Differential proteomic profiling of spermatozoal proteins of infertile men with unilateral or bilateral varicocele.

To compare the sperm protein profile between infertile men with unilateral varicocele and infertile men with bilateral varicocele. This prospective study investigated 50 infertile patients with clinical varicocele (33 unilateral and 17 bilateral) seeking fertility workup between March 2012 and April 2014. Routine sperm parameters, reactive oxygen species, total antioxidant capacity, and sperm deoxyribonucleic acid fragmentation were assessed in their semen. Sperm protein profile was characterized only in pooled samples of 5 unilateral and 3 bilateral varicocele samples, respectively, using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and an Linear Trap Quadrupole-Orbitrap Elite hybrid mass spectrophotometer system. Differences in protein expression were analyzed using gel analysis software, followed by protein identification using mass spectroscopy analysis. Differentially expressed proteins and their abundance were quantified by comparing spectral counts, followed by bioinformatics analysis. Unique expression of 64 proteins in the bilateral group and 31 proteins in the unilateral group was obtained. Core functions of the top protein interaction networks were post-translational modification (∼122 proteins associated with acetylation), protein folding, free-radical scavenging, cell death, and survival. The top molecular and cellular functions were protein degradation, free radical scavenging, and post-translational modifications, whereas the top pathways were protein ubiquitination and mitochondrial dysfunction. Major biological pathways for the 253 differentially expressed proteins were metabolism, apoptosis, and signal transduction. Functional proteomic profiling helps identify the differential processes or pathways that are affected based on the nature of varicocele (bilateral or unilateral) and provide insights into the mechanistic implications of varicocele-associated male infertility.