Monday, November 7, 2011

Stem cells can finally be used to treat brain disease

By transforming stem cells into neurons, the cells of the brain, scientists have shown that they are able to treat parkinson's disease in monkeys. By this, they finally delivered some of the promises that stem cells have when it comes to treating diseases. Monkeys that have human-like parkinson's disease were treated with neurons that were derived from stem cells, and guided into producing the brain messenger dopamine. The cells integrated into the brain, and were able to restore movement that was lost due to the disease, while no side-effects were noted. This is an important step for the development of a cure for parkinson's, which currently can only be treated by reducing the symptoms.

A dopamine neuron.
Monkeys were given six injections of a million cells each. When the scientists tracked the cells they injected, they were found to be integrating with the existing wiring of the brain, and functioning by producing dopamine, the neurotransmitter that patients with parkinson's lack. The injected cells were also found to be safe, as no tumour formation or aggressive overgrowth of the injected cells was reported in the animals. To further illustrate the potency of this treatment, the scientists found the same result in two other animal species: rats and mice. This indicates the treatment is ready for tests in human patients, which will probably conducted on a small scale at first. What makes it even more interesting, is the fact that the cells used in their experiments are already of human origin.

Previous attempts to restore neuronal tissue in parkinson's patients involved using foetal brain tissue, that was supposed to restore the dopamine-producing neurons. While there was some form of success, it is not a feasible therapy, as foetal tissue is controversial, and hard to obtain. Producing stem cells that can be guided into the right cell type for integration into the brain and playing a role in dopamine production is now much more likely to work, given the latest results. Another advantage of using cell-based therapy is the ability to take the patient's own cells, for example from the skin, transform these to stem cells, and consequently differentiate those into the cell types that the patients needs. By this, the required starting material is easy to obtain and will not be recognized by the immune system as foreign objects. Something similar has already been tried with liver cells, that were transformed to neurons. However, it was previously unable to create the right type of neuronal cell for use in parkinson's patients. While some neurons did produce dopamine, it was never found to be enough.

Dopamine signaling is required for proper motor functions, which explains the shaking behaviour of parkinson's patients that have lost their dopaminergic neurons. In addition, dopamine functions in the reward system of our brain.

Recently, scientists have shown great advancements in the production of relevant stem cells. For example, we are now able to make human embryonic stem cells in the lab, instead of deriving them from foetal tissue. Also, the production of stem cells can now be performed a 100 times faster with a novel technique. All in all this shows stem cell therapy is becoming more and more a reality.

Stem cells have been hallowed as a wonder drug for many incurable diseases. This is because we can direct them into becoming any type of cell we want, as long as we give them the right cue. By this, scientists thought, we can easily replace all damaged tissue the body can not repair. This is especially important for diseases of the nervous system, of which parkinson's is an example. The body is rarely able to restore lost neurons, while other cells, such as those from the liver, readily grow back after being damaged.

However, using stem cells in the clinic was not as easy as many scientists thought. At first, it was hard to obtain the cells, because research on stem cells was in the past often prohibited, mostly due to religious movements that severely damaged the progress of medical research. Secondly, it was found that stem cells can have unwanted side-effects, such as tumour development. Because of this, many promising stem cell-based therapies have not yet found their way into the clinic.

It is likely that the scientists will want to start clinical trials for this novel therapy as soon as possible. Earlier studies revealed the structure of a protein that is likely to be a key component in inducing parkinson's, and it has been tried to restore neurons by electrically stimulating the damaged parts of the brain, while a stem cell treatment was already found to be effective in damaged spinal cords.

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