The vasal fluid proteomic profile and microscopic sperm presence at time of vasectomy reversal

Background: The microscopic characteristics of vasal fluid at time of vasectomy reversal (VR) guide operative decision making and predict fertility outcomes. The proteomic profile of this vasal fluid has not been described or correlated with the microscopic fluid appearance. To characterize the vasal fluid proteome at time of VR and evaluate the variation of the vasal fluid proteome with respect to microscopic presence of sperm. Methods: A prospective cohort study was conducted enrolling twenty-five men undergoing VR for infertility and/or pain at a University-affiliated hospital. Vasal fluid samples obtained at time of VR were grouped based on presence of sperm on light microscopy at time of VR. Proteomic profiles were generated using liquid chromatography/ tandem mass spectrometry, and MS/MS protein spectral counts compared between individuals and treatment groups, controlling for less than 5% protein false discovery rate (FDR). Proteins were matched with the human swissprot database using the Comet search engine, and categorized by Gene Ontology (GO) terms. Results: There was large variability between the 46 vasal fluid samples collected, with 1,692 unique proteins detected. The three most abundant proteins were Lactotransferrin, Cysteine-rich secretory protein 1, A-kinase anchor protein 4. There was no correlation between the proteome and microscopic sperm presence. Prevalent GO terms included viral process, signal transduction, innate immune response, protein folding and spermatogenesis. Conclusions: We describe the proteome and the most common proteins in vasal fluid at time of VR. Numerable sperm, testis and epididymis specific proteins were present even in the absence of sperm on microscopy. Further evaluation is needed to determine if a protein biomarker may better guide operative decision making and predict VR fertility outcomes.