Comparative proteomic analysis coupled with conventional protein assay as a strategy to identify predictors of successful testicular sperm extraction in patients with non-obstructive azoospermia

Predictors of Successful Testicular Sperm Extraction: A New Era for Men with Non-Obstructive Azoospermia

Background/Objectives: Non-obstructive azoospermia (NOA) is a severe form of male infertility characterized by the absence of sperm in the ejaculate due to impaired spermatogenesis. Testicular sperm extraction (TESE) combined with intracytoplasmic sperm injection is the primary treatment, but success rates are unpredictable, causing significant emotional and financial burdens. Traditional clinical and hormonal predictors have shown inconsistent reliability. This review aims to evaluate current and emerging non-invasive preoperative predictors of successful sperm retrieval in men with NOA, highlighting promising biomarkers and their potential clinical applications. Methods: A comprehensive literature review was conducted, examining studies on clinical and hormonal factors, imaging techniques, molecular biology biomarkers, and genetic testing related to TESE outcomes in NOA patients. The potential role of artificial intelligence and machine learning in enhancing predictive models was also explored. Results: Traditional predictors such as patient age, body mass index, infertility duration, testicular volume, and serum hormone levels (follicle-stimulating hormone, luteinizing hormone, inhibin B) have limited predictive value for TESE success. Emerging non-invasive biomarkers-including anti-Müllerian hormone levels, inhibin B to anti-Müllerian hormone ratio, specific microRNAs, long non-coding RNAs, circular RNAs, and germ-cell-specific proteins like TEX101-show promise in predicting successful sperm retrieval. Advanced imaging techniques like high-frequency ultrasound and functional magnetic resonance imaging offer potential but require further validation. Integrating molecular biomarkers with artificial intelligence and machine learning algorithms may enhance predictive accuracy. Conclusions: Predicting TESE outcomes in men with NOA remains challenging using conventional clinical and hormonal parameters. Emerging non-invasive biomarkers offer significant potential to improve predictive models but require validation through large-scale studies. Incorporating artificial intelligence and machine learning could further refine predictive accuracy, aiding clinical decision-making and improving patient counseling and treatment strategies in NOA.

Evaluation of PGK2 and ACR proteins in seminal plasma: suggestion of potential new biomarkers for prediction of sperm retrieval in non-obstructive azoospermia patients

This study aimed to assess the role of testis-specific proteins, PGK2 and ACR, in the prediction of sperm retrieval results by microdissection testicular sperm extraction (micro-TESE) in men with non-obstructive azoospermia (NOA). This was a case-control study including 48 semen samples of NOA patients undergoing the micro-TESE procedure, 15 semen samples from normozoospermic men as the positive control, and 12 semen samples from obstructive azoospermia/post-vasectomy (OA/PV) as negative controls. We investigated the levels of PGK2 and ACR proteins by ELISA tests in seminal plasma samples. The ELISA results revealed a significantly higher concentration of PGK2 and ACR in the NOA patients with successful sperm retrieval (NOA+) in comparison to NOA patients with failed sperm retrieval (NOA-) group (p = 0.0001 in both cases). For the first time, the data from this study suggests that a seminal PGK2 concentration of 136.3 pg/ml and ACR concentration of 21.75 mIU/ml can be used as cut-off values for the prediction of micro-TESE outcomes in NOA patients. These findings may be useful to avoid unnecessary micro-TESE operations. Overall, the seminal levels of the PGK2 and ACR proteins may be useful in predicting sperm retrieval success by micro-TESE in NOA patients.

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.

