For more than a decade, researchers have touted stem cells as the most promising advance in medicine since antibiotics. And this winter, when President Obama lifted the Bush administration's ban on federal funding for embryonic-stem-cell research, talking heads buzzed that his decision could bring scientists that much closer to cures — not just treatments — for conditions like heart failure, spinal-cord injuries and Alzheimer's disease. Biologists around the world toasted their new prospects with champagne. "Lifting the ban will free us up to use additional cell lines," says Jack Kessler, director of the Feinberg Neuroscience Institute at Northwestern University. "It's very important for science."
The hype surrounding stem cells runs high these days. But getting the straight story — where the cells come from, what they do, and why they warrant executive orders and billions in research dollars — is surprisingly difficult. Making sense of the torrent of stem-cell research findings, separating the false claims from the scientists and studies that matter, requires an unusually well-honed baloney detector. In this comprehensive survey of the stem-cell landscape, we've done the vetting for you: hashing out the core science, analyzing the challenges, and getting firsthand insight from the patients themselves.
Scientists talk up all types of stem cells and techniques to create them. But don't feel overwhelmed — much of the jargon can be boiled down to these fundamental terms.
Embryonic stem cells: The Swiss Army knife of regenerative science, these cells are harvested in the early fetal stage and have the unique characteristic of pluripotency, meaning that they can turn into any one of more than 200 tissue types. This makes them ideal for regenerating diseased heart tissue, repairing spinal cords, and replenishing brain cells. But to critics who believe that human life begins at conception, harvesting these cells is akin to killing a baby.
Induced pluripotent stem (iPS) cells: These cells are as close as you'll get to a fountain of youth. Inserting genes responsible for embryonic pluripotency into adult skin cells effectively rewinds their developmental clock and gives them embryonic-like powers to morph into heart, cardiac and other tissue types. An added bonus: No embryos necessary.
Somatic-cell nuclear transfer: This process birthed the famous cloned sheep Dolly. The basics: Take an egg cell and replace its nucleus with the genetic material of an adult cell from the organism to be cloned. Shocking the cell yields an embryo with the same DNA as the donor, which eliminates the risk of an immune reaction. But cloning humans may carry too much ethical baggage to be truly worthwhile, especially given the viability of iPS cells, which also contain a patient's own DNA.
Cord-blood stem cells: These multipotent stem cells are derived from babies' umbilical cords. Most of them are precursors for blood and immune cells, so they aren't as versatile as embryonic or induced pluripotent adult cells. Recently, however, cord-blood stem-cell transplants have become a viable alternative to bone-marrow transplants in treating blood disorders like leukemia, especially when a bone-marrow match can't be found.single page
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