Relationships between human sperm protamines, DNA damage and assisted reproduction outcomes

Sperm epigenetics and male infertility: unraveling the molecular puzzle

BACKGROUND

The prevalence of infertility among couples is estimated to range from 8 to 12%. A paradigm shift has occurred in understanding of infertility, challenging the notion that it predominantly affects women. It is now acknowledged that a significant proportion, if not the majority, of infertility cases can be attributed to male-related factors. Various elements contribute to male reproductive impairments, including aberrant sperm production caused by pituitary malfunction, testicular malignancies, aplastic germ cells, varicocele, and environmental factors.

MAIN BODY

The epigenetic profile of mammalian sperm is distinctive and specialized. Various epigenetic factors regulate genes across different levels in sperm, thereby affecting its function. Changes in sperm epigenetics, potentially influenced by factors such as environmental exposures, could contribute to the development of male infertility.

CONCLUSION

In conclusion, this review investigates the latest studies pertaining to the mechanisms of epigenetic changes that occur in sperm cells and their association with male reproductive issues.

Sperm Head Morphology Alterations Associated with Chromatin Instability and Lack of Protamine Abundance in Frozen-Thawed Sperm of Indonesian Local Bulls

This study aimed to analyze various alterations in the morphology of the sperm head and its association with nucleus instability and insufficient sperm protamine. Frozen-thawed semen from twenty local Indonesian bulls was used for all stages in this study. The results of sperm head defect assessments are used for bull grouping, high (HD) and low (LD). Sperm DNA damage was assessed using Acridine Orange and Halomax. The PRM1 protein abundance was carried out using an enzyme immunoassay, while PRM1 gene expression was carried out using the RT-qPCR. PRM deficiency was performed using CMA3. Several kinds of sperm head defects in the HD were significantly higher (p < 0.05) than in the LD bulls. Sperm DNA damage showed a significant (p < 0.05) difference between the HD and LD bulls. PRM1 abundance was significantly (p < 0.05) decreased in HD bulls. PRM deficiency was significantly (p < 0.05) higher in HD bulls than in LD bulls. PRM deficiency in bulls correlated significantly (p < 0.01) with sperm head defects, DNA damage, and PRM1 abundance. The lack of sperm protamine might affect the sperm nucleus's stability and induce morphological alterations in the sperm head.

Evaluation of Sperm DNA Fragmentation Using Two Different Methods: TUNEL via Fluorescence Microscopy, and Flow Cytometry

Background and Objectives: Sperm DNA fragmentation refers to any break in one or both of the strands of DNA in the head of a sperm. The most widely used methodologies for assessing sperm DNA fragmentation are the sperm chromatin structure assay (SCSA), the sperm chromatin dispersion assay (SCD), the single-cell gel electrophoresis assay (SCGE-comet), and the terminal-deoxynucleotidyl-transferase (TdT)-mediated dUTP nick end labelling (TUNEL) assay. The aim of this study was to compare the efficiency and sensitivity of the analysis of sperm DNA fragmentation using TUNEL via fluorescence microscopy, and flow cytometry. Materials and Methods: Semen samples were collected and analyzed for standard characteristics using light microscopy, and for sperm DNA fragmentation using both TUNEL via fluorescence microscopy, and flow cytometry. Results: There were no significant differences in the values of the sperm DNA fragmentation index (DFI) obtained when the analysis was performed using TUNEL or flow cytometry (p = 0.543). Spearman's correlation analysis revealed a significant negative correlation between sperm motility (%) and sperm DNA fragmentation (p < 0.01), as well as between sperm concentration and sperm DNA fragmentation (p < 0.05). The Mann-Whitney U test showed no significant difference in the DFI among couples with repeated implantation failure (RIF) and miscarriages (p = 0.352). Conclusions: Both methods (TUNEL via fluorescence microscopy, and flow cytometry) have a high efficiency and sensitivity in accurately detecting sperm DNA fragmentation, and can be effectively used to assess male fertility.

Separating the chaff from the wheat: antibody-based removal of DNA-fragmented sperm

STUDY QUESTION

Is it possible to remove sperm with damaged DNA from a semen sample?

SUMMARY ANSWER

By using immunomagnetic cell sorting that targets the sperm head-bound epididymal sperm-binding protein 1 (ELSPBP1), it was possible to produce an ELSPBP1(-) sperm fraction characterized by consistently lower levels of sperm DNA fragmentation (SDF).

WHAT IS KNOWN ALREADY

In bovines, ELSPBP1 is bound to dead spermatozoa. Human ejaculates with high SDF have increased detected levels of sperm ELSPBP1 when compared to ejaculates with low native SDF.

STUDY DESIGN, SIZE, DURATION

We recruited 267 patients who were referred to the clinic for conjugal infertility. After applying exclusion criteria, such as fever within 90 days of the study, history of systemic diseases, alterations or surgical interventions to the genital tract and use of cigarette or drugs, a total of 133 patients were included. A total of 52 samples were used for the evaluation of sperm ELSPBP1 levels (Sub-study 1), 41 samples for determination of ELSPBP1 location in human sperm (Sub-study 2), and 40 samples for immunomagnetic cell sorting targeting ELSPBP1, to produce ELSPBP1(-) (without ELSPBP1) and ELSPBP1(+) (with ELSPBP1) fractions (Sub-study 3). Samples were collected between July 2016 and September 2019.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In Sub-study 1, sperm ELSPBP1 levels were assessed by western blotting. For Sub-study 2, ELSPBP1 was localized in sperm by immunocytochemistry. Finally, for Sub-study 3, sperm were selected based on incubation of semen samples with antibody-coated magnetic microspheres targeting ELSPBP1. Two fractions were produced (with or without ELSPBP1), and these sub-populations were submitted to an alkaline Comet assay for determination of SDF.

MAIN RESULTS AND THE ROLE OF CHANCE

Men with high SDF presented higher sperm ELSPBP1 levels when compared to the control group (low SDF), while no difference between groups was observed in seminal plasma. ELSPBP1 was located in the head region of human sperm. The ELSPBP1(+) fractions presented high and variable levels of SDF, while their paired ELSPBP(-) fractions presented consistently low SDF.

LIMITATIONS, REASONS FOR CAUTION

This work did not validate the levels of ELSPBP1 in other functional alterations of sperm, such as acrosome integrity or mitochondrial activity. Moreover, this is still a pre-clinical study, intended to demonstrate proof-of-concept that ELSPBP1 selects sperm with low DNA fragmentation; further investigation is warranted to demonstrate safety for use in ART. Sperm fractions were not assessed for sperm vitality. A clinical trial is still necessary for these findings to be extrapolated to outcomes in ART.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings demonstrate that ELSPBP1 is associated with sperm with higher levels of DNA fragmentation. The finding that the sperm membrane can reflect alterations in DNA integrity could give rise to a novel molecular method for sperm preparation prior to use of assisted reproductive procedures. Moreover, the detection of sperm-bound ELSPBP1 could serve as an indirect method for the determination of DNA fragmentation.

STUDY FUNDING/COMPETING INTEREST(S)

L.B.B. was a recipient of a Ph.D. scholarship from the Sao Paulo Research Foundation-FAPESP (process number 2016/05487-3). R.P.B. is a recipient of a Scientific Productivity scholarship from the Brazilian National Council for Scientific and Technological Development-CNPq (process number 306705/2017-6). The authors have no conflict of interest to disclose.

TRIAL REGISTRATION NUMBER

N/A.

