Sperm chromatin anomalies can influence decondensation after intracytoplasmic sperm injection

In this study we investigated whether morphology and chromatin anomalies in human spermatozoa can influence fertilization after intracytoplasmic sperm injection (ICSI). We examined unfertilized oocytes, using the fluorochrome Hoechst 33342, to determine whether a relationship exists between failure of fertilization and sperm chromatin quality. Sperm chromatin packaging quality was assessed using the chromomycin A3 (CMA3) fluorochrome, and the presence of DNA damage in spermatozoa, using in-situ nick translation, Normal males present sperm parameters with a normal morphology of > 20%, CMA3 fluorescence of < 30% and exhibit endogenous nicks in < 10% of their spermatozoa. When patients were separated according to these values no difference was observed in their fertilization rates after ICSI. When the unfertilized ICSI oocytes were examined, we found that patients with CMA3 fluorescence of <30% and nicks in < 10% of their spermatozoa had only 17.5 and 21.6% respectively of their unfertilized oocytes containing spermatozoa that remained condensed. In contrast, patients with higher CMA3 and nick values had a significantly higher number, 41.2 and 48.9%, of their unfertilized oocytes containing condensed spermatozoa. sperm morphology did not show any such pattern. The percentage of spermatozoa which had initiated decondensation in unfertilized oocytes was not influenced by morphology, CMA3 fluorescence or nicks. In light of these results we postulate that poor chromatin packaging and/or damaged DNA may contribute to failure of sperm decondensation after ICSI and result in failure of fertilization.