastocyst was observed. More precisely, in a group that was treated with MACS-ICSI, a higher percentage of good quality blastocysts was found among women older than 30 years (75.0 vs. 33.3%; P = 0.028), while there was no difference among younger women. If all included couples were compared regardless of age, no significant difference was observed in the outcome of the ICSI/MACS-ICSI cycles in terms of oocytes and embryos. Additionally, after the ICSI and MACS-ICSI procedures, the morphologies of the prepared spermatozoa were compared. Results showed that the overall percentage of morphologically normal spermatozoa did not differ significantly between the ICSI and MACS-ICSI procedures. However, detailed analyses of the morphologically abnormal spermatozoa revealed significantly more spermatozoa with abnormal tails after MACS-ICSI procedure, which may be potential consequence of the selection procedure. Moreover, the trends towards less spermatozoa with abnormal heads and towards more spermatozoa with abnormal necks and midpieces after MACS-ICSI procedure were revealed, although the differences were not significant.

CONCLUSIONS

Couples dealing with male infertility due to teratozoospermia can benefit from MACS selection of spermatozoa with higher percentage of good quality blastocysts but only when the woman is older than 30 years.

Impact of high magnification sperm selection on neonatal outcomes: a retrospective study

PURPOSE

The aim of this study was to compare the effect of the deselection of spermatozoa presenting vacuole-like structures using IMSI (intracytoplasmic morphologically selected sperm injection) with ICSI (intracytoplasmic sperm injection) by means of neonatal outcomes.

METHODS

In a retrospective two-center analysis, a total of 848 successful IMSI or ICSI cycles ending with a live birth, induced abortion, or intrauterine fetal death (IUFD) were included.

RESULTS

The IMSI and ICSI groups included 332 and 655 babies or fetuses, respectively. The parents were older in the IMSI group than in the ICSI group (mothers were 35.1 vs 32.9 years, and fathers were 39.1 vs 36.2 years). The multiple pregnancy rate was higher in the IMSI group. The mean pregnancy duration and mean birth weight were almost identical in both groups. There was no significant difference in major congenital malformations between the two groups. However, this rate was decreased in the IMSI group compared to that in the ICSI group (1.8 vs 3.2%), the difference being mainly found in singletons (1.4 vs 3.3%). Boys were more often affected than girls in both groups. The percentages of chromosomal abnormalities did not differ between the IMSI and ICSI groups (0.6 and 0.8%). The reported congenital malformations mainly affected the heart, urogenital, and musculoskeletal systems.

CONCLUSIONS

In the present study, the malformation rates observed in the IMSI and ICSI groups were not significantly different, even if slightly lower after IMSI. However, the observed difference followed the same trends observed in previous reports, indicating the possible impact of IMSI on decreasing congenital malformation occurrences. This highlights the necessity to prospectively evaluate the impact of IMSI on neonatal outcome after IVF treatment.

Role of sperm DNA fragmentation in male factor infertility: A systematic review

OBJECTIVE

To summarise the latest evidence on the role of sperm DNA fragmentation (SDF) in male factor infertility, as SDF has been emerging as a valuable tool for male infertility evaluation.

METHODS

A search of PubMed was conducted using the keywords 'sperm DNA fragmentation' and 'male infertility'. Studies in languages other than English were excluded. All identified studies were screened and clinical studies in humans were included.

RESULTS

In all, 150 articles were included for analysis. Current evidence supports the association between high SDF and poor reproductive outcomes for natural conception and intrauterine insemination. Although the relationship between high SDF and in vitro fertilisation and intracytoplasmic sperm injection is less clear, the negative implication of high SDF on pregnancy loss is evident. Various treatment strategies have been attempted with varying success. The predictive value of SDF testing on outcomes of natural pregnancy and assisted reproduction illustrates its value in clinical practice.

CONCLUSION

The significant role of SDF in male factor infertility is supported by current evidence. The beneficial role of SDF testing in selection of varicocelectomy candidates, evaluation of patients with unexplained infertility and recurrent pregnancy loss, selection of the most appropriate assisted reproductive technique with highest success rate for infertile couples, and assessment of infertile men with modifiable lifestyle factors or gonadotoxin exposure has been recently proposed.

Can intracytoplasmic Morphologically Selected Spermatozoa Injection be Used as First Choice of Treatment for Severe Male Factor Infertility Patients?

