Sperm single-stranded DNA, detected by acridine orange staining, reduces fertilization and quality of ICSI-derived embryos

Purpose: The aim of this study was to evaluate the effect of sperm single-stranded DNA, detected by acridine orange (AO), and classical sperm parameters on embryonic quality after ICSI. Methods: Before ICSI, the spermatozoa of 183 infertile patients with oligo-, astheno-, teratozoospermia (n = 147), or more than one previous unsuccessful conventional IVF attempt (n = 36) were stained by AO to assess the presence of single-stranded DNA. Two days after ICSI, the embryos of 135 patients were scored for morphology, fragmentation included. Embryos of 48 couples were cultured for 4 days to develop to the morula or blastocyst stage. At most 2 embryos were transferred on Day 2 or 4. Results: When the level of spermatozoa with single-stranded DNA was increased, there was a significantly lower fertilization rate after ICSI. Besides, increased sperm single-stranded DNA resulted in a higher proportion of heavily fragmented embryos on Day 2 (P < 0.05). In patients with an increased level of spermatozoa with single-stranded DNA, a significantly higher number of embryos were arrested in spite of prolonged culturing (P < 0.05). Classical sperm parameters did not affect the quality and developmental potential of ICSI-derived embryos. No correlation was found between the level of spermatozoa with single-stranded DNA, pregnancy rate, and live-birth rate achieved by ICSI, except in patients with 0% of spermatozoa with single-stranded DNA, in whom the pregnancy rate was significantly higher. Conclusions: Sperm single-stranded DNA provides additional data on sperm functional capacity in terms of fertilization and embryonic quality after ICSI.