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.