Deoxyribonucleic acid methylation abnormalities at imprinted loci in oligospermic and azoospermic men.

OBJECTIVE

To assess deoxyribonucleic acid (DNA) methylation at imprinted and repetitive genomic regions in ejaculated and testicular sperm from men with oligospermia, azoospermia, and those undergoing vasectomy reversal (VR), compared with fertile controls.

DESIGN

Observational case-control study.

SUBJECTS: Samples were obtained from 68 men, including 29 infertile men (18 oligospermic [5-15 million/mL], 11 severely oligospermic [<5 million/mL]) and 20 fertile controls with confirmed natural conceptions. Testicular tissue was collected from 11 azoospermic men (7 obstructive azoospermia [OA], 4 nonobstructive azoospermia [NOA]) and 8 men with prior paternity undergoing VR.

EXPOSURE: Sperm DNA methylation at four imprinted genes (H19, GTL2, MEST, and LIT1) and one repetitive element (LINE1).

MAIN OUTCOME MEASURES: Methylation levels at CpG sites determined by bisulfite pyrosequencing.

RESULTS

The H19 was significantly hypomethylated only in severe oligospermia compared with fertile controls, whereas other groups showed nonsignificant trends with overlapping distributions. In contrast, MEST was significantly hypermethylated in oligospermic, azoospermic, and VR groups compared with fertile controls. No significant differences were observed for GTL2, LIT1, or LINE1.

CONCLUSION

The DNA methylation abnormalities in sperm are locus-specific and vary across infertility phenotypes. MEST alterations were consistent across groups, whereas H19 changes were limited to severe oligospermia. Similar methylation patterns in testicular sperm from azoospermic and VR groups suggest that epigenetic alterations may reflect the testicular environment or obstruction, or differences between testicular and ejaculated sperm.