Glossary of Regenerative Medicine-Related Terms

The following is a glossary of some regenerative medicine-related terms that may be useful to the reader. Please click a specific word in the list below or scroll through the alphabetized entries.

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Adult stem cells

Stem cells that are derived from tissues of developed, adult organisms that remain in an undifferentiated, or unspecialized, state. These 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, etc

Allogeneic cells

Being genetically different although belonging to or obtained from the same species, such as cells that are obtained from one human that would be used to treat another person.


Allogeneic transplantation

Cell, tissue or organ transplants from one member of a species to a genetically different member of the same species.


Autologous cells

Derived or transferred from the same individual's body


Autologous transplantation

Cell, tissue or organ transplants from one individual back to the same individual. Such transplants do not produce an immune response and are not rejected by the recipient.



The characteristic of a substance that can be broken down by microorganisms.


Biological substitutes

"Tissue Engineering" is the application of principles and methods of engineering and life sciences toward fundamental understanding of structure-function relationships in normal and pathological mammalian tissues and the development of biological substitutes to restore, maintain, or improve tissue function.



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, a cluster of cells called the inner cell mass (from which embryonic stem cells are derived) and an outer layer of cells called the trophoblast (that forms the placenta).


Bone marrow

The soft blood-forming tissue that fills the cavities of bones and contains fat and immature and mature blood cells, including white blood cells, red blood cells, and platelets.


Bone marrow stromal cell

Also known as mesenchymal stem cells, bone marrow stromal cells are a mixed population of cells derived from the non-blood forming fraction of bone marrow. Bone marrow stromal cells are capable of growth and differentiation into a number of different cell types including bone, cartilage and fat.



A smooth material that covers bone ends of a joint to cushion the bone and allow the joint to move easily without pain.


Cell biology

Cell biology (also called cellular biology) is an academic discipline which studies cells. This includes their physiological properties such as their structure and the organelles they contain, their environment and interactions, their life cycle, division and function (physiology) and eventual death.


Cell lines

Cells that can be maintained and grown in culture and display an immortal or indefinite life span.


Cell nutrients

The “food” that keeps cells alive.


Cell type

A specific subset of cells within the body, defined by their appearance, location and function.
  1. adipocyte: the functional cell type of fat, or adipose tissue, that is found throughout the body, particularly under the skin. Adipocytes store and synthesize fat for energy, thermal regulation and cushioning against mechanical shock.
  2. cardiomyocytes: the functional muscle cell type of the heart that allows it to beat continuously and rhythmically.
  3. chondrocyte: the functional cell type that makes cartilage for joints, ear canals, trachea, epiglottis, larynx, the discs between vertebrae and the ends of ribs.
  4. fibroblast: a connective or support cell found within most tissues of the body. Fibroblasts provide an instructive support scaffold to help the functional cell types of a specific organ perform correctly.
  5. hepatocyte: the functional cell type of the liver that makes enzymes for detoxifying metabolic waste, destroying red blood cells and reclaiming their constituents, and the synthesis of proteins for the blood plasma.
  6. hematopoietic cell: the functional cell type that makes blood. Hematopoietic cells are found within the bone marrow of adults. In the fetus, hematopoietic cells are found within the liver, spleen, bone marrow and support tissues surrounding the fetus in the womb.
  7. myocyte: the functional cell type of muscles.
  8. neuron: the functional cell type of the brain that is specialized in conducting impulses.
  9. osteoblast: the functional cell type responsible for making bone.
  10. islet cell: the functional cell of the pancreas that is responsible for secreting insulin, glucogon, gastrin and somatostatin. Together, these molecules regulate a number of processes including carbohydrate and fat metabolism, blood glucose levels and acid secretions into the stomach.



Mature, differentiated cartilage cells



The process in which an organism produces one or more genetically alike copies of itself by asexual means. Cloning may occur by propagation of cuttings, as in the case of plants; continual budding, as in the case of hydra; fission, as in the case of bacteria and protozoa; parthenogenic asexual reproduction as in the case of aphids; or somatic cell nuclear transfer, as in the case of higher order animals such as mammals. The term cloning can also be applied to a group of cells undergoing replication by repetitive mitoses (cell divisions).



