Parkinson’s disease patients can find hope in a new treatment, thanks to breakthrough stem cell research that successfully replaces damaged nerves. Swedish researchers have figured out how to create motor neurons that become lost in the brains of Parkinson’s disease patients. They published their findings in the journal Cell Stem Cell.

Researchers from Lund University took human embryonic stem cells (hESC) from in vitro fertilization embryos and grew them into motor neurons. The neurons were transplanted into the brains of rats with Parkinson’s disease, and over the course of five months, their dopamine levels rose back to normal. There are currently one million individuals living with Parkinson’s disease in the United States, and 96 percent of them were diagnosed after the age of 50.

Parkinson’s is an incurable progressive disease that takes over your body, rendering you without control, according to the Parkinson’s Disease Foundation. It affects the nervous system and movement, causing tremors, stiffness, slow movements, impaired posture and balance, speech changes, and other life-changing symptoms. This tumbling loss of motor skills is partially caused by the death of nerve cells that control dopamine in the brain. Researchers don’t know exactly why the chemical messenger begins to die, but once dopamine levels decrease, the brain loses the ability to regulate critical muscle movements.

"Our study represents an important milestone in the preclinical assessment of hESC-derived dopamine neurons and provides essential support for their usefulness in treating Parkinson's disease," said the study’s lead author Malin Parmar of Lund University, in a press release.

There are medications available for Parkinson’s patients, however, none have been able to successfully reverse the effects of the disease. This research is only the first step toward new treatment, but it's a huge and important finding in Parkinson’s disease research. Scientists still need to see if they can reverse Parkinson’s symptoms in animals on a long-term basis. Then, they need to see if they can replicate their findings in humans. If laboratory testing passes in the future, researchers may be able to use tissue from aborted human fetuses — one of the few options, since there's a limited availability of cells. This would help make stem cell replacement a realistic and therapeutic option for Parkinson’s patients who need enough hESC to make the treatment effective.

Roger Barker, of Addenbrooke’s Hospital and the University of Cambridge, reviewed the study and warned that the researchers must be thorough in their process, without rushing into clinical testing. "This involves understanding the history of the whole field of cell-based therapies for Parkinson's disease and some of the mistakes that have happened," Barker said. "It also requires a knowledge of what the final product should look like and the need to get there in a collaborative way without being tempted to take shortcuts, because a premature clinical trial could impact negatively on the whole field of regenerative medicine."

Source: Parmar M, Grealish S, Diguet E, Kirkeby A, Mattsson B, and Heuer A, et al. Human ESC-Derived Dopamine Neurons Show Similar Preclinical Efficacy and Potency to Fetal Neurons when Grafted in a Rat Model of Parkinson’s Disease. Cell Stem Cell. 2014.