A team of stem cell scientists has identified the biological mechanisms of Parkinson’s disease and recreated a model of the disease in a dish.

Researchers at The New York Stem Cell Foundation (NYSCF) Research Institute studied a pair of identical twins— one with Parkinson’s and one without— as well as another unrelated Parkinson’s patient and four healthy control subjects to observe key characteristics of the disease. After comparing the individuals’ biological factors, they noticed differences in the patients’ neurons’ ability to produce dopamine. Dopamine production is deficient in Parkinson’s disease.

"The unique scenario of identical twins, one with this disease and one without, allowed our scientists an unprecedented look into the mechanisms of Parkinson's disease," Susan L. Solomon, NYSCF chief executive officer, said in a news release. "Advanced stem cell research techniques allow us to push the boundaries of science and see what actually goes wrong at the cellular level, step by step during the disease process."

Parkinson’s disease affects an estimated 500,000 people in the United States, according to the National Institutes of Health (NIH). The average age of onset is 60, and the risk of developing it increases with age. Symptoms of Parkinson’s include tremor, shaking in the hands, arms, legs, jaw or head; impaired balance or postural instability; slowness of movement; and stiffness of the limbs and trunk.

There is currently no cure for Parkinson’s.

While the disease is moderately hereditary, scientists have yet to fully understand the mechanisms of inheritance. The researchers note the DNA mutations that produce the enzyme glucocerebrosidase (GBA) have been linked to a five-fold increased risk of developing Parkinson’s, but only 30 percent of people with this mutation have been shown to get the disease by age 80. This suggests that genetic and non-genetic factors cause Parkinson’s. In studying the identical twins, scientists were able to analyze these mechanisms.

The scientists made induced pluripotent stem (iPS) cells from skin samples from both twins to generate a cellular model of Parkinson’s in a dish, recreating the outstanding features of the disease— specifically the dopamine and a-synuclein deficiency.

Scientists saw that the neurons from the twin affected by Parkinson’s produced less dopamine and had higher levels of an enzyme called monomine oxidase B (MAO-B), as well as a poorer ability to connect with each other, compared to the twin that did not have the disease.

The findings suggest a possible therapy for Parkinson’s: treating neurons with molecules that reduce the activity of MAO-B and GBA, while normalizing α -synuclein and dopamine levels.

"The subject of Parkinson's disease discordant twins gave us an incredible opportunity to utilize stem cell models of disease in a dish to unlock some of the biological mechanisms of disease," Dr. Scott Noggle, NYSCF vice president, said in the news release. "Working with these various different groups and scientists added to the depth and value of the research and we hope our findings will be applicable to other Parkinson's disease patients and other neurodegenerative disorders."

The study was published in the Nov. 6 issue of the journal Cell Reports.