Even non-embryonic stem cells might be able to produce many types of specialized cells, but researchers are still trying to work out the details.
Recent studies show that some cells taken from human adult tissues seem capable of growing into many types of specialized cells, even ones that they would not become naturally. This may allow researchers to grow a wide variety of specialized cells for transplant or study.
Below are examples of tissue stem cells that appear especially versatile. The work is exciting, but as with any scientific study, they must be replicated in more laboratories before scientists can fully trust the conclusions. Scientists working with these versatile cells regard embryonic stem cells as the gold standard for gauging cells' ability to transform into other cell types.
In 2007, multiple researchers reported that both mouse and human cells could be converted to cells that behave like embryonic stem cells. Researchers believe these so-called induced pluripotent stem (iPS) cells will be incredibly valuable for studying disease and potentially even cell therapy. Several caveats remain however. As of mid-2008, these so-called induced pluripotent cells still need to be more extensively compared to embryonic stem cells, and the technique to make the cells requires permanently inserting multiple gene copies into the cells, making them more variable and less predictable.
Amniotic fluid stem cells. Human placentas seem to contain a particularly powerful source of stem cells. These cells appear easy to grow in the lab, and they can transform into nerve cells, blood vessel cells, liver cells, cartilage, bone and cardiac muscle—almost as many types of tissues as embryonic stem cells. The work still must be confirmed by independent laboratories.
Multipotent adult progenitor cells. Scientists report that these cells within the bone marrow can form all three of the major categories of tissue. Some aspects of this work have been replicated in separate laboratories, and other aspects await confirmation.
Testes cells. Cells within the testes of mice seem capable of generating an array of different kinds of cells in laboratory dishes, including heart, brain and skin cells. One company claims to have similar results from human biopsy specimens.
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Can stem cells from one tissue be grown into many other types of cells?. Nat Rep Stem Cells (2007). https://doi.org/10.1038/stemcells.2007.19