Spinal injuries and stem cells

Spinal typically crush rather than cut the tissue leaving the axons intact. In this case, a primary problem is self-destruction (apoptosis) of the nearby oligodendrocytes. When these cells die and their associated axons lose their myelin coat, the axons cannot transmit information effectively. Severed axons within the CNS may grow small new extensions, but no significant regeneration of the axon occurs across the damaged site, and there are no well-documented reports of significant return of function. Functional regeneration is prevented either by some basic difference of CNS neurons or some property of their environment, such as inhibitory factors associated with nearby glia.

Researchers are trying a variety of ways to provide en environment that will support axonal regeneration in the CNS. They are creating tubes to support regrowth of the severed axons, redirecting the axons to regions of the spinal cord that lack growth-inhibiting factors, preventing apoptosis of the oligodendrocytes so myelin can be maintained, and supplying neurotrophic factors that support recovery of the damaged tissue.

Medical researchers are also attempting to restore function to damaged or diseased brains by implanting progenitor stem cells that will develop into new neurons and replace missing neurotransmitters or neurotrophic factors. Alternatively, pieces of fetal brain or tissues from the patient that produce the needed neurotransmitters or growth factors have been implanted. For example, in patients with Parkinson disease, a degenerative nervous system disease resulting in progressive loss of movement, the implantation of tissue from posterior portions of a fetal brain into affected area has been somewhat successful in restoring motor function. Ethical concerns have rendered the future of this technique uncertain, however.

(Widmaier EP, Raff H, Strang KT. Vander's Human Physiology: the mechanisms of body function. 12 ed.New York: McGraw-Hill International Edition; 2011)