Seminal molecular markers as a non-invasive diagnostic tool for the evaluation of spermatogenesis in non-obstructive azoospermia

Oxidative Stress Biomarkers in Male Infertility: Established Methodologies and Future Perspectives

Male fertility can be affected by oxidative stress (OS), which occurs when an imbalance between the production of reactive oxygen species (ROS) and the body's ability to neutralize them arises. OS can damage cells and influence sperm production. High levels of lipid peroxidation have been linked to reduced sperm motility and decreased fertilization ability. This literature review discusses the most commonly used biomarkers to measure sperm damage caused by ROS, such as the high level of OS in seminal plasma as an indicator of imbalance in antioxidant activity. The investigated biomarkers include 8-hydroxy-2-deoxyguanosine acid (8-OHdG), a marker of DNA damage caused by ROS, and F2 isoprostanoids (8-isoprostanes) produced by lipid peroxidation. Furthermore, this review focuses on recent methodologies including the NGS polymorphisms and differentially expressed gene (DEG) analysis, as well as the epigenetic mechanisms linked to ROS during spermatogenesis along with new methodologies developed to evaluate OS biomarkers. Finally, this review addresses a valuable insight into the mechanisms of male infertility provided by these advances and how they have led to new treatment possibilities. Overall, the use of biomarkers to evaluate OS in male infertility has supplied innovative diagnostic and therapeutic approaches, enhancing our understanding of male infertility mechanisms.

Seminal plasma biomarkers for predicting successful sperm retrieval in patients with nonobstructive azoospermia: a narrative review of human studies

BACKGROUND

Non-obstructive azoospermia (NOA) is considered to be the most severe form of male infertility. Before the emergence of surgical testicular sperm extraction and assisted reproductive technology, NOA patients could hardly become biological fathers of their children. However, failure of the surgery could cause physical and psychological harm to patients such as testicular damage, pain, hopeless of fertility and additional cost. Therefore, predicting the successful sperm retrieval (SSR) is so important for NOA patients to make their choice whether to do the surgery or not. Because seminal plasma is secreted by the testes and accessory gonads, it can reflect the spermatogenic environment, making it a preferential choice for SSR valuation. The purpose of this paper is to summarize the available evidence and provide the reader with a broad overview of biomarkers in seminal plasma for SSR prediction.

RESULTS

A total of 15,390 studies were searched from PUBMED, EMBASE, CENTRAL and Web of Science, but only 6615 studies were evaluated after duplications were removed. The abstracts of 6513 articles were excluded because they were irrelevant to the topic. The full texts of 102 articles were obtained, with 21 of them being included in this review. The included studies range in quality from medium to high. In the included articles, surgical sperm extraction methods included conventional testicular sperm extraction (TESE) and microdissection testicular sperm extraction (micro-TESE). Currently, the biomarkers in seminal plasma used to predict SSR are primarily RNAs, metabolites, AMH, inhibin B, leptin, survivin, clusterin, LGALS3BP, ESX1, TEX101, TNP1, DAZ, PRM1 and PRM2.

CONCLUSION

The evidence does not conclusively indicate that AMH and INHB in seminal plasma are valuable to predict the SSR. It is worth noting that RNAs, metabolites and other biomarkers in seminal plasma have shown great potential in predicting SSR. However, existing evidence is insufficient to provide clinicians with adequate decision support, and more prospective, large sample size, and multicenter trials are urgently needed.

Evaluation of cell-free seminal mRNA for the diagnosis of obstruction as the cause of azoospermia in infertile men: A prospective cohort study

Differentiating obstructive (OA) from non-obstructive (NOA) azoospermia is clinically important in managing infertile men. Classically, the differentiation has been based on clinical, hormonal and histological analysis. Histological tests are invasive and may miss spermatogenic areas. Seminal fluid can serve as a medium to assess the status of spermatogenesis and presence or absence of certain markers can help diagnosing and differentiating azoospermia. We evaluated the role of cell-free seminal markers: DDX4, PRM1 and PRM2 in diagnosing and differentiating between OA and NOA and classifying their subtypes. We observed DDX4 was more sensitive for NOA compared with OA. Among various subtypes of NOA, DDX4 positivity was higher in patients with maturation arrest and hypospermatogenesis compared with Sertoli cell only syndrome. PRM1 and PRM2 had very low positivity rate for any meaningful comparison. Seminal cell-free markers can serve as non-invasive tests in diagnosing and differentiating etiologies of azoospermia but their validity needs to be proved in long-term trials with more refined molecular techniques.

