The New Generation of Medicine

Adult stem cells and the more controversial embryonic stem cells are both similar and distinct. Adult stem cells are found in certain parts of the body in specialized tissue that is able to renew itself. Typically, these cells can reproduce only the type of cell that they have become—stem cells from the liver will produce only liver cells. By contrast, embryonic stem cells have greater flexibility—they are able to differentiate into the various types of cells that form the human body. Until recently, it was believed that embryonic cells offered the greatest hope for treating disease. But in 2002, Verfaillie found that adult stem cells derived from bone marrow in mice are able to differentiate much like embryonic stem cells. Verfaillie dubbed these cells “multipotent adult progenitor cells,” or MAPCs. If adult stem cells like these can be used to generate various types of cells, it might be possible to harvest a person’s own stem cells for use in repairing tissue, thus reducing the risk of transplant rejection.

Before these cells can be used in treatments, however, “a large number of studies are still required to fully understand the potential of MAPCs,” Verfaillie says. The first clinical trials using MAPCs in humans are expected to begin at the U of M early this year. The trials will target Fanconi anemia, a rare, congenital disease that causes bone marrow failure and is ultimately fatal to young patients.

But however promising adult stem cells may be, Verfaillie strongly believes that embryonic cell research must also go forward. “It’s far too early in stem cell research to disregard one type over another,” she says. Verfaillie believes that side-by-side comparisons must be done to determine which type of stem cell is most useful in treating a particular disease or condition.

Embryonic stem cells, of course, have been the source of intense controversy, because they require the destruction of a blastocyst, or fertilized egg, typically at five days. Federal funding for research using embryonic stem cells is available only for work on cell lines that existed prior to President George Bush’s cutoff date of August 9, 2001. But Verfaillie notes that because these cell lines were grown in connective-tissue cells from mice, it is unlikely that they could ever be used to treat human patients. In addition, she says, techniques for deriving human stem cell lines have greatly improved since the presidential cutoff, resulting in better-quality and more diverse cell lines, crucial for researchers’ continued investigations.

And so in 2002, the university decided to conduct research on embryonic stem cell lines that fell outside of the federal-funding restrictions. “We saw the potential benefit of expanding research to include these cells,” says Cerra, adding that the U of M spent 18 months consulting with bioethicists, its general counsel, and others to ensure that regulatory restrictions—such as separating embryonic cell research from any federally funded resources—could be met. The university also decided to forgo state dollars. Reaction from the legislature was swift. Bills supporting and prohibiting the university’s choice were introduced in 2004—the bill against the research even proposed withdrawing all state funding of the university. (Both bills are currently in legislative limbo.)