Researchers Reveal Dopaminergic Neurons Derived from PSCs Could Treat Parkinson’s
A research team consisting of members from three major United States universities (Colorado, Rush and Yale) and scientists from the St. Kitts Biomedical Research Foundation, managed to transplant embryonic stem cells from humans to primates suffering from a laboratory modeled Parkinson’s disease. 6 weeks after the transplant, researchers report that the cells are still viable and are very well integrated into the host primates. The study was recently published in the online journal Cell Transplantation.
Parkinson’s disease is a neurodegenerative condition that affects the central nervous system. Approximately one and a half million U.S. citizens and more than ten million people worldwide. Symptoms include postural instability, bradykinesia, rigidity and tremor. These motor symptoms are caused by the death of the dopamine-generating cells found in the substantia nigra. The cause of the disease is not yet fully understood by scientists, but there are several therapies currently targeting the symptoms.
According to Professor Eugene Redmond, from the School of Medicine at the Yale University, Parkinson’s disease was among the first neurological disorders to which neuron-replacement therapy was considered. Starting in the early 1970s, researchers made progress towards learning the requirements to differentiate stem cells into dopamine-generating nervous cells. Since then, researchers progressed towards discovering the correct gene expression, the right amount of growth factors and the propitious culture factors that would result in the creation of dopamine-generating neurons.
However, precedent studies show that if dopamine-generating neurons are transplanted into animal models, such as primates and rodents, the effects are only short-lasting. Furthermore, only a very small amount of studies reveal functional improvement. According to the authors of the current study, they tested the long-term effects, survival rates and functional benefit of the dopamine-generating neurons implanted into laboratory primates suffering from Parkinson’s disease. As also shown in previous studies, the gene expression responsible for the activity of the enzyme known as TH (tyrosine hydroxylase), is only transitory. Tyrosine hydroxylase is an enzyme that plays an important role in the synthesis of catecholamines. Researchers have been trying to discover the best cellular stage and the best culture environment in order to increase the survivability of the transplanted cells. One factor that was underlined was the need for a stronger immunosuppression.
Professor Redmond affirms that the results of this study reveal that these dopamine-generating neurons, derived from PSCs (pluripotent stem cells), maintain their responsive abilities once they were transplanted into the brains of primates. However, the absence of a continuous TH expression shows that further research is needed in order to create and maintain the correct form of dopamine-generating neurons.
Although the study shows that the transplanted neurons are capable of surviving in the brain of primates, the research team concluded that further long-term studies need to be don in order to better understand the factors that contribute to a functional long-term replacement of dopamine-generating neurons.