07/10/2026  |  Paloma Oliveto  |  Correio Brasiliense

https://www.correiobraziliense.com.br/ciencia-e-saude/2026/07/7458373-estudo-testa-transplante-de-celulas-como-tratamento-para-parkinson.html 

In a preliminary study involving eight patients, scientists demonstrated the safety of the procedure, which uses embryonic tissue reprogrammed to become neurons. There is still a long way to go before clinical application, but the authors are optimistic

For decades, the treatment of Parkinson’s disease has focused on alleviating the symptoms caused by the progressive loss of neurons that produce dopamine, which is currently achieved through the use of medications. Now, a human study points to a new therapeutic approach: replacing destroyed brain cells with new structures of embryonic origin, genetically programmed to naturally produce the neurotransmitter.

In Parkinson’s disease, the brain loses nerve cells that produce dopamine, leading to symptoms such as slowness of movement, rigidity, gait disturbances, and tremors. Although the most modern medications have revolutionized the treatment of the disease, improving patients’ quality of life, over time these substances often become less effective and can cause neurological, gastrointestinal, and psychiatric side effects, among others.

To address these limitations, researchers from England, Sweden, and the United States tested the safety of transplanting dopamine-producing neurons derived from embryonic stem cells into the brain. As this is still a preliminary study, the research—published in the journal *Nature Medicine* and presented yesterday at the annual meeting of the International Society for Stem Cell Research in Montreal, Canada—was conducted with only eight patients, who were followed for one year. According to the scientists, the procedure proved feasible, paving the way for studies involving a larger number of participants. 

Marco
“The possibility of replacing the dopaminergic neurons lost in Parkinson’s disease has been a long-standing goal in the field,” said Malin Parmar, a professor of cellular neuroscience at Lund University in Sweden and the study’s lead author. “The findings represent an important milestone for regenerative medicine approaches to Parkinson’s disease and support the continued clinical development of stem cell-based therapies.” 

In the study, eight patients with the neurodegenerative disease received the cell product transplanted in two different doses, followed by 12 months of immunosuppression to prevent graft rejection. Seven participants completed the follow-up, and one died from a lung infection not directly related to the procedure. According to the authors, the surgical procedure was well tolerated, with no significant side effects. 

Imaging tests using a dopamine production marker showed increased activity precisely in the regions where the cells had been implanted, especially among patients who received the higher dose of the graft. For the researchers, this indicates that some of the transplanted cells survived and began to function.  

Symptoms
With regard to symptoms, the results were more modest. Some patients showed improvement in motor function, others remained stable, and most were able to reduce their daily dose of anti-Parkinson’s medications. Six of the seven volunteers followed for one year reduced the amount of medication they were taking.

“We hope this is the beginning of a new and exciting program that could ultimately benefit the entire Parkinson’s patient community,” said Roger Barker, professor of clinical neuroscience at the University of Cambridge and clinical lead and principal investigator at the UK center, in a statement.  

Today, it is estimated that more than 8.5 million people worldwide live with Parkinson’s, a number that could exceed 12 million by 2040. According to the World Health Organization (WHO), it is the neurological disease with the fastest-growing prevalence and disability rates in recent decades. In Brazil, there are about half a million diagnosed patients, with approximately 36,000 new cases each year. 

Embryos
Although the study’s tests were conducted using human embryonic stem cells, the authors believe that in the future it will be possible to use cells derived from the patient’s own skin or blood and reprogrammed to specialize in dopamine production. In addition to the work described yesterday, there are teams in the United States, Japan, and South Korea working with different cell types to differentiate them into dopaminergic neurons. 

 “The biggest challenge for autologous cell therapy (which uses the patient’s own cells) has been developing reliable methods to qualify each patient’s cells for treatment,” explains Jeanne Loring, a researcher at Scripps Research in the United States. According to the researcher, genomic analysis approaches that identify potential future mutations have been used to make the procedure increasingly personalized.

The new study, however, is preliminary, and experts caution that there is still a long way to go to confirm the findings. “Although the research offers hope, we are still far from saying that this is a therapy that will be used in clinical practice. There are still several steps to go, as these initial studies are in the phase of evaluating the treatment’s safety—that is, to assess whether these stem cells will transform into malignant or tumor cells. This is one of the main concerns, in addition to long-term complications, which could even worsen the symptoms of Parkinson’s disease,” notes neurologist Luciana Mendonça Barbosa, a professor at the Catholic University of Brasília (UCB).

The professor points out that there are two other preliminary studies on dopaminergic cell transplantation that have demonstrated safety. “This third study shows that the treatment is, in fact, safe over the course of a year. Scientists will follow the patients for another three years, so we’ll have more data on it,” she says. 

Even with the limitations of the current phase, Jeanne Loring says she is optimistic. “We’ve known for decades that transplanting young dopaminergic neurons can reverse the symptoms of Parkinson’s disease when the appropriate cells are used. If these findings are confirmed over time, we expect to see significant improvements in quality of life, which will continue to increase as the transplanted cells mature,” she explains. 

Expert Opinion

The study represents a major breakthrough in the possibility of safely implanting a patient’s own stem cells into the brain. The fact that scientists have demonstrated that these stem cells survived is very interesting. Not only did they survive, but they actually proved to be functional: they were able to produce dopamine without complications such as hemorrhages or tumor formation. However, in practice, this is not yet of immediate clinical use—so far, the goal has been to demonstrate safety. It may be that, as this study continues, ways to achieve greater clinical efficacy will be discovered. Science faces several challenges in advancing this type of research. The first was to prove that it is possible to differentiate a patient’s stem cell so that it produces dopamine and to safely implant it into the brain. The next challenge is to confirm this safety in a larger number of patients and to understand whether there will be a clinical benefit that justifies the complexity of the procedure. 

Bruno Brujaili, neurosurgeon at the Sírio-Libanês Hospital in São Paulo, specialist in Parkinson’s disease

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Does this study represent a paradigm shift in the treatment of Parkinson’s disease?

Yes, it’s a possibility. Currently, the treatment for motor and non-motor symptoms of Parkinson’s disease involves replacement therapy—either with dopamine or other neurotransmitters that may be altered in the patient’s brain. In the case of motor symptoms, they are treated with dopamine replacement, which acts precisely on the nigrostriatal pathway (a bundle of dopaminergic neurons connecting the substantia nigra to the striatum) that is deficient and causes symptoms of rigidity, tremor, and slowness of movement. This study, which is still preliminary and currently in Phase 1 and 2 trials in humans, still needs to be confirmed by more comprehensive research. But what has been described is indeed a new treatment strategy. If this is confirmed in larger studies, patients will need lower doses of dopamine to achieve the same improvement in symptoms compared to current medications. 

What are the main scientific challenges before a cell therapy like this can be offered in clinical practice?

There is still a long way to go before it reaches clinical practice, but the first step has been taken; the results are indeed encouraging and now need to be confirmed in larger populations, as well as in placebo-controlled trials. When we compare the treatment described in the study with a procedure that does not introduce dopamine-producing cells into the brain—or that implants a different type of cell that does not produce the substance—we will be able to confirm whether the intervention being performed is indeed what causes the symptomatic improvement in these patients. This will likely take several more years—at least five—before we can arrive at a definitive answer.

Carlos Uribe, neurologist at Hospital Brasília, part of the Rede Américas network