Polymorphisms in the HSF2, LRRC6, MEIG1 and PTIP genes correlate with sperm motility in idiopathic infertility

The aim of this study was to investigate the association of 24 functionally important single nucleotide polymorphisms (SNPs) with male infertility. In this cross-sectional study, we genotyped 24 functionally important single nucleotide polymorphisms in 24 infertility candidate genes in 500 oligo-/astheno-/oligoastheno-/normo-zoospermic infertile men with idiopathic infertility. Sequenom iPlex gold assay was used for genotyping. Sperm count and motility were compared between prevalent genotypes at each test locus. We did not observe any significant difference in the average sperm count between the alternate genotypes for the loci in the KLK3, LRRC6, MEIG1, HSF2, ESR2 and PTIP genes. However, we observed a significant difference in sperm motility between the alternate genotypes for the loci in the LRRC6, MEIG1, HSF2 and PTIP genes. Polymorphisms in the LRRC6 (rs200321595), MEIG1 (rs150031795), HSF2 (rs143986686) and PTIP (rs61752013) genes show association with sperm motility.

Prediction Models for Successful Sperm Retrieval in Patients with Non-Obstructive Azoospermia Undergoing Microdissection Testicular Sperm Extraction: Is There Any Room for Further Studies?

Several prediction models for successful sperm retrieval (SSR) in patients with azoospermia due to spermatogenic dysfunction (also termed non-obstructive azoospermia—NOA) have been developed and published in the past years, however their resulting prediction accuracy has never been strong enough to translate their results in the clinical practice. This notwithstanding, the number of prediction models being proposed in this field is growing. We have reviewed the available evidence and found that, although patients with complete AZFc deletion or a history of cryptorchidism may have better probability of SSR compared to those with idiopathic NOA, no clinical or laboratory marker is able to determine whether a patient with NOA should or should not undergo microdissection testicular sperm extraction (mTESE) to have his testicular sperm retrieved. Further research is warranted to confirm the utility of evaluating the expression of noncoding RNAs in the seminal plasma, to individuate patients with NOA with higher probability of SSR.

Coding and Non-Coding RNAs, as Male Fertility and Infertility Biomarkers

Semen analysis is usually the first step in the assessment of male fertility. Although analyzes provide valuable information about male fertility, success of cytoplasmic sperm injection using this method is not predictable. In the recent years, studies have shown that sperm quality assessment helps clinicians predict male fertility status based on the expression of biomarkers. To write this article, a comprehensive study was conducted on several RNA transcripts by searching related words on medical information databases by 2018. According to the literature, spermatogenesis based disorders in male infertility have a significant relationship with the expression level of some RNA molecules (like DAZ and PRM1/PRM2 ratio) in semen and testicular tissue. Thus, they might be used as predictor biomarkersto evaluate success rate of testicular sperm extraction (TESE) procedure, but confirmation of this hypothesis requires more extensive research. By comparing the number of RNAs attributed to each fertility disorder in men, it is possible to trace the causes of disease or return fertility to some infertile patients by regulating the mentioned molecules. Further researches can provide a better understanding of the use of RNA expression profiles in the diagnosis and treatment of male infertility.

The RNA content of human sperm reflects prior events in spermatogenesis and potential post-fertilization effects

Transcriptome analyses using high-throughput methodologies allow a deeper understanding of biological functions in different cell types/tissues. The present study provides an RNA-seq profiling of human sperm mRNAs and lncRNAs (messenger and long non-coding RNAs) in a well-characterized population of fertile individuals. Sperm RNA was extracted from twelve ejaculate samples under strict quality controls. Poly(A)-transcripts were sequenced and aligned to the human genome. mRNAs and lncRNAs were classified according to their mean expression values (FPKM: Fragments Per Kilobase of transcript per Million mapped reads) and integrity. Gene Ontology analysis of the Expressed and Highly Expressed mRNAs showed an involvement in diverse reproduction processes, while the Ubiquitously Expressed and Highly Stable mRNAs were mainly involved in spermatogenesis. Transcription factor enrichment analyses revealed that the Highly Expressed and Ubiquitously Expressed sperm mRNAs were primarily regulated by zinc-fingers and spermatogenesis-related proteins. Regarding the Expressed lncRNAs, only one-third of their potential targets corresponded to Expressed mRNAs and were enriched in cell-cycle regulation processes. The remaining two-thirds were absent in sperm and were enriched in embryogenesis-related processes. A significant amount of post-testicular sperm mRNAs and lncRNAs was also detected. Even though our study is solely directed to the poly-A fraction of sperm transcripts, results indicate that both sperm mRNAs and lncRNAs constitute a footprint of previous spermatogenesis events and are configured to affect the first stages of embryo development.

