Neurons derived from stem cells.Credit: Silvia Riccardi/SPL

Currently, more than 10 million people worldwide live with Parkinson’s disease (PD). By 2020, in the US alone, people living with Parkinson’s are expected to outnumber the cases of multiple sclerosis, muscular dystrophy and Lou Gehrig’s disease combined.

There is no cure for Parkinson’s and treatment options consist of medications that patients ultimately develop tolerance to, or surgical therapies that are expensive. Therefore, therapeutic options that offer long-lasting treatment, or even a cure, are essential for treating PD.

Luckily for patients, Jun Takahashi’s team at Kyoto University has pioneered a stem cell based therapy for PD patients.

To understand their treatment strategy, however, we first have to understand what causes this disease. Parkinson’s results from decreased numbers of neurons that produce dopamine, a molecule that helps control muscle movements. Without proper dopamine production, patients experience a wide range of movement abnormalities, including the classic tremors that are associated with PD.

The current treatment options only target the symptoms, as opposed to the root cause of the disease. Takashi’s group decided to go directly to the source and improve dopamine production in these patients by correcting the dopaminergic neuron shortage.

The scientists harvested skin cells from a healthy donor and reprogrammed them to become induced pluripotent stem cells (iPSCs), or stem cells that become any type of cell. These iPSCs were then turned into the precursors of dopamine-producing neurons and implanted into 12 brain regions known to be hotspots for dopamine production.

The procedure was carried out in October and the patient, a male in his 50s, is still healthy. If his symptoms continue to improve and he doesn’t experience any bad side effects,  he will receive a second dose of dopamine-producing stem cells. Six other patients are scheduled to receive this same treatment and Takashi hopes that, if all goes well, this type of treatment can be ready for the general public by 2023.

This treatment was first tested in monkeys, where the researchers saw that not only did the implanted stem cells improve Parkinson’s symptoms and survive in the brain for at least two years, but they also did not cause any negative side effects.

This is only the third time iPSCs have been used as a treatment option in humans. The first was for macular degeneration in 2014.

CIRM is funding a similar, albeit earlier-stage program, with Jeanne Loring at Scripps.