Easy sperm processing technique allowing exclusive accumulation and later usage of DNA-strandbreak-free spermatozoa

Sperm DNA fragmentation is increased in poor-quality semen samples and correlates with failed fertilization, impaired preimplantation development and reduced pregnancy outcome. Common sperm preparation techniques may reduce the percentage of strandbreak-positive spermatozoa, but, to date, there is no reliable approach to exclusively accumulate strandbreak-free spermatozoa. To analyse the efficiency of special sperm selection chambers (Zech-selectors made of glass or polyethylene) in terms of strandbreak reduction, 39 subfertile men were recruited and three probes (native, density gradient and Zech-selector) were used to check for strand breaks using the sperm chromatin dispersion test. The mean percentage of affected spermatozoa in the ejaculate was 15.8 ± 7.8% (range 5.0–42.1%). Density gradient did not significantly improve the quality of spermatozoa selected (14.2 ± 7.0%). However, glass chambers completely removed 90% spermatozoa showing strand breaks and polyethylene chambers removed 76%. Both types of Zech-selectors were equivalent in their efficiency, significantly reduced DNA damage (P < 0.001) and, with respect to this, performed better than density gradient centrifugation (P < 0.001). As far as is known, this is the first report on a sperm preparation technique concentrating spermatozoa unaffected in terms of DNA damage. The special chambers most probably select for sperm motility and/or maturity.Sperm DNA fragmentation is increased in poor-quality semen samples and correlates with failed fertilization, impaired preimplantation development and reduced pregnancy outcome. Common sperm preparation techniques may reduce the percentage of strandbreak-positive spermatozoa, but, to date, there is no reliable approach to exclusively accumulate strandbreak-free spermatozoa. To analyse the efficiency of special sperm selection chambers in terms of strandbreak reduction, 39 subfertile men were recruited. Three probes (native, density gradient, and selection chamber) were used to check for strand breaks using the sperm chromatin dispersion test. The mean percentage of affected sperms in the ejaculate was 15.8 ± 7.8% (range 5.0–42.1%). Density gradient did not significantly improve the quality of spermatozoa selected (14.2 ± 7.0%). However, glass and polyethylene chambers completely removed sperms showing strand breaks in 90% and 76% of patients, respectively. Both types of selecting chambers were equivalent in their efficiency and significantly reduced DNA damage (P < 0.001) and, with respect to this, performed better than density gradient centrifugation (P < 0.001). This is the first report on a sperm preparation technique concentrating unaffected spermatozoa (in terms of DNA damage). The special chambers most probably select for sperm motility and/or maturity. A prospective study using guaranteed strandbreak-free spermatozoa for intracytoplasmic sperm injection is ongoing.