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group_5_presentation_1_-_regeneration_stem_cells [2019/01/31 19:39] smithl12 |
group_5_presentation_1_-_regeneration_stem_cells [2019/02/01 17:37] (current) smithl12 |
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| + | ========Regeneration and Stem Cells======== | ||
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| + | ======1. Introduction to Regeneration====== | ||
| + | Regeneration is a fascinating concept among us humans; the thought of amputated limbs growing back into fully functioning body parts has long been popularized in cartoons and fictional characters. For instance, Piccolo, a character from Dragon Ball Z is popular for its remarkable regenerative capability. | ||
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| + | {{ :dragonball.gif?nolink&300 |}} | ||
| + | Figure 1. Cartoon character, Piccolo, displaying regeneration. | ||
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| + | Regeneration is the process by which an organism is able to replace or restore lost tissue, organs, limbs, or other body structures (King & Newmark, 2012). Interestingly, the phenomena of repair and regeneration are universal, but the capacity for regeneration is a characteristic that varies remarkably among organisms. Certain invertebrates, such as hydra, possess the ability to regenerate into two genetically identical individuals when cut in half (Bosch, 2007). Amphibians such as salamanders can readily replace whole body parts (Morrison et al., 2006). Mammals however, are fairly limited in their ability to regenerate. Although the function of a damaged organ may be recovered, most mammals are unable to restore missing body structures (King & Newmark, 2012). The ability to replace lost or damaged organs with new body structures that are genetically and functionally identical to the original is known as complete regeneration. Incomplete regeneration describes the process by which organ or tissue function may be recovered, but missing or damaged structures cannot be restored (King & Newmark, 2012). | ||
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| + | ======2. Defining Key Terms====== | ||
| + | The healing and regeneration of a complex body structure involves diverse cellular processes such as wound healing, programmed cell death, stem cell proliferation, and dedifferentiation (King & Newmark, 2012). | ||
| + | In order to gain a better understanding of the cellular processes involved in regeneration, it is important to begin by defining some key terms. Stem cells can be defined as undifferentiated progenitor cells that possess the ability to develop into specialized cells, while also maintaining self-renewal (Singh et al., Chandra, 2016). Cellular differentiation describes the process by which a cell changes from one cell type to another, typically to a more specialized type (Slack, 2007). Dedifferentiation is another important biological phenomenon whereby specialized cells regress back to a simpler state reminiscent of stem cells (Cai et al., 2007). | ||
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| + | Stem cells can be classified as totipotent, pluripotent, multipotent or unipotent, depending on their potency (Singh et al., 2016). Totipotent cells have the potential to develop into all the cell types in an organism, plus extra-embryonic cell types. Pluripotent cells can give rise to all the cell types that make up the body, except extra-embryonic cell lines. Multipotent stem cells are lineage specific with limited differentiation potential, and tend to develop only within specific tissue or cell lines. The developmental potential of unipotent cells is further reduced as they are able to give rise to only one cell type. It is important to note that both the self-renewal capacity and the differentiation potential of stem cells is reduced down the stem cell hierarchy from totipotent to unipotent cell states (Singh et al., 2016) | ||
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| + | The blastema is a general term used to describe a regeneration bud containing a mass of undifferentiated progenitor cells capable of growth and renewal. Several organisms such as planarian flatworms, zebrafish and salamanders utilize a regenerative blastema for healing and regrowth during adult stages (Godwin, 2014). Injury or amputation among such organisms can trigger the formation of a blastema from adult tissue; the blastema then functions to reform the diverse tissues of the missing body structure (Kragl et al., 2009). The identity and potency of the type of cells that make up the blastema is not completely known. It is believed that cells near the site of injury lose their specialized properties and revert back to a primordial state via de-differentiation; these cells then multiply rapidly and redifferentiation to form the new tissue needed to rebuild the missing body structure (Bosch, 2007). Recent research also suggests that in some organisms, cells within the blastema may contribute to regrowth via memory retention of the tissue of origin (Kragl et al., 2009). | ||
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| + | ======3. Types of Regeneration====== | ||
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| + | Regeneration can occur in three different ways: epimorphosis, morphallaxis and compensatory regeneration. | ||
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| + | **Epimorphosis**: This type of regeneration is commonly found within Salamanders, usually results in a new limb or appendage. In this type of regeneration, the remaining part of the limb attached to the body is able to form a ‘blastema’ at the site of the cut. The cells on the wound are able to help construct the missing structures in an ‘add-on’ type of manner. | ||
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| + | **Morphallaxis**: This form of regeneration is commonly found in Hydras, there is no ‘blastema’ formed and the remaining cells are used to regenerate the rest of the body. | ||
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| + | **Compensatory**: Regeneration of this form occurs with the human liver, cells divide but they maintain their differentiated functions. Meaning that the cells produce other cells of their own kind and there is no undifferentiated tissue needed. | ||
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| ======4. Regeneration in Animals====== | ======4. Regeneration in Animals====== | ||
| ==A. Salamander Description== | ==A. Salamander Description== | ||
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| ==E. Human Application== | ==E. Human Application== | ||
| - | {{ :salamander.png?nolink |}} | + | {{ :salamander.png?nolink |}} (Heinrich, 2016) |
| The regeneration in model organisms is applicable to humans as scientists can copy or use these ideas as a framework for future research. For example, using this idea of dedifferentiating cells, scientists are able to create induced multipotent stem cells out of fat cells. Through aspirating fat cells with two different solutions, the fat cells can convert back to a less specific state which can be used for wound healing. However, this cannot be used to regrow limbs, but this is a great step in the right direction for regenerative medicine. (Heinrich, 2016) | The regeneration in model organisms is applicable to humans as scientists can copy or use these ideas as a framework for future research. For example, using this idea of dedifferentiating cells, scientists are able to create induced multipotent stem cells out of fat cells. Through aspirating fat cells with two different solutions, the fat cells can convert back to a less specific state which can be used for wound healing. However, this cannot be used to regrow limbs, but this is a great step in the right direction for regenerative medicine. (Heinrich, 2016) | ||
