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Stem Cell Glossary
Sources: National Institutes of Health and International Society for Stem Cell Research
Adult Stem Cells
Stem cells found in different tissues of the developed adult.
These stem cells can give rise to specialized cell types of the tissue from which they came, i.e., a heart stem cell can give rise to
a functional heart muscle cell.
Blastocyst
A very early embryo consisting of approximately 150 cells. The
blastocyst is a spherical cell mass produced by cleavage of the
zygote (fertilized egg). It contains a fluid-filled cavity (blastocoel), a cluster of cells called the inner cell mass (from which
embryonic stem cells are derived) and another layer of cells
called the trophoblast (that forms the placenta).
Cell-Based Therapies
Treatment in which stem cells are induced to differentiate into
the specific cell type required to repair damaged or destroyed
cells.
Cell Culture
The practice of growing and maintaining cells in a controlled environment under specific conditions for experimental research.
Cell Division
Method by which a single cell divides to create two cells. There
are two main types of cell division: mitosis and meiosis.
Cell Type
A specific subset of cells within the body, defined by their appearance, location, and function.
Clone
To generate identical copies of a cell or organism. When used to
refer to cells grown in a tissue culture dish, a clone is a population of identical cells that create a cell line. This cloned cell line
is produced by cell division (mitosis) of the original cell.
Colony
A cluster or group of cells. Stem cells grow in colonies since
they are unable to survive as single cells. When passaging stem
cells, scientists must break up the colonies into smaller pieces in
order for them to continue to grow. If colonies are broken into
single cells they will be unable to survive.
Culture Medium
The liquid that covers cells in a culture dish that contains nutrients to feed the cells. Medium may also include other growth
factors added to produce desired changes in the cells. Cells
need to be fed because they consume the nutrients and release
metabolic waste into the culture medium. Stem cells require
special attention and must be fed with fresh medium daily.
Directed Differentiation
Directed differentiation is a step by step process by which
scientists manipulate and guide human pluripotent stem cells
to become a specific group of specialized cells. This is accomplished by controlling the environment, modifying the culture
conditions and addition or omission of growth factors.
DNA
Deoxyribonucleic acid, a chemical found primarily in the nucleus
of cells. DNA carries the genetic instructions for making all the
structures and materials the body needs to function.
Ectoderm
The outer of three germ layers of the early embryo. The ectoderm gives rise to the skin, nervous system, enamel of the
teeth, lens of the eye, sensory organs, 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
then called a fetus.
Embryoid Bodies
Spherical colonies seen in culture produced by the growth of
embryonic stem cells in suspension. Embryoid bodies are of
mixed cell types, and the distribution and timing of the appearance of specific cell types corresponds to that observed within
the embryo.
Endoderm
The inner of three germ layers of the early embryo that gives
rise in later development to tissues such as the lungs, intestine,
liver, and pancreas.
Feeder Layer
Cells used in co-culture to maintain pluripotent stem cells. For
human embryonic stem cell cultures, typical feeder layers include mouse embryonic fibroblasts (MEFs) or human embryonic
fibroblasts. Feeder layer cells are treated to prevent them from
dividing when in co-culture with stem cells.
Gene
A segment of DNA found on chromosomes in the nucleus of
a cell. Genes are the functional unit of heredity and direct the
formation of an enzyme or other protein.
Germ Layers
Fertilization of an egg stimulates cell division, and the resulting
cells are organized into three different layers, called germ layers. The three layers are the ectoderm, the mesoderm, and the
endoderm.
Karyotype
The number and appearance of chromosomes in the nucleus
of a cell when observed under a microscope . The preparation and study of karyotypes falls under the scientific branch
of Cytogenetics. This field plays an important role in research
and medicine because it allows the scientists to study genetic
patterns, developmental defects and effects of toxins on cells.
Scientists working with human pluripotent stem cells have to
test and evaluate the karyotypes of their cells on a regular basis
since abnormal cells cannot be used in research.
Mesenchymal Stem Cell
Also known as bone marrow stromal cells, mesenchymal stem
cells are rare cells, mainly found in the bone marrow, that can
give rise to a large number of tissue types such as bone, cartilage, fat tissue, and connective tissue.
Hematopoietic Stem Cell
A stem cell that gives rise to all red and white blood cells and
platelets.
Mesoderm
The middle of three germ layers that gives rise in later development to such tissues as muscle, bone, blood, connective tissue,
and kidneys.
Human Embryonic Stem Cell (hES cell or hESC)
The cells derived from the inner cell mass of a developing
blastocyst. An hES cell is self-renewing (can replicate itself),
pluripotent (can form all cell types found in the body), and theoretically immortal.
Microenvironment
The molecules and compounds (such as nutrients and growth
factors) in the fluid surrounding a cell in an organism or in the
laboratory. The microenvironment plays an important role in
determining the characteristics of a cell.
Human Induced Pluripotent Stem (iPS) Cell
A type of pluripotent stem cell, similar to a human embryonic
stem cell, induced by the introduction of certain embryonic
genes into a somatic cell.
Mitosis
Cell division that allows a population of cells to increase or
maintain its numbers.
Inner Cell Mass (ICM)
A small group of cells attached to the wall of the blastocyst (the
embryo at the very early stage of development that looks like
a hollow ball). Embryonic stem cells are made by isolating and
culturing the cells that make up the inner cell mass. In development, the inner cell mass eventually gives rise to all the organs
and tissues of the future embryo and fetus, but does not give
rise to extra-embryonic tissues, such as the placenta.
