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In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change 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.
Transdifferentiation, 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. The term 'transdifferentiation' was originally coined by Selman and Kafatos in 1974 to describe a change in cell properties as cuticle producing cells became salt-secreting cells in silk moths undergoing metamorphosis.
Cellular differentiation is the process in which a stem cell changes from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types. Differentiation continues in adulthood as adult stem cells divide and create fully differentiated daughter cells during tissue repair and during normal cell turnover. Some differentiation occurs in response to antigen exposure. Differentiation dramatically changes a cell's size, shape, membrane potential, metabolic activity, and responsiveness to signals. These changes are largely due to highly controlled modifications in gene expression and are the study of epigenetics. With a few exceptions, cellular differentiation almost never involves a change in the DNA sequence itself. Metabolic composition, however, gets dramatically altered where stem cells are characterized by abundant metabolites with highly unsaturated structures whose levels decrease upon differentiation. Thus, different cells can have very different physical characteristics despite having the same genome.
In genetics and developmental biology, somatic cell nuclear transfer (SCNT) is a laboratory strategy for creating a viable embryo from a body cell and an egg cell. The technique consists of taking a denucleated oocyte and implanting a donor nucleus from a somatic (body) cell. It is used in both therapeutic and reproductive cloning. In 1996, Dolly the sheep became famous for being the first successful case of the reproductive cloning of a mammal. In January 2018, a team of scientists in Shanghai announced the successful cloning of two female crab-eating macaques from foetal nuclei.
Embryonic 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.
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. It is critically involved in the self-renewal of undifferentiated embryonic stem cells. As such, it is frequently used as a marker for undifferentiated cells. Oct-4 expression must be closely regulated; too much or too little will cause differentiation of the cells.
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 (iPS) in 2007.
The stem cell controversy concerns 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. Many less controversial sources of acquiring stem cells include using cells from the umbilical cord, breast milk, and bone marrow, which are not pluripotent.
Rudolf Jaenisch is a Professor of Biology at MIT and a founding member of the Whitehead Institute for Biomedical Research. He is a pioneer of transgenic science, in which an animal’s genetic makeup is altered. Jaenisch has focused on creating genetically modified mice to study cancer, epigenetic reprogramming and neurological diseases.
In biology and medicine, stem cell genomics is the analysis of the genomes of stem cells. Currently, this field is rapidly expanding due to the dramatic decrease in the cost of sequencing genomes. The study of stem cell genomics has wide reaching implications in the study of stem cell biology and possible therapeutic usages of stem cells.
Induced pluripotent stem cells 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, collectively known as Yamanaka factors, encoding transcription factors could convert somatic cells into pluripotent stem cells. Shinya Yamanaka was awarded the 2012 Nobel Prize along with Sir John Gurdon "for the discovery that mature cells can be reprogrammed to become pluripotent."
Kevin Eggan is a Professor of Stem Cell and Regenerative Biology at Harvard University, known for his work in stem cell research, and as a spokesperson for stem cell research in the United States. He was a 2006 recipient of a MacArthur Fellowship. In 2005, he was named to the MIT Technology Review TR35 as one of the top 35 innovators in the world under the age of 35.
Shinya Yamanaka is a Japanese stem cell researcher and a Nobel Prize laureate. He is a professor and the director emeritus of Center for iPS Cell Research and Application, Kyoto University; as a senior investigator at the UCSF-affiliated Gladstone Institutes in San Francisco, California; and as a professor of anatomy at University of California, San Francisco (UCSF). Yamanaka is also a past president of the International Society for Stem Cell Research (ISSCR).
Janet Rossant, is a developmental biologist well known for her contributions to the understanding of the role of genes in embryo development. She is a world renowned leader in developmental biology. Her current research interests focus on stem cells, molecular genetics, and developmental biology. Specifically, she uses cellular and genetic manipulation techniques to study how genes control both normal and abnormal development of early mouse embryos. Rossant has discovered information on embryo development, how multiple types of stem cells are established, and the mechanisms by which genes control development. In 1998, her work helped lead to the discovery of the trophoblast stem cell, which has assisted in showing how congenital anomalies in the heart, blood vessels, and placenta can occur.
Zeng Fanyi is a Chinese stem cell scientist and professor at Shanghai Jiao Tong University (SJTU) medical school.
Cell 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.
The Stem Cell Lineage Database (SCLD) is a database of resources used to identify cell lineages.
A knockout mouse, or knock-out mouse, is a genetically modified mouse in which researchers have inactivated, or "knocked out", an existing gene by replacing it or disrupting it with an artificial piece of DNA. They are important animal models for studying the role of genes which have been sequenced but whose functions have not been determined. By causing a specific gene to be inactive in the mouse, and observing any differences from normal behaviour or physiology, researchers can infer its probable function.
Stimulus-triggered acquisition of pluripotency (STAP) was a proposed method of generating pluripotent stem cells by subjecting ordinary cells to certain types of stress, such as the application of a bacterial toxin, submersion in a weak acid, or physical trauma. The technique gained prominence in January 2014 when research by Haruko Obokata et al. was published in Nature. Over the following months, all scientists who tried to duplicate her results failed, and suspicion arose that Obokata's results were due to error or fraud. An investigation by her employer, RIKEN, was launched. On April 1, 2014, RIKEN concluded that Obokata had falsified data to obtain her results. On June 4, 2014, Obokata agreed to retract the papers. On August 5, 2014, Yoshiki Sasai—Obokata's supervisor at RIKEN and one of the coauthors on the STAP cell papers—was found dead at a RIKEN facility after an apparent suicide by hanging.
Regeneration in humans is the regrowth of lost tissues or organs in response to injury. This is in contrast to wound healing, or partial regeneration, which involves closing up the injury site with some gradation of scar tissue. Some tissues such as skin, the vas deferens, and large organs including the liver can regrow quite readily, while others have been thought to have little or no capacity for regeneration following an injury.
References
- ↑ Linzhao Cheng, Lei Xiao, Fanyi Zeng and Alex Zhang, 10 January 2008, Stem Cells Shine in Shanghai
- ↑ Naik, Gautam (July 24, 2009). "Chinese Scientists Reprogram Cells to Create Mice". The Wall Street Journal . Retrieved 2024-08-29.
- ↑ Park, Alice (2009-07-23). "Scientists Grow Mice from New Kind of Stem Cell - TIME". TIME . Archived from the original on 2009-07-26. Retrieved 2024-08-29.
- 1 2 Mice Made From Mouse Skin Cells: Chinese Studies Confirm Potential of Skin Cells Reprogrammed to Act Like Embryonic Stem Cells - WebMD
- 1 2 Mice pups bred from adult stem cells - Australian Broadcasting Corporation