Researchers have had some success with stimu-
lating blood stem cells, in the laboratory, to func-
tion as though they were other types of cells such
as NERVEcells or MUSCLEcells, and are hopeful that
stem cells will someday become a source of culti-
vated replacement tissues and organs. Multipotent
stem cells that occur in other tissues are difficult
to identify and extract from their source tissues
though may also hold similar potential.
For further discussion of stem cells within the
context of the structures and functions of genetics,
please see the overview section “Genetics and
Molecular Medicine.”
See also ETHICAL ISSUES IN GENETICS AND MOLECU-
LAR MEDICINE; GAMETE; HEMATOPOIESIS; STEM CELL
THERAPY.
stem cell therapy Implantation of STEM CELLSto
become specialized cells for tissue and organ repair
or replacement. Though most STEM CELLtherapy
applications remain experimental, BONE MARROW
TRANSPLANTATION(also called BLOODstem cell trans-
plantation) has become a standard of treatment
for many cancers affecting the blood and the lym-
phatic system (leukemias and lymphomas) as well
as certain other cancers. Researchers have also
been successful in cultivating stem cells into SKIN
for skin grafting, to treat severe BURNS, and into
pancreatic islet cells that produce INSULIN, to treat
severe type 1 DIABETES. Though these applications
of stem cell therapy remain experimental, they
raise the potential for stem cell therapy to become
viable in treating numerous health conditions.
Two significant concerns with stem cell therapy
are the potential for cancer to develop and the
rejection of the cultivated cells or tissue. A prime
value of the stem cell is its unlimited ability to
divide. However, a function called APOPTOSISlimits
most division of the cells in the body. It appears
that cells can divide only a certain number of
times, then begin to shut down. The exceptions
are stem cells and cancer cells, and researchers are
not certain what will keep stem cells from becom-
ing cancer cells. Apoptosis remains a focus of
much research. And as is the case with organs
donated for transplantation, the body can reject
stem cell transplantations. When this occurs the
body’s IMMUNE SYSTEM attacks the transplanted
stem cells, killing them.
See also BLOOD STEM CELLS; CELL STRUCTURE AND
FUNCTION; GENE THERAPY; ISLETS OF LANGERHANS;
LEUKEMIA; MOLECULARLY TARGETED THERAPY.stem cell therapy 141