Sperm DNA fragmentation: mechanisms of origin, impact on reproductive outcome, and analysis

Paternal factors contributing to embryo quality

PURPOSE

Advancing maternal and paternal age leads to a decrease in fertility, and hence, many infertile couples opt for assisted reproductive technologies [ART] to achieve biological parenthood. One of the key determinants of achieving a live outcome of ART, embryo quality, depends on both the quality of the oocyte and sperm that have created the embryo. Several studies have explored the effect of oocyte parameters on embryo quality, but the effects of sperm quality on the embryo have not been comprehensively evaluated.

METHOD

In this review, we assess the effect of various genetic factors of paternal origin on the quality and development of the embryo.

RESULTS

The effects of sperm aneuploidy, sperm chromatin structure, deoxyribonucleic acid [DNA] fragmentation, role of protamines and histones, sperm epigenetic profile, and Y chromosome microdeletions were explored and found to negatively affect embryo quality.

CONCLUSION

We propose that careful assessment of spermatozoal parameters is essential to achieve embryo development and a healthy live birth. However, the heterogeneity in test results and the different approaches of assessing a single sperm parameter highlight the need for more research and the development of standardized protocols to assess the role of sperm factors affecting embryo quality.

Paternal factors and embryonic development: Role in recurrent pregnancy loss

The events occurring at the maternal-foetal interface define a successful pregnancy but the current paradigm has shifted towards assessing the contribution of spermatozoa for embryogenesis. Spermatozoa with defective DNA integrity may fertilise the oocyte but affect subsequent embryonic development. The present case-control study was conducted in male partners of couples experiencing recurrent pregnancy loss (RPL) to assess the gene expression of spermatozoal FOXG1, SOX3, OGG1, PARP1, RPS6, RBM9, RPS17 and RPL29. This was correlated with reactive oxygen species (ROS) levels and DNA Fragmentation Index (DFI). Semen samples were obtained from 60 cases and 30 fertile controls. Gene expression was done by qPCR analysis, and relative quantification was calculated by the 2^-ΔΔCt method. Chemiluminescence and the sperm chromatin structure assay were used to measure the ROS and DFI levels respectively. FOXG1, OGG1, RPS6 and RBM9 were seen to be upregulated, while SOX3 and PARP1 were downregulated. Relative expression of SOX3, OGG1, RPS6 and RPS17 showed a significant difference between patients and controls (p < 0.05). RPL patients were seen to have high ROS (>27.8; p = 0.001) and DFI (>30.7; p < 0.0001) with respect to controls. Sperm transcript dysregulation and oxidative DNA damage can be "carried over" after implantation, thus affecting embryogenesis and health of the future progeny.

Risk of chromosomal aberration in spermatozoa during intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) has become critical for the treatment of severe male infertility. The principal feature of ICSI is the direct injection of spermatozoon into an oocyte, which facilitates the production of fertilized embryos regardless of semen characteristics, such as sperm concentration and motility. However, the chromosomal integrity of ICSI zygotes is degraded compared to that of zygotes obtained via in vitro fertilization. This chromosomal damage may occur due to the injection of non-capacitated, acrosome-intact spermatozoa, which never enter the oocytes under natural fertilization. Furthermore, it is possible that the in vitro incubation and pre-treatment of spermatozoa during ICSI results in DNA damage. Chromosomal aberrations in embryos induce early pregnancy losses. However, these issues may be overcome by embryo production using gametes with guaranteed chromosomal integrity. Because conventional chromosome analysis requires fixing cells to obtain the chromosome spreads, embryos cannot be produced using the nucleus that has been analyzed. On the other hand, genome cloning using androgenic or gynogenic embryos provides an additional nucleus for chromosome analysis following embryo production. Thus, this review aims to highlight the hazardous nature of chromosomal aberrations in sperm during ICSI and to introduce a method for the prezygotic examination for chromosomal aberrations.

Is sperm DNA fragmentation a useful test that identifies a treatable cause of male infertility?

The present-day laboratory methods of sperm analysis are a poor predictor of reproductive outcome, and for many years it has been clear that newer and better tests are required. Although many such tests have been proposed, only those which determine sperm DNA quality are still being considered. Of these, several tests of sperm DNA fragmentation are available, although there is presently no consensus about the most appropriate test, the best test specimen (fresh or washed sperm) or what level of fragmentation is of clinical concern. Moreover, although several strategies have been proposed to reduce DNA fragmentation, there is no universal approach and few randomised trials have tested these in a clinical context. As such, most professional bodies do not presently support the use of sperm DNA fragmentation tests, and it is clear that large randomised trials are still required to further evaluate their clinical effectiveness.

What should be done for men with sperm DNA fragmentation?

In an age when a small quantity of sperm can lead to pregnancy through in vitro fertilization or intracytoplasmic sperm injection, selecting healthy sperm is important. Sperm DNA fragmentation (SDF) is known to be higher in infertile men. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) and the alkaline comet test are SDF tests that directly measure DNA damage and have shown closer correlations with assisted reproduction results than indirect tools such as the sperm chromatin structure assay or the sperm chromatic dispersion test. It is difficult; however, to endorse a single test as the best test overall; instead, it is best to select a testing method based on each patient's clinical condition and goals. In a couple struggling with infertility, if the male partner has a high level of SDF, he should aim to decrease SDF through lifestyle modifications, antioxidant treatment, and ensuring an appropriate duration of abstinence, and physicians need to treat the underlying diseases of such patients. If sperm DNA damage continues despite the patient's and physician's efforts, other methods, such as micromanipulation-based sperm selection or testicular sperm extraction, should be used to select healthy sperm with nuclear DNA integrity.

