Bone Marrow - Blood Cells and Platelets, Importance, Transplants
Know your Body

Bone Marrow : The Source of Blood Cells and Platelets

Dr.Surya Rao Poodipeddi profile Authored by Dr.Surya Rao Poodipeddi on 7 Mar 2014 - 16:16.

Bone marrow is a soft fatty tissue present inside the cavities of bones. It is the principal source for all the red blood cells, platelets and most of the white blood cells. 

Blood cells are formed in the marrow of flat bones. The main flat bones from where blood cells are formed are shoulder blades, ribs, breastbone and the pelvis. All the blood cells are derived from a single type of cell called the stem cell. The body’s hormones control production of stem cells as per body needs including a substance called erythropoietin produced by the kidneys.

The hormones responsible to control the production of stem cells include thyroid hormones, the growth hormone secreted by the pituitary and the corticosteroids secreted by the adrenal glands. 

Red blood cells, platelets, white blood cells and fat cells in the bone marrow are nourished by tiny blood vessels called sinusoids, which also carry away the wastes.

The blood cells manufactured by the stem cells in the bone marrow have important and vital functions. The white blood cells are the warriors to fight infection. The red blood cells carry oxygen to and remove waste products like carbon dioxide from organs and tissues. The platelets are responsible for the blood to clot 

Though most of the stem cells are found in the bone marrow some stem cells can also be found in the blood stream, which are called PBSCs (Peripheral Blood Stem Cells). Blood in the umbilical cord also contains some stem cells. They have a capacity to divide and form more stem cells as well as an ability to mature into white blood cells, red blood cells and platelets.

Apart from manufacturing blood cells the stem cells play an important role in bone marrow transplants.

Bone Marrow Transplants (BMT) means collecting bone marrow from a donors bones and transplanting it into the recipient whose stem cells are destroyed either due to a disease or due to high doses of chemotherapy or radiation therapy given in cases of blood cancer. PBSCT (Peripheral Blood Stem Cell Transplants) also has similar function.

There are three types of bone marrow transplants.

  •  Antilogous Transplants where patients receive their own stem cells.
  • Syngeneic Transplants where the recipient receives marrow from his/her identical twin.
  • Allogeneic Transplants where the patient receives stem cells from someone other than the patient himself/herself or an identical twin. In this type of transplants the patient receives stem cells from his/her brother, sister or parents or an unrelated person if there is perfect matching.

The main purpose of BMT and PBSCT transplant in patients on cancer treatment is to make it possible for patients to receive higher doses of chemotherapy (drugs specifically meant for cancer treatment) and/or radiation. In order to appreciate how these procedures work one should know the basics as to how chemotherapy and radiation therapy work.

In patients with cancer, the cell division occurs rapidly and the cancer cells multiply to enormous numbers, whose division can be arrested by chemotherapy. However, this is not so in normal healthy cells. Thus the chemotherapy may as well destroy the rapidly dividing bone marrow cells.

Consequently the destruction of normal stem cells by these drugs and/or radiation leads to less formation of red blood cells, white blood cells and the platelets which in turn leads to lack of oxygen carrying capacity, lack of capacity to fight infection and reduced capacity in clotting of blood. Thus bone marrow transplants counter the effects of chemotherapy and/or radiation in making good the manufacture of the stem cells, which in turn will manufacture the blood cells to restore normal functioning.
 

Bone marrow transplants whether BMT or PBSCT are the main weapons in the treatment of Leukemia and Lymphoma. Aplastic anemia where there is congenital absence of bone marrow formation can be tackled only through bone marrow transplant. They are also used in the treatment of childhood brain tumors and a disease called neuroblastoma (an uncommon and rare disease affecting newborns)

Cure for diseases: Researchers are working day and night to explore the possibility of a cure with bone marrow transplants in patients with breast cancer, ovarian tumors and a kidney tumor called Wilm’s tumor and a dangerous condition called multiple myeloma. Bone marrow transplants serve as a parameter to evaluate remissions or recurrence of leukemia in a patient.

The most essential requirement of bone marrow transplant is a perfect matching of the donors and recipients’ marrow or at least as close a match as possible. It needs an elaborate testing of different sets of proteins called human leukocyte-associated antigens. Everything depends on how closely these antigens in the recipient match with the donors antigens.

The process of collecting bone marrow from a donor is called harvesting. The donor is given a general anesthesia. It can be done under local anesthesia also. Several cuts, not requiring stitches are made on the pelvic bone (The Hipbone) or the breastbone. A large needle is inserted through the cuts in to the marrow cavity and the marrow is aspirated and collected.

The procedure may take around half an hour. The harvested bone marrow is then processed to remove blood and bone fragments. It can be transplanted immediately or preserved for several years by combining a preservative and placed in a liquid nitrogen freezer to keep the stem cells alive until they are required.

In cases where PBSC’s are transplanted the procedure is altogether different. The procedure to collect peripheral blood stem cells is called aphaeresis. The patient is given a medication for about 4 to 5 days to enhance the release of stem cells into the blood stream. Blood is removed through a central venous catheter (a flexible tube placed in a large vein in the neck or the chest area). |

One can also use a large vein to place a needle. The blood is sent to a machine, which removes the stem cells. The blood is then returned to the patient/. The collected stem cells are stored. The entire procedure may take around 4 to 5 hours. It may be necessary to treat the collected cells with a drug to remove any cancer cells, stored in a freezer and transplanted when necessary.

There are no complications in the donor except probably the effects of general anesthesia if any. The donor’s body is capable of replacing the bone marrow within weeks. He may feel bit tired. Recovering strength after donating bone marrow may need few days to few weeks in some.

If PBSC is chosen the donor will have no problems except the effects of the drug given to enhance release of stem cells in to the periphery. There may be some muscle and bone aches, which will last only for a couple of days.

Major complications in the recipient include infection and rejection if not properly matched.

 

*Disclaimer: This is not medical advice. The content is for educational purposes only. Please contact your doctor for any health care issues.