Transfer of Galectin-3-Binding Protein via Epididymal Extracellular Vesicles Promotes Sperm Fertilizing Ability and Developmental Potential in the Domestic Cat Model

Key proteins transferred by epididymal extracellular vesicles (EVs) to the transiting sperm cells contribute to their centrosomal maturation and developmental potential. Although not reported in sperm cells yet, galectin-3-binding protein (LGALS3BP) is known to regulate centrosomal functions in somatic cells. Using the domestic cat model, the objectives of this study were to (1) detect the presence and characterize the transfer of LGALS3BP via EVs between the epididymis and the maturing sperm cells and (2) demonstrate the impact of LGALS3BP transfer on sperm fertilizing ability and developmental potential. Testicular tissues, epididymides, EVs, and spermatozoa were isolated from adult individuals. For the first time, this protein was detected in EVs secreted by the epididymal epithelium. The percentage of spermatozoa with LGALS3BP in the centrosome region increased as cells progressively incorporated EVs during the epididymal transit. When LGALS3BP was inhibited during in vitro fertilization with mature sperm cells, less fertilized oocytes and slower first cell cycles were observed. When the protein was inhibited in epididymal EVs prior to incubation with sperm cells, poor fertilization success further demonstrated the role of EVs in the transfer of LGALS3BP to the spermatozoa. The key roles of this protein could lead to new approaches to enhance or control fertility in clinical settings.

Protein markers of spermatogenesis and their potential use in the management of azoospermia

INTRODUCTION

Azoospermia, absence of sperm in the ejaculate is classified as obstructive (OA) and non-obstructive azoospermia (NOA). In OA, sperm are produced, but due to physical obstruction in the male reproductive tract, they are not released in the ejaculate. NOA, on the other hand, is defined as the absence of sperm in the ejaculate due to testicular dysfunction. In NOA, spermatogenesis is frequently preserved in specific sites, and proteomics studies have been employed in order to identify men with preserved spermatogenesis.

AREAS COVERED

Differential protein expression in patients with male infertility is an indicator of impaired spermatogenesis. Here, we reviewed proteins with a potential role as biomarkers of spermatogenesis that could help in the management of non-obstructive and obstructive azoospermia. The following keywords were used for bibliographic research: seminal plasma, proteomics, male infertility, nonobstructive, obstructive, azoospermia, oligospermia.

EXPERT OPINION

Biopsy is an invasive and potentially harmful technique for detecting spermatogenesis in men with OA and NOA. Seminal plasma proteins are highly promising as biomarkers for spermatogenesis. Current literature presents a number of potential candidate biomarkers for determining preserved spermatogenesis.

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.

Non-obstructive azoospermia: current and future perspectives

Infertility affects 1 in 6 couples, and male factor infertility has been implicated as a cause in 50% of cases. Azoospermia is defined as the absence of spermatozoa in the ejaculate and is considered the most extreme form of male factor infertility. Historically, these men were considered sterile but, with the advent of testicular sperm extraction and assisted reproductive technologies, men with azoospermia are able to biologically father their own children. Non-obstructive azoospermia (NOA) occurs when there is an impairment to spermatogenesis. This review describes the contemporary management of NOA and discusses the role of hormone stimulation therapy, surgical and embryological factors, and novel technologies such as proteomics, genomics, and artificial intelligence systems in the diagnosis and treatment of men with NOA. Moreover, we highlight that men with NOA represent a vulnerable population with an increased risk of developing cancer and cardiovascular comorbodities.

Seminal Plasma Proteomic Biomarkers of Oxidative Stress

The prevalence of idiopathic male infertility is high, up to 75% of patients with abnormal sperm parameters. Hence, the research of its causes is mandatory. Oxidative stress (OS) can be responsible for male infertility in 30–80% of cases. In recent years, seminal plasma (SP) proteomics has developed as a useful tool to provide biomarkers of specific diseases. This systematic review aims to collect the available evidence on the changes of SP proteome in patients exposed to OS to provide possible SP biomarkers of sperm OS. To accomplish this, the following keyterms “seminal fluid proteome”, “seminal plasma proteome”, “oxidative stress”, and “sperm oxidative stress” were used and 137 records were found. Among these, 17 were finally included. Nine proteins involved with OS were found overexpressed in patients with OS. Twenty-three proteins were found differentially expressed in patients with clinical conditions associated with OS, such as varicocele, male accessory gland infection/inflammation, cigarette smoke, and obesity. These proteins do not seem to overlap among the clinical conditions taken into account. We speculate that specific SP proteins may mediate OS in different clinical conditions. Altogether, these results suggest that proteomics could help to better understand some of the molecular mechanisms involved in the pathogenesis of infertility. However, further studies are needed to identify potential biomarkers of male infertility with valuable clinical significance.

