08 May 2001

Stem cells from the bone marrow of adults may be as flexible as embryonic stem cells, according a study in the current issue of Cell. Researchers at Yale, New York University, and Johns Hopkins found that these cells, which continuously replenish the supply of red blood cells and various types of immune cells, give rise to epithelial cells in a variety of organs.

The researchers took advantage of a technique whereby the bone marrow stem cells of a female mouse can be destroyed by irradiation and then replaced by stem cells from a male mouse. Researchers can later identify these stem cells by the the presence of a Y-chromosome.

Eleven months after receiving transplanted stem cells, female mice were found to have cells containing Y-chromosomes in organs such as the liver, lung, gastrointestinal tract, and skin. The researchers demonstrated that these were epithelial cells integrated into the different organs, as opposed to immune cells such as macrophages that might be circulating through the organs. They speculate that stem cells from the marrow may make their way to these sites as part of normal cell turnover or in response to injury.

The methods used in this particular study did not allow the researchers to determine whether bone marrow stem cells can differentiate into glia or neurons. However, such studies are underway. "There is something going on in the neural tissue," said Neil Theise of New York University, one of the authors. "We have to confirm that it's not just circulating white blood cells, but I'm optimistic that we have neural engraftment."—Hakon Heimer