For the first time ever, researchers have managed to rid monkeys with Parkinson’s disease of their symptoms by transplanting adult uterine stem cells.

Working with monkeys that had been induced with Parkinson’s, a team of researchers from the Yale School of Medicine and the National Institutes of Health used stem cells — cells that have the ability to take on the characteristics of any tissue cell — taken from the uteri of eight female monkeys and injected them into the brains of three male monkeys. While certain drug treatments have been found to treat Parkinson’s symptoms in some patients, stem cell treatments have been shown to treat underlying causes of the disease.

Furthermore, many patients with severe Parkinson’s do not respond to current pharmacological treatments, but stem cells hold the potential of working for all Parkinson’s patients. The study was published in the Journal of Cellular and Molecular Medicine on Oct. 6.

“I don’t want to over-sell stem cells. We don’t know how effective it will be,” said Hugh Taylor ’83, professor of obstetrics, gynecology and reproductive sciences at the Yale School of Medicine and the study’s senior author. “We’re a few years off, but not 10 years off.”

According to Levent Mutlu, a postdoctoral fellow in the School of Medicine’s obstetrics and gynecology department and one of the study’s lead authors, using uterine stem cells means scientists can sidestep the ethical concerns that often arise in studies using embryonic stem cells. Unlike the latter, uterine stem cells do not come from terminated embryos.

Gene Redmond, professor of psychiatry and neurosurgery at the Yale School of Medicine and one of the study’s authors, said that though embryonic stem cells have already been shown to be effective in treating advanced stages of Parkinson’s, the ethical dilemmas associated with them make them prohibitive to use.

Additionally, unlike bone marrow stem cells — which are extracted via an extremely painful process — harvesting uterine stem cells is as simple as performing a biopsy and does not require the use of general anesthetic. Furthermore, partially differentiated cells, unlike their undifferentiated counterparts, have never been found to cause brain tumors, Taylor said.

“We weren’t sure how far we’d have to go when differentiating the cells before transplanting them,” Taylor said. “It turns out if you differentiate too far, the new cells don’t migrate where they are supposed to go. They don’t make the connections they are supposed to make. Instead if you inject undifferentiated stem cells and let them do the final differentiation steps in the intact brain, they do a lot better. It surprised us that we had to use these relatively undifferentiated cells.”

Taylor also said that although only half the population is female, hysterectomies are a common procedure, and it would not be difficult to set up a bank to pair patients with immunologically-matched donors.

The researchers are now in the process of gathering funds to do a larger study with monkeys with severe Parkinson’s, Taylor said. Going forward, the researchers will be faced with taking care of monkeys that cannot take care of themselves. While the monkeys in this study were essentially asymptomatic, future subjects will have an advanced form of the degenerative disease.

He added that the study’s findings are a harbinger of breakthroughs to come.

According to the Parkinson’s Disease Foundation, approximately 60,000 Americans are diagnosed with Parkinson’s every year.

Clarification: Oct. 20

A previous version of this article used a quote from one of the study’s lead authors stating that an alternative cure for Parkinson’s had been found. In fact, the results are only preliminary, and a cure for the disease has not yet been discovered.