Brief Procedure Repairs Knees
Present only briefly in human embryos, stem cells grow into the 210 different types of cells in the body that eventually make up an entire human being. What makes stem cells unique—and uniquely valuable—is their lack of specialization and their ability to reproduce indefinitely. To isolate them, Gearhart’s team searched small samples of human fetal tissue for “primordial germ cells” that eventually would have become eggs and sperm. They then placed those cells on a “feeder layer” of mouse connective tissue cells, surrounded by a broth of nutrients and highly specialized growth factors, aiming for just the right atmosphere to allow the development of stem cells.
Once the results looked like stem cells and produced enzymes like stem cells, the study entered the critical phase. “The gold standard was seeing if the cells have true potential, if they’d develop into the three basic layers of cells [muscles, bones and nerves] found in all mammalian embryos,” says Michael Shamblott, Ph.D., a researcher on the project. “And ours did.”
The discovery likely will have sweeping long-term implications for medical practice, especially in such areas as repairing diseased organs, growing organs for transplants, speeding research on new drugs, facilitating gene therapy and numerous other innovations. The ability to isolate stem cells also will allow scientists to probe more closely the mysteries of human biological development.
“The potential of these unique, versatile cells for human biologic studies and medicine is enormous,” Gearhart says. “These cells will let us study human processes in a way we couldn’t before. Instead of having to rely on mice or other substitutes for human tissues, we’ll have a unique resource that we can start applying to medicine.”
Lana Skirboll, director of science policy at the National Institutes of Health, upon learning of the discovery, acknowledged, “If you had asked me last week if I would have predicted this, I would have said it’s far into the future.”