Predictive model to estimate the chances of successful sperm retrieval by testicular sperm aspiration in patients with nonobstructive azoospermia

OBJECTIVE

To explore predictors of successful sperm retrieval (SR) and to identify potentially suitable candidates for testicular sperm aspiration (TESA), a more straightforward, less traumatic, and less costly procedure than open surgical SR methods.

DESIGN

Retrospective chart review.

SETTING

Academic tertiary medical center.

PATIENTS

A total of 297 patients with nonobstructive azoospermia.

INTERVENTIONS

All patients underwent full clinical evaluation before undergoing a staged SR procedure, starting with TESA and proceeding to microsurgical testicular sperm extraction (microTESE). Predictors of positive SR with TESA were selected using the least absolute shrinkage and selection operator (LASSO) regression analysis using k-fold cross-validation. The obtained regression coefficients were used to create a predictive model, and a receiver operating characteristic (ROC) curve was obtained to express its predictive ability. Cut-off values for each significant predictor were also identified using ROC analysis.

MAIN OUTCOME MEASURE(S)

Development of a prediction model for positive SR with TESA.

RESULTS

Overall, a positive SR was observed in 23.6% of patients undergoing TESA. Average testis size (P = .017) and serum follicle-stimulating hormone (FSH) level (P < .001) were the significant predictors of positive SR identified by LASSO regression analysis. The predictive model had an AUC of 0.742 with a sensitivity of 73.9% and specificity of 69.9%. Patients presenting with an average testis size >7.75 mL and serum FSH level <8.5 IU/L had a TESA-positive SR of 43%.

CONCLUSIONS

TESA may be a suitable alternative to microTESE in selected nonobstructive azoospermia patients presenting with an average testis size >7.75 mL and serum FSH level <8.5 IU/L.

Seminal Plasma Transcriptome and Proteome: Towards a Molecular Approach in the Diagnosis of Idiopathic Male Infertility

As the “-omic” technology has largely developed, its application in the field of medical science seems a highly promising tool to clarify the etiology, at least in part, of the so-called idiopathic male infertility. The seminal plasma (SP) is made-up of secretions coming from the male accessory glands, namely epididymis, seminal vesicles, and prostate. It is not only a medium for sperm transport since it is able to modulate the female reproductive environment and immunity, to allow the acquisition of sperm competence, to influence the sperm RNA content, and even embryo development. The aim of this systematic review was to provide an updated and comprehensive description of the main transcripts and proteins reported by transcriptome and proteome studies performed in the human SP of patients with idiopathic infertility, in the attempt of identifying possible candidate molecular targets. We recurrently found that micro RNA (miR)-34, miR-122, and miR-509 are down-regulated in patients with non-obstructive azoospermia (NOA) and oligozoospermia compared with fertile controls. These molecules may represent interesting targets whose predictive role in testicular sperm extraction (TESE) or assisted reproductive techniques (ART) outcome deserves further investigation. Furthermore, according to the available proteomic studies, ECM1, TEX101, lectingalactoside-binding andsoluble 3 binding protein (LGALS3BP) have been reported as accurate predictors of TESE outcome. Interestingly, ECM1 is differently expressed in patients with different ART outcomes. Further prospective, ample-sized studies are needed to validate these molecular targets that will help in the counseling of patients with NOA or undergoing ART.

