Stem cells are unspecialized cells that have two important
characteristics that distinguish them from other cells in the body.
First, they can replenish their numbers for long periods through cell
division. Second, after receiving certain chemical signals, they can
differentiate, or transform into specialized cells with specific
functions, such as a heart cell or nerve cell.
Stem cells can be classified by the extent to which they can differentiate into different cell types:
Totipotent stem cells can differentiate
into any cell type in the body plus the placenta, which nourishes the
embryo. A fertilized egg is a type of Totipotent stem cell. Cells
produced in the first few divisions of the fertilized egg are also
Totipotent.
Pluripotent stem cells are
descendants of the Totipotent stem cells of the embryo. These cells,
which develop about four days after fertilization, can differentiate
into any cell type, except for Totipotent stem cells and the cells of
the placenta.
Multipotent stem cells are
descendants of Pluripotent stem cells and antecedents of specialized
cells in particular tissues. For example, hematopoietic stem cells,
which are found primarily in the bone marrow, give rise to all of the
cells found in the blood, including red blood cells, white blood cells,
and platelets. Another example is neural stem cells, which can
differentiate into nerve cells and neural support cells called Glia.
Progenitor
cells (or Unipotent stem cells) can produce only one cell type. For
example, Erythroid Progenitor cells differentiate into only red blood
cells. At the end of the long chain of cell divisions are "terminally
differentiated" cells, such as a liver cell or lung cell, which are
permanently committed to specific functions. These cells stay committed
to their functions for the life of the organism or until a tumor
develops. In the case of a tumor, the cells differentiate, or return to
a less mature state. Research is now being conducted on both adult and
embryonic stem cells to determine the characteristics and potential of
both to cure disease.
What do the terms Totipotent, Pluripotent and Multipotent mean?
"Stem cells" is a term used to describe all cells that can give rise to
cells of multiple tissue types. However, there are different types of
stems cells. Totipotent cells, like the cells of a fertilized egg in
the first few days after fertilization, can give rise to a fully
functional organism. During normal development, the Totipotent cells
become more specialized and are considered Pluripotent, meaning that
they can give rise to every cell type in the body, but will not give
rise to the placenta or supporting tissues necessary for fetal
development. Because their potential is not total, they are not
Totipotent and they are not embryos. Pluripotent stem cells undergo
further specialization into stem cells committed to giving rise to
cells that are specialized for a particular function. Multipotent cells
can give rise to the cell types found in the tissue from which they
were derived, such as blood stem cells that give rise only to red blood
cells, white blood cells and platelets, or skin stem cells that give
rise only to the various types of skin cells.
Cell therapy can be defined as a group of new techniques, or
technologies, that rely on replacing diseased or dysfunctional cells
with healthy, functioning ones. These new techniques are being applied
to a wide range of human diseases, including many types of cancer,
neurological diseases such as Parkinson's and Lou Gehrig's disease,
spinal cord injuries, and diabetes. Replacing dead cells in the retina
with new ones may someday cure even presently incurable eye diseases
such as glaucoma and macular degeneration. To understand how cell
therapy works, it helps to understand the role of cells in the body.
Cells are the basic building blocks of the human body. These tiny
structures compose the skin, muscles, bones and all of the internal
organs. They also hold many of the keys to how our bodies function.
Cells serve both a structural and a functional role in the body,
performing an almost endless variety of actions to sustain the body's
tissues and organs.
There are hundreds, perhaps thousands, of different specialized cell
types in the adult body. All of these cells perform very specific
functions for the tissue or organ they compose. For example,
specialized cells in the heart muscle "beat" rhythmically through the
conduction of electrical signals, while the cells of the pancreas
produce insulin to help the body convert food to energy. These mature
cells have been differentiated, or dedicated, to performing their
special tasks. Conventional wisdom has long maintained that under
normal conditions, once a cell has become specialized, it cannot be
changed into a different type of cell.
Like the body itself, cells have a finite life span; they eventually
die. Most of the body's cells divide and duplicate throughout life, but
some cells either don't replenish themselves or do so in such small
numbers that they cannot replace themselves fast enough to combat
disease.
While cells are indispensable in performing vital functions for the
body, they can also exist outside the body. They can live and divide in
"cultures," special solutions in test tubes or Petrie dishes. This
ability of certain cell types to live isolated from other cells under
controlled conditions has allowed scientists to study them
independently of the organ or system they are normally a part of.
Through the isolation and targeted manipulation of cells, scientists
are finding ways to identify young, regenerating ones that can be used
to replace damaged or dead ones in diseased organs. This therapy is
similar to the process of organ transplant, only the treatment consists
of the transplantation of cells rather than organs. The cells that have
shown by far the most promise of supplying diseased organs with healthy
new ones are called stem cells.
