Spermatozoa as biomarkers for the assessment of human male infertility and genotoxicity

Effects of the air pollution dynamics on semen quality and sperm DNA methylation in men living in urban industrial agglomeration

Human populations living in urban industrial regions of developed countries are exposed to high levels of environmental pollutants. The reproductive consequences of the exposure to air pollution can be monitored through semen analysis and molecular methods. In this study, we tested the possible impact of seasonal changes in the level of air pollution on the semen quality and sperm DNA methylation of 24 men living and working in the industrial agglomeration of Ostrava (Czech Republic). The study participants were healthy non-smokers. The study group was homogeneous regarding their profession, moderate alcohol consumption, no drug abuse and no additional exposure to chemical toxicants. We performed targeted methylation next generation sequencing (NGS) using Agilent SureSelect Human Methyl-Seq and Illumina NextSeq 500 platform to analyze semen samples collected repeatedly from the same men following the season of high (winter) and low (summer) air pollution exposure. We did not detect any adverse effects of the increased exposure on the semen quality; neither we found any difference in average sperm DNA methylation between the two sampling periods. Our search for differentially methylated CpG sites did not reveal any specific CpG methylation change. Our data indicate that the seasonal changes in the level of the air pollution probably do not have any substantial effect on sperm DNA methylation of men living in the highly polluted industrial agglomeration for a long period of time.

Correlations between elevated basal sperm DNA fragmentation and the clinical outcomes in women undergoing IUI

OBJECTIVE

This study aimed to explore the impact of the sperm DNA fragmentation index (DFI) on the clinical outcomes in women undergoing artificial insemination by husband intrauterine insemination (AIH-IUI).

METHODS

In this retrospective study, the value of sperm DFI was detected by sperm chromatin structure assay (SCSA) in a semen analysis collected before fertility treatment (basal DFI) in 1,500 IUI cycles at the infertility clinic of Northern Jiangsu People's Hospital Reproductive Medicine Center from Jan 2016 to April 2021. Receiver operating characteristic (ROC) curves were used to calculate the cut-off value for the clinical outcomes of IUI, including the biochemical pregnancy rate, clinical pregnancy rate, delivery rate, and live birth rate, and multivariate logistic regression was conducted to analyse the risk factors for clinical outcomes after IUI.

RESULT

In 1,500 IUI cycles, the results showed that there were no statistically significant differences between the normal DFI group and the abnormal DFI group in biochemical pregnancy rate (14.41% vs. 11.3%, P = 0.386), clinical pregnancy rate (12.9% vs. 10.5%, P = 0.433), delivery rate (11.0% vs. 8.9%, P = 0.456), live birth rate (10.9% vs. 8.9%, P = 0.484) or pregnancy loss rate (14.6% vs. 15.4%, P = 1.000).

CONCLUSION

Sperm DFI alone may have limited predictive power for IUI clinical outcomes.

In Silico Analysis of Sperm From Ejaculates with Different Semen Characteristics

Background:

Male infertility is associated with altered characteristics of the sperm within the ejaculate. It is possible to find molecular explanations for the observed phenotypes and their consequences. This study aimed to analyze, using a specialized software, a gene set of transcriptomic data from different types of ejaculates.

Methods:

Data from ejaculate samples categorized as normal, oligospermia, and teratozoospermia were obtained from Gene Expression Omnibus (GEO). After normalization, the data average for each sample category was calculated and analyzed independently using Ingenuity Pathway Analysis (IPA).

Results:

Five important canonical pathways are involved in normal and altered semen samples (Oligospermia and teratozoospermia) except sirtuin signaling and mitochondrial dysfunction pathways. The five most important biological processes are identified in all semen phenotypes, but the only difference is the genes connected with initiation of RNA transcription in oligospermic and asthenospermic samples.

Conclusion:

Surprisingly, different types of ejaculates share many pathways and biological processes; sperm proteomics as a new global approach gives clues for the development of strategies to explain the reason for observed phenotypes of ejaculated spermatozoa, their possible effect on fertility, and for implementing research strategies in the context of infertility diagnosis and treatment.

