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Adult Stem cell 'breakthrough' is hype - study Adult stem cells, touted as the raw material for the organ farms of the future, are proving to be far more disappointing than their defenders claim, two new studies warn. Scientists have already discovered that stem cells taken from embryos at their earliest stage have the remarkable ability to grow into almost any organ of the body. Their goal is to coax these cells in growing into skin, bone, brain or nerve cells in a lab dish, then harvest and transplant them into a patient. Ethical controversy But the use of cells taken from embryos is fraught with ethical controversy, and many countries have laws that ban or tightly control the practice. In the past few years, intensifying interest has focussed on stem cells taken from adult tissue, such as blood, brain and muscle. Recent studies A series of recent studies have encouraged a blaze of optimism that these immature cells can be reprogrammed to grow into multiple types of cells, thus providing a nearly limitless — and uncontroversial — source of transplant material. The apparent breakthrough has come from mixing these precursor cells with embryos cells in "co-cultures" in which, it is thought, the reprogramming takes place. The adult stem cells, according to this theory, are genetically wiped clean and converted to their highly potent embryonic counterparts. But two studies published in Nature, the British weekly science journal, say these assumptions are far too optimistic. Stem cell not reprogrammed They found that in many instances, the adult stem cell was not reprogrammed — it simply melded with an embryo cell. That is bad news, because it means that the adult cell had to co-opt an embryonic counterpart in order to become a cell with potential therapeutic use, said Austin Smith, a University of Edinburgh professor. In other words, it did not add to the number of miracle cells. Need for caution "This suggests a need for caution with regard to the therapeutic use of adult tissue stem cells," he said. "If they only make other tissues by fusing existing cells rather than producing new cells, their utility for tissue repair and regenerative medicine will be greatly restricted." Smith's team made the discovery about the hybrids by tagging mouse brain cells with green fluorescent protein. This marker was then discovered in "co-culture" cells that behaved like embryonic stem cells. Scientists led by Naohiro Terada of the University of Florida in Gainesville separately arrived at the same discovery about cell fusion. Fusion problem They found that adult cells from either mouse bone marrow or brain, grown in the same dish as embryonic stem cells, fused spontaneously to produce hybrids able to produce muscle, nerve and other cell types. The extent of the fusion problem is unclear, but if the results are confirmed by tests on animals, they are "a warning to the overzealous trend" in stem-cell research, it said. "I still support adult stem-cell research and I really would like to see that blood stem cells can turn into brain or liver cells. That would be great," Terada told AFP. "But before concluding that, maybe we should be more careful. We can expect real prospects from stem cell research when we have a stronger foundation (of knowledge)," he said. - AFP Bob Martone [log in to unmask] http://www.samlink.com/~bmartone ---------------------------------------------------------------------- To sign-off Parkinsn send a message to: mailto:[log in to unmask] In the body of the message put: signoff parkinsn