Aim:

This study was carried out to assess the outcome of the intracytoplasmic morphologically selected sperm injection (IMSI) technique compared with the previous failed intracytoplasmic sperm injection (ICSI) attempts in oligoasthenoteratozoospermia (OAT)/severe OAT (SOAT)/teratozoospermia patients.

Setting:

Institution-based, in vitro fertilization center.

Study Design:

It was a nonrandomized prospective study including 57 couples who had previous one or two ICSI failures (failure due to no implantation as embryos were transferred in these cycles and had no pregnancy) due to male factor. There was no case of total fertilization failure. IMSI was carried out in these couples and the results were compared with their previously failed ICSI attempts.

Materials and Methods:

Real-time selection of sperms was done using IMSI as it allows the assessment of fine nuclear morphology and vacuoles in the sperm head at a high magnification (>6000×) with differential interference contrast optics. Therefore, IMSI was applied in couples having OAT, SOAT or teratozoospermia as male factor and the results were compared with their previous failed ICSI attempts. Statistical analysis was carried out using GraphPad Prism.

Results and Conclusion:

Data analysis demonstrated significant difference in the fertilization rate between IMSI and previous ICSI attempts of these patients (30.0% vs. 52.0%; P < 0.05). The embryo quality, implantation and pregnancy rates with IMSI were also significantly higher than those of their previous ICSI cycles (32% vs. 56.4%; 30.2% vs. 68.5%; 0.0% vs. 62.4%; P < 0.05). Our conclusion is that the IMSI procedure improved embryo development and the clinical outcomes in the same infertile couples with male infertility and poor embryo development over their previous ICSI attempts and can be taken up as the treatment of choice in cases of severe male factor infertility.

An investigation of the potential effect of sperm nuclear vacuoles in human spermatozoa on DNA fragmentation using a neutral and alkaline Comet assay

Presence of vacuoles and degree of sperm DNA damage are considered to be the basic factors used for the assessment of sperm fertilization capacity. We aimed to investigate the link between these two parameters. According to our knowledge, this is the first study where the Comet assay was used to assess the degree of DNA fragmentation of sperm categorized by Motile Sperm Organelle Morphology Examination (MSOME) Grades. Semen samples from 10 patients were assessed. Spermatozoa were graded into four MSOME groups according to the Vanderzwalmen's criteria. A total of 3930 motile spermatozoa were selected one-by-one using an inverted microscope and transferred onto two different slides. The degree of DNA fragmentation was analyzed by alkaline and neutral Comet assay. Results of the neutral Comet assay showed that Grade I spermatozoa (absence of vacuoles) presented significantly lower dsDNA fragmentation level (mean: 3.13 ± 1.17%) than Grade II (maximum of two small vacuoles; mean: 10.34 ± 2.65%), Grade III (more than two small vacuoles or at least one large vacuole; mean: 23.88 ± 8.37%), and Grade IV (large vacuoles associated with abnormal head shapes or other abnormalities; mean: 36.94 ± 7.78%; p < 0.05). Results of the alkaline Comet assay showed that Grade I spermatozoa had significantly lower DNA (ssDNA + dsDNA) fragmentation level (mean: 8.33 ± 3.62%) than Grade III (mean: 25.64 ± 9.15%) and Grade IV (mean: 40.10 ± 9.10%, p < 0.05), but not significantly lower than Grade II (mean: 12.73 ± 5.06%; p > 0.05). Probably, the vacuoles may be responsible for double strand DNA breaks rather than single strand DNA breaks (only 2.39% spermatozoa in MSOME Grade II, 1.76% in III, and 3.16% in IV has single strand breaks). The results demonstrate that lower MSOME grading correlates with lower sperm DNA fragmentation. Therefore, the observation of sperm nuclear vacuoles using real-time optical microscopy without precise DNA fragmentation examination is not sufficient for optimal sperm selection for intracytoplasmic sperm injection.

A Strengths-Weaknesses-Opportunities-Threats (SWOT) analysis on the clinical utility of sperm DNA fragmentation testing in specific male infertility scenarios

Background

Sperm DNA fragmentation (SDF) is recognized as a leading cause of male infertility because it can impair the paternal genome through distinct pathophysiological mechanisms. Current evidence supports SDF as a major factor in the pathophysiology of several conditions, including varicocele, unexplained infertility, assisted reproductive technology failure, and environmental lifestyle factors, although the mechanisms involved have not been fully described yet. Measurement of the levels of DNA fragmentation in semen provides valuable information on the integrity of paternal chromatin and may guide therapeutic strategies. A recently published clinical practice guideline (CPG) highlighted how to use the information provided by SDF testing in daily practice, which triggered a series of commentaries by leading infertility experts. These commentaries contained an abundance of information and conflicting views about the clinical utility of SDF testing, which underline the complex nature of SDF.

