Region where adult blood stem cells arise identified with time-lapse imaging

David Traver (right) and Neil Chi used zebrafish, grown in tanks at UCSD, to track blood-forming stem cells. Courtesy of UC San Diego.

Biologists at the University of California-San Diego have used time-lapse imaging to identify the specific region in vertebrates where adult blood stem cells arise during embryonic development. The discovery could lead to safer and more effective stem cell therapies for patients with leukemia, multiple myeloma, anemia and other diseases of the blood or bone marrow.

The researchers imaged the process in which primitive embryonic tissues first produce the parent stem cells that produce all adult blood cells. These cells--called haematopoietic stem cells (HSCs)--are responsible for the benefits of bone marrow transplants.

Currently, transplantation involves infusing donor stem cells into a patient's bone marrow. The procedure hopefully generates new healthy blood cells, but it also comes with serious risks such as immune rejection. Generating the stem cells using the patient's own precursor cells might overcome the risk and complication of bone marrow transplants, but requires understanding the molecular processes of haematopoietic stem cells.

The researchers used fluorescent reporter transgenes, confocal time-lapse microscopy, and flow cytometry to study zebrafish, demonstrating that haematopoietic stem cells arise directly from cells lining the floor of the dorsal aorta. They imaged the process in living embryos and also documented the steps in of haematopoietic stem cell formation.

In a related paper, researchers from Erasmus Medical Center in Rotterdam, The Netherlands imaged haematopoietic stem cells emerging from the aortic endothelium in a mouse embryo.

Click here to see a video on the UC San Diego work.

Research papers:
Haematopoietic stem cells derive directly from aortic endothelium during development

Julien Y. Bertrand, Neil C. Chi, Buyung Santoso, Shutian Teng, Didier Y. R. Stainier & David Traver doi:10.1038/nature08738

In vivo imaging of haematopoietic cells emerging from the mouse aortic endothelium
Jean-Charles Boisset, Wiggert van Cappellen, Charlotte Andrieu-Soler, Niels Galjart, Elaine Dzierzak & Catherine Robin doi:10.1038/nature08764