Glossary of Stem-Cell Related Terms
Adult stem cells
Stem cells found in different tissues that remain in an undifferentiated, or unspecialized, state. These can give rise to specialized cell types of the tissue from which they came — as, in the bone marrow, stem cells can develop into all the cells of the blood. Adult stem cells also exist in liver, skin, muscle, brain and many other organs.
Differentiation
The process by which early unspecified cells acquire the features of other, specific cells such as muscle, liver or islet cells.
Germ cell
Cells from fetal tissue, specifically from primordial germ cells, which eventually develop into sperm or eggs if the fetus continues to develop. These cells can give rise to all three germ layers in human beings. (The mesoderm layer will form the muscles and connective tissue. The ectoderm layer will form the epidermis. The endoderm layer will form the gut.
Hematopoietic stem cells (HSC)
The HSC are the best understood of the adult stem cells. These cells can be found in bone marrow, umbilical cord blood and adult blood and form all types of cells in the blood: white, red and platelets. Now routinely used to treat patients with cancers and other disorders of the blood and immune system.
Human embryonic stem cell (hESC)
Cells from the “inner cell mass” of a four-to-five day old embryo called a “blastocyst.” These cells, which have the potential to become a wide variety of specialized cell types, can be cultured in the laboratory to make cell lines. These cells are not “cloned cells” because they contain sets of chromosomes that originate from two cells (sperm and egg).
Multipotent
A more specialized stem cell, such as a blood or skin stem cell. Adult stem cells are generally multipotent.
Pluripotent
Capable of giving rise to or developing into most tissues of an organism; hESC are pluripotent.
Reproductive cloning
SCNT also could theoretically be used to create identical individuals by reproductive cloning. In this case, the cloned cell would be placed into a woman’s uterus to produce an offspring genetically identical to the person who donated the nucleus. This process has been performed in some animals but never in humans. This type of cloning is banned.
Somatic cell
A cell that contains two sets of chromosomes and is part of a mature tissue (in contrast to sperm and egg cells that may contain one set of chromosomes).
Somatic cell nuclear transfer (SCNT)
SCNT involves the transfer of a nucleus from a somatic cell (the donor cell) into an embryonic stem cell or egg from which the nucleus has been removed (the recipient cell). The resulting cell contains identical chromosomes to the donor cell – this is called “cloning.” SCNT can be used for therapeutic cloning or reproductive cloning.
Therapeutic cloning
SCNT could be performed using the nucleus of a somatic cell from a patient who needs a new organ or tissue. After SCNT, the cloned embryonic stem cells would be directed in the lab to form the type of tissue needed for transplantation. The new tissue formed by SCNT could be now matched to the patient and so should not be rejected after transplantation.
Primer developed with assistance from Gay Crooks, MD, and Carolyn Lutzko, PhD, along with input from the International Society for Stem Cell Research and the National Institutes of Health.
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