Zebrafish Lead Scientists to Origin of Stem Cells

Ronnie Steinitz/Guardian

After identifying the location of stem-cell production in the blood vessels of zebrafish, biologists at UCSD hope to one day use the information to simplify human medical procedures like bone-marrow transplants.

In the future, scientists will ideally be able stimulate the growth of a sick patient’s own stem cells, then re-direct them to the area where they are needed — such as the bone marrow. This would greatly decrease the chances of infection or graft-versus-host disease, in which the donor cells reject or attack the body.

The research team that discovered the location was headed by assistant professor of biology David Traver, postdoctoral fellow in Traver’s laboratory Julien Bertrand, assistant professor of medicine Neil Chi and professor of biochemistry at UC San Francisco Didier Stainier.

Bertrand said he thought zebrafish might be good cell providers because they have proven to be a standard test model for other vertebrates, including humans. The zebrafish embryo is also more accessible in its developmental stages than the traditional lab rat.

“[The formation of blood cells] has been thoroughly described in the mouse embryo, but since mouse development occurs in utero, it is not accessible for direct imaging,” Bertrand said. “Zebrafish development — on the other hand — occurs in a petri dish, because fertilization is external in fish.”

The cells — more specifically known as hematopoietic stem cells (HSCs) — have the ability to generate many types of cells. These include white blood cells, which affect the immune system, and red blood cells like platelets, which help in clotting.

According to Bertrand, this discovery is an important step toward understanding how to produce HSCs from types of artificial stem cells that are either more readily available or more limited. These HSCs would then have the potential to create any cell the body might need.

“[Through imaging,] I could observe the ‘transformation’ of flat endothelial cells along the aorta into round [bone-marrow] stem cells,” Bertrand said.

Now that scientists have identified the area where HSCs are produced, they can begin trying to produce them independently of a donor. Patients with blood or bone-marrow diseases — like cancer or leukemia — would undergo a transplant with HSCs that are already compatible with their immune systems.

Because the zebrafish embryo is transparent, biologists easily observed and studied the growth of the fish as they developed in their eggs.

Readers can contact Megha Ram at [email protected].

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