Glossary on stem cells

GLOSSARY

Adult (or somatic) stem cell—An undifferentiated cell found in a differentiated tissue that can renew itself and differentiate (with certain limitations) to give rise to all the specialized cell types of the tissue from which it originated. It is important to note that scientists do not agree about whether or not adult stem cells may give rise to cell types other than those of thetissue from which they originate.
astrocyte—a type of supporting (glial) cell found in the nervous system.
Blastocoel—The fluid-filled cavity inside the blastocyst of the developing embryo.
Blastocyst—A preimplantation embryo of about 150 cells produced by cell division following fertilization. The blastocyst is a sphere made up of an outer layer of cells (the trophoblast), a fluid-filled cavity(the blastocoel), and a cluster of cells on the interior (the inner cell mass).
Bone marrow stromal cells—A mixed population of stem cells found in bone marrow that does not give rise to blood cells but instead generates bone, cartilage, fat, and fibrous connective tissue.
Cell division—Method by which a single cell divides to create two cells. There are two main types of cell division: mitosisand meiosis.
Cell-based therapies—Treatment in which stem cells are induced to differentiate into the specific cell type required to repair damaged or destroyed cells or tissues.
Cell culture—Growth of cells in vitro in an artificial medium for experimental research.
Clone—Generate identical copies of a molecule, cell, or organism.
1. When it is used to refer to cells grown in a tissueculture dish, a clone is a line of cells that is genetically identical to the originating cell. This cloned line is produced by cell division (mitosis) of the originating cell.
2. The term clone may also be used to refer to an animal produced by somatic cell nuclear transfer (SCNT).
Cloning—See Somatic cell nuclear transfer (SCNT).
Cord blood stem cells—See Umbilical cord blood stem cells.Culture medium—The liquid that covers cells in a culture dish and contains nutrients to feed the cells. Medium may also include other growth factors added to produce desired changes in the cells.
Differentiation—The process whereby an undifferentiated embryonic cell acquires the features of a specialized cell such as a heart, liver, or muscle cell.
Directed differentiation—Manipulating stem cellculture conditions to induce differentiation into a particular cell type.
DNA—Deoxyribonucleic acid, a chemical found primarily in the nucleus of cells. DNA carries the instructions or blueprint for making all the structures and materials the body needs to function.
Ectoderm—Outermost germ layer of cells derived from the inner cell mass of the blastocyst; gives rise to the nervous system, sensoryorgans, skin, and related structures.
Embryo—In humans, the developing organism from the time of fertilization until the end of the eighth week of gestation, when it is called a fetus.
Embryoid bodies—Rounded collections of cells that arise when embryonic stem cells are cultured in suspension. Embryoid bodies contain cell types derived from all 3 germ layers.
Embryonic germ cells—Pluripotent stemcells that are derived from early germ cells (those that would become sperm and eggs). Embryonic germ cells (EG cells) are thought to have properties similar to embryonic stem cells.
Embryonic stem cells—Primitive (undifferentiated) cells derived from a 5-day preimplantation embryo that have the potential to become a wide variety of specialized cell types.
Embryonic stem cell line—Embryonicstem cells, which have been cultured under in vitro conditions that allow proliferation without differentiation for months to years.
Endoderm—Innermost layer of the cells derived from the inner cell mass of the blastocyst; it gives rise to lungs, other respiratory structures, and digestive organs, or generally "the gut".
Enucleated— A cell with its nucleus removed.
Feeder layer—Cells used in...