A protein chemical substance that is the main support of skin, tendon, bone, cartilage and connective tissue



An enzyme formed when the skin is irritated or inflamed, collagenase breaks down the collagen fibers in the dermis, resulting in aging of the skin. In the laboratory it is used to purify islet cells.



The part of the cell not including the nucleus.


Dermal fibroblasts

Skin cells that produce collagen


Difference between medical device and a drug (from the FDA’s perspective)

Increasingly, pharmaceutical companies and medical device companies are developing and marketing combination products that contain both a device and a drug component. Examples include drug coated stents, prefilled drug delivery devices and antibiotic bone cement.



The process of development with an increase in the level of organization or complexity of a cell or tissue, accompanied with a more specialized function. To undergo a cellular progression to a more specialized type; the process of development with an increase in the level of organization or complexity of a cell or tissue, accompanied with a more specialized function.



The outer of three germ layers of the early embryo that gives rise in later development to the skin, cells of the amnion and chorion, nervous system, enamel of the teeth, lens of the eye and neural crest.



The product of a fertilized egg, from the zygote until the fetal stage.


Embryoid bodies

Spheroid 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.


Embryonic germline cells

Embryonic germline cells, also called EG cells, are pluripotent stem cells derived from the primitive germline cells (those cells that give rise to eggs and sperm). Their properties are similar to those of embryonic stem cells.


Embryonic stem cell

Embryonic stem (ES) cells are cells derived from the inner cell mass of developing blastocysts. An ES cell is self-renewing (can replicate itself), pluripotent (can form all cell types found in the body) and theoretically is immortal.



The inner of three germ layers of the early embryo that gives rise in later development to tissues such as the lungs, the intestine, the liver and the pancreas.


Ex vivo

Pertaining to a biological process or reaction taking place outside of a living cell or organism


Extracellular (Extracellular matrix)

Material secreted by and surrounding cells. Consists if fibers and ground substance.  It is the “glue” that holds cells together



The stage in development from the end of the embryonic stage, 7-8 weeks after fertilization, to developed organism that ends at birth.



A connective-tissue cell that secretes proteins and especially molecular collagen from which the extracellular fibrillar matrix of connective tissue forms


Functional tissue engineering

Functional tissue engineering involves the study of the structure and the function of living tissues, with the aim of recreating these tissues in the laboratory. Such engineered tissues could then be used to replace damaged body parts, or to study complex biological problems in a controlled environment.

Germ layers

The three germ layers are the endoderm, mesoderm and ectoderm and are the three precursory tissue layers of the early, primitive embryo (which form at approximately two weeks in the human) that give rise to all tissues of the body.



(Good Laboratory Practices) GLP prescribes a series of planning and operational procedures for experiments to ensure the generation of high quality and reliable test data



Good Manufacturing Practices (GMP) are standard guidelines set out by the FDA to ensure drug development is carried out in safe and quality processes, to avoid contamination and ensure repeatability.


Growth factors

A chemical that stimulates body cells to grow or make more cells. Growth factors are found naturally in the body, but can also be manufactured and used as drugs or in tissue engineering.


Hematopoietic stem cells 

The precursors of mature blood cells that are defined by their ability to replace the bone marrow system following its obliteration (for example, by g-irradiation) and can continue to produce mature blood cells.



Not homologous or uniform. In the context of cells, heterologous is a mixed or divergent cell population or of a divergent origin.



A tissue or organ from a donor (the person giving the organ or tissue) that will not be rejected by the recipient (the patient in whom the tissue or organ is transplanted). Rejection is caused because the immune system of the recipient sees the transplanted organ or tissue as foreign and tries to destroy it. Tissues from most people are not histocompatible with other people. In siblings, the probability of histocompatibility is higher, while identical twins are almost always histocompatible.



The study of the form of structures seen under the microscope. Also called microscopic anatomy, as opposed to gross anatomy which involves structures that can be observed with the naked eye.



Similar or uniform, often used in the context of genes and DNA sequences. In the context of stem cells, the term homologous recombination is a technique used to disable a gene in embryonic stem cells.


Human embryonic stem cell

A stem cell that is derived from the inner cell mass of a blastocyst and can differentiate into several tissue types in a dish. They are similar to embryonic stem cells from the mouse; however, in the mouse, it is possible to inject those cells into a blastocyst, to make a new mouse, while this is not, and should not, be possible in humans for ethical reasons. Human embryonic stem cells are harder to grow than mouse embryonic stem cells.


