Processing of semen by density gradient centrifugation selects spermatozoa with longer telomeres for assisted reproduction techniques

Abstract

The ends of eukaryotic chromosomes contain specialized chromatin structures called telomeres, the length of which plays a key role in early human embryonic development. Although the effect of sperm preparation techniques on major sperm characteristics, such as concentration, motility and morphology have been previously documented, the possible status of telomere length and its relation with sperm preparation techniques is not well-known for humans. The aim of this study was to investigate the role of density gradient centrifugation in the selection of spermatozoa with longer telomeres for use in assisted reproduction techniques in 105 samples before and after sperm processing. After density gradient centrifugation, the average telomere length of the sperm was significantly longer (6.51 ± 2.54 versus 5.16 ± 2.29, P < 0.01), the average motile sperm rate was significantly higher (77.9 ± 11.8 versus 44.6 ± 11.2, P < 0.01), but average DNA fragmentation rate was significantly lower (11.1 ± 5.9 versus 25.9 ± 12.9, P < 0.01) compared with raw semen. Additionally, telomere length was positively correlated with semen sperm count (rs = 0.58; P < 0.01). In conclusion, density gradient centrifugation is a useful technique for selection of sperm with longer telomeres.

Semen preparation methods and sperm telomere length: density gradient centrifugation versus the swim up procedure

“…To the best of our knowledge, this is the first study to compare the telomere length in sperm cells recovered by the DGC and SU methods. In our study, the STL of the spermatozoa enriched by these both methods was longer than that in raw semen, which is consistent with previous studies that have demonstrated that either the SU or the DGS method could select sperm with a longer STL and lower DNA fragmentation3536. Nevertheless, no significant difference was found between the STL in sperm obtained by the two procedures.…”

“…Sperm DNA fragmentation was determined using a kit according to the manufacturer’s instructions (BRED, Life Science Technology Inc., Shenzhen, China), and the detailed steps are described in a previous study36. More than 500 sperm were assessed for each sample under a 100X objective on an Olympus BX51 microscope.…”

“…Santiso et al . and our previous study showed that either the SU or DGC method could screen out sperm with longer telomeres and lower DNA fragmentation for fertilization3536. However, no study has examined the effects of these two methods on the STL of sperm.…”

Does combining magnetic-activated cell sorting with density gradient or swim-up improve sperm selection?

“…Here, in addition to PLC-ζ or Izumo-1 distribution patterns at a high-resolution 3-D confocal microscopic level, we also analyzed the sperm morphology according to strict criteria and found no significant difference between groups in the NZS cases. Our finding that SU+MACS or DG+MACS resulted in lower DNA fragmentation and higher DNA integrity compared to SU or DG alone at the statistically insignificant level indicated that SU or DG alone are also beneficial techniques to select spermatozoa with high DNA quality as it has been indicated by previous studies [11,12]. Very recently, Bucar et al [13] demonstrated that the application of MACS following DG and SU gave a significantly lower number of total or rapid progressive spermatozoa compared to others.…”

Investigation of sperm telomere length as a potential marker of paternal genome integrity and semen quality

“…Few studies have been published on STL in relation to semen parameters, and the small amount of information that is available is contradictory. Thilagavathi et al (2013) did not find any correlation with conventional sperm parameters and telomere length, whereas other studies reported a positive association between STL and sperm count in young donors (aged 18-19 years) (Ferlin et al, 2013) and in infertile patients (Yang et al, 2015).…”