What Are Stem Cells?
Stem cells are special human cells that have the ability to develop into many different
cell types, from muscle cells to brain cells. In some cases, they also have the ability
to repair damaged tissues. Researchers believe that stem cell-based therapies may
one day be used to treat devastating ailments like paralysis and Alzheimer disease.
Types of stem cells
Stem cells are divided into two main forms. They are embryonic stem cells and adult
stem cells. The embryonic stem cells used in research today come from unused embryos.
These result from an in vitro fertilization procedure and that are donated to science. These embryonic stem cells
are pluripotent. This means that they can turn into more than one type of cell.
There are two types of adult stem cells. One type comes from fully developed tissues,
like the brain, skin, and bone marrow. There are only small numbers of stem cells
in these tissues. They are more likely to generate only certain types of cells. For
example, a stem cell derived from the liver will only generate more liver cells.
The second type is induced pluripotent stem cells. These are adult stem cells that
have been manipulated in a lab to take on the pluripotent characteristics of embryonic
stem cells. Scientists first reported that human stem cells could be reprogrammed
this way in 2006. Although induced pluripotent stem cells don't appear to be clinically
different from embryonic stem cells, scientists have not yet found one that can develop
every kind of cell and tissue.
Stem cells in medicine
The only stem cells currently used to treat disease are hematopoietic stem cells.
These are the blood cell-forming adult stem cells found in bone marrow. Every type
of blood cell in the bone marrow begins as a stem cell. Stem cells are immature cells
that are able to make other blood cells that mature and function as needed.
These cells are used in procedures like bone marrow transplants. These help cancer
patients make new blood cells after their own hematopoietic stem cells have been killed
by radiation therapy and chemotherapy. They may also be used to treat people with
conditions like Fanconi anemia. This is a blood disorder that causes the body's bone
marrow to fail.
Stem cells may benefit our health in the future in many ways and through many new
therapies. Researchers believe that stem cells will eventually be used to help regenerate
damaged tissue. One day, for example, healthcare providers may be able to treat people
with chronic heart disease. They can do this by growing healthy heart muscle cells
in a lab and transplanting them into damaged hearts. Other therapies could target
illnesses as diverse as type 1 diabetes, spinal cord injuries, Alzheimer disease,
and rheumatoid arthritis. New medicines could also be tested on cells generated from
pluripotent stem cells.
Challenges in stem cell research
Stem cells need much more study before their use can be expanded. Scientists must
first learn more about how embryonic stem cells develop so that they can understand
how to control the type of cells created from them. Another challenge is that the
embryonic stem cells available today have a high likelihood of being rejected by the
body. Finally, some people find it morally troubling to use stem cells derived from
Scientists also face challenges with the use of adult pluripotent stem cells. These
cells are difficult to grow in a lab, so researchers are investigating ways to improve
the process. These cells are also found in relatively tiny quantities in the body.
There is a greater chance that they could contain DNA abnormalities.
A number of clinical trials that use stem cell therapies are currently being conducted
in the U.S. If you are interested in trying this therapy to treat a specific condition,
ask your healthcare provider how to find out about trials available in your area.