Integration of sperm DNA damage assessment into OECD test guidelines for genotoxicity testing using the MutaMouse model

The Organisation for Economic Co-operation and Development (OECD) endorses test guidelines (TG) for identifying chemicals that are genotoxic, such as the transgenic rodent gene mutation assay (TG 488). Current OECD TG do not include assays for sperm DNA damage resulting in a critical testing gap. We evaluated the performance of the Sperm Chromatin Structure Assay (SCSA) and the Terminal Deoxynucleotidyl Transferase-Mediated Deoxyuridine Triphosphate Nick end Labeling (TUNEL) assay to detect sperm DNA damage within the recommended TG 488 protocol. MutaMouse males received 0, 0.5, 1, or 2 mg/kg/day triethylenemelamine (TEM), a multifunctional alkylating agent, for 28 days orally and tissues were collected two (blood) and three (sperm and bone marrow) days later. TEM significantly increased the frequency of lacZ mutants in bone marrow, and of micronuclei (MN) in both reticulocytes (%MN-RET) and normochromatic erythrocytes (%MN-NCE) in a dose-dependent manner (P < 0.05). The percentage of DNA fragmentation index (%DFI) and %TUNEL positive cells demonstrated dose-related increases in sperm (P < 0.05), and the two assay results were strongly correlated (R = 0.9298). Within the same animal, a good correlation was observed between %MN-NCE and %DFI (R = 0.7189). Finally, benchmark dose modelling (BMD) showed comparable BMD₁₀ values among the somatic and germ cell assays. Our results suggest that sperm DNA damage assays can be easily integrated into standard OECD designs investigating genotoxicity in somatic tissues to provide key information on whether a chemical is genotoxic in germ cells and impact its risk assessment.

The male contribution to recurrent pregnancy loss

There are several known causes of recurrent pregnancy loss (RPL) in a couple, which include endocrine abnormalities, immunologic abnormalities, structural uterine abnormalities and karyotype abnormalities. The evaluation largely focuses on the female. The male contribution to RPL remains understudied. With the exception of the karyotype analysis, there is currently no other recommended testing for the male partner of a woman who has suffered multiple pregnancy losses. Chromosomal abnormalities are well defined causes of pregnancy losses in the literature. However, despite the fact that abnormal DNA fragmentation has been implicated in the pathogenesis of unexplained RPL, it is not routinely checked during the evaluation of RPL. This is likely due to the fact that abnormal DNA fragmentation is the end result of multiple different mechanisms including environmental exposures, varicoceles, gene alteration and epigenetic changes resulting in an inherent susceptibility to DNA damage? We are just beginning to scratch the surface of our understanding of the male contribution to RPL and more studies especially focusing on epigenetic modifications and gene alterations are needed.

Effects of microsurgical varicocelectomy on semen analysis and sperm function tests in patients with different grades of varicocele: Role of sperm functional tests in evaluation of treatments outcome

It seems that varicocele play a role in male infertility, as such, their prevalence increases from 15% in the normal population to 80% in secondary infertility subjects. Varicoceles may have negative effects on semen quality. Our goal was to assess the effects of microsurgical varicocelectomy on semen analysis and sperm functional tests in men with different grades of varicoceles. Thirty infertile men with different grades of varicoceles (grades 1 to 3) were enrolled in our study. Semen quality was assessed by semen analysis according to the WHO guideline (WHO, 1999) and four different sperm functional tests (aniline blue, toluidine blue, chromomycin A3 and TUNEL test) were carried out before and 3 months after microsurgical varicocelectomy (M-varicocelectomy). When considered all three grades together, we showed that M-varicocelectomy had statistically significant effects on all four types of sperm functional tests (p value<0.05). It also had positive effects on conventional semen parameters, although the effects were not statistically significant for some parameters (for example sperm count). When analysed separately (based on varicocele grades) the surgery, although caused improvements in semen quality, but may have more statistically significant effects on patients with varicocele of higher grade. In addition, in varicocele of lower grade (for example grade 2), sperm function test may be a better predictor of surgical success than the conventional semen analysis. Thus, we show that not only M-varicocelectomy has significant positive effect on semen quality but also if sperm functional tests become more affordable in the future, because they yield more precise results, their use in daily practice may increase significantly in patients with varicoceles.

Impact of a gestational exposure to diesel exhaust on offspring gonadal development: experimental study in the rabbit

The aim of the present work was to address experimentally the possible impact of exposure to air pollution during gestation on the differentiation and function of the gonads of the offspring using a rabbit model. Rabbits were exposed daily to diluted diesel exhaust gas or filtered air from the 3rd until the 27th day of gestation, during which time germ cells migrate in genital ridges and divide, and fetal sex is determined. Offspring gonads were collected shortly before birth (28th day of gestation) or after puberty (7.5 months after birth). The structure of the gonads was analyzed by histological and immunohistological methods. Serum concentrations of testosterone and anti-Müllerian hormone were determined using ELISA. The morphology and the endocrine function of the gonads collected just at the arrest of the exposure were similar in polluted and control animals in both sexes. No differences were observed as well in gonads collected after puberty. Sperm was collected at the head of the epididymis in adults. Sperm motility and DNA fragmentation were measured. Among all parameters analyzed, only the sperm DNA fragmentation rate was increased three-fold in exposed males. Mechanisms responsible for these modifications and their physiological consequences are to be further clarified.

