Stem cells Stem cells are ‘generic’ cells that develop into particular types of cells. So they may become nerve cells, muscle cells, blood cells… in fact, any cell in the body! Stem cells divide over and over to produce new cells. Photo information: Stem cells can differentiate into any other cell type. There are three main types of mammalian stem cell: embryonic stem cells, derived from blastocysts; adult stem cells, which are found in some adult tissues; and cord blood stem cells, which are found in the umbilical cord. The cell seen here is destined to become a blood cell. During blood cell development in adults, stem cells develop through a process known as haemopoiesis. Blood cells have short lifespans and are therefore constantly produced by the bone marrow.

Stem cells, bone marrow and blood cells One of the main places you find stem cells is in bone marrow. Stem cells in bone marrow produce new blood cells to replace those that have died. When the cells are mature they are released into the bloodstream. A ‘bone marrow’ donation is really a donation of stem cells. Bone marrow is found in the cavities inside the long and flat bones of the body. Questions you may like to ask (if already studied the blood and its parts) : Q. Which blood cells do you think stem cells in bone marrow produce? A. White blood cells, red blood cells, platelets. Q. What do these blood cells do? A. White blood cells fight infection; red blood cells carry oxygen around the body; platelets help blood clot when you cut yourself. Photo information: Bone marrow is the site of blood cell production. Differentiating white blood cells (yellow), part of the body's immune system, and red blood cells (red), which carry oxygen around the body, are seen amongst reticular fibres (cream). Reticular fibres make up the connective tissue framework of the bone marrow. Compact (or cortical) bone, which forms the hardened perimeter that contains the marrow, is seen at top. Magnification: x500 when printed 10 centimetres wide.

Leukaemia Leukaemia is a form of cancer. In the most common forms of leukaemia, one abnormal white blood cell continuously replicates (clones) itself. These abnormal white blood cells do not function properly: They do not fight infections They inhibit the production of other blood cells and platelets For some people, a bone marrow transplant can be a life-saver. Question you may like to ask about leukaemia (if already studied the blood and its parts): Q. Given what you know about leukaemia and the role of the different blood cells, what do you think may be some symptoms of this cancer? A. Because the abnormal white blood cells: - do not function properly and inhibit production of healthy white blood cells – more infections; - inhibit the production of red blood cells – looking pale, feeling tired and breathless - inhibit the production of platelets – unusual bleeding, e.g. bleeding gums, frequent nosebleeds

Transplants save lives Bone marrow transplants not only save the lives of leukaemia patients. They can also save the lives of those suffering from: illnesses where the immune system does not function properly such as aplastic anaemia (where the bone marrow stops making enough blood cells) rare genetic diseases such as osteopetrosis (where bones harden and become dense and bone marrow does not develop properly) all kinds of cancers (where healthy stem cells have been damaged during treatments to destroy cancer cells)

Stem cell (“bone marrow”) donation There are three ways to collect stem cells from a donor: Bone marrow A donor has a small operation under general anesthetic. Circulating blood A donor’s circulating stem cells are boosted with a special drug. Then they are connected to a cell separator machine, which collects the stem cells and returns the rest of the blood to the donor. Cord blood Selected hospitals offer new mothers the chance to donate the blood that remains in the placenta and umbilical cord after their baby’s birth.

Advantages / disadvantages for patients Cord blood: hasn’t been exposed to environment so less likely to contain viral infection; requires less stringent matching; once collected is banked and can be readily available at short notice. Bone marrow and circulating blood: tend to have a greater number of stem cells in the donation, so tend to be accepted into the patient’s body more quickly. Disadvantages tends to have less stem cells in the donation. finding a match and arranging a donation can take weeks, or months (this is time the patient may not have).

Finding a match A bone marrow donor needs to be a close ‘tissue type’ match with the recipient You can tell what someone’s tissue type by testing their blood Tissue type is inherited but only 30% of donors are found from within a patient’s family Patients are most likely to find a match from within their own ethnic community So donors from all ethnic backgrounds are needed