Divide and Conquer? A look at Stem Cell Research
Stem cells could be the beginning of the end for deadly
diseases, by allowing medical science to form custom-made
tissues and organs that would replace or repair damaged ones.
Scientists haven't yet mastered the process of creating
specialized cells that form body parts. But they have come a
long way since the 1800s when pathologist Rudolf Virchow
pioneered the idea that disease starts at the cellular level in
his Berlin laboratory.
Embryonic stem cell research got its start in the U.S. in
November 1998 when James Thomson, a scientist at the University
of Wisconsin in Madison, was the first to successfully remove
cells from spare embryos at fertility clinics. He established
the world's first human embryonic stem cell line. His
announcement however, set off a firestorm of controversy that
was quickly carried into countries around the world.
At the center of the controversy was a wave of political and
religious fervor, with zealots who likened the research to
cannibalism, and warned of a dark, science fiction-like future
filled with "embryo farms" and "cloning mills"
In truth, every year thousands of unwanted embryos are slated
for disposal at fertility clinics around the country. These
embryos are smaller than the dot above the letter "i" when typed
onto a piece of paper.
They have no identifying features, and not even a hint of a
nervous system.
To throw them away, advocates say, when the stem cells
themselves would be unable to develop into a baby - even if
planted inside a uterus - seems an unthinkable waste that they
claim borders on immoral.
Some forms of stem cell therapy have been around - and widely
used - for decades. For example, bone marrow transplants are
used to treat sickle cell anemia. The stem cells in the donated
bone marrow regenerate the patient's blood and immune system.
It works like this - one cell divides, and becomes two. The two
become four. And so on and so on, until they multiply into a
ball of millions of cells. Similar cells combine into tissues,
and the tissues combine into organs. There are over 200
different types of cells that create the human body. And inside
each of us are billions of cells, each with a specific job to do.
A stem cell is a cell that matures and has the ability to
self-replicate - often throughout the life of the organism. So,
the dream for medical researchers is to provide the right
conditions - or give specific stems cells the right signals - so
that a targeted stem cell will develop into mature cells that
could repair diseased tissues or organs. If successful, it would
mean the end of crude mechanical devices such as insulin pumps,
titanium joints or plastic arteries, and use living, natural
replacements.
The potential for stem cell medicine is awe inspiring. Stem cell
lines could be used to help burn victims, and those who have
suffered spinal cord injuries. It also has the potential to cure
many common diseases of today, such as diabetes, heart disease
and some types of cancer.
Even in the midst of all the controversy, few question the
medical promise of embryonic stem cells.
And while the arguments go back and forth, policymakers and
governments aren't waiting for medical answers.
Their reactions - and actions - that have included limiting
government funding and the type of research that is allowed are
varied.
Germany for example has banned some types of stem cell research.
Under President George W. Bush, the U.S. has imposed stern
limits on the government funding, but left private funding wide
open.
This has meant that the U.K., China, Korea and Singapore are
competing with one another to become the epicenter of stem cell
research. In addition to providing funding, they've set up
ethical oversights to encourage and support research in the
field, within carefully drawn guidelines.
Despite the varied political climates, scientists too are
working furiously to see which techniques will produce viable
treatments the fastest.
In the United Kingdom, scientists are allowed to extract stem
cells from embryos left over from in-vitro fertilizations, and
to clone embryos specifically for study.
With an eye on the future, the U.K. has built the world's first
Stem Cell bank. It is a repository where stem cell lines are
kept in cold storage. Researchers can deposit and withdraw both
adult and embryonic stem cells. They apply the same rigorous
standards to all cells, and scientists hope that eventually they
will be able to create batches of stem cells that are as uniform
as the drugs created by pharmaceutical companies.
What are embryonic stem cells?
Most embryonic stem cells used in research come from embryos
created in in-vitro fertilization.
Each embryo's inner cell mass has 40 or so stem cells. The mass
is transferred to a culture dish lined with feeder cells. As the
cells divide and multiply, they are re-planted into fresh
culture dishes. If, after many months, the original stem cells
have grown into millions of healthy cells without maturing and
differentiating into specialized cells, they are referred to as
a "stem cell line" and are capable of reproducing indefinitely.
Embryonic stem cells can develop into any type of cell through a
process called pluripotency. The challenge for scientists is to
keep the harvested cells from maturing and then at the proper
time, give them the right signals so that the cells
differentiate into the needed tissue. We have not yet figured
out nature's secret - how to tell one stem cell to form blood,
another a specific organ and yet another skin.
Scientists know that complex combinations of growth factors,
genetic and chemical signals drive the process, but they're a
long way from making the leap to being able to perfect or order
the process.
What are adult stem cells?
The adult body has a limited number of stem cells in many
tissues and organs that are dormant until activated by illness
or injury. Adult stem cells aren't as functional or a
multi-talented as embryonic stem cells however. They can't morph
into any kind of cell and may be limited to becoming only the
cell types of their original tissue. (So while an adult stem
cell in brain can become a neuron or a glial cell (both are
neural cells), present research hasn't provided us with the
formula for ordering to change into a liver or bone cell.
Adult stem cells have been found in the brain, the blood, the
cornea, the retina, the heart, in fat, skin, dental pulp, bone
marrow, blood vessels and skeletal muscle and in the intestines.
Generally adult stem cells have two main drawbacks for
researchers. They are scarcer in the body and harder to culture
than embryonic cells. Since large numbers of them are needed, it
makes their viability for wide spread use somewhat questionable.
How many stem cell lines exist today?
Right now, the U.S. still leads the world in the number of
embryonic stem cell lines, even with the restrictions on funding
imposed by President Bush, which prohibit government funding for
any embryonic stem cell lines created after August 9, 2001. But
the U.K. and Asian countries - most particularly South Korea and
Singapore, are working hard to become the new world leaders and
are aggressively providing the facilities, funding and
oversights into therapies and are beginning to attract some of
the brightest scientific minds.
There are a total of 155 embryonic stem cell lines in the world
today. 78 of them are approved for U.S. federal funding, and of
those, 22 are approved for U.S. funding and suitable for
research. Sweden has 33, South Korea has 24, India has 10,
Singapore has 7, Israel has 5, the U.K. has 3, Spain has 2 and
Iran has 1.
What progress has been made?
So far however, only adult stem cells have been tested on
humans, although research on both adult and embryonic stem cells
continues at a fast pace. Some of the results to date show
promise in being able to treat heart disease, leukemia and other
cancers, rheumatoid arthritis, Parkinson's Disease, and Type I
diabetes.
Preliminary results however are exciting, and this century could
mark the beginning of a revolutionary transformation in the
practice of medicine, as we know it.