Associations between sperm quality, DNA damage, and CYP1A1, GSTT1 and GSTM1 polymorphisms with 1-hydroxypyrene urinary levels in men occupationally exposed to polycyclic aromatic hydrocarbons

PURPOSE

During recent decades, several reports have suggested a decrease in semen quality and DNA damage due in part to environmental toxicants and industrial chemicals. Among these xenobiotics, polycyclic aromatic hydrocarbons (PAHs) are of particular concern because of their remarkable mutagenic and carcinogenic properties and because several experimental and epidemiological studies have reported adverse effects of PAHs on male reproductive health and DNA structure. The aim of the study was to evaluate the association between 1-hydroxypyrene (1-OHP) urinary levels and sperm quality, DNA damage and the frequency of CYP1A1, GSTT1, and GSTM1 polymorphisms.

METHODS

Semen, urine and blood samples were taken for sperm-quality assessment, 1-OHP urinary level measurement, DNA damage evaluation and polymorphism frequency analysis of three genes implicated in PAH metabolism in a total of 70 Mexican subjects exposed and nonexposed to PAHs.

RESULTS

A significant decrease in sperm quality and increased DNA damage were registered in occupationally exposed volunteers. Polymorphisms modified the 1-OHP urinary levels; however, no associations were found between them. Inverse associations were registered between the sperm concentration/mL and 1-OHP levels and between tail lengths and the GSMT1 null genotype.

CONCLUSIONS

Our data showed an inverse association between 1-OHP urinary levels and both sperm quality and the DNA integrity. Additionally, the heterozygote variants of CYP1A1-m1 and CYP1A1-m2 significantly increased the urinary excretion of 1-OHP, and the GSTM1 null variant was inversely associated with the comet parameters evaluated.

Azoospermia and embryo morphokinetics: testicular sperm-derived embryos exhibit delays in early cell cycle events and increased arrest prior to compaction

Purpose

Sperm play an essential role in embryonic genome activation and embryonic progression to blastocyst. In the present work, we focus on development of embryos created as a result of ICSI with testicular or epididymal sperm from azoospermic males and compare this to outcomes from normospermic males. The objective of this study was to determine if sperm origin influences clinical outcomes, the kinetics of embryo development, or the incidence of cleavage anomalies and multinucleation.

Methods

A total of 93 consecutive intracytoplasmic sperm injection cycles (ICSI) performed for 83 couples were included in this study. Observations were made on 594 fertilized oocytes cultured in the EmbryoScope using time-lapse microscopy (TLM). Epididymal sperm (n = 29) cycles or surgically retrieved sperm from the testis (TESE; n = 37 cycles) of men with either obstructive (OA) or non-obstructive azoospermia (NOA) were used to inject oocytes. A further 27 ICSI cycles were performed using ejaculated sperm from normospermic males, designated as our control sperm (CS) group. Kinetic data and cycle outcomes were retrospectively analyzed.

Results

The clinical pregnancy rate was not different between the three groups (TESE 51.4%, PESA 57.7%, and CS 59.3%). A non-significant decrease was observed in both implantation (30.9%) and live birth rate (43%) with TESE as compared to PESA (35.3%, 58%, respectively) and CS groups (45.1%, 56%, respectively). Failure to compact was significantly higher amongst TESE-NOA embryos (35.2%; P < 0.001) as compared to TESE-OA (4%), PESA (9%), and CS (3.8%) embryos. The two points at which TESE-derived embryos (both NOA and OA) behaved most differently from PESA and CS embryos was at cc2 (t3-t2; time to initiation of the second cell cycle) and tSB (time to start of blastulation). A significantly lower percentage of TESE embryos exhibited kinetics typically ascribed to high quality embryos with the greatest developmental potential. Finally, the incidence of direct uneven cleavage (DUC) was observed to be significantly higher after ICSI with sperm retrieved from azoospermic males.

Conclusions

TLM allowed a more in depth comparison of paternal influence on embryo morphokinetics and helped to identify specific differences in cell cycle kinetics. TESE-NOA embryos exhibited a higher incidence of compaction failure.

Effect of Heat Stress on Sperm DNA: Protamine Assessment in Ram Spermatozoa and Testicle

Sperm DNA fragmentation is considered one of the main causes of male infertility. The most accepted causes of sperm DNA damage are deleterious actions of reactive oxygen species (ROS), defects in protamination, and apoptosis. Ram sperm are highly prone to those damages due to the high susceptibility to ROS and to oxidative stress caused by heat stress. We aimed to evaluate the effects of heat stress on the chromatin of ejaculated and epididymal sperm and the activation of apoptotic pathways in different cell types in ram testis. We observed higher percentages of ejaculated sperm with increased chromatin fragmentation in the heat stress group; a fact that was unexpectedly not observed in epididymal sperm. Heat stress group presented a higher percentage of spermatozoa with DNA fragmentation and increased number of mRNA copies of transitional protein 1. Epididymal sperm presented greater gene expression of protamine 1 on the 30th day of the spermatic cycle; however, no differences in protamine protein levels were observed in ejaculated sperm and testis. Localization of proapoptotic protein BAX or BCL2 in testis was not different. In conclusion, testicular heat stress increases ram sperm DNA fragmentation without changes in protamination and apoptotic patterns.

The effect of swim-up and gradient sperm preparation techniques on deoxyribonucleic acid (DNA) fragmentation in subfertile patients

PURPOSE

To compare the effect of two different sperm preparation techniques, including swim-up and gradient methods on sperm deoxyribonucleic acid (DNA) fragmentation status of semen samples from unexplained and mild male factor subfertile patients undergoing intrauterine insemination (IUI).

DESIGN

A prospective randomized study was conducted in 65 subfertile patients, including 34 unexplained and 31 male factor infertility to compare basal and post-procedure DNA fragmentation rates in swim-up and gradient techniques. Sperm DNA fragmentation rates were evaluated by a sperm chromatin dispersion (SCD) test in two portions of each sample of semen that was prepared with either swim-up or gradient techniques. Sperm motility and morphology were also assessed based on WHO 2010 criteria.

