Shortly after John Gearhart's amazing discovery of isolating and growing embryonic stem cells in culture, he made the following prediction, "The potential of these unique, versatile cells for human biologic studies and medicine is enormous". In fact, many have
underestimated the potential stem cells could have in the world of biological research and medicine. The idea of a pluri-potent cell that has the ability to divide and differentiate into any type of cell in the body provides infinite research possibilities with direct applications to pressing medical problems. An interesting aspect of stem cell biology lies in the process of stem cell self-renewal. This process is necessary to maintain stem cells as well as regulate hyperproliferation. As noted by Kiger et al, there are two ways in which systems maintain proper stem cell numbers. The first is by asymmetric division in which one cell remains a stem cell, while the other differentiates. Another mechanism is to maintain stem cells through symmetric stem cell division, which is common after a wound or transplantation (Kiger, et. al2001). Stem cell self-renewal is a critical process in the maintenance of blood, skin, sperm, and many other cells. The potential for therapeutics based on understanding stem cell self renewal is very promising. However the signaling pathways and biological characteristics of the system must be well understood to fully exploit stem cell potential in medicine.
[...] Characterizing this niche could play a very important role in ultimately using stem cell therapy/manipulation for treating diseases or injuries to the brain/nervous system. The methods discussed above to characterize the hippocampus niche could also be applied to other tissue stem cell populations to understand their initiating ligands and signaling pathways. The process of stem cell self-renewal is a basic biological process that if understood better could provide many answers to injury and disease and provide therapies to treat them. [...]
[...] elegans or cell culture model with hippocampus stem cells could be used to evaluate stem cell factors and signaling pathways in these cells.To characterize further the niche in the hippocampus, the genes responsible for the maintenance of the stem cell self-renewal should be understood. One approach to understand signaling would involve identifying the genes that code for proteins that are involved in the stem cell renewal as well as the cell differentiation signaling pathway. This could be accomplished by the use microarrays to measure gene expression differences in stem cells in an ‘activated' versus resting state. [...]
[...] In this particular case, the apical tip of Drosophilae testes acts as a niche for stem cell self-renewal(Tulina, Matunis 2001). Dr. Matunis stressed that the identification of this particular niche was somewhat by chance and that very few niches have actually been discovered and characterized to the extent of that in Drosophilae spermatogenesis. Stem Cell Hubs in the Brain? Song, et al. of The Salk Institute for Biological Studies have recently discovered that contrary to prior belief, new nerve cells arise in different parts of the brain throughout life. [...]
[...] al found that in the hippocampus, it is in fact astrocytes that are responsible for maintaining stem cell self-renewal as well as directing the differentiation of the stem cells into functioning neurons. Song et al notes that, astrocytes appeared to work by increasing the rate of proliferation of the stem cells and steering their progeny towards becoming neurons'(Song et. al, 2002). The findings of Song et al and their idea of glial cells acting as a microenvironment and sending signals to stem cells are very similar to Matunis' results and the idea of a stem cell niche. [...]
[...] One way to begin to test this hypothesis would be to make antibodies to the ligand (assuming one now knows the ligand responsible for stem cell renewal in the brain) and conduct immunohistochemistry on brain tissue to determine if spatial gradients of ligand concentration are associated with astrocyte hubs and whether the gradient is consistent with the cell differentiation activity as cells move away from the hub region. In vitro studies with stem cell populations and the stem cell renewal ligand could also be conducted to determine the concentration of the ligand required to maintain stem characteristics in the cells. [...]
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