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Bone Marrow Sampling and Transplants
Bone marrow transplant is a potential cure for several diseases, including cancer and specific genetic disorders. Notably, this procedure is applicabl…
Bone marrow transplants replace diseased marrow with healthy marrow from a compatible host. It can cure several cancers and genetic disorders like thalassemia.
The donor-recipient compatibility or disease diagnosis is confirmed using a biopsy — a diagnostic test for a sample of red bone marrow.
Red bone marrow is typically harvested from the iliac crest of the donor's hip bone.
Before transplanting the healthy marrow, the patient's affected marrow is destroyed by chemotherapy or radiation to avoid eliciting immune responses to donor marrow.
The healthy marrow is then injected into the patient's veins, from where it migrates to the bone marrow cavities for donor stem cells to multiply.
Once the donor cells establish themselves, the recipient's marrow gets replaced with healthy cells.
An incompatibility of transplanted marrow may cause graft-versus-host reactions.
Graft-rejection risks can be substantially minimized by utilizing the stem cells obtained from the umbilical cord at birth, which can be stored in cord blood banks for future transplantation.
Alternatively, the patient's somatic cells can be genetically reprogrammed to induced pluripotent stem cells for transplant.
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Q1: What diseases can bone marrow transplants treat?
Bone marrow transplants can cure several cancers and genetic disorders. These include aplastic anemia, leukemia, Hodgkin's disease, non-Hodgkin's lymphoma, multiple myeloma, thalassemia, sickle-cell disease, and severe combined immunodeficiency disease (SCID). The procedure replaces diseased marrow with healthy marrow from a compatible donor, allowing donor stem cells to multiply and restore normal blood cell production.
Q2: Where is bone marrow harvested from donors?
Red bone marrow is typically harvested from the iliac crest, which is the upper portion of the donor's hip bone. This location provides accessible red bone marrow containing hematopoietic stem cells needed for transplantation. The harvested marrow is then processed and prepared for injection into the recipient's veins.
Q3: Why is chemotherapy or radiation used before bone marrow transplant?
High doses of chemotherapy and radiation destroy the recipient's affected or cancerous red bone marrow before transplant. This conditioning treatment eliminates diseased cells and reduces the risk of transplant rejection by suppressing the recipient's immune system. It creates space in the bone marrow cavities for donor stem cells to establish themselves and multiply.
Q4: What is graft-versus-host disease in bone marrow transplants?
Graft-versus-host disease occurs when transplanted marrow produces T cells that attack the recipient's tissues, causing an incompatibility reaction. This is a major risk of bone marrow transplants. The severity depends on donor-recipient compatibility. Using cord blood stem cells or induced pluripotent stem cells can substantially minimize this risk compared to traditional bone marrow transplants.
Q5: How do cord blood stem cells differ from bone marrow transplants?
Cord blood stem cells are collected from the umbilical cord at birth and stored in cord blood banks for future use. They are less likely to cause graft-versus-host disease and require less precise donor-recipient matching than bone marrow. Cord blood cells can be stored indefinitely, provide a larger donor pool, and are less likely to transmit infections, making them a promising alternative to traditional bone marrow transplants.
Q6: How is bone marrow transplant compatibility confirmed?
A biopsy is used as a diagnostic test to confirm donor-recipient compatibility and verify the disease diagnosis before transplant. This sample of red bone marrow helps determine if the donor and recipient are immunologically matched. Proper matching reduces the risk of graft rejection and graft-versus-host reactions, improving transplant success rates.
Q7: What happens after healthy marrow is injected into the recipient?
After injection into the patient's veins, healthy marrow migrates to the bone marrow cavities where donor stem cells multiply and establish themselves. Once the donor cells are engrafted, they gradually replace the recipient's marrow with healthy, noncancerous cells. The recipient remains vulnerable to infections for 2-3 weeks until the transplanted marrow produces enough white blood cells for immune function.