RESULTS

Swim-up but not gradient method yielded a statistically significant reduction in the DNA fragmented sperm rate after preparation as compared to basal rates, in the semen samples of both unexplained (41.85 ± 22.04 vs. 28.58 ± 21.93, p < 0.001 for swim-up; and 41.85 ± 22.04 vs. 38.79 ± 22.30, p = 0.160 for gradient) and mild male factor (46.61 ± 19.38 vs. 30.32 ± 18.20, p < 0.001 for swim-up and 46.61 ± 19.38 vs. 44.03 ± 20.87, p = 0.470 for gradient) subgroups.

CONCLUSIONS

Swim-up method significantly reduces sperm DNA fragmentation rates and may have some prognostic value on intrauterine insemination in patients with decreased sperm DNA integrity.

Sperm DNA fragmentation: An early and reliable marker of air pollution

Environmental factors could have a key role in the continuous and remarkable decline of sperm quality observed in the last decades. This study compared the seminal parameters and sperm DFI in men living in areas with different levels of air pollution. Results demonstrate that both steel plants workers and patients living in a high polluted area show a mean percentage of sperm DNA fragmentation above 30%, highlighting a clear sperm damage. In this work, two different techniques were used to measure sperm DNA damage in patients' groups, finding in both cases a high sperm DFI in patients living in polluted areas. We candidate sperm DNA fragmentation as a valuable early marker of the presence and harmful effects of pollution. We suggest that sperm DNA evaluation could be both an indicator of individual health and reproductive capacity, and a suitable datum to connect the surrounding environment with its effects.

Sperm DNA fragmentation index does not correlate with blastocyst euploidy rate in egg donor cycles

Sperm DNA fragmentation is a known etiology for male infertility. We evaluated the impact of sperm DNA fragmentation index (DFI) on blastocyst euploidy in IVF cycles with egg donors. This observational retrospective study, which was conducted in a university affiliated fertility clinic, included IVF-ICSI-pre-implantation Genetic Screening (PGS) egg donor cycles in which DFI was tested prior to IVF, between January 1st, 2014 and July 31st, 2016. Twenty-seven cycles with DFI > 15% were included in the study group and compared with 18 cycles of DFI < 15% within control group. Research group participants had significantly lower sperm count and motility (55.4*10⁶/ml and 37.4%, respectively) compared with controls (92.5*10⁶/ml and 55.7%, respectively, p < .05). The groups were similar in terms of donors' demography (age, BMI), ovarian reserve (AMH, AFC) and response to hormonal stimulation (E2 level on triggering day and number of retrieved eggs). Embryo development (from 2PN through day 3 embryos to blastocysts) was similar as well. The number of biopsied blastocysts from study and control groups was 171 and 87, respectively. PGS with array comprehensive genomic hybridization revealed comparable euploidy rates of 69.3% and 67.3%, respectively (p > .05). DFI did not have an impact on the blastocyst euploidy rate in IVF cycles with egg donors.

Transmission electron microscopy analysis of the origin and incidence of sperm intranuclear cytoplasmic retention in fertile and teratozoospermia men

The human sperm nucleus contains cytoplasm. However, the origin and incidence of human sperm intranuclear cytoplasmic retention (INCR) remain unknown. The objectives of this study were to observe the morphological origin of INCR within the seminiferous epithelium and investigate the incidence of INCR in fertile and teratozoospermia men using transmission electron microscopy (TEM). By TEM, INCR initially appeared in elongating round spermatid nuclei and varied in size, number, shape, content, location and distribution within sperm nuclei. The teratozoospermia group (n = 16) demonstrated a higher incidence of INCR than did the fertile group (n = 16) (17.6 ± 5.2% vs. 9.7 ± 3.4%; p = 0.000). In the fertile group, no correlations were found between the incidence of INCR and abnormal sperm morphology, nuclear vacuole, acrosome integrity, motility or concentration (p > 0.05). However, the incidence of INCR exhibited a positive relationship with sperm abnormal morphology in the teratozoospermia group (r = 0.616, p = 0.011). These results demonstrate that INCR occurs in the early process of spermatogenesis and is an alteration found in the nucleus. Spermatozoa from teratozoospermia men contained more INCRs than those from fertile males. More attention should be paid to the possibility of spermatozoa containing INCR when using spermatozoa with abnormal head morphology for clinical or diagnostic purposes.

Antioxidant activity of CAPE (caffeic acid phenethyl ester) in vitro can protect human sperm deoxyribonucleic acid from oxidative damage

PURPOSE

Sperm processing (e.g., centrifugation) used in preparation for assisted reproduction can result in excessive generation of reactive oxygen species (ROS) and potential sperm damage. The use of antioxidants during sperm processing has been shown to prevent iatrogenic sperm damage, including DNA damage. In this study, we evaluated the effect of caffeic acid phenethyl ester (CAPE) on oxidative stress mediated sperm dysfunction and DNA damage.

METHODS

Semen samples were obtained to liquefy at room temperature. After centrifugation and washing protocols, spermatozoa were incubated in a single step supplemented medium with either of 10, 50 or 100 μmol/L CAPE for 2 hours at 36 °C. After incubation period, MDA levels of seminal plasma were measured. The fragmentation in sperm DNA was detected by light microscopy via use of an aniline blue assay, while ultrastructural morphology was analyzed by transmission electron microscopy.