What Does Intracytoplasmic Sperm Injection Change in Embryonic Development? The Spermatozoon Contribution

The intracytoplasmic sperm injection (ICSI) technique was invented to solve severe male infertility due to altered sperm parameters. Nowadays, it is applied worldwide for the treatment of couple infertility. ICSI is performed with any available spermatozoon from surgery or ejaculated samples, whatever are the sperm motility, morphology or quantity. The aim of the present review was to study if embryo development and kinetics would be modified by (1) ICSI under the technical aspects, (2) the micro-injected spermatozoa in connection with male infertility. From published data, it can be seen that ICSI anticipates the zygote kinetics Furthermore, because fertilization rate is higher in ICSI compared to conventional in vitro fertilization (IVF), more blastocysts are obtained for clinical use in ICSI. Sperm and spermatozoa characteristics, such as sperm parameters, morphology and vitality, DNA content (levels of sperm DNA fragmentation, microdeletions, and chromosomal abnormalities), RNA content, epigenetics, and sperm recovery site (testicular, epididymis, and ejaculated), have an impact on fertilization and blastocyst rates and embryo kinetics in different ways. Even though ICSI is the most common solution to solve couples' infertility, the causes of male infertility are crucial in building a competent spermatozoa that will contribute to normal embryonic development and healthy offspring.

Sperm DNA fragmentation in men vaccinated with Gam-COVID-Vac (Sputnik V)

Aim. To perform comparative analysis of sperm characteristics and DNA fragmentation in men vaccinated with GamCOVID-Vac (Sputnik V) and unvaccinated men.

Materials and methods. Characteristics ofsemen analysis and DNA fragmentation index in ejaculate samples of 122 men, 28 of whom were vaccinated with Gam-COVID-Vac (Sputnik V), were analyzed. Study participants did not have history of coronavirus infection COVID-19. Vaccinated patients were divided into 2 groups: group 1 (n = 10) included patients for whom the time between full vaccination (2 doses of the vaccine) and ejaculate sampling was shorter than 75 days; and the group 2 (n = 18) included patients for whom the time between vaccination and ejaculate sampling was longer than 75 days. Unvaccinated men comprised the control group (group 3, n = 94). Standard semen analysis was performed in accordance with the accepted laboratory guidelines of the World Health Organization (2010). DNA fragmentation was evaluated using fluorescent labelling of single- and double-strand DNA breaks (TUNEL).

Results. Totalsperm countin the group 1 was 265 ± 75 million, in the group 2 – 355 ± 67 million, in the group 3 – 304 ± 26 million. Progressive motile (PR)sperm in the group 1was 18.5 ± 1.9 %, in the group 2 – 23.2 ± 3.0 %, in the group 3 – 18.2 ± 1.1 %. Normal sperm morphology in the group 1 was 4.0 ± 0.5 %, in the group 2 – 5.8 ± 0.9 %, in the group 3 – 4.1 ± 0.3 %. The best ejaculate quality was observed in patients of the group 2, however, no statistically significant differences in semen analysis characteristics between the groups were found. Percentage of sperm with fragmented DNA (DNA fragmentation index, DFI) in the group 1 varied between 4.6 and 31.4 %, in the group 2 between 0.8 and 36.5 %, in the group 3 (control) between 1.3 and 39.8 %. Mean number of germ cells with DNA breaksin the group 1 (12.5 ± 2.4 %) was higher than in the group 2 (10.9 ± 2.0 %) and control group (10.5 ± 0.7 %), but with no statistical significance. Percentage of patients with DNA fragmentation index above the reference value (≤15 %) in the groups 1, 2 and 3 was 20, 22 and 18 % respectively. In 3 of 6 patients with increased DFI in the groups 1 and 2, this value was above the reference level even before vaccination.

Conclusion. No significant effect of vaccination with Sputnik V on sperm DNA fragmentation level in men was observed.

The Association of Certain Seminal Phthalate Metabolites on Spermatozoa Apoptosis: An Exploratory Mediation Analysis via Sperm Protamine

Earlier studies have suggested that exposure to phthalates (PAEs) may induce spermatozoa apoptosis. Sperm protamine as a molecular biomarker during spermatozoa apoptotic processes may mediate the association between PAE exposure and spermatozoa apoptosis. This study aimed to explore whether sperm protamine mediates the association of PAE exposure with spermatozoa apoptosis. We determined sperm protamine levels, 8 PAE metabolite concentrations in seminal plasma, and 3 spermatozoa apoptosis parameters among 111 men from an infertility clinic. The associations of PAEs as individual chemicals and mixtures with sperm protamine were determined. The mediating roles of protamine in the associations between PAEs and spermatozoa apoptosis parameters were examined by mediation analysis. After adjusting for confounders, we observed positive correlations between seminal plasma concentrations of mono(2-ethylhexyl) phthalate (MEHP) and sperm protamine-1 and protamine ratio. Estimates comparing highest vs. lowest quartiles of MEHP concentration were 4.65% (95% CI: 1.47%, 7.82%) for protamine-1 and 25.86% (95% CI: 3.05%, 53.73%) for protamine ratio. The quantile g-computation models showed that the adjusted protamine-1 per quartile increase in PAE mixture was 9.42% (95% CI: 1.00, 20.92) with MEHP being the major contributor. Although the joint association between PAE mixture and protamine ratio was negligible, MEHP was still identified as the main contributor. Furthermore, we found that protamine-2 and protamine ratio levels in the highest quartiles exhibited a decrease of 43.45% (95% CI: 60.54%, -19.75%) and an increase of 122.55% (95% CI: 60.00%, 209.57%) in Annexin V⁺/PI^- spermatozoa relative to the lowest quartiles, respectively. Mediation analysis revealed that protamine ratio significantly mediated 55.6% of the association between MEHP and Annexin V⁺/PI^- spermatozoa elevation (5.13%; 95% CI: 0.04%, 10.52%). Our findings provided evidence that human exposure to PAEs was associated with increased protamine levels which may mediate the process of spermatozoa apoptosis.

A Genome-Wide Association Study for Tolerance to Paratuberculosis Identifies Candidate Genes Involved in DNA Packaging, DNA Damage Repair, Innate Immunity, and Pathogen Persistence

Although the genetic susceptibility to diseases has been extensively studied, the genetic loci and the primary molecular and cellular mechanisms that control disease tolerance are still largely unknown. Bovine paratuberculosis (PTB) is an enteritis caused by Mycobacterium avium subsp. paratuberculosis (MAP). PTB affects cattle worldwide and represents a major issue on animal health. In this study, the associations between host genetic and PTB tolerance were investigated using the genotypes from 277 Spanish Holstein cows with two distinct phenotypes: cases) infected animals with positive PCR and bacteriological culture results but without lesions in gut tissues (N= 24), and controls) animals with negative PCR and culture results but with PTB-associated lesions (N= 253). DNA from peripheral blood of the study population was genotyped with the Bovine EuroG MD Bead Chip, and the corresponding genotypes were imputed to whole-genome sequencing (WGS) data. A genome-wide association study was performed using the WGS data and the defined phenotypes in a case-control approach. A total of 142 single nucleotide polymorphisms (SNPs) were associated (false discovery rate ≤ 0.05, P values between 1.5 × 10^-7 and 5.7 × 10^-7) with tolerance (heritability= 0.55). The 40 SNPs with P-values < 5 × 10^-7 defined 9 QTLs and 98 candidate genes located on BTA4, BTA9, BTA16, BTA25, and BTA26. Some of the QTLs identified in this study overlap with QTLs previously associated with PTB, bovine tuberculosis, mastitis, somatic cell score, bovine diarrhea virus persistent infection, tick resistance, and length of productive life. Two candidate genes with important roles in DNA damage response (ERCC4 and RMI2) were identified on BTA25. Functional analysis using the 98 candidate genes revealed a significant enrichment of the DNA packaging process (TNP2/PRMI1/PRM2/PRM3). In addition, the TNF-signaling (bta04668; TRAF5/CREB5/CASP7/CHUK) and the toxoplasmosis (bta05145; TGFβ2/CHUK/CIITA/SOCS1) pathways were significantly enriched. Interestingly, the nuclear Factor NF-κβ Inhibitor Kinase Alpha (CHUK), a key molecule in the regulation of the NF-κB pathway, was enriched in both pathways. Taken together, our results define a distinct immunogenetic profile in the PTB-tolerant animals designed to control bacterial growth, modulate inflammation, limit tissue damage and increase repair, thus reducing the severity of the disease.

