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Stem Cell Glossary

Stem cell terms to know

Stem cell science involves many technical terms. This glossary covers many of the common terms you will encounter in reading about stem cells.

Adult stem cells
A commonly used term for tissue-specific stem cells, cells that can give rise to the specialized cells in specific tissues. Includes all stem cells other than pluripotent stem cells such as embryonic and induced pluripotent stem cells. 

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Autologous
Cells or tissues from the same individual; an autologous bone marrow transplant involves one individual as both donor and recipient.

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Basic research
Research designed to increase knowledge and understanding (as opposed to research designed with the primary goal to solve a problem).

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Blastocyst
A transient, hollow ball of 150 to 200 cells formed in early embryonic development that contains the inner cell mass, from which the embryo develops, and an outer layer of cell called the trophoblast, which forms the placenta.

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Bone marrow stromal cells
A general term for non-blood cells in the bone marrow, such as fibroblasts, adipocytes (fat cells) and bone- and cartilage-forming cells that provide support for blood cells. Contained within this population of cells are multipotent bone marrow stromal stem cells that can self-renew and give rise to bone, cartilage, adipocytes and fibroblasts. 

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Cardiomyocytes
The functional muscle cells of the heart that allow it to beat continuously and rhythmically.

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Clinical translation
The process of using scientific knowledge to design, develop and apply new ways to diagnose, stop or fix what goes wrong in a particular disease or injury; the process by which basic scientific research becomes medicine.

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Clinical trial
Tests on human subjects designed to evaluate the safety and/or effectiveness of new medical treatments.

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Cord blood
The blood in the umbilical cord and placenta after child birth. Cord blood contains hematopoietic stem cells, also known as cord blood stem cells, which can regenerate the blood and immune system and can be used to treat some blood disorders such as leukemia or anemia. Cord blood can be stored long-term in blood banks for either public or private use. Also called umbilical cord blood.

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Cytoplasm
Fluid inside a cell, but outside the nucleus.

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Differentiation
The process by which cells become increasingly specialized to carry out specific functions in tissues and organs.

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Drug discovery
The systematic process of discovering new drugs.

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Drug screening
The process of testing large numbers of potential drug candidates for activity, function and/or toxicity in defined assays.

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Embryo
Generally used to describe the stage of development between fertilization and the fetal stage; the embryonic stage ends 7-8 weeks after fertilization in humans.

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Embryonic stem cells (ESCs)
Undifferentiated cells derived from the inner cell mass of the blastocyst; these cells have the potential to give rise to all cell types in the fully formed organism and undergo self-renewal.

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Fibroblast
A common connective or support cell found within most tissues of the body.

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Glucose
A simple sugar that cells use for energy.

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Hematopoietic
Blood-forming; hematopoietic stem cells give rise to all the cell types in the blood.

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Immunomodulatory
The ability to modify the immune system or an immune response.

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Induced pluripotent stem cells (iPSCs)
Embryonic-like stem cells that are derived from reprogrammed, adult cells, such as skin cells. Like ESCs, iPS cells are pluripotent and can self-renew.

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In vitro
Latin for “in glass.” In biomedical research this refers to experiments that are done outside the body in an artificial environment, such as the study of isolated cells in controlled laboratory conditions (also known as cell culture).

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In vivo
Latin for “within the living.” In biomedical research this refers to experiments that are done in a living organism. Experiments in model systems such as mice or fruit flies are an example of in vivo research.

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Islets of Langerhans
Clusters in the pancreas where insulin-producing beta cells live.

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Macula
A small spot at the back of the retina, densely packed with the rods and cones that receive light, which is responsible for high-resolution central vision.

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Mesenchymal stem cells (MSCs)
A term used to describe cells isolated from the connective tissue that surrounds other tissues and organs. MSCs were first isolated from the bone marrow and shown to be capable of making bone, cartilage and fat cells. MSCs are now grown from other tissues, such as fat and cord blood. Not all MSCs are the same and their characteristics depend on where in the body they come from and how they are isolated and grown. May also be called mesenchymal stromal cells.