RESULTS

Significant increase has been observed in percent chromatin condensation (assessed by aniline blue staining) and Malondialdehyde (Mmol/L) in oligoasthenoteratozoospermia group before the centrifugation (0.57 ± 0.15). Incubation of samples with 100 μmol/L CAPE after centrifugation resulted in a significantly lower percent chromatin condensation compared to samples incubated without CAPE (0.42 ± 0.12) (P < 0.0033). Incubation of all samples with CAPE (10 μmol/L, 50 μmol/L, 100 μmol/L.) after centrifugation resulted in a significantly lower percentage of Malondialdehyde levels.

CONCLUSIONS

The data suggests that preincubation of spermatozoa with the antioxidant CAPE offers protection against oxidative DNA damage in vitro.

A systematic review on sperm DNA fragmentation in male factor infertility: Laboratory assessment

Objective

To review sperm DNA fragmentation (SDF) testing as an important sperm function test in addition to conventional semen analysis. High SDF is negatively associated with semen quality, the fertilisation process, embryo quality, and pregnancy outcome. Over recent decades, different SDF assays have been developed and reviewed extensively to assess their applicability and accuracy as advanced sperm function tests. Amongst them, the standardisation of the terminal deoxynucleotidyl transferased UTP nick-end labelling (TUNEL) assay with a bench top flow cytometer in clinical practice deserves special mention with a threshold value of 16.8% to differentiate infertile men with DNA damage from fertile men.

Materials and methods

A systematic literature search was performed through the PubMed, Medline, and ScienceDirect databases using the keywords ‘sperm DNA fragmentation’ and ‘laboratory assessment’. Non-English articles were excluded and studies related to humans were only included.

Results

Of the 618 identified, 87 studies (original research and reviews) and in addition eight book chapters meeting the selection criteria were included in this review. In all, 366 articles were rejected in the preliminary screening and a further 165 articles related to non-human subjects were excluded.

Conclusion

There are pros and cons to all the available SDF assays. TUNEL is a reliable technique with greater accuracy and as an additional diagnostic test in Andrology laboratories along with basic semen analysis can predict fertility outcome, and thus direct the choice of an assisted reproductive technology procedure for infertile couples. Also, the TUNEL assay can be used as a prognostic test and results are beneficial in deciding personalised treatment for infertile men.

Fatherhood and Sperm DNA Damage in Testicular Cancer Patients

Testicular cancer (TC) is one of the most treatable of all malignancies and the management of the quality of life of these patients is increasingly important, especially with regard to their sexuality and fertility. Survivors must overcome anxiety and fears about reduced fertility and possible pregnancy-related risks as well as health effects in offspring. There is thus a growing awareness of the need for reproductive counseling of cancer survivors. Studies found a high level of sperm DNA damage in TC patients in comparison with healthy, fertile controls, but no significant difference between these patients and infertile patients. Sperm DNA alterations due to cancer treatment persist from 2 to 5 years after the end of the treatment and may be influenced by both the type of therapy and the stage of the disease. Population studies reported a slightly reduced overall fertility of TC survivors and a more frequent use of ART than the general population, with a success rate of around 50%. Paternity after a diagnosis of cancer is an important issue and reproductive potential is becoming a major quality of life factor. Sperm chromatin instability associated with genome instability is the most important reproductive side effect related to the malignancy or its treatment. Studies investigating the magnitude of this damage could have a considerable translational importance in the management of cancer patients, as they could identify the time needed for the germ cell line to repair nuclear damage and thus produce gametes with a reduced risk for the offspring.

Practical implications of mineral and vitamin imbalance in grazing sheep

Rapid progress in research on mineral functions in biological systems over the past 20 years has provided new and unexplored implications for health and production in grazing livestock. The strong interaction among calcium (Ca), magnesium (Mg), phosphorus (P), sodium (Na), potassium (K) and vitamin D influences the absorption, utilisation and status of these nutrients, particularly Ca and Mg. An imbalanced intake of Ca, Mg, P, Na, K and vitamin D is common in ruminants grazing pastures and vegetative crops. The interaction may modify susceptibility to clinical hypocalcaemia, hypomagnesaemia and pregnancy toxaemia, or to subclinical and chronic deficiencies of Ca, Mg and Na. However, hypocalcaemia is also associated with endocrine failure. Whether this failure is susceptible to nutritional modulation or even whether supplements of Ca, Mg, Na and vitamin D reduce or exacerbate the risk of metabolic disease in sheep is unclear. Selenium, manganese, zinc, copper, sulfur, vitamin E and vitamin A play synergistic roles in the antioxidant defence mechanism and modulate the consequences of oxidative stress. In extensive grazing systems combined low intakes of these antioxidants are not unusual, particularly in seasonally dry environments and at a time coinciding with the increased oxidative stress that naturally occurs through the reproductive cycle. This oxidative stress is accentuated by heat stress and parasite infection. Oxidative stress in the short-term influences growth, reproduction, offspring survival and health. Long-term, oxidative damage to embryo DNA and changes in RNA expression, may influence lifetime performance of offspring. The high cost of providing mineral supplements to grazing sheep is a deterrence to addressing the implications of multiple mineral deficiencies. New herbaceous and shrub options to increase the botanical and nutritional diversity within pasture and crop-grazing systems may allow livestock to select a heterogeneous diet providing a more balanced mineral intake.

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.

Effect of sperm DNA fragmentation on embryo development: clinical and biological aspects

Objective

The aim of this study was to investigate the effect of sperm DNA fragmentation on fertilization rate, embryo development (blastulation rate), and pregnancy outcomes for ICSI cycles performed in a cohort of couples using donor eggs and to assess the remaining embryos that were not transferred or frozen for apoptotic markers.

