Enolase1 (ENO1) and glucose-6-phosphate isomerase (GPI) are good markers to predict human sperm freezability

Sperm cryopreservation is a method to preserve sperm samples for a long period. However, the fertility of sperm decreases markedly after freezing and thawing in a certain amount of samples. The aim of the present study was to find useful and reliable predictive biomarkers of the capacity to withstand the freeze-thawing process in human ejaculates. Previous researches have shown that enolase1 (ENO1) and glucose-6-phosphate isomerase (GPI) are closely related to spermatozoa quality. We chose the two proteins as probable markers of sperm freezing capacity. Ejaculate samples were separated into good freezability ejaculates (GFE) and poor freezability ejaculates (PFE) according to progressive motility of the sperm after thawing. Before starting cryopreservation protocols, the two proteins from each group were compared using western blot analysis and immunofluorescence. Results showed that normalized content of ENO1 (P < 0.05) and GPI (P < 0.01) were both significantly higher in GFE than in PFE. The association of ENO1 and GPI with postthaw sperm viability and motility was confirmed using Pearson's linear correlation. In conclusion, ENO1 and GPI can be used as markers of human sperm freezability before starting the cryopreservation procedure.