PRM1 Gene Expression and Its Protein Abundance in Frozen-Thawed Spermatozoa as Potential Fertility Markers in Breeding Bulls

Functional genes and proteins in sperm play an essential role in bulls’ reproductive processes. They are more accurate in determining bull fertility than conventional semen quality tests. Protamine-1 (PRM1) is a gene or protein crucial for packaging and protecting sperm DNA until fertilization affects normal sperm function. This study analyzes the genes and proteins potential from PRM1 as fertility markers for different breeds of bulls utilized in the artificial insemination programs, expected to be an accurate tool in interpreting bull fertility in Indonesia. This study used Limousin, Holstein, and Ongole Grade bulls divided into two groups based on fertility, high-fertility (HF) and low fertility (LF). The semen quality assessment included progressive motility (computer-assisted semen analysis), viability (eosin-nigrosine), and plasma membrane integrity (HOS test). Sperm DNA fragmentation (SDF) was assessed using the acridine orange staining and the Halomax test. Sperm PRM deficiency was evaluated with the chromomycin A3 method. Moreover, PRM1 gene expression was measured using qRT-PCR, and the PRM1 protein abundance was measured with the enzyme immunoassay method. Semen quality values, relative expression of PRM1 gene, and quantity of PRM1 protein were significantly higher (p < 0.05) in HF bulls than in LF bulls. The SDF and PRM deficiency values in LF bulls were significantly higher (p < 0.05) than HF bulls. Additionally, PRM1 at the gene and protein levels correlated significantly (p < 0.01) with fertility. Therefore, PRM1 is a potential candidate for fertility markers in bulls in Indonesia.

Direct visualization of pre-protamine 2 detects protamine assembly failures and predicts ICSI success

Histone-to-protamine transition is an essential step in the generation of fully functional spermatozoa in various mammalian species. In human and mouse, one of the two protamine-encoding genes produces a precursor pre-protamine 2 (pre-PRM2) protein, which is then processed and assembled. Here we design an original approach based on the generation of pre-PRM2-specific antibodies to visualize the unprocessed pre-PRM2 by microscopy, flow cytometry and immunoblotting. Using mouse models with characterized failures in histone-to-protamine replacement, we show that pre-Prm2 retention is tightly linked to nucleosome disassembly. Additionally, in elongating/condensing spermatids, we observe that pre-Prm2 and transition protein are co-expressed spatiotemporally, and their physical interaction suggests that these proteins act simultaneously rather than successively during histone replacement. By using our anti-human pre-PRM2 antibody we also measured pre-PRM2 retention rates in the spermatozoa from 49 men of a series of infertile couples undergoing ICSI, which shed new light on the debated relation between pre-PRM2 retention and sperm parameters. Finally, by monitoring 2-pronuclei (2PN) embryo formation following ICSI, we evaluated the fertilization ability of the sperm in these 49 patients. Our results suggest that the extent of pre-PRM2 retention in sperm, rather than pre-PRM2 accumulation per se, is associated with fertilization failure. Hence, anti-pre-PRM2/pre-Prm2 antibodies are valuable tools which could be used in routine monitoring of sperm parameters in fertility clinics, as well as in experimental research programmes to better understand the obscure process of histone-to-protamine transition.

Identification of biomarkers for bull fertility using functional genomics

Prediction of bull fertility is critical for the sustainability of both dairy and beef cattle production. Even though bulls produce ample amounts of sperm with normal parameters, some bulls may still suffer from subpar fertility. This causes major economic losses in the cattle industry because using artificial insemination, semen from one single bull can be used to inseminate hundreds of thousands of cows. Although there are several traditional methods to estimate bull fertility, such methods are not sufficient to explain and accurately predict the subfertility of individual bulls. Since fertility is a complex trait influenced by a number of factors including genetics, epigenetics, and environment, there is an urgent need for a comprehensive methodological approach to clarify uncertainty in male subfertility. The present review focuses on molecular and functional signatures of bull sperm associated with fertility. Potential roles of functional genomics (proteome, small noncoding RNAs, lipidome, metabolome) on determining male fertility and its potential as a fertility biomarker are discussed. This review provides a better understanding of the molecular signatures of viable and fertile sperm cells and their potential to be used as fertility biomarkers. This information will help uncover the underlying reasons for idiopathic subfertility.

Sperm bauplan and function and underlying processes of sperm formation and selection

The spermatozoon is a highly differentiated and polarized cell, with two main structures: the head, containing a haploid nucleus and the acrosomal exocytotic granule, and the flagellum, which generates energy and propels the cell; both structures are connected by the neck. The sperm's main aim is to participate in fertilization, thus activating development. Despite this common bauplan and function, there is an enormous diversity in structure and performance of sperm cells. For example, mammalian spermatozoa may exhibit several head patterns and overall sperm lengths ranging from ∼30 to 350 µm. Mechanisms of transport in the female tract, preparation for fertilization, and recognition of and interaction with the oocyte also show considerable variation. There has been much interest in understanding the origin of this diversity, both in evolutionary terms and in relation to mechanisms underlying sperm differentiation in the testis. Here, relationships between sperm bauplan and function are examined at two levels: first, by analyzing the selective forces that drive changes in sperm structure and physiology to understand the adaptive values of this variation and impact on male reproductive success and second, by examining cellular and molecular mechanisms of sperm formation in the testis that may explain how differentiation can give rise to such a wide array of sperm forms and functions.

Sperm chromatin condensation as an in vivo fertility biomarker in bulls: a flow cytometry approach

Background

Genetic selection in cattle has been directed to increase milk production. This, coupled to the fact that the vast majority of bovine artificial inseminations (AI) are performed using cryopreserved sperm, have led to a reduction of fertility rates over the years. Thus, seeking sensitive and specific sperm biomarkers able to predict fertility rates is of vital importance to improve cattle reproductive efficiency. In humans, sperm chromatin condensation evaluated through chromomycin A3 (CMA3) has recently been purported to be a powerful biomarker for sperm functional status and male infertility. The objectives of the present study were: a) to set up a flow cytometry method for simultaneously evaluating chromatin condensation and sperm viability, and b) to test whether this parameter could be used as a predictor of in vivo fertility in bulls. The study included pools of three independent cryopreserved ejaculates per bull from 25 Holstein males. Reproductive outcomes of each sire were determined by non-return rates, which were used to classify bulls into two groups (highly fertile and subfertile).

Results

Chromatin condensation status of bovine sperm was evaluated through the combination of CMA3 and Yo-Pro-1 staining and flow cytometry. Sperm quality parameters (morphology, viability, total and progressive motility) were also assessed. Pearson correlation coefficients and ROC curves were calculated to assess their capacity to predict in vivo fertility. Sperm morphology, viability and total motility presented an area under the ROC curve (AUC) of 0.54, 0.64 and 0.68, respectively (P > 0.05), and thus were not able to discriminate between fertile and subfertile individuals. Alternatively, while the percentage of progressively motile sperm showed a significant predictive value, with an AUC of 0.73 (P = 0.05), CMA3/Yo-Pro-1 staining even depicted superior results for the prediction of in vivo fertility in bulls. Specifically, the percentage of viable sperm with poor chromatin condensation showed better accuracy and precision to predict in vivo fertility, with an AUC of 0.78 (P = 0.02).

Conclusions

Chromatin condensation evaluated through CMA3/Yo-Pro-1 and flow cytometry is defined here as a more powerful tool than conventional sperm parameters to predict bull in vivo fertility, with a potential ability to maximising the efficiency of dairy breeding industry.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00634-7.