Do adult stem cells have the same capability as embryonic stem
cells? For many years, scientists have conducted studies to determine
whether the stem cells in adult tissue have the same developmental
capability as embryonic stem cells. The general consensus is that adult
stem cells seem to be less versatile. Scientists think that embryonic
stem cells have a much greater utility and potential than the adult
stem cells, because embryonic stem cells may develop into virtually
every type of cell in the human body. Adult stem cells, on the other
hand, may only be able to develop into a limited number of cell types.
Embryonic Stem Cells also continue to divide indefinitely when placed
in culture, while this may not be the case for adult stem cells, which
would reduce their capacity to form new cell types. Both adult and
embryonic stem cell research should continue simultaneously as they are
both critical to our understanding of the etiology, progression and
treatment of disease.
Even though most of the work done in this field has been experimental, most scientists find cell therapy so promising that they believe it is only a matter of time before its use becomes routine. And while many of the hoped-for uses of cell therapy sound futuristic, there are a few forms of this technique that have already been in use for years. Bone marrow transplants are an example of cell therapy in which the stem cells in a donor's marrow are used to replace the blood cells of the victims of leukemia and other cancers. Cell therapy is also being used in experiments to graft new skin cells to treat serious burn victims, and to grow new corneas for the sight-impaired. In all of these uses, the goal is for the healthy cells to become integrated into the body and begin to function like the patient's own cells. Heart
So far, the results of such experiments have exceeded expectations. In a recent advance, pancreatic cells grown from stem cells were implanted into the body of a diabetic and began to produce insulin. Even though cell therapy is a new science, early results like the above have caused great optimism in the scientific community. However, there are several scientific challenges that must be overcome before we can truly harness the power of stem cells.
One of the first challenges that must be overcome for stem cell
therapies to become more commonplace is the difficulty of identifying
stem cells in tissue cultures, which contain numerous types of cells.
While scientists are discovering new cell types almost every day, they
estimate that there could literally be thousands of human cell types.
The process of identifying any desired type of stem cell will involve
painstaking research. Second, once stem cells are identified and
isolated, the right biochemical solution must be developed to cause
these progenitor cells to differentiate into the desired cell type.
This too will require a great deal of experimentation.
Assuming that the above obstacles have been overcome, new issues
arise when the cells are implanted into a person. The cells must be
integrated into the patient's own tissues and organs and "learn" to
function in concert with the body's natural cells. Cardiac cells that
beat in a cell culture, for example, may not beat in rhythm with a
patient's own heart cells. And neurons injected into a damaged brain
must become "wired into" the brain's intricate network of cells and
their connections in order to work properly.
Another challenge is the phenomenon of tissue rejection. Just as in
organ transplants, the body's immune cells will recognize transplanted
cells as "foreign," setting off an immune reaction that could cause the
transplant to fail and possibly endanger the patient. Cell recipients
would have to take drugs to temporarily suppress their immune systems,
which in itself could be dangerous.
Yet another concern is the possible risk of cancer. Cancer results
when cells lose their internal "brakes" and keep dividing when further
proliferation is no longer desirable. Researchers must find a delicate
balance between fostering the growth of new cells to replenish damaged
tissues and making sure that cells don't overgrow and become cancerous.
However, most scientists believe that, with the appropriate research,
these obstacles can be overcome and the power of stem cells can be
harnessed.
There are also ethical, social, financial and political issues
affecting this new industry. One of the hardest issues for this
industry to overcome is that patients are generally offered stem cell
therapy after all other treatments have been exhausted, therefore
limiting the chance for success. One must keep in mind that the success
of stem cell therapy poses a serious threat to many other conventional
treatments. Therefore, there are powerful forces that go out of their
way to minimize this industry's successes and magnify its failures.
Despite the many challenges before us, most scientists believe that
cell therapy will revolutionize medicine. With the use of cell
therapies, we may soon have dramatic cures for cancer, Parkinson's,
diabetes, kidney disease, multiple sclerosis, muscular degeneration and
a host of other diseases. Cell therapies have also shown great promise
in helping to repair catastrophic spinal injuries, and helping victims
of paralysis regain movement. It is even possible that the human life
span could be greatly extended due to the replenishment of tissues in
aging organs. We may even have the ability one day to grow our own
organs for transplantation from our own stem cells, eliminating the
danger of organ rejection. While we will undoubtedly encounter the
limits of cell therapy one day, there is every reason to hope that this
revolutionary new approach will result in radically improved ways to
treat diseases.
The cost of administering 100 to110 million differentiated cells varies, depending on location and condition treated. For further information about cost and treatment packages as well as financing options please contact our office.
Since this procedure has yet to be FDA approved, it is not covered by traditional health insurance policies. Some of our patients have used the services of “Insurance Claims Filing Services” and have been reimbursed for the procedure expenses. We recommend that patients contact them directly for more information.
