Words and phrases commonly used in stem cell research

The Cell Therapy and Regenerative Medicine Glossary provides a further guide to terminology used in regenerative medicine.


Ancestor cell

General term for cell without self-renewal ability that contributes to tissue formation. In some cases it generates tissue stem cells. Synonyms: precursor cell.

Asymmetric division

Cell division resulting in two daughter cells with different properties. Observed in some but not all stem cells and can occur in other types of progenitor cell.

Autologous cell therapy

A therapy using cells derived from a patient’s own body. This often involves the extraction of cells and an ‘ex vivo’ (outside the body) step of growing and multiplying them before transplanting them back into the patient.

Allogeneic cell therapy

A therapy using cells derived from a donor to treat a different patient. Often intended to become an ‘off the shelf’ cell therapy product which uses cells derived from a single donor to treat many unrelated patients.


An early stage embryo of about 100 cells that has not yet implanted into the womb. The blastocyst is a sphere made up of an outer layer of cells, a fluid-filled cavity and cluster of cells inside called the inner cell mass.

Cancer cell of origin

Precancerous cell that gives rise to a cancer stem cell. May be a mutated stem cell, or a progenitor cell that has acquired self-renewal capacity through mutation.

Cancer stem cell

Self-renewing cell responsible for sustaining a cancer and for producing differentiated progeny that form the bulk of the cancer. Cancer stem cells identified in leukaemias and certain solid tumours are critical therapeutic targets.  See also: Cancer: a disease of stem cells? (factsheet)

Cancer-initiating cell

Cell that can produce a new cancer upon transplantation. A key property of a cancer stem cell.

Cell culture

The growth of cells in a laboratory dish for experimental research. The cells are grown in a solution, or medium, that contains nutrients and growth factors. Different factors can be added to the culture medium to initiate changes in cell behaviour.

Cell line

A population of cells all carrying the same genes, grown in the laboratory through many cycles of growth and division over many generations of cells.

Cell replacement therapy

Reconstitution of tissue by functional incorporation of transplanted stem-cell progeny. Distinct from ‘bystander’ trophic, anti-inflammatory or immunomodulatory effects of introduced cells.

Clinical translation

The process of turning scientific knowledge into approved medical treatments, through a series of carefully controlled research and approval steps. See also: The road to the clinic.

Clinical trial

A research study in human subjects to answer specific questions about vaccines or new therapies or new ways of using known treatments. Clinical trials are used to determine whether new drugs or treatments are both safe and effective. Trials take place in four phases: Phase I tests a new drug or treatment in a small group; Phase II expands the study to a larger group of people; Phase III expands the study to an even larger group of people; and Phase IV takes place after the drug or treatment has been licensed and marketed.  See also: clinical trials FAQ, clinical trials and stem cell treatments topic page.

Clonal analysis

Investigation of properties of single cells. Essential for formal demonstration of self-renewal and potency.


Engagement in a programme leading to differentiation. For a stem cell, this means it no longer retains the ability to self-renew.

Daughter cell

One of the two or more cells formed in the division of a single cell.


The process by which cells become specialized to perform particular tasks.

Embryonic stem cell

Pluripotent stem-cell lines derived from early embryos before formation of the tissue germ layers.  See also: Embryonic stem cells: where do they come from and what can they do? (factsheet)


Epigenetics explores how genetically identical entities, whether cells or whole organisms, display different characteristics, and how these are inherited.


A type of tissue that lines cavities and surfaces in the body. Examples include the cornea of the eye, the layers of the skin and the lining of the lungs. Epithelial tissues can also form glands. In Greek, ‘epi’ means ‘on, upon’ and ‘theli’ means ‘tissue’.

Germ cells

The reproductive cells in multicellular organisms.

Hematopoietic stem cells

Stem cells that give rise to all the blood cell types.


The functional cell type of the liver. Hepatocytes make enzymes for detoxifying metabolic waste, synthesise proteins for the blood plasma, produce bile and help control blood sugar levels within narrow limits.

Immortal strand

The hypothesis of selective retention of parental DNA strands during asymmetric self-renewal. Potential mechanism to protect stem cells from the mutations associated with replication.

Induced pluripotent stem (iPS) cells

A type of pluripotent stem cell derived from a non-pluripotent cell, typically an adult somatic cell, by manipulating expression of certain genes. Read our fact sheet on iPS cells.


Term used to describe cells with a common ancestry, that is developing from the same type of identifiable immature cell.

Long-term reconstitution

Lifelong renewal of tissue by transplanted cells. The definitive test for haematopoietic, epidermal and spermatogonial stem cells.


A type of white blood cell and a versatile part of the immune system. Constantly on patrol, macrophages can find and kill many different kinds of bacteria. They are usually the first responders to any invasion of the body.


Able form multiple mature cell types that constitute an entire tissue or tissues. Example: haematopoietic (blood) stem cells.


Cellular micro-environment providing the support and stimuli necessary to sustain self-renewal.


Able to form two or more mature cell types within a tissue. For example, neural stem cells that can create a subset of neurons in the brain are oligopotent.


Unproven notion that tissue stem cells may be able to generate the cell types of another tissue under certain conditions.


Able to form all the body’s cell lineages, including germ cells, and some or even all extraembryonic cell types. Example: embryonic stem cells.


The range of commitment options available to a cell.

Progenitor cell

Generic term for any dividing cell with the capacity to give rise to another cell type. Includes possible stem cells in which self-renewal has not yet been demonstrated.

Regenerative medicine

Reconstruction of diseased or injured tissue by activation of resident cells or by cell transplantation.


Increase in potency. Occurs naturally in regenerative organisms (dedifferentiation). Induced experimentally in mammalian cells by nuclear transfer, cell fusion, genetic manipulation or in vitro culture.  See our factsheet on reprogramming.


The ability of a stem cell to divide and produce copies of itself for an indefinite period of time. This is the defining property of stem cells.

Somatic cell

Any of the cells of a plant or animal other than germ cells (reproductive cells)

Stem cell

A cell that can continuously produce unaltered daughters and also has the ability to produce daughter cells that have different, more restricted properties. See also: An introduction to stem cells FAQ


Unproven notion that different stem cells are regulated by common genes and mechanisms.

Therapeutic cloning

The process of producing embryonic stem cells from an adult cell taken from a patient. This is done using a technique called somatic cell nuclear transfer (SCNT).  See also: our short film on cloning, Dolly & beyond.

Tissue stem cell

Stem cell derived from, or resident in, a fetal or adult tissue, with potency limited to cells of that tissue. These cells sustain turnover and repair throughout life in some tissues. Synonyms: adult stem cell.


Sufficient to form entire organism. The zygote is totipotent; not demonstrated for any vertebrate stem cell.

Transcription factor

A protein that binds to specific sequences of DNA and thereby activates or represses the production of messenger RNA (known as ‘transcription’ of DNA to RNA). Messenger RNA carries the code for the production of new proteins.


Forms a single mature cell type. For example, spermatogonial stem cells are unipotent, as they can only form sperm cells.


A single cell resulting from the fusion of male and female gametes (sperm and egg) at fertilization.