Aerobic training mitigates the negative impact of diabetes on fertility

Diabetes negatively affects the reproductive system. This present study investigated the effects of aerobic training on protamine 1 and 2 mRNA expression, sex hormones, antioxidant defence and sperm quality in diabetic rats. Thirty-six male Wistar rats were randomly allocated into three groups including diabetic training (DT) group, diabetic (D) group and control (C) group. Rats in DT were exercised 5 times per week for 8 weeks. Blood samples were collected for evaluation of sex hormones 48 h after the last training session. Also, the testes were removed and subjected to histological evaluation and semen analysis. Testicular mRNA expressions of protamines were determined by RT-qPCR. Protamines 1 and 2, and the ratio of protamine 1 to protamine 2 were significantly lower in DT and D groups compared with C group (p < 0.01). LH and testosterone levels were significantly lower in D group compared with DT and C group (p < 0.01). Malondialdehyde was significantly lower in DT and C groups compared with D group (p < 0.001). Sperm parameters were significantly lower in D group compared with C group (p < 0.01). Our findings suggest that aerobic training may mitigate the negative impact of diabetes on sex hormones, oxidative stress, protamine content and sperm parameters in male rats.

Association among sperm chromatin condensation, sperm DNA fragmentation and 8-OHdG in seminal plasma and semen parameters in infertile men with oligoasthenoteratozoospermia

The present study aimed to investigate the clinical role of standard sperm diagnosis parameters (sperm concentration, motility, morphology) as well as aniline blue staining of histones, 8-OHdG, TUNEL assay were performed on semen samples in infertile men with oligoasthenoteratozoospermia (OAT). Thirty-two infertile and ten proven fertile men were included in the study. Chromatin condensation sperm in infertile men was significantly lower compared to the fertile men (p < 0.0001). Age, sperm concentration, morphology and motility were significantly negatively correlated with chromatin condensation (p < 0.05). However, no significant correlations among the chromatin condensation, SDF and sperm DNA damage were detected in terms of 8-OHdG concentration.

Chronic Prostatitis/Chronic Pelvic Pain Syndrome Leads to Impaired Semen Parameters, Increased Sperm DNA Fragmentation and Unfavorable Changes of Sperm Protamine mRNA Ratio

BACKGROUND

Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS) is a frequent disease affecting men of every age and accounting for a great number of consultations at urology departments. Previous studies suggested a negative impact of CP/CPPS on fertility. As increasing attention has been attributed to additional aspects, such as sperm DNA integrity and sperm protein alterations, besides the WHO standard semen analysis when assessing male fertility, in this prospective study, we aimed to further characterize the fertility status in CP/CPPS patients with a focus on these parameters.

METHODS

Sperm DNA fragmentation measured by sperm chromatin structure assay (SCSA) and protamine 1 to protamine 2 mRNA ratio assessed by RT-qPCR were analyzed along with conventional ejaculate parameters and inflammatory markers in 41 CP/CPPS patients and 22 healthy volunteers.

RESULTS

We found significant differences between the groups concerning multiple conventional ejaculate parameters. A significant increase in sperm DNA fragmentation was shown in CP/CPPS patients with association to other sperm parameters. The majority of CP/CPPS patients exhibited protamine mRNA ratios out of the range of regular fertility.

CONCLUSIONS

This is a pioneering study with a strong practical orientation revealing that CP/CPPS leads to increased sperm DNA damage and changes in sperm protamine levels, emphasizing an unfavorable impact of CP/CPPS on fertility.

Do Seminal Isoprostanes Have a Role in Assisted Reproduction Outcome?

F₂-isoprostanes (F₂-IsoPs), stereoisomers of prostaglandin F2α generated by the free radical-induced oxidation of arachidonic acid, have been associated with different male infertility conditions. This study aimed to evaluate the role of seminal isoprostane levels and sperm characteristics in the reproductive outcome and embryo quality of 49 infertile couples. Semen analysis was performed following WHO guidelines. Sperm chromatin maturity was detected using an aniline blue (AB) assay, and DNA integrity was assessed using the acridine orange (AO) test. Seminal F₂-IsoP levels were quantified by gas chromatography/negative ion chemical ionization tandem mass spectrometry (GC/NICI–MS/MS) analysis. Correlations among variables and their impact on in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) outcome were investigated. F₂-IsoP levels are positively correlated with double-stranded DNA sperm (p < 0.001) and negatively correlated with mature sperm chromatin (p < 0.001). Patients with positive outcomes had an increased percentage of sperm with double-stranded DNA, as did patients producing high-quality embryo, who showed higher F₂-IsoP levels compared to those detected in the low-quality embryo group. An intriguing relationship between a mild increase in F₂-IsoP levels, DNA integrity, and embryo quality seems to indicate that the non-enzymatic oxidation of arachidonic acid can be also a marker of metabolic activity in human semen.

The paternal toolbox for embryo development and health

The sperm is essential for reconstitution of embryonic diploidy and highly specialized developmental functions. Immediately after gamete fusion, the sperm-borne PLC-zeta triggers activation, generating intracellular free Ca2+ oscillations. Mutations in the PLC-zeta encoding gene are associated with the absence of this factor in mature sperm and inability to achieve fertilization. Sperm play also a role in the greater game of the choreography of fertilization. In the human, the sperm centrioles are introduced into the oocyte environment with gamete fusion. They interact with the oocyte cytoskeletal apparatus to form a functional pair of centrosomes and ultimately regulate pronuclear juxtaposition in preparation for the first cleavage. As a consequence, the fidelity of chromosome segregation during the first cell divisions depends on the function of sperm centrioles. Sperm DNA integrity is essential for embryo development and health. Damaged DNA does not impact on the sperm fertilization ability following ICSI. However, detrimental effects emerge at pre- and post-implantation stages. Sperm-specific epigenetic factors also play an active role in the regulation of embryonic development, as shown by correlations between reduced embryo morphological quality and incorrect chromatin packaging during spermiogenesis or abnormal methylation of sperm CpG islands. This functional landscape demonstrates that the contribution of the sperm to development goes far beyond its well-established role in fertilization. Clinical studies confirm this view and indicate sperm function as a crucial aspect of research to increase the efficacy of assisted reproduction treatments.

Detailed cell-level analysis of sperm nuclear quality among the different hypo-osmotic swelling test (HOST) classes

PURPOSE

We studied the quality differences between the different hypo-osmotic swelling test (HOST) classes, as measured by criteria of DNA fragmentation, DNA decondensation, and nuclear architecture. The aim was to find particular HOST classes associated with good-quality metrics, which may be potentially used in ICSI (intra-cytoplasmic sperm injection).

METHODS

Ten patients from the Department of Reproductive Medicine at Tenon Hospital (Paris, France) were included. Their semen samples were collected and divided into two fractions: one was incubated in a hypo-osmotic solution as per HOST protocol and sorted by sperm morphology, and a second was incubated without undergoing the HOST protocol to serve as an unsorted baseline. Three parameters were assessed: DNA fragmentation (TUNEL assay), DNA decondensation (chromomycin A3 assay), and nuclear architecture (FISH, with telomeric and whole chromosome painting probes). The different HOST classes were evaluated for these three parameters, and statistical analysis was performed for each class versus the unsorted non-HOST-treated sperm. Results with p<0.05 were considered statistically significant.

RESULTS

For each of the parameters evaluated, we found significant differences between HOST-selected spermatozoa and non-selected spermatozoa. Overall, spermatozoa of HOST classes B and B+ exhibited the highest quality based on four metrics (low DNA fragmentation, low DNA decondensation, short inter-telomeric distance, and small chromosome 1 territory area), while spermatozoa of HOST classes A and G exhibited the poorest quality by these metrics.

