Stem cells found in different tissues of the developed, adult organism which remain in an unspecialized state. These stem cells can produce 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. Their natural role in most cases is to replenish dying cells and regenerate damaged tissue, a role which may be enhanced for therapeutic purposes.

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

Cell, tissue or organ transplants from one individual back to the same individual. Such transplants do not induce an immune response and are not rejected, because the transplanted tissue is genetically identical to the recipient. Future therapies may involve harvesting stem cells from the patient, regenerating tissues or organs, and conducting autologous transplantation to return the material to the patient to repair or replace damaged tissue.

A material which is in whole or in part composed of living matter, such as a polymer scaffolding perfused with cells. Biomaterials may be used as a medical device which augments or replaces natural tissue for therapeutic effect. The combination of synthetic and living material derived from stem cells could enable the repair of heart valves, bone, cartilage and other tissues by replacing or patching the damaged parts with materials that are genetically identical to the patient, and therefore safe from immunological rejection.

A very early embryo consisting of approximately 150-300 cells. The blastocyst is a spherical cell mass produced by cleavage of the zygote (fertilized egg) after approximately 5-7 days of cell divisions. It contains a microscopic 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).

Stem cells, which make up only a very small percentage of the total tumor mass, have been found to be the source of some, and possibly most cancers. The cancer stem cell hypothesis states that certain stem cells remain in tissues to replenish them after injury or disease, yet because they are self-renewing and can survive for a longer period of time, the adult stem cells can also accumulate mutations which would cause them to spin off cells that divide uncontrollably, forming a tumor. Since current cancer treatments reduce tumor mass but might not affect the stem cells seeding the tumor, new therapeutic strategies may be directed at the cancer-causing stem cells.

Cells of a particular type that can be maintained and grown in culture, outside the body in a Petri dish. Culture conditions can vary widely for different cell types, with many factors adjusted to enable the cells to thrive and divide. These factors may include temperature, gas composition, pH, glucose concentration, and the presence of growth factors and other nutrients. Cell lines can be used in biological assays to decipher molecular pathways or screen for new therapeutics, greatly facilitating the study of natural and disease biology in the laboratory.

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, in hydra; fission, in bacteria and protozoa; or parthogenic asexual reproduction in aphids. In higher order animals, such as mammals, cloning can be carried out by somatic cell nuclear transfer. A form of cloning occurs naturally in mammals in the form of identical twins and triplets. The term cloning is also applied to cells undergoing replication by repetitive mitoses (cell divisions) which produces cells that are genetically identical to one another. 

Stem cells can be derived from blood the umbilical cord at the time of birth. Umbilical cord stem cells are rich in hematopoietic stem cells, which normally reside in the bone marrow and can be used for the treatment of leukemia and other blood diseases. Numerous public and private cord blood banks have emerged to collect and store neonatal cord blood as future "insurance" against diseases that might be treatable using a stem cell approach.

The study of the process by which organisms grow and develop, including the formation and specialization of cells and tissues, from embryo to adulthood. Modern research in developmental biology examines the processes of cell growth and differentiation, and the roll in which stem cells seed and control the development of tissues and organs.

The process by which a cell reverts to a less specialized, progenitor state.

The process by which a stem cell loses its capacity for self-renewal and becomes a mature and definitive cell type - for example a blood cell, nerve cell, pancreatic cell, or cardiac muscle cell. Learning the triggers that cause differentiation to specific cell types is a major area of study in stem cell science.

The process of taking fully mature, differentiated stem cells and inducing them to become another cell type without going through a stem cell (iPS) state. The transition from one cell type directly to another is referred to as "transdifferentiation." In the case of pancreatic cells, the method employs three developmental factors (different from the ones used to create iPS cells) causing acinar cells to switch directly to a insulin producing beta cells.

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

Cells that are derived from the inner cell mass of a human blastocyst and, because they are pluripotent, can differentiate into any cell or tissue type in the body, or potentially in a laboratory dish. Some believe that new methods used to create induced pluripotent stem (iPS) cells from non-embryo sources eliminates the need for human embryonic stem cells (hESCs) and their attendant ethical concerns. However, hESCs continue to be an essential tool in the study of regenerative and developmental biology and serve as a gold standard for continued refinement of iPS technology.

An indispensable instrument in stem cell research, FACS enables the rapid characterization, counting and isolation of cells suspended in a stream of fluid. The technology employs a laser beam of a single wavelength directed into the stream and fluorescence detectors that measure the scattered light. If a fluorescing molecule is detected in the stream (such as a tagged antibody attached to the surface of a stem cell), the data is recorded, and optionally, the stream briefly diverted to collect the tagged cell.

HSCs are stem cells that give rise to all blood cell types. They may be multipotent, oligopotent or unipotent and lead to the generation of erythrocytes (red blood cells), macrophages (the "clean up crew" of the immune system), neutrophils, basophils, eosinophils and dendritic cells (immunological "helper" cells), megakaryocytes and platelets (involved in blood clotting), as well as the immune effector  T-cells, B-cells, Natural Killer cells.

