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The Scientist 14[23]:20, Nov. 27, 2000 http://www.thescientist.com/yr2000/nov/research_001127.html RESEARCH Stem Cells Tapped to Replenish Organs Embryonic or adult? The superior source depends on the tissue By Douglas Steinberg Editors Note: This is the second of two articles on issues raised by recent stem cell discoveries. The first article appeared in the November 13 issue "All politics is local" was a famous maxim of Thomas "Tip" O'Neill, the late speaker of the House of Representatives, and the same can be said of medically useful stem cells. Progenitor cells may prove to be more or less pluripotent in the lab, but if they don't succeed on a local level in the body, they won't cure anything. They must be capable of being coaxed into differentiating reliably into the cell types that populate particular organs. How much can embryonic stem cells (ESCs) and adult stem cells (ASCs) replenish tissues of the brain, pancreas, liver, heart, and blood? So far, researchers have manipulated ESCs to generate a broad span of cell types. ASCs have yielded a narrower range, partly because several subtypes haven't been isolated yet. The phenomenon of transdifferentiation, however, promises to extend the capabilities of ASCs. And as studies proliferate in the wake of discoveries and the issuance of new guidelines by the National Institutes of Health, the relative advantages and disadvantages of ESCs and ASCs could change considerably within the next few years. ******************