CONCLUSION

In addition to their pathophysiological interest, our results open possibilities of sperm selection prior to ICSI, which may allow for optimization of reproductive outcomes in heretofore unstudied patient populations.

An improved acetic acid-urea polyacrylamide electrophoresis method to evaluate bovine sperm protamines

The acetic acid-urea polyacrylamide gel electrophoresis system could separate very similar basic proteins on differences in size and effective charge. This system has been used for many years to analyse histones and their post-translational modifications and widely used in the study of mammal protamines. Two types of protamine have been described, the protamine 1 (P1) and the protamine 2 (P2) family members, which are synthetized by PRM1 and PRM2 genes. The ratio of P1 and P2 is important for predicting fertility in humans and mice. Therefore, the quantification of protamines is a fundamental step in order to establish the ratio between P1 and P2 in these species. In other mammals, studies linking sperm protamination and the protamine ratio with fertility are increasing. So, the use of an effective technique to separate and quantify protamines is important to study sperm P1/P2 ratio. Therefore, this article describes in detail a feasible and useful procedure to isolate bovine sperm protamines, to perform pre-electrophoresis with PEG solution and finally to carry out acid-urea polyacrylamide gel electrophoresis in reverse polarity. This technique allows a clear separation and efficient detection of bovine sperm protamines.

Liquid chromatography-tandem mass spectrometry reveals an active response to DNA damage in human spermatozoa

OBJECTIVE

To investigate how endogenously elevated DNA fragmentation alters the human sperm proteome, and whether this fragmentation contributes to genomic deletions.

DESIGN

Research study.

SETTING

Commercial fertility clinic.

PATIENT(S)

Men with low (0%-4%, n = 7) or high (≥16%, n = 6) sperm DNA fragmentation, as assessed by terminal deoxynucleotidyl transferase dUTP nick end labeling assay.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Global sperm proteome, single-nucleotide polymorphism genotyping array.

RESULT(S)

A total of 78 significantly differentially abundant proteins (30 decreased, 48 increased) were observed in control vs. high DNA damage samples. DNA damage resulted in robust proteomic responses, including markers of oxidative stress and apoptosis, DNA damage repair proteins, and transcription/translation and protein turnover machinery. Several key sperm functional proteins were significantly decreased in ejaculates with high DNA damage. We were unable to substantiate a link between increased DNA fragmentation and genomic deletions in human spermatozoa.

CONCLUSION(S)

Developing human spermatozoa initiate an active transcriptional response to endogenous DNA damage, which manifests as alterations in the sperm proteome.

Microbiological Evaluation and Sperm DNA Fragmentation in Semen Samples of Patients Undergoing Fertility Investigation

Fifteen percent of male infertility is associated with urogenital infections; several pathogens are able to alter the testicular and accessory glands' microenvironment, resulting in the impairment of biofunctional sperm parameters. The purpose of this study was to assess the influence of urogenital infections on the quality of 53 human semen samples through standard analysis, microbiological evaluation, and molecular characterization of sperm DNA damage. The results showed a significant correlation between infected status and semen volume, sperm concentration, and motility. Moreover, a high risk of fragmented sperm DNA was demonstrated in the altered semen samples. Urogenital infections are often asymptomatic and thus an in-depth evaluation of the seminal sample can allow for both the diagnosis and therapy of infections while providing more indicators for male infertility management.

Effects of liraglutide on sperm characteristics and fertilization potential following experimentally induced diabetes in mice

The current study was conducted to analyze the dose-dependent effects of liraglutide against the diabetes-induced detrimental impact on sperm parameters and fertilization potential. For this purpose, 42 adult male mice were randomly divided into control (with no intervention) and experimental groups. Next, the experimental group was subdivided into diabetic, 1.20 mg kg^-1 liraglutide-received diabetic, 1.80 mg kg^-1 liraglutide-received diabetic, 1.20 mg kg^-1 liraglutide-received non-diabetic and 1.80 mg kg^-1 liraglutide-received non-diabetic groups. All chemicals were administrated subcutaneously. Following 42 days, the animals were euthanized, and sperm samples were collected. The sperm count, motility, viability, DNA integrity, and maturity were analyzed and compared between groups. Moreover, the sperm fertilization potential was investigated by in vitro fertilization (IVF). For this purpose, the preimplantation embryo development at 2-cell, 4-cell, morula, and blastocyst stages was investigated and compared. Observations revealed that diabetes significantly diminished sperm count, motility, viability, chromatin condensation, and DNA integrity percentages versus a control group. On the other hand, 1.20 mg kg^-1 and 1.80 mg kg^-1 of liraglutide did not improve sperm motility and viability, while ameliorated sperm count and chromatin condensation and DNA integrity in diabetic animals. The diabetic animals represented diminished preimplantation embryo development, which was not altered in liraglutide-received groups. In conclusion, at least in administrated doses, liraglutide could not improve the sperm viability and motility and, via this mechanism, could not induce an appropriate/beneficial effect on IVF outcome.

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

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

In Silico Sperm Proteome Analysis to Investigate DNA Repair Mechanisms in Varicocele Patients

Varicocele, a condition associated with increased oxidative stress, negatively affects sperm DNA integrity and reduces pregnancy rates. However, the molecular mechanisms related to DNA integrity, damage, and repair in varicocele patients remain unclear. This study aimed to determine the role of DNA repair molecular mechanisms in varicocele-related infertility by combining an in silico proteomics approach with wet-laboratory techniques. Proteomics results previously generated from varicocele patients (n=50) and fertile controls (n=10) attending our Andrology Center were reanalyzed using bioinformatics tools, including the WEB-based Gene SeT AnaLysis Toolkit, Open Target Platform, and Ingenuity Pathway Analysis (IPA), to identify differentially expressed proteins (DEPs) involved in DNA repair. Subsequently, selected DEPs in spermatozoa were validated using western blotting in varicocele (n = 13) and fertile control (n = 5) samples. We identified 99 DEPs mainly involved in male reproductive system disease (n=66) and male infertility (n=47). IPA analysis identified five proteins [fatty acid synthase (FASN), myeloperoxidase (MPO), mitochondrial aconitate hydratase (ACO2), nucleoporin 93 (NUP93), and 26S proteasome non-ATPase regulatory subunit 14 (PSMD14)] associated with DNA repair deficiency, which showed altered expression in varicocele (P <0.03). We validated ACO2 downregulation (fold change=0.37, change%=-62.7%, P=0.0001) and FASN overexpression (fold change = 4.04, change %= 303.7%, P = 0.014) in men with varicocele compared to controls. This study combined a unique in silico approach with an in vitro validation of the molecular mechanisms that may be responsible for varicocele-associated infertility. We identified ACO2 and FASN as possible proteins involved in DNA repair, whose altered expression may contribute to DNA damage in varicocele pathophysiology.

The Sins of Our Forefathers: Paternal Impacts on De Novo Mutation Rate and Development

Spermatogonial stem cells (SSCs) are generally characterized by excellent DNA surveillance and repair, resulting in one of the lowest spontaneous mutation rates in the body. However, the barriers to mutagenesis can be overwhelmed under two sets of circumstances. First, replication errors may generate age-dependent mutations that provide the mutant cells with a selective advantage, leading to the clonal expansions responsible for dominant genetic diseases such as Apert syndrome and achondroplasia. The second mechanism centers on the vulnerability of the male germline to oxidative stress and the induction of oxidative DNA damage in spermatozoa. Defective repair of such oxidative damage in the fertilized oocyte results in the creation of mutations in the zygote that can influence the health and well-being of the offspring. A particular hot spot for such oxidative attack on chromosome 15 has been found to align with several mutations responsible for paternally mediated disease, including cancer, psychiatric disorders, and infertility.