Differential sperm proteomic profiles according to pregnancy achievement in intracytoplasmic sperm injection cycles: a pilot study

PURPOSE

To describe the proteomic profiles in semen samples and define the differences in sperm proteomic profiles among samples that ultimately achieved pregnancy (P) via intracytoplasmic sperm injection (ICSI) in an oocyte donation program and those that were unsuccessful (NP).

METHODS

Prospective, analytical, observational nested case and control study evaluating the proteomic profile of spermatozoa from patients' ejaculates where pregnancies were (group pregnant (P), n= 4) or were not (group non-pregnant (NP), n=4) achieved after ICSI in an oocyte donation program aiming to standardize female factor. Proteins were separated and analyzed by means of SWATH-MS) and compared between P/NP groups to identify sperm biomarkers of fertility/infertility. Proteins are available via ProteomeXchange.

RESULTS

We identified and quantified 2228 proteins, with 37 significantly higher in the P group and 16 higher in NP. Enrichment analysis revealed that the increased proteins in P group sperm were related to motility, anaerobic metabolism, and protein biosynthesis functions, while the increased proteins in the NP group were involved in protein biosynthesis, protein folding, aerobic metabolism, and signal transduction, all of which are functions not previously described as influencing sperm success. Some proteins identified (e.g., SLC2A3, or CD81) are located in the cell membrane and thus may be employed to select spermatozoa by magnetic-activated cell sorting (MACS).

CONCLUSION(S)

This work revealed differences in the proteomic profiles of sperm samples successful in achieving pregnancy and those that were not, expanding our understanding of sperm function and infertility-related molecular markers, and enabling the future development of male fertility diagnostic tools and therapies.

A review on genotoxicity in connection to infertility and cancer

Genotoxicity has been identified as the main cause of infertility and a variety of cancers. The mechanisms affect the structure, quality of the information or the segregation of DNA and are not inherently correlated with mutagenicity. The concept of genotoxicity, the chemical classes that cause genetic damage and the associated mechanisms of action are discussed here. Hazardous effects of pharmaceuticals, cosmetics, agrochemicals, industrial compounds, food additives, natural toxins and nanomaterials are, in large part, identified by genotoxicity and mutagenicity tests. These are critical and early steps in industrial and regulatory health assessment. Though several in vitro experiments are commonly used and approval by regulatory agencies for commercial licensing of drugs, their accuracy in human predictions for genotoxic and mutagenic effects is frequently questioned. Treatment of real and functional genetic toxicity problems depends in detail on the knowledge of mechanisms of DNA damage in the molecular, subcellular, cellular and tissue or organ system levels. Current strategies for risk assessment of human health need revisions to achieve robust and reliable results for optimizing their effectiveness. Additionally, computerized methods, neo-biomarkers leveraging '-omics' approaches, all of which can provide a convincing genotoxicity evaluation to reduce infertility and cancer risk.

Sperm microRNA pairs: new perspectives in the search for male fertility biomarkers

OBJECTIVE

To identify candidates of fertility biomarkers among pairs of human sperm microRNAs.

DESIGN

Expression data of 736 sperm microRNAs from fertile and infertile individuals characterized in previous published studies by means of TaqMan quantitative polymerase chain reaction (PCR) were reexamined. A set of microRNA pairs with the best biomarker potential were selected and validated by means of quantitative real-time (qRT) PCR in an independent cohort.

SETTING

University laboratory.

PATIENT(S)

Semen samples were obtained from fertile (n = 10) and infertile (asthenozoospermia, n = 10; teratozoospermia, n = 10; oligozoospermia, n = 10; unexplained male infertility [UMI], n = 8) individuals. The validation cohort included 9 fertile donors and 14 infertile patients with different seminal alterations.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Spearman test was used to select microRNA pairs with a correlated expression in fertile individuals and a noncorrelated expression in each infertile group. The biomarker potential of these pairs was determined with the use of receiver operating characteristic curves. The differential relative expression of each pair in fertile and infertile populations was verified (Mann-Whitney test). Those pairs with best results were validated by qRT-PCR.