In vitro
Latin for “in glass;” in a laboratory dish or test tube; in an artificial environment.
In vitro Fertilization (IVF)
A technique that unites the egg and sperm in a clinical laboratory, instead of inside the female body.
Morphology
The study of the shape and visual appearance of cells, tissues
and organs.
Multipotent
The ability of a single stem cell to develop into more that one
cell type in the body. Multipotent stem cells can generate multiple differentiated cell types, but all within a particular tissue,
organ, or physiological system.
For example, blood-forming (hematopoietic) stem cells are
single multipotent cells that can produce all cell types that are
normal components of the blood.
Passage
A round of cell growth and proliferation in cell culture. When
passaging, scientists will use an enzyme to remove the cells
from the surface of a culture plate. They will then break the
colonies into smaller pieces and place them into a new culture
plate where they will be able to attach and continue to grow.
Pluripotent
The ability of a single stem cell to give rise to all of the various
cell types that make up the body. Pluripotent cells have the
ability to become any of the three major tissue types (germ layers) in the body, but they cannot make up the so-called “extraembryonic” tissues such as the amnion, chorion, and other
components of the placenta.
Pre-implantation Embryo
A fertilized egg (zygote) and all of the developmental stages up
to, but not beyond the blastocyst stage.
Progenitor cells
Progenitor cells are early descendants of stem cells. Unlike
stem cells, they have a limited ability to multiply or renew themselves before they become a specialized group of cells and acquire a specific function in the body. Progenitor cells are known
as multipotent or oligopotent cells since they can multiply and
proceed down a specific lineage or pathway. For example, progenitor cells in the blood/bone marrow lineage can give rise to a
variety of blood cells but not nerve cells or kidney cells.
Proliferation
Expansion of cells by the continuous division of single cells into
two identical daughter cells.
Regenerative Medicine
A treatment in which stem cells are induced to differentiate into
the specific cell type required to repair damaged or destroyed
cell populations or tissues.
See also Cell-Based Therapies.
Reproductive Cloning
The goal of reproductive cloning is to create an animal being
identical to the animal that donated the somatic cell nucleus.
The embryo is implanted in a uterus and develops into a live
being.
The first animal to be created by reproductive cloning was Dolly
the sheep, born at the Roslin Institute in Scotland in 1996.
See also Therapeutic Cloning.
Signals
Internal and external factors that control changes in cell structure and function.
Stem Cells
Cells with the ability to divide for indefinite periods in culture
and to give rise to specialized cells.
Teratoma
Scientists verify that they have established a pluripotent stem
cell line by injecting these stem cells into mice with a dysfunctional immune system. Since the injected cells cannot be destroyed by the mouse’s immune system, they survive and form
a multi-layered benign tumor called a teratoma. In this test, the
teratomas serve to establish the ability of a stem cell to give rise
to all cell types in the body.
Therapeutic Cloning
The goal of therapeutic cloning is to create cells that exactly
match a patient. By combining a patient’s somatic cell nucleus
and an egg cell with its nucleus removed, a scientist may harvest
embryonic stem cells from the resulting embryo that can be
used to generate tissues that match the patient’s body. This
means that tissues created are unlikely to be rejected by the
patient’s immune system.
Totipotent
A totipotent stem cell can give rise to all the cell types that
make up the body, plus all of the cell types that make up the
extra-embryonic tissues such as the placenta.
See also Pluripotent and Multipotent.
Transdifferentiation
The process by which stem cells from one tissue differentiate
into cells of another tissue.
Trophoblast
The tissue of the developing embryo responsible for implantation and formation of the placenta. In contrast to embryonic
stem cells, the trophoblast does not come from the inner cell
mass, but from the cells surrounding it.
Umbilical Cord Stem Cells
Stem cells collected from the umbilical cord at birth that can
produce all of the blood cells in the body. Umbilical cord stem
cells are similar to stem cells that reside in bone marrow, and
cord blood is currently used to treat patients who have undergone chemotherapy to destroy their bone marrow due to cancer
or other blood-related disorders.
Efforts are being undertaken to collect umbilical cord cells and
store them in freezers for later use. However, one problem is
that there may not be enough umbilical cord stem cells in any
one sample to transplant into an adult patient.
Undifferentiated Cell
A cell that is unspecialized and has not acquired a specific funtion in the human body.
Additional Resources:
Learn more about stem cells by visiting these online resources:
WiCell Research Institute
http://www.wicell.org
National Institutes of Health (NIH)
http://stemcells.nih.gov
International Society for Stem Cell Research (ISSCR)
http://www.isscr.org
University of Wisconsin-Madison
http://www.stemcells.wisc.edu/
University of Michigan
http://www.umich.edu/stemcell/
The Harvard Stem Cell Institute
http://www.hsci.harvard.edu/
Children’s Hospital Boston
http://www.childrenshospital.org/research
University of Utah
http://learn.genetics.utah.edu/
University of California, San Francisco
http://irm.ucsf.edu/
Northwest Association for Biomedical Research
www.nwabr.org/education/stemcellforum.htm
Pittsburg Development Center
http://www.pdc.magee.edu/outreach.htm
University of California, Irvine
http://stemcell.uci.edu/index.cfm