Stem cell

Stem cell

Overview
This article is about the cell type. For the medical therapy, see Stem Cell Treatments
Stem cell treatments
Stem cell treatments are a type of intervention strategy that introduces new cells into damaged tissue in order to treat disease or injury. Many medical researchers believe that stem cell treatments have the potential to change the face of human disease and alleviate suffering...



Stem cells are biological cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 found in all multicellular organisms, that can divide
Cell division
Cell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort...

 (through mitosis
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...

) and differentiate
Cellular differentiation
In developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation occurs numerous times during the development of a multicellular organism as the organism changes from a simple zygote to a complex system of...

 into diverse specialized cell types and can self-renew to produce more stem cells. In mammals, there are two broad types of stem cells: embryonic stem cell
Embryonic stem cell
Embryonic stem cells are pluripotent stem cells derived from the inner cell mass of the blastocyst, an early-stage embryo. Human embryos reach the blastocyst stage 4–5 days post fertilization, at which time they consist of 50–150 cells...

s, which are isolated from the inner cell mass
Inner cell mass
In early embryogenesis of most eutherian mammals, the inner cell mass is the mass of cells inside the primordial embryo that will eventually give rise to the definitive structures of the fetus...

 of blastocyst
Blastocyst
The blastocyst is a structure formed in the early embryogenesis of mammals, after the formation of the morula. It is a specifically mammalian example of a blastula. It possesses an inner cell mass , or embryoblast, which subsequently forms the embryo, and an outer layer of cells, or trophoblast,...

s, and adult stem cell
Adult stem cell
Adult stem cells are undifferentiated cells, found throughout the body after embryonic development, that multiply by cell division to replenish dying cells and regenerate damaged tissues...

s, which are found in various tissues.
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Encyclopedia
This article is about the cell type. For the medical therapy, see Stem Cell Treatments
Stem cell treatments
Stem cell treatments are a type of intervention strategy that introduces new cells into damaged tissue in order to treat disease or injury. Many medical researchers believe that stem cell treatments have the potential to change the face of human disease and alleviate suffering...



Stem cells are biological cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

 found in all multicellular organisms, that can divide
Cell division
Cell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort...

 (through mitosis
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...

) and differentiate
Cellular differentiation
In developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation occurs numerous times during the development of a multicellular organism as the organism changes from a simple zygote to a complex system of...

 into diverse specialized cell types and can self-renew to produce more stem cells. In mammals, there are two broad types of stem cells: embryonic stem cell
Embryonic stem cell
Embryonic stem cells are pluripotent stem cells derived from the inner cell mass of the blastocyst, an early-stage embryo. Human embryos reach the blastocyst stage 4–5 days post fertilization, at which time they consist of 50–150 cells...

s, which are isolated from the inner cell mass
Inner cell mass
In early embryogenesis of most eutherian mammals, the inner cell mass is the mass of cells inside the primordial embryo that will eventually give rise to the definitive structures of the fetus...

 of blastocyst
Blastocyst
The blastocyst is a structure formed in the early embryogenesis of mammals, after the formation of the morula. It is a specifically mammalian example of a blastula. It possesses an inner cell mass , or embryoblast, which subsequently forms the embryo, and an outer layer of cells, or trophoblast,...

s, and adult stem cell
Adult stem cell
Adult stem cells are undifferentiated cells, found throughout the body after embryonic development, that multiply by cell division to replenish dying cells and regenerate damaged tissues...

s, which are found in various tissues. In adult
Adult
An adult is a human being or living organism that is of relatively mature age, typically associated with sexual maturity and the attainment of reproductive age....

 organisms, stem cells and progenitor cell
Progenitor cell
A progenitor cell is a biological cell that, like a stem cell, has a tendency to differentiate into a specific type of cell, but is already more specific than a stem cell and is pushed to differentiate into its "target" cell...

s act as a repair system for the body, replenishing adult tissues. In a developing embryo, stem cells can differentiate into all the specialized cells (these are called pluripotent cells), but also maintain the normal turnover of regenerative organs, such as blood, skin, or intestinal tissues.

Stem cells can now be artificially grown and transformed into specialized cell types with characteristics consistent with cells of various tissues such as muscles or nerves through cell culture
Cell culture
Cell culture is the complex process by which cells are grown under controlled conditions. In practice, the term "cell culture" has come to refer to the culturing of cells derived from singlecellular eukaryotes, especially animal cells. However, there are also cultures of plants, fungi and microbes,...

. Highly plastic adult stem cells are routinely used in medical therapies. Stem cells can be taken from a variety of sources, including umbilical cord blood and bone marrow
Bone marrow
Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...

. Embryonic cell lines and autologous embryonic stem cells generated through therapeutic cloning have also been proposed as promising candidates for future therapies. Research into stem cells grew out of findings by Ernest A. McCulloch
Ernest McCulloch
Ernest Armstrong McCulloch, OC, O.Ont, FRSC was a University of Toronto cellular biologist, best known for demonstrating – with James Till – the existence of stem cells.-Biography:...

 and James E. Till
James Till
James Edgar Till, OC, O.Ont, FRSC is a University of Toronto biophysicist, best known for demonstrating – with Ernest McCulloch – the existence of stem cells.-Early work:...

 at the University of Toronto
University of Toronto
The University of Toronto is a public research university in Toronto, Ontario, Canada, situated on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution of higher learning in Upper Canada...

 in the 1960s.

There are three sources of autologous adult stem cells: 1) Bone marrow, which requires extraction by harvesting, that is, drilling into bone (typically the femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

 or iliac crest
Iliac crest
-External links: - "Superficial muscles of the gluteal region and posterior thigh." - "Anterior Abdominal Wall: Osteology and Surface Anatomy " - "The Back, Posterior View" * *...

), 2) Adipose tissue (lipid cells), which requires extraction by liposuction, and 3) Blood, which requires extraction through pheresis, wherein blood is drawn from the donor, (similar to a blood donation) passed through a machine that extracts the stem cells and returns other portions of the blood to the donor.

Of all stem cell types, autologous harvesting involves the least risk. By definition, autologous cells are obtained from one's own body, just as one may bank his or her own blood for elective surgical procedures.

