neurodegenerative disease

Stem cell treatment improves motor function in monkeys modeling Parkinson’s Disease

/ Yimy Villa / 2 Comments

Neurodegenerative diseases impact millions of people worldwide with the risk of being affected by one of these diseases increasing as you get older. For many of these diseases, there are very few treatments available to patients. As life expectancy increases and the population continues to age, it is crucial to try and find treatments that can potentially slow the progression of these diseases or cure them entirely. This is one of the reasons why CIRM has committed directing around $1.5 billion in funding over the next few years to research related to neurological disorders.

One of the most common neurodegenerative diseases is Parkinson’s Disease (PD), a movement disorder that affects one million people in the U.S alone and leads to shaking, stiffness, insomnia, fatigue, and problems with walking, balance, and coordination.  It is caused by the breakdown and death of dopaminergic neurons, special nerve cells in the brain responsible for the production of dopamine, a chemical messenger that is crucial for normal brain activity.

A recent study published in Nature Medicine has shown improved motor function and growth of neurons over a two year period in monkeys modeling PD. The study was conducted by Su-Chun Zhang, M.D., Ph.D. and his team at the University of Wisconsin using induced pluripotent stem cells (iPSCs), a kind of stem cell that can become virtually any type of cell that can be made from skin cells. The hope is that these results can pave the way for starting human clinical trials.

In order to replicate PD in humans, the team injected 10 adult monkeys with a neurotoxin that produces PD like symptoms. As a result of this, all 10 monkeys developed slow movements, imbalances, tremors, and impaired coordination in the hand on the opposite side of the injection. Additionally, scans revealed that on the injected side, monkeys lost most brain activity involving dopamine in two key brain areas. The team then waited three years after injecting the neurotoxin before administering the therapy, during which time the monkeys’ symptoms persisted.

To generate iPSC lines, the team obtained skin cells from five of the monkeys. The iPSCs were then turned into dopamine neural progenitor cells, which have the ability to create dopamine. These newly created cells were then administered into the brains of the five monkeys, with each monkey receiving a treatment derived from their own skin cells. A sixth iPSC line from a donor monkey was used for the remaining five monkeys to see how the treatment would work if it was not derived from their own skin cells.

The results showed that the monkeys that received the treatment derived from their own skin cells recovered. These animals moved more, moved faster, and were nimbler than before the treatment. They gained the ability to grasp treats, use all four limbs for walking, and climb their cages with ease and increased agility. However, the monkeys that received iPSCs derived from a donor did not recover. Their symptoms remained unchanged or worsened compared to before the treatment.

In a news article, Zhang emphasizes how he and his team are proceeding with a treatment derived from one’s own cells (autologous) vs. one from a donor (allogeneic).

“I initially wanted to do allogeneic transplants in patients because the autologous approach is too expensive. However, after seeing [our] data, I changed my mind. I want to go with the autologous first… because I feel the chance of success is really, really high.”

CIRM is currently funding a human clinical trial ($5.5 million) that is using a gene therapy approach for PD.

CIRM-funded Stanford study finds potential diagnostic tool, treatment for Parkinson’s

/ Yimy Villa / Leave a comment
Dr. Xinnan Wang, a neurosurgeon and author of a study that has identified a molecular pathway apparently responsible for the death of dopaminergic neurons that causes the symptoms of Parkinson’s.

Of the various neurodegenerative diseases, Parkinson’s is the second most common and affects 35 million people world wide. It is caused by the gradual breakdown of dopaminergic neurons in the brain, which are a type of cell that produce a chemical in your brain known as dopamine.  This decrease in dopamine can cause complications such as uncontrollable shaking of the hands, slowed movement, rigid muscles, loss of automatic movements, speech changes, bladder problems, constipation, and sleep disorders.

Although 5-10% of cases are the result of genetically inherited mutations, the vast majority of cases are sporadic, often involving complex interactions of multiple unknown genes and environmental factors. Unfortunately, it is this unknown element that make the disease very difficult to detect early on in the majority of patients.

However, in a CIRM funded study, Dr. Xinnan Wang and her team at Stanford University were able to pinpoint a molecular defect that seems almost universal in patients with Parkinson’s and those at high risk of acquiring it. This could prove to be a way to detect Parkinson’s in its early stages and before symptoms start to manifest. Furthermore, it could also be used to evaluate a potential treatment’s effectiveness at preventing or stalling the progression of Parkinson’s.

In a Stanford press release, Dr. Wang explains the implications of these findings:

“We’ve identified a molecular marker that could allow doctors to diagnose Parkinson’s accurately, early and in a clinically practical way. This marker could be used to assess drug candidates’ capacity to counter the defect and stall the disease’s progression.” 

What is more astounding is that Dr. Wang and her team were also able to identify a compound that is shown to reverse the defect in cells taken from Parkinson’s patients. In an animal model, the compound was able to prevent the death of neurons, which is the underlying problems in the disease.

In their study, Dr. Wang and her team focused on the mitochondria, which churns out energy and is the powerhouse of the cell. Dopaminergic neurons in the brain are some of the body’s hardest working cells, and it is theorized that they start to die off when the mitochondria burns out after constant, high energy production.

Mitochondria spend much of their time attached to a grid of protein “roads” that crisscross cells. Our cells have a technique for clearing “burnt out” mitochondria, but the process involves removing an adaptor molecule called Miro that attaches mitochondria, damaged or healthy, to the grid. 

Dr. Wang’s team previously identified a mitochondrial-clearance defect in Parkinson’s patients’ cells that involved the inability to remove Miro from damaged mitochondria.

In the current study, they obtained skin samples from 83 Parkinson’s patients, Five patients with asymptomatic close relatives considered to be at heightened risk, 22 patients diagnosed with other movement disorders, and 52 healthy control subjects. They extracted fibroblasts, which are cells common in skin tissue, from the samples and subjected them to a stressful process that messes up mitochondria. 

The researchers found the Miro-removal defect in 78 of the 83 Parkinson’s fibroblasts (94%) and in all five of the “high-risk” samples, but not in fibroblasts from the control group or patients with other movement-disorders.

Next, the team was able to screen over 6.8 million molecules and found 11 that would bind to Miro, initiating separation from the mitochondria, are non-toxic, orally available, and able to cross the blood-brain barrier. These 11 compounds were tested in fruit flies and and ultimately one of them, which seems to target Miro exclusively, was tested on fibroblasts from a patient with sporadic Parkinson’s disease. The compound was found to substantially improved Miro clearance in these cells after their exposure to mitochondria-damaging stress.

Dr. Wang is optimistic that clinical trials of the compound or something similar are no more than a few years off.

In the same Stanford press release, Dr. Wang stated that,

“Our hope is that if this compound or a similar one proves nontoxic and efficacious and we can give it, like a statin drug, to people who’ve tested positive for the Miro-removal defect but don’t yet have Parkinson’s symptoms, they’ll never get it.”

The full results of this study were published in the journal Cell Metabolism.