There Could Be Hope for Parkinson's Therapies in Neural Stem Cells
Neurons made from stem cells integrated just fine in mouse brains, offering hope for replacement therapies.
An artist's impression of neurons. Image: Shutterstock/Andrej Vodolazhskyi
It seems an incredibly simplistic solution to dealing with the sick or dead neurons caused by degenerative diseases like Parkinson's and Alzheimer's: replace them with healthy ones. But one day, in theory, it just might be as easy as that.
In a study on mice, researchers at the University of Luxembourg have made neurons out of skin cells and successfully implanted them into the rodents' brains. They published their results in a paper in Stem Cell Reports, which builds on earlier work on converting stem cells. What the new study showed was that after six months the implanted neurons became fully integrated into the brain, forming new synapses and exhibiting normal activity, with no adverse effects.
"This long-term aspect is the really interesting part here—the fact that they first survive for half a year, which is pretty long for a mouse; the fact that they do not form a tumour; and that they perfectly integrate in the existing network," cellular biologist Jens Schwamborn, who led the team, told me.
Stem cells are kind of like a blank slate cell that can be reprogrammed into a specialised cell; we've seen them make skin, blood cells, lung cells, and insulin-producing cells aimed at treating diabetes. Clearly, they can also be reprogrammed into neurons.
In a petri dish, the researchers programmed the neurons from the mice's own skin cells, the idea being that there won't be any immune reaction when you use the same organism's cells. They then transplanted them into the cortex and hippocampus of the brain. "In principle, it's just an injection of cells at a particular position of the brain," explained Schwamborn.
The fact that the new neurons started functioning as normal is a step toward replacement therapy—basically, replacing neurons that have degenerated with shiny new ones. But before anyone gets too excited about "cures" for conditions like Parkinson's, Alzheimer's, and Huntington's, debilitating diseases which have so far eluded any real remedy, bear in mind that translating the work to humans will inevitably take a long time. It's still early stages.
Schwamborn said there's an ongoing study to do the same thing with human cells, which he's confident will work, then to be more specific in terms of the cell type they want to use. "Here we had a mixture of all possible cell types; by using pre-differentiation conditions, we could push them, for example, to become dopaminergic neurons used for Parkinson's disease," he said. Dopaminergic neurons are the ones that generate dopamine, and that are lost in Parkinson's disease.
More long term aims include testing the technique in primates, which is still a while off. And then, if all goes well: personalised cell-replacement therapies.