Properties


The classical definition of a stem cell requires that it possess two properties:
  • Self-renewal: the ability to go through numerous cycles
    Cell cycle
    The cell cycle, or cell-division cycle, is the series of events that takes place in a cell leading to its division and duplication . In cells without a nucleus , the cell cycle occurs via a process termed binary fission...

     of cell division
    Cell division
    Cell division is the process by which a parent cell divides into two or more daughter cells . Cell division is usually a small segment of a larger cell cycle. This type of cell division in eukaryotes is known as mitosis, and leaves the daughter cell capable of dividing again. The corresponding sort...

     while maintaining the undifferentiated state.
  • Potency: the capacity to differentiate
    Cellular differentiation
    In developmental biology, cellular differentiation is the process by which a less specialized cell becomes a more specialized cell type. Differentiation occurs numerous times during the development of a multicellular organism as the organism changes from a simple zygote to a complex system of...

     into specialized cell types. In the strictest sense, this requires stem cells to be either totipotent or pluripotent—to be able to give rise to any mature cell type, although multipotent or unipotent progenitor cell
    Progenitor cell
    A progenitor cell is a biological cell that, like a stem cell, has a tendency to differentiate into a specific type of cell, but is already more specific than a stem cell and is pushed to differentiate into its "target" cell...

    s are sometimes referred to as stem cells.Apart from this it is being said that stem cells function is regulated in a feed back mechanism.

Self-renewal


Two mechanisms to ensure that the stem cell population is maintained exist:
  1. Obligatory asymmetric replication
    Asymmetric cell division
    An asymmetric cell division produces two daughter cells with different cellular fates. This is in contrast to normal, symmetric, cell divisions, which give rise to daughter cells of equivalent fates...

    : a stem cell divides into one father cell that is identical to the original stem cell, and another daughter cell that is differentiated
  2. Stochastic differentiation: when one stem cell develops into two differentiated daughter cells, another stem cell undergoes mitosis
    Mitosis
    Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...

     and produces two stem cells identical to the original.

Potency definitions





Potency specifies the differentiation potential (the potential to differentiate into different cell types) of the stem cell.
  • Totipotent (a.k.a omnipotent) stem cells can differentiate into embryonic and extraembryonic cell types. Such cells can construct a complete, viable organism. These cells are produced from the fusion of an egg and sperm cell. Cells produced by the first few divisions of the fertilized egg are also totipotent.
  • Pluripotent stem cells are the descendants of totipotent cells and can differentiate into nearly all cells, i.e. cells derived from any of the three germ layer
    Germ layer
    A germ layer, occasionally referred to as a germinal epithelium, is a group of cells, formed during animal embryogenesis. Germ layers are particularly pronounced in the vertebrates; however, all animals more complex than sponges produce two or three primary tissue layers...

    s.
  • Multipotent stem cells can differentiate into a number of cells, but only those of a closely related family of cells.
  • Oligopotent stem cells can differentiate into only a few cells, such as lymphoid or myeloid stem cells.
  • Unipotent cells can produce only one cell type, their own, but have the property of self-renewal, which distinguishes them from non-stem cells (e.g., muscle stem cells).

Identification


The practical definition of a stem cell is the functional definition—a cell that has the potential to regenerate tissue over a lifetime. For example, the defining test for a bone marrow or hematopoietic stem cell (HSC) is the ability to transplant one cell and save an individual without HSCs. In this case, a stem cell must be able to produce new blood cells and immune cells over a long term, demonstrating potency. It should also be possible to isolate stem cells from the transplanted individual, which can themselves be transplanted into another individual without HSCs, demonstrating that the stem cell was able to self-renew.

Properties of stem cells can be illustrated in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...

, using methods such as clonogenic assay
Mesenchymal stem cell
Mesenchymal stem cells, or MSCs, are multipotent stem cells that can differentiate into a variety of cell types, including: osteoblasts , chondrocytes and adipocytes...

s, in which single cells are assessed for their ability to differentiate and self-renew. Stem cells can also be isolated by their possession of a distinctive set of cell surface markers. However, in vitro culture conditions can alter the behavior of cells, making it unclear whether the cells will behave in a similar manner in vivo
In vivo
In vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research...

. There is considerable debate as to whether some proposed adult cell populations are truly stem cells.

Embryonic


Embryonic stem cell lines (ES cell lines) are cultures of cells derived from the epiblast
Epiblast
In amniote animal embryology, the epiblast is a tissue type derived either from the inner cell mass in mammals or the blastodisc in birds and reptiles. It lies above the hypoblast.-Mammals:...

 tissue of the inner cell mass
Inner cell mass
In early embryogenesis of most eutherian mammals, the inner cell mass is the mass of cells inside the primordial embryo that will eventually give rise to the definitive structures of the fetus...

 (ICM) of a blastocyst
Blastocyst
The blastocyst is a structure formed in the early embryogenesis of mammals, after the formation of the morula. It is a specifically mammalian example of a blastula. It possesses an inner cell mass , or embryoblast, which subsequently forms the embryo, and an outer layer of cells, or trophoblast,...

 or earlier morula
Morula
A morula is an embryo at an early stage of embryonic development, consisting of cells in a solid ball contained within the zona pellucida....

 stage embryos. A blastocyst is an early stage embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

—approximately four to five days old in humans and consisting of 50–150 cells. ES cells are pluripotent and give rise during development to all derivatives of the three primary germ layer
Germ layer
A germ layer, occasionally referred to as a germinal epithelium, is a group of cells, formed during animal embryogenesis. Germ layers are particularly pronounced in the vertebrates; however, all animals more complex than sponges produce two or three primary tissue layers...

s: ectoderm, endoderm and mesoderm. In other words, they can develop into each of the more than 200 cell types of the adult body
Human body
The human body is the entire structure of a human organism, and consists of a head, neck, torso, two arms and two legs.By the time the human reaches adulthood, the body consists of close to 100 trillion cells, the basic unit of life...

 when given sufficient and necessary stimulation for a specific cell type. They do not contribute to the extra-embryonic membranes or the placenta
Placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...

. The endoderm is composed of the entire gut tube and the lungs, the ectoderm gives rise to the nervous system and skin, and the mesoderm gives rise to muscle, bone, blood—in essence, everything else that connects the endoderm to the ectoderm.

