Thursday November 27 2008
Treating Down’s syndrome in the womb “could help prevent some of the brain damage caused… before the child enters the world”, according to The Daily Telegraph.
The newspaper says a “breakthrough” study showed that injecting pregnant mice with brain-protecting proteins reduced developmental delays similar to those found in children with Down’s syndrome.
While this small study in mice with a Down’s-like condition found that the treatment improved some of the motor and sensory skills tested, there was no change in other skills. It is also still unclear whether these results would be maintained in the long term.
Before this technology could be adapted and used as a medical treatment for humans, it would need much further animal testing including stringent safety tests before human trials. It is far too early to say whether this treatment will go on to help babies with Down’s syndrome.
Where did the story come from?
This study was conducted by Dr Laura Toso and colleagues from the National Institutes of Health and other research institutions in the US and Italy. It was published in the peer-reviewed medical journal, Obstetrics and Gynaecology.
The research was funded by the Division of Intramural Research Program, National Institutes of Health, Eunice Kennedy Shriver National Institute of Child and Human Development, and the National Institute on Alcohol Abuse and Alcoholism.
What kind of scientific study was this?
This was an animal study looking at whether treatment with brain-protecting proteins in the womb would have an effect on the development of mice in a model of Down’s syndrome.
In humans, Down’s syndrome is caused by carrying an extra partial or whole copy of a chromosome, known as chromosome 21. The researchers used a mouse model of Down’s syndrome, where mice carried an extra copy of about 55% of the genes found on human chromosome 21.
This mouse strain with extra genes is known as Ts65Dn, and these mice have similar developmental delays to those seen in people with Down’s syndrome. Currently there is no treatment available to prevent these delays in development.
The researchers were interested in two short pieces of protein (called peptides) that have been shown to improve survival of nerve cells in the laboratory and to protect against learning defects in a mouse model of fetal alcohol syndrome.
The researchers took 10 pregnant Ts65Dn mice and randomly assigned four mice to receive peptide injections, and six mice to receive control injections (salt water). Injections were administered into the space around the organs in the abdomen, but not directly into the womb.
Injections were given on days 8-12 of pregnancy (mouse pregnancies usually last between 18 to 21 days). The researchers also carried out the same experiment on normal (non-Ts65Dn) mice. The researchers were not told what treatments the mice were receiving or whether the mice were Ts65Dn mice or normal mice.
Once the offspring were born, the researchers weighed them and tested their development daily from five to 21 days of age. Developmental tests assessed their motor skills (muscle development, movement and coordination) and their sensory skills.
There were 10 different tests, five motor and five sensory (such as what day mice first opened their eyes, reflex tests, ability to climb a mesh screen and strength of grasp). Researchers used a scoring system to assess performance in each tests.
A total of 20 offspring from Ts65Dn mothers were tested; six from mothers treated with peptide, and 14 from control mothers. A total of 27 offspring from normal mothers were tested; nine from peptide treated mothers and 18 from control mothers. Once again, the researchers did not know which group the offspring belonged to during testing.
The researchers then compared the performance of the different groups of mice. They also looked at brain changes in the different groups of mice.
What were the results of the study?
The researchers found that the Down’s syndrome-like Ts65Dn offspring of untreated mothers had significant delays in achieving four of the five motor skills tested, and four of the five sensory skills when compared to the offspring of normal mice.
However, Ts65Dn offspring from mothers treated with the peptide mixture showed no delay in achievement of three of these four delayed motor skills, and one of these four delayed sensory skills.
Offspring from normal mice who had been treated with the peptide mixture achieved four of the five motor skills and two of the five sensory skills earlier than offspring of untreated normal mice.
What interpretations did the researchers draw from these results?
The researchers concluded that “prenatal treatment with (the peptide mixture) prevented developmental delay… in Down’s syndrome”.
What does the NHS Knowledge Service make of this study?
This small study in a mouse model of Down’s syndrome has highlighted the possibility of improving development with treatments in the womb. It is worth noting that the treatment did not improve all of the skills tested, and that the mice were only followed up for a relatively short period of time.
It is unclear whether the improvements seen in mice would be seen in humans, and whether such improvements would significantly alter the impact of Down’s syndrome on the individual.
Much more research in animals will be needed before this treatment could be tried in humans. In particular, much more information on the safety and long-term effects of this treatment is needed.