The news media are ignoring a major medical revolution. Doctors and scientists have been making major strides in the fields of tissue engineering and regenerative medicine in the last decade. Journalists write news stories about embryonic stem cells which only promise to be useful sometime in the distant future and ignore the fact that doctors have been using adult stem cells to grow bones and treat various disorders for years.
Harvard University’s Dr. Joseph P. Vacanti and his brother Dr. Charles A. Vacanti have been among the leaders in this field. Joseph Vacanti began working on the idea in the seventies, but didn’t isolate human adult stem cells until1992..
Most cells can only reproduce a limited number of times. Small sections of DNA at the ends of chromosomes called telomeres become shorter with each division. The loss of these telomeres prevents further division. Stem cells don’t have this problem.
Specialized cells normally only produce daughter cells like themselves. Stem cells are flexible and can often produce a variety of different cell types.
By 1994 the Vacantis were ready to work with Dr. Joseph Upton and Dr. Dennis P. Lund at Boston Children’s Hospital to grow a chest for 12-year-old Sean G. McCormack of Norwood, Mass. McCormack was born with Poland’s Syndrome and had no cartilage or bone under the skin on the left side of his chest. McCormack was an active boy and wanted to play baseball even though his condition made such activity risky.
The doctors scraped away protruding cartilage
from McCormack and used the cells to seed a biogradable scaffold composed
of artificial polymer that was molded to the shape of his torso. Dr. Yilin
Cao assisted by adding growth factors to the cells before “cooking”
them in a bioreactor for several weeks. After receiving special approval
from the Food & Drug Administration, the doctors implanted the engineered
cartilage into McCormack.
Charles Vacanti has also grown thumbs and
ear lobes.
Recently German doctors grew a
new jaw bone for a 56-year-old German man whose lower jaw and half
his tongue were cut out a decade ago because of mouth cancer.
Doctors couldn’t use the normal approach
of taking a piece of bone from some other location because the man was
taking blood thinner for another medical condition. Artificial jaws would
have posed too great a risk of infection.
Dr. Patrick Warnke and his team began by
creating a virtual jaw on a computer based on a 3-dimensional scan of the
patient’s mouth. They next created a thin titanium micro-mesh cage. Sugar
lump sized bone mineral blocks were placed in the cage along with human
growth factor for building bone and blood extracted from the man’s bone
marrow.
The surgeons implanted the cage into the
muscle below the man’s right shoulder blade and left it there for a few
months. They then removed it along with some surrounding muscle and blood
vessels and implanted it in the man’s mouth with connections to blood
vessels in the patient’s neck.
Plastic scaffolds can also be used to grow
new cells in the patient’s body. In early 1998 a surgeon repaired a large
hernia I had by placing a plastic scaffold across the gap. My stem cells
then generated new muscle cells along that scaffold.
Charles Vacanti wasn’t the first to grow
new human tissue for patients. During World War I Dr. Harold Delf Gillies
used tissue from other parts of the body to repair war injuries. He developed
the tubed
pedicle graft to facilitate new tissue growth. This procedure involved
maintaining blood vessel connections to the new tissue until new blood
vessels developed.
This procedure was particularly useful
for growing new skin cells. Human skin cells are constantly replaced with
new cells working their way up to the surface as old skin cells die and
fall off. The use of the tubed pedicul graft technique allowed growth of
new skin cells in areas where skin was still healthy to be transplanted
to areas where it had been destroyed. I can recall seeing new skin growing
as a kind of tube on my grandfather’s neck back in the 50's. The skin
was then used to replace facial skin that had been destroyed by skin cancer.
Skin grafts themselves aren’t a recent
invention. Hindu accounts report the use of skin
grafts as early as 3000 B.C.
Today various forms of “artificial skin”
are available with some using human tissue such as the product called Apligraf
that uses the foreskin taken from infants to produce a type of “skin”
that can be used for burn victims.
Cornea transplants are the most common
transplants from one person to another. Over 700,000 people have received
cornea
transplants since 1961.
The first was attempted by Richard Kissam
in 1838, but the cornea soon became opaque. Various other attempts also
failed until Conrad
Zirm succeeded in 1905.
As with other transplant surgery the number
of people who need corneas exceeds the supply of corneas available for
transplant the June 2, 1999, issue of the New England Journal of Medicine
reported on a Japanese study that supplemented cornea transplants with
adult stem cells. Today, doctors are using adult stem cells to grow new
corneas for transplant.
Cancer treatment is one of the biggest
uses of stem cells. Curing some forms of cancer requires using radiation
to kill the blood producing stem cells in the bone marrow. Bone marrow
transplants(adult stem cells) are then used to replace the destroyed cells.
Similar procedures are being investigated for autoimmune disorders.
For example, Methodist Hospital in Houston,
Texas, and other locations have tested this treatment for Multiple Sclerosis.
Other variations have involved reeducating the patient’s immune system
cells in experimental treatment for
Lupus. Stem cells are removed from the patient before zapping the immune
system. The reeducated cells are then injected back into the patient.
Immune suppression combined with partial
pancreas transplants has been used successfully in experimental treatment
of diabetes. In this procedure a donor pancreas was divided among multiple
recipients whose immune systems had been treated.