Nearly all research to date has made use of mouse embryonic stem cells (mES) or human embryonic stem cells (hES). Both have the essential stem cell characteristics, yet they require very different environments in order to maintain an undifferentiated state. Mouse ES cells are grown on a layer of gelatin and require the presence of leukemia inhibitory factor (LIF). Human ES cells are grown on a feeder layer of mouse embryonic fibroblasts (MEFs) and require the presence of basic fibroblast growth factor (bFGF or FGF-2). Without optimal culture conditions or genetic manipulation, embryonic stem cells will rapidly differentiate.

A human embryonic stem cell is also defined by the presence of several transcription factors and cell surface proteins. The transcription factors Oct-4
Oct-4
Oct-4 also known as POU5F1 is a protein that in humans is encoded by the POU5F1 gene. Oct-4 is a homeodomain transcription factor of the POU family. This protein is critically involved in the self-renewal of undifferentiated embryonic stem cells...

, Nanog
NANOG
The North American Network Operators' Group is an educational and operational forum for the coordination and dissemination of technical information related to backbone/enterprise networking technologies and operational practices. It runs meetings, talks, surveys, and an influential mailing list...

, and Sox2
SOX2
SRY -box 2, also known as SOX2, is a transcription factor that is essential to maintain self-renewal of undifferentiated embryonic stem cells....

 form the core regulatory network that ensures the suppression of genes that lead to differentiation and the maintenance of pluripotency. The cell surface antigens most commonly used to identify hES cells are the glycolipids stage specific embryonic antigen 3
Stage specific embryonic antigen 3
Stage-specific embryonic antigen 3 is a glycosphingolipid, specifically, an oligosaccharide composed of five carbohydrate units connected to a sphingolipid. Sphinogolipids were originally discovered in 1884 by Dr. Thudichum who named them after the Sphinx of Greek mythology in reference to the...

 and 4 and the keratan sulfate antigens Tra-1-60 and Tra-1-81. The molecular definition of a stem cell includes many more proteins and continues to be a topic of research.

There are currently no approved treatments using embryonic stem cells. The first human trial was approved by the US Food and Drug Administration in January 2009. However, the human trial had not yet been initiated until October 13, 2010 in Atlanta for spinal injury victims. ES cells, being pluripotent cells, require specific signals for correct differentiation—if injected directly into another body, ES cells will differentiate into many different types of cells, causing a teratoma
Teratoma
A teratoma is an encapsulated tumor with tissue or organ components resembling normal derivatives of all three germ layers. There are rare occasions when not all three germ layers are identifiable...

. Differentiating ES cells into usable cells while avoiding transplant rejection are just a few of the hurdles that embryonic stem cell researchers still face. Many nations currently have moratoria
Moratorium (law)
A moratorium is a delay or suspension of an activity or a law. In a legal context, it may refer to the temporary suspension of a law to allow a legal challenge to be carried out....

 on either ES cell research or the production of new ES cell lines. Because of their combined abilities of unlimited expansion and pluripotency, embryonic stem cells remain a theoretically potential source for regenerative medicine
Regenerative medicine
Regenerative medicine is the "process of replacing or regenerating human cells, tissues or organs to restore orestablish normal function". This field holds the promise of regenerating damaged tissues and organs in the body by replacing damaged tissue and/or by stimulating the body's own repair...

 and tissue replacement after injury or disease.

Fetal


The primitive stem cells located in the organs of fetuses are referred to as fetal stem cells.

Adult


Also known as somatic
Somatic
The term somatic means 'of the body',, relating to the body. In medicine, somatic illness is bodily, not mental, illness. The term is often used in biology to refer to the cells of the body in contrast to the germ line cells which usually give rise to the gametes...

 (from Greek Σωματικóς, "of the body") stem cells and germline (giving rise to gametes) stem cells, they can be found in children, as well as adults.

Pluripotent adult stem cells are rare and generally small in number but can be found in a number of tissues including umbilical cord blood. A great deal of adult stem cell research to date has had the aim of characterizing the capacity of the cells to divide or self-renew indefinitely and their differentiation potential. In mice, pluripotent stem cells are directly generated from adult fibroblast cultures. Unfortunately, many mice do not live long with stem cell organs.

Most adult stem cells are lineage-restricted (multipotent) and are generally referred to by their tissue origin (mesenchymal stem cell
Mesenchymal stem cell
Mesenchymal stem cells, or MSCs, are multipotent stem cells that can differentiate into a variety of cell types, including: osteoblasts , chondrocytes and adipocytes...

, adipose-derived stem cell, endothelial stem cell, dental pulp stem cell, etc.).

Adult stem cell treatments have been successfully used for many years to treat leukemia and related bone/blood cancers through bone marrow transplants. Adult stem cells are also used in veterinary medicine to treat tendon and ligament injuries in horses.

The use of adult stem cells in research and therapy is not as controversial
Stem cell controversy
The stem cell controversy is the ethical debate primarily concerning the creation, treatment, and destruction of human embryos incident to research involving embryonic stem cells. Not all stem cell research involves the creation, use, or destruction of human embryos...

 as the use of embryonic stem cell
Embryonic stem cell
Embryonic stem cells are pluripotent stem cells derived from the inner cell mass of the blastocyst, an early-stage embryo. Human embryos reach the blastocyst stage 4–5 days post fertilization, at which time they consist of 50–150 cells...

s, because the production of adult stem cells does not require the destruction of an embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

. Additionally, in instances where adult stem cells are obtained from the intended recipient (an autograft), the risk of rejection is essentially non-existent. Consequently, more US government funding is being provided for adult stem cell research.

An extremely rich source for adult mesenchymal stem cells is the developing tooth bud of the mandibular third molar. The stem cells eventually form enamel (ectoderm), dentin, periodontal ligament, blood vessels, dental pulp, nervous tissues, and a minimum of 29 different end organs. Because of extreme ease in collection at 8–10 years of age before calcification and minimal to no morbidity, these will probably constitute a major source of cells for personal banking, research and current or future therapies. These stem cells have been shown capable of producing hepatocytes.

Amniotic


Multipotent stem cells are also found in amniotic fluid
Amniotic fluid
Amniotic fluid or liquor amnii is the nourishing and protecting liquid contained by the amniotic sac of a pregnant woman.- Development of amniotic fluid :...