Assessing the impact of semen quality on embryo development in an egg donation model

Objective

To investigate if any of the World Health Organization semen parameters and/or male age are associated with embryo development.

Design

Retrospective chart review between January 2008 and May 2015.

Setting

Academic fertility practice.

Patients

Anonymous egg donors aged ≤30 years.

Interventions

Chart review.

Main Outcome Measures

Sperm parameters were evaluated on a continuum and were dichotomized to determine if low values (strict morphology < 4%, concentration < 15 × 10⁶, low motility < 40%) or older age (>50 years) are associated with embryo morphology. Repeated linear regression measures to determine the associations and multivariate testing to determine independent effects for each predictor were performed.

Results

Three hundred eighty-four donors with 574 egg donation cycles were identified, and 205 subjects with 275 cycles were included in the final analysis. The mean donor age was 25.31 ± 2.81 years, with a mean antral follicle count of 28.09 ± 10.5. The mean male age was 43.25 ± 6.65 years. The mean World Health Organization semen parameters at fertilization were 55.8 × 10⁶ ± 44.3 × 10⁶/mL concentration, 44.8% ± 20.2% motility, and 6.9% ± 5.3% strict morphology. Neither male age nor sperm morphology was associated with embryo morphology. A low total motile count was significantly associated with a higher cell number in day-3 embryos and a 1.56-times higher chance of poor day-3 cell symmetry. There was no statistically significant difference in blastocyst formation, clinical pregnancy, or live-birth rates.

Conclusions

Although statistically significant, the effect of the low total motile count on day-3 cell number and cell symmetry are likely clinically insignificant. Male age, race, or poor sperm morphology were not associated with a poor cycle outcome or impaired embryo development. The use of intracytoplasmic sperm injection likely alleviates the negative effect of diminished semen quality on treatment outcome.

Recent advances in clinical diagnosis and treatment of male factor infertility

Infertility is a significant global health issue affecting around 8-12% of couples worldwide with male factor infertility accounting for a substantial proportion of these cases. Despite significant advances within the past few decades, an etiology for male factor infertility cannot be identified in up to 80% of patients and thus, this continues to be an area of active study. This review aims to provide an update on recent advances in the field of male infertility including semen analysis and at-home semen testing, genetics, DNA fragmentation, surgical approaches, and the rise of telemedicine in the era of COVID19.

The semen microbiome and its impact on sperm function and male fertility: A systematic review and meta-analysis

BACKGROUND

Male factor is attributable in up to 50% of cases of infertility. In vitro studies demonstrate that bacteria can negatively impact sperm function. The use of next-generation sequencing techniques has provided a better understanding of the human microbiome, and dysbiosis has been reported to impact health. Evidence regarding the impact of the semen microbiome on sperm function and fertility remains conflicting.

MATERIALS AND METHODS

A systematic search was conducted in accordance with the Preferred Reporting Items for Reviews and Meta-analysis (PRISMA) statement. The databases MEDLINE, OVID and PubMed were searched to identify English language studies related to the identification of bacteria in the semen of infertile and fertile men, between 1992 and 2019. Fifty-five observational studies were included, with 51 299 subjects. We included studies identifying bacteria using next-generation sequencing, culture or polymerase chain reaction.

RESULTS

The semen microbiome was rich and diverse in both fertile and infertile men. Three NGS studies reported clustering of the seminal microbiome with a predominant species. Lactobacillus and Prevotella were dominant in respective clusters. Lactobacillus was associated with improvements in semen parameters. Prevotella appeared to exert a negative effect on sperm quality. Bacteriospermia negatively impacted sperm concentration and progressive motility, and DNA fragmentation index (DFI; MD: 3.518, 95% CI: 0.907 to 6.129, P = .008). There was an increased prevalence of ureaplasma urealyticum in infertile men (OR: 2.25, 95% CI: 1.47-3.46). Ureaplasma urealyticum negatively impacted concentration and morphology. There was no difference in the prevalence of chlamydia trachomatis between fertile and infertile men and no significant impact on semen parameters. Enterococcus faecalis negatively impacted total motility, and Mycoplasma hominis negatively impacted concentration, PM and morphology.

DISCUSSION AND CONCLUSIONS

Ureaplasma urealyticum, Enterococcus faecalis, Mycoplasma hominis and Prevotella negatively impact semen parameters, whereas Lactobacillus appears to protect sperm quality. These findings may facilitate the development of novel therapies (eg probiotics), although the evidence regarding the impact of the seminal microbiome on fertility is inconclusive and further studies are needed to investigate this association.

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.

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

BACKGROUND

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

OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

DISCUSSION AND CONCLUSIONS

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

Developmental origins of transgenerational sperm histone retention following ancestral exposures

Numerous environmental toxicants have been shown to induce the epigenetic transgenerational inheritance of disease and phenotypic variation. Alterations in the germline epigenome are necessary to transmit transgenerational phenotypes. In previous studies, the pesticide DDT (dichlorodiphenyltrichloroethane) and the agricultural fungicide vinclozolin were shown to promote the transgenerational inheritance of sperm differential DNA methylation regions, non-coding RNAs and histone retention, which are termed epimutations. These epimutations are able to mediate this epigenetic inheritance of disease and phenotypic variation. The current study was designed to investigate the developmental origins of the transgenerational differential histone retention sites (called DHRs) during gametogenesis of the sperm. Vinclozolin and DDT were independently used to promote the epigenetic transgenerational inheritance of these DHRs. Male control lineage, DDT lineage and vinclozolin lineage F3 generation rats were used to isolate round spermatids, caput epididymal spermatozoa, and caudal sperm. The DHRs distinguishing the control versus DDT lineage or vinclozolin lineage samples were determined at these three developmental stages. DHRs and a reproducible core of histone H3 retention sites were observed using an H3 chromatin immunoprecipitation-sequencing (ChIP-Seq) analysis in each of the germ cell populations. The chromosomal locations and genomic features of the DHRs were analyzed. A cascade of epigenetic histone retention site alterations was found to be initiated in the round spermatids and then further modified during epididymal sperm maturation. Observations show that in addition to alterations in sperm DNA methylation and ncRNA expression previously identified, the induction of differential histone retention sites (DHRs) in the later stages of spermatogenesis also occurs. This novel component of epigenetic programming during spermatogenesis can be environmentally altered and transmitted to subsequent generations through epigenetic transgenerational inheritance.

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

Background

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

Results

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

Conclusion

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

X chromosome variants are associated with male fertility traits in two bovine populations

BACKGROUND

Twenty-five phenotypes were measured as indicators of bull fertility (1099 Brahman and 1719 Tropical Composite bulls). Measurements included sperm morphology, scrotal circumference, and sperm chromatin phenotypes such as DNA fragmentation and protamine deficiency. We estimated the heritability of these phenotypes and carried out genome-wide association studies (GWAS) within breed, using the bovine high-density chip, to detect quantitative trait loci (QTL).

RESULTS

Our analyses suggested that both sperm DNA fragmentation and sperm protamine deficiency are heritable (h2 from 0.10 to 0.22). To confirm these first estimates of heritability, further studies on sperm chromatin traits, with larger datasets are necessary. Our GWAS identified 12 QTL for bull fertility traits, based on at least five polymorphisms (P < 10-8) for each QTL. Five QTL were identified in Brahman and another seven in Tropical Composite bulls. Most of the significant polymorphisms detected in both breeds and nine of the 12 QTL were on chromosome X. The QTL were breed-specific, but for some traits, a closer inspection of the GWAS results revealed suggestive single nucleotide polymorphism (SNP) associations (P < 10-7) in both breeds. For example, the QTL for inhibin level in Braham could be relevant to Tropical Composites too (many polymorphisms reached P < 10-7 in the same region). The QTL for sperm midpiece morphological abnormalities on chromosome X (QTL peak at 4.92 Mb, P < 10-17) is an example of a breed-specific QTL, supported by 143 significant SNPs (P < 10-8) in Brahman, but absent in Tropical Composites. Our GWAS results add evidence to the mammalian specialization of the X chromosome, which during evolution has accumulated genes linked to spermatogenesis. Some of the polymorphisms on chromosome X were associated to more than one genetically correlated trait (correlations ranged from 0.33 to 0.51). Correlations and shared polymorphism associations support the hypothesis that these phenotypes share the same underlying cause, i.e. defective spermatogenesis.