RESULT(S)

Forty-eight pairs showed significant correlations in the fertile group. The pairs that were uncorrelated in the infertile populations and displayed the best biomarker potential were hsa-miR-942-5p/hsa-miR-1208 (asthenozoospermia), hsa-miR-296-5p/hsa-miR-328-3p (teratozoospermia), hsa-miR-139-5p/hsa-miR-1260a (oligozoospermia), and hsa-miR-34b-3p/hsa-miR-93-3p (UMI). The hsa-miR-942-5p/hsa-miR-1208 pair showed the greatest potential for detecting seminal alterations in the validation cohort (85.71% true positives).

CONCLUSION(S)

The pairs hsa-miR-942-5p/hsa-miR-1208 and hsa-miR-34b-3p/hsa-miR-93-3p have the potential to become new molecular biomarkers that could help to diagnose male infertility, especially in cases of UMI or when seminal parameters are close to the threshold values.

The role of flavonoid antioxidant, morin in improving procarbazine-induced oxidative stress on testicular function in rat

BACKGROUND

Procarbazine (PCZ) is an effective chemotherapeutic drug used in the treatment of lymphoma; however, oxidative stress-mediated testicular toxicity is a major side effect. Recently, therapeutic intervention using flavonoids against oxidative stress-related pathologies is gaining more attention. Morin (MOR) is a natural flavonoid with proven antioxidant activity. This study was designed therefore to evaluate the potential role of MOR in ameliorating PCZ-induced testicular oxidative stress and altered sperm quality in rat model.

METHODS

A total of 24 male Wistar rats (170-180 g) were randomly assigned into 4 treatment groups: I, control; II, PCZ (2 mg/kg b.w.); III, PCZ (2 mg/kg b.w.) + MOR (100 mg/kg b.w.) simultaneously administered and IV, MOR (100 mg/kg b.w.), and all treatments lasted 14 days.

RESULTS

PCZ treatment displayed significant reduction in sperm number, sperm motility, percentage normal sperm cells, and daily sperm production rate. Meanwhile the activities of testicular enzymes: gamma-glutamyl transferase, acid phosphatase, and lactate dehydrogenase were significantly altered in the PCZ group compared to control. Furthermore, PCZ caused a significant reduction in levels of glutathione and ascorbic acid as well as activities superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase in the testes of PCZ-treated rats. A significant increase in testicular malondialdehyde level was also observed in the PCZ group. MOR treatment, however, significantly restored the altered sperm parameters and biochemical markers in the testis.

CONCLUSIONS

Our data suggest that MOR administration protected against PCZ-induced testicular and spermatotoxicity in rat, by improving testicular antioxidant system.

Spermatozoa from normozoospermic fertile and infertile individuals convey a distinct miRNA cargo

Deciphering the underlying causes of idiopathic male infertility is one of the main challenges in reproductive medicine. This is especially relevant in infertile patients displaying normal seminal parameters and no urogenital or genetic abnormalities. In these cases, the search for additional sperm biomarkers is of high interest. This study was aimed to determine the implications of the sperm miRNA expression profiles in the reproductive capacity of normozoospermic infertile individuals. The expression level of 736 miRNAs was evaluated in spermatozoa from eight normozoospermic infertile males using TaqMan^® qRT-PCR. Results were contrasted with data from 10 control normozoospermic fertile individuals analyzed under the same conditions. Clustering analysis of miRNA expression data separated the individuals according to their fertility condition (fertile and infertile). Fifty-seven miRNAs were differentially expressed (DE-miRNAs) between populations; 20 of them was regulated by a host gene promoter that in three cases comprised genes involved in fertility. The predicted targets of the DE-miRNAs (n = 8,606) unveiled a significant enrichment of biological processes related to embryonic morphogenesis and chromatin modification. Normozoospermic infertile individuals exhibit a specific sperm miRNA expression profile clearly differentiated from normozoospermic fertile individuals. This miRNA cargo has potential implications in the individuals' reproductive competence.