Gene replacement therapy is being combined
with stem cell treatments for Muscular Dystrophy.
Scientists once thought bone marrow stem
cells were only useful for producing blood cells. However, scientists now
know that bone marrow cells can be used to produce brain cells that could
be transplanted into the brain as well as providing new liver cells.
It has been known for some time that the
liver can regenerate. This capacity allows partial liver transplants in
which the new liver then expands, including partial livers provided by
living donors.
The development of new corneas and bones
demonstrate one of the types of treatments the Vacantis believe adult stem
cells can be used for. Doctors in the field of regenerative medicine believe
they extend such procedures to grow new internal organs such as kidneys
and the pancreas.
Other treatments involve repairing existing
body parts in place. Doctors have begun injecting a patient’s own stem
cells into the
heart where they begin replacing damaged tissues.
Other doctors are looking for the proteins
that signal for replacement cells such as the gene that codes for stromal
cell-derived factor-1(SDF-1).
These doctors believe that they may be
able to get the body to repair itself by injecting this protein into a
damaged heart, for example, they can trigger heart repairs. This particular
gene is also of interest to diabetes researchers who have found that many
Americans who have Type 1 Diabetes have a defective copy of this gene.
However, this defect hasn’t found in
Japanese with Type 1 Diabetes. Conceivably a defective copy of a gene that
normally signals for repairs could trigger the body’s immune system to
destroy cells.
Spinal cord injuries are also being treated
with adult stem cells. Laura
Dominguez of San Antonio, Texas, and others have benefitted from the
treatment provided by Dr. Carlos Lima at the Egas Moniz Hospital, in Lisbon,
Portugal. Lima harvests stem cells from the patient’s nose and inserts
them into the sites of spinal cord breaks.
Doctors have discovered how to repair damaged
lung
cells using adult stem cells. Dentists are working on a way to use
adult stem cells to grow new
teeth at the appropriate location in a patient’s mouth.
A medical revolution is occurring using
adult stem cells to repair or completely replace damaged tissues. Unfortunately,
some researchers want to slow this revolution by diverting the inadequate
amount of research funds to development of embryonic stem cells. They claim
that embryonic cells are needed because they believe adult stem cells cannot
be used to produce all the various cell types.
This belief persists in spite of the fact
that all the major cell types(skin, muscle, nerve(glial and neuron), blood
and bone) can already be produced from adult stem cells as can more specialized
cells such as pancreas, kidney, cornea and lung. Moreover many of these
cells are already being used to treat patients as the above discussion
indicates.
Duke University researchers have even discovered
that a significant portion of the adipose fat cells most of us have too
many of can be converted into nerve
and other cells. The ability of fat cells to function as stem cells
may explain why obese people have more trouble with heart and other problems.
The use of their stem cells to store fat may prevent them from producing
cells to replace damaged cells in the heart or other areas.
Dr. Steven Goldman has led a team of researchers
at the University of Rochester Medical Center to turn ordinary cells into
stem cells by introducing a telomerase
gene. The presence of this gene allows the cells to reproduce indefinitely
because the telomerase gene replaces the telomeres that normally become
shorter as cells divide.
The FDA has recently approved human trials
by Massachusetts General Hospital of an adult stem cell therapy that has
reversed Type
I(Juvenile) diabetes in mice. A team led by Harvard’s Dr. Denise
Faustman has successfully(92% success rate) used adult spleen cells to
retrain the immune systems of diabetic mice to stop the immune system attacks
on insulin-producing pancreas cells.
Lee Iacocca’s foundation has donated
$1 million of the possible $11 million that will be needed for the trial.
Unfortunately some major foundations like the Juvenile
Diabetes Foundation are using money to support embryonic research instead.
The claim by embryonic researchers that
all research should be financed ignores the fact that research funds are
very limited. Why spend money on embryonic research that may never be useful
in humans instead of adult stem cell research that is already producing
results?
Adult stem cells are successfully treating
people now for spinal cord injuries and Parkinson’s. Why spend money
on embryonic research when researchers are still having trouble managing
embryonic cells? Some embryonic cells have produced tumors. The March 25,
2004, issue of the New
England Journal of Medicine contained an article indicating that some
embryonic cells are producing cells with extra chromosomes.
Why should patients have to wait for embryonic
researchers to duplicate the work of adult stem cell researchers before
receiving treatments? Testing new treatments can take several years and
embryonic research isn’t even ready to consider clinical trials. Some
treatments with adult stem cells, particularly for cancer, are already
available to the general public. Additional treatments will be available
within a few years if they work. Embryonic treatments cannot realistically
be expected to be available for at least 5 to 10 years if not longer.
So, why should people have to wait? Why
not provide full funding to adult stem cell therapies now instead of splitting
money with embryonic research that may never produce results?
In the early days of micro computers some programmers would distribute
their programs as shareware. People could try the program out before
deciding whether to send money to the progammer. This same procedure
can be used by writers on the Internet. Readers can decide after
reading something whether it is worth paying for and how much to pay for
it. One way to do so is through PayPal.
Email: reasonmclucus@netscape.net
Spontaneous
generation of insulin producing cells has been observed in mice whose
immune systems were suppressed.
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