Proteomics and metabolomics - Current and future perspectives in clinical andrology

Proteomics and metabolomics are emerging as promising tools to investigate the molecular mechanisms associated with male infertility. Proteins and metabolites play a pivotal role in regulating the molecular pathways associated with physiological functions of spermatozoa. Semen analysis, physical examination and laboratory work up cannot identify the etiology of infertility in 30%-40% of cases, which are classified as idiopathic. Therefore, the application of proteomics and metabolomics in the field of andrology will aid to overcome the limitations of the standard semen analysis. Understanding the molecular pathways associated with male infertility will help in planning ad hoc treatments, contributing to the clinical management of infertile patients. In this review, proteomics and metabolomics studies on spermatozoa and seminal plasma are discussed with a focus on molecular biomarkers associated with male infertility-related conditions.

Sperm recovery and ICSI outcomes in men with non-obstructive azoospermia: a systematic review and meta-analysis

BACKGROUND

Factor affecting sperm retrieval rate (SRR) or pregnancy rates (PR) after testicular sperm extraction (TESE) in patients with non-obstructive azoospermia (NOA) have not been systematically evaluated. In addition, although micro-TESE (mTESE) has been advocated as the gold standard for sperm retrieval in men with NOA, its superiority over conventional TESE (cTESE) remains conflicting.

OBJECTIVE AND RATIONALE

The objective was to perform a meta-analysis of the currently available studies comparing the techniques of sperm retrieval and to identify clinical and biochemical factors predicting SRR in men with NOA. In addition, PRs and live birth rates (LBRs), as derived from subjects with NOA post-ICSI, were also analysed as secondary outcomes.

SEARCH METHODS

An extensive Medline, Embase and Cochrane search was performed. All trials reporting SRR derived from cTESE or mTESE in patients with NOA and their specific determinants were included. Data derived from genetic causes of NOA or testicular sperm aspiration were excluded.

OUTCOMES

Out of 1236 studies, 117 studies met the inclusion criteria for this study, enrolling 21 404 patients with a mean age (± SD) of 35.0 ± 2.7 years. cTESE and mTESE were used in 56 and 43 studies, respectively. In addition, 10 studies used a mixed approach and 8 studies compared cTESE with mTESE approach. Overall, a SRR per TESE procedure of 47[45;49]% (mean percentage [95% CI]) was found. No differences were observed when mTESE was compared to cTESE (46[43;49]% for cTESE versus 46[42;49]% for mTESE). Meta-regression analysis demonstrated that SRR per cycle was independent of age and hormonal parameters at enrolment. However, the SRR increased as a function of testis volume. In particular, by applying ROC curve analysis, a mean testis volume higher than 12.5 ml predicted SRR >60% with an accuracy of 86.2% ± 0.01. In addition, SRR decreased as a function of the number of Klinefelter's syndrome cases included (S = -0.02[-0.04;-0.01]; P < 0.01. I = 0.12[-0.05;0.29]; P = 0.16). Information on fertility outcomes after ICSI was available in 42 studies. Overall, a total of 1096 biochemical pregnancies were reported (cumulative PR = 29[25;32]% per ICSI cycle). A similar rate was observed when LBR was analysed (569 live births with a cumulative LBR = 24[20;28]% per ICSI cycle). No influence of male and female age, mean testis volume or hormonal parameters on both PR and LBR per ICSI cycle was observed. Finally, a higher PR per ICSI cycle was observed when the use of fresh sperm was compared to cryopreserved sperm (PR = 35[30;40]%, versus 20[13;29]% respectively): however, this result was not confirmed when cumulative LBR per ICSI cycle was analysed (LBR = 30[20;41]% for fresh versus 20[12;31]% for cryopreserved sperm).

WIDER IMPLICATIONS

This analysis shows that cTESE/mTESE in subjects with NOA results in SRRs of up to 50%, with no differences when cTESE was compared to mTESE. Retrieved sperms resulted in a LBR of up to 28% ICSI cycle. Although no difference between techniques was found, to conclusively clarify if one technique is superior to the other, there is a need for a sufficiently powered and well-designed randomized controlled trial to compare mTESE to cTESE in men with NOA.