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Multipotent stem cells
Stem cells that can give rise to several different types of specialized cells in specific tissues; for example, blood stem cells can produce the different types of cells that make up the blood, but not the cells of other organs such as the liver or the brain.

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Neuron
An electrically excitable cell that processes and transmits information through electrical and chemical signals in the central and peripheral nervous systems.

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Pancreatic beta cells
Cells responsible for making and releasing insulin, the hormone responsible for regulating blood sugar levels. Type I diabetes occurs when these cells are attacked and destroyed by the body's immune system.

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Photoreceptors
Rod or cone cells in the retina that receive light and send signals to the optic nerve, which passes along these signals to the brain.

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Placebo
A pill, injection or other treatment that has no therapeutic benefit; often used as a control in clinical trials to see whether new treatments work better than no treatment.

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Placebo effect
Perceived or actual improvement in symptoms that cannot be attributed to the placebo itself and therefore must be the result of the patient's (or other interested person's) belief in the treatment's effectiveness.

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Pluripotent stem cells
Stem cells that can become all the cell types that are found in an embryo, fetus or adult, such as embryonic stem cells or induced pluripotent (iPS) cells.

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Preclinical research
Laboratory research on cells, tissues and/or animals for the purpose of discovering new drugs or therapies.

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Precursor cells
An intermediate cell type between stem cells and differentiated cells. Precursor cells have the potential to give rise to a limited number or type of specialized cells. Also called progenitor cells. 

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Progenitor cells
An intermediate cell type between stem cells and differentiated cells. Progenitor cells have the potential to give rise to a limited number or type of specialized cells and have a reduced capacity for self-renewal. Also called precursor cells. 

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Regenerative Medicine
An interdisciplinary branch of medicine with the goal of replacing, regenerating or repairing damaged tissue to restore normal function. Regenerative treatments can include cellular therapy, gene therapy and tissue engineering approaches.

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Reprogramming
In the context of stem cell biology, this refers to the conversion of differentiated cells, such as fibroblasts, into embryonic-like iPS cells by artificially altering the expression of key genes.

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Retinal pigment epithelium
A single-cell layer behind the rods and cones in the retina that provide support functions for the rods and cones.

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RNA
Ribonucleic acid; it "reads" DNA and acts as a messenger for carrying out genetic instructions. 

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Scientific method
A systematic process designed to understand a specific observation through the collection of measurable, empirical evidence; emphasis on measurable and repeatable experiments and results that test a specific hypothesis.

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Self-renewal
A special type of cell division in stem cells by which they make copies of themselves.

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Somatic stem cells
Scientific term for tissue-specific or adult stem cells.

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Stem cells
Cells that have both the capacity to self-renew (make more stem cells by cell division) and to differentiate into mature, specialized cells.

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Stem cell tourism
The travel to another state, region or country specifically for the purpose of undergoing a stem cell treatment available at that location. This phrase is also used to refer to the pursuit of untested and unregulated stem cell treatments. 

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Teratoma
 
A benign tumor that usually consists of several types of tissue cells that are foreign to the tissue in which the tumor is located.

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Tissue
A group of cells with a similar function or embryological origin. Tissues organize further to become organs.

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Tissue-specific stem cells
Stem cells that can give rise to the specialized cells in specific tissues; blood stem cells, for example, can produce the different types of cells that make up the blood, but not the cells of other organs such as the liver or the brain. Includes all stem cells other than pluripotent stem cells such as embryonic and induced pluripotent cells. Also called adult or somatic stem cells.

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Totipotent
The ability to give rise to all the cells of the body and cells that aren’t part of the body but support embryonic development, such as the placenta and umbilical cord.

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Translational research
Research that focuses on how to use knowledge gleaned from basic research to develop new drugs, treatments or therapies.

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Zygote
The single cell formed when a sperm cell fuses with an egg cell.