STEM CELLS IN USE
In 1968, doctors performed the first successful bone marrow transplant. Bone marrow contains somatic stem cells that can produce all of the different cell types that make up our blood. It is transplanted routinely to treat a variety of blood and bone marrow diseases, blood cancers, and immune disorders. More recently, stem cells from the blood stream (called peripheral blood stem cells) and umbilical cord stem cells have been used to treat some of the same blood-based diseases.
Somatic Stem Cell Therapy: Using a Bone Marrow Transplant to Cure
Leukemia
Leukemia is a cancer of white blood cells, or leukocytes. Like other blood
cells, leukocytes develop from somatic stem cells. Mature leukocytes are
released into the bloodstream, where they work to fight off infections in our
bodies.Leukemia results when leukocytes begin to grow and function abnormally, becoming cancerous. These abnormal cells cannot fight off infection, and they interfere with the functions of other organs.
Successful treatment for leukemia depends on getting rid of all the abnormal leukocytes in the patient, allowing healthy ones to grow in their place. One way to do this is through chemotherapy, which uses potent drugs to target and kill the abnormal cells. When chemotherapy alone can't eliminate them all, physicians sometimes turn to bone marrow transplants.
In a bone marrow transplant, the patient's bone marrow stem cells are replaced with those from a healthy, matching donor. To do this, all of the patient's existing bone marrow and abnormal leukocytes are first killed using a combination of chemotherapy and radiation. Next, a sample of donor bone marrow containing healthy stem cells is introduced into the patient's bloodstream.
If the transplant is successful, the stem cells will migrate into the patient's bone marrow and begin producing new, healthy leukocytes to replace the abnormal cells.
New evidence suggests that bone marrow stem cells may be able to differentiate into cell types that make up tissues outside of the blood, such as liver and muscle. Scientists are exploring new uses for these stem cells that go beyond diseases of the blood.
Peripheral Blood Stem Cells
Since they can be obtained from drawn blood, PBSCs are easier to collect than bone marrow stem cells, which must be extracted from within bones. This makes PBSCs a less invasive treatment option than bone marrow stem cells. PBSCs are sparse in the bloodstream, however, so collecting enough to perform a transplant can pose a challenge.
Umbilical Cord Blood Stem Cells
Newborn infants no longer need their umbilical cords, so they have traditionally
been discarded as a by-product of the birth process. In recent years, however,
the stem-cell–rich blood found in the umbilical cord has proven useful in
treating the same types of health problems as those treated using bone marrow
stem cells and PBSCs.Umbilical cord blood stem cell transplants are less prone to rejection than either bone marrow or peripheral blood stem cells. This is probably because the cells have not yet developed the features that can be recognized and attacked by the recipient's immune system. Also, because umbilical cord blood lacks well-developed immune cells, there is less chance that the transplanted cells will attack the recipient's body, a problem called graft versus host disease.
Both the versatility and availability of umbilical cord blood stem cells makes them a potent resource for transplant therapies.
What Is the Difference between Cord Blood Stem Cells and Embryonic Stem Cells Used in Research?
You may have heard of the ethical debate surrounding stem cell research. This debate is focused on the use of embryonic stem cells. If you are considering banking your child’s cord blood, rest assured that cord blood stem cells are not part of this controversy.Many people oppose the use of embryonic stem cells because a human embryo must be destroyed to harvest these cells. Cord blood stem cells are not embryonic stem cells, but are instead part of an uncontroversial group of stem cells called adult stem cells. No embryos are destroyed in the collection of cord blood stem cells.
Embryonic Stem Cells
Embryonic stem cells are a type of stem cell derived from embryos fertilized in an in vitro fertilization clinic. These cells are not derived directly from embryos developing in a woman’s body.The embryos that are used to isolate embryonic stem cells are usually about four or five days old and referred to as blastocysts. The inner cell mass of the blastocyst contains about 30 cells that scientists can isolate and transfer to a culture dish. In this culture dish, the cells divide and proliferate. In only 6 months time, the total number of embryonic stem cells can be in the millions.
Embryonic stem cells are pluripotent, which means they have the ability to give rise to all other cell types in the human body. It is this property that is intriguing to researchers. If it is determined how these cells differentiate into specific cells in the human body, scientists may be able to create cultures of specific cell types. Stem cell transplants using these cells may be the key to successfully treating diseases like Alzheimer’s, Parkinson’s, diabetes, heart disease, and even spinal cord injuries.
Cord Blood Stem Cells
Cord blood stem cells are not embryonic stem cells and are free from the controversy that surrounds them. In fact, cord blood stem cells belong to a different group of stem cells entirely called adult stem cells. No embryos are destroyed in the collected of cord blood stem cells.Cord blood refers to the blood that remains in the umbilical cord and in the placenta after birth. Typically, the umbilical cord and placenta are discarded, but the blood found inside is rich in a type of stem cell called hematopoietic stem cells. Hematopoietic stem cells can differentiate into all types of blood cells and are currently used to treat over 70 diseases such as leukemia and other cancers.
The hematopoietic stem cell is the most frequently studied and used stem cell. Additionally, these cells have the largest proven application to clinical practice and have been used in transplantation for over 30 years!
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