. These stem cells are very active, expand extensively without feeders and are not tumorigenic. Amniotic stem cells
Amniotic stem cells
Amniotic stem cells are multipotent stem cells of mesenchymal origin extracted from amniotic fluid.Amniotic stem cells are able to differentiate into various tissue type such as skin, cartilage, cardiac tissue, nerves, muscle, and bone, and may have potential future medical applications.All over...

 are multipotent and can differentiate in cells of adipogenic, osteogenic, myogenic, endothelial, hepatic and also neuronal lines.
All over the world, universities and research institutes are studying amniotic fluid
Amniotic fluid
Amniotic fluid or liquor amnii is the nourishing and protecting liquid contained by the amniotic sac of a pregnant woman.- Development of amniotic fluid :...

 to discover all the qualities of amniotic stem cells, and scientists such as Anthony Atala
Anthony Atala
Anthony Atala, M.D., is the W.H. Boyce Professor and Director of the Wake Forest Institute for Regenerative Medicine, and Chair of the Department of Urology at the Wake Forest University School of Medicine in North Carolina...

 and Giuseppe Simoni
Giuseppe Simoni
Giuseppe Simoni is an Italian biologist and scientist. He was born in Pavia, Italy in 1944, and obtained his degree in biology at the University of Milan, where he later became a professor of genetics and biology for thirteen years....


have discovered important results.

Use of stem cells from amniotic fluid
Amniotic fluid
Amniotic fluid or liquor amnii is the nourishing and protecting liquid contained by the amniotic sac of a pregnant woman.- Development of amniotic fluid :...

 overcomes the ethical objections to using human embryos as a source of cells. Roman Catholic teaching forbids the use of embryonic stem cells in experimentation; accordingly, the Vatican
Holy See
The Holy See is the episcopal jurisdiction of the Catholic Church in Rome, in which its Bishop is commonly known as the Pope. It is the preeminent episcopal see of the Catholic Church, forming the central government of the Church. As such, diplomatically, and in other spheres the Holy See acts and...

 newspaper "Osservatore Romano" called amniotic stem cell "the future of medicine".

It is possible to collect amniotic stem cells for donors or for autologuous use: the first US amniotic stem cells bank opened in 2009 in Medford, MA, by Biocell Center
Biocell Center
Biocell Center is an international company specializing in the cryopreservation and private banking of amniotic fluid stem cells. The company is headquartered in Italy with several international locations and is involved with numerous partnerships and research studies of amniotic fluid stem...

 Corporation and collaborates with various hospitals and universities all over the world.

Induced pluripotent


These are not adult stem cells, but rather reprogrammed cells (e.g. epithelial cells) given pluripotent capabilities. Using genetic reprogramming with protein transcription factors, pluripotent stem cells equivalent to embryonic stem cells have been derived from human adult skin tissue. Shinya Yamanaka
Shinya Yamanaka
is a Japanese physician and adult stem cell researcher. He serves as the director of Center for iPS Cell Research and Application and a professor at the Institute for Frontier Medical Sciences at Kyoto University, as a senior investigator at the UCSF-affiliated J...

 and his colleagues at Kyoto University
Kyoto University
, or is a national university located in Kyoto, Japan. It is the second oldest Japanese university, and formerly one of Japan's Imperial Universities.- History :...

 used the transcription factors Oct3/4, Sox2, c-Myc, and Klf4 in their experiments on cells from human faces. Junying Yu
Junying Yu
Junying Yu, is an American stem cell biologist. She is currently a researcher at the University of Wisconsin–Madison.-Biography:Yu was born in 1975 in Zhejiang, China. In 1997, Yu graduated from the Department of Biology of Peking University in Beijing...

, James Thomson
James Thomson (cell biologist)
James Alexander Thomson is an American developmental biologist best known for deriving the first human embryonic stem cell line in 1998 and for deriving human induced pluripotent stem cells in 2007.-Thomson's research:...

, and their colleagues at the University of Wisconsin–Madison
University of Wisconsin–Madison
The University of Wisconsin–Madison is a public research university located in Madison, Wisconsin, United States. Founded in 1848, UW–Madison is the flagship campus of the University of Wisconsin System. It became a land-grant institution in 1866...

 used a different set of factors, Oct4, Sox2, Nanog and Lin28, and carried out their experiments using cells from human foreskin
Foreskin
In male human anatomy, the foreskin is a generally retractable double-layered fold of skin and mucous membrane that covers the glans penis and protects the urinary meatus when the penis is not erect...

.

As a result of the success of these experiments, Ian Wilmut
Ian Wilmut
Sir Ian Wilmut, OBE FRS FMedSci FRSE is an English embryologist and is currently Director of the Medical Research Council Centre for Regenerative Medicine at the University of Edinburgh. He is best known as the leader of the research group that in 1996 first cloned a mammal from an adult somatic...

, who helped create the first cloned animal Dolly the Sheep
Dolly the Sheep
Dolly was a female domestic sheep, and the first mammal to be cloned from an adult somatic cell, using the process of nuclear transfer. She was cloned by Ian Wilmut, Keith Campbell and colleagues at the Roslin Institute near Edinburgh in Scotland...

, has announced that he will abandon nuclear transfer
Nuclear transfer
Nuclear Transfer is a form of cloning. The steps involve removing the DNA from an oocyte , and injecting the nucleus which contains the DNA to be cloned. In rare instances, the newly constructed cell will divide normally, replicating the new DNA while remaining in a pluripotent state...

 as an avenue of research.

Frozen blood samples can be used as a source of induced pluripotent stem cells, opening a new avenue for obtaining the valued cells.

Lineage



To ensure self-renewal, stem cells undergo two types of cell division (see Stem cell division and differentiation diagram). Symmetric division gives rise to two identical daughter cells both endowed with stem cell properties. Asymmetric division, on the other hand, produces only one stem cell and a progenitor cell
Progenitor cell
A progenitor cell is a biological cell that, like a stem cell, has a tendency to differentiate into a specific type of cell, but is already more specific than a stem cell and is pushed to differentiate into its "target" cell...

 with limited self-renewal potential. Progenitors can go through several rounds of cell division before terminally differentiating into a mature cell. It is possible that the molecular distinction between symmetric and asymmetric divisions lies in differential segregation of cell membrane proteins (such as receptors
Receptor (biochemistry)
In biochemistry, a receptor is a molecule found on the surface of a cell, which receives specific chemical signals from neighbouring cells or the wider environment within an organism...

) between the daughter cells.

