Researchers from Duke University have just discovered a key protein involved in the repair of spinal cords in zebrafish which they believe has the potential to help develop a treatment that can be used for humans.
Unlike humans, the spinal cord of a zebrafish has the ability to completely recover after being severed and now scientists have been able to identify the protein that’s involved in this process. Furthermore, they believe that this discovery could help them to find ways to repair and regenerate human tissue.
From their observations, the team saw that as the severed spinal cord of the zebrafish starts to regenerate, a bridge begins to form. Cells from one end of the severed cord start to extend a distance of up to ten times their own length until they unite the gap. Once the gap has been bridged, nerve cells form and after a period of about 8 weeks, new nerve tissues completely fill the gap at the site of the injury. This results in a complete reversal of the paralysis experienced by the fish following the injury to the spinal cord.
The scientists wanted to find out what prompts this process and what molecules are involved. They did this by observing changes in the activity of the genes following the injury. Dozens of genes were activated by the injury, but the researchers found seven that secreted proteins involved in the repair. In particular, the levels of connective tissue growth factor were seen to rise sharply in the supporting cells that were involved in the formation of the bridge in the first fourteen days after the injury.
Following this discovery, the team used genetic techniques to delete the connective tissue growth factor, and found that the fish were unable to repair their severed spinal cord. As we share most of our protein-coding genes with zebra fish, this discovery was very exciting. Human connective tissue growth factor has almost 90% of the amino acid building blocks of the equivalent zebra fish protein. To test their theory further, the researchers added the human version of this protein to the injury site in the zebra fish spinal cord and found that it was able to boost regeneration. Just two weeks following the injury, the fish were no longer paralysed but were able to swim.
The team believe that due to complications in human spinal injuries, such as scar tissue, this protein alone is probably not sufficient to instigate regeneration in human spinal cords. However, they do plan to continue their investigations using mice, to see if they can further identify why zebrafish are able to regenerate and mammals are not, suggesting that it might be due to how the protein is controlled rather than how it is made up.
The study was published in the November edition of journal Science.