Omics in Seminal Plasma: An Effective Strategy for Predicting Sperm Retrieval Outcome in Non-obstructive Azoospermia

Non-obstructive azoospermia (NOA) is a severe form of male factor infertility resulting from the impairment of sperm production. Surgical sperm retrieval followed by intracytoplasmic sperm injection (ICSI) is the only alternative for NOA patients to have their own genetic children. Nevertheless, due to an approximately 50% chance of success, harvesting sperm from these patients remains challenging. Thus, discovering noninvasive biomarkers, which are able to reliably predict the probability of sperm acquisition, not only can eliminate the risk of surgery but also can lower the costs of NOA diagnosis and treatment. Seminal plasma is the non-cellular and liquid portion of the ejaculate that consists of the secretions originating from testes and male accessory glands. In past years, a wide range of biomolecules including DNAs, RNAs, proteins, and metabolic intermediates have been identified by omics techniques in human seminal plasma. The current review aimed to briefly describe genomic, transcriptomic, proteomic, and metabolomic profiles of human seminal plasma in an attempt to introduce potential candidate noninvasive biomarkers for sperm-retrieval success in men with NOA.

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.

A clinical trial on the consistency of bilateral testicular tissue histopathology and Johnsen score: single side or bilateral side biopsy?

To evaluate and compare left and right testicular tissue histopathology and Johnsen score, and to investigate the necessity for bilateral testicular biopsy. We recruited180 patients with non-obstructiveazoospermia (NOA) on testicular biopsy who had undergonetesticular sperm aspiration (TESA). Pathological sections of testicular tissue were diagnosed by specially-assigned doctors, who evaluated pathological findings, determined the Johnsen score and confirmed for the presence or absence of sperm. Sperm positive rates for left and right testicular histopathology were 55.0% and 51.7% respectively, and the proportion of Johnsen scores≥8 for left and right testes were 53.3% and 50.0%, respectively. Cohen kappa values revealed that the identification of sperm in bilateral testicular samples was not consistent and was related to random effects; Optimized cut-off value for bilateral testicular volume was 11ml (Johnsen score ≥8), and optimized cut-off values of E₂ on left and right testes were 144.5pmol/L and 133.5 pmol/L (Johnsen score≤7). However, age, serum prolactin (PRL), follicle stimulating hormone (FSH), luteinizing hormone (LH) and total testosterone (TT) levels were not accurate predictors for the existence of testicular sperm. There was nostatistical significance between left and right testicular histopathology in terms of sperm positive rates or Johnsen score; the Johnsen score were caused entirely by random effects and a score from one side could not represent the other side. Therefore, we recommend that both testes need to undergo surgery when NOA patients undergo testicular biopsy or sperm retrieval.

Genetic evaluation of male infertility

Men with severe oligospermia (<5 million sperm/mL ejaculate fluid) or azoospermia should receive genetic testing to clarify etiology of male infertility prior to treatment. Categorization by obstructive azoospermia (OA) or non-obstructive azoospermia (NOA) is critical since genetic testing differs for the former with normal testicular function, testicular volume (~20 mL), and follicle-stimulating hormone (FSH) (1-8 IU/mL) when compared to the latter with small, soft testes and increased FSH. History and physician examination along with laboratory testing (following appropriate genetic counseling) is critical to accurate selection of genetic testing appropriate for azoospermia due to primary testicular failure as compared with congenital hypogonadotropic hypogonadism (HH). Genetic testing options include cystic fibrosis transmembrane conductance regulator (CFTR) testing for men with congenital absence of the vas, while karyotype, Y chromosome microdeletions (YCMD), and other specific genetic tests may be warranted depending on the clinical context of severe oligospermia or NOA. The results of genetic testing guide management options. The most recent techniques for genetic analysis, including sperm microRNA (miRNA) and epigenetics, are forming the foundation for future genetic diagnosis and therapeutic targets in male infertility.

