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

Abstract

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.