Prosaposin in seminal plasma on the day of oocyte retrieval is associated with normal fertilization and embryo development in in vitro fertilization cycles

The prospective study including 166 participants aims to evaluate the association between seminal prosaposin and the outcomes of in vitro fertilization (IVF) cycles in humans. The generalized linear model (GLM) was used to analyze the associations between seminal prosaposin concentrations and normal fertilization rates and good embryos proportion. The generalized estimating equation (GEE) was used to evaluate the association between embryo parameters and the prosaposin concentrations. Each model was adjusted for age of the couples, female basal FSH, AFC and BMI, starting dose and oocyte yield of IVF cycles and smoker. GLM models suggested that prosaposin was significantly associated with fertilization rate (P = 0.005) and good embryo proportion (P = 0.038) while none of the semen parameters (sperm concentration, motility, progressive motility, normal morphology rate, postwash sperm concentration and motility) was significantly associated with the parameters in the cohort. Using GEE, it was also shown that prosaposin was positively associated with the occurrence of early cleavage and negatively associated with uneven cleavage pattern on day 3. In both the overall population and the normozoospermia patients, the prosaposin was significantly associated with pregnancy with adjustment with covariates. In conclusion, our data suggested that seminal prosaposin concentration could provide more information regarding normal fertilization and embryo development in IVF than traditional semen parameters.

Stable-protein Pair Analysis as A Novel Strategy to Identify Proteomic Signatures: Application To Seminal Plasma From Infertile Patients

Our aim was to define seminal plasma proteome signatures of infertile patients categorized according to their seminal parameters using TMT-LC-MS/MS. To that extent, quantitative proteomic data was analyzed following two complementary strategies: (1) the conventional approach based on standard statistical analyses of relative protein quantification values; and (2) a novel strategy focused on establishing stable-protein pairs. By conventional analyses, the abundance of some seminal plasma proteins was found to be positively correlated with sperm concentration. However, this correlation was not found for all the peptides within a specific protein, bringing to light the high heterogeneity existing in the seminal plasma proteome because of both the proteolytic fragments and/or the post-translational modifications. This issue was overcome by conducting the novel stable-protein pairs analysis proposed herein. A total of 182 correlations comprising 24 different proteins were identified in the normozoospermic-control population, whereas this proportion was drastically reduced in infertile patients with altered seminal parameters (18 in patients with reduced sperm motility, 0 in patients with low sperm concentration and 3 in patients with no sperm in the ejaculate). These results suggest the existence of multiple etiologies causing the same alteration in seminal parameters. Additionally, the repetition of the stable-protein pair analysis in the control group by adding the data from a single patient at a time enabled to identify alterations in the stable-protein pairs profile of individual patients with altered seminal parameters. These results suggest potential underlying pathogenic mechanisms in individual infertile patients, and might open up a window to its application in the personalized diagnostic of male infertility.

Association between JMJD1A Expression and Sperm Retrieval in Non-Obstructive Azoospermic Patients

Identification of molecular markers which can predict the outcome of sperm retrieval non-invasively in patients with non-obstructive azoospermia (NOA) are valuable in clinical andrology. Jumonji domain-containing 1a (JMJD1A) is a significant epigenetic regulator during spermatogenesis, which plays an important role in the differentiation of post-meiotic germ cells into mature spermatozoa. We therefore aimed to examine the potential association between JMJD1A expression and the outcome of sperm retrieval in patients with NOA. Testicular biopsy specimens from 50 NOA patients with either successful sperm retrieval (sperm+, n=22) or failed sperm retrieval (sperm-, n=28) were collected and then examined for JMJD1A expression by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). In addition, conventional clinical parameters including luteinizing hormone, follicle-stimulating hormone, testosterone, age, and testicular volume were compared between the two NOA groups. The expression of JMJD1A in the sperm+ group was significantly higher than in the sperm- group (P<0.001), however, no significant difference was observed between the two groups in clinical parameters. The receiver operating characteristic (ROC) curve of JMJD1A expression in predicting the sperm retrieval outcome showed a sensitivity of 90.91% and a specificity of 89.29% with significant discriminatory ability between the sperm+ and sperm- groups [area under the ROC curve (AUC)= 0.91]. This study demonstrates a significant association between the expression of JMJD1A and the success of sperm recovery in patients with NOA, and thus suggests that JMJD1A expression quantification in testicular biopsies may be a valuable biomarker along with conventional parameters in predicting the presence of spermatozoa.