Technology that employs automation and robotics to conduct hundreds or thousands of biological assay experiments within a short period of time. Typically, high throughput screening (HTS) systems will use rectangular plastic trays containing 96, 384, 1536, or 3456 wells (or more in microfluidic systems), where each well may hold a small amount of liquid sample containing cells. Automated liquid handling can add factors or compounds to test the effect on the cells. HTS can be used (for example) to screen hundreds of thousands of chemical compounds as potential drug candidates, or to identify factors that determine the ultimate fate of a differentiating stem cell.

Somatic cells induced to a pluripotent embryonic stem cell-like state. The process of creating these cells, often referred to as "reprogramming" involves introducing a combination of three to four genes for transcription factors, delivered by retroviruses, into the somatic cell. Cells can be taken from patients with specific diseases such as ALS, Parkinson's, or cardiovascular disease and induced to form iPS cells. Multiple uses can be derived from iPS cells when they are differentiated to more specialized cell types, including the development of assays for studying disease processes, scanning drug candidates for safety and effectiveness, or application to regenerative medicine.

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 eventually gives 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. 

Latin for "in glass," the term in vitro refers to experiments that are performed outside an organism's body, in laboratory glassware (or as is more often the case, plasticware) such as a test tube or a Petri dish. 

A procedure where an egg cell (the oocyte) and sperm cells are brought together in a laboratory 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. 

Latin for "within the living," the term in vivo refers to experiments conducted using a whole, living organism. In vivo experimentation is often necessary to confirm hypotheses that can not be thoroughly tested in the artificial environment of  laboratory glassware. In vivo research, which can be conducted in animals or controlled human clinical trials, provide more complete information on the overall effects of a disease or its treatment.

A series of interactions between genes, proteins, and other biological factors that leads to a biological effect, such as the differentiation of one cell type to another, the division of a cell, the production of antibodies, cell homing, the formation of tissue and body patterns during development, the secretion of factors such as insulin, etc.

Stem cells that can produce cells of multiple differentiated cell types, but all within a particular tissue, organ, or physiological system. For example, blood-forming (hematopoietic) stem cells are multipotent cells that can produce all cell types that are normal components of the blood.

A form of reproduction where an egg develops without sperm. Parthenogenesis occurs commonly among insects and other arthropods and less frequently among higher animals such as fish. Artificially inducing parthenogenesis with human eggs may be a means to isolate stem cells from an embryo, without fertilization.

Stem cells that can become all the cell types that are found in an organism, but not the embryonic components of the trophoblast and placenta (these are usually called extra-embryonic tissues). Isolated human embryonic stem cells are pluripotent, and although they can generate any cell in the body, they would not be able to generate the placenta. 

Often confused with a stem cell, this is an early descendant of a stem cell that can only differentiate, but 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. In scientific terms, it is said that progenitor cells are more differentiated than stem cells.

Stem cells, like most cells, display a characteristic set of protein molecules on their cell surface called markers, which can be used to make a preliminary identification. Using fluorescently tagged antibodies that attach to these markers, an instrument called a fluorescence activated cell sorter (FACS) can separate and isolate the rare stem cell among a population of thousands of differentiated cells.

Medical interventions that aim to repair damaged organs, most often by using stem cells to replace cells and tissues damaged by aging and by disease.

The process of creating an induced pluripotent stem (iPS) cell. Originally, reprogramming methods involved introducing a combination of three to four genes into an adult cell using retroviruses. The use of oncogenes and retroviruses, both of which have the potential of inducing tumor growth, exclude these methods from therapeutic applications. More recently, reprogramming methods have been derived that employ other genes or chemical factors deemed to be safer alternatives for future applications in regenerative medicine.

The ability of a stem cell to divide and form more stem cells with identical properties to the parent cell, thereby allowing the population to be replenished indefinitely. 

All the cells within the developing or developed organism except germline (egg and sperm) cells that have reached a terminal differentiated state.

Sometimes known as therapeutic cloning. A process by which a nucleus from a single cell (for example a skin cell) is transferred into an unfertilized egg, from which the nucleus (the genetic contents) have been removed. The resulting reconstructed embryo is then allowed to develop to the blastocyst stage. Embryonic stem cells derived from this blastocyst are genetically identical to the donor of the original nucleus.

The migration of stem cells through the blood or tissue to an ultimate destination where it differentiates and replaces or builds tissue. Stem cell homing is triggered by interactions between the cell surface adhesion molecules (such as selectins, integrins and ICAMs) and the cell's surrounding environment.

Cells that can both self-renew (make more stem cells by cell division) and differentiate into mature, specialized cells such as blood cells, nerve cells, muscle cells, etc. 

Therapeutic cloning is a term used to refer to somatic cell nuclear transfer (SCNT). Embryonic stem cells derived from therapeutic cloning (or SCNT) can then be instructed to form particular cell types, for example heart muscle. If the stem cells are placed back into the individual who gave the DNA for the somatic cell nuclear transfer, these cells are genetically identical and will not be rejected by the donors immune system.

Cells that can form an entire organism, including the extra embryonic tissue such as the placenta (in mammals) that do not become part of the fetus. Immediately after fertilization, a single totipotent cell (the zygote) is formed. This cell continues to divide into identical totipotent cells. About four days after fertilization and continued cell division, the totipotent cells begin to specialize into pluripotent and multipotent cells capable of generating only a specific subset of cells in the developing organism.

The area of focus or effort to transition basic research discoveries into clinical applications that benefit patients.