Embryonic stem cells have a number of distinctive properties.
That cell, and its immediate descendents, are called "totipotent" stem cells because they form every tissue in the body. Specialization starts almost immediately, as the multiplying cells form a ball called a blastocyst. Inside the blastocyst are "pluripotent" or "embryonic" stem cells that can form just about every cell except the placenta.
It is the descendants of these embryonic stem cells that form the skin in your eyelids and the hair of your eyelashes. They form the muscle cells that raise your eyelid and nerve cells that detect light in your eye.
Embryonic stem cells, however, dislike the status quo. Normally, whether in the body or the lab, they quickly specialize. Within days, their job is done and they disappear.
One of the first medical experiments with adult stem cells used cells gathered from aborted fetuses, a controversial source to those who oppose abortion. About a decade ago, Swedish researchers started injecting fetal brain tissue into the brains of people with Parkinson's, a disease that gets unrelentingly worse. Over the ensuing years, many of these people improved, which helped spark the current fetish for stem cells. We previously covered the role of neural stem cells in learning; we'll get to stem cells and Parkinson's shortly.
This Morris Minor looks great. But like a stem cell, it's trying to change into something else.
Transplantation of fetal brain cells also seems to have helped patients with Huntington's disease, a progressive and fatal brain illness that causes uncoordination and psychosis. In a pilot study in Florida, four of seven patients had improvements in movement, although the disease normally gets steadily worse. The implanted cells were alive and connected to other neurons in a patient who died for unrelated reasons, more than one year after the transplant.
While there is no proof that the transplants caused the improvement, it's a reasonable conclusion. And, says Ole Isacson, of Harvard Medical School, "such long survival is good news not just for fetal-cell transplantation but for using stem cells."
What are the pitfalls and potentials of these remarkable cells, in terms of treating the ills that ail us?
are 1 2 3 4
pages in this feature.
Bibliography | Credits | Feedback | Search