Stem cells differ from other kinds of cells in the body. All stem cells - regardless of their source - have three unique properties:

1. Capable of dividing and renewing themselves for long periods of time
2. Unspecialized
3. 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.  

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.