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Magic seeds
 Stem cells. They perform miracles in a human embryo. Hundreds of cells that
divide in a mother's womb are slowly transforming into cells that will form various organs
of the human body. Liver cells. Brain cells. Skin, bone and nerve cells. These are the
magic seeds called 'stem cells' that scientists now want to use. To replace an injured
cell, and to heal...
But a lot of controversy surrounds the ongoing scientific research on these. Some say it
is not ethical to tamper with embryos, from where human life springs. But many others feel
that stem cells can prove to be a miracle in science…
The miracle of division
In the beginning, one cell becomes two, and two multiply to four. As they divide further,
they form into a ball of about 200-250 cells - a spherical shape called blastocyst. This
takes place in a human embryo. (See graphic: Cross examination) These cells are
transformed into tissues or cells that make up the human body. Scientists now want to
pluck these raw cells from the young human embryo and make them perform 'special'
functions outside the human body - in a laboratory. Stem cells are unspecialised cells
that are capable of turning into 'specialised' (cells that do a specific function) cells.
The dream is to launch a medical revolution in science, where ailing organs and tissues in
a human being may be repaired. It would mean bringing a dead cell alive through living,
homegrown replacements, instead of mechanical devices. So, a damaged brain cell, which
could take away life, can be replaced by a brain stem cell, restoring all the functions of
the brain. It could heal even the diseases that are now incurable...
Turning cells into medicine
Some children are born with organs that do not work right. A child with juvenile diabetes,
for example, has a pancreas that does not generate enough insulin, to digest sugars.
Adults too have cells or organs that are damaged and do not function (See What do cells
do?).
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What do cells do?
Cells are the building blocks of the human body. They perform a variety of functions to
sustain its tissues and organs. These are the specialised cells that form various organs -
skin, muscles and bones. Pancreatic cells, for instance, release insulin to
convert food to energy.
Like the body, cells have a finite life span; they eventually die. Most cells divide and
duplicate all their life. But some cells are not able to replenish themselves. Or, they do
so in such small numbers that they cannot replace themselves fast enough to combat
diseases. |
Although cells are indispensable for the
human body, they can exist outside it. They can live and divide in "cultures" -
special solutions in test tubes or dishes. This ability of some cells to live under
controlled conditions has inspired scientists to study them as independent organs. They
are looking for ways to identify young, healthy ones that can replace worn out tissues in
diseased organs. Stem cells have this potential.
There are two kinds of stem cells that have been experimented on - embryonic (ESC) and
adult stem cells. ESC, (see Cross examination) are 'pluripotent'. They have the potential
to develop into cells of any organ. Adult stem cells are stem cells in various tissues and
organs in an adult, where they lie low until activated by illness. They are also found in
children and can be extracted from the blood of the umbilical cord.
Embryonic stem cells (ESC) can be both a bane and a benefit to scientists. It is very
difficult to tell which stem cell will form blood, skin, or liver tissue. Complex
biochemical solutions and other factors drive the process. Until the formula is found, ESC
cannot be tried out in humans. The danger with ESC is that they can grow into tumours or
change into unwanted tissues. For example, heart cells that are meant to repair, can morph
into dangerous bits of bone.
Unlike ESC, adult stem cells have not yet been found to transform into every kind of cell.
They may not be able to change into same cell type of the tissue from which they have been
removed. Also, adult stem cells are few in the body and hard to nurture in
"cultures".
But, the entire process is not so simple as it seems. After all, it is nature's secret of
life that science would be tampering with. And yet, it could give a chance for a dying
person to live. Like most scientific innovations, this new idea has also been dogged by
doubts...
Not for sale
Although stem cells have been curing people for years, these treatments have been
conducted through adult stem cells. The potential of adult stem cells was first tapped
about forty years ago. Bone-marrow transplants have infused fresh life into patients with
leukaemia and lymphoma. The work on ESC is, however, new.
In 1998, a scientist called James Thomson at the University of Wisconsin, succeeded in
removing cells from embryos and established the world's first embryonic stem cell line.
The discovery triggered a widespread debate.Politicians and religious leaders began to
raise some crucial questions onissues such as where were the embryos needed for the stem
cells, going to come from? And secondly, how many would have to be destroyed?
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A
microscopic view of bone stem cells. |
Most ESC that scientists use for
studying, are extracted from embryos created by in vitro fertilisation (a technique in
which egg cells are fertilised outside a woman's body.) Millions of frozen embryos are
stored worldwide in fertilisation clinics. Most of them will eventually be thrown away.
Instead, they are being used for studying stem cells.
Those who oppose the studying of ESC say that the blastocyst, from where the ESC are
removed, is a human being, which has feelings. And destroying a blastocyst would be
inhumane. Blastocysts in the early stage of evolution, do not possess even a nervous
system. Hence, biologically, they do not have feelings.
There are also some who find it unethical to grow human cells in other creatures.
Recently, scientists put human stem cells into the brains of mice. This is being seen as a
major breakthrough in medical science. Researchers hope that this could help them find
cures for brain diseases like Parkinson's.
Countries like the United States and Germany have imposed restrictions on stem cell
research. Others like Singapore, the UK, Korea and India, have not done so. Among the
developing nations, India leads on this front. However, here, scientists are allowed to
use stem cells only from discarded embryos and aborted foetuses. They plan to start the
trials on human bodies soon. Lets hope the magic seeds work… |
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