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Adult Stem Cells
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As noted earlier, multipotent stem cells can be found in some types of
adult tissue.

In fact, stem cells are needed to replenish the supply cells in our body
that normally wear out.

An example, which was mentioned previously, is the blood stem cell.

Multipotent stem cells have not been found for all types of adult tissue,
but discoveries in this area of research are increasing.

For example, until recently, it was thought that stem cells were not
present in the adult nervous system, but, in recent years, neuronal stem
cells have been isolated from the rat and mouse nervous systems.

The experience in humans is more limited.

In humans, neuronal stem cells have been isolated from fetal tissue and a
kind of cell that may be a neuronal stem cell has been isolated from adult
brain tissue that was surgically removed for the treatment of epilepsy.

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Do adult stem cells have the same potential as pluripotent stem cells?
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Until recently, there was little evidence in mammals that multipotent cells
such as blood stem cells could change course and produce skin cells, liver
cells or any cell other than a blood stem cell or a specific type of blood
cell; however, research in animals is leading scientists to question this
view.

In animals, it has been shown that some adult stem cells previously thought
to be committed to the development of one line of specialized cells are
able to develop into other types of specialized cells.

For example, recent experiments in mice suggest that when neural stem cells
were placed into the bone marrow, they appeared to produce a variety of
blood cell types.

In addition, studies with rats have indicated that stem cells found in the
bone marrow were able to produce liver cells.

These exciting findings suggest that even after a stem cell has begun to
specialize, the stem cell may, under certain conditions, be more flexible
than first thought.

At this time, demonstration of the flexibility of adult stem cells has been
only observed in animals and limited to a few tissue types.

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Why not just pursue research with adult stem cells?
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Research on human adult stem cells suggests that these multipotent cells
have great potential for use in both research and in the development of
cell therapies.

For example, there would be many advantages to using adult stem cells for
transplantation.

If we could isolate the adult stem cells from a patient, coax them to
divide and direct their specialization and then transplant them back into
the patient, it is unlikely that such cells would be rejected.

The use of adult stem cells for such cell therapies would certainly reduce
or even avoid the practice of using stem cells that were derived from human
embryos or human fetal tissue, sources that trouble many people on ethical
grounds.

While adult stem cells hold real promise, there are some significant
limitations to what we may or may not be able to accomplish with them.

First of all, stem cells from adults have not been isolated for all tissues
of the body.

Although many different kinds of multipotent stem cells have been
identified, adult stem cells for all cell and tissue types have not yet
been found in the adult human.

For example, we have not located adult cardiac stem cells or adult
pancreatic islet stem cells in humans.

Secondly, adult stem cells are often present in only minute quantities, are
difficult to isolate and purify, and their numbers may decrease with age.

For example, brain cells from adults that may be neuronal stem cells have
only been obtained by removing a portion of the brain of epileptics, not a
trivial procedure.

Any attempt to use stem cells from a patient's own body for treatment would
require that stem cells would first have to be isolated from the patient
and then grown in culture in sufficient numbers to obtain adequate
quantities for treatment.

For some acute disorders, there may not be enough time to grow enough cells
to use for treatment.

In other disorders, caused by a genetic defect, the genetic error would
likely be present in the patient's stem cells.

Cells from such a patient may not be appropriate for transplantation.

There is evidence that stem cells from adults may have not have the same
capacity to proliferate as younger cells do.

In addition, adult stem cells may contain more DNA abnormalities, caused by
exposure to daily living, including sunlight, toxins, and by expected
errors made in DNA replication during the course of a lifetime.

These potential weaknesses could limit the usefulness of adult stem cells.

Research on the early stages of cell specialization may not be possible
with adult stem cells since they appear to be farther along the
specialization pathway than pluripotent stem cells.

In addition, one adult stem cell line may be able to form several, perhaps
3 or 4, tissue types, but there is no clear evidence that stem cells from
adults, human or animal, are pluripotent.

In fact, there is no evidence that adult stem cells have the broad
potential characteristic of pluripotent stem cells.

In order to determine the very best source of many of the specialized cells
and tissues of the body for new treatments and even cures, it will be
vitally important to study the developmental potential of adult stem cells
and compare it to that of pluripotent stem cells.

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Summary
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Given the enormous promise of stem cells to the development of new
therapies for the most devastating diseases, it is important to
simultaneously pursue all lines of research.

Science and scientists need to search for the very best sources of these
cells.

When they are identified, regardless of their sources, researchers will use
them to pursue the development of new cell therapies.

The development of stem cell lines, both pluripotent and multipotent, that
may produce many tissues of the human body is an important scientific
breakthrough.

It is not too unrealistic to say that this research has the potential to
revolutionize the practice of medicine and improve the quality and length
of life.

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janet paterson
53 now / 44 dx cd / 43 onset cd / 41 dx pd / 37 onset pd
TEL: 613 256 8340 URL: http://www.geocities.com/janet313/
EMAIL: [log in to unmask] SMAIL: PO Box 171 Almonte Ontario K0A 1A0 Canada