Stem cells are the only cells in the body that has capacity to different cell types, like blood, bone and muscle cells. They also repair damaged tissue. Now, stem cells are essential element in treatment of blood cancer and blood disorder. Medical researchers believe that stem cells also have the potential to treat many other diseases.
Stem cells are the only cells in the body that can create specialized cells. They can make more than 200 specialized cells, such as blood and bone cells, among the trillions of cells in the body.
Function of Stem cells
Stem cells do two things that no other cells can do:
- They continuously renew and divide to make exact replicas of themselves. Typical or normal cells multiply and divide, but they have limited lifespans.
- They are the only cells that make specialized (differentiated) cells to replenish or repair specific cell types. Hematopoietic stem cells support blood and immune cells. Basal stem cells support skin cells. Mesenchymal stem cells support bone, cartilage, muscle and fat.
Blood Stem cells
Blood-forming stem cells are vital because they grow into different types of blood cells. The main types of blood cells are:
- White Blood Cells (WBC), which are part of immune system and help to fight invading infection
- Red Blood Cells (RBC), which help in oxygen transportation throughout body
- Platelets, which help in formation of blood clot and prevent bleeding at the time of injuries
Use of stem cells
Hematopoietic Stem cells can be used to replace damaged or abnormal bone marrow stem cells. For example, Hematopoietic stem cell transplants are done to replace stem cells in bone marrow. Doctors use them to treat
- Blood cancers such as types of leukemia, multiple myeloma and non-Hodgkin lymphoma, Myelo Dysplastic Syndrome.
- Blood Disorders such as sickle cell anemia, thalassemia, aplastic anemia, etc.
People with these diseases often need stem cell transplants after receiving intensive chemotherapy or radiation therapy to kill cancerous stem cells in their bone marrow, followed by stem cells infused from healthy donors.
Mechanism
Stem cell transplants do not usually work against cancer directly. Instead, they restore body's ability to produce new blood cells after treatment with the very high doses of chemotherapy and may be other treatments, such as radiation therapy, that are used to destroy cancer cells.
But in leukemia, the stem cell transplant may work against cancer directly. This happens because of an effect called graft-versus-tumor or graft-versus-leukemia, which can occur after transplants that use stem cells from a donor. This effect occurs when white blood cells from donor (the graft) attack any cancer cells that remain in patient’s body (the tumor or leukemia cells). This effect improves the chances of success of the transplant.
Types of Stem Cell Transplants
- Peripheral Blood Stem Cell Transplant - When stem cells collected from the blood stream, the transplant may be called a peripheral blood stem cell transplant, or PBSCT. It is usually done with mobilization of stem cells from bone marrow to peripheral blood with the help of mobilization agents.
- Bone Marrow Transplant - When blood stem cells collected from the bone marrow, transplant may be called as Bone Marrow Transplant (BMT). It is usually collected by piercing bone with specialised needles.
- Cord Blood Transplant – Stem cells collected from umbilical cord blood when a baby is born. The procedure may be called a Cord Blood Transplant.
Once the stem cells enter into bloodstream of patient, the stem cells travel to the bone marrow, where they take the place of the cells that were destroyed by treatment. Transplants can be:
- Autologous, which means the stem cells come from the patient (person with cancer treated and later stem cells mobilised with medications)
- Allogeneic, which means the stem cells come from some healthy donor after mobilisation of stem cells from marrow with medication. The donor may be a blood relative or someone who is not blood related. It is done only when HLA is fully or partly matched between donor and patient.
- Syngeneic, which means the stem cells come from patient’s identical twin
There are benefits and risks to both autologous and allogeneic stem cell transplants. With autologous transplants, the transplanted cells will match. But there is a small risk that cancer cells will be transplanted.
With allogeneic transplants, it is important that the cells match closely enough that immune system won’t see the transplanted blood stem cells as foreign and destroy them.
Role of blood centre
Peripheral blood stem cell Transplant procedures are carried by stem cells collected with apheresis procedure using automated equipment under the constant supervision of medical personnel after proper evaluation of donor/patient.
For donation of blood stem cells, donors receive injections of medication that are given under the skin (subcutaneously). The medication increases the number of blood stem cells in the bloodstream. The medication is usually started several days before donation. Once the desired level is achieved (usually 4-5 days), stem cells are collected.
During the donation, blood is usually taken through a tube (catheter) in a vein in an arm. The blood goes through apheresis instrument which takes out the stem cells. The remaining blood is then returned to the donor.This process is called apheresis. It is an outpatient procedure that typically takes up to 4 to 6 hours to complete. Some donors require multiple apheresis sessions, depending on how many blood stem cells are needed, diagnosis of the patient, etc.
Risks of Stem Cell Donation
The risks of this type of stem cell donation are minimal. The injection that increases the number of stem cells in the blood (mobilisation agent) can cause side effects, such as bone pain, muscle aches, headache, fatigue, nausea and vomiting.
Other possible side effects include being lightheaded or having chills, numbness or tingling around the mouth, and cramping in the hands. Side effects usually disappear within a couple of hours to days after the injections stop.