An alternative theory is that stem cells remain undifferentiated due to environmental cues in their particular niche. Stem cells differentiate when they leave that niche or no longer receive those signals. Studies in Drosophila germarium have identified the signals dpp and adherens junctions that prevent germarium stem cells from differentiating.
The signals that lead to reprogramming of cells to an embryonic-like state are also being investigated. These signal pathways include several transcription factor
Transcription factor
In molecular biology and genetics, a transcription factor is a protein that binds to specific DNA sequences, thereby controlling the flow of genetic information from DNA to mRNA...

s including the oncogene
Oncogene
An oncogene is a gene that has the potential to cause cancer. In tumor cells, they are often mutated or expressed at high levels.An oncogene is a gene found in the chromosomes of tumor cells whose activation is associated with the initial and continuing conversion of normal cells into cancer...

 c-Myc
Myc
Myc is a regulator gene that codes for a transcription factor. In the human genome, Myc is located on chromosome 8 and is believed to regulate expression of 15% of all genes through binding on Enhancer Box sequences and recruiting histone acetyltransferases...

. Initial studies indicate that transformation of mice cells with a combination of these anti-differentiation signals can reverse differentiation and may allow adult cells to become pluripotent. However, the need to transform these cells with an oncogene may prevent the use of this approach in therapy.

Challenging the terminal nature of cellular differentiation and the integrity of lineage commitment, it was recently determined that the somatic expression of combined transcription factor
Transcription factor
In molecular biology and genetics, a transcription factor is a protein that binds to specific DNA sequences, thereby controlling the flow of genetic information from DNA to mRNA...

s can directly induce other defined somatic cell fates; researchers identified three neural-lineage-specific transcription factors that could directly convert mouse fibroblasts (skin cells) into fully functional neuron
Neuron
A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...

s. This "induced neurons" (iN) cell research inspires the researchers to induce other cell types implies that all cells are totipotent: with the proper tools, all cells may form all kinds of tissue.

Treatments


Medical researchers believe that stem cell therapy has the potential to dramatically change the treatment of human disease. A number of adult stem cell therapies already exist, particularly bone marrow transplant
Bone marrow transplant
Hematopoietic stem cell transplantation is the transplantation of multipotent hematopoietic stem cell or blood, usually derived from bone marrow, peripheral blood stem cells, or umbilical cord blood...

s that are used to treat leukemia
Leukemia
Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...

. In the future, medical researchers anticipate being able to use technologies derived from stem cell research to treat a wider variety of diseases including cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

, Parkinson's disease
Parkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...

, spinal cord injuries, Amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis , also referred to as Lou Gehrig's disease, is a form of motor neuron disease caused by the degeneration of upper and lower neurons, located in the ventral horn of the spinal cord and the cortical neurons that provide their efferent input...

, multiple sclerosis
Multiple sclerosis
Multiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms...

, and muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

 damage, amongst a number of other impairments and conditions.
However, there still exists a great deal of social and scientific uncertainty surrounding stem cell research, which could possibly be overcome through public debate and future research, and further education of the public.

One concern of treatment is the risk that transplanted stem cells could form tumors and become cancerous if cell division continues uncontrollably.

Stem cells are widely studied, for their potential therapeutic use and for their inherent interest.

Supporters of embryonic stem cell research argue that such research should be pursued because the resultant treatments could have significant medical potential. It has been proposed that surplus embryos created for in vitro fertilization could be donated with consent and used for the research.

The recent development of iPS cells has been called a bypass of the legal controversy. Laws limiting the destruction of human embryos have been credited for being the reason for development of iPS cells, but it is still not completely clear whether hiPS cells are equivalent to hES cells. Recent work demonstrates hotspots of aberrant epigenomic reprogramming in hiPS cells (Lister, R., et al., 2011).

Research patents


The patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....

s covering a lot of work on human embryonic stem cells are owned by the Wisconsin Alumni Research Foundation
Wisconsin Alumni Research Foundation
The Wisconsin Alumni Research Foundation is the nonprofit technology transfer office of the University of Wisconsin–Madison. It is a significant source of research support, independent of federal grants...

 (WARF). WARF does not charge academics to study human stem cells but does charge commercial users. WARF sold Geron Corp.
Geron Corp.
Geron Corporation is a biotechnology company located in Menlo Park, California that specializes in developing and commercialization of products in three specific areas: 1) therapeutic products for cancer that inhibit telomerase; 2) pharmaceuticals that activate telomerase in tissues impacted by...

 exclusive rights to work on human stem cells but later sued Geron Corp. to recover some of the previously sold rights. The two sides agreed that Geron Corp. would keep the rights to only three cell types. In 2001, WARF came under public pressure to widen access to human stem-cell technology.

A request for reviewing the WARF patents 5,843,780; 6,200,806; 7,029,913 US Patent and Trademark Office were filed by non-profit patent-watchdogs The Foundation for Taxpayer & Consumer Rights, and the Public Patent Foundation
Public Patent Foundation
Public Patent Foundation, or PUBPAT, is a nonprofit organization that seeks to limit perceived abuse of the United States patent system. It was founded in 2003 by Dan Ravicher. , there was growing concern by many technology professionals over the number of patents granted that are either too...

  as well as molecular biologist Jeanne Loring of the Burnham Institute. According to them, two of the patents granted to WARF are invalid because they cover a technique published in 1993 for which a patent had already been granted to an Australian researcher. Another part of the challenge states that these techniques, developed by James A. Thomson
James Thomson (cell biologist)
James Alexander Thomson is an American developmental biologist best known for deriving the first human embryonic stem cell line in 1998 and for deriving human induced pluripotent stem cells in 2007.-Thomson's research:...

, are rendered obvious by a 1990 paper and two textbooks. Based on this challenge, patent 7,029,913 has been rejected in 2010. The two remaining hES WARF patents are due to expire in 2015.

The outcome of this legal challenge is particularly relevant to the Geron Corp. as it can only license patents that are upheld.

Key research events

  • 1908: The term "stem cell" was proposed for scientific use by the Russia
    Russia
    Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

    n histologist Alexander Maksimov (1874–1928) at congress of hematologic society in Berlin
    Berlin
    Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...

    . It postulated existence of haematopoietic stem cells.
  • 1960s: Joseph Altman
    Joseph Altman
    Joseph Altman discovered adult neurogenesis, the creation of new neurons in the adult brain, in the 1960s. As an independent investigator at MIT, his results were largely ignored. In the late 1990s, the fact that the brain can create new neurons even into adulthood was rediscovered, leading it to...

     and Gopal Das present scientific evidence of adult neurogenesis
    Neurogenesis
    Neurogenesis is the process by which neurons are generated from neural stem and progenitor cells. Most active during pre-natal development, neurogenesis is responsible for populating the growing brain with neurons. Recently neurogenesis was shown to continue in several small parts of the brain of...

