The genetic integrity of the sperm is crucial for successful fertilization and normal embryo development. Sperm DNA fragmentation is a term used to denote when the genetic material within the sperm is abnormal, which in turn may lead to male subfertility and IVF failure. Conventional sperm examinations (i.e., semen analysis) done for sperm concentration, motility analysis and morphology assessment cannot assess the sperm at the molecular level and as result aid the detection of DNA fragmentation.
A number of sperm DNA fragmentation tests are available on the market, but the one used at the Reproductive Health Group, is the SpermComet test which is currently the most accurate than other tests such as SCSA and TUNEL.
Studies in the literature have shown that:
- High sperm DNA fragmentation does not impair fertilisation or embryo cleavage stages
- High sperm DNA fragmentation affects subsequent blastocyst development
- Higher the DNA fragmentation levels, higher the chances of failed assisted conception treatment and miscarriage
- Sperm DNA fragmentation is higher in subfertile men with abnormal sperm parameters
- Men with normal sperm parameters are also found to have high sperm DNA fragmentation
Advantages of the sperm DNA fragmentation test
- Provides a reliable analysis, beyond the routine semen sample assessment, of sperm DNA integrity that may help to identify men who are at risk of failing to initiate a healthy pregnancy
- Information helps in the clinical diagnosis, management and treatment of male infertility
- Prognostic value in assessing outcome of assisted conception treatment
High rates of sperm DNA fragmentation and pregnancy potential
- Normal, healthy pregnancies do occur in couples where the male partner has high percentage of sperm with fragmented DNA, although the chances are significantly reduced, as the percentage of sperm bearing low levels of DNA fragmentation is much lower
- Embryos derived from sperm with highly fragmented DNA have poor prognosis
- DNA fragmentation could result in initiation of apoptosis (natural cellular death) and mutations resulting in blastocyst arrest, miscarriage, abnormalities in the offspring and an increased susceptibility to childhood cancer
- Sperms with high DNA fragmentation fertilising younger oocytes than older oocytes carry a better prognosis of successful pregnancy, as they are much more efficient at DNA repair of defective sperm
Causes of Sperm DNA Fragmentation
In men, the major contributing factor for sperm DNA fragmentation is oxidative stress, which can be associated with one or more of the following:
- Elevated testicular temperature
- Recreational drugs use
- Environmental and occupational pollutants
- Advanced age
- Sperm cytoplasmic droplets
Indications for men who may benefit from the SpermComet test
- Unexplained Infertility
- Arrested Embryo Development
- Poor Blastocyst Development
- Multiple Failed IVF/ICSI treatment
- Recurrent miscarriage in partner
- Advanced age
- Poor semen parameters
- Exposure to harmful substances
Treatment of high sperm DNA fragmentation
It depends essentially on the cause. If the damage is caused by free radicals, a change in lifestyle and diet designed to protect against oxidative stress may help reduce the levels of DNA fragmentation. Other treatment options include:
- Antibiotics in the co-existence of an infection
- Life style changes – drugs, smoking and occupation
- Diet – fresh foods, particularly those containing antioxidants or vitamin C & E
- Varicocoele repair
- Testicular aspiration of sperm (DNA damage occurs at the post-testicular level, hence testicular sperm may have a better DNA integrity than ejaculated sperm)
- ICSI rather than IVF
Initiatives to reduce the levels of fragmentation can be assessed by undertaking a second test three months later.
What is the SpermComet test?
Is a second generation sperm DNA test. It detects the sperm with DNA damage and also tells how much DNA damage each sperm have. A SpermComet test result of 45% means that there is an average of 45% damage in each sperm that was assessed. Sperm are stained with a fluorescent probe that interacts with the DNA molecule. The fluorescence signal changes when the DNA is fragmented, and this is monitored using a flow cytometer.
What do the results mean?
The results are reported showing the following categories of fertility potential:
≤ 24% sperm DNA damage: no significant fertility problem
> 25% ≤ 49% sperm DNA damage: increased risk of fertility problem
> 50% sperm DNA damage: high risk of fertility problem and IVF treatment failure
Spontaneous and IVF pregnancies are possible with abnormal sperm DNA fragmentation, but the higher the sperm DNA damage the greater the risk ofmiscarriage.