With potential therapeutic implications, Stainier and a colleague also recently discovered that endothelial cells, which line the blood vessels, play a critical role in inducing the development, or proper differentiation, of red blood cells, the transporters of oxygen. When endothelial cells were removed from the developing zebrafish embryo, red blood cells did not form. When endothelial cells were restored, blood cells developed. (The researchers were able to conduct this experiment because the embryos can survive without blood for at least seven days.). Presumably, said Stainier, the endothelial cells act by releasing an as-yet-unidentified factor.
The finding represents the first demonstration in an animal model, Stainier said, that endothelial cells are necessary for the proper differentiation of red blood cells. He said he suspects the discovery, published in Development,5 will apply to the immune system's white blood cells, as well.
Identifying the factor released by endothelial cells could lead, said Stainier, to a mechanism for prompting naive, or undifferentiated, cells to develop into red blood cells, which could then be used to boost the blood supply. "The insights zebrafish can offer into human biology and medicine are boundless," said Stainier. "We will be learning from these animals for years to come."