New study shows partial recovery in spinal cords of rats

New study shows partial recovery in spinal cords of rats

A new study showed that combining partially differentiated stem cells with gene therapy could promote the growth of new “insulation” around nerve fibers in the damaged spinal cords of rats.  Mimicking the activity of two nerve growth factors, the treatment was shown to also improve the rats’ motor function and electrical conduction from the brain to the leg muscles. 

Study authors hope the finding will eventually lead to discovering new ways of treating spinal cord injury in humans.  The study provides the best demonstration to date that producing a nerve-insulating substance called myelin can lead to functional improvements in animals with spinal cord injury.

In previous studies the loss of myelin around nerve fibers were shown to contribute to the impaired function after a spinal cord injury, but it has not been clear whether promoting new myelin growth in the spinal cord can reverse the damage until the latest study.  Other researchers have suggested remyelination could possibly repair the spinal cord, but the new study is the first to show that it can work. 

Appearing in the July 27, 2005 issue of the Journal of Neuroscience, the study was funded in part by the National Institute of Neurological Disorders and Stroke, part of the National Institutes of Health.  Researchers in the study took special cells called glial-restricted precursors from the spinal cords of embryonic rats.  The precursor cells develop from stem cells and are specialized so they can form only two kinds of cells – astrocytes or oligodendrocytes. 

Researchers injected the treated precursor cells into the spinal cords of rats with a contusion spinal cord injury, caused by an impact to the spinal cord.  Other groups of spinal cord injured rats received just precursor cells or other treatments that were used for comparison. 

Evaluated weekly for six weeks after the treatment using a behavioral test called the Basso-Beattie-Bresnahan scale, which measures characteristics like weight support, joint movements and coordination, the researchers found the majority of rats treated with the combination of precursor cells and gene therapy improved significantly on both tests.  Researchers also used an electrical current test. 

Combination therapy improved the rats’ ability to walk and allowed about a 10 percent improvement on the electrical current test.  The rats that received the other treatments did not improve significantly, and untreated rats did not have any electrical activity that passed through the damaged spinal cord.  When studying the damaged spinal cord tissue after the combined treatment, researchers found that many of the transplanted cells survived and migrated within the cord and about 30 percent of them developed into myelin-producing oligodendrocytes.

The researchers are now investigating ways to improve the combination therapy with additional genetic modifications to transplanted cells, and they plan to test similar techniques that start with undifferentiated embryonic stem cells instead of glial-restricted precursor cells.  The embryonic stem cells would be better for human studies, according to the study’s lead researcher, than glial-restricted precursors because they are more readily obtained.


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