Stem cells are the most controversial of all the therapies because of the "when does life begin" debate. For our purposes we will leave the moral and ethical debates outside our scope of discussion. We will look at what a stem cell is and why it may be helpful.
You know how some animals can re-grow body parts? Like a lizard re-growing his tail or a star fish re-growing an arm – turns out humans have many of the same skills. While we cannot re-grow an arm or a leg, we are constantly re-growing blood, skin, and other tissues.
The discovery of stem cells was made in the 1950's. The process of bone marrow transplantation is actually a form of stem cell therapy. The blood is one of the best natural re-growers. If we can transplant stem cells into a person’s bone marrow (the place where blood is created) we can create new blood cells. The cord blood therapy is just a variation of a bone marrow transplant.
Instead of needing a perfect match for a bone marrow transplant, a cord blood transplant uses stem cells from an umbilical cord what will re-grow blood cells in a new host (body). In 1998 the science of stem cell therapy began to really take hold when stem cells where isolated and kept alive in a laboratory. These cells where able to stay "unspecialized" for a long period of time. That means the stem cell was not a muscle cell or a nerve cell or a blood cell. It has the potential to be any of those cells – but it had not specialized (or differentiate) yet.
If we can isolate and specialize these cells – we can theoretically regenerate blood, skin, or nerve cells.
The human body has over 200 different specialized cells, but that whole package begins as just 30 to 34 cells in a blastocyst. These are the cells that have the entire recipe for creating a human being. This blastocyst is created 5 days after fertilization – this is where the “when does life begin” discussion really heats up. But from a science perspective – what makes these cells so unique. Could one of these cells be the key to re-growing brain cells or heart cells? Could the cure for some diseases or cancers be found here?
Stem cells are hard to find in human body – kind of like looking for a needle in a haystack. They hide deep in tissue, they are inconspicuous in size, shape and function and they are present in very low number. That is also one of the big advantages. If we only need a couple stem cells to maintain a lifetime of cell regeneration – that would be very helpful.
A stem cell itself cannot be transplanted because of the risk of tumors (teratomas), but if we can specialize (or differentiate) the stem cell it can be used to re-grow a needed cell type – say a brain cell. The theory is the new specialized brain stem cells could continue to regenerate new cells as needed. Adult has stem cells stationed about their body re-growing skin and blood and other tissues. Is there an adult specialized cell in the brain that could re-grow brain cells for a Tay-Sachs sufferer? The stem cells identified already in adults are in the obvious places like blood, skin and muscle – but they have also been found in livers, eyes, and the brain. Scientist are fairly certain there are more stem cells hidden in the body still to be discovered.
The embryonic stem cells appear to be more versatile then the adult stem cells. The 30 cells in the blastocyst can create 200 different cell types. In adults it was originally thought that a blood stem cell can only produce various blood cells. Some recent experiments say perhaps that is not actually true. While those cells are most incline to produce a blood cell – if properly stimulated they may be able to create other cells.
As you might imagine, this therapy has a lot of big potential and a lot of big risk. We really only started to understand stem cells in 1998 – we have a lot to learn still. Research is going on everywhere – despite what you might think. While embryonic stem cells grab all the headlines – lot of stem cells exist and are being tested. Bone marrow transplants have been happening for years and doctors have been growing patches of skins to graph on burn victims for years.
But many questions still remain unanswered. How do we transplant a differentiated stem cell in the brain? Can we harvest them from one’s own body? Can they continually regenerate brain cells? We have much to learn about his therapy – and some very smart people are trying to sort it all out.
For more information on stem cell therapy, check out these links: