Effects of age on DNA double-strand breaks and apoptosis in human sperm.
OBJECTIVE
This study was designed to explore the relationship between men's age and DNA damage and apoptosis in human spermatozoa.


METHODS
Semen samples were collected from men between the ages of 20 and 57 years. Sperm DNA double-strand breaks were assessed using the neutral microgel electrophoresis (comet) assay, and apoptosis was estimated using the DNA diffusion assay.


METHODS
Academic medical center.


METHODS
Sixty-six men aged 20 to 57 years were recruited from infertility laboratory and general populations and consented to donate a semen sample. Recruitment was determined by time and day of analysis; the only exclusions were for azoospermia, prostatitis, or prior cancer therapy.


METHODS
None.


METHODS
DNA damage and apoptosis in human sperm.


RESULTS
Age correlated with an increasing percentage of sperm with highly damaged DNA (range: 0-83%) and tended to inversely correlate with percentage of apoptotic sperm (range: 0.3%-23%). For example, percentage of sperm with highly damaged DNA, comet extent, DNA break number, and other comet measures was statistically significantly higher in men aged 36-57 years than in those aged 20-35 years, but percentage apoptosis was statistically significantly lower in the older group. Semen analysis showed percentage motility to be significantly higher in younger age groups.


CONCLUSIONS
This study clearly demonstrates an increase in sperm double-stranded DNA breaks with age. Our findings also suggest for the first time an age-related decrease in human sperm apoptosis. These novel findings may indicate deterioration of healthy sperm cell selection process with age.
Singh
Narendra P
NP
Department of Bioengineering, University of Washington, Seattle, Washington 98195-7962, USA. narendra@u.washington.edu
Muller
Charles H
CH
Berger
Richard E
RE
D000328:Adult; D000367:Age Factors; D000375:Aging / Q000235:genetics*; D017209:Apoptosis / Q000502:physiology*; D004249:DNA Damage; D006801:Humans; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012661:Semen / Q000166:cytology; D013094:Spermatozoa / Q000166:cytology / Q000502:physiology*