Methods

A search of papers published in response to the CPG entitled “Clinical utility of sperm DNA fragmentation testing: practice recommendations based on clinical scenarios” was performed within the Translational Andrology and Urology (TAU) website (http://tau.amegroups.com/). The start and end dates for the search were May 2017 and August 2017, respectively. Each commentary meeting our inclusion criteria was rated as “supportive without reservation”, “supportive with reservation”, “not supportive” or “neutral”. We recorded whether articles discussed either SDF characteristics as a laboratory test method or clinical scenarios, or both. Subsequently, we extracted the particulars from each commentary and utilized the ‘Strengths-Weaknesses-Opportunities-Threats’ (SWOT) analysis to understand the perceived advantages and drawbacks of SDF as a specialized sperm function method in clinical practice.

Results

Fifty-eight fertility experts from six continents and twenty-two countries contributed commentaries. Overall, participants (87.9%; n=51) were supportive of the recommendations provided by the CPG on the utility of SDF testing based on clinical scenarios. The majority of participants made explicit remarks about both the clinical scenarios and SDF assays’ characteristics. Among ‘not supportive’ and ‘supportive with reservation’ participants, 75% (n=30/40) and 77.5% (n=31/40) expressed concerns related to technical limitations of SDF testing methods and clinical utility of the test in one or more clinical scenarios discussed in the CPG, respectively. The SWOT analysis revealed that the CPG provides a reasonable evidence-based proposal for integration of SDF testing in the routine daily practice. It also uncovered gaps of knowledge and threats limiting the widespread application of SDF in everyday practice, thus allowing the identification of opportunities to further refine SDF testing and its clinical utility.

Conclusions

The understanding of the role of SDF in male infertility requires an in-depth analysis of the multifactorial pathophysiological processes and the theories involved. The SWOT analysis allowed an objective evaluation of CPG on the clinical utility of SDF testing based on clinical scenarios and its accompanying commentaries written by global experts in all possible angles. Implementation of SDF testing in the clinic may not only increase the outcome of ART but more importantly improve the health of both fathers to be and resulting offspring.

Sperm selection in natural conception: what can we learn from Mother Nature to improve assisted reproduction outcomes?

BACKGROUND

In natural conception only a few sperm cells reach the ampulla or the site of fertilization. This population is a selected group of cells since only motile cells can pass through cervical mucus and gain initial entry into the female reproductive tract. In animals, some studies indicate that the sperm selected by the reproductive tract and recovered from the uterus and the oviducts have higher fertilization rates but this is not a universal finding. Some species show less discrimination in sperm selection and abnormal sperm do arrive at the oviduct. In contrast, assisted reproductive technologies (ART) utilize a more random sperm population. In this review we contrast the journey of the spermatozoon in vivo and in vitro and discuss this in the context of developing new sperm preparation and selection techniques for ART.

METHODS

A review of the literature examining characteristics of the spermatozoa selected in vivo is compared with recent developments in in vitro selection and preparation methods. Contrasts and similarities are presented.

RESULTS AND CONCLUSIONS

New technologies are being developed to aid in the diagnosis, preparation and selection of spermatozoa in ART. To date progress has been frustrating and these methods have provided variable benefits in improving outcomes after ART. It is more likely that examining the mechanisms enforced by nature will provide valuable information in regard to sperm selection and preparation techniques in vitro. Identifying the properties of those spermatozoa which do reach the oviduct will also be important for the development of more effective tests of semen quality. In this review we examine the value of sperm selection to see how much guidance for ART can be gleaned from the natural selection processes in vivo.

