A bioassy to measure fertilization competence of human spermatozoa

OBJECTIVE: To test a biomarker-based assay to diagnose sperm function which specifically predicts the ability to capacitate and fertilize. DESIGN: We assessed ganglioside GM1 localization in sperm as a biomarker to quantify the sub-population that could respond to capacitating stimuli and become fertilization competent. Specific patterns of sperm GM1 localization were quantified in basal and capacitating conditions on semen samples of consenting men with the aim of predicting fertilizing ability. MATERIALS AND METHODS: Semen parameters were evaluated according to WHO 2010 criteria. Samples were scored via fluorescence microscopy for GM1 localization patterns reflecting capacitation status in at least 200 sperm incubated under both standard and capacitating media. Based on preliminary data and normal timing of human sperm capacitation within 4hrs, we made observations at 1, 2, and 3hrs. Men were categorized as having normal or abnormal capacitation based on pattern frequencies compared to our reference ranges, and then clinical outcomes followed to assess predictive ability. RESULTS: In all tested men (n 1⁄4 63), average semen parameters were 58.1 20 x10/ml, motility of 47.8 8%, and normal morphology of 2.7 1%. We identified 31 men with scores matching the normal reference group, with baseline GM1 patterns of 17%-22%-28% in standard and 26%31%-38% in capacitating media, respectively. We identified 32 men with below reference values of 15%-20%-24% in standard and 20%-25%-29% in capacitating media. Semen parameters were comparable between the two groups. The population with normal range GM1 patterns had an IUI pregnancy rate of 45.2% (14/31) of which 8 (25.8%) generated at least one fetal heartbeat. Three additional couples in this group became pregnant on their own. For men with below-reference GM1 patterns, the IUI clinical pregnancy rate was only 6.3% (2/32; P1⁄4 0.03). In this cohort, 13 underwent ICSI and 6 became pregnant (46.2%). CONCLUSION: The GM1 assay reflected sperm fertilizing ability and could identify men prone to IUI failure irrespective of semen parameters. Assay results may guide selection of optimal ART treatment. Supported by: BioAccelerate NYC Prize through the Partnership Fund of New York City (A.J. Travis, Cornell). Dr. Travis taught methods to the Palermo lab, who independently recruited patients, performed assays and analyzed results.