What is Stem Cell Therapy?
Stem cells differ from other kinds of cells in the body. All stem cells - regardless of their source - have three unique properties:
- Capable of dividing and renewing themselves for long periods of time
- Unspecialized
- Can give rise to specialized cells
These unique properties could be used for cell-based therapies in which stem cells that are genetically altered to produce the missing enzyme are delivered to the brain or central nervous system.
What is the Current Status of Stem Cell Therapy?
Many potential treatments are currently being tested in animal models and some have already been brought to clinical trials for spinal cord injuries and diseases related to the eye (from http://stemcells.nih.gov/info/health.asp). Breakthrough work has been done in the Sandhoff mouse model and was partially funded by the NTSAD Research Initiative.
To learn more, read Stem cells act through multiple mechanisms to benefit mice with neurodegenerative metabolic disease, published by Nature Medicine, 2007.
What are the Challenges to Stem Cell Therapy?
Stem cell therapy has a lot of promise to cure but faces formidable challenges to develop safe and effective therapies. Some of the challenges include:
- Risk of an immune response leading to rejection of these cells
- Risk of cells differentiating in an unexpected way
- Transmission of donor-related diseases that reside in those stem cells
- Ability to scale-up the amount of cells needed for humans
- Acceptance of this approach owing to the controversy over embryonic stem cells
The embryonic stem cell controversy is becoming less of an issue as scientists have recently discovered how to manipulate adult cells into a stem cell state but more work is necessary to understand their therapeutic properties and potential.
Also see 
Bone Marrow Transplant
Learn more:
http://stemcells.nih.gov/info/basics/basics1.asp
http://learn.genetics.utah.edu/content/tech/stemcells/