Sperm DNA methylation landscape in infertile men with clinical varicocele: unravelling the treatment effect.

PURPOSE: Varicocele has been associated with reduced male fertility potential. Treatment modalities for varicocele improve semen parameters, yet more than 50% of cases remain infertile. Varicocele-induced heat and hypoxia stress may cause aberrant epigenetic modifications, possibly leading to abnormal sperm functions. This study aims to investigate the genome-wide sperm DNA methylation alterations in infertile men with clinical varicocele and evaluate the effect of varicocele treatment on methylation and fertility status.

METHODS

This study includes 30 healthy fertile men and 50 infertile men with clinical varicocele. Whole genome bisulfite sequencing (WGBS) was employed to identify differentially methylated CpG (DMC) sites in sperm genomic DNA of the infertile men with varicocele compared to the fertile controls. DMCs located within genes associated with spermatogenesis and sperm functions were selected for validation in larger study population by pyrosequencing. Varicocele group were followed up after 3 months of either antioxidant treatment or varicocelectomy, and sperm DNA methylation changes were evaluated. Participants were monitored for 1 to 2 years following treatment to evaluate their fertility status.

RESULTS

From WGBS analysis, a total of 6414 DMCs and 1484 differentially methylated genes (DMGs) were identified. Signalling pathways involved in spermatogenesis process and sperm functions were enriched in the pathway analysis. Selected DMC within gene H2AX was significantly hypermethylated, and CDKN1B and BCR were hypomethylated in varicocele study population. However, after 3 months of varicocele treatment (both modes), notable restoration could only be observed in H2AX and CDKN1B DMCs. 20% of the follow-up patients achieved fertility after varicocele treatment and demonstrated a reversal of DNA methylation alterations.

CONCLUSION

This study highlights the altered sperm DNA methylation landscape and its possible implications on altered spermatogenesis and sperm function in clinical varicocele cases. It also presents insights into the possibility of restoration of altered DNA methylation levels following varicocele treatment.