Stem Cell Research and the Treatment of Spinal Cord Injuries

Stems cells seem to be a buzz word in today's society; and however controversial the topic may be, their uses are numerous. One particular use is in the treatment of spinal cord injuries. Researchers are currently looking into stems cells as an option for repairing cells and/or tissue that is injured in the spinal cord, one of the most debilitating injuries. Spinal cord injuries often lead to full or partial paralysis, a condition that can severely impact one's quality of life. So, putting the controversy of stem cell use and harvesting aside, how exactly can stem cells help in improving the lives of those with spinal cord injuries?

Before one can understand the specifics of how the stem cell can work to heal, they must first understand the basics of the stem cell itself. According to the National Institutes of Health stems cells serve "...as a sort of repair system for the body...When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function." (2006). It is this unique characteristic that makes the stem cell such a valuable cell in body healing including muscle cell replacement, red blood cell replacement, and brain cell replacement. However, there are also different types of stem cells, each with different properties. The one most publicized, and thought of with the most promise, is the embryonic stem cell.

The embryonic stem cell is the most primitive of the body's stem cells and has the ability to become any of the different stem cells. These cells get their name from their place of development. Embryonic stem cells are derived from embryos from fertilized eggs. However, the National Institutes of Health note that "They are not derived from eggs fertilized in a woman's body," but are instead donated to in vitro fertilization clinics after in vitro (fertilization) had been performed (2006).

Adult stem cells are unspecialized cells that are found in specialized tissue of the body. As the stem cells renew themselves there, they become specialized for the type of tissue present. Unfortunately, "Adult stem cells are rare and difficult to identify, isolate, and purify but are capable of making identical copies of themselves for the lifetime of the organism. There are insufficient numbers of cells available for transplantation and adult stem cells do not replicate indefinitely in culture" (Christopher and Dana Reeve Foundation, 2008). It is for this reason that embryonic cells show such promise medically. Adult cells lack the changeability, and the ability to replenish, of the embryonic cells, and thus embryonic cells are necessary if stems cells are to be of use in the treatment of spinal cord injuries.

A spinal cord injury occurs when a disc or vertebrae of the spinal column is broken, shifted, or otherwise injured. More often than not, when the spinal column is injured, so too is the delicate spinal cord. Furthermore, since the central nervous system (composed of the brain and spinal cord) is responsible for communications between brain and body, spinal cord injuries affect, to varying degrees, body functions. According to the National Institute of Neurological Disorders and Stroke (2008), "Most injuries to the spinal cord don't completely sever it. Instead, an injury is more likely to cause fractures and compression of the vertebrae, which then crush and destroy axons..." Axons are a part of the nerve that carry signals or information through the spinal cord to the body or brain. Thus, a slight injury may only affect the body until it heals, while other injuries may damage too many nerves and cause permanent full or partial paralysis. Furthermore, partial damage may cause swelling that "...cuts off the blood supply to the neurons and glial cells" causing additional damage to other spinal cells, and immune cells that rush to the site of the injury.

Now that both stem cells and spinal cord injuries are understood, we can begin to delve into the world of stem cell use in the treatment of spinal cord injuries. It was long held that the spinal cord, once injured, was unable to heal itself. However, Johns Hopkins study published in 2007 unveiled the idea that by transplanting stem cells into the injured spinal cords survived, and some even grew (Physorg, 2007). Some of the transplanted nerve cells also connected with the spinal cord cells of the rats being used. This promotes the idea that transplanted cells have the potential to restore communication between brain and spinal cord.

A similar 2005 study found that stems cells injected into mice migrated "...up the spinal cord and develop into multiple different neural cell types, including neurons and oligodendrocytes, the cell type that forms insulating myelin sheaths around nerves" (Lovgren, 2005). Researcher Aileen Anderson of the Department of Physical Medicine and Rehabilitation at the University of Irvine commented on the study saying, "We show that these cells make connections with the nervous system of the mouse in a way that is appropriate...and could mediate recovery" (Lovgren, 2005). Another Irvine study through UC Irvine, led by Hans Keirstead, specified that the stem cell breakthrough was thought to be most effective during the acute phase of a spinal cord injury. This particular phase is between the first week of the injury and around two to three months after. After about two to three month mark, the injury becomes a chronic one. During the chronic phase scar tissue fills the space between the neuron cell, preventing crucial myelin sheath replacement. However, in acute spinal cord injuries, Keirstead's research yielded myelin tissue growth, and within two months the rats of the study showed "significant improvements in walking ability in comparison to injured rats who received no treatment" (Medical News Today, 2005). This is because the myelin is essential in protecting the nerves and their function, when stripped away due to injury or damage by disease, motor and sensory difficulties most often result, with the most serious being paralysis.

Clearly, there is still along way to go before stem cells can be used to treat spinal cord injuries in humans, but research is the key. With the research results available now, and further research, it seems only a matter of time before nerve damage, and myelin sheath replacement will be an option in acute spinal cord injury cases. Perhaps lifetime paralysis won't have to be the inevitable result of serious spinal cord injury.

References:

Christopher and Dana Reeve Foundation. (2008). Human Embryonic Stem Cell Research. Retrieved April 9, 2008, from http://www.christopherreeve.org/site/c.geIMLPOpGjF/b.3799979/k.6763/Human_Embryonic_Stem_Cell_Research.htm

Lovgren, S. (2005). Stem Cells Repair Damaged Spinal Cords in Mice. Retrieved April 9, 2008, from

http://news.nationalgeographic.com/news/2005/09/0920_050920_spinalcord.html

Medical News Today. (2005). Stem Cell Treatment Improves Mobility After Spinal Cord Injury. Retrieved April 9, 2008 from http://www.medicalnewstoday.com/articles/24159.php

National Institute of Neurological Disorder and Stroke. (2008). Spinal Cord Injury: Hope Through Research. Retrieved April 9, 2008, from http://www.ninds.nih.gov/disorders/sci/detail_sci.htm#106273233

Physorg. (2007). Study: Spinal Cord Can Repair Itself. Retrieved April 9, 2008, from http://www.physorg.com/news90689620.html

The National Institutes of Health. (2008). Stem Cell Basics. Retrieved April 9, 2008, from http://stemcells.nih.gov/info/basics/basics3.asp