CONCLUSIONS

Genetic improvement for bull fertility is possible through genomic selection, which is likely more accurate if the QTL on chromosome X are considered in the predictions. Polymorphisms associated with male fertility accumulate on this chromosome in cattle, as in humans and mice, suggesting its specialization.

Bacterial infection of the male reproductive system causing infertility

Bacterial infections play a disruptive and hidden role in male reproductive failure. Different kinds of bacteria are often able to interfere with reproductive function in both sexes and lead to infertility. In this study, to further evaluate the role of bacterial infections in male reproduction we provided an extensive overview of so far researches investigating the effects of bacterial infections on male fertility. We searched Medline, PubMed, Scopus and Google scholar databases to identify the potentially relevant studies on bacterial infections and their implications in male infertility. All the bacteria included in this article have negative effects on the male reproductive function; however, there is ample evidence to blame bacteria such as Escherichia coli, Chlamydia trachomatis, Ureaplasma, Mycoplasma and Staphylococcus aureus for reduced fertility and deterioration of sperm parameters. More studies are needed to clarify the molecular mechanisms by which different bacteria exert their detrimental effects on male reproductive system. Getting more insight into probable mechanisms, would significantly facilitate the production of new, advanced, and effective remedies in the future. In view of all evidence, we strongly suggest increasing awareness among people and considering screening programs for patients seeking fertility both to avoid transmission and to improve fertility outcomes among them.

Protamine-2 Deficiency Initiates a Reactive Oxygen Species (ROS)-Mediated Destruction Cascade during Epididymal Sperm Maturation in Mice

Protamines are the safeguards of the paternal sperm genome. They replace most of the histones during spermiogenesis, resulting in DNA hypercondensation, thereby protecting its genome from environmental noxa. Impaired protamination has been linked to male infertility in mice and humans in many studies. Apart from impaired DNA integrity, protamine-deficient human and murine sperm show multiple secondary effects, including decreased motility and aberrant head morphology. In this study, we use a Protamine-2 (Prm2)-deficient mouse model in combination with label-free quantitative proteomics to decipher the underlying molecular processes of these effects. We show that loss of the sperm's antioxidant capacity, indicated by downregulation of key proteins like Superoxide dismutase type 1 (SOD1) and Peroxiredoxin 5 (PRDX5), ultimately initiates an oxidative stress-mediated destruction cascade during epididymal sperm maturation. This is confirmed by an increased level of 8-OHdG in epididymal sperm, a biomarker for oxidative stress-mediated DNA damage. Prm2-deficient testicular sperm are not affected and initiate the proper development of blastocyst stage preimplantation embryos in vitro upon intracytoplasmic sperm injection (ICSI) into oocytes. Our results provide new insight into the role of Prm2 and its downstream molecular effects on sperm function and present an important contribution to the investigation of new treatment regimens for infertile men with impaired protamination.

Mitigating the Effects of Oxidative Sperm DNA Damage

Sperm DNA damage is correlated with reduced embryo development and increased miscarriage risk, reducing successful conception. Given its links with oxidative stress, antioxidants have been investigated as a potential treatment, yet results are conflicting. Importantly, individual antioxidants are not identical in composition, and some compounds may be more effective than others. We investigated the use of the polyphenol-rich, high-antioxidant-capacity fruit acai as a treatment for elevated sperm DNA fragmentation (>16%), measured by terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL). Following ≥ 74 days of treatment, we observed a significant decrease in sperm DNA fragmentation (-17.0% ± 2.5%) to 11.9 ± 1.7% (0-37%), with a 68.6% success rate (defined as post-treatment TUNEL < 16%). Post-treatment decreases in DNA fragmentation and success rates were not significantly impacted by low motility and/or concentration, or exceptionally high (> 25%) TUNEL. Treatment significantly reduced concentration in men with normal semen parameters, but 88% remained normal. Overall, successful treatment was not associated with age, semen parameters or TUNEL result at baseline. However, body mass index was significantly higher in nonresponders at baseline. This study provides evidence of a low-cost, effective treatment for elevated sperm DNA damage using acai.

Sperm DNA Integrity and Male Fertility in Farm Animals: A Review

The accurate prediction of male fertility is of major economic importance in the animal breeding industry. However, the results of conventional semen analysis do not always correlate with field fertility outcomes. There is evidence to indicate that mammalian fertilization and subsequent embryo development depend, in part, on the inherent integrity of the sperm DNA. Understanding the complex packaging of mammalian sperm chromatin and assessment of DNA integrity could potentially provide a benchmark in clinical infertility. In the era of assisted reproduction, especially when in-vitro fertilization or gamete intrafallopian transfer or intracytoplasmic sperm injection is used, assessment of sperm DNA integrity is important because spermatozoa are not subjected to the selection process occurring naturally in the female reproductive tract. Although sperm DNA integrity testing measures a significant biological parameter, its precise role in the infertility evaluation in farm animals remains unclear. In this review, the earlier findings on sperm DNA integrity in relation to male fertility are compiled and analyzed. Furthermore, the causes and consequences of sperm DNA damage are described, together with a review of advances in methods for detection of sperm DNA damage, and the prognostic value of sperm DNA quality on male fertility.

The Impact of Single- and Double-Strand DNA Breaks in Human Spermatozoa on Assisted Reproduction

Several cellular insults can result in sperm DNA fragmentation either on one or both DNA strands. Oxidative damage, premature interruption of the apoptotic process and defects in DNA compaction during spermatogenesis are the main mechanisms that cause DNA breaks in sperm. The two-tailed Comet assay is the only technique that can differentiate single- (SSBs) from double- (DSBs) strand DNA breaks. Increased levels of the phosphorylated isoform of the H2AX histone are directly correlated with DSBs and proposed as a molecular biomarker of DSBs. We have carried out a narrative review on the etiologies associated with SSBs and DSBs in sperm DNA, their association with reproductive outcomes and the mechanisms involved in their repair. Evidence suggests a stronger negative impact of DSBs on reproductive outcomes (fertilization, implantation, miscarriage, pregnancy, and live birth rates) than SSBs, which can be partially overcome by using intracytoplasmic sperm injection (ICSI). In sperm, SSBs are irreversible, whereas DSBs can be repaired by homologous recombination, non-homologous end joining (NHEJ) and alternative NHEJ pathways. Although few studies have been published, further research is warranted to provide a better understanding of the differential effects of sperm SSBs and DSBs on reproductive outcomes as well as the prognostic relevance of DNA breaks discrimination in clinical practice.

Diagnostic value of advanced semen analysis in evaluation of male infertility

Conventional semen analysis is the standard of care to initially evaluate the fertility status of a male patient. However, it has some limitations and among these are failure to correctly identify the aetiology underlying fertility problems, intra- and inter-observer variability and incomplete information about sperm function. Considering these drawbacks, advanced semen tests have been developed to assess male infertility, including sperm function tests, oxidative stress (OS) and sperm DNA fragmentation (SDF) tests. This review illustrates the commonly utilised sperm function techniques, along with the assays used to assess SDF and OS and their diagnostic value.

