Photo/IllutrationThe Asahi Shimbun

Pregnant mice whose fetuses were induced with Down syndrome produced offspring with inhibited symptoms after being administered a chemical compound discovered by Japanese researchers.

The finding, published Sept. 5 in the Proceedings of the National Academy of Sciences, could have important ramifications for expectant mothers, said Masatoshi Hagiwara, a chemical biology professor at Kyoto University, who headed the research team.

He said the lab tests led to a "symptomatic improvement" in baby mice.

Down syndrome is mainly caused by the presence of an extra copy of the human chromosome 21 and is a common cause of intellectual disabilities in humans. A healthy individual only has a pair of each type of 23 chromosomes.

The excessive activity of a gene in those suffering from the disorder results in mental disabilities, congenital heart diseases and other health problems.

While human fetuses with Down syndrome can be diagnosed, there is no radical cure for the disorder.

Inspired by the fact that a gene to inhibit the proliferation of nerve cells becomes excessively active in Down syndrome patients, the researchers tried to find a chemical that can inhibit the activity of the gene to help nerve cells’ proliferation.

The scientists orally administered the compound to pregnant mice and confirmed that the brains of newborn mice with Down syndrome grew properly.

They also checked the cognitive abilities of 12 baby mice suffering from the disorder through maze testing and found their capabilities were comparable to those of healthy mice.

The team also discovered other mice that were given the compound produced more nerve cells.

The researchers added the chemical to induced pluripotent stem (iPS) cells created from cells of Down syndrome sufferers. They said this helped nerve cells proliferate in human cells as well.

Although the compound cannot cure the chromosomal abnormality itself, the finding could lead to the development of prenatal treatment to deal with Down syndrome.

Hagiwara said he holds high expectations for new therapeutic methods, but cautioned that extensive trials would be necessary before commercializing the technique.

“There are high hurdles to overcome before we administer the compound to pregnant women," he said, citing the need to ensure a safe clinical environment and win social acceptance for the treatment. “We are looking to make it clinically available first as a drug for cerebral infarction and other diseases.”

More than 90 percent of expectant mothers underwent abortions after prenatal checks based on a new type of blood test turned up Down syndrome or other chromosomal abnormalities in the fetuses.

The development of a prenatal Down syndrome treatment would give parents another choice beyond giving birth or having an abortion.

“The compound has been tested only in mice and human cells, and its effects on mothers, as well as appropriate doses, when to administer it and other long-term factors need to be studied,” said Rika Kosaki, a senior doctor at the Division of Medical Genetics of the National Center for Child Health and Development.

(This article was written by Jin Nishikawa and Roku Goda.)