    , ongoing stem cell activity in the brain; like André Gernez
    André Gernez
    André Gernez is a French non-conventional physician. He created a global non-governmental organisation Organic Union International in 1989 with doctors Jacques Lacaze and Jean-Pierre Willem....

    , their reports contradict Cajal
    Santiago Ramón y Cajal
    Santiago Ramón y Cajal ForMemRS was a Spanish pathologist, histologist, neuroscientist, and Nobel laureate. His pioneering investigations of the microscopic structure of the brain were original: he is considered by many to be the father of modern neuroscience...

    's "no new neurons" dogma and are largely ignored.
  • 1963: McCulloch
    Ernest McCulloch
    Ernest Armstrong McCulloch, OC, O.Ont, FRSC was a University of Toronto cellular biologist, best known for demonstrating – with James Till – the existence of stem cells.-Biography:...

     and Till
    James Till
    James Edgar Till, OC, O.Ont, FRSC is a University of Toronto biophysicist, best known for demonstrating – with Ernest McCulloch – the existence of stem cells.-Early work:...

     illustrate the presence of self-renewing cells in mouse bone marrow.
  • 1968: Bone marrow
    Bone marrow
    Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...

     transplant
    Organ transplant
    Organ transplantation is the moving of an organ from one body to another or from a donor site on the patient's own body, for the purpose of replacing the recipient's damaged or absent organ. The emerging field of regenerative medicine is allowing scientists and engineers to create organs to be...

     between two siblings successfully treats SCID
    Severe combined immunodeficiency
    Severe combined immunodeficiency , is a genetic disorder in which both "arms" of the adaptive immune system are impaired due to a defect in one of several possible genes. SCID is a severe form of heritable immunodeficiency...

    .
  • 1978: Haematopoietic stem cells are discovered in human cord blood
    Cord blood
    Umbilical cord blood is blood that remains in the placenta and in the attached umbilical cord after childbirth. Cord blood is collected because it contains stem cells which can be used to treat hematopoietic and genetic disorders.-Collection:...

    .
  • 1981: Mouse embryonic stem cell
    Embryonic stem cell
    Embryonic stem cells are pluripotent stem cells derived from the inner cell mass of the blastocyst, an early-stage embryo. Human embryos reach the blastocyst stage 4–5 days post fertilization, at which time they consist of 50–150 cells...

    s are derived from the inner cell mass
    Inner cell mass
    In early embryogenesis of most eutherian mammals, the inner cell mass is the mass of cells inside the primordial embryo that will eventually give rise to the definitive structures of the fetus...

     by scientists Martin Evans
    Martin Evans
    Sir Martin John Evans FRS is a British scientist who, with Matthew Kaufman, was the first to culture mice embryonic stem cells and cultivate them in a laboratory in 1981...

    , Matthew Kaufman
    Matthew Kaufman
    Matthew H. Kaufman is Professor Emeritus at University of Edinburgh having been Professor of Anatomy there from 1985–2007. He has taught anatomy and embryology for more than 30 years, initially at the University of Cambridge, when he was a Fellow of King’s College, and more recently in...

    , and Gail R. Martin
    Gail R. Martin
    Professor Gail R. Martin, is in charge of the developmental biology program at the University of California, San Francisco. She is a member of the American Academy of Arts & Sciences, a member of the National Academy of Sciences , and is the President of the Society for Developmental Biology.In...

    . Gail Martin is attributed for coining the term "Embryonic Stem Cell".
  • 1992: Neural stem cells are cultured in vitro
    In vitro
    In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...

    as neurospheres.
  • 1997: Leukemia is shown to originate from a haematopoietic stem cell, the first direct evidence for cancer stem cell
    Cancer stem cell
    Cancer stem cells are cancer cells 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 , perhaps in contrast to other non-tumorigenic cancer cells...

    s.
  • 1998: James Thomson
    James Thomson (cell biologist)
    James Alexander Thomson is an American developmental biologist best known for deriving the first human embryonic stem cell line in 1998 and for deriving human induced pluripotent stem cells in 2007.-Thomson's research:...

     and coworkers derive the first human embryonic stem cell line
    Stem cell line
    A stem cell line is a family of constantly dividing cells, the product of a single group of stem cells. They are obtained from human or animal tissues and can replicate for long periods of time in vitro...

     at the University of Wisconsin–Madison
    University of Wisconsin–Madison
    The University of Wisconsin–Madison is a public research university located in Madison, Wisconsin, United States. Founded in 1848, UW–Madison is the flagship campus of the University of Wisconsin System. It became a land-grant institution in 1866...

    .
  • 1998: John Gearhart (Johns Hopkins University) extracted germ cells from fetal gonadal tissue (primordial germ cells) before developing pluripotent stem cell lines from the original extract.
  • 2000s: Several reports of adult stem cell
    Adult stem cell
    Adult stem cells are undifferentiated cells, found throughout the body after embryonic development, that multiply by cell division to replenish dying cells and regenerate damaged tissues...

     plasticity are published.
  • 2001: Scientists at Advanced Cell Technology
    Advanced Cell Technology
    Advanced Cell Technology, Incorporated , is a biotechnology company located in Marlborough, Massachusetts, USA. The company specializes in the development and commercialization of cell therapies for the treatment of a variety of diseases...

     clone first early (four- to six-cell stage) human embryos for the purpose of generating embryonic stem cells.
  • 2003: Dr. Songtao Shi of NIH discovers new source of adult stem cells in children's primary teeth.
  • 2004–2005: Korean researcher Hwang Woo-Suk
    Hwang Woo-Suk
    Hwang Woo-suk is a South Korean veterinarian and researcher. He was a professor of theriogenology and biotechnology at Seoul National University who became infamous for fabricating a series of experiments, which appeared in high-profile journals, in the field of stem cell research...

     claims to have created several human embryonic stem cell
    Embryonic stem cell
    Embryonic stem cells are pluripotent stem cells derived from the inner cell mass of the blastocyst, an early-stage embryo. Human embryos reach the blastocyst stage 4–5 days post fertilization, at which time they consist of 50–150 cells...

     lines from unfertilised human oocyte
    Oocyte
    An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...

