Growing Stem Cells
Last November saw major advances in cultivating human embryonic stem cells--a "holy grail" of biotechnology. Such cells can become any of the body's tissues, so the cultivation of them could lead to organs on demand. James A. Thomson and his colleagues at the University of Wisconsin described in Science how they coaxed days-old embryo cells to grow indefinitely in their undifferentiated state while retaining their ability to become specialized tissue cells. Days later John D. Gearhart of Johns Hopkins University and his co-workers reported a similar feat, using primordial germ cells (cells that would eventually become sperm and eggs). In unpublished work, researchers at Advanced Cell Technology in Worcester, Mass., say they fused nuclei from adult human cells with cow eggs that had their nuclei removed. The human nuclei commandeered the bovine cells, turning them into embryonic stem cells.