Immunologically safe

Will not cause any immune response problems when implanted in the body


In vitro fertilization

A procedure where an egg cell (the oocyte) and sperm cells are brought together in a dish (i.e. in vitro), so that a sperm cell can fertilize the egg. The resulting fertilized egg, called a zygote, will start dividing and after a several divisions, forms the embryo that can be implanted into the womb of a woman and give rise to pregnancy.


In vivo

Pertaining to a biochemical process or reaction taking place in a living cell or organism.


Inner cell mass

A small group of cells attached to the wall of the blastocyst (the embryo at a 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. it is the inner cell mass that will eventually give rise to all the organs and tissues of the future embryo and fetus, but do not give rise to the extra-embryonic tissues, such as the placenta.

Mammalian cells

Cells from mammals, ranging from animals to humans


Mesenchymal stem cells

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 (the lining of joints), fat tissue, and connective tissue (tissue that is in between organs and structures in the body).



The middle of three germ layers that gives rise later in development to such tissues as muscle, bone, and blood.



Study of the shape and visual appearance of cells, tissues and organs.


Multipotent stem cells

Stem cells whose progeny are of 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.


Neural stem cell

A type of stem cell that resides in the brain, which can make new nerve cells (called neurons) and other cells that support nerve cells (called glia). In the adult, neural stem cells can be found in very specific and very small areas of the brain where replacement of nerve cells is seen.



A part of the cell, situated more or less in the middle of the cell, that is surrounded by a specialized membrane and contains the DNA of the cell. This DNA is packaged into structures called chromosomes, which is the genetic, inherited material of cells.


Oligopotent progenitor cells

Progenitor cells that can produce more than one type of mature cell. An example is the myeloid progenitor cell which can give rise to mature blood cells, including blood granulocytes, monocytes, red blood cells, platelets, basophiles, eosinophiles and dendritic cells, but not T lymphocytes, B lymphocytes, or natural killer cells.



Any disease-producing microorganism or material



The description of the characteristics of a cell, a tissue or an animal; as black and white fur of a mouse are two p henotypes that can be found. The phenotype is determined by the genes (or the genotype) and by the environment. For example, short stature is a phenotype that can be genetically determined (and therefore inherited from the parents), but can also be caused by malnourishment during childhood (and therefore be caused by the environment).



A membranous organ that develops during pregnancy. It lines the uterine wall, partially envelopes the fetus, and is attached to the umbilical cord. The placenta exchanges nutrients, wastes, and gases between maternal and fetal blood. Substances ingested by the mother during pregnancy pass through the placenta to the fetus.



A phenomenon used to describe a cell that is capable of becoming a specialized cell type of different tissue. For example, when the same stem cell can make both new blood cells and new muscle cells.



A cell characteristic which permits stem cells to become all the cell types that are found in an implanted embryo, fetus, or developed organism.


Pluripotent stem cells

Stem cells that can become all the cell types that are found in an implanted embryo, fetus, or developed organism, but not embryonic components of the trophoblast and placenta (these are usually called extra-embryonic).


Post-implantation embryo

Implanted embryos in the early stages of development until the establishment of the body plan of a developed organism with identifiable tissues and organs.


Pre-implantation embryos

Fertilized eggs (zygotes) and all of the developmental stages up to, but not beyond, the blastocyst stage.


Progenitor cell

A progenitor cell, often confused with stem cell, is an early descendant of a stem cell that can only differentiate, but it cannot renew itself anymore. In contrast, a stem cell can renew itself (make more stem cells by cell division) or it can differentiate (divide and with each cell division evolve more and more into different types of cells). A progenitor cell is often more limited in the kinds of cells it can become than a stem cell.


Regenerative medicine

Clinical procedures that aim to repair damaged tissue or organs, most often by using tissue engineered scaffolds and stem cells to replace cells and tissues damaged by aging and by disease. In some cases, medical devices are part of the therapeutic procedure.


Reproductive cloning

Somatic cell nuclear transfer used for the production of a fetus and delivery of a live offspring that is genetically identical the donor of the somatic cell DNA.


