Implanting retinal cells into the brains of people with advanced Parkinson鈥檚 disease can improve motor function by almost a half, according to a follow-up study of six patients.
Parkinson鈥檚 is caused by the progressive loss of dopamine-producing cells in a region of the brain called the striatum. Retinal pigment epithelial cells, which are found in the inner layer of the neural retina, produce dopamine.
A team led by Ray Watts at Emory University School of Medicine used a product called Spheramine, which consists of retinal cells attached to gelatin micro-beads. These beads improve the survival of the cells in the brain. The cells were implanted into the striatum in the side of the patient鈥檚 brain most affected by cell loss.
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鈥淭his is the first human intracerebral retinal cell implantation study in the world and we are encouraged by the results so far,鈥� says Watts. 鈥淲e鈥檝e been following these six participants for over a year, and we鈥檝e found they鈥檝e improved, on average, nearly 50 per cent in motor function.鈥�
But not all Parkinson鈥檚 experts are convinced that retinal cell treatment is the way forward. There are other experimental cell implantation treatments for Parkinson鈥檚 and some have produced similar or even better results.
Reimplanted stem cells
Earlier in April, Michel Levesque at the Cedars-Sinai Medical Center in Los Angeles reported a total reversal of symptoms in one patient. The patient is still without symptoms three years after stem cells were removed from his brain, coaxed into becoming dopamine-producing cells, and then reimplanted.
鈥淚 think transplantation of the patient鈥檚 own neural stem cells and differentiated dopaminergic neurons is more biologically and physiologically compatible 鈥� more efficacious and more elegant,鈥� Levesque says.
The retinal cells used in Watts鈥� study were taken from deceased donors and grown in the lab. A total of about 325,000 cells, attached to the microcarriers, were injected into five different regions of the striatum in each patient.
鈥淲e will continue to follow these six participants for months to come. We hope to begin a phase II controlled trial soon, implanting Spheramine on both sides of the brain, instead of just one side,鈥� Watts says.
The team are not using immunosuppressants, because the immune system is not thought to be as active in the brain as in the rest of the body. 鈥淭here is an assumption that the brain is a relatively immune-privileged organ,鈥� Levesque says. 鈥淏ut it has also been shown that the brain does react to foreign bodies by an inflammatory response that may lead to infectious complications, such as brain abscesses.鈥�
Watts presented his research at the annual conference of the American Academy of Neurology in Denver, US.