Stem Cells To Treat Parkinson’s?

Promising new research has shown positive results from using stem cell therapy to treat Parkinson’s disease. Researchers have been encouraged by their findings, which are also inspiring hope in people living with Parkinson’s , a progressive neurodegenerative disorder.

The studies have involved transplanting stem cells into the brains of people with Parkinson’s to repair or replace the dopamine damaged by the disease. Stem cells are immature cells capable of developing into various cell types, including neurons that produce dopamine.

Parkinson’s disease is caused by the gradual loss of nerve cells in the brain that make dopamine, a hormone that controls movement and muscle tone and influences learning, mood, and attention. As nerve cells die, people with Parkinson’s develop symptoms such as tremors, stiffness, slow movement, and difficulty with balance. About one million people in the United States are living with Parkinson’s, while more than 150,000 people in the United Kingdom (UK) have the disease.

Parkinson’s is treated primarily with levodopa, a medication that helps to increase dopamine levels in the brain. Levodopa, however, becomes less effective over time and may lead to side effects, such as dyskinesia, a movement disorder marked by involuntary and uncontrollable muscle movements.

Stem cell therapy aims to slow the progression of Parkinson’s, lessen the disease’s symptoms, and repair the brain damage caused by the disease.

The American Parkinson’s Disease Association noted that researchers have been working on developing stem cell treatments for Parkinson’s for decades, and there are two “crucial steps” to this process:

• Encouraging these stem cells to develop into nerve cells that produce dopamine.

According to the association, several types of stem cells can be considered for cell-based Parkinson’s treatments, such as embryonic stem cells derived from a human embryo, typically at a very early developmental stage, and induced pluripotent stem cells that are created from adult skin or blood cells that have been reprogrammed to revert to an embryonic state.

Parkinson’s UK and other organizations worldwide supporting and funding research related to Parkinson’s disease have been pleased with stem-cell therapy’s early clinical trial results.

“Stem cell therapies hold huge promise for slowing, or even reversing, the progression of Parkinson’s as they could be used to replace lost brain cells to potentially restore lost function,” Claire Bale, associate director of research at Parkinson’s UK, told The Independent. “However, making stem cell therapies a reality has proven challenging.”

One reason this type of therapy for Parkinson’s has been challenging is that stem cells have the potential to become so many different kinds of cells, Dr. Lorenz Studer, director of the Center for Stem Cell Biology at the Sloan Kettering Institute in New York, told NPR. He said it takes “just the right mix of chemicals at just the right time to produce a neuron that makes dopamine.” Studer and his team have been studying stem cells for the treatment of brain diseases for over 25 years.

“It took us nearly 10 years to figure out the recipe, how to make specifically those dopamine cells,” he told NPR. “It took us another 10 years to have the product that we would dare to put into patients.”

Investigators say they also needed to find a way to create and package large numbers of stem cells that could be easily delivered to surgeons. So, researchers developed techniques that allowed them to freeze stem cells until needed.

Results of Stem-Cell Clinical Trials

Two small clinical trials have been conducted to test the safety and tolerability of injecting cells into participants with Parkinson’s. The “hotly anticipated clinical trials” were described in the journal Nature as a “big leap in the field.” The journal published the studies in April.

One study involved 12 people with Parkinson’s in the United States and Canada. The treatment involved surgically injecting participants’ brains with either a low or high dose of bemdaneprocel, a stem-cell product developed by BlueRock Therapeutics.

The cells were derived from human embryonic stem cells, which researchers had coaxed into becoming immature brain cells known as neuron progenitors. They were injected into a structure on each side of the brain that was involved in movement. PET scans taken 18 months later showed the cells were producing dopamine, and some participants “experienced visible reductions in tremors,” the study said.

“The idea is to place these neuron progenitors right where you need them to connect with other neurons in the brain,” Dr. Viviane Tabar, a stem-cell scientist and chair of neurosurgery at Memorial Sloan Kettering Cancer Center, told NPR.

Not only was the cell therapy found to be safe, but the study also found that participants who received the high dose benefited more from the treatment than participants in the low-dose group.

A second study, conducted by researchers in Kyoto, Japan, used human-induced pluripotent stem cells derived from a patient’s own cells rather than an embryo. The cells were injected into both sides of the brains of seven participants. Researchers discovered that the transplanted cells produced dopamine, and the patients seemed to experience decreased symptoms.

Patients in the two studies reported no serious problems.

New Study Uses Patients’ Own Stem Cells

Researchers at Mass General Brigham recently launched the first phase of a groundbreaking treatment that reprograms an individual’s own stem cells to replace dopamine neurons in the brain damaged by Parkinson’s.

Researchers say this is the first-of-its-kind trial using an “autologous transplantation approach.” Autologous stem cells are undeveloped cells that can become different types of cells. These cells are taken from a patient’s body and returned to the patient later for treatment. Using autologous stem cells “circumvents the requirement for immunosuppressive treatments, which are necessary when cells from other donors are used,” the researchers said.

During the clinical trial, researchers will track six participants for 12 months and beyond to determine the safety of the stem-cell procedure and monitor for any improvements in Parkinson’s disease symptoms. Three participants have already been treated at Brigham and Women’s Hospital.

After treating the initial six patients in the first phase, investigators hope to expand and recruit more patients for the Phase 2A study.

Dr. Ole Isacson, a professor of neurology (neuroscience) at Harvard Medical School and Mass General Brigham, has spent 30 years working on Parkinson’s cell therapy and laying the groundwork for clinical trials.

“Seeing this transformational new patient cell-based replacement of their own dopamine neurons come to fruition—from the very basic science breakthroughs in our lab to be completely translated into a clinical application for patients suffering from Parkinson’s disease—is very gratifying,” Isacson said in a statement about the clinical trial. “We believe this approach may open up a new treatment paradigm and lead to the development of many additional cell therapies to restore damaged brain systems and replace degenerated brain cells in other diseases.”

Source Links:

https://www.apdaparkinson.org/article/understanding-stem-cell-therapy-in-parkinsons-disease-treatment/
https://www.the-independent.com/news/health/stem-cell-therapy-parkinsons-disease-clinical-trial-b2734261.html
https://www.npr.org/sections/shots-health-news/2025/04/17/g-s1-60796/parkinsons-stem-cell-transplant-treatment
https://www.nature.com/articles/d41586-025-00688-x
https://www.massgeneralbrigham.org/en/about/newsroom/press-releases/clinical-trial-novel-stem-cell-treatment-for-parkinsons