DNA Breakage and Failure of Apoptosis in Sperm as men age

Fertility and Sterility
Volume 80, Issue 6 , December 2003, Pages 1420-1430






doi:10.1016/j.fertnstert.2003.04.002
Copyright © 2003 American Society for Reproductive Medicine. Published by Elsevier Science Inc.
Male factor
Effects of age on DNA double-strand breaks and apoptosis in human sperm*1

Narendra P. Singh M.B.B.S., M.S.a, , , Charles H. Muller Ph.D.b and Richard E. Berger M.D.b

a Bioengineering, University of Washington, Seattle, Washington, USA
b Department of Urology, University of Washington, Seattle, Washington, USA

Received 6 February 2003; revised 30 April 2003; accepted 30 April 2003. ; Available online 3 December 2003.




Abstract
Objective
This study was designed to explore the relationship between men's age and DNA damage and apoptosis in human spermatozoa.

Design
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.

Setting
Academic medical center.

Patient(s)
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.

Intervention(s)
None.

Main outcome measure(s)
DNA damage and apoptosis in human sperm.

Result(s)
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.

Conclusion(s)
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.

Author Keywords: DNA double-strand breaks; apoptosis; human sperm; aging; Comet assay


Corresponding author. Reprint requests: Narendra P. Singh, M.B.B.S., M.S., Department of Bioengineering, Box 357962, University of Washington, , Seattle, Washington 98195-7962, , USA (FAX: 206-685-2060).

*1 Supported by the Paul G. Allen Foundation for Medical Research.