Steered science.

Chris Mooney ("Research and Destroy," October) writes: "Embryonic stem-cell research (ESC) is another issue where conservatives have latched onto fringe science in order to advance moral arguments" But virtually everything positive about ESCs is hype from politicians, the media, or ESC researchers. The Democrats refuse to even acknowledge the existence of adult stem cells (ASCs), as shown in John Kerry's response to a question about them in the second presidential debate. Yet ESCs aren't even in clinical trials, while ASCs have been used to treat human disease since the 1950s. Eighty therapies currently use ASCs.

The only possible advantage of ESCs is its potential, but again Mooney is wrong in saying flatly: "It's well established that embryonic stem cells can generate any kind of tissue found in the body" We don't know that yet. Scientists have already discovered at least 14 types of ASCs that--even with limited plasticity--could eliminate the need for a "one-size fits all" cell. MacroPore of San Diego expects to use fat stem cells to make such repairs routine in as little as two years. Further, three different labs have presented evidence that an ASC can be "teased" into all three germ lines that make up all the cells of the human body. PPL Therapeutics has taken fully mature cow skin cells, reprogrammed them to become stem cells, and then converted these to heart cells.

Mooney presents Dr. Irving Weissman as a disinterested party, identifying him only as a "Stanford pathologist." Yet Weissman has appeared in commercials urging Californians to vote for California's Proposition 71 which would give $3 billion only to ESC research--much of it Weissman's. Mooney quotes Weissman saying, "Scientifically, there is no independently verified evidence today that a pure stem cell of one type--adult tissue, say blood forming--can turn into another tissue at all" Yet a search reveals a slew of studies having done just that. One study appeared in Nature Medicine in November 2000 where marrow stem cells from mice were converted into mature liver cells in the same animals. Among the co-authors: Irving Weissman.

Michael Fumento

Senior Fellow

Hudson Institute

Washington, D.C.

Chris Mooney responds:

Michael Fumento claims that an impressive number of studies have show adult stem cells to be capable of transforming into different tissue types. Yet, as I argued, while some studies have indeed suggested adult stem cells have such a capability, this claim--known as transdifferentiation--is extremely controversial. Top scientists say the studies in question aren't necessarily reliable. One needn't turn to Stanford's Irving Weissman for this point, even though he's in many respects the godfather of adult stem cell research. Distinguished cell biologists Elizabeth Blackburn and Janet Rowley, one a former and one a current member of the President's Council on Bioethics, have cautioned that "many of the reports on the properties of cells differentiated from adult stem cell preparations are to date preliminary and incomplete."