Ficoll-400 density gradient method as an effective sperm preparation technique for assisted reproductive techniques

BACKGROUND:

Infertility being a burning issue, the male itself contributes about 40% as a cause, as evident by statistical data. However, Assisted Reproductive Technology (ART) has emerged as a powerful tool in the management of infertility. Sperm preparation techniques govern the selection procedure to separate functional spermatozoa which can then be used in IUI, IVF, and ART and for cryopreservation.

AIM:

The present study was aimed at evaluation of sperm preparation techniques for reliability, performance and to determine the most effective, feasible and economical technique.

MATERIALS AND METHODS:

The subjects under study includes males with normal proven fertility (n=40) and the males with unexplained infertility (n=40). Four sperm separation techniques, viz., Swim-up, Swim-down, Sucrose and Ficoll-400 density gradient techniques were evaluated for their efficacy in separation of good quality fraction of spermatozoa. Sperm viability, morphology and maturation status of spermatozoa were taken as evaluation parameters following the standard methods (WHO 2010).

STATISTICAL ANALYSIS:

Data was analyzed using student's t-test and the four selected techniques were compared with the normal semen samples for scoring the efficiency of the techniques.

RESULTS AND DISCUSSION:

Out of the several techniques used, Ficoll-400 was found to be more efficient method for separation of spermatozoa. The percentage of change in each parameter was calculated and taken as the index for recovery of potent sperm from the original sperm. Ficoll-400 density gradient yielded higher percentage of live, mature, morphologically normal spermatozoa in an isolated fraction as compared to other three techniques.

CONCLUSION:

It was observed that a combination of Ficoll-400 gradient separation with Swim-up technique could give quality spermatozoa which in-turn would directly have an impact on the success of IVF and other ART techniques.

Sperm mRNAs and microRNAs as candidate markers for the impact of toxicants on human spermatogenesis: an application to tobacco smoking

Spermatozoa contain a complex population of RNAs including messenger RNAs (mRNAs) and small RNAs such as microRNAs (miRNA). It has been reported that these RNAs can be used to understand the mechanisms by which toxicological exposure affects spermatogenesis. The aim of our study was to compare mRNA and miRNA profiles in spermatozoa from eight smokers and eight non-smokers, and search for potential relationships between mRNA and miRNA variation. All men were selected based on their answers to a standard toxic exposure questionnaire, and sperm parameters. Using mRNA and miRNA microarrays, we showed that mRNAs from 15 genes were differentially represented between smokers and non-smokers (p<0.01): five had higher levels and 10 lower levels in the smokers. For the microRNAs, 23 were differentially represented: 16 were higher and seven lower in the smokers (0.004≤p<0.01). Quantitative RT-PCR confirmed the lower levels in smokers compared to non-smokers for hsa-miR-296-5p, hsa-miR-3940, and hsa-miR-520d-3p. Moreover, we observed an inverse relationship between the levels of microRNAs and six potential target mRNAs (B3GAT3, HNRNPL, OASL, ODZ3, CNGB1, and PKD2). Our results indicate that alterations in the level of a small number of microRNAs in response to smoking may contribute to changes in mRNA expression in smokers. We conclude that large-scale analysis of spermatozoa RNAs can be used to help understand the mechanisms by which human spermatogenesis responds to toxic substances including those in tobacco smoke.

RNA: a possible contributor to the 'missing heritability'

A number of human pathologies have a transmission pattern that does not obey Mendelian segregation rules. This type of heredity is defined as non-Mendelian and is based on mechanisms of transgenerational epigenetic inheritance. Comprehensive information on the molecular mechanisms of it is still lacking. However, recent evidence from distantly related species including Caenorhabditis elegans, Drosophila, and mouse, points towards a role for non-coding RNA molecules in such a pattern of inheritance. While it would be too hasty to conclude that RNA molecules are at work in the transgenerational non-genetic inheritance of human pathologies, a growing number of studies seem to strongly support such a speculation.

