Study Reveals Secret of Zebrafish

Scientists at Monash University in Australia have found how the zebrafish heals its spinal cord after injury.

A zebrafish, Danio rerio, in an aquarium (Azul)

The zebrafish, Danio rerio, is a tropical fish belonging to the family Cyprinidae. This species is a popular aquarium fish and is also an important model organism in scientific research. It has the amazing ability to regenerate fins, skin, the heart and the brain.

A new study in the Journal of Neuroscience describes the role of a protein in the remarkable self-healing ability of the fish. The finding could eventually lead to ways to stimulate spinal cord regeneration in humans.

“When the spinal cord is severed in humans and other mammals, the immune system kicks in, activating specialized cells called glia to prevent bleeding into it,” explained study co-author Prof Peter Currie.

“Glia are the workmen of nervous system. The glia proliferate, forming bigger cells that span the wound site in order to prevent bleeding into it. They come in and try to sort out problems. A glial scar forms.”

However, the scar prevents axons, threadlike structures of nerve cells that carry impulses to the brain, of neighboring nerve cells from penetrating the wound. The result is paralysis.

“The axons upstream and downstream of the lesion sites are never able to penetrate the glial scar to reform. This is a major barrier in mammalian spinal cord regeneration,” Prof Currie said.

In contrast, the zebrafish glia form a bridge that spans the injury site but allow the penetration of axons into it. The fish can fully regenerate its spinal cord within two months of injury. “You can’t tell there’s been any wound at all,” Prof Currie said.

The team discovered the protein, called fibroblast growth factor (fgf), controlled the shape of the glia, and accounted for the difference in the response to spinal cord injury between humans and zebrafish. The scientists showed the protein could be manipulated in the zebrafish to speed up tissue repair even more.

“The hope is that fgf could eventually be used to promote better results in spinal cord repair in people,” Prof Currie concluded.

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Bibliographic information: Yona Goldshmit, Tamar E. Sztal, Patricia R. Jusuf, Thomas E. Hall, Mai Nguyen-Chi, and Peter D. Currie. 2012. Fgf-Dependent Glial Cell Bridges Facilitate Spinal Cord Regeneration in Zebrafish. The Journal of Neuroscience 32(22): 7477-7492. doi:10.1523/JNEUROSCI.0758-12.2012