Stem Cells
Stem cells are in the news almost constantly. You could think of them as the biological equivalent of the Swiss Army knife. Except, in this case, there are about 200 different tools (types of cells) built in. But you can only pull out one blade or tool at a time. And once you have, you can’t use any other tool. (Stem cells can give rise to cells with specific functions but those cells cannot usually go back to being stem cells.) Stem cells can also give rise to more stem cells so that they persist for a long time. (Try doing that with a Swiss Army knife!)
There are embryonic stem cells and adult stem cells. In mice or man (or any other mammal) embryonic stem cells are obtained from the center of a blastocyst. The name blastocyst sounds like something painful to me. But it is the name for an embryo 5 days after a sperm has fertilized an egg when it is still smaller than a period. Among the adult stem cells that are known, there are hematopoietic stem cells (that give rise to your blood cells), ones for generating brain cells, the outer layer of the skin, the lining of your digestive tract etc.
What makes embryonic stem cells special compared to adult stem cells is that they have the full 200 tools but adult stem cells do not. And scientists have mastered the art of getting the embryonic stem cells to grow very well in culture.
I’m proud to say that immunology led the way in the field of stem cells. Hematopoietic or blood stem cells were discovered way back when Immuoman was just an immunokid (the 1950s). Since then thousands of patients with cancer and other diseases of the blood have been saved by bone marrow and hematopoietic stem cell transplantation. In contrast, embryonic stem cells were not discovered until the 1980s in mice and in humans in 1998.
Recently, scientists at UCLA were able to take a mouse fibroblast (a cell that provides structure to tissues such as the underlying layer of the skin), and put genetic material into them that released the expression of genes for all the functions of other cells (unlocked the other tools in the knife). In essence, what they have done is to take a “run of the mill” adult cell (not even a stem cell of any kind) and turn it into an embryonic stem cell. If this can be repeated with human cells, the whole debate about using embryonic stem cells for research and medicine will become obsolete.
For now, however, the moral and ethical dilemmas related to the use of embryonic stem cells rage on. The core theological question is: When does a human being become a human being? If the blastocyst is already human, then we tread a slippery slope by exploiting these tissues. If a person does not become a person until later in development, then the answer is very different. The potential to save thousands, perhaps millions of lives also weighs in the balance. This is why the debate over embryonic stem cells is probably the single most complex bioethical issue facing the world today.
In the not too distant future, stem cells could allow medicine to do for patients with illnesses such as diabetes, Parkinson’s disease, strokes, burns, heart disease, Alzheimer’s disease and trauma what bone marrow transplantation has already done for thousands of patients with blood disorders. These cells could also be used for basic medical research and drug testing. And they could be used to engineer whole tissues and organs for the replacement of diseased or worn out parts. The potential impact of stem cells is staggering and we may not even yet have a full vision of what they could do for the human race. It’s like the old adage: “It is possible to count the seeds in an apple, but how many apples are in a seed?” So we might ask today: How many human lives are in one small cell? The answer is huge.
I highly recommend the following free booklets on the web: http://dels.nas.edu/bls/stemcells/booklet.shtml http://stemcells.nih.gov/info/basics/