Replacing Cells - Biotechnology and Your Health: Pharmaceutical Applications - page 116

child no longer had to wear the helmet she had worn for the
previous year since her fall. At three months, scans of her skull
showed bone formation where the defect had been. This was quite
an amazing procedure, but there is no way to be sure that the
addition of stem cells made a difference in the result. New methods
will have to be developed to track the stem cells to see if they became
part of the final graft. Early efforts like these provide hope that it
may be possible to incorporate the use of stem cells into complex
medical procedures, but like bone marrow transplants in their
early days, it will take many years and controlled clinical trials to
have full confidence in the role of adult stem cells.
In a general way, the question about the versatility of adult stem
cells comes down to whether the library of genetic instructions is
irreversibly changed as cells specialize, and whether some parts then
become unusable. This is a fundamental question that scientists
have been studying for many years, and the answers are not yet
certain. It is also a practical question, since if stem cells from one or
more adult tissue are pluripotent, then such cells might be taken
from an individual and used to repair and replace any, or at least
many, of his or her tissues that are not working correctly.
POSSIBILITIES OF STEM CELL THERAPY
Excitement about ES-derived cells has been fueled by several
reports of laboratory and animal studies. In Parkinson's disease ,
symptoms result from a loss of cells that produce a critical signal
molecule. Cells that produce the signal were created in the lab
from mouse ES cells. When injected into the brain, they reduced
symptoms in mice with a form of Parkinson's disease. Strains of
rats and mice have been developed or discovered that are unable
to produce myelin, the fatty insulation that normally covers the
nerve fibers of the brain and spinal cord. Injection of insulation-
producing cells generated from mouse ES cells produced myelin on
the nerve fibers of these animals.