Sperm DNA fragmentation in the total and vital fractions before and after density gradient centrifugation: Significance in male fertility diagnosis.

BACKGROUND: Sperm DNA fragmentation measured by different techniques make comparisons impossible due to lack of standardization. Induction of DNA damage after sperm preparation in the entire fraction has been observed on independent occasions but findings are not consistent.

METHODS: Men presenting at a University hospital setup for infertility treatment. DNA damage via TUNEL assay was validated on fresh semen samples, as conventional semen parameters, to reduce variability of results.

RESULTS: Sperm motility in neat semen inversely correlated with sperm DNA fragmentation in the total fraction, but, total count, leukocytes and immature germ cells significantly affected the vital fraction. Sperm DNA fragmentation was observed both in normal and subnormal semen samples, but was significantly different in the total fraction of astheno-, asthenoterato- and oligoteratozoospermic men. After density gradient centrifugation, sperm DNA fragmentation increased significantly in the total but decreased in the vital fraction. Advancing male age significantly influenced damage in the total but not in the vital population.

CONCLUSIONS: These findings provide opportunities to investigate the significance of the total and the vital fractions both in natural conception and after different assisted reproductive technologies.