"The origin of DNA fragmentation can be multi factorial," said Mr. Avendao. "Oxidative stress (mainly due to reproductive tract infections) and apoptosis are the most studied, but other factors as age, smoking, exposure to air pollution and abnormal testicular warming are believed to increase the proportion of sperm DNA fragmentation."
The researchers are now applying DNA fragmentation evaluation to couples with male factor infertility. "Our preliminary results using this new evaluation method show a clear negative correlation between the percentage of DNA fragmented sperm and the embryo quality and pregnancy outcome," said Mr. Avendao.
"Different research groups have shown that in addition to affecting normal embryonic development, fertilisation with damaged spermatozoa resulting in a live-born infant can be associated with increased chromosomal abnormalities, minor or major birth defects, and even childhood cancer," said Mr. Avendao. "Our work has shown that normal sperm morphology alone should not be used as the unique attribute for the selection of sperm for ICSI. New methods that allow an accurate separation of sperm with intact DNA should be sought."
Sperm biology has received less attention since the introduction and success of the ICSI technique, say the researchers. "While the ICSI procedure bypasses the natural sperm selection, we believe that the deleterious effects of injecting a DNA-fragmented sperm should and can be avoided. Further research into sperm biology is essential if we are to avoid problems in the future," said
|Contact: Mary Rice|
European Society for Human Reproduction and Embryology