The effect of sperm DNA fragmentation on live birth rate after IVF or ICSI: a systematic review and meta-analysis

A systematic review and meta-analysis was conducted to evaluate the relationship between the extent of sperm DNA damage and live birth rate (LBR) per couple and the influence of the method of fertilization on treatment outcome. Searches were conducted on MEDLINE, EMBASE and Cochrane Library. Six studies were eligible for inclusion in the meta-analysis. Overall, LBR increased signficantly in couples with low sperm DNA fragmentation compared with those with high sperm DNA fragmentation (RR 1.17, 95% CI 1.07 to 1.28; P = 0.0005). After IVF and intracytoplasmic sperm injection (ICSI), men with low sperm DNA fragmentation had significantly higher LBR (RR 1.27, 95% CI 1.05 to 1.52; P = 0.01) and (RR 1.11, 95% CI 1.00 to 1.23, P = 0.04), respectively. A sensitivity analysis showed no statistically significant difference in LBR between low and high sperm DNA fragmentation when ICSI treatment was used (RR 1.08, 95% CI 0.39 to 2.96; P = 0.88). High sperm DNA fragmentation in couples undergoing assisted reproduction techniques is associated with lower LBR. Well-designed randomized studies are required to assess the role of ICSI over IVF in the treatment of men with high sperm DNA fragmentation.

Comparison between intracytoplasmic sperm injection and intracytoplasmic morphologically selected sperm injection in oligo-astheno-teratozoospermia patients

Objective

The aim of this study was to evaluate the efficiency of the intracytoplasmic morphologically selected sperm injection (IMSI) technique compared with conventional ICSI and previous ICSI attempts in oligo-astheno-teratozoospermia (OAT) patients.

Methods

The sperms were selected under high magnification (6,600×) and used to induce fertilization in previous ICSI patients by IMSI. These results were compared with previous conventional ICSI cycles in patients with OAT infertility.

Results

These results demonstrated no significant difference in the fertilization rate between IMSI and previous ICSI cycles (67.7% vs. 65.0%). However, the pregnancy and implantation rates with IMSI were significantly higher than those of the ICSI cycles (33.3% vs. 12.5% and 14.6% vs. 5.4%, respectively; p<0.05). The miscarriage rate among pregnant patients (18.2% vs. 37.5%) showed no statistically significant difference between groups.

Conclusion

Compared to conventional ICSI, this study found that IMSI increased the IVF-ET success rates in patients with OAT.

Semen analysis: update on clinical value, current needs and future perspectives

At present, evaluation of male reproductive function consists primarily of routine semen analysis, a collection of conventional microscopic assessments ideally performed following the guidelines set by the World Health Organization. While providing some insight into testicular function, these long-performed tests are limited in the information that they impart; more specifically, they are unable to predict true fertility potential. As a consequence, there is a need for the appraisal and consideration of newer semen parameters that may be more indicative of reproductive success. Although various novel assays have been introduced that broaden the scope of information available to both researcher and clinician, the utility of these tests remains limited due to the lack of standardisation of protocols and the absence of clinically established, dependable reference ranges. As such, it is not surprising that most of these parameters and their associated methods remain recommended for ‘research purposes only’. With the burgeoning ‘omics’ revolution, nanotechnology and the development of new analytical instruments, there is now an opportunity for the identification and measurement of previously unknown features that may prove to be more indicative of each sperm's true functional status and capability. Once optimised, simplified, clinically validated and made more readily accessible, these new approaches hold the promise of forming the fulcrum upon which andrological investigations can enter a new era.

Intracytoplasmic morphologically selected sperm injection (IMSI): a critical and evidence-based review

Introduced in 2001, intracytoplasmic morphologically selected sperm injection (IMSI) represents a more sophisticated way of ICSI whereby, prior to injection, the spermatozoon is selected at higher magnification. Doing so, the spermatozoon can be evaluated for fine integrity of its nucleus and the injection of a normal spermatozoon with a vacuole-free head can be assured.

Additional research is needed to unravel the underlying mechanisms responsible for the presence of vacuoles in sperm heads. Associations with acrosome status, chromatin condensation, DNA fragmentation and sperm aneuploidy have been documented, however, controversy on their nature exists. Spermatozoon shape and large vacuoles are detected and deselected in conventional ICSI as well. However, the detection of subtle small vacuoles depends on the resolving power of the optical system and may impact oocyte fertilization, embryo development and implantation.

Several comparative studies have indicated that the use of high-magnification sperm selection was associated with both higher pregnancy and delivery rates, whereas also lower miscarriage rates were observed. However, still to date randomized, well-powered studies to confirm these findings are scarce and show conflicting results. Hence, the most relevant indications for IMSI still remain to be determined. Two groups of patients have been put forward i.e. severe male-factor infertility patients and patients with a history of repeated ICSI failures. However, for both groups limited to no proof of any benefit does exist.

IMSI is a time-consuming procedure at the expense of oocyte ageing. The lack of proof and understanding of its benefit does not justify its routine clinical application at present.