What should it take to describe a substance or product as 'sperm-safe'

BACKGROUND

Male reproductive potential continues to be adversely affected by many environmental, industrial and pharmaceutical toxins. Pre-emptive testing for reproductive toxicological (side-)effects remains limited, or even non-existent. Many products that come into direct contact with spermatozoa lack adequate testing for the absence of adverse effects, and numerous products that are intended for exposure to spermatozoa have only a general assumption of safety based on the absence of evidence of actual harm. Such assumptions can have unfortunate adverse impacts on at-risk individuals (e.g. couples who are trying to conceive), illustrating a clear need for appropriate up-front testing to establish actual 'sperm safety'.

METHODS

After compiling a list of general areas within the review's scope, relevant literature and other information was obtained from the authors' personal professional libraries and archives, and supplemented as necessary using PubMed and Google searches. Review by co-authors identified and eliminated errors of omission or bias.

RESULTS

This review provides an overview of the broad range of substances, materials and products that can affect male fertility, especially through sperm fertilizing ability, along with a discussion of practical methods and bioassays for their evaluation. It is concluded that products can only be claimed to be 'sperm-safe' after performing objective, properly designed experimental studies; extrapolation from supposed predicate products or other assumptions cannot be trusted.

CONCLUSIONS

We call for adopting the precautionary principle, especially when exposure to a product might affect not only a couple's fertility potential but also the health of resulting offspring and perhaps future generations.

The presence, role and clinical use of spermatozoal RNAs

BACKGROUND Spermatozoa are highly differentiated, transcriptionally inert cells characterized by a compact nucleus with minimal cytoplasm. Nevertheless they contain a suite of unique RNAs that are delivered to oocyte upon fertilization. They are likely integrated as part of many different processes including genome recognition, consolidation-confrontation, early embryonic development and epigenetic transgenerational inherence. Spermatozoal RNAs also provide a window into the developmental history of each sperm thereby providing biomarkers of fertility and pregnancy outcome which are being intensely studied. METHODS Literature searches were performed to review the majority of spermatozoal RNA studies that described potential functions and clinical applications with emphasis on Next-Generation Sequencing. Human, mouse, bovine and stallion were compared as their distribution and composition of spermatozoal RNAs, using these techniques, have been described. RESULTS Comparisons highlighted the complexity of the population of spermatozoal RNAs that comprises rRNA, mRNA and both large and small non-coding RNAs. RNA-seq analysis has revealed that only a fraction of the larger RNAs retain their structure. While rRNAs are the most abundant and are highly fragmented, ensuring a translationally quiescent state, other RNAs including some mRNAs retain their functional potential, thereby increasing the opportunity for regulatory interactions. Abundant small non-coding RNAs retained in spermatozoa include miRNAs and piRNAs. Some, like miR-34c are essential to the early embryo development required for the first cellular division. Others like the piRNAs are likely part of the genomic dance of confrontation and consolidation. Other non-coding spermatozoal RNAs include transposable elements, annotated lnc-RNAs, intronic retained elements, exonic elements, chromatin-associated RNAs, small-nuclear ILF3/NF30 associated RNAs, quiescent RNAs, mse-tRNAs and YRNAs. Some non-coding RNAs are known to act as epigenetic modifiers, inducing histone modifications and DNA methylation, perhaps playing a role in transgenerational epigenetic inherence. Transcript profiling holds considerable potential for the discovery of fertility biomarkers for both agriculture and human medicine. Comparing the differential RNA profiles of infertile and fertile individuals as well as assessing species similarities, should resolve the regulatory pathways contributing to male factor infertility. CONCLUSIONS Dad delivers a complex population of RNAs to the oocyte at fertilization that likely influences fertilization, embryo development, the phenotype of the offspring and possibly future generations. Development is continuing on the use of spermatozoal RNA profiles as phenotypic markers of male factor status for use as clinical diagnostics of the father's contribution to the birth of a healthy child.