Methods

Eighty-two women (egg recipients) were included in the study (2016) were included in the study. The recipients' mean age was 41.8±5.1 y/o (36-49), while the egg donors' mean age was 30.8±2.1 y/o (27-33). Even though donor egg cycles with frozen sperm samples are performed regularly in our center, 35 cycles were done using fresh sperm samples. The mean age of the males involved in the procedure was 40.1±5.2 y/o. Fertilization, blastulation, and pregnancy rates were assessed. The patients were divided into two groups, TUNEL <15% and ≥15%. In arrested embryos, ICC was performed to detect cleaved caspase-3, survivin, TUNEL, and DNA. The Student's t-test was used in between-group comparisons. The Mann-Whitney U-test was used to assess homogeneity. Pearson's correlation coefficient was also calculated. p<0.05 was considered statistically significant.

Results

This study showed that there is a negative correlation (R=-0.5) between DNA fragmentation and blastulation rate. High levels of DNA fragmentation were associated with low blastulation and pregnancy rates (per transfer); however, fertilization rate was not affected. Samples with higher levels of DNA fragmentation were associated with higher levels of DNA fragmentation in blastomeres without activating the apoptotic pathway (9.1% vs. 15.9%) (p<0.05). Blastomeres from samples with high DNA fragmentation activated the apoptotic pathway in higher levels than samples with TUNEL <15% (16.4% vs. 21.9%) (p<0.05).

Conclusion

Sperm DNA fragmentation was negatively correlated with blastulation and pregnancy rates even in good quality oocytes. High levels of DNA damage promote embryo arrest and induce the activation of the apoptotic pathway.

Intracytoplasmic sperm injection: state of the art in humans

Among infertile couples, 25% involve both male and female factors, while male factor alone accounts for another 25% due to oligo-, astheno-, teratozoospermia, a combination of the three, or even a complete absence of sperm cells in the ejaculate and can lead to a poor prognosis even with the help of assisted reproductive technology (ART). Intracytoplasmic sperm injection (ICSI) has been with us now for a quarter of a century and in spite of the controversy generated since its inception, it remains in the forefront of the techniques utilized in ART. The development of ICSI in 1992 has drastically decreased the impact of male factor, resulting in millions of pregnancies worldwide for couples who, without ICSI, would have had little chance of having their own biological child. This review focuses on the state of the art of ICSI regarding utility of bioassays that evaluate male factor infertility beyond the standard semen analysis and describes the current application and advances in regard to ICSI, particularly the genetic and epigenetic characteristics of spermatozoa and their impact on reproductive outcome.

Positive rheotaxis extended drop: a one-step procedure to select and recover sperm with mature chromatin for intracytoplasmic sperm injection

PURPOSE

The purpose of this study was to develop a novel one-step ICSI approach to select sperm with better chromatin maturity than the conventional method.

METHODS

This was a pilot diagnostic study, which prospectively recruited men during a 6-month period in a University-affiliated infertility centre. Forty consecutive semen samples were provided for analysis. The positive rheotaxis extended drop (PRED) was set up creating a pressure and viscosity gradient. Each semen sample was divided into four aliquots: one aliquot for density gradient centrifugation (DGC), two aliquots for PRED (fresh semen (PRED-FS) and processed semen (PRED-DGC)), and one aliquot as the control (FS). In PRED, a mean of 200 spermatozoa were collected consecutively without selection from the outlet reservoir. The aniline blue assay was used to assess chromatin immaturity.

RESULTS

The mean channel length, measured from inlet to outlet, was 32.55 ± 0.86 mm, with a mean width of 1.04 ± 0.21 mm. In 82.5% of cases (33/40), at least 50 spermatozoa were captured between 15 and 30 min. Improved chromatin maturity after the DGC preparation and the PRED approach was observed in all samples. This was reflected by a mean reduction from 28.65 ± 8.97% uncondensed chromatin in the native ejaculates to 17.29 ± 7.72% in DGC and 0.89 ± 1.31% in the PRED approach (P < 0.01).

CONCLUSIONS

The PRED method may improve the current ICSI technique by providing it with its own sperm selection process. ICSI would probably become an even more complete technique comprising selection, capture and injection of the male gamete.

Male Obesity: Epigenetic Origin and Effects in Sperm and Offspring

PURPOSE OF REVIEW

The prevalence of obesity has increased substantially in the current generations of Western countries, and the burden of obesity-related complications has been growing steadily. In men, obesity is not only a major risk factor for serious chronic diseases, concern is growing that the reproductive capacity, and more particularly, their offspring's health may be affected. Obesity-related impaired spermatogenesis is associated with a decrease in microscopic and molecular sperm characteristics and pregnancy success. We hypothesize that epigenetics is an important mediator explaining interactions between an obesogenic environment and sperm/offspring outcomes.

RECENT FINDINGS

Recent studies have explored inter- and transgenerational epigenetic effects in sperm cells and in offspring. Father-to-child effects have been reported in relation to preconceptional nutritional and life-style related factors.

SUMMARY

Here, we summarize the current understanding about obesity and molecular or epigenetic underlying mechanisms in sperm. We identify the obesogenic environment of the father before conception as a potential origin of health or disease in the offspring and include it as part of a new concept, the Paternal Origins of Health and Disease (POHaD).

Reproductive outcomes of testicular versus ejaculated sperm for intracytoplasmic sperm injection among men with high levels of DNA fragmentation in semen: systematic review and meta-analysis

OBJECTIVE

To compare sperm DNA fragmentation (SDF) levels between testicular and ejaculated sperm and to evaluate outcomes of intracytoplasmic sperm injection (ICSI) with the use of testicular (Testi-ICSI) versus ejaculated (Ejac-ICSI) sperm in nonazoospermic men with high SDF.

