Stem cellIn multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can differentiate into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell in a cell lineage. They are found in both embryonic and adult organisms, but they have slightly different properties in each. They are usually distinguished from progenitor cells, which cannot divide indefinitely, and precursor or blast cells, which are usually committed to differentiating into one cell type.
Adult stem cellAdult stem cells are undifferentiated cells, found throughout the body after development, that multiply by cell division to replenish dying cells and regenerate damaged tissues. Also known as somatic stem cells (from Greek σωματικóς, meaning of the body), they can be found in juvenile, adult animals, and humans, unlike embryonic stem cells. Scientific interest in adult stem cells is centered around two main characteristics.
Stem-cell nicheStem-cell niche refers to a microenvironment, within the specific anatomic location where stem cells are found, which interacts with stem cells to regulate cell fate. The word 'niche' can be in reference to the in vivo or in vitro stem-cell microenvironment. During embryonic development, various niche factors act on embryonic stem cells to alter gene expression, and induce their proliferation or differentiation for the development of the fetus.
Embryonic stem cellEmbryonic stem cells (ESCs) are pluripotent stem cells derived from the inner cell mass of a blastocyst, an early-stage pre-implantation embryo. Human embryos reach the blastocyst stage 4–5 days post fertilization, at which time they consist of 50–150 cells. Isolating the inner cell mass (embryoblast) using immunosurgery results in destruction of the blastocyst, a process which raises ethical issues, including whether or not embryos at the pre-implantation stage have the same moral considerations as embryos in the post-implantation stage of development.
Stem-cell therapyStem-cell therapy is the use of stem cells to treat or prevent a disease or condition. , the only established therapy using stem cells is hematopoietic stem cell transplantation. This usually takes the form of a bone-marrow transplantation, but the cells can also be derived from umbilical cord blood. Research is underway to develop various sources for stem cells as well as to apply stem-cell treatments for neurodegenerative diseases and conditions such as diabetes and heart disease.
Induced pluripotent stem cellInduced pluripotent stem cells (also known as iPS cells or iPSCs) are a type of pluripotent stem cell that can be generated directly from a somatic cell. The iPSC technology was pioneered by Shinya Yamanaka and Kazutoshi Takahashi in Kyoto, Japan, who together showed in 2006 that the introduction of four specific genes (named Myc, Oct3/4, Sox2 and Klf4), collectively known as Yamanaka factors, encoding transcription factors could convert somatic cells into pluripotent stem cells.
Stem cell controversyThe stem cell controversy is the consideration of the ethics of research involving the development and use of human embryos. Most commonly, this controversy focuses on embryonic stem cells. Not all stem cell research involves human embryos. For example, adult stem cells, amniotic stem cells, and induced pluripotent stem cells do not involve creating, using, or destroying human embryos, and thus are minimally, if at all, controversial.
Stem-cell lineA stem cell line is a group of stem cells that is cultured in vitro and can be propagated indefinitely. Stem cell lines are derived from either animal or human tissues and come from one of three sources: embryonic stem cells, adult stem cells, or induced stem cells. They are commonly used in research and regenerative medicine. Stem cell By definition, stem cells possess two properties: (1) they can self-renew, which means that they can divide indefinitely while remaining in an undifferentiated state; and (2) they are pluripotent or multipotent, which means that they can differentiate to form specialized cell types.
Mesenchymal stem cellMesenchymal stem cells (MSCs) also known as mesenchymal stromal cells or medicinal signaling cells are multipotent stromal cells that can differentiate into a variety of cell types, including osteoblasts (bone cells), chondrocytes (cartilage cells), myocytes (muscle cells) and adipocytes (fat cells which give rise to marrow adipose tissue).
Hematopoietic stem cellHematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the very first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within the (midgestational) aorta-gonad-mesonephros region, through a process known as endothelial-to-hematopoietic transition. In adults, haematopoiesis occurs in the red bone marrow, in the core of most bones. The red bone marrow is derived from the layer of the embryo called the mesoderm.