High-magnification selection of spermatozoa prior to oocyte injection: confirmed and potential indications

Intracytoplasmic morphologically selected sperm injection (IMSI) involves the use of differential interference contrast microscopy at high magnification (at least ·6300) to improve the observation of live human spermatozoa (particularly by showing sperm head vacuoles that are not necessarily seen at lower magnifications) prior to intracytoplasmic sperm injection (ICSI) into the oocyte. However, a decade after IMSI’s introduction, the technique’s indications and ability to increase pregnancy and/or birth rates (relative to conventional ICSI) are subject to debate. In an attempt to clarify this debate, this work performed a systematic literature review according to the PRISMA guidelines. The PubMed database was searched from 2001 onwards with the terms ‘IMSI’, ‘MSOME’ and ‘high-magnification, sperm’. Out of 168 search results, 22 relevant studies reporting IMSI outcomes in terms of blastocyst, pregnancy, delivery and/or birth rates were selected and reviewed. The studies’ methodologies and results are described and discussed herein. In view of the scarcity of head-to-head IMSI versus ICSI studies, the only confirmed indication for IMSI is recurrent implantation failure following ICSI. All other potential indications of IMSI require further investigation.

The nature of human sperm head vacuoles: a systematic literature review

Motile sperm organelle morphology examination (MSOME) involves the use of differential interference contrast microscopy (also called Nomarski contrast) at high magnification (at least 6300x) to improve the observation of live human spermatozoa. In fact, this technique evidences sperm head vacuoles that are not necessarily seen at lower magnifications - particularly if the vacuoles are small (i.e. occupying <4% of the sperm head’s area). However, a decade after MSOME's introduction, it is still not clear whether sperm head vacuoles are nuclear, acrosomal and/or membrane-related in nature. In an attempt to clarify this debate, we performed a systematic literature review in accordance with the PRISMA guidelines. The PubMed database was searched from 2001 onwards with the terms "MSOME", “human sperm vacuoles”, "high-magnification, sperm”. Out of 180 search results, 21 relevant English-language publications on the nature of human sperm head vacuoles were finally selected and reviewed. Our review of the literature prompted us to conclude that sperm-head vacuoles are nuclear in nature and are related to chromatin condensation failure and (in some cases) sperm DNA damage.

Focus on intracytoplasmic morphologically selected sperm injection (IMSI): a mini-review

Intracytoplasmic sperm injection (ICSI) is the recommended treatment in many cases of male-factor infertility. Several studies have demonstrated a positive correlation between optimal sperm morphology and positive ICSI outcomes. In fact, spermatozoa with severe abnormalities of the head are well documented to be associated with low fertilisation, implantation and pregnancy rates. However, a spermatozoon which is classified as 'normal' by microscopic observation at low magnification could contain ultrastructural defects that impair both the fertilisation process and embryonic development. The intracytoplasmic morphologically selected sperm injection (IMSI) procedure changed the perception of how a spermatozoon suitable for injection should appear. Sperm selection is carried out at ×6000 magnification, allowing improved assessment of the sperm nucleus. Currently, standardized clinical indications for IMSI are lacking and the candidates are selected on the grounds of their medical history or of a careful analysis of the sperm suspension. Further prospective randomized studies are needed to confirm the advantages of IMSI in specific groups of patients. In addition to providing a brief overview of the IMSI procedure, this study aims to review the literature, which explains the theoretical basis and the clinical outcomes of this technique. Several reports show that IMSI is associated with improved implantation and clinical pregnancy rates as well as lower abortion rates when compared to ICSI. Although a possible correlation between the sperm's abnormal nucleus shape, increased DNA fragmentation and negative laboratory and clinical outcomes has been long investigated, the results are conflicting.

Motile sperm organelle morphology examination (MSOME) and sperm head vacuoles: state of the art in 2013

BACKGROUND Approximately 10 years after the first publication introducing the motile sperm organelle morphology examination (MSOME), many questions remained about sperm vacuoles: frequency, size, localization, mode of occurrence, biological significance and impact on male fertility potential. Many studies have tried to characterize sperm vacuoles, to determine the sperm abnormalities possibly associated with vacuoles, to test the diagnostic value of MSOME for male infertility or to question the benefits of intracytoplasmic morphologically selected sperm injection (IMSI). METHODS We searched PubMed for articles in the English language published in 2001-2012 regarding human sperm head vacuoles, MSOME and IMSI. RESULTS A bibliographic analysis revealed consensus for the following findings: (i) sperm vacuoles appeared frequently, often multiple and preferentially anterior; (ii) sperm vacuoles and sperm chromatin immaturity have been associated, particularly in the case of large vacuoles; (iii) teratozoospermia was a preferred indication of MSOME and IMSI. CONCLUSION The high-magnification system appears to be a powerful method to improve our understanding of human spermatozoa. However, its clinical use remains unclear in the fields of male infertility diagnosis and assisted reproduction techniques (ARTs).

