The effect of an environmental toxin, perfluorooctanoic acid, on cryopreserved-thawed, human sperm

Abstract

Perfluorooctanoic acid (PFOA) is the final breakdown product of ammonium perfluorooctanoate, which is used in the production of cookware made with Teflon, food wrappers for the fast food industry, clothing, and products that impart stain resistance in carpet, leather, and fabric. The goal of this study was to evaluate the direct effects of PFOA on human live sperm in vitro. A prospective study evaluating the effects of PFOA on human sperm using cryopreserved-thawed semen samples obtained from a population of donor males. Frozen semen samples were thawed in a water bath at 37oC. The samples were washed × 2 in human tubal fluid with HEPES buffer and 5% synthetic albumin (HHTF) and a post-thaw semen analysis was performed. Only samples that were normal by WHO guidelines were used for this study. Perfluorooctanoic acid was dissolved in HHTF and added to individual tubes containing semen for final PFOA concentrations of 0 (control), 0.5, 5, 50, 250, 500 and 1000μM. The concentrations of PFOA used in this study were chosen based on PFOA concentrations that have been measured in human plasma[0.5 to 250μM] and concentrations known to cause Leydig cell toxicity[250–1000μM]. Samples were evaluated for sperm concentration, motility, progression, and vigor by Computer Assisted Semen Analysis (CASA) at baseline, 1, 3, 5, and 7 hours after the initiation of exposure to PFOA. The primary study outcome was sperm motility over time, both between and within groups. Secondary study outcomes included straight-line velocity (VSL), curvilinear velocity (VCL), and amplitude of lateral head displacement (ALH). For statistical analysis, ANOVA and general linear regression were used to determine statistical significance. Tukey's test was used for post-hoc analysis. There was no change in sperm concentration over time. There was a dose dependent decrease in sperm motility in cryopreserved-thawed sperm treated with PFOA as shown in figure 1. There was no significant change in sperm motility in the control group over time. However, all treatment groups demonstrated a significant reduction in sperm motility from baseline including:[0.5μM] at times 3 and 7 hour (p= 0.02);[5μM] from 1 hour onward (p< 0.01); and[50–1000μM] from 1 hour onward (p< 0.001). There was a significant decrease in VSL in the[1000μM] treatment group at all time periods and a significant decrease in VAP in the[1000μM] treatment group at the 1,3 and 7 hour time periods. There was no difference in ALH for any treatment group over time. This is the first study to demonstrate that PFOA treatment of cryopreserved-thawed sperm leads to a dose dependent decrease in sperm motility in vitro. Whether PFOA causes detrimental effects on sperm function in vivo is a subject of ongoing research by our laboratory.