Assessing sperm DNA fragmentation with the sperm chromatin dispersion test

The sperm cell has evolved to transmit a paternal haploid genome to the oocyte and form a new embryo. Therefore, it is essential that the integrity of this genome be evaluated as part of the standard semen analysis. The assessment of DNA fragmentation is consequently considered as an important parameter of sperm quality. The Sperm Chromatin Dispersion (SCD) test is a simple, fast, and reliable procedure to determine the frequency of sperm cells with fragmented DNA, and this may be confidently performed with the Halosperm(®) kit. Unfixed sperm cells are immersed in an agarose microgel on a slide, incubated in an acid unwinding solution that transforms DNA breaks into single-stranded DNA, and then in a lysing solution to remove protamines. After staining, the spermatozoa without fragmented DNA shows nucleoids with big halos of spreading of DNA loops, whereas those with fragmented DNA appear with a small or no halo. This may be visualized using fluorescence microscopy or with the standard bright-field microscope, without the requirement of more complex or expensive instrumentation. This procedure is very versatile, and being a diffusion-like assay with only a lysis protocol, may be usefully adapted for other species. Moreover, simultaneous determination of aneuploidies may be accomplished in the same sperm cell.