A new method of synthesizing dopamine-producing neurons, the predominant type of brain cell destroyed in Parkinson’s, offers hope for creating cell-replacement therapies that reverse the damage.
The method provides an efficient way of making functional cells. When transplanted into mice and rats with brain damage and movement problems similar to Parkinson’s, the cells integrated into the brain and worked normally, reversing the animals’ motor issues.
The finding brings researchers a step closer to testing a stem-cell-derived therapy in patients with this disorder. “We finally have a cell that seems to survive and function and a cell source that we can easily scale up,” says Lorenz Studer, a researcher at the Sloan Kettering Institute and senior author on the new study. “That makes us optimistic that this could potentially be used in patients in the future.”
The research also highlights the challenges of generating cells for tissue-replacement therapy, showing that subtle differences in the way the cells are made can have a huge impact on how well they work once implanted.
Many of the symptoms of Parkinson’s disease—which include tremor, muscle rigidity, and loss of balance—are linked to loss of dopamine in the brain. While medications exist to replace some of the lost chemical, they do not alleviate all of the symptoms and can lose their effectiveness over time. Scientists hope that replacing lost cells with new ones will provide a more complete and long-term solution.
In the new study, researchers started with human embryonic stem cells, which by definition can differentiate into any cell type. To make a specific type of cell in high numbers, scientists expose the stem cells to a cocktail of chemicals that mimic what they would experience during normal development.
While stem-cell researchers had previously been able to create dopamine-producing neurons from human stem cells, these cells did little to alleviate movement problems in animals engineered to mimic the symptoms of Parkinson’s. In 2009, Studer and others developed a method of making the cells that more closely mimics the way they form during development. The resulting cells also carry more of the molecular markers that characterize dopamine-producing cells in the brain.