Sperm telomere length as a parameter of sperm quality in normozoospermic men

Abstract

Study question: Could sperm telomere length (STL) represent a novel parameter and biomarker of sperm quality?

Summary answer: STL is associated with standard semen quality parameters and, more importantly, it is significantly associated with levels of DNA fragmentation and sperm protamination.

What is known already: Telomeres are fundamental for genome integrity. Recent studies have demonstrated that STL increases with age and men with oligozoospermia have shorter sperm telomeres than normozoospermic men.

Study design, size, duration: Cohort study conducted from September 2014 to June 2015 on 100 subjects with normal standard semen parameters.

Participants/materials, setting, methods: STL was measured indirectly by quantitative polymerase chain reaction using telomere/single-copy gene ratio, sperm DNA fragmentation by terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling assay and protamination by aniline blue staining. Data were analyzed for determining the relationships between STL, standard semen parameters and DNA fragmentation and protamination.

Main results and the role of chance: Among standard semen parameters, STL was positively associated with progressive motility (P = 0.004) and vitality (P = 0.007). STL was significantly and negatively associated with sperm DNA fragmentation (P = 0.001) and significantly and positively associated with protamination (P = 0.002). The role of chance was limited and the findings have biological relevance and a pathophysiological explanation.

Limitations, reasons for caution: For the present study, we deliberately selected only men with normozoospermia to better analyze whether STL might represent a biomarker of sperm quality beyond traditional sperm parameters. Additional studies in proven fertile men with normal sperm parameters are needed.

Wider implications of the findings: The measurement of STL is a simple and rapid method that offers further information about the quality of sperm. The results of this study demonstrate that STL could be considered as an additional sperm parameter and opens new perspectives in the evaluation of the infertile male. Additional studies will clarify the significance of this parameter also as a prognostic biomarker in assisted reproduction.

Study funding/competing interests: No external funding was either sought or obtained for this study. There are no conflicts of interest to be declared.

Keywords: DNA fragmentation; male infertility; protamination; sperm quality; sperm telomere length.