Bone Marrow

Marrow is a soft matter found inside the long bones of vertebrates that produces red and white blood cells, platelets and lymphocytes. The cells produced by marrow are "stem cells" with the capacity to develop into different kinds of cells. The process by which the marrow makes the components of blood from stem cells is called hematopoiesis. Since the marrow is the only source of blood, it is vitally important that it stay healthy. Diseases that are rooted in or affect the bone marrow and impair the production of blood include leukemia, multiple myeloma, aplastic anemia, sickle cell anemia, polycythemia vera, myelofibrosis, and lymphoma. In addition to disease, bone marrow cells are vulnerable to radiation and to chemotherapy treatments for cancer.

Background

The bone marrow of animals is edible and considered a delicacy in some cuisines. Cattle and sheep are two animals whose marrow is widely consumed. Removing the marrow from the bones can present difficulties. Eighteenth century upper-class Europeans used narrow spoons designed to dig the marrow out of cooked bones. Sometimes bones are split and the marrow is served in the bone. Cooked marrow is soft enough to be spread on toast. Marrow can also serve as a base for soup, as in the Vietnamese national dish pho. Bone marrow is rich in fat, and scavenging marrow from the bones of the kills of predators may have been one of the earliest ways that humans were able to incorporate animal fat into their diets. So-called paleo diets, meant to emulate the diet of our earliest human ancestors, often prominently feature bone marrow.

Marrow is divided into two types: red marrow, which produces blood cells, and yellow marrow, which is mainly fat. The red marrow produces billions of blood cells a day. As a person ages, red marrow is converted to yellow marrow, although in an emergency situation where a large quantity of blood needs to be replaced, yellow marrow can be converted back to red marrow. The newly formed blood cells enter the bloodstream through blood vessels extending into the marrow. The marrow also produces osteoblasts and osteoclasts, cells that build up and destroy bone respectively.

Topic Today

Recently bone marrow transplants have become possible, although the procedure is risky and currently is only used for patients with life-threatening conditions. Donor bone marrow is taken from the donor’s pelvic bones under anesthesia, in a procedure called a bone marrow harvest. Recovery from bone marrow donation takes about three weeks on average. Bone marrow transplants can be autologous, when stem cells are removed from a person’s marrow and then frozen to be kept until the original donor needs it for a transplant, or allogenic, when bone marrow cells are taken from another person, often someone closely related to the patient, whose cells would be compatible. The first bone marrow transplant from an unrelated donor took place in 1979. Less developed stem cells can also be recovered from blood in the umbilical cord during birth. In the United States, there is a national bone marrow registry, called Be the Match, designed to find compatible cells for patients if no close relative is available. Be the Match is operated by the National Marrow Donor Program, a nonprofit agency founded in 1986 and located in Minneapolis. Other countries have similar programs. Bone Marrow Donors Worldwide, located in Leiden, Netherlands, coordinates matches and donations from national programs on a global basis. Many donor–recipient relationships take place across national lines.

As preparation for a bone marrow transplant, the cells in the existing bone marrow are killed via chemotherapy or radiation treatments. This suppresses the immune system long enough for the foreign cells to be adopted into the body but also renders the patient vulnerable to numerous infections due to his or her weakened immunity. The transplant itself is not invasive but relies on injecting the new cells into the blood. The new marrow is vulnerable to infection and rejection and full recovery can take as long as a year.

There is an alternative procedure in which drugs are administered that move stem cells into the bloodstream before they are fully transformed into specialized blood cells They are then removed from the donor's blood. German researchers have recently developed an artificial bone marrow, which in the future may serve as a source of stem cells and eliminate the need for stem cell donors.

The scientific and medical uses of stem cells are expanding rapidly, and marrow is the major source of adult stem cells in the human body. Adult stem cells are particularly popular because they do not raise the religious and ethical issues of stem cells derived from fetal tissue. Stem cells are extracted from marrow for research and other uses by drilling into the bone, usually the pelvis, in a procedure similar to that used for marrow donation. Stem cells offer the possibility of treatments for cell-based diseases by creating replacement cells. There have even been some experiments with the transformation of bone marrow stem cells into sperm, which has led to speculation about two women becoming genetic parents together. However, researchers are not close to actually producing a human child with bone marrow stem cell sperm.

Bibliography

Anton, Joseph H., and Deborah Yolin Raley. Manual of Stem Cell and Bone Marrow Transplantation. Cambridge: Cambridge UP, 2013. Print.

Cherry, Daniel A. Bone Marrow: A Practical Manual. N. p.: CRC, 2011. Print.

Gatter, Kevin, and David Brown. Bone Marrow Diagnosis: An Illustrated Guide. Chichester: Wiley, 2014. Print.

Hoffman, Ronald, et al. Hematology: Basic Principles and Practice. Philadelphia: Elsevier Saunders, 2013. Print.

Islam, Anwarul. Manual of Bone Marrow Examination. Bloomington: Trafford, 2013. Print.

Moulopoulos, Lia Angela, and Vassilis Koutoulidis. Bone Marrow MRI: A Pattern-Based Approach. New York: Springer, 2014. Print.

Passweg, J. R., et al. "European Society for Blood and Marrow Transplantation EBMT. Hematopoietic SCT in Europe: Data and Trends in 2012 with Special Consideration of Pediatric Transplantation." Bone Marrow Transplant 49 (2014): 744–50. Print.

Stewart, Susan. Bone Marrow and Blood Stem Cell Transplants: A Guide for Patients. BMT Infonet.org. 6 June 2015. Web. 30 Dec. 2015. http://www.bmtinfonet.org/books/transplants-2012.