Stem cells show promise for Parkinson's disease

Motor neurons derived from human embryonic stem cells (hESCs) have restored muscle function in a rat model of Parkinson's disease, taking a first and important step towards the use of cell replacement therapy in humans with this incurable condition.

Parkinson's disease is a degenerative movement disorder that affects millions of people around the world. It is caused, in part, by the death of neurons in the brain that release the neurotransmitter dopamine.

The loss of dopaminergic nerve cells leads to progressive problems with control over movement along with tremors, slowness, speech problems and other life-changing symptoms. Current treatment options can cause severe side effects such as involuntary movements and lose effectiveness over time.

European researchers transplanted hESC-derived dopaminergic neurons into the brains of rats with Parkinson’s disease and found this led to an increase in dopamine levels and restoration of muscle function. The neurons, located in the mid-brain, survived and retained their function up to 6 months post-transplantation.

“Our study represents an important milestone in the preclinical assessment of hESC-derived dopamine neurons and provides essential support for their usefulness in treating Parkinson’s disease,” said Malin Parmar of Lund University in Sweden.

The transplanted cells restored dopamine levels back to normal within five months. The researchers also observed that the neurons projected sufficiently long distances for use in humans, regenerated midbrain-to-forebrain connections and innervated the correct target structures.

In a review of the study, Roger Barker of Addenbrooke’s Hospital and the University of Cambridge said the researchers should be rigorous and not rush the work into clinical trials for Parkinson’s disease.

“This involves understanding the history of the whole field of cell-based therapies for Parkinson’s disease and some of the mistakes that have happened,” he said. “It also requires a knowledge of what the final product should look like and the need to get there in a collaborative way without being tempted to take short cuts, because a premature clinical trial could impact negatively on the whole field of regenerative medicine.”

The study has been published in Cell Stem Cell