Authors Rocca MS, Speltra E, Menegazzo M, Garolla A, Foresta C, Ferlin A
Review Date April 2016
Citation Human Reproduction, 2016 doi:10.1093/humrep/dew061 (online ahead of print)
Semen analysis is limited in its power to predict whether a man is fertile and often fails to find abnormalities in the semen of infertile men. Idiopathic infertility is therefore a common diagnosis and it may be hypothesised that specific unrecognised molecular defects may be causing the problem. A variety of methods have been proposed to add to the diagnostic work-up of men with normal standard semen parameters. Telomeres (DNA sequences that cap and help preserve the ends of chromosomes) tend to decrease in length in somatic cells over time but this is not observed in germ cells. Recently there has been interest in the role of sperm telomere length (STL) in reproduction. It has been demonstrated that oligozoospermic men have shorter STL than normozoospermic men. Also, studies suggest that STL may be useful in prognostic evaluation in assisted reproduction.
To assess whether STL is a novel parameter and biomarker of sperm quality.
Data were collected from a cohort of 100 men with normal standard semen parameters consecutively recruited from September 2014 to June 2015 in an Ancroloy and Reproduction clinic in Italy.
STL was measured indirectly by quantitative polymerase chain reaction (PCR) using telomere/single-copy gene ratio; sperm DNA fragmentation was measured by terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling assay; and protamination by aniline blue staining.
Data were analysed to determine the relationships between STL, standard semen parameters and DNA fragmentation and protamination (all reported as means +/- SDs) using Pearson correlation or Spearman rank correlation.
The men had a mean age of 34 years (SD=8.6). Among standard semen parameters, STL was positively associated with progressive motility (r=0.46; p=0.004) and vitality (r=0.34; p=0.007). STL was significantly and negatively associated with sperm DNA fragmentation (r=-0.44; p=0.001) and significantly and positively associated with protamination (r=0.41; p=0.002). In other correlations, DNA fragmentation was negatively associated with protamination (P=0.0003) and progressive motility (P<0.0001).
The authors say this is the first study analysing in detail associations between STL and conventional semen parameters and they used validated methods to assess DNA fragmentation and protamination. The findings of significant correlations between STL and progressive motility and vitality add to previous data showing associations between STL and total sperm count and shorter STL in oligozoospermic and infertile men compared to normozoospermic and fertile men. Hypotheses aout the pathophysiological basis of the observed associations include the role of protamines in protecting DNA from damage and that DNA fragmentation may trigger telomere shortening independently of the normal shortening that occurs at the end of the cell cycle.
Further studies are needed but STL may be useful as an additional sperm parameter in the evaluation of the infertile male or as a prognostic biomarker in assisted reproduction.
Points to Note
- The findings support other work in suggesting that sperm telomere length may offer further information about the quality of sperm and could be a useful parameter to add to semen analysis, although more work is needed to assess its potential.
- This study only included normozoospermic men referred for semen analysis in a narrow age range; further studies should include a broader range of patients.
- The cause or effect relationships between sperm telomere length and sperm parameters is currently unknown and this study was not able to determine this.
- Statistical analysis only included correlations between variables. More sophisticated techniques will be needed to assess the value of sperm telomere length as a measure of sperm quality.
- As the assays for measuring telomere length are becoming simpler and quicker, investigating the role of STL in measuring sperm quality in semen analysis is probably warranted.