Bone marrow stem cells

These cells have been studied for some time, and it is now known that adult stem cells from bone marrow have the potential to generate cell types not just of blood, but of other tissue in the body, like brain tissue. This is called plasticity, and it is a relatively new concept for adult stem cells. Bone marrow stem cells can differentiate to become cell types found in the brain like neurons, oligodendrocytes and astrocytes (the three main types of neural cells).

Researchers hope to discover whether these cells will repair myelin, and whether there are risks in using stem cells in this way. Scientists hope to find out the genetic signals that can coax adult stem cells from bone marrow to become oligodendrocytes that can make myelin. 

Schwann cells

These are not stem cells – they are specialised myelin-making cells found in the peripheral nervous system (external to the brain and spinal cord).

In some ways, they appear possible candidates for transplantation – Schwann cells are relatively accessible in the body, and they can be grown and purified ready for transplant. On the down side, however, Schwann cells generally do not find the environment of the brain and spinal cord to their liking, and they have a limited ability to engage in widespread myelin repair. One study several years ago in MS attempted to transplant Schwann cells into the central nervous system but the results are unpublished. 

Olfactory ensheathing cells

These are specialised cells found within the tissue that connects the scent-detecting nerve cells in the nose to the brain, and they are attracting a lot of attention among scientists.

These cells are on the border between the central nervous system and the peripheral nervous system, and they can operate in both environments. Rat and human olfactory ensheathing cells can make new myelin sheaths in the central nervous systems of rats. The location of these cells in the nose lining also makes them more accessible than brain cells, (although less accessible than Schwann cells). Scientists believe that olfactory ensheathing cells might be good candidates for transplantation to promote repair in MS and in spinal cord injury, for example, although much more work is needed to assess their potential.