DESIGN

Systematic review and meta-analysis.

SETTING

Not applicable.

PATIENT(S)

Normo- and oligozoospermic men with high levels of SDF in semen subjected to Testi-ICSI or Ejac-ICSI.

INTERVENTION(S)

Summary mean difference (MD) and odds ratio (OR) were calculated with the use of an inverse variance model and fixed- or random-effects models, respectively.

MAIN OUTCOME MEASURE(S)

Primary outcomes were SDF levels, clinical pregnancy rates (CPRs), and live birth rates (LBRs). Secondary outcomes were fertilization and miscarriage rates.

RESULT(S)

Five studies involving 143 patients provided paired SDF rates for testicular and ejaculated sperm, revealing lower SDF in testicular sperm (MD -24.58%). Four studies involving 507 cycles and 3,840 oocytes reported clinical outcomes of Testi-ICSI and Ejac-ICSI. Fertilization rates were not different between sperm sources, but a trend to lower rates was observed with Testi-ICSI. CPRs were higher for Testi-ICSI than for Ejac-ICSI, as were LBRs, whereas miscarriage rates were reduced with Testi-ICSI.

CONCLUSION(S)

Testicular sperm have lower levels of SDF than ejaculated sperm, with Testi-ICSI for high post-testicular SDF men improving reproductive outcomes compared with Ejac-ICSI. Infertile couples may benefit from Testi-ICSI if male partners have confirmed high SDF in the ejaculate.

Clinical utility of sperm DNA fragmentation testing: concise practice recommendations

Sperm DNA integrity is generally acknowledged as an essential component for human reproduction. While the negative impact of high sperm DNA fragmentation (SDF) on outcomes of natural pregnancy and assisted reproductive technology (ART) is well known, the clinical indication of SDF testing is less well defined. A recent review on clinical utility of SDF testing highlighted the different SDF assays and clinical indications of SDF testing. This concise practice recommendations aim at summarizing the evidence and presenting to the readers the essence of the clinical utility of SDF testing based on the currently existing evidence. The potential role of SDF testing in varicocelectomy candidates, couples with recurrent pregnancy loss, patients with unexplained infertility, couples with failed assisted reproduction, and infertile men with exposure to modifiable lifestyle risk factors is illustrated. Recommendations from an expert panel on each clinical condition is presented, with levels of evidence.

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 telomere length in motile sperm selection techniques: A qFISH approach

Several studies have associated telomere shortening with alterations in reproductive function. The objective of the present study was to determine telomere length (TL) in spermatozoa selected by either density-gradient centrifugation (DGC) or swim-up. The analysis of TL was performed using quantitative fluorescent in situ hybridisation (qFISH) using PNA probes in combination with a chromatin decompaction protocol in sperm cells. Results of TL were 24.64 ± 5.00 Kb and 24.95 ± 4.60 Kb before and after DGC, respectively, and 19.59 ± 8.02 Kb and 20.22 ± 5.18 Kb before and after swim-up respectively. Sperm selected by DGC or swim-up did not show any significant differences in TL as compared to nonselected sperm (p > .05). Negative correlations between TL and sperm motility (r = -.308; p = .049) and concentration (r = -.353; p = .028) were found. Furthermore, exposure of sperm to increasing concentrations of hydrogen peroxide during incubation resulted in a reduction in TL. These data indicate that oxidative stress may be one of the main factors involved in the reduction of TL in sperm. Preliminary clinical results from patients included in this study indicate that TL was shorter in spermatozoa from couples who never achieved a pregnancy compared to couples who did achieve at least one natural pregnancy (p < .05); however, the clinical utility of this biomarker still needs to be confirmed in further studies.

Magnetic-activated cell sorting before density gradient centrifugation improves recovery of high-quality spermatozoa

Recent studies have evaluated the use of magnetic-activated cell sorting (MACS) to reduce apoptotic spermatozoa and improve sperm quality. However, the efficiency of using MACS alone, before or after sperm processing by density gradient centrifugation (DGC) has not yet been established. The purpose of this study is to determine the optimal protocol of MACS in assisted reproduction techniques (ART). Thus, we compared sperm quality obtained by DGC alone (DGC), DGC followed by MACS (DGC-MACS), MACS followed by DGC (MACS-DGC), and MACS alone (MACS), and found that the combined methods (MACS-DGC and DGC-MACS) led to retrieval of less spermatozoa with fragmented DNA compared to the single protocols. However, MACS-DGC protocol led to a significantly higher percentage of spermatozoa with progressive motility and normal morphology than DGC-MACS protocol. These findings suggest the potential clinical value of using MACS-DGC to improve sperm quality in seminal preparation for ART.

Sperm DNA fragmentation index does not correlate with blastocyst aneuploidy or morphological grading

High DNA fragmentation index (DFI) may be associated with poor outcome after IVF. Our aim was to determine whether DFI impacts blastocyst quality or clinical outcome. This retrospective study included 134 couples who underwent 177 IVF-ICSI and pre-implantation genetic screening (PGS) cycles during January 1st, 2014-March 31st, 2016 and had documented previous DFI. Group 1 (DFI>30%) encompassed 25 couples who underwent 36 cycles; Group 2 (DFI 15-30%) included 45 couples and 57 cycles; group 3 (DFI<15%) included 64 couples and 83 cycles. Male partners within group 1 were older (45.1 compared to 40.6 and 38.3 years, respectively, p<0.05), had higher BMI (32.4 compared to 26.6 and 25.8 respectively, p<0.05) and lower sperm count and motility (46*106/ml and 35.5%, respectively) compared to groups 2 (61.8*106/ml and 46.6%, respectively) and 3 (75.8*106/ml and 55.1%, respectively, p<0.05). Female parameters including ovarian reserve and response and embryo development were similar. Total numbers of biopsied blastocysts were 116, 175 and 259 in groups 1, 2 and 3, respectively. PGS for 24 chromosomes revealed comparable euploidy rate of 46-50.4%, with a similar morphological classification. No significant differences were found regarding pregnancy rates or pregnancy loss. It seems that DFI doesn't correlate with blastocyst aneuploidy or morphological grading.

