Parkinson’s disease (PD) is a common, progressive neurological disorder that primarily affects movement. It occurs when brain cells that produce a chemical called dopamine begin to die, particularly in a part of the brain called the substantia nigra. Dopamine plays a crucial role in controlling movement, so when these cells are lost, people experience symptoms such as tremors, stiffness, slow movements, and trouble with balance.
While there are medications that help control symptoms, these treatments don’t stop the disease from progressing. Over time, their effectiveness may wear off, and they can cause unpleasant side effects. This has led scientists to explore new options – one of the most promising being stem cell therapy. This blog explores how stem cells might help treat Parkinson’s, what types of stem cells are being studied, and what we can expect in the near future.
The Challenge of Treating Parkinson’s Disease
Current treatments for PD mainly focus on managing symptoms, not curing the disease. The most commonly used drug is levodopa, which the body converts into dopamine. While levodopa helps relieve movement symptoms, it doesn’t only act where it’s needed. It floods the brain more broadly, which can lead to unwanted effects like hallucinations, cognitive problems, and involuntary movements (called dyskinesias).
Also, as the disease progresses, people often experience “motor fluctuations,” where the medication wears off before the next dose is due, making symptoms come and go unpredictably. More advanced therapies, such as deep brain stimulation or special levodopa gels, can help some people, but they’re not suitable or affordable for everyone.
In short, while medications help many people live better with Parkinson’s, they don’t solve the underlying problem: the loss of dopamine-producing cells. This is where regenerative medicine – and especially stem cells – comes in.
The Promise of Stem Cells in Parkinson’s Treatment
Stem cells are special cells that can turn into many different types of cells in the body. Importantly, they can also replicate themselves, giving researchers a potentially endless supply of cells to work with. For Parkinson’s, the idea is to turn stem cells into dopamine-producing neurons (the kind that die off in PD) and then implant them into the brain. Ideally, these new cells would settle into the right areas and start working like the original ones did – releasing dopamine in a natural, balanced way.
This targeted, biological approach might avoid many of the side effects of current drug treatments. It also holds the potential for long-lasting effects, possibly even slowing or stopping disease progression. Over the years, researchers have experimented with different kinds of cells to achieve this goal, but stem cells are currently the most promising option.
Types of Stem Cells Being Studied
Embryonic Stem Cells (ESCs)
These stem cells come from early-stage embryos (usually donated from in vitro fertilization). They can become any cell type in the body. Scientists have worked for years to coax these cells into becoming the specific type of dopamine-producing neurons lost in Parkinson’s. Early versions of this approach had inconsistent results – sometimes the cells didn’t fully become the right type of neuron, or the process produced too few usable cells.
However, advances in understanding how brain cells develop during embryonic stages have helped improve these techniques. Scientists now have better protocols that consistently produce authentic dopaminergic neurons – the ones from the midbrain region involved in movement control.
Even though results are getting better, some challenges remain. ESC-based treatments require immunosuppression, because the implanted cells aren’t from the patient’s own body and could be rejected. But despite these hurdles, clinical trials using ESC-derived neurons are expected to begin soon, marking a significant step forward.
Induced Pluripotent Stem Cells (iPSCs)
Introduced in 2007, iPSCs offer an exciting alternative. These are adult cells (like skin or blood cells) that scientists reprogram to become stem cells. Like ESCs, iPSCs can turn into almost any cell type, including dopamine-producing neurons.
One major advantage of iPSCs is that they can be made from a person’s own cells. This opens the door for personalized treatment – using your own cells to create brain implants – reducing the risk of immune rejection and the need for long-term immunosuppressive drugs.
So far, iPSC-based therapies have shown promise in animal studies, including in primates. Grafted cells survived, didn’t form tumors, extended connections to the brain’s movement centers, and improved movement symptoms. As with ESCs, human trials using iPSC-derived neurons are expected to begin soon.
Mesenchymal Stem Cells (MSCs)
MSCs come from adult tissues such as bone marrow. They’re easier to obtain than ESCs or iPSCs and don’t raise the same ethical concerns. However, they don’t naturally become dopamine-producing neurons. While they can produce some dopamine-related proteins in the lab, they don’t fully develop into the authentic neuron types needed for Parkinson’s treatment.
Still, MSCs may have other benefits. They release factors that reduce inflammation and protect brain cells from damage. These properties could help slow down disease progression or support other treatments, but so far, they haven’t been shown to improve movement symptoms directly. More research is needed to determine their role in PD therapy.
Induced Neurons (iNs)
Another approach is to directly convert a person’s regular body cells (like skin cells) into neurons without going through a stem cell stage. This avoids the risk of the cells turning into tumors, which is a theoretical concern with stem cells. These so-called induced neurons could also be made from a patient’s own cells.
Unfortunately, this method is still in its early days. The process doesn’t produce many cells, and results have been inconsistent. Right now, it’s not seen as a practical option for widespread treatment, but researchers are exploring ways to improve the technique.
There’s also some interest in trying this direct conversion inside the brain – turning support cells (astrocytes) into neurons in the patient’s brain itself. While intriguing, this concept is still highly experimental.
Progress in Stem Cell Research for Parkinson’s
The journey toward stem cell therapy for Parkinson’s has taken decades, but recent discoveries have helped clear many of the obstacles that held progress back. For instance, researchers now understand better how to guide stem cells into becoming the exact type of neurons needed for treatment. They’ve also developed quality control markers to ensure the cells being implanted are the right kind and at the right stage of development.
Animal studies have shown that these therapies can be safe and effective, leading to improvements in motor function without serious side effects. We’re now at the point where human trials using both ESCs and iPSCs are about to begin or are already in progress. These trials will help answer important questions about safety, effectiveness, and long-term outcomes.
Stem Cell Therapy: A Promising Future for Parkinson’s Treatment
Stem cell therapy is not a guaranteed cure for Parkinson’s disease, but it stands out as one of the most promising advancements in the effort to combat this debilitating condition. If successful, these therapies could offer more natural dopamine delivery, helping to reduce the side effects commonly associated with current medications. They may also provide longer-lasting benefits, potentially minimizing the need for frequent doses. By using a patient’s own cells, the treatments could be tailored for personalized care, and perhaps most significantly, they may introduce a new way to slow the progression of the disease rather than simply masking its symptoms.
There’s still significant work ahead. Clinical trials take time, and important questions remain about cost, access, and how to manufacture these treatments on a large scale. Even so, science continues to move forward at a rapid pace, and growing optimism can be felt throughout the medical community.
Parkinson’s disease remains a major challenge for patients, their families, and healthcare providers. While traditional medications can offer some relief, they do not offer a cure. As stem cell research accelerates, we may be moving closer to a future in which therapies don’t just manage symptoms – but help restore lost function and improve quality of life.
Source: Stoker TB. Stem Cell Treatments for Parkinson’s Disease. In: Stoker TB, Greenland JC, editors. Parkinson’s Disease: Pathogenesis and Clinical Aspects [Internet]. Brisbane (AU): Codon Publications; 2018 Dec 21. Chapter 9. Available from: https://www.ncbi.nlm.nih.gov/books/NBK536728/ doi: 10.15586/codonpublications.par
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