In the context of engineered tissue, a scaffold is a material that can be formed in the shape of tissue that needs to be replaced (as an example a rotator cuff).  The scaffold can be biologically derived or a synthesized material.  The scaffold material must be biologically compatible for human implantation.  The scaffold is typically impregnated (seeded) with a patient’s cells before implantation.  Finally the scaffold must be designed to “dissolve ” as the cells grow on the scaffold.  Typically, in several months, the scaffold has disappeared and has been replaced by new tissue.



Implanted or impregnated as in seeding a scaffold with stem cells.


Somatic cell nuclear transfer

A technique in which the nucleus of a somatic cell (any cell of the body except sperm cells and egg cells) is injected, or transfered, into an egg, that has had its nucleus removed. If the new egg is then implanted into the womb of an animal, an individual will be born that is a clone. The clone has the identical genetic material as the somatic cell, which supplied the nucleus that carries the genetic material. This procedure was first developed for agricultural purposes. However, in human medicine, this technique can be used to isolate embryonic stem cells from eggs that have undergone nuclear transfer. When the somatic cell is supplied from the cells of a person, the stem cells isolated from the developing eggs can be used to make a tissue that will not be rejected by that person, because they have the same genetic material.


Somatic cells

All the cells within the developing or developed organism with the exception of germline (egg and sperm) cells.


Stem cells

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



An internal tissue layer in the wall of the gastrointestinal tract


Synthetic biomaterials/scaffolds.

As contrasted with natural materials that can be used to form scaffolds for tissue engineering, some scientists are developing “artificial”, chemically formulated scaffolds.  There may be advantages to these materials, in particular in the ability to control the structure and the functions of the resultant tissue.


Therapeutic cloning

Somatic cell nuclear transfer for the isolation of embryonic stem cells. The embryonic stem cells are derived from the blastocyst (before it becomes a fetus) and can be instructed to form particular cell types (e.g. heart muscle) to be implanted into damaged tissue (e.g. heart) to restore its function. If the stem cells are placed back into the individual who gave the DNA for the somatic cell nuclear transfer, the embryonic stem cells and their derivatives are genetically identical and thus immunocompatible (they will not be rejected).


Tissue function

The role or the capacity of specific tissue; as an example, cardiac tissue must beat (contract) to perform its role of having the heart pump blood


Totipotent stem cells

Stem cells that can give rise to all cell types that are found in an embryo, fetus, or developed organism, including the embryonic components of the trophoblast and placenta required to support development and birth. The zygote and the cells at the very early stages following fertilization (i.e., the 2-cell stage) are considered totipotent.



The ability of a particular cell of one tissue, organ or system, including stem or progenitor cells, to differentiate into a cell type characteristic of another tissue, organ, or system; e.g., blood stem cells changing to liver cells.


Transplantation biology

The science that studies the transplantation of organs and cells. Transplantation biologists investigate scientific questions to understand why foreign tissues and organs are rejected, the way transplanted organs function in the recipient, how this function can be maintained or improved, and how the organ to be transplanted should be handled to obtain optimal results.



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 cells surrounding it.



A digestive enzyme of pancreatic origin; catalyzes the hydrolysis of proteins to smaller polypeptide units


Umbilical cord stem cells

Hematopoietic stem cells are present in the blood of the umbilical cord during and shortly after delivery. These stem cells are in the blood at the time of delivery, because they move from the liver, where blood-formation takes place during fetal life, to the bone marrow, where blood is made after birth. Umbilical cord stem cells are similar to stem cells that reside in bone marrow, and can be used for the treatment of leukemia, and other diseases of the blood. Efforts are now being undertaken to collect these 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.


Undifferentiated cells

Cells that have not matured; they have not formed an “identity” such as skin cells, muscle cells, cardiac cells, etc.


Unipotent stem cells

Stem cells that self-renew as well as give rise to a single mature cell type; e.g., spermatogenic stem cells.


Urinary bladder matrix

Extracellular matrix derived from the urinary bladder (typically of a pig) that is used for tissue engineered scaffold.



Ventricular assist device (VAD) is a type of mechanical heart that is surgically implanted in the patient's chest during open-heart surgery to help the heart pump blood.

Xenogenic cells

Cells originating outside the organism or from a foreign substance introduced into the organism.



The cell that results from the union of sperm and egg during fertilization. Cell division begins after the zygote forms.