What are stem cells and what are they used for?

Stem cells are unprogrammed cells in the human body that can be described as "shape shifters." These cells have the ability to change into other types of cells. Stem cells are at the center of a new field of science called regenerative medicine. Because stem cells can become bone, muscle, cartilage and other specialized types of cells, they have the potential to treat many diseases, including Parkinson's, Alzheimer's, diabetes and cancer. Eventually, they may also be used to regenerate organs, reducing the need for organ transplants and related surgeries.

"Stem cells are like little kids who, when they grow up, can enter a variety of professions," Dr. Marc Hedrick of the UCLA School of Medicine says. "A child might become a fireman, a doctor or a plumber, depending on the influences in their life -- or environment. In the same way, these stem cells can become many tissues by making certain changes in their environment."

Stem cells can typically be broken into four types:

Embryonic and fetal stem cells have the potential to morph into a greater variety of cells than adult stem cells do.

In April 2001, researchers at UCLA and the University of Pittsburgh found stem cells in fat sucked out of liposuction patients. Previously, stem cells were found only in bone marrow, brain tissue and fetal tissue -- sources that have caused both logistical and ethical problems. Stem cells from fat have the ability to mature into other types of specific cells, including muscle, bone and cartilage, but how many other types is still unknown.

Prior to being transplanted into a person's tissue to begin regeneration of that tissue, stem cells have to go through differentiation. Differentiation is the process by which scientists pre-specialize the stem cells, almost like preprogramming the stem cells to become specific cells. These cells are then injected into the area of the body being targeted for tissue regeneration. When stem cells come into contact with growth chemicals in the body, the chemicals program the stem cells to grow into the tissue surrounding it.

Stem cells are already being used to treat leukemia and some joint repairs. For example, a bone-marrow transplant is accomplished by injecting stem cells from a donor into the bloodstream of the patient. Stem cells from bone marrow also have the ability to repair the liver. Researchers are studying stem cells to find out if they could correct brain damage resulting from Parkinson's disease.

The next step will be to learn what influences stem cells to change into particular types of cells. Once that's known, it will be possible to grow cells that perfectly match those of the patients.

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