Interrelationships between seminal parameters and sperm nuclear DNA damage before and after density gradient centrifugation: implications for assisted conception

BACKGROUND: With an increase in the use of assisted reproduction technologies the requirements of the diagnostic semen analysis are constantly changing. METHODS: Spermatozoa from patients undergoing IVF were analysed by examining the conventional semen parameters and DNA/chromatin integrity, using in-situ nick translation (NT) and the Chromomycin A3 fluorochrome, which indirectly demonstrates a decreased presence of protamine. Samples were examined before and after preparation using discontinuous density gradient centrifugation. RESULTS: Density gradient centrifugation enriched samples by improving the percentage of morphologically normal forms by 138% and sperm nuclear integrity by 450%. Sperm nuclear integrity as assessed by in-situ nick translation (NT) demonstrated a very clear relationship with sperm concentration, motility and morphology. Morphology correlated with fertilization rates of patients undergoing IVF, while NT values of the spermatozoa post-preparation were significantly lower in pregnant patients. CONCLUSIONS: We have demonstrated that along with the classical semen parameters, the assessment of nuclear integrity improves the characterization of the semen sample and may be used as a tool for allocating patients to specific assisted reproduction treatments.