Cell potencyCell potency is a cell's ability to differentiate into other cell types. The more cell types a cell can differentiate into, the greater its potency. Potency is also described as the gene activation potential within a cell, which like a continuum, begins with totipotency to designate a cell with the most differentiation potential, pluripotency, multipotency, oligopotency, and finally unipotency. Totipotency (Lat. totipotentia, "ability for all [things]") is the ability of a single cell to divide and produce all of the differentiated cells in an organism.
HydrogelA hydrogel is a biphasic material, a mixture of porous, permeable solids and at least 10% by weight or volume of interstitial fluid composed completely or mainly by water. In hydrogels the porous permeable solid is a water insoluble three dimensional network of natural or synthetic polymers and a fluid, having absorbed a large amount of water or biological fluids. These properties underpin several applications, especially in the biomedical area. Many hydrogels are synthetic, but some are derived from nature.
Tissue engineeringTissue engineering is a biomedical engineering discipline that uses a combination of cells, engineering, materials methods, and suitable biochemical and physicochemical factors to restore, maintain, improve, or replace different types of biological tissues. Tissue engineering often involves the use of cells placed on tissue scaffolds in the formation of new viable tissue for a medical purpose but is not limited to applications involving cells and tissue scaffolds.
Regenerative medicineRegenerative medicine deals with the "process of replacing, engineering or regenerating human or animal cells, tissues or organs to restore or establish normal function". This field holds the promise of engineering damaged tissues and organs by stimulating the body's own repair mechanisms to functionally heal previously irreparable tissues or organs. Regenerative medicine also includes the possibility of growing tissues and organs in the laboratory and implanting them when the body cannot heal itself.
Cancer stem cellCancer stem cells (CSCs) are cancer cells (found within tumors or hematological cancers) that possess characteristics associated with normal stem cells, specifically the ability to give rise to all cell types found in a particular cancer sample. CSCs are therefore tumorigenic (tumor-forming), perhaps in contrast to other non-tumorigenic cancer cells. CSCs may generate tumors through the stem cell processes of self-renewal and differentiation into multiple cell types.
Amniotic stem cellsAmniotic stem cells are the mixture of stem cells that can be obtained from the amniotic fluid as well as the amniotic membrane. They can develop into various tissue types including skin, cartilage, cardiac tissue, nerves, muscle, and bone. The cells also have potential medical applications, especially in organ regeneration. The stem cells are usually extracted from the amniotic sac by amniocentesis which occurs without harming the embryos.
T cellT cells are one of the important types of white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their cell surface. T cells are born from hematopoietic stem cells, found in the bone marrow. Developing T cells then migrate to the thymus gland to develop (or mature). T cells derive their name from the thymus. After migration to the thymus, the precursor cells mature into several distinct types of T cells.
TransdifferentiationTransdifferentiation, also known as lineage reprogramming, is the process in which one mature somatic cell is transformed into another mature somatic cell without undergoing an intermediate pluripotent state or progenitor cell type. It is a type of metaplasia, which includes all cell fate switches, including the interconversion of stem cells. Current uses of transdifferentiation include disease modeling and drug discovery and in the future may include gene therapy and regenerative medicine.
In vivoStudies that are in vivo (Latin for "within the living"; often not italicized in English) are those in which the effects of various biological entities are tested on whole, living organisms or cells, usually animals, including humans, and plants, as opposed to a tissue extract or dead organism. This is not to be confused with experiments done in vitro ("within the glass"), i.e., in a laboratory environment using test tubes, Petri dishes, etc.
Ex vivoEx vivo (Latin: "out of the living") literally means that which takes place outside an organism. In science, ex vivo refers to experimentation or measurements done in or on tissue from an organism in an external environment with minimal alteration of natural conditions. A primary advantage of using ex vivo tissues is the ability to perform tests or measurements that would otherwise not be possible or ethical in living subjects. Tissues may be removed in many ways, including in part, as whole organs, or as larger organ systems.
