Stem cells can do extraordinary things that other cells in the body cannot do. Put very simply, stem cells can renew themselves, and they have the potential to specialise and become other cells, like cells in muscle, blood or the brain.
What can stem cells potentially do?
In medicine, this means stem cells might be able to repair or replace damaged tissue in the body. Stem cells might be able to repair the MS damage in the central nervous system, and lead to re-growth of myelin and protection of nerve fibres, the most realistic aim for stem cell science in MS is to replace myelin around nerves, and in this way prevent nerve fibres from being lost. Stem cells might also be able to replace the immune system (thought to misfire in MS) and that way prevent the damage in MS.
Differentiation is the process by which a stem cell changes to become a specialised cell. (Stem cells are described as being unspecialised.) During the differentiation process, certain genes will become activated (and others de-activated) and the cell will develop a specific structure to carry out a certain function. Scientists are trying to work out how they might be able to influence or direct the differentiation process.
Different types of stem cells
· Embryonic stem cells are from part of the early (4- to 5-day) embryo or the 5- to 10-week fetus. They are pluripotent, which means they can give rise to all types of cells of the body.
· Adult stem cells are can be found in some parts of the body like bone marrow, brain, and retina of the eye, for example. (Umbilical cord blood is a source of blood-forming stem cells, similar to the cells obtained from bone marrow.) Adult stem cells are multipotent, capable of turning into a limited number of cell types.
· Progenitor or precursor cells are partially specialised. They divide and can give rise to differentiated or specialised cells. For example, scientists have identified neural precursor cells in the brain that can turn into oligodendrocytes, which are the cells that make myelin. Scientists hope that neural precursor cells can be used to repair damage in MS, either by transplanting cells, or by stimulating the existing cells.