Stem Cells in Action
A bit confused as to how that frozen cord blood and those stem cells go from the freezer to saving your life? You’re not alone. The mechanics of stem cell therapy is typically a bit of a mystery to most of the population. But it doesn’t have to be. This overview will help you understand just what happens, not to mention allow you to impress all your friends the next time the topic of stem cells comes up.
From Stem Cell to Particular Cell
As you likely already know, a stem cell is a type of cell that has the ability to become another cell in the body. The more primitive (less developed) the stem cell, the greater its ability to differentiate (become another cell). Stem cells found in cord blood, though classified as adult stem cells, are much more primitive than those stem cells found in bone marrow or peripheral blood. Therefore, cord blood stem cells can differentiate into a wider variety of cells in the body.
While differentiation does occur naturally in the body, through stem cell research, scientists have learned how to artificially differentiate a stem cell into the type of cell they need. However, this process has not been perfected. Because researchers don’t know exactly which signals normally start the differentiation process, they use chemicals to manipulate and influence the cells. When the stem cells have differentiated, they can be transplanted, usually through injection, into a recipient.
But why use stem cell transplants to help someone with a certain cancer, blood disorder, or genetic disorder? Because stem cells are capable of continuously reproducing themselves. Therefore, when the blood and immune systems are not working efficiently, a stem cell transplant can greatly improve an individual’s blood production.
For example, leukemia causes the body to produce an abundance of white blood cells (WBC). Through chemotherapy, the cancerous WBC are destroyed. However, WBC are what make up a healthy immune system; without them, we are vulnerable to many diseases and illnesses. To help improve a person’s chance of recovery from leukemia, cord blood stem cells can be manipulated to become white blood cells, which are then transplanted to help encourage a full recovery from the cancer.
You’ve probably heard a lot about finding a "perfect match" for a transplant. No, this does not refer to a romantic match-making attempt. Rather, it refers to finding a match for Human Leukocyte Antigens (HLA). Made up of six different antigen groups, HLA is a type of protein located on the outside surface of a cell. From the six groups, there are three that are thought to be the most important when finding a suitable blood sample for a stem cell transplant: HLA-A, HLA-B, and HLA-DR. Each group of antigens contain two antigens – one from the mother and one from the father. In total, there are six individual antigens that need to be matched.
When performing a transplant, the ideal is to have a 6/6 HLA match. In the case of bone marrow, a transplant may be done if a 5/6 HLA match can be located. With cord blood transplants, though, a 4/6 HLA match is considered sufficient to proceed with the transplant. Since cord blood stem cells are more primitive than bone marrow stem cells, there is less risk of the cells attacking a patient’s immune system.
Another issue with stem cell treatment using cord blood is that, in general, this type of transplant is thought to be best suited to children and small adults (those weighing less than 110lbs). This is because the number of stem cells needs to be matched to the weight of the patient. However, as cord blood transplants are performed more often, techniques have improved. Additionally, a handful of transplants have been successfully done using cord blood stem cells from two separate donors. This is a promising sign that cord blood transplants can be used for almost anyone, regardless of size or age.