New research from McLean Hospital and the Harvard Stem Cell Institute has shown that stem cell therapy reduces seizures in mice.

Researchers used an animal model to transplant seizure-inhibiting, human embryonic stem cell-derived neurons into the brains of mice that had a common form of epilepsy. Half of the mice that received the transplanted neurons no longer had seizures, while the other half experienced a significant drop in seizure frequency.

The transplanted neurons integrated into the mouse brains and began to receive neuronal activity. The neurons then released GABA, an inhibitory response that reversed the electrical hyperactivity that causes seizure.

“Previous studies showed increasing inhibition in the epileptic brain can help control the seizure and also a lot of anti-epilepsy drugs are mimicking this GABA, so many of them worked by binding to the GABA receptors,” researcher Sangmi Chung, assistant professor of psychiatry at Harvard, told

Researchers initially set out to test the functionality of human neurons, but later decided to test their effect on epilepsy because it is such a devastating disease. About 30 percent of people do not respond to seizure drugs and one out of 26 people will be affected by seizures in their lifetime, Chung said.

Over 65 million people worldwide are affected by epileptic seizures, which can cause convulsions, loss of consciousness and other neurological symptoms. Patients are treated with anti-seizure drugs, and may choose to have a portion of their brain removed.

Because mouse cells mature more quickly than human cells— within weeks instead of years— it was unclear how long a stem cell transplant in a human would take before becoming effective, Chung noted.

“If we compare it with the mouse [model], we believe it will be years, not weeks,” she said.

However, the study found that, even without full maturation, the cells integrated into the epileptic mouse brains, receive signals and release GABA, therefore preventing seizures.

“I think it’s really good news in terms of transplantation— even maturing, not fully mature [cells] still work,” Chung said.

The exact mechanisms of how seizures are generated is not completely clear, but looking at the removed sections of brain from epileptic patients has shown that the attacks involve interneuron death.

More tests are needed before the study goes to a clinical trial, including primate trials and finding a process to purify neurons, Chung said.

“Hopefully, especially considering the really desperate population of patients, hopefully it will move fast,” she said.