Stem Cell Gain: Bone marrow cells seem to have what it takes

The ongoing effort to find an adult stem cell that can morph into most, if not all, types of tissues has received a boost. Tests show that a rodent bone marrow cell similar to one found in people acts as a multipurpose stem cell, much as embryonic stem cells do.

The work, which appears in the June 23 Nature, suggests that the human version also has the potential to grow into many types of tissue. This quality could be of immense value in fighting diseases that arise from congenital defects or degeneration of organs, says study coauthor Catherine M. Verfaillie, a physician and hematologist at the University of Minnesota Medical School–Minneapolis.

Stem cells from human embryos can divide for indefinite periods and give rise to a vast array of specialized cells. However, difficult ethical issues arise because taking the cells destroys the embryos.

On the other hand, therapy using stem cells from adult bone marrow is less controversial. People healthy enough to provide their own marrow for stem cells would have the added advantage of avoiding immune rejection of those cells. However, adult cells previously tested in laboratory cultures haven’t multiplied rapidly or differentiated into many tissues.

Verfaillie and her team have found in human bone marrow a kind of adult stem cell that they call multipotent adult progenitor cells. “These cells didn’t appear to grow old in culture,” she says. The researchers reported earlier this year that multipotent adult progenitor cells proliferate abundantly in the lab and can differentiate into cells similar to liver cells.

To test the versatility of such a stem cell, the researchers identified the mouse version, collected and grew some in the lab, and injected these cells into a separate group of mice. The scientists found that the injected cells took up residence in the blood, bone marrow, spleen, liver, lung, and intestines of the mice receiving them.

Many of the cells then developed into tissues of those types.

“I’m very impressed by this work,” says stem cell biologist Curt I. Civin of the Johns Hopkins Medical Institutions in Baltimore. The cells grew abundantly in the lab and, once injected, didn’t show any signs of causing cancer, as embryonic stem cells sometimes do, he notes.

Verfaillie cautions that much research remains before multipotent adult stem cells can be tested in people. For example, scientists don’t know how the stem cells adopt the characteristics of the cells around them. The chemicals in the surrounding tissue might cue a cell to differentiate, she says.