Stem Cell Glossary

Stem Cell: A cell that can divide to form more stem cells as well as giving rise to specialized cells (blood cells, nerve cells, muscle cells, etc.).

Self-renewal: The ability of a stem cell to divide and give rise to more stem cells with identical properties to the parent cell, thereby allowing the population to be replenished indefinitely.

Differentiation: The process whereby a stem cell loses its capacity for self-renewal and becomes a mature and specialized cell type - for example a blood cell, nerve cell, pancreatic cell, cardiac muscle cell, etc.

Adult stem cells: Stem cells found in mature tissues (bone marrow, skin, brain, etc.) that can self-renew and give rise to other cell types from their tissue of origin, thereby producing a steady supply of new cells to maintain that tissue throughout life. In general, adult stem cells from one organ do not give rise to cell types from other organs.

Cord blood stem cells: Stem cells that are recovered from umbilical cord at the time of birth. These stem cells resemble the stem cells found in adult bone marrow. They are thus more like adult stem cells than embryonic stem cells.

Blastocyst: An early stage embryo, prior to the time of implantation in a uterus. The blastocyst consists of a microscopic cluster of several hundred undifferentiated cells, from which embryonic stem cells can be derived.

Embryonic stem cells: Stem cells that are derived from a blastocyst and which (unlike adult stem cells) can give rise to every cell type in every organ of the body.

Somatic cell nuclear transfer (sometimes known as ‘therapeutic cloning'): A process by which a nucleus from a single cell (for example a skin cell) is transferred into an unfertilized egg, which is then allowed to develop to the blastocyst stage. Embryonic stem cells derived from this blastocyst are genetically identical to the donor of the original nucleus.