Genome-wide 5-hydroxymethylcytosine patterns in human spermatogenesis are associated with semen quality

We performed immunofluorescent analysis of DNA hydroxymethylation and methylation in human testicular spermatogenic cells from azoospermic patients and ejaculated spermatozoa from sperm donors and patients from infertile couples. In contrast to methylation which was present throughout spermatogenesis, hydroxymethylation was either high or almost undetectable in both spermatogenic cells and ejaculated spermatozoa. On testicular cytogenetic preparations, 5-hydroxymethylcytosine was undetectable in mitotic and meiotic chromosomes, and was present exclusively in interphase spermatogonia Ad and in a minor spermatid population. The proportions of hydroxymethylated and non-hydroxymethylated diploid and haploid nuclei were similar among samples, suggesting that the observed alterations of 5-hydroxymethylcytosine patterns in differentiating spermatogenic cells are programmed. In ejaculates, a few spermatozoa had high 5-hydroxymethylcytosine level, while in the other ones hydroxymethylation was almost undetectable. The percentage of highly hydroxymethylated (5-hydroxymethylcytosine-positive) spermatozoa varied strongly among individuals. In patients from infertile couples, it was higher than in sperm donors (P<0.0001) and varied in a wider range: 0.12-21.24% versus 0.02-0.46%. The percentage of highly hydroxymethylated spermatozoa correlated strongly negatively with the indicators of good semen quality – normal morphology (r=-0.567, P<0.0001) and normal head morphology (r=-0.609, P<0.0001) – and strongly positively with the indicator of poor semen quality: sperm DNA fragmentation (r=0.46, P=0.001). Thus, the immunocytochemically detected increase of 5hmC in individual spermatozoa is associated with infertility in a couple and with deterioration of sperm parameters. We hypothesize that this increase is not programmed, but represents an induced abnormality and, therefore, it can be potentially used as a novel indicator of semen quality.

Effect of Vitamin E and Polyunsaturated Fatty Acids on Cryopreserved Sperm Quality in Bos taurus Bulls Under Testicular Heat Stress

Taurine bulls are highly susceptible to heat stress, leading to increased oxidative stress (OS) and impaired sperm viability. Polyunsaturated fatty acids (PUFAs) supplementation can be an alternative to improve semen quality, which also results in more sperm susceptibility to lipid peroxidation. Moreover, this deleterious effect can be exacerbated in animals affected by heat stress. Vitamin E is a key antioxidant that counteracts lipid peroxidation of sperm membrane caused by OS. Thus, combining PUFAs with vitamin E may improve sperm quality. In this context, this study aimed to evaluate the effect of interaction between PUFAs and vitamin E on sperm quality in Bos taurus bulls under testicular heat stress. Sixteen taurine bulls under testicular heat stress were randomly assigned in four groups: Control, Vitamin E, PUFA, and PUFA + Vitamin E. All groups lasted for 60 days. Samples were cryopreserved/thawed and analyzed for motility variables (CASA), membrane and acrosome integrity, mitochondrial activity, susceptibility to oxidative stress, DNA integrity, and sperm-binding capacity. Results showed that vitamin E had a beneficial effect on some sperm characteristics, whereas PUFA supplementation had an adverse effect when the two treatments were evaluated separately. Finally, the association between PUFAs and vitamin E did not improve sperm quality.

FSH treatment in infertile males candidate to assisted reproduction improved sperm DNA fragmentation and pregnancy rate

The purpose of this study is to evaluate whether follicle-stimulating hormone treatment improves sperm DNA parameters and pregnancy outcome in infertile male candidates to in-vitro fertilization.Observational study in 166 infertile male partners of couples undergoing in-vitro fertilization. Eighty-four patients were receiving follicle-stimulating hormone treatment (cases) and 82 refused treatment (controls). Semen parameters, sexual hormones, and sperm nucleus (fluorescence in-situ hybridization, acridine orange, TUNEL, and γH2AX) were evaluated at baseline (T0) and after 3 months (T1), when all subjects underwent assisted reproduction techniques. Statistical analysis was performed by analysis of variance.Compared to baseline, cases showed significant improvements in seminal parameters and DNA fragmentation indexes after follicle-stimulating hormone therapy (all P < 0.05), whereas no changes were observed in controls. Within cases, follicle-stimulating hormone treatment allowed to perform intrauterine insemination in 35 patients with a pregnancy rate of 23.2 %. Intracytoplasmic sperm injection was performed in all controls and in 49 patients from cases, with pregnancy rates of 23.2 and 40.8 %, respectively (P < 0.05). After 3 months (T0 vs. T1) of follicle-stimulating hormone therapy, cases with positive outcome had reduced DNA fragmentation index and lower double strand breaks (P < 0.05 and P < 0.001 vs. negative outcome, respectively).In this observational study, we showed that follicle-stimulating hormone treatment improves sperm DNA fragmentation, which in turn leads to increased pregnancy rates in infertile males undergoing in-vitro fertilization. In particular, double strand breaks (measured with γH2AX test) emerged as the most sensible parameter to follicle-stimulating hormone treatment in predicting reproductive outcome.