Stem cells can be extracted from bone marrow, blood, or embryos using three different methods. The method of harvesting stem cells from peripheral blood is preferred because it is considered safer and does not require anesthesia for either the donor or the patient. Embryonic stem cell harvesting, which involves destroying an embryo in order to extract stem cells, is fraught with moral and ethical issues. Bone marrow stem cell harvesting is an older method that is still used when blood stem cells are insufficient.
Peripheral blood can be autologous, meaning it comes from the patient, or allogenic, meaning it comes from a third party. Each arm has two intravenous devices, one that draws blood from the body and the other that returns it. Before the blood is returned to the donor, a machine separates the stem cells from it.
The donor is given a drug that promotes white cell formation in the bone marrow before this method of stem cell harvesting begins. In most cases, there are very few stem cells in the blood that can be harvested. These drugs stimulate the production of a large number of white blood cells in the bone marrow. Because the bone marrow can no longer hold all of these cells, they are released into the bloodstream and harvested. To be effective, stem cell transplants require millions of these cells.
This type of harvesting necessitates precision timing in order to capture cells as they mature into white blood cells. The drugs used in the procedure cause cells to mature quickly into forms that are unfit for harvesting. Donors are typically tested on a regular basis to determine the best time to harvest.
Hundreds of stem cells form as a human embryo develops. The embryo dies when these stem cells are extracted. Animal research found a way to remove one cell from an eight-cell embryo, which was then manipulated by contact with other embryonic stem cells and grew its own stem cells. The remaining seven-cell embryo was implanted in the womb of a rat and gave birth to healthy offspring. By preserving the original embryo, scientists hope to resolve the controversy surrounding stem cell extraction.
When a patient receives allogenic stem cell harvesting, he or she is usually receiving chemotherapy to treat cancer. These chemicals cause his or her bone marrow to produce white blood cells in order to fight foreign substances. Drugs that cause the same reaction in healthy donors who aren’t receiving chemotherapy have been developed, and these drugs are commonly given to cancer patients to boost stem cell production in their bone marrow.
Before cells can be extracted from bone marrow, anesthesia is required. Large bones are typically the best sources of stem cells, with some doctors preferring the pelvic bone. This method of stem cell harvesting is a more complicated procedure that usually causes more pain. When sufficient stem cells cannot be extracted from the blood, this procedure is used.
The harvesting of peripheral blood stem cells can be repeated until enough cells are available. As the marrow works to produce more blood and white blood cells, the patient may experience bone pain. In most cases, over-the-counter pain relievers the procedure’s discomfort. Recovery is usually quick, with no long-term consequences.