 By LEE BOWMAN Scripps Howard News Service January 09, 2007
"Our hope is that these cells will provide a valuable resource for tissue repair and for engineered organs, as well," said Dr. Anthony Atala, senior researcher and director of the Institute for Regenerative Medicine at the Wake Forest University School of Medicine. He and colleagues at Wake Forest and Harvard Medical School reported their findings on the broad potential of amniotic stem cells in a study published Sunday in the journal Nature Biotechnology. The new cell lines may represent a compromise between the use of stem cells derived from discarded human embryos, which have the potential to develop into any type of human cell, but carry ethical concerns for some people, and adult stem cells, which can be induced to develop into other types of cells, but have less flexibility and more problems with universal acceptance in their new hosts. Atala said it has been known for decades that both the placenta and amniotic fluid contain a number of different progenitor cell types from the developing embryo, including fat, bone and muscle. "We asked the question: 'Is there a possibility that within this population, we can capture true stem cells? And the answer is yes.' " The researchers have determined that about 1 percent of the stem cells in amniotic fluid are able to give rise to many of the specialized cell types found in the human body. Atala said it remains to be seen whether all types of cells can be derived from the amniotic cells, but, "So far, we've been successful with every cell type we've attempted to produce from these cells." The specialized cells generated from the stem cells include all three classes of cells found in developing embryos. The researchers have been working with the amniotic cells for seven years. "It took us this long to verify that we had a true stem cell," Atala said. The study notes that the cells were harvested from backup amniotic fluid samples obtained during amniocentesis, a prenatal test that examines cells in the fluid to diagnose certain genetic disorders. The researchers also have been able to isolate similar stem cells from "afterbirth" -the placenta and other membranes that are expelled from the uterus after a baby is delivered. The scientists project that with 100,000 specimens, they could theoretically supply 99 percent of the U.S. population with perfect genetic matches of stem cells for transplantation. In addition to being easily obtained, amniotic stem cells can be grown in large quantities, because they typically double every 36 hours. They do not require guidance from other cells for their development, and they do not produce tumors, which have proven to be a problem with some other types of stem cells. Functional tests of the new cell lines included implanting neural cells generated from mice into a degenerative brain disease. The cells grew and "re-populated" the diseased areas. Also, bone cells produced from the stem cells were successfully used to grow bony tissue in mice, and liver cells were able to function as well. Atala said at this point that he does not think the amniotic cells can completely replace the role of embryonic cells in either research or eventual clinical use. "They are yet another source of stem cells that have a great deal of potential, but I don't know they will replace anything," he said. The researcher made headlines last spring as head a team based at Harvard that reported the first generation of complex human organs -partial replacement bladders grown from their own bladder cells -for seven young patients at Boston's Children's Hospital. Atala said while the amniotic cells have great promise in the field of tissue engineering, he does not expect any attempt to use them for human therapy for several more years.
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