- •Sperm telomeres were shorter in older OAZ men than in older NZ men.
- •Younger OAZ men had a higher number of short telomeres in spermatozoa and a tendency towards lower TERC accumulation.
- •Mean telomere length in PBMC was shorter in younger OAZ patients, who also showed a higher percentage of short telomeres.
- •Positive correlations between STL and sperm count and motility were found in younger NZ men.
- •Spermatozoa from younger NZ accumulated lower TRF1 mRNA levels.
How do age and normo- or oligoasthenozoospermia affect telomere length dynamics in spermatozoa and blood?
Sperm and blood samples were collected from a cohort of 37 men aged 25 and under and 40 men aged 40 and over, with either normozoospermia (NZ) or oligoasthenozoospermia (OAZ). Telomere length was evaluated using quantitative fluorescence in-situ hybridization. Telomerase mRNA (TERC and TERT) and shelterin (TRF1) gene expression were analysed using quantitative real-time polymerase chain reaction. TRF1 protein immunoreactivity was also evaluated using immunofluorescence.
Mean sperm telomere length (STL) increased with age in the NZ group; older NZ men accumulated the longest telomeres (P < 0.001). In peripheral blood mononuclear cells (PBMC), mean telomere length decreased with age in NZ groups, although not reaching statistical significance. Interestingly, the younger OAZ group had the shortest mean telomere length (versus young NZ, P = 0.0081; versus old NZ, P = 0.0116; versus old OAZ, P = 0.0009) and accumulated the highest percentage of short telomeres compared with the other groups (overall P = 0.0017). Analysis of TERC and TERT mRNA expression in spermatozoa and PBMC did not show significant differences among groups. Statistically significant positive correlations were found between STL and seminal parameters in younger NZ men (P = 0.009 for sperm count and P = 0.007 for total progressive motility). Protein immunoreactivity of TRF1 in blood was not significantly different in all groups analysed.
The OAZ group did not show the increase of STL with age that is seen in NZ individuals, suggesting that telomere length elongation mechanisms fail in OAZ patients. In PBMC, younger OAZ individuals showed significantly shorter mean telomere length, suggesting that this parameter could be a good biomarker of OAZ in younger OAZ patients. Telomerase gene and TRF1 mRNA expression and TRF1 protein immunoreactivity did not differ significantly between groups, and so these factors cannot be used as OAZ biomarkers.
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Carlos Balmori is Chief of the Urology and Andrology Department at IVI-RMA Madrid. In 2019, he started his PhD in telomere research at the Rey Juan Carlos University and IVI-RMA Madrid. His research interests focus on biomarkers of male fertility for diagnosis and treatment, as well as semen quality improvement techniques.
Telomere maintenance was altered in oligoasthenozoospermic (OAZ) men, leading to an impairment of sperm telomere length elongation with age. Younger OAZ patients had shorter telomeres in blood. This opens up the possibility of using peripheral blood mononuclear cell telomere length as a biomarker of OAZ.
Published online: October 24, 2021
Accepted: October 15, 2021
Received in revised form: September 10, 2021
Received: July 16, 2021Declaration: The authors report no financial or commercial conflicts of interest.
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