Stem Cells: The Hope And The Hype

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Even the true believers among scientists, however, dispute eager politicians who have called for a Manhattan Project approach to research. "I hate to say it, but biology is more complicated than splitting the atom," Witte says. "The physicists on the Manhattan Project knew what they needed to accomplish and how to measure it. In biology, we're codeveloping our measurement tools and our outcome tools at the same time." Indeed, a massive centralized effort controlled by the Federal Government could do more harm than good. The key is to have the broadest cross section of scientists possible working across the field. When it comes to such an impossibly complicated matter as stem cells, the best role for legislators and Presidents may be neither to steer the science nor to stall it but to stand aside and let it breathe. [This article contains a diagram. Please see hardcopy or pdf.] Making Sense of STEM CELLS WHAT THEY ARE Stem cells are nature's master cells, capable of generating every one of the many different cells that make up the body. They have the ability to self-renew, which means that they are theoretically immortal and can continue to divide forever if provided with enough nutrients. Because they are so plastic, they hold enormous promise as the basis for new treatments and even cures for disorders ranging from Parkinson's and heart disease to diabetes and even spinal-cord injury

WHERE THEY COME FROM

LEFTOVER OR DEAD-END IVF EMBRYOS

Why they are useful More than 400,000 embryos created during in vitro fertilization lie frozen in clinic tanks in the U.S. Many of them will be discarded, so the embryonic stem cells that exist inside them could be salvaged

Drawbacks The freezing process may make it harder to extract stem cells. Some of the embryos were the weakest ones created by infertile couples and may not yield high-quality stem cells

ADULT STEM CELLS Why they are useful They exist in many major tissues, including the blood, skin and brain. They can be coaxed to produce more cells of a specific lineage and do not have to be extracted from embryos Drawbacks They can generate only a limited number of cell types, and they are difficult to grow in culture

NUCLEAR-TRANSFER EMBRYOS Why they are useful These embryos are created using the technique that created Dolly, the cloned sheep. Stem cells can be custom-made by inserting a patient's skin cell into a hollowed human egg. Any resulting therapies would not run the risk of immune rejection

Drawbacks The process has not yet been successfully completed with human cells, and it requires an enormous amount of fresh human eggs, which are difficult to obtain

UMBILICAL-CORD CELLS

Why they are useful Although they are primarily made up of blood stem cells, they also contain stem cells that can turn into bone, cartilage, heart muscle and brain and liver tissue. Like adult stem cells, they are harvested without the need for embryos

Drawbacks An umbilical cord is not very long and doesn't hold enough cells to treat an adult

The Process 1 EMBRYO

An egg is fertilized or cloned to form an embryo. The embryo begins to divide

2 1 TO 5 DAYS