The use of genomics, proteomics, and metabolomics in identifying biomarkers of male infertility

Although male factors account for approximately 50% of all infertility, the mechanisms underlying their origin are unknown. Currently, clinicians rely primarily on semen analyses to predict male reproductive potential and chart treatment success. Even when invasive procedures are performed, the causes of male factor infertility frequently remain elusive. Recently, the advent of new technologies has spurred the search for novel male infertility biomarkers, and the detection of genes, proteins, or metabolites unique to the infertile male holds much promise. The concept that a cost-effective, noninvasive, and accurate set of biomarkers can be identified to diagnose male factor infertility is tantalizing. This review focuses on the various methodologies used in the discovery of novel biomarkers along with their findings. Specific attention is paid to recent advances in the fields of genetics, proteomics, and metabolomics.

ICSI improves fertilization in isolated teratozoospermic men: a study with strictly controlled external factors and WHO-5 standard

A clear clinical management pathway (conventional in vitro fertilization, IVF or intracytoplasmic sperm injection, ICSI) for treating patients with teratozoospermia is lacking. Here we conducted a retrospective study of fertility indices in 2,178 IVF/ICSI cycles in order to reevaluate clinical management of couples with isolated teratozoospermia (< 4% morphologically normal sperms and normal sperm concentration and motility with the standard of WHO-5).We strictly controlled external factors that could affect oocyte quality or endometrial receptivity to minimize the impact of confounders. Fertilization, total fertilization failure, embryo quality, blastocyst formation rate, and pregnancy rate were studied. Retrospectively, in conventional IVF cycles a significantly lower fertilization rate and higher total fertilization failure rate were observed in couples with isolated teratozoospermia as compared to couples with a normal semen profile. Furthermore, when ICSI was used to treat these teratozoospermic couples, improvement in fertilization was noted. However, the embryo quality, blastocyst formation rate, and pregnancy of couples with isolated teratozoospermia were not enhanced by ICSI. Multiple variable analysis showed that many factors including percentage of morphologically normal sperm are statistically correlated with fertilization rate and total fertilization failure in conventional IVF cycles. In addition the insemination method was correlated with fertilization rate in cases with isolated teratozoospermia. Further studies are warranted to compare outcomes of conventional IVF and ICSI in cases of isolated teratozoospermia, where less than 5 oocytes are retrieved.

Sperm mRNA transcripts are indicators of sub-chronic low dose testicular injury in the Fischer 344 rat

Current human reproductive risk assessment methods rely on semen and serum hormone analyses, which are not easily comparable to the histopathological endpoints and mating studies used in animal testing. Because of these limitations, there is a need to develop universal evaluations that reliably reflect male reproductive function. We hypothesized that toxicant-induced testicular injury can be detected in sperm using mRNA transcripts as indicators of insult. To test this, we exposed adult male Fischer 344 rats to low doses of model testicular toxicants and classically characterized the testicular injury while simultaneously evaluating sperm mRNA transcripts from the same animals. Overall, this study aimed to: 1) identify sperm transcripts altered after exposure to the model testicular toxicant, 2,5-hexanedione (HD) using microarrays; 2) expand on the HD-induced transcript changes in a comprehensive time course experiment using qRT-PCR arrays; and 3) test these injury indicators after exposure to another model testicular toxicant, carbendazim (CBZ). Microarray analysis of HD-treated adult Fischer 344 rats identified 128 altered sperm mRNA transcripts when compared to control using linear models of microarray analysis (q<0.05). All transcript alterations disappeared after 3 months of post-exposure recovery. In the time course experiment, time-dependent alterations were observed for 12 candidate transcripts selected from the microarray data based upon fold change and biological relevance, and 8 of these transcripts remained significantly altered after the 3-month recovery period (p<0.05). In the last experiment, 8 candidate transcripts changed after exposure to CBZ (p<0.05). The two testicular toxicants produced distinct molecular signatures with only 4 overlapping transcripts between them, each occurring in opposite directions. Overall, these results suggest that sperm mRNA transcripts are indicators of low dose toxicant-induced testicular injury in the rat.