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.
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.
Hair cells are the sensory receptors of both the auditory system and the vestibular system in the ears of all vertebrates, and in the lateral line organ of fishes. Through mechanotransduction, hair cells detect movement in their environment.
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.
Spermidine is a polyamine compound found in ribosomes and living tissues and having various metabolic functions within organisms.
Myc is a family of regulator genes and proto-oncogenes that code for transcription factors. The Myc family consists of three related human genes: c-myc (MYC), l-myc (MYCL), and n-myc (MYCN). c-myc was the first gene to be discovered in this family, due to homology with the viral gene v-myc.
Margatoxin (MgTX) is a peptide that selectively inhibits Kv1.3 voltage-dependent potassium channels. It is found in the venom of Centruroides margaritatus, also known as the Central American Bark Scorpion. Margatoxin was first discovered in 1993. It was purified from scorpion venom and its amino acid sequence was determined.
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."
Telomerase reverse transcriptase is a catalytic subunit of the enzyme telomerase, which, together with the telomerase RNA component (TERC), comprises the most important unit of the telomerase complex.
Krüppel-like factor 4 is a member of the KLF family of zinc finger transcription factors, which belongs to the relatively large family of SP1-like transcription factors. KLF4 is involved in the regulation of proliferation, differentiation, apoptosis and somatic cell reprogramming. Evidence also suggests that KLF4 is a tumor suppressor in certain cancers, including colorectal cancer. It has three C2H2-zinc fingers at its carboxyl terminus that are closely related to another KLF, KLF2. It has two nuclear localization sequences that signals it to localize to the nucleus. In embryonic stem cells (ESCs), KLF4 has been demonstrated to be a good indicator of stem-like capacity. It is suggested that the same is true in mesenchymal stem cells (MSCs).
Mesenchymal 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, chondrocytes, myocytes and adipocytes.
SB-431542 is a drug candidate developed by GlaxoSmithKline (GSK) as an inhibitor of the activin receptor-like kinase (ALK) receptors, ALK5, ALK4 and ALK7. However, it is not an inhibitor of anaplastic lymphoma kinase.
Linifanib (ABT-869) is a structurally novel, potent inhibitor of receptor tyrosine kinases (RTK), vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) with IC50 of 0.2, 2, 4, and 7 nM for human endothelial cells, PDGF receptor beta (PDGFR-β), KDR, and colony stimulating factor 1 receptor (CSF-1R), respectively. It has much less activity (IC50s > 1 μM) against unrelated RTKs, soluble tyrosine kinases, or serine/threonine kinases. In vivo linifanib is effective orally in mechanism-based murine models of VEGF-induced uterine edema (ED50 = 0.5 mg/kg) and corneal angiogenesis (>50%inhibition, 15 mg/kg).
The STAT3-Ser/Hes3 signaling axis is a specific type of intracellular signaling pathway that regulates several fundamental properties of cells.
Glis1 is gene encoding a Krüppel-like protein of the same name whose locus is found on Chromosome 1p32.3. The gene is enriched in unfertilised eggs and embryos at the one cell stage and it can be used to promote direct reprogramming of somatic cells to induced pluripotent stem cells, also known as iPS cells. Glis1 is a highly promiscuous transcription factor, regulating the expression of numerous genes, either positively or negatively. In organisms, Glis1 does not appear to have any directly important functions. Mice whose Glis1 gene has been removed have no noticeable change to their phenotype.
Epigenetic regulation of neurogenesis is the role that epigenetics plays in the regulation of neurogenesis.
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.
Inner ear regeneration is the biological process by which the hair cells and supporting cells of the ear proliferate and regrow after hair cell injury. This process depends on communication between supporting cells and the brain. Because of the volatility of the inner ear's hair cells, regeneration is crucial to the functioning of the inner ear. It is also a limited process, which contributes to the irreversibility of hearing loss in humans and other mammals.
Thiazovivin is a drug which acts as a potent and selective inhibitor of the enzyme Rho kinase. It is used alongside a cocktail of other growth factors and modulators in cell culture techniques for the generation of induced pluripotent stem cells, which can then be used for a wide variety of applications.
RepSox is a small molecule inhibitor of TGFβR1, also known as ALK5, that was first identified in the wake of the discovery of the Yamanaka factors. It has shown promise in a variety of in-vitro and in-vivo rodent trials modelling various diseases. It inhibits TGFβR1 autophosphorylation by preventing the protein from binding with ATP, inhibits the binding of TGF-β to TGFβR1, and prevents the transcription of genes activated by TGFβR1 with nanomolar potency. RepSox is a member of the 1,5-naphthyridine class.
