The safety and efficiency of bone marrow transplants may improve due to the discovery of a rare molecule that establishes blood stem cells in their niche within the bone marrow.

The molecule—Robo4—is found only in the hematopoietic stem cells and in the endothelial cells of blood vessels. According to the new study findings, published in Cell Stem Cell (2011;8:72-83), hematopoietic stem cells—the key components in bone marrow transplants—use Robo4 to anchor themselves in the bone marrow where they reside.

In an increasingly common alternative to traditional bone marrow transplants, repeated drug injections are administered to usher stem cells away from bone marrow and into the bloodstream, from which they can be harvested and eventually groomed into different types of cells. The Robo4 discovery, however, creates an opportunity to find agents that can block the molecule in a safer and more effective fashion.

“If we can get specific and efficient inhibition of Robo4, we might be able to mobilize the hematopoietic stem cells to the blood more efficiently,” explained E. Camilla Forsberg, an assistant professor of biomolecular engineering at University of California–Santa Cruz, in a statement describing her team’s work.