High blood pressure is a leading risk for women and babies during pregnancy. Now researchers can stop it in its tracks by turning off the genes in the placenta.The technique, called RNA silencing (reducing gene expression) has normalised blood pressure in a small trial in monkeys.
High blood pressure leads to a condition known as pre-eclampsia that affects 10 per cent of pregnancies. This new approach targets gene activity and is less unlikely to cause unexpected side-effects because it’s a highly specific treatment.
The technique destroys short strands of DNA-like molecules that are the blueprints for making proteins called RNA. For pre-eclampsia, it targets the blueprint for one particular placenta protein, FLT, which raises blood pressure.
Researchers tested this approach in a mild version of pre-eclampsia in baboons. They induced pre-eclampsia in nine apes, prompting their placentas to pump out more of the FLT protein. They then injected their RNA therapy into three baboons.
Within two weeks, the placentas of these baboons made less FLT, and they showed signs of lower blood pressure and less kidney damage than the six untreated animals.
The offspring of these three apes seemed normal, but they were born a little smaller than average.
Researcher Melissa Moore says this could be a result of reducing blood pressure, so they need to do further animal studies to find the optimal therapy dose.
Another RNA therapy for pre-eclampsia that targets a different protein involved in blood pressure is currently being tested in rats.
It is being developed by Irish biotech firm Alnylam, which brought the first RNA therapy to market, designed against a rare hereditary form of nerve damage.
RNA therapy is safe for pre-eclampsia because the treatment does not seem to cross the placenta, making it less likely to affect the foetus.
Also, a single injection can target a particular protein for several weeks, making it an appealing treatment in countries where regular medical care can be difficult.
Pre-eclampsia can lead to kidney and liver damage, seizures and stroke.
When severe, the only treatment is to deliver the baby, no matter how early in the pregnancy, so women face choosing between their own health and the baby.
When it occurs, the placenta isn’t effective enough. To compensate, it releases proteins into a woman’s blood to raise her blood pressure, boosting the delivery of nutrients and oxygen to the foetus.
But these proteins can push the woman’s blood pressure to dangerously high levels.
Progress in developing treatments has been slow, partly because pharmaceutical firms are nervous about the risk of causing birth defects.