    s. The lines were later shown to be fabricated.
  • 2005: Researchers at Kingston University
    Kingston University
    Kingston University is a public research university located in Kingston upon Thames, southwest London, United Kingdom. It was originally founded in 1899 as Kingston Technical Institute, a polytechnic, and became a university in 1992....

     in England
    England
    England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

     claim to have discovered a third category of stem cell, dubbed cord-blood-derived embryonic-like stem cells (CBEs), derived from umbilical cord blood. The group claims these cells are able to differentiate into more types of tissue than adult stem cells.
  • 2005: Researchers at UC Irvine's Reeve-Irvine Research Center are able to partially restore the ability of rats with paralyzed spines to walk through the injection of human neural stem cells.
  • August 2006: Mouse Induced pluripotent stem cell
    Induced pluripotent stem cell
    Induced pluripotent stem cells, commonly abbreviated as iPS cells or iPSCs are a type of pluripotent stem cell artificially derived from a non-pluripotent cell, typically an adult somatic cell, by inducing a "forced" expression of specific genes....

    s: the journal Cell
    Cell (journal)
    Cell is a peer-reviewed scientific journal publishing research papers across a broad range of disciplines within the life sciences. Areas covered include molecular biology, cell biology, systems biology, stem cells, developmental biology, genetics and genomics, proteomics, cancer research,...

     publishes Kazutoshi Takahashi and Shinya Yamanaka
    Shinya Yamanaka
    is a Japanese physician and adult stem cell researcher. He serves as the director of Center for iPS Cell Research and Application and a professor at the Institute for Frontier Medical Sciences at Kyoto University, as a senior investigator at the UCSF-affiliated J...

    .
  • October 2006: Scientists at Newcastle University in England create the first ever artificial liver cells using umbilical cord blood stem cells.
  • January 2007: Scientists at Wake Forest University
    Wake Forest University
    Wake Forest University is a private, coeducational university in the U.S. state of North Carolina, founded in 1834. The university received its name from its original location in Wake Forest, north of Raleigh, North Carolina, the state capital. The Reynolda Campus, the university's main campus, is...

     led by Dr. Anthony Atala
    Anthony Atala
    Anthony Atala, M.D., is the W.H. Boyce Professor and Director of the Wake Forest Institute for Regenerative Medicine, and Chair of the Department of Urology at the Wake Forest University School of Medicine in North Carolina...

     and Harvard University
    Harvard University
    Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...

     report discovery of a new type of stem cell in amniotic fluid
    Amniotic fluid
    Amniotic fluid or liquor amnii is the nourishing and protecting liquid contained by the amniotic sac of a pregnant woman.- Development of amniotic fluid :...

    . This may potentially provide an alternative to embryonic stem cells for use in research and therapy.
  • June 2007: Research reported by three different groups shows that normal skin cells can be reprogrammed to an embryonic state in mice. In the same month, scientist Shoukhrat Mitalipov reports the first successful creation of a primate stem cell line through somatic cell nuclear transfer
    Somatic cell nuclear transfer
    In genetics and developmental biology, somatic-cell nuclear transfer is a laboratory technique for creating a clonal embryo, using an ovum with a donor nucleus . It can be used in embryonic stem cell research, or, potentially, in regenerative medicine where it is sometimes referred to as...

  • October 2007: Mario Capecchi
    Mario Capecchi
    Mario Renato Capecchi is an Italian-born American molecular geneticist and a co-winner of the 2007 Nobel Prize in Physiology or Medicine for discovering a method for introducing homologous recombination in mice employing embryonic stem cells, with Martin Evans and Oliver Smithies...

    , Martin Evans
    Martin Evans
    Sir Martin John Evans FRS is a British scientist who, with Matthew Kaufman, was the first to culture mice embryonic stem cells and cultivate them in a laboratory in 1981...

    , and Oliver Smithies
    Oliver Smithies
    Oliver Smithies is a British-born American geneticist and Nobel laureate, credited with the invention of gel electrophoresis in 1955, and the simultaneous discovery, with Mario Capecchi and Martin Evans, of the technique of homologous recombination of transgenic DNA with genomic DNA, a much more...

     win the 2007 Nobel Prize for Physiology or Medicine for their work on embryonic stem cells from mice using gene targeting strategies producing genetically engineered mice (known as knockout mice) for gene research.
  • November 2007: Human induced pluripotent stem cell
    Induced pluripotent stem cell
    Induced pluripotent stem cells, commonly abbreviated as iPS cells or iPSCs are a type of pluripotent stem cell artificially derived from a non-pluripotent cell, typically an adult somatic cell, by inducing a "forced" expression of specific genes....

    s: Two similar papers released by their respective journals prior to formal publication: in Cell
    Cell (journal)
    Cell is a peer-reviewed scientific journal publishing research papers across a broad range of disciplines within the life sciences. Areas covered include molecular biology, cell biology, systems biology, stem cells, developmental biology, genetics and genomics, proteomics, cancer research,...

     by Kazutoshi Takahashi and Shinya Yamanaka
    Shinya Yamanaka
    is a Japanese physician and adult stem cell researcher. He serves as the director of Center for iPS Cell Research and Application and a professor at the Institute for Frontier Medical Sciences at Kyoto University, as a senior investigator at the UCSF-affiliated J...

    , "Induction of pluripotent stem cells from adult human fibroblasts by defined factors", and in Science by Junying Yu
    Junying Yu
    Junying Yu, is an American stem cell biologist. She is currently a researcher at the University of Wisconsin–Madison.-Biography:Yu was born in 1975 in Zhejiang, China. In 1997, Yu graduated from the Department of Biology of Peking University in Beijing...

    , et al., from the research group of James Thomson
    James Thomson (cell biologist)
    James Alexander Thomson is an American developmental biologist best known for deriving the first human embryonic stem cell line in 1998 and for deriving human induced pluripotent stem cells in 2007.-Thomson's research:...

