Fertility Road Issue 03

SCIENCE | sperm dna fragmentation
SPERM DNA
FRAGMENTATION
By Dr Preben Christensen,
from SPZ Lab in Denmark
© Sebastian Kaulitzki / shutterstock.com
Recently, there has been increased
emphasis on the evaluation of
sperm quality. Much of this has
been due a growing realisation
that a sperm or semen test is actually of
limited value.
Sperm, in essence, act as little more
than vehicles by which DNA is carried
from the male to the female egg. Only
very few make it to their goal, and along
the way a potentially damaging process is
undertaken, where the protein blocks
designed to protect the sperm can very often
fail, leaving DNA susceptible to damage
and at risk of becoming fragmented.
There have been significant recent studies
into DNA fragmentation, and I have outlined
below the latest findings into an area of
fertility previous not given the attention it
perhaps deserves.
Historically, infertility has been a problem
that was believed to originate solely from
the woman. About 300 years ago, people
were pretty sure that “what father does
is always right!” The Dutchman Nicolas
Hartsoecker was one of the first to look at
a sperm sample under the microscope. He
drew a ‘Homunculus’, a small child in the
head of the sperm cell, and the belief was
that anything produced by the man would
have to be perfect.
This example tells us that one of our
problems when trying to understand new
research is our entire perception of the
problem! Thus, approximately 75% of all
women believe that it can only be the
woman that is the problem when a fertilised
egg does not implant in the uterus.
And that is despite the fact that nowadays
most men are aware of the fact that
sperm quality can be a problem. Indeed, in
approximately every fourth childless couple,
the reason for the involuntary childlessness
is DNA fragmentation in the sperm cells.
The vast majority of these men have
normal sperm quality, the problem being
that you cannot see when the genome (the
DNA) is not packed properly in the sperm
cell. The concentration of sperm cells can
be fine, they are swimming properly and
can easily fertilise the egg. However, the
fertilised egg is still doomed to perish. The
reason for this is that the genome from the
sperm cell has been damaged (fragmented)
during the long journey to the egg. The
egg might be able to carry out small
repairs of the sperm cell’s DNA, but major
damage is fatal for the further development
of the egg. In other words, the woman’s
eggs might be perfectly fine – but with a
fragmented genome in the sperm cells, the
fertilisation will not result in a viable foetus.
The most extensive study carried out
so far regarding the significance of DNA
fragmentation in sperm cells was conducted
by Mona Bungum at Malmø University
Hospital and was published in 2007 in the
journal Human Reproduction. The study
was based on 998 treatment cycles, where
the couples received either IUI, IVF or ICSI
Historically, infertility has been a problem that
was believed to originate solely from the woman.
About 300 years ago, people were pretty sure
that “what father does is always right!”
treatment. Mona showed that the DNA
fragmentation index (DFI) was above 25 for
approximately 27% of the infertile couples
in her study. At this level itz is basically
impossible to get the wished-for child
through IUI treatment. For approximately
5% of the couples, the DFI was above 50.
At this level, IVF treatment will not have
the desired result either. In other words,
this is a very frequent problem.
It’s also something of a hidden problem,
because when the fertilised egg starts
splitting, the first breaks take place without
any influence from the genome of the sperm
cell. Not until there are eight cells does the
egg start drawing on information from the
sperm cell.
»
www.fertilityroad.com
59