The effect of oxidative and reductive stress on semen parameters and functions of physiologically normal human spermatozoa

Both oxidative stress (OS) and reductive stress (RS) are the two extreme facets of redox imbalance that can have deleterious effects on sperm function. However, there is a lack of information on the physiological range of oxidation-reduction potential (ORP). The aim of this study was to investigate the effect of OS and RS on functions and associated molecular changes in normal spermatozoa in order to establish the physiological range of ORP. In the current study, total and progressive motility remained unchanged in spermatozoa exposed to ORP values 0.33 and 0.72 mV/10⁶ sperm/mL. However, a significant (P < 0.05) decline in total and progressive motility were observed at ORP values 1.48, 2.75, -11.24, -9.76 and -9.35 mV/10⁶ sperm/mL. Sperm vitality also decreased significantly (P < 0.0001) at 2.75, -11.24 and -9.76 mV/10⁶ sperm/mL. Spermatozoa exposed to ORP levels 2.75 and -11.24 mV/10⁶ sperm/mL showed a significant (P < 0.01) decrease in mitochondrial membrane potential. Intracellular reactive oxygen species (iROS) production increased (P < 0.05) in spermatozoa exposed to ORP levels of 1.48 and 2.75 mV/10⁶ sperm/mL, while iROS decreased (P < 0.05) at ORP levels -9.76 and -11.24 mV/10⁶ sperm/mL. No significant change in sperm DNA fragmentation was noted in sperm exposed to OS/RS and the values were below the reference range (<19.25%). Western blot analysis revealed decreased expression of CV-ATPA, CIII-UQCRC2 and CIV-MTCO1 proteins at 60 and 120 min (P < 0.05) in both OS and RS conditions. This is the first study to report physiological range of ORP (between -9.76 and 1.48 mV/10⁶ sperm/mL) and to elucidate the role of altered expression of oxidative phosphorylation (OXPHOS) complexes proteins in mediating detrimental effects of oxidative and reductive conditions on sperm functions. A decreased expression of OXPHOS proteins and associated mitochondrial dysfunction contributes to decreased sperm motility and vitality under oxidative and reductive stress.

Role of genetics and epigenetics in male infertility

Male infertility is a complex condition with a strong genetic and epigenetic background. This review discusses the importance of genetic and epigenetic factors in the pathophysiology of male infertility. The interplay between thousands of genes, the epigenetic control of gene expression, and environmental and lifestyle factors, which influence genetic and epigenetic variants, determines the resulting male infertility phenotype. Currently, karyotyping, Y-chromosome microdeletion screening and CFTR gene mutation tests are routinely performed to investigate a possible genetic aetiology in patients with azoospermia and severe oligozoospermia. However, current testing is limited in its ability to identify a variety of genetic and epigenetic conditions that might be implicated in both idiopathic and unexplained infertility. Several epimutations of imprinting genes and developmental genes have been postulated to be candidate markers for male infertility. As such, development of novel diagnostic panels is essential to change the current landscape with regard to prevention, diagnosis and management. Understanding the underlying genetic mechanisms related to the pathophysiology of male infertility, and the impact of environmental exposures and lifestyle factors on gene expression might aid clinicians in developing individualised treatment strategies.

Effects of cryopreservation on stallion sperm protamine messenger RNAs

Protamines substitute DNA-binding histones during late spermatogenesis in sperm nucleus. Stallion sperm contains all three variants of these arginine-rich and positively charged nuclear proteins (P1, P2 and P3). Two variants of protamine-2, that is P2 and P3, constitute approximately 15% of the entire protamine content. Also, the ratio of protamine-1 to protamine-2 varies among different mammalian species, and abnormal protamine ratios and protamine content are correlated with male infertility. In this study, changes in protamine mRNA abundance for all three protamines were investigated in stallion sperm during cryopreservation. Twelve ejaculates were collected from six sexually mature stallions. Sperm samples were divided into two parts for total mRNA extraction: one as fresh and the other as cryopreserved sample. Levels of three protamine transcripts were determined by real-time reverse transcriptase polymerase chain reaction. Results of relative expression showed that cryopreservation can significantly alter protamine transcripts: protamine 2 was downregulated, while protamine 3 was upregulated in cryopreserved samples relative to the control. Changes in protamine 1 were not significant after cryopreservation. This study is the first to evaluate changes in mRNA abundance of protamine genes in stallion sperm following cryopreservation. Such evaluations are important in finding transcriptomic markers for success in fertilization and assisted reproductive techniques.

Comparison of ART outcomes in men with altered mRNA protamine 1/protamine 2 ratio undergoing intracytoplasmic sperm injection with ejaculated and testicular spermatozoa

Assisted reproductive technologies involving the use of spermatozoa and eggs for in vitro fertilization (IVF) have come as the solution for many infertile couples to become parents. However, in some cases, the use of ejaculated spermatozoa delivers poor IVF performance. Some studies have suggested the use of testicular spermatozoa in severe male infertility cases, but no guidelines regarding their utilization are currently available. In the present study, we found the mRNA protamine 1/protamine 2 (P1/P2) ratio to be a valuable biomarker of poor sperm function that could be used as a diagnostic key for the identification of cases that would benefit from the use of testicular spermatozoa. A total of 23 couples undergoing egg donation cycles with at least one previous cycle failure were studied. All couples underwent two consecutive intracytoplasmic sperm injection (ICSI) cycles with either ejaculated or testicular spermatozoa (TESA). The sperm mRNA P1/P2 ratio, fertilization rate, blastocyst rate, and pregnancy and live birth rate were compared. Results showed improved ICSI and clinical outcomes in cycles with testicular spermatozoa in men with altered mRNA P1/P2 ratios. TESA cycles presented significantly higher rates of fertilization (mean ± standard deviation: 76.1% ± 15.1% vs 65.5% ± 18.8%), blastocyst formation (55.0% ± 20.3% vs 30.8% ± 23.8%), and good morphological quality blastocyst (28.9% ± 22.9% vs 13.5% ± 17.9%) and also improvements on pregnancy (60.9% vs 0%) and healthy birth rates (56.5% vs 0%) than EJACULATE cycles. The results described here suggest that in patients with previous IVF/ICSI failures and aberrant mRNA protamine ratios, the use of testicular spermatozoa may be a good alternative to improve clinical outcomes.

The concentration of testosterone, pituitary adenylate cyclase-activating polypeptide, and protamine 1 in the serum of male chicken following administration of epididymis and testicular extracts and their combination

Bakcground and Aim

Testis and epididymis are male reproductive organs that play an important role in spermatogenesis. These two organs are rich in the content of hormones and other molecules needed in the process of spermatogenesis which affect the quality of the spermatozoa. The objective of this study was to examine the effect of the administration of epididymis and testicular extracts and their combination on testosterone, pituitary adenylate cyclase-activating polypeptide (PACAP), and protamine 1 (PRM1) concentrations in the serum of male chicken.

Materials and Methods

Twenty male chickens (broiler strain Cp707), aged 3 weeks and weighing 800-1000 g, were randomly divided into four different groups including a control group (T0) = injected with 1 ml normal saline and treatment groups: T1 = injected with 1 ml epididymis extract, T2 = injected with 1 ml testicular extract, and T3 = injected with a combination of 1 ml epididymis + 1 ml testicular extract. The experiment was conducted for 13 days and at the end of the study (day 14), the chickens were sacrificed to obtain the serum. Furthermore, the concentrations of testosterone, PACAP, and PRM1 were then measured by using an enzyme-linked immunosorbent assay technique.

Results

The concentrations of PACAP and PRM1 did not show a significant difference between treatment groups (T1, T2, and T3) and control group (T0) (p>0.05). However, the concentration of testosterone showed a significantly higher difference in a group injected with a combination of 1 ml epididymis and 1 ml testicular extracts (T3) compared to the control group (T0) (p<0.05).

Conclusion

The administration of epididymis and testicular extracts and their combination did not affect the increase of PACAP and PRM1 concentration. However, a combination of these extracts significantly affects the increase of testosterone concentration in the serum of male chicken.