Twelve years of MSOME and IMSI: a review

A promising method for observing spermatozoa, motile sperm organelle morphology examination (MSOME) enables the evaluation of the nuclear morphology of motile spermatozoa in real time at high magnification and has allowed the introduction of a modified microinjection procedure, intracytoplasmic morphologically selected sperm injection (IMSI). Since its development, several studies have intensively investigated the efficacy of MSOME and IMSI. The objective of the present study is to review the current literature on the MSOME and IMSI techniques. A promising method for observing spermatozoa, motile sperm organelle morphology examination (MSOME), enables the evaluation of the nuclear morphology of motile spermatozoa in real time at high magnification and has allowed the introduction of a modified microinjection procedure, intracytoplasmic morphologically selected sperm injection (IMSI). Since its development, several studies have intensively investigated the efficacy of MSOME and IMSI. The objective of the present study is to review the current literature on the MSOME and IMSI techniques.

High prevalence of isolated sperm DNA damage in infertile men with advanced paternal age

BACKGROUND

Sperm DNA damage is associated with male infertility, lower pregnancy rates and pregnancy loss.

OBJECTIVE

The primary aim of our study was to evaluate the prevalence of sperm DNA damage in younger and older men with normozoospermia.

DESIGN, SETTING AND PARTICIPANTS

We obtained semen from 277 consecutive non-azoospermic men presenting for sperm DNA testing.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The main outcome measures included sperm % DNA fragmentation index (%DFI, using sperm chromatin structure assay), sperm concentration, motility and morphology, and, paternal age.

RESULTS AND LIMITATIONS

Sperm % DFI was positively correlated with paternal age (r = 0.20, P < 0.001) and inversely correlated % progressive motility (r = -0.16, P = 0.01). Sperm %DFI was significantly higher in older (≥40 years) compared to younger (<40 years) normozoospermic men (17 ± 13 vs. 12 ± 8, respectively P = 0.008), whereas, sperm concentration, progressive motility and morphology were not significantly different in these two groups. Moreover, the prevalence of high levels of sperm DNA damage (>30 % DFI) was significantly higher in older compared to younger normozoospermic men (17 % vs. 3 %, respectively, P < 0.001).

CONCLUSION

The data indicate that a conventional semen analysis can often fail to detect a defect in spermatogenesis (high %DFI) in older men and suggest that infertile couples with advanced paternal age, including those with normal semen parameters, should consider sperm DNA testing as part of the couple evaluation.

The combination matters--distinct impact of lifestyle factors on sperm quality: a study on semen analysis of 1683 patients according to MSOME criteria

BACKGROUND

Poor sperm quality can negatively affect embryonic development and IVF outcome. This study is aimed at investigating the influence of various lifestyle factors on semen quality according to MSOME (motile sperm organelle morphology examination) criteria.

METHODS

1683 male patients undergoing assisted reproductive technologies (ART) in our clinic were surveyed about their age, BMI (body mass index), ejaculation frequency, nutrition, sports, sleeping habits and social behavior. Semen samples were collected and evaluation of semen parameters according to MSOME and WHO criteria was performed. Results were grouped and statistically analyzed.

RESULTS

Although single parameters had minor effects on sperm parameter, the combination of age, BMI, coffee intake, ejaculatory frequency and duration of sexual abstinence were identified as factors having a negative effect on sperm motility. Additionally, we could demonstrate that MSOME quality was reduced. The negative impact of age, BMI and coffee intake on sperm quality could be compensated if patients had a high ejaculation frequency and shorter periods of sexual abstinence.

CONCLUSIONS

Combinations of adverse lifestyle factors could have a detrimental impact on sperm, not only in terms of motility and sperm count but also in terms of sperm head vacuolization. This negative impact was shown to be compensated by higher ejaculation frequency and a shorter period of sexual abstinence. The compensation is most likely due to a shorter storage time in the male gonads, thus reducing the duration of sperms' exposure to reactive oxygen species (ROS).