Scientists Are Implanting Lab-Grown Brain Cells to Restore Dopamine in Parkinson's Patients

Researchers are testing a bold new approach: implanting specially engineered stem cells directly into the brain to restore dopamine production in people with Parkinson's disease. In an early-phase clinical trial at Keck Medicine of USC, doctors are surgically placing lab-grown cells into the brain's movement center, hoping to replace the neurons that Parkinson's gradually destroys. If successful, this could represent the first treatment to actually slow or halt the disease's progression, rather than just managing its symptoms.

Why Does Parkinson's Destroy Movement Control?

Parkinson's disease affects more than one million people in the United States, with approximately 90,000 new cases diagnosed each year. The condition is fundamentally a problem of dopamine loss. Dopamine is a chemical messenger in the brain that controls movement, memory, mood, and other essential functions. As Parkinson's progresses, the brain cells that produce dopamine gradually die off, leaving the brain unable to regulate movement properly. This breakdown causes the hallmark symptoms: tremors, muscle stiffness, and slowed motion.

Current medications and therapies can ease these symptoms, but no treatment has been proven to stop or slow the disease itself. That's what makes this new stem cell approach potentially transformative. "If the brain can once again produce normal levels of dopamine, Parkinson's disease may be slowed down and motor function restored," said Brian Lee, MD, PhD, a neurosurgeon with Keck Medicine and principal investigator of the study.

How Do Lab-Grown Stem Cells Replace Damaged Brain Cells?

The treatment uses a newer type of stem cell called induced pluripotent stem cells, or iPSCs. Unlike embryonic stem cells, which come from developing embryos, iPSCs are created by taking adult cells—such as those from skin or blood—and reprogramming them back into a versatile state. Once reprogrammed, these cells can develop into many different kinds of cells in the body, including dopamine-producing neurons.

"We believe that these iPSCs can reliably mature into dopamine-producing brain cells, and offer the best chance of jump-starting the brain's dopamine production," explained Xenos Mason, MD, a neurologist who specializes in Parkinson's disease and other movement disorders with Keck Medicine and co-principal investigator of the study.

What Does the Surgical Procedure Involve?

The implantation process is precise and carefully guided. A neurosurgeon creates a small opening in the skull to access the brain. Using magnetic resonance imaging (MRI) for real-time guidance, the surgeon carefully places the stem cells into the basal ganglia, the brain region responsible for coordinating movement. After the operation, participants undergo intensive monitoring for 12 to 15 months to track changes in symptoms and watch for potential side effects. Researchers plan to continue following patients for up to five years to assess long-term safety and effectiveness.

The clinical trial, called REPLACE, includes the following key details:

• Trial Size: The multisite study involves 12 people with moderate to moderate-severe Parkinson's disease across three sites in the United States.
• Therapy Name: The stem cell treatment is called RNDP-001 and is produced by Kenai Therapeutics, a biotechnology company focused on developing treatments for neurological disorders.
• Regulatory Status: The U.S. Food and Drug Administration has granted the trial fast-track designation, which is intended to speed up the development and review process.
• Monitoring Period: Participants are closely observed for 12 to 15 months initially, with continued follow-up for up to five years.

Researchers are watching carefully for potential complications, including dyskinesia (excess involuntary movements) or infection, though the goal is to demonstrate that the implanted cells can safely integrate into the brain and restore dopamine production.

This trial represents a significant shift in how doctors think about treating Parkinson's disease. Rather than simply replacing dopamine with medications, researchers are attempting to repair the brain's own dopamine-producing system at its source. "Our ultimate goal is to pioneer a technique that can repair patients' motor function and offer them a better quality of life," said Dr. Lee. If the early results are promising, this approach could eventually offer hope to millions of people living with Parkinson's worldwide.