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Why are doctors and scientists so excited about human
embryonic stem cells? Stem cells have potential in many
different areas of health and medical research. To start with,
studying stem cells will help us to understand how they transform
into the dazzling array of specialized cells that make us what we
are. Some of the most serious medical conditions, such as cancer and
birth defects, are due to problems that occur somewhere in this
process. A better understanding of normal cell development will
allow us to understand and perhaps correct the errors that cause
these medical conditions.
Another potential application of stem cells is making cells and
tissues for medical therapies. Today, donated organs and tissues are
often used to replace those that are diseased or destroyed.
Unfortunately, the number of people needing a transplant far exceeds
the number of organs available for transplantation. Pluripotent stem
cells offer the possibility of a renewable source of replacement
cells and tissues to treat a myriad of diseases, conditions and
disabilities, including Parkinson's and Alzheimer's diseases, spinal
cord injury, stroke, burns, heart disease, diabetes, osteoarthritis,
and rheumatoid arthritis.
Have human embryonic stem cells been used successfully to treat
any human diseases yet?
Scientists have been able to do experiments with human embryonic
stem cells just since 1998, when a group led by Dr. James Thomson at
the University of Wisconsin developed a technique to isolate and
grow the cells. Moreover, federal funds to support research with
human embryonic stem cells have been available only since Aug. 9,
2001, when President Bush announced his decision on federal funding
for this research. Because many academic researchers rely on federal
funds to support their laboratories, they are just beginning to
learn how to grow and use the cells. Thus, although human embryonic
stem cells are thought to offer potential cures and therapies for
many devastating diseases, research using them is still in its early
stages.
Adult stem cells, such as blood-forming stem cells
called hematopoietic stem cells
in bone marrow, are currently the only type of stem cell commonly
used to treat human diseases. Doctors have been transferring these
cells in bone marrow transplants for over 40 years. More advanced
techniques of collecting, or "harvesting," these cells are now used
in order to treat leukemia, lymphoma and several inherited blood
disorders.
The clinical potential of adult stem cells has also been
demonstrated in the treatment of other human diseases, including
diabetes and advanced kidney cancer. However, these newer uses have
involved studies with a very limited number of patients.
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 What will be the best type of stem cell to use for therapy?
Pluripotent stem cells, while having great therapeutic potential,
face formidable technical challenges. First, scientists must learn
how to control their development into all the different types of
cells in the body. Second, the cells now available for research are
likely to be rejected by a patient's immune system. Another serious
consideration is that the idea of using stem cells from human
embryos or human fetal tissue troubles many people on ethical
grounds.
Until recently, there was little evidence that multipotent adult
stem cells could change course and provide the flexibility that
researchers need in order to address all the medical diseases and
disorders they would like to. New findings in animals, however,
suggest that even after a stem cell has begun to specialize, it may
be more flexible than previously thought.
There are currently several limitations to using adult stem
cells. Although many different kinds of multipotent stem cells have
been identified, adult stem cells that could give rise to all cell
and tissue types have not yet been found. Adult stem cells are often
present in only minute quantities and can therefore be difficult to
isolate and purify. There is also evidence that they may not have
the same capacity to multiply as embryonic stem cells do. Finally,
adult stem cells may contain more DNA abnormalities -- caused by
sunlight, toxins and errors in making more DNA copies during the
course of a lifetime. These potential weaknesses might limit the
usefulness of adult stem cells.
I have Parkinson’s Disease. Is there a clinical trial I can
participate in that uses stem cells as therapy?
The public may search a database of National Institutes of
Health-sponsored clinical trials at
http://www.clinicaltrials.gov. Enter the search terms of
interest (in this case,
"Parkinson's disease and stem cells")
to search for applicable clinical trials.
Where can I donate umbilical cord stem cells?
The National Institutes of Health cannot accept donated umbilical
cord stem cells from the general public. The National Marrow Donor
Program maintains a Web page on donating cord blood, at
http://www.marrow.org/NMDP/
cord_blood_bank_list.html, and the International Cord Blood
Society has one at
http://www.cordblood.org/public/insights.
[National
Institutes of Health] |