Prospective evaluation of scrotal ultrasound and intratesticular perfusion by color-coded duplex sonography (CCDS) in TESE patients with azoospermia

PURPOSE

The objective of this study was to assess whether CCDS might improve the outcome of testicular sperm retrieval in patients with azoospermia. Furthermore, we evaluated potential sonographic alterations of the testis before and after trifocal and Micro-TESE.

METHODS

78 patients were enrolled prospectively: 24 with obstructive azoospermia (OA) and 54 with non-obstructive azoospermia (NOA). 31 of 54 patients in the NOA group had negative surgical sperm retrieval. Testicular volume, hormonal parameters and sonographical findings were compared before and after TESE. The spermatogenetic score was determined for all retrieval sites. CCDS was performed at the upper, middle and lower segment of the testis. Ultrasound parameters and peak systolic velocity (PSV) were measured pre- and post-operatively.

RESULTS

Testicular volume and epididymal head size were significantly increased in OA patients compared to NOA patients. Ultrasound parameters were comparable between NOA patients with and without successful sperm retrieval. A higher intratesticular PSV was significantly correlated with a better spermatogenic score in the corresponding sonographic position. However, after adjustment for other clinical confounders, PSV does not show a significant influence on the spermatogenic score. Testicular volume decreased significantly in all patients post-operatively after 6 weeks (p < 0.001). Finally, the PSV significantly increased in all patients 24 h after surgery and nearly returned to baseline levels after 6 weeks (p < 0.001).

CONCLUSIONS

A higher intratesticular PSV may be helpful as a pre-operative diagnostic parameter in mapping for better sperm retrieval, but CCDS does not help to predict successful testicular sperm retrieval after adjustment for other clinical confounders.

Preclinical evaluation of a TEX101 protein ELISA test for the differential diagnosis of male infertility

BACKGROUND

TEX101 is a cell membrane protein exclusively expressed by testicular germ cells and shed into seminal plasma. We previously verified human TEX101 as a biomarker for the differential diagnosis of azoospermia, and developed a first-of-its-kind TEX101 ELISA. To demonstrate the clinical utility of TEX101, in this work we aimed at evaluating ELISA performance in a large population of fertile, subfertile, and infertile men.

METHODS

Mass spectrometry, size-exclusion chromatography, ultracentrifugation, and immunohistochemistry were used to characterize TEX101 protein as an analyte in seminal plasma. Using the optimized protocol for seminal plasma pretreatment, TEX101 was measured by ELISA in 805 seminal plasma samples.

RESULTS

We demonstrated that TEX101 was present in seminal plasma mostly in a free soluble form and that its small fraction was associated with seminal microvesicles. TEX101 median values were estimated in healthy, fertile pre-vasectomy men (5436 ng/mL, N = 64) and in patients with unexplained infertility (4967 ng/mL, N = 277), oligospermia (450 ng/mL, N = 270), and azoospermia (0.5 ng/mL, N = 137). Fertile post-vasectomy men (N = 57) and patients with Sertoli cell-only syndrome (N = 13) and obstructive azoospermia (N = 36) had undetectable levels of TEX101 (≤0.5 ng/mL). A cut-off value of 0.9 ng/mL provided 100% sensitivity at 100% specificity for distinguishing pre- and post-vasectomy men. The combination of a concentration of TEX101 > 0.9 ng/mL and epididymis-specific protein ECM1 > 2.3 μg/mL provided 81% sensitivity at 100% specificity for differentiating between non-obstructive and obstructive azoospermia, thus eliminating the majority of diagnostic testicular biopsies. In addition, a cut-off value of ≥0.6 ng/mL provided 73% sensitivity at 64% specificity for predicting sperm or spermatid retrieval in patients with non-obstructive azoospermia.

