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Saturday, May 1, 2010

What Is a Blood and Marrow Stem Cell Transplant and WHY ?


[Extracted from US Department of Health and Human Services - Natural Institutes of Health]

A blood and marrow stem cell transplant replaces a person's abnormal stem cells with healthy ones from another person (a donor). This procedure allows the recipient to get new stem cells that work properly.

Stem cells are found in bone marrow, a sponge-like tissue inside the bones. Stem cells develop into the three types of blood cells that the body needs :

* Red blood cells, which carry oxygen through the body
* White blood cells, which fight infection
* Platelets (PLATE-lets), which help the blood clot

Small numbers of stem cells also are found in the blood and in the umbilical cord (the cord that connects a fetus to its mother's placenta).

Another type of stem cell, called an embryonic stem cell, can develop into any type of cell in the body. These cells aren't found in bone marrow.

Overview

Doctors use stem cell transplants to treat people who have :

* Certain cancers, such as leukemia. The high doses of chemotherapy and radiation used to treat some cancers can severely damage or destroy bone marrow. A transplant replaces the stem cells that the treatment destroyed.

* Severe blood diseases, such as thalassemias, aplastic anemia, and sickle cell anemia. In these diseases, the body doesn't make enough red blood cells or they don't work properly.

* Certain immune-deficiency diseases that prevent the body from making some kinds of white blood cells. Without these cells, a person can develop life-threatening infections. A transplant provides stem cells to replace the missing white blood cells.

Types of Transplants

The two main types of stem cell transplants are autologous and allogenic.

For an autologous transplant, your own stem cells are collected and stored for use later on. This works best when you still have enough healthy stem cells, even though you’re sick. If you have cancer, the cancer cells are removed or destroyed from the collected cells.

For an allogenic transplant, you get stem cells from a donor. The donor can be a relative (like a brother or sister) or an unrelated person. You also may get stem cells from umbilical cord blood donated by an unrelated person.

To prevent problems, the donor's stem cells should match yours as closely as possible. Donors and recipients are matched through a blood test called HLA tissue typing.



Collection Process

Stem cells used in transplants are collected from donors in several ways.

A procedure called apheresis (a-fer-E-sis) may be used. For this procedure, a needle is placed in the donor's arm to draw blood. Then, his or her blood is passed through a machine that removes the stem cells from the blood. The rest of the blood is returned to the donor.

Stem cells may be collected directly from a donor's pelvis. This procedure isn't used very much anymore because it must be done in a hospital using local or general anesthesia (AN-es-THE-ze-a). For this procedure, a hollow needle is inserted repeatedly into the pelvis, and marrow is sucked out of the bone.

Blood containing stem cells may be collected from an umbilical cord and placenta after a baby is born. The blood is frozen and stored at a cord blood bank for future use.

Outlook

Stem cell transplants have serious risks. Some complications are life threatening. For some people, however, stem cell transplants are the best hope for a cure or a longer life.

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Although many people may think of a transplant to mean replacing a diseased organ with another one, such as in heart or liver transplants, stem cells have an important and often life saving use for treating disease.

A stem cell transplant doesn't involve surgery in the same sense as an organ transplant and the procedure is simplistic in comparison. Its benefit, however, can be just as enormous.

What is a Stem Cell Transplant ?

In basic terms, a stem cell transplant is the infusion of healthy cells to replace diseased or damaged ones. If successful, the healthy replacement stem cells will integrate into the body and give rise to more cells that can all take on the necessary functions for a specific tissue.

Current Stem Cell Transplant Treatments

There are current treatments that have shown success over the years and it is anticipated that the therapies will be further refined to improve success rates.

Cancer

Cancer, particularly leukaemia, is an important disease for stem cell transplants; bone and peripheral blood stem cell transplants have been used for decades. A patient receives chemotherapy or radiation treatment to destroy the cancer cells but unfortunately, healthy cells are also damaged. A stem cell transplant can replace the lost and damaged cells with fresh, functioning ones, which can then provide the red blood cells, white blood cells and platelets that are important to metabolism, clotting and immunity. The other benefit of this treatment is that the newly formed white blood cells can further improve immune function such that they destroy any remaining cancer cells in the marrow.

Aplastic Anaemia

Aplastic anaemia is a condition that is not cancerous but rather, involves a reduction in the production of blood cells by the bone marrow. A stem cell transplant can replace the dysfunctional marrow with new functioning stem cells. These stem cells then travel from the bloodstream to the marrow where ideally, they begin to work properly and produce healthy working blood cells.

Potential Future Transplant Treatments

Success has already been shown in studies with stem cell transplants for a variety of diseases but more research is required before these can be performed regularly. Some of the diseases that could benefit from stem cell transplants are:

* Parkinson's disease - replacing destroyed brain cells with healthy ones.

* Type I diabetes - providing viable functioning stem cells for the pancreas.

* Retinal diseases - transplanting stem cells to replace those in the retina that have been damaged by disease.

What Are The Risks ?

Stem cell transplants still have several risks associated with the procedure. Some people will find they experience few issues while others may require consistent monitoring and repeated hospital stays. Some of the complications that can occur with a stem cell transplant are :

* Damage to organs or blood vessels

* Graft versus host disease

* Death

Thus, although some people will experience few complications, others may find they suffer from short and long-term problems associated with a stem cell transplant. The success varies widely and it is impossible to predict who will experience side effects and to what degree they will occur.

In most cases, the benefits of stem cell transplants will likely outweigh the risk of complications and these techniques can truly be life-saving for conditions such as leukaemia and aplastic anaemia. It is hoped and anticipated that future research can yield successful therapies for a broader range of diseases.

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