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) 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?).
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 childrenand 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...
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.
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?
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. lastocysts 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…