RNA (Ribonucleic Acid) Interference is a way of “silencing a gene” to stop it from working properly, inhibiting a sperm from entering the egg. Researchers from Brigham and Women's Hospital in Boston have identified a gene called ZP3 which is active in eggs just before they are fertilized. ZP3 produces a protein which allows the sperm to bind to the surface of the egg. If this protein isn't there, the egg can't be fertilized. The Boston team “silenced” the ZP3 gene in mice, and found they could not get pregnant.
At present, there is no contraceptive drug that is non-hormonal and reversible. “What we are trying to do is to think about contraception in a new way. Obviously, there are going to be hurdles and it is going to take a lot of time, but the need is there and we think it can be achieved,” said Dr. Zev Williams when he presented the research to the conference.
According to Professor Bill Ledger, from the University of Sheffield, a lot of women still had side effects, even on the modern hormonal contraceptives. “This is a new concept. If it were available, I am sure a lot of people would want to take it.”
Most hormonal methods of birth control can cause nausea, headaches, and low sex drive. It can also slightly raise the risk of DVT (deep vein thrombosis) and strokes. They are designed to work by suppressing ovulation. However, in a small percentage of cases, ovulation may still take place. For some women, this may occur every single cycle. As a result, these contraceptives prevent pregnancy through a different method. Aside from suppressing ovulation, hormonal methods of birth control may also change the lining of the uterus so that implantation of a fertilized egg cannot take place. The embryo is then expelled from the body during the next menstrual period. These possibilities and side effects are causing controversy among women which make some of them avoid hormonal birth control altogether.
However, the production of this new contraceptive pill is still a decade away and may have its own side-effects. Researchers estimate that it will take about 10 years before clinical trials of RNA Interference contraceptive would be possible.
Obstacles need to be overcome and there is no guarantee that side-effects would completely eradicted, said Dr Martin Fabani, a researcher in the technique at Cambridge University. He even added that, RNA interference is fantastic and there was a big hype around it, but people are starting to see what we call 'off-target' effects - where the therapy has an unwanted effect elsewhere in the body. Every single application has some degree of off target effects.
The advantage of this research into ZP3 is that the gene appears to be active only in eggs prior to the moment of fertilization, and nowhere else in the body. It means that it could be switched off without necessarily affecting either the prior development of the egg and ovulation, or other parts of the body.
