Introduction To Stem Cells


The term "stem cell" refers to a cell that can give rise to a variety of other cells like the stem of a flower can give rise to leaves, other stems and flowers, etc. There are many different kinds of stem cells. One type that is getting a lot of attention in the media these days is the "embryonic" stem cell. These cells are usually isolated from an unborn fetus and under the right circumstances have the ability to make virtually any cell in our bodies. The use of this kind of stem cell is and exciting future prospect thought there are certain moral issues that cloud the research.

Another type of stem cell is the "hematopoietic" stem cell. This kind of stem cell can be isolated from fully formed individuals and has the capability to make all of the cells in our blood and immune system including infection-fighting white blood cells, oxygen-carrying red blood cells and blood-clotting platelets. The hematopoietic stem cell is what our transplant program uses when we perform a "stem cell" transplant. In adults, these cells are found chiefly in the bone marrow but, under the right circumstances, they can be induced to go out into the blood stream.
 
Because hematopoetic stem cells are found in the marrow they were historically collected through a bone marrow harvesting procedure in the operating room before we learned that we could "mobilize" them into the blood. Bone marrow is harvested in a one-hour hospital procedure using anesthesia. Typically, several small cuts (not requiring stitches) are made in the skin over the large bones at the base of your back and a large needle is used to withdraw bone marrow through these cuts. Today, stem cells are more commonly obtained from the bloodstream by a process called apheresis after being "mobilized". Apheresis is a safe outpatient procedure. Both bone marrow harvesting and apheresis provide stem-cell support that allows doctors to give intensive therapy without permanently harming a cancer patient's immune system or causing irreversible marrow damage.

Hematopoietic stem cells can also be isolated from the umbilical cord blood from a newborn baby. These "cord blood" stem cells can also be used for transplant but because they are low in number and the infant's immune system is not fully formed they are more difficult transplants for adults. Our program is not currently using cord blood stem cells but may in the near future.


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