WASHINGTON, D.C. (March 10, 2009)—Stem cells have long been touted as potential cures or treatments for a variety of ailments from paralysis to Parkinson's disease. After all, these cells (found in bone marrow, for instance, and also in human embryos, making their use a subject of much controversy) can potentially turn into a wide variety of cells with specific functions. Or, they can throw off proteins—such as growth factors—that help other cells grow. Stem cells injected into a paralyzed patient’s spine, for instance, might help regenerate nerve tissue.

But while the flexibility of these cells is the key to their usefulness, they might not be quite as flexible as we once thought, says Julia Dory Ransohoff, 17, one of 40 finalists in the Intel Science Talent Search here in Washington this week for the competition’s final rounds. (We've been on hand to live-Twitter and to profile a few projects, everything from Splenda in drinking water to whether parents should discuss their drinking with their kids to cellulosic ethanol.)

A student at Menlo Atherton High School in Menlo Park, Calif., Ransohoff tested the effectiveness of adult bone marrow stem cells in treating damaged heart tissue following a heart attack. Doing her work in a lab at Stanford University, she discovered that stem cells taken from female donors triggered more of an immune system response—in which the host attacks the transplanted cells—than stem cells taken from male donors. In other words, donor gender matters.

Ransohoff was not expecting these results. First, it wasn’t clear that donor gender would matter because of how flexible stem cells are thought to be. But if it did, “I was expecting to find the reverse,” she says, because women tend to have better heart health. She thought that perhaps whatever gives women’s hearts a slight protection against heart attacks might transfer with the transplanted stem cells. But it didn’t. “We were all very surprised,” she says.

She entered her project in the Intel Science Talent Search “on a lark” she says, and since Intel’s headquarters are located nearby in Santa Clara, Calif., people from the company actually showed up in person to announce her finalist and semi-finalist status. “They surprised me twice at school,” she says.

Also surprising? Getting to meet President Obama on the exact day he announced changes in the federal policy toward embryonic stem cell research, reversing a Bush administration ban on federal funding. On Monday, after talking with reporters about her stem cell project, Ransohoff zipped over to the White House (with her 39 fellow finalists) to talk with Obama. “It was a little surreal,” she says. “I felt like I was watching TV.” Though her project didn’t involve embryonic stem cells, she’s thrilled to learn that such cells could be an area for her future research: “I’m excited to be 17 and in a field that’s just been released and let out into the open."

See Ransohoff discuss her project in this video.

Photo of Julia Ransohoff by Laura Vanderkam/copyright Scientific American