Stem cell therapy is a form of treatment in which doctors use the patient’s own stem cells or those from a donor. In most cases, these are hematopoietic stem cells from the bone marrow (bone marrow transplant). Stem cells are found primarily in the bone marrow, blood, brain, liver, adipose tissue, and muscles.
Medical professionals distinguish between embryonic and adult stem cells. Embryonic stem cells are found in an embryo, whereas adult stem cells are present in the human body throughout a person’s lifetime. Stem cells possess extraordinary properties. They can regenerate, divide, or develop into other cell types (such as red and white blood cells and platelets).
In stem cell therapy, doctors introduce previously isolated and preserved stem cells into the recipient’s bloodstream via an infusion.
Stem cell therapy has been used successfully for decades to treat blood cancer (leukemia) and burns. Clinical trials are currently investigating its use in treating other diseases.
Stem cell therapy is most commonly used for blood disorders and cancers in which the bone marrow has been damaged by chemotherapy.
After high-dose chemotherapy, white blood cells (leukocytes)—which are responsible for the immune system—are particularly affected. Infusing stem cells into the bloodstream allows the hematopoietic system and the immune system to rebuild themselves.
Typical diseases treated with high-dose chemotherapy include:
Stem cell therapy is also successfully used to treat extensive, severe burns. In this procedure, medical professionals cultivate skin tissue from the patient’s own stem cells, which doctors then apply to the burned areas of skin.
A new procedure involves repairing damage to the cornea of the eye, such as that caused by chemical burns. In this procedure, doctors transplant stem cells into the eye so that the patient’s cornea can regenerate.
Currently, doctors are researching the effects of stem cell therapy on:
Cancer cells in the blood © psdesign1 / Fotolia
There are two main forms of stem cell therapy: autologous and allogeneic transplantation.
In autologous stem cell transplantation, doctors harvest the patient’s own stem cells, process them, and reinfuse them.
An allogeneic stem cell transplant involves transferring stem cells between two individuals—that is, between a donor and a recipient.
Which method is used depends on the clinical picture. Not every donor is suitable for an allogeneic transplant. Certain characteristics of the cell surfaces must match those of the recipient.
A disadvantage of this approach is that rejection reactions can occur more frequently.
Stem cell therapy is performed on an inpatient basis in a hospital. The first step is the collection of stem cells from the bone marrow, blood, or umbilical cord.
Stem cells are harvested from the bone marrow via a puncture of the pelvic bone. Doctors use a hollow needle to aspirate the bone marrow. Bone marrow transplantation is painful and complex and is rarely performed these days.
A common procedure is the collection of stem cells from the blood. In this process, doctors first stimulate the stem cells with growth factors to migrate from the bone marrow into the bloodstream.
Using an infusion needle, the donor’s blood is fed into a machine that separates the stem cells from
The third option for stem cell collection is umbilical cord blood. Doctors collect the stem cells from the umbilical cord blood immediately after a child is born.
After the stem cells are collected, they are preserved. Liquid nitrogen freezes the stem cells, which are then stored at -196 degrees Celsius. Once frozen, the stem cells can be transplanted into the recipient.
Autologous stem cell therapy involves chemotherapy prior to the transplant to reduce the number of cancer cells (conditioning phase).
Treatment with high-dose chemotherapy or radiation lasts between two and ten days. The transplant itself takes only one to two hours.
Healthy blood stem cells are administered to the recipient via an intravenous infusion. After about two weeks, new blood cells form from the stem cells.
The patient can be discharged from the hospital after three to four weeks if blood production is successful. Allogeneic stem cell therapy follows the same procedure as autologous treatment.
As an additional measure, the patient receives immunosuppressive drugs prior to the transplant. The goal is to reduce or prevent rejection of the donor stem cells.
Like other medical procedures, stem cell therapy is associated with certain risks and side effects.
Currently, this form of therapy is primarily used for cancer in combination with high-dose chemotherapy.
Chemotherapy generally has several known side effects, such as:
- Nausea
- Vomiting
- Inflammation of the mucous membranes
- Hair loss
- Organ damage (heart, lungs, liver, kidneys)
- Infections due to a weakened immune system
Stem cell transplantation itself also carries risks. These primarily include:
- acute allergic reactions
- life-threatening infections caused by viruses, bacteria, or fungi during the period between transplantation and the start of new blood formation
- Rejection of the donor stem cells
- Rarely: complete failure of the transplanted blood stem cells
Rejection reactions can range from mild to life-threatening. A specific form of rejection is graft-versus-host disease (GvHD).
In this case, the transplanted cells reject the recipient. GvHD can range from mild to severe and occurs primarily after allogeneic transplants.
In such cases, doctors use medications to suppress the immune system in order to prevent rejection reactions.