Genetic study of Hormad1 and Hormad2 with non-obstructive azoospermia patients in the male Chinese population

PURPOSE

To evaluate the association of the Hormad1 and Hormad2 single nucleotide polymorphisms (SNPs) variants with non-obstructive azoospermia (NOA) in the Chinese population.

METHODS

In the present study, we assessed 10 single nucleotide polymorphisms (SNPs) of Hormad1 and Hormad2 using Sequenom iplex technology in 361 NOA cases and 368 normal controls from Chinese population.

RESULTS

We observed no statistical differences in the distribution of allele frequencies. Further genetic model analysis and haplotype analysis also showed no significant difference between the two groups. However, we found that genotype distribution of rs718772 of Hormad2 was significantly different between the larger testis group (average testis volume ≥10 ml) and the small testis group (average testis volume <10 ml) in the NOA patients (P = 0.035).

CONCLUSIONS

In conclusion, Hormad1 and Hormad2 might not be the susceptible genes for the non-obstructive azoospermia in our study population. However, rs718772 of Hormad2 variant might be associated with testis development in NOA patients.

Molecular analysis of testis biopsy and semen pellet as complementary methods with histopathological analysis of testis in non-obstructive azoospermia

PURPOSE

Non-obstructive azoospermia (NOA) is one the many causes of male infertility (10 %) resulting from testicular failure. Multiple testicular biopsies fail to find mature sperm in at least 50 % of cases Therefore; hunting for sensitive and specific biomarkers of spermatogenesis that could better determine the fertility status in NOA can lead to improved management of male infertility. Therefore, we evaluated sperm production through analyses of germ cell-specific transcripts (DAZ, TSPY1, SPTRX3 and SPTRX1) in semen and testicular biopsies of men with azoospermia.

METHODS

We collected semen (N=83) and testis biopsies (N=31) from men with non-obstructive azoospermia. We later extracted RNA and synthesized cDNA using washed semen precipitate and testicular tissues. We also performed semi-nested PCR with designed specific primers. Using H&E method, an expert pathologist performed the histopathological evaluation. Having categorized the patients into three groups based on histopathological results, we calculated the agreement between molecular results of semen and tissues with histopathological findings for each patient using Kappa statistical test.

RESULTS

Molecular findings of precipitated semen and testicular tissues were in disagreement with histopathological results in most cases. Molecular analysis of testis biopsies showed significant difference (Kappa coefficient=0.009, P value=0.894) with histopathological results; TSPY1, DAZ, SPTRX3 and SPTRX1 were respectively detected in 94 %, 94 %, 17.6 % and 52.9 % of men diagnosed with germ cell aplasia.

CONCLUSIONS

Molecular analysis of semen does not provide sufficient sensitivity and specificity to be used as a screening test at the present time, but it is a useful adjunct to histopathological methods in men with NOA. Spermatid/sperm specific transcripts indicated the possibility to find mature sperm following repeated multiple testicular sperm extraction (TESE) or microdisection TESE (mTESE).

Expression analysis of MND1/GAJ, SPATA22, GAPDHS and ACR genes in testicular biopsies from non-obstructive azoospermia (NOA) patients

BACKGROUND

High-throughput studies provide a wide spectrum of genes for use as predictive markers during testicular sperm extraction (TESE) in combination with ICSI. In this work, we used the specimens from testicular biopsies of men with non-obstructive azoospermia who underwent TESE to investigate the expression of spermatogenesis-related genes MND1, SPATA22, GAPDHS and ACR.

METHODS

Testicular biopsy specimens were subdivided into three groups: hypospermatogenesis (HS); maturation arrest (MA); and Sertoli cell-only syndrome (SCO). The levels of expression of the spermatogenesis-related genes MND1, SPATA22, GAPDHS and ACR in the testes were compared among these three groups using the reverse transcription polymerase chain reaction (RT-PCR) technique.

RESULTS

Analysis of the expression of spermatogenic genes in human testes with abnormal spermatogenesis showed different expression patterns in patients from different groups. Fertilization rate for studied set of patients was 66% and pregnancy rate 29%. For HS group fertilization rate was 72% and pregnancy rate 32%, while for MA group fertilization and pregnancy rates were 54% and 26%, respectively. Fertilization rates in relation to the studied genes were uniformly around 70%, pregnancy rates for ACR and GAPDHS genes were surprisingly low at 6% and 8% correspondingly.

CONCLUSIONS

Analysis of the expression of genes involved in spermatogenesis can be a fast additional test for the level of spermatogenesis in testicular samples.