I can answer for PD but other neurodegenerative diseases are similar.
Unfortunately, for Parkinson's disease, stem cell treatments have not been very successful so far. Part of the reason is that the abnormal protein (alpha-synuclein) which causes the degeneration of neurons continues to spread, even in the grafted stem cells. In other words, we are not addressing the underlying reason for the degeneration.
Also, stem cells are meant to replace neurons in areas of the brain responsible for movement. We already have fairly good treatments for those symptoms (including levodopa). Parkinson's gets more challenging to treat when it starts to affect other parts of the brain and causes "non-motor symptoms". Stem cells would not help with those symptoms.
There are other adverse effects of stem cells like dyskinesia and the theoretical risk of cancer, etc.
It's still an area of active research so there is still hope. It may be an adjunct treatment to disease-modifying treatments in the future.
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TL;DR: stem cells replace neurons but don't fix the underlying problem that causes the death of neurons
Tounsk t1_j2d0lmu wrote
Reply to ELI5 Why aren't we curing more degenerative diseases with stem cell research? by KaishiXYZ
I can answer for PD but other neurodegenerative diseases are similar.
Unfortunately, for Parkinson's disease, stem cell treatments have not been very successful so far. Part of the reason is that the abnormal protein (alpha-synuclein) which causes the degeneration of neurons continues to spread, even in the grafted stem cells. In other words, we are not addressing the underlying reason for the degeneration.
Also, stem cells are meant to replace neurons in areas of the brain responsible for movement. We already have fairly good treatments for those symptoms (including levodopa). Parkinson's gets more challenging to treat when it starts to affect other parts of the brain and causes "non-motor symptoms". Stem cells would not help with those symptoms.
There are other adverse effects of stem cells like dyskinesia and the theoretical risk of cancer, etc.
It's still an area of active research so there is still hope. It may be an adjunct treatment to disease-modifying treatments in the future.
​
TL;DR: stem cells replace neurons but don't fix the underlying problem that causes the death of neurons
https://www.ncbi.nlm.nih.gov/books/NBK536728/#:~:text=As%20has%20been%20discussed%2C%20the,particularly%20disabling%20in%20some%20patients.
https://pubmed.ncbi.nlm.nih.gov/18391962/