The title of the letter in the Dec. 3 edition of the journal Nature — “Live-animal tracking of individual haematopoietic stem/progenitor cells in their niche” — doesn’t begin to describe it, this real-life, real-time view of a single stem cell making its way to its ultimate home inside the bone-marrow cavity of a living mouse.

As David Scadden, co-director of the Harvard Stem Cell Institute and director of the Center for Regenerative Medicine at Massachusetts General Hospital (MGH) explains, it was first hypothesized 30 years ago that “stem cells have to have a particular location and a particular tissue type in order to survive, and without that they won’t be able to produce cells such as blood cells.”

In 2000, researchers working in drosophila — fruit flies — verified the hypothesis. In their letter to Nature, Scadden, postdoctoral fellow Cristina Lo Ceslo, Charles P. Lin of MGH’s Wellman Center for Photomedicine, and colleagues, describe tracking single stem cells transplanted into living mice.

Scadden, a hematologist-oncologist who provides cancer patients with bone-marrow transplants — which are essentially blood stem cell transplants — says, “we inject cells into a vein, and some of them find their way to where they need to end up, but we need to know what happens to them. And more important, we need to discover what we can do to increase the efficiency of the process, to make sure that the stem cells ‘take’ and thrive.”

Now, Scadden says, “we can actually watch the cells divide; we can see the process by which cells engraft, and regenerate the bone marrow.”

The most exciting thing coming from this work, Scadden says, is that we know there are drugs that improve stem cells getting to where they need to go and drugs that appear to stimulate the successful establishment of the transplanted stem cells. The next step, he says, is working with those drugs in clinical trials in marrow-transplant patients.

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