    , "Induced pluripotent stem cell lines derived from human somatic cells": pluripotent stem cells generated from mature human fibroblasts. It is possible now to produce a stem cell from almost any other human cell instead of using embryos as needed previously, albeit the risk of tumorigenesis due to c-myc and retroviral gene transfer remains to be determined.
  • January 2008: Robert Lanza and colleagues at Advanced Cell Technology and UCSF create the first human embryonic stem cells without destruction of the embryo
  • January 2008: Development of human cloned blastocysts following somatic cell nuclear transfer
    Somatic cell nuclear transfer
    In genetics and developmental biology, somatic-cell nuclear transfer is a laboratory technique for creating a clonal embryo, using an ovum with a donor nucleus . It can be used in embryonic stem cell research, or, potentially, in regenerative medicine where it is sometimes referred to as...

     with adult fibroblasts
  • February 2008: Generation of pluripotent stem cells from adult mouse liver and stomach: these iPS cells seem to be more similar to embryonic stem cells than the previously developed iPS cells and not tumorigenic, moreover genes that are required for iPS cells do not need to be inserted into specific sites, which encourages the development of non-viral reprogramming techniques.
  • March 2008-The first published study of successful cartilage regeneration in the human knee using autologous adult mesenchymal stem cells is published by clinicians from Regenerative Sciences
  • October 2008: Sabine Conrad and colleagues at Tübingen, Germany generate pluripotent stem cells from spermatogonial cells of adult human testis by culturing the cells in vitro under leukemia inhibitory factor
    Leukemia inhibitory factor
    Leukemia inhibitory factor, or LIF, an interleukin 6 class cytokine, is a protein in cells that affects cell growth and development.-Function:LIF derives its name from its ability to induce the terminal differentiation of myeloid leukemic cells...

     (LIF) supplementation.
  • 30 October 2008: Embryonic-like stem cells from a single human hair.
  • 1 March 2009: Andras Nagy, Keisuke Kaji, et al. discover a way to produce embryonic-like stem cells from normal adult cells by using a novel "wrapping" procedure to deliver specific genes to adult cells to reprogram them into stem cells without the risks of using a virus to make the change. The use of electroporation
    Electroporation
    Electroporation, or electropermeabilization, is a significant increase in the electrical conductivity and permeability of the cell plasma membrane caused by an externally applied electrical field...

     is said to allow for the temporary insertion of genes into the cell.
  • 28 May 2009 Kim et al. announced that they had devised a way to manipulate skin cells to create patient specific "induced pluripotent stem cells" (iPS), claiming it to be the 'ultimate stem cell solution'.
  • 11 October 2010 First trial of embryonic stem cells in humans.
  • 25 October 2010: Ishikawa et al. write in the Journal of Experimental Medicine that research shows that transplanted cells that contain their new host's nuclear DNA could still be rejected by the invidual's immune system due to foreign mitochondrial DNA
    Mitochondrial DNA
    Mitochondrial DNA is the DNA located in organelles called mitochondria, structures within eukaryotic cells that convert the chemical energy from food into a form that cells can use, adenosine triphosphate...

    . Tissues made from a person's stem cells could therefore be rejected, because mitochondrial genomes tend to accumulate mutations.
  • 2011: Israel
    Israel
    The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...

    i scientist Inbar Friedrich Ben-Nun led a team which produced the first stem cells from endangered species, a breakthrough that could save animals in danger of extinction.

See also

  • Neural stem cell
    Neural stem cell
    Neural stem cells are the self-renewing, multipotent cells that generate the main phenotypes of the nervous system. In 1989, Sally Temple described multipotent, self-renewing progenitor and stem cells in the subventricular zone of the mouse brain . In 1992, Brent A...

  • Cancer stem cell
    Cancer stem cell
    Cancer stem cells are cancer cells 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 , perhaps in contrast to other non-tumorigenic cancer cells...

  • Stem cell controversy
    Stem cell controversy
    The stem cell controversy is the ethical debate primarily concerning the creation, treatment, and destruction of human embryos incident to research involving embryonic stem cells. Not all stem cell research involves the creation, use, or destruction of human embryos...

  • Dental pulp stem cells
    Dental pulp stem cells
    Dental Pulp Stem Cells, or are multipotent stem cells that have the potential to differentiate into a variety of cell types.More recently a subpopulation of dental pulp stem cells has been described as human Immature Dental Pulp Stem Cells .-Definition:Dental pulp is the soft living tissue inside...

  • Human genome
    Human genome
    The human genome is the genome of Homo sapiens, which is stored on 23 chromosome pairs plus the small mitochondrial DNA. 22 of the 23 chromosomes are autosomal chromosome pairs, while the remaining pair is sex-determining...

  • Induced Pluripotent Stem Cell
    Induced pluripotent stem cell
    Induced pluripotent stem cells, commonly abbreviated as iPS cells or iPSCs are a type of pluripotent stem cell artificially derived from a non-pluripotent cell, typically an adult somatic cell, by inducing a "forced" expression of specific genes....

     (iPS Cell)
  • Meristem
    Meristem
    A meristem is the tissue in most plants consisting of undifferentiated cells , found in zones of the plant where growth can take place....

  • Partial cloning
    Partial cloning
    In the field of cell biology, the method of partial cloning converts a fully differentiated old somatic cell into a partially reprogrammed young cell that retains all the specialised functions of the differentiated old cell but is simply younger. The method of PCL reverses characteristics...

  • Plant stem cells
    Plant stem cells
    Plant stem cells are innately undifferentiated cells located in the meristems of plant. Plant stem cells serve as the origin of plant vitality, as they maintain themselves while providing a steady supply of precursor cells to form differentiated tissues and organs in plant.-Characteristics:Plant...

  • Stem cell marker
    Stem cell marker
    Stem cell markers are genes and their protein products used by scientists to isolate and identify stem cells. Stem cells can also be identified by functional assays. Below is a list of genes/protein products that can be used to identify various types of stem cells, or functional assays that do the...

  • Stem Cell Network
    Stem Cell Network
    The Stem Cell Network is a not-for-profit corporation founded in 2001. SCN funds applied stem cell research in Canada and facilitates collaboration between universities, industry, government and non-governmental organizations....

  • Boyd Melson
    Boyd Melson
    Boyd "Rainmaker" Melson is an American light middleweight boxer.As an amateur, Melson won the 48th World Military Boxing Championship gold medal in the 69 kg. weight class, and was a four-time United States Army champion, a three-time NCBA All-American boxer, a four-time West Point Brigade...

    , boxer who donates all his earnings to stem cell research
  • Cell bank
    Cell bank
    A cell bank is a facility that stores cells of specific genetic lines for the purpose of future use in a product or medicinal needs. They often contain expansive amounts of base cell material that can be utilized for various projects...


External links


General

Peer-reviewed journals