Protein Fingerprinting of Seminal Plasma Reveals Dysregulation of Exosome-Associated Proteins in Infertile Men with Unilateral Varicocele

Purpose: Aberrant expression of seminal plasma proteins are associated with altered homeostasis that may affect the fertilizing ability of spermatozoa. However, the precise roles of seminal exosomes on sperm function remain unclear. The objective of this study was to identify the differentially expressed proteins (DEPs) associated with varicocele-mediated infertility by comparing seminal plasma protein profile of unilateral varicocele patients with proven fertile donors. Materials and Methods: Semen samples were obtained from 10 proven fertile donors with normal semen parameters and 33 infertile patients with unilateral varicocele. For proteomic analysis, 5 samples from each group were pooled and run in triplicate. Key DEPs (ANXA2, TF, CD63, KIF5B, SEMG1) associated with the exosome function were selected by bioinformatic tools and validated using Western blotting. Results: A total of 47 seminal plasma proteins were differentially expressed in unilateral varicocele patients compared to fertile donors. Validation of exosome-associated DEPs in unilateral varicocele patients (n=7) and fertile donors (n=7) revealed significant upregulation of ANXA2 (p=0.0016) and downregulation of KIF5B (p=0.009). The main upstream regulators of the DEPs in seminal plasma of unilateral varicocele group were androgen receptor, YB1 and NRF2. Conclusions: This is the first report to identify DEPs in seminal plasma of unilateral varicocele patients compared to fertile donors. Based on the detection of DEPs associated with exosomal function, Western blotting was used to validate the presence of defective exosome machinery in seminal plasma of unilateral varicocele patients. KIF5B and ANXA2 can be utilized as potential biomarkers of infertility in unilateral varicocele patients.