Essay, Research Paper: Spinal Cord Regeneration

Spinal Cord Regeneration


Spinal cord injury can occur in many ways ranging from gunshot wounds, stab wounds and also bone displacement. These circumstances can lead to the death of neurons, and the demyelination of axons which causes some loss and damage to neurons. As Hudgins (1998) reports after a primary injury such as above, secondary injury occurs 30 minutes after and also that secondary injury is when the most critical damage occurs. This is when there is hemorrhaging in the gray matter of the spinal cord, which contains clusters of neurons and axons. This is when the most devastating damage occurs, and the results of this secondary injury causes paralysis, in most cases. Paralysis has a great effect on peoples lives, so Doctors are researching and experimenting different ways to inhibit growth in neurons in the spinal cord to cure paralysis. Doctors are experimenting with a couple of styles for regenerating glial growth. One option is transplanting fetal tissue into the damaged area and another option is to make the pre-existing cells functional.
Doctors have been experimenting mostly on rodents in order to see what the results showed. None of these experiments have been performed on humans, but will be in the near future. The process on influencing pre-existing cells is a very complicated procedure. After an injury, the axons of the cells are broken up and the myelin breaks away, also the damaged cell bodies shrink. This causes a gap between other neurons, thus making them unable to communicate with other cells, causing paralysis. Dr. Mary Bunge (1998) explains "regenerating neurons need some kind of supporting structure on which to grow. Such a substrate should also direct the growing neurons to their appropriate targets, allowing them to make connections that will transmit signals from one neuron to the next" (p.1). According to Travis (1997) One way of filling this gap in the axon is by using macrophages. Macrophages are bacteria and virus fighting white blood cells that also clean up foreign objects from the body. When a spinal cord is injured and the axons are in pieces, the macrophages arrive on the scene and begin to clean up the area. This abundance of cells, and proteins that are present, can create a bridge between the cells.
This mesh of cells and proteins does not occur naturally in the body, therefore growth cannot occur. It has been said that nerves cannot grow in any situation, but they can in the central nervous system due to a special protein found in the myelin. After the macrophages have been placed in the gap, the cells can begin to generate the axons and the mesh provides direction for the growing axons (Travis, 1997).
Another way to promote growth in neurons is by the use of a Nerve Growth Factor (NGF) along with Schwann cells, grown exogenously. When a neuron is damaged the axons become demyelinated causing cells to cease functioning. Experiments have been performed in rodents in which the scientists were able to restore function in their spinal cord. In the experiment the scientists inject a nerve growth factor to the injured area. A NGF used in this specific procedure was Neurotrophin-3. Neurotrophin-3 is one of the most common NGF's used because it has shown positive effects. According to Logan (1997) "In the visual system, remarkable regeneration can be promoted in the presence of myelin debris by neurotrophin application to the cell bodies of severed
axons" (p1372). After the neurotrophin-3 is injected into the cells, and after the cells have grown, the schwann cells need to be transplanted. The schwann cells used in this procedure are grown exogenously. These cells are used to remyelinate the axons to enable normal electrical impulses for communication. This method of spinal cord regeneration has been successful in rodents and will soon be used in humans. Dr. Bunge a NINDS grantee from the University of Miami (1997) reports that " by implanting pure schwann cells she achieved extensive remyelination of central nervous system axons in newborn rats with a genetic myelin deficiency. This work proved that peripheral nerve cells could survive and function appropriately when implanted into the central nervous system. Dr. Bunge recently expanded her work in the repair and remyelination of spinal cord axons after traumatic injury" (p.1).
Paralysis is a traumatizing and devastating diagnosis, and that is why doctors are researching and experimenting new ways to cure it. A more recent experiment is using fetal tissue to replace the damaged nerve tissue. In this procedure doctors would obtain fetal nerve tissue and transplant it into a human. The reason this would work is that the fetal tissue has not stopped growing yet, so it will continue to grow when transplanted. At the rate that technology is growing, it seems that soon enough spinal cord injury and paralysis will soon be helped, or maybe even cured.



References

Bunge, M. Promoting New Growth in Damaged Nerves. P. 1-2

http://www.mediconsult.com/noframes/spinal/shareware/research/growht.html

(World Wide Web), 1997


Finkel, E Stem Cells In Brain Have Regenerative Potential

The Lancet, 347, p.751 1996, March


Hudgins, L The Status Research: Effects of SCI. p. 1-6

http://www.erols.com.nscia/newsroom/scilife/status.html

(World Wide Web) 1998


Logan, A Spinal Cord Repair Takes A Step Forward

The Lancet, 349, p.1372 1997, May


Travis, J Repairing Severed Spinal Cords

MIT's Technology Review, 18, p.13 (1997, January)