CONCLUSIONS

We demonstrated the clinical utility of TEX101 ELISA as a test to evaluate vasectomy success, to stratify azoospermia forms, and to better select patients for sperm retrieval.

Seminal biomarkers for the evaluation of male infertility

For men struggling to conceive with their partners, diagnostic tools are limited and often consist of only a standard semen analysis. This baseline test serves as a crude estimation of male fertility, leaving patients and clinicians in need of additional diagnostic biomarkers. Seminal fluid contains the highest concentration of molecules from the male reproductive glands, therefore, this review focuses on current and novel seminal biomarkers in certain male infertility scenarios, including natural fertility, differentiating azoospermia etiologies, and predicting assisted reproductive technique success. Currently available tests include antisperm antibody assays, DNA fragmentation index, sperm fluorescence in situ hybridization, and other historical sperm functional tests. The poor diagnostic ability of current assays has led to continued efforts to find more predictive biomarkers. Emerging research in the fields of genomics, epigenetics, proteomics, transcriptomics, and metabolomics holds promise for the development of novel male infertility biomarkers. Seminal protein-based assays of TEX101, ECM1, and ACRV1 are already available or under final development for clinical use. Additional panels of DNA, RNA, proteins, or metabolites are being explored as we attempt to understand the pathophysiologic processes of male infertility. Future ventures will need to continue data integration and validation for the development of clinically useful infertility biomarkers to aid in male infertility diagnosis, treatment, and counseling.

Recent advances in understanding & managing male infertility

Male infertility remains a struggle to definitively diagnose and treat with many men labelled as “idiopathic infertility” and eventually requiring assisted reproductive techniques.  Along those lines, research groups are continuing to explore current social and environmental factors, including the obesity epidemic, and their effects on male fertility potential.  Novel biomarkers of natural fertility status and azoospermia etiology have additionally seen recent attention with ACRV1 and TEX101/ECM1 assays either currently or soon to be commercially available.  Despite these advancements, however, medical treatment options have seen little progress.  Though surgical therapies have similarly seen little transformation, groups are exploring the use of testicular sperm for couples with elevated sperm DNA fragmentation and either planned or previously failed IVF/ICSI.  Concerted collaborative efforts will be needed as we move forward to better understand the challenges men face when struggling to conceive.

Proteomic profile of seminal plasma in adolescents and adults with treated and untreated varicocele

Varicocele, the most important treatable cause of male infertility, is present in 15% of adult males, 35% of men with primary infertility, and 80% of men with secondary infertility. On the other hand, 80% of these men will not present infertility. Therefore, there is a need to differentiate a varicocele that is exerting a deleterious effect that is treatable from a “silent” varicocele. Despite the growing evidence of the cellular effects of varicocele, its underlying molecular mechanisms are still eluding. Proteomics has become a promising area to determine the reproductive biology of semen as well as to improve diagnosis of male infertility. This review aims to discuss the state-of-art in seminal plasma proteomics in patients with varicocele to discuss the challenges in undertaking these studies, as well as the future outlook derived from the growing body of evidence on the seminal proteome.

Proteomic profile of seminal plasma in adolescents and adults with treated and untreated varicocele

Varicocele, the most important treatable cause of male infertility, is present in 15% of adult males, 35% of men with primary infertility, and 80% of men with secondary infertility. On the other hand, 80% of these men will not present infertility. Therefore, there is a need to differentiate a varicocele that is exerting a deleterious effect that is treatable from a "silent" varicocele. Despite the growing evidence of the cellular effects of varicocele, its underlying molecular mechanisms are still eluding. Proteomics has become a promising area to determine the reproductive biology of semen as well as to improve diagnosis of male infertility. This review aims to discuss the state-of-art in seminal plasma proteomics in patients with varicocele to discuss the challenges in undertaking these studies, as well as the future outlook derived from the growing body of evidence on the seminal proteome.

