Adult 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.
Axon: A long, slender projection of a nerve cell or neuron that conducts electrical impulses away from the neuron’s cell body.
Blastocyst: An early stage of human development, comprising 50 to 100 cells; the structure found in early pregnancy before implantation.
Differentiation: The process whereby an undifferentiated embryonic cell acquires the features of a specialized cell such as a heart or muscle cell.
DNA, or deoxyribonucleic acid: The substance found in the nucleus of cells. It contains the genetic instructions for the development and functioning of all living organisms.
Embryo: In humans, the developing organism from the time of fertilization until the end of the eighth week of gestation, after which it is referred to as a fetus.
Embryonic germ cells: Pluripotent stem cells derived from early germ cells.
Germ layers: The resulting cells after an egg is fertilized compose three different layers, or germ layers.
Multipotent: The ability of a stem cell to develop into more than one cell type of the body, but not all of them.
Nano-gel: A nano-engineered material containing molecules programmed to come together into nano-structures. When exposed to living tissues, it triggers the self-assembly of the molecules and is transformed into a gel. When the gel is injected, it then self-assembles into a scaffold that will allow axons to grow down the spinal cord.
Nanoengineering: The practice of engineering in the field of nanotechnology, or the control of matter on the molecular level in scales smaller than one billionth of a meter.
Neurons: Composed of a cell body and its processes—an axon and one or more dendrites—these nerve cells function by transmitting impulses to other neurons or cells.
Pluripotent: The ability of a stem cell to develop into the various cell types that make up the body.
Reproductive cloning: This type of cloning creates animals that are genetically identical. Using somatic cell nuclear transfer, one animal donates a somatic cell nucleus that divides and is transferred into the uterus of a surrogate mother. The first animal successfully created by reproductive cloning was Dolly the sheep, in 1996.
Somatic cell nuclear transfer (SCNT): The process in which the nucleus from an adult cell is removed and then transferred to an egg whose nucleus has been removed. This is the first step in both reproductive and therapeutic cloning.
Therapeutic cloning: The goal of therapeutic cloning is to create cells that exactly match a patient’s. A cell produced through SCNT is then allowed to divide until it forms a blastocyst, which then can be used to create an embryonic stem cell line that matches a patient’s DNA and produce cells for medical purposes.
Totipotent: The ability of a stem cell to develop into all the cell types that make up the body plus all of the cell types that make up the extraembryonic tissues.
Umbilical cord blood stem cells: These stem cells are collected from the umbilical cord at birth and can produce all of the blood cells in the body. Cord blood is used to treat patients whose bone marrow is destroyed due to cancer or other blood-related diseases.
Undifferentiated cell: A cell that has not yet generated structures or manufactured proteins characteristic of a specialized cell type.