There are several ways adult stem cells can be isolated, most of which are being actively explored by our researchers.
1) From the body itself:
Scientists are discovering that many tissues and organs contain a small number of adult stem cells that help maintain them. Adult stem cells have been found in the brain, bone marrow, blood vessels, skeletal muscle, skin, teeth, heart, gut, liver, and other (although not all) organs and tissues. They are thought to live in a specific area of each tissue, where they may remain dormant for years, dividing and creating new cells only when they are activated by tissue injury, disease or anything else that makes the body need more cells.
Adult stem cells can be isolated from the body in different ways, depending on the tissue. Blood stem cells, for example, can be taken from a donor’s bone marrow, from blood in the umbilical cord when a baby is born, or from a person’s circulating blood. Mesenchymal stem cells, which can make bone, cartilage, fat, fibrous connective tissue, and cells that support the formation of blood can also be isolated from bone marrow. Neural stem cells (which form the brain’s three major cell types) have been isolated from the brain and spinal cord. Research teams at Children’s, headed by leading scientists Stuart Orkin, MD and William Pu, MD, both affiliate members of the Stem Cell Program, recently isolated cardiac stem cells from the heart.
Isolating adult stem cells, however, is just the first step. The cells then need to be grown to large enough numbers to be useful for treatment purposes. The laboratory of Leonard Zon, MD, director of the Stem Cell Program, has developed a technique for boosting numbers of blood stem cells that’s now in Phase I clinical testing.
2) From amniotic fluid:
Amniotic fluid, which bathes the fetus in the womb, contains fetal cells including mesenchymal stem cells, which are able to make a variety of tissues. Many pregnant women elect to have amniotic fluid drawn to test for chromosome defects, the procedure known as amniocentesis. This fluid is normally discarded after testing, but Children’s Hospital Boston surgeon Dario Fauza, MD, a Principal Investigator at Childrens and an affiliate member of the Stem Cell Program, has been investigating the idea of isolating mesenchymal stem cells and using them to grow new tissues for babies who have birth defects detected while they are still in the womb, such as congenital diaphragmatic hernia. These tissues would match the baby genetically, so would not be rejected by the immune system, and could be implanted either in utero or after the baby is born.
3) From pluripotent stem cells:
Because embryonic stem cells and induced pluripotent cells (iPS cells), which are functionally similar, are able to create all types of cells and tissues, scientists at Children’s and elsewhere hope to use them to produce many different kinds of adult stem cells. Laboratories around the world are testing different chemical and mechanical factors that might prod embryonic stem cells or iPS cells into forming a particular kind of adult stem cell. Adult stem cells made in this fashion would potentially match the patient genetically, eliminating both the problem of tissue rejection and the need for toxic therapies to suppress the immune system.
4) From other adult stem cells:
A number of research groups have reported that certain kinds of adult stem cells can transform, or differentiate, into apparently unrelated cell types (such as brain stem cells that differentiate into blood cells or blood-forming cells that differentiate into cardiac muscle cells). This phenomenon, called transdifferentiation, has been reported in some animals. However, it’s still far from clear how versatile adult stem cells really are, whether transdifferentiation can occur in human cells, or whether it could be made to happen reliably in the lab.