Sample treatment methods involving combinatorial peptide ligand libraries for improved proteomes analyses

If used in an optimized manner, the technology of combinatorial peptide solid-phase libraries can easily improve the analytical determinations of proteomes by several factors. The discovery of novel species and of early stage biomarkers becomes thus reachable with a simple sample treatment. This report describes the most important point to consider (overloading and full recovery) along with a minimum scientific background and gives then detailed recipes to laboratory technicians. Orientations for optional routes are also given according to the objective of the experimental investigations. This covers different approaches to capture proteins of very low abundance. Total protein harvestings to prevent partial losses are also described such as single exhaustive desorption and fractionated elutions for more detailed analyses. Documented results are also reported demonstrating the capability of the technology well beyond what is the common assumption.

Shotgun proteome analysis of honeybee venom using targeted enrichment strategies

The aim of this study was to explore the honeybee venom proteome applying a shotgun proteomics approach using different enrichment strategies (combinatorial peptide ligand libraries and solid phase extraction). The studies were conducted using nano-LC/MALDI-TOF/TOF-MS system. The MS analysis of peptide profiles (in the range of 900-4500 Da) and virtual gel-image of proteins from Lab-on-Chip assay (in the range of 10-250 kDa) confirm that use of targeted enrichment strategies increase detection of honeybee venom components. The gel-free shotgun strategy and sophisticated instrumentation led to a significant increase of the sensitivity and higher number of identified peptides in honeybee venom samples, comparing with the current literature. Moreover, 11 of 12 known honeybee venom allergens were acknowledged and 4 new, so far uncharacterized proteins were identified. In addition, similarity searches were performed in order to investigate biological relations and homology between newly identified proteins sequences from Apis mellifera and other Hymenoptera.

Proteomics and integrative genomics for unraveling the mysteries of spermatogenesis: the strategies of a team

The strikingly complex structural organization of the mammalian testis in vivo creates particular difficulties for studies of its organization, function and regulation. These difficulties are particularly pronounced for investigations of the molecular communication networks within the seminiferous tubules that govern spermatogenesis. The use of classical molecular and cell biology approaches to unravel this complexity has proved problematic, due to difficulties in maintaining differentiated germ cells in vitro, in particular. The lack of a suitable testing ground has led to a greater reliance on high-quality proteomic and genomic analyses as a prelude to the in vitro antx1d in vivo testing of hypotheses. In this study, we highlight the options currently available for research, as used in our laboratory, in which proteomic and integrative genomic strategies are applied to the study of spermatogenesis in mammals. We will comment on results providing insight into the molecular mechanisms underlying normal and pathological spermatogenesis and new perspectives for the treatment of male infertility in humans. Finally, we will discuss the relevance of our strategies and the unexpected potential and perspectives they offer to teams involved in the study of male reproduction, within the framework of the Human Proteome Project.

SIGNIFICANCE

Integrative genomics is becoming a powerful strategy for discovering the biological significance hidden in proteomic datasets. This work introduces some of the integrative genomic concepts and works used by our team to gain new insight into mammalian spermatogenesis, a remarkably sophisticated process. We demonstrate the relevance of these integrative approaches to understand the cellular cross talks established between the somatic Sertoli cells and the germ cell lineage, within the seminiferous epithelium. Our work also contributes to new knowledge on the pathophysiology of testicular function, with promising clinical applications. This article is part of a Special Issue entitled: 20years of Proteomics in memory of Viatliano Pallini. Guest Editors: Luca Bini, Juan J. Calvete, Natacha Turck, Denis Hochstrasser and Jean-Charles Sanchez.