Determination of testicular function in adolescents with varicocoele - a proteomics approach.

The goal of this study was to determine seminal plasma biomarkers of testicular function in adolescents with varicocoele and to verify enriched gene ontology terms associated to these differential proteomes. An observational study was carried out in an academic research environment. A total of 77 adolescent patients were recruited from a local public school, of which 23 were without varicocoele and with normal semen analysis (control group), 37 were with varicocoele and normal semen (VNS) parameters, and 17 were with varicocoele and altered semen (VAS) parameters. Two semen collections were provided with a 1-week interval, after 2-5 days of ejaculatory abstinence. Seminal plasma proteins were identified and quantified utilizing a label-free shotgun proteomics approach, generating (i) proteins differentially expressed in each group (control, VNS, and VAS) and putative biomarkers using multivariate statistics followed by discriminant analysis. Confirmatory analysis was performed for two proteins by western blotting. Enriched biological processes and molecular functions were determined using gene ontology analysis. In total, 541 proteins were identified and quantified: 108 exclusive or overexpressed in controls, 26 in the VNS group, and 13 in the VAS group. The suggested biomarkers are Cab45/SDF4 (Q9BRK5), protein lefty-1 (O75610), DNase I (P24855), PAP2-alpha (O14494), IBP-7 (Q16270), HDC (P01860), and CRISP-3 (P54108). Western blotting results showed that Cab45 was significantly underexpressed in both varicocoele groups, and CRISP-3 was significantly overexpressed in seminal plasma of adolescents with VAS. In conclusion, specific biomarkers of spermatogenesis and homeostasis are observed in adolescents without varicocoele, and the presence of a palpable varicocoele progressively shifts these adolescents toward initially an immune response, and finally toward a chronic inflammatory profile. This shift is accompanied by decreased semen quality.

Unbiased label-free quantitative proteomic profiling and enriched proteomic pathways in seminal plasma of adult men before and after varicocelectomy.

STUDY QUESTION: Does the seminal plasma proteomic profile and functional enrichment of gene ontology terms change after microsurgical varicocelectomy? Are there any potential targets for diagnosis or therapeutic intervention in varicocele? SUMMARY ANSWER: A shift in state from a responsive-to-stress condition before varicocele correction to a responsive-to-environment condition after varicocelectomy was observed in enriched proteomic pathways. WHAT IS KNOWN ALREADY: Varicocele may lead to many adverse effects, including failure of testicular growth and development, and is associated with decreased semen quality and increased semen oxidative stress. Varicocelectomy is the treatment of choice, and is associated with improved semen quality, but little is known regarding the underlying molecular mechanisms and post-genomic pathways following intervention. STUDY DESIGN, SIZE, DURATION: A prospective study was carried out including 18 adult men with varicocele. These patients provided one semen sample before they were submitted for bilateral varicocele repair through microsurgical varicocelectomy, and one other semen sample 90 days after the surgery. PARTICIPANTS/MATERIALS, SETTING, METHODS: An aliquot of each semen sample was used for unbiased proteomics analysis by a label-free quantitative approach (2D nanoUPLC-ESI-MS(E)). Samples were pooled according to group (normalized to protein content) and run in quadruplicate. These quadruplicate runs provided degrees of freedom in order to compare groups using a non-parametric Mann-Whitney test for quantified proteins. MAIN RESULTS AND THE ROLE OF CHANCE: A total of 316 proteins were quantified or identified, of which 91 were exclusively identified or quantified in one of the groups (53 in the pre- and 38 in the post-varicocelectomy group), and 68 were quantified in both groups and submitted to statistical analysis, of which 5 were overrepresented in the pre-varicocelectomy group (P < 0.05). In enriched functional analysis, binding and response to stimulus functions were enriched in a common cluster (present in both groups), nitric oxide metabolism and tetratricopeptide repeat domain-binding functions were enriched in the pre-varicocelectomy group, and response to reactive oxygen species, gluconeogenesis, nicotinamide adenine dinucleotide-binding and protein stabilization were enriched in the post-varicocelectomy. LIMITATIONS, REASONS FOR CAUTION: Because a shotgun proteomics analysis was chosen in order to generate a list of putative biomarkers, a targeted follow-up study should be performed to confirm these biomarkers. WIDER IMPLICATIONS OF THE FINDINGS: The proteins found in both groups possess functions usually found in human semen. The enriched function analysis demonstrated a shift back to homeostasis after varicocelectomy, suggesting that varicocele correction promotes return of semen to a physiological state. STUDY FUNDING/COMPETING INTEREST(S): The funding for this project was received from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) as a scholarship for Ms Camargo. There was no conflict of interest.