Early apoptotic changes in human spermatozoa and their relationships with conventional semen parameters and sperm DNA fragmentation

Aim: To investigate whether early apoptotic changes in spermatozoa can be significant markers for sperm quality. Methods: Two early apoptotic changes in the semen of 56 men were assessed using Annexin V (AN)/propidium iodide (PI) staining for phosphatidylserine externalization and JC-1 staining for mitochondrial membrane potential (MMP). The results were compared with conventional semen parameters and DNA fragmentation identified using the TUNEL assay. Results: The different labeling patterns in the bivariate Annexin V/PI analysis identified four distinctive spermatozoa populations. The percentage of AN(-)/PI- spermatozoa positively correlated with conventional semen parameters and MMP, but negatively correlated with TUNEL (+) spermatozoa. As for the AN(-)/PI+ fraction, we found an opposite result in comparison to AN(-)/PI- spermatozoa. The level of early apoptotic AN(+)/PI- spermatozoa negatively correlated with MMP and sperm motility. The level of late apoptotic AN(+)/PI+ spermatozoa negatively correlated with conventional semen parameters and MMP, and positively correlated with TUNEL (+) spermatozoa. MMP positively correlated with conventional semen parameters, but negatively correlated with TUNEL (+) spermatozoa. Conclusion: Although early apoptotic AN(+)/PI- spermatozoa only negatively correlates with sperm motility, the differences in proportion of each subpopulation of spermatozoa (especially, the percentage of AN(-)/PI- spermatozoa), and decreased MMP might be significant markers for diagnosing male infertility. They possibly bring additional information to predict the outcome of in vitro fertilization.