What is a Bone Marrow Transplant?

National Marrow Donor Program. Related ArticlesBone marrow transplantMarrow Donor - Finding a Bone Marrow or Stem Cell DonorEngraftmentStem Cell Transplant - How are Stem Cells Collected for TransplantBone Marrow Transplants -- Understanding the Immune System, Including Autoi...

In addition, the bone marrow contains hematopoietic stem cells, which give rise to the three classes of blood cells that are found in the circulation: white blood cells (leukocytes), red blood cells (erythrocytes), and platelets (thrombocytes). Biological compartmentalization is evident within the bone marrow, in that certain cell types tend to aggregate in specific areas. For instance, erythrocytes, macrophages, and their precursors tend to gather around blood vessels, while granulocytes gather at the borders of the bone marrow.

The red bone marrow is a key element of the lymphatic system, being one of the primary lymphoid organs that generate lymphocytes from immature hematopoietic progenitor cells. 2 The bone marrow and thymus constitute the primary lymphoid tissues involved in the production and early selection of lymphocytes. Furthermore, bone marrow performs a valve-like function to prevent the backflow of lymphatic fluid in the lymphatic system.

The normal bone marrow architecture can be damaged or displaced by aplastic anemia, malignancies such as multiple myeloma, or infections such as tuberculosis, leading to a decrease in the production of blood cells and blood platelets. The bone marrow can also be affected by various forms of leukemia, which attacks its hematologic progenitor cells. 5 Furthermore, exposure to radiation or chemotherapy will kill many of the rapidly dividing cells of the bone marrow, and will therefore result in a depressed immune system.

Many of the symptoms of radiation sickness are due to damage sustained by the bone marrow cells. To diagnose diseases involving the bone marrow, a bone marrow aspiration is sometimes performed. This typically involves using a hollow needle to acquire a sample of red bone marrow from the crest of the ilium under general or local anesthesia.

Bone marrow examination is the pathologic analysis of samples of bone marrow obtained via biopsy and bone marrow aspiration. Bone marrow examination is used in the diagnosis of a number of conditions, including leukemia, multiple myeloma, anemia, and pancytopenia. The bone marrow produces the cellular elements of the blood, including platelets, red blood cells and white blood cells.

While much information can be gleaned by testing the blood itself (drawn from a vein by phlebotomy), it is sometimes necessary to examine the source of the blood cells in the bone marrow to obtain more information on hematopoiesis; this is the role of bone marrow aspiration and biopsy. The ratio between myeloid series and erythroid cells is relevant to bone marrow function, and also to diseases of the bone marrow and peripheral blood, such as leukemia and anemia. The normal myeloid-to-erythroid ratio is around 3:1; this ratio may increase in myelogenous leukemias, decrease in polycythemias, and reverse in cases of thalassemia.

In a bone marrow transplant, hematopoietic stem cells are removed from a person and infused into another person (allogenic) or into the same person at a later time (autologous). If the donor and recipient are compatible, these infused cells will then travel to the bone marrow and initiate blood cell production. Transplantation from one person to another is conducted for the treatment of severe bone marrow diseases, such as congenital defects, autoimmune diseases or malignancies.

The patient's own marrow is first killed off with drugs or radiation, and then the new stem cells are introduced. Before radiation therapy or chemotherapy in cases of cancer, some of the patient's hematopoietic stem cells are sometimes harvested and later infused back when the therapy is finished to restore the immune system. The stem cells are typically harvested directly from the red marrow in the iliac crest, often under general anesthesia.

The procedure is minimally invasive and does not require stitches afterwards. Depending on the donor's health and reaction to the procedure, the actual harvesting can be an outpatient procedure, or can require 1–2 days of recovery in the hospital. Another option is to administer certain drugs that stimulate the release of stem cells from the bone marrow into circulating blood.

8 An IV is inserted into the donor's arm, and the stem cells are filtered out of the blood. This procedure is similar to donating blood or platelets. In adults, bone marrow may also be taken from the sternum, while the tibia is often used when taking samples from infants.

9 In newborns, stem cells may be retrieved from the umbilical cord. Many cultures have used bone marrow as food throughout history. Some anthropologists believe that early humans were scavengers rather than hunters in some regions of the world.

Marrow would have been a useful food source (largely due to its fat content) for tool-using hominids, who were able to crack open the bones of carcasses left by apex predators such as lions. European diners in the 18th century often used a marrow scoop (or marrow spoon), often of silver and with a long, thin bowl, as a table implement for removing marrow from a bone. Bone marrow was also used in various preparations, such as pemmican.

Bone marrow's popularity as a food is now relatively limited in the western world, but it remains in use in some gourmet restaurants, and is popular among food enthusiasts. In Vietnam, beef bone marrow is used as the soup base for the national staple dish, ph? , while in the Philippines, the soup bulalo is made primarily of beef stock and marrow bones, seasoned with vegetables and boiled meat; a similar soup in the Philippines is called kansi.

13 In Indonesia, bone marrow is called sumsum and can be found especially in Minangkabau cuisine. Sumsum is often cooked as soup or as gulai (a curry-like dish). In India and Pakistan, slow-cooked marrow is the core ingredient of the dish nalli nihari.

In Hungary, tibia is a main ingredient of beef soup; the bone is chopped into 10–15 cm pieces, and the ends are covered with salt to prevent the marrow from leaking from the bone while cooking. Upon serving the soup, the marrow is usually spread on toast. Beef bone marrow is also the main ingredient in Italian dish ossobuco (braised veal shanks), and beef marrow bones are often included in the French pot-au-feu broth, the cooked marrow being traditionally eaten on toasted bread with sprinkled coarse sea salt.

In Iranian cuisine, lamb shanks are usually broken before cooking to allow diners to suck out and eat the marrow when the dish is served. Similar practices are also common in Pakistani cuisine. Some Native Alaskans eat the bone marrow of caribou and moose.

Cooper, B (2011). "The origins of bone marrow as the seedbed of our blood: from antiquity to the time of Osler". Baylor University Medical Center Proceedings 24 (2): 115–8.