For example, clinicians and scientists might direct a stem cell population to expand several fold through symmetrical self-renewal before differentiation into multipotent or more specialized progenitor cells. Knowledge of the details could be clinically useful. The factors that determine the fate of stem cells is the focus of intense research. (SC- Stem cell, DP-Differentiated progeny) D) Symmetric division without self-renewal where there is a loss in the stem cell pool but results in two differentiated daughter cells. C) Asymmetric self-renewal in which a stem cell divides into one differentiated daughter cell and one stem cell, maintaining the stem cell pool. B) Symmetric self-renewal where a stem cell divides into two daughter stem cells increasing the stem cell pool. A) Quiescence in which a stem cell does not divide but maintains the stem cell pool. This results in greater proliferation of differentiated progeny with a net loss in the stem cell pool.įour potential outcomes of stem cells. The fourth fate is that in which a stem cell divides to produce two daughters both different from the parent cell. Asymmetric self-renewal results in the generation of differentiated progeny needed for natural tissue development/regeneration while also maintaining the stem cell pool for the future. The third fate, asymmetric self-renewal, occurs when a stem cell divides into two daughter cells, one a copy of the parent, the other a more specialized cell, named a somatic or progenitor cell. This does not result in differentiated progeny but does increase the pool of stem cells from which specialized cells can develop in subsequent divisions.
A second fate of stem cells is symmetric self-renewal in which two daughter stem cells, exactly like the parent cell, arise from cell division. An example of this is stem cells in the bone marrow that await activating signals from the body. A common fate for multipotent stem cells is to remain quiescent without dividing or differentiating, thus maintaining its place in the stem cell pool.
#Stem cell series#
In other words, pluripotent cells can eventually become any cell of the body by differentiating into multipotent stem cells that themselves go through a series of divisions into even more restricted specialized cells.īased on the two defining characteristics of stem cells (unlimited self-renewal and ability to differentiate), they can be described as having four outcomes or fates 3 ( Figure 2). These more limited multipotent stem cells come in several subtypes: some can become only cells of a particular germ line (endoderm, mesoderm, ectoderm) and others, only cells of a particular tissue. In natural development, pluripotent stem cells are only present for a very short period of time in the embryo before differentiating into the more specialized multipotent stem cells that eventually give rise to the specialized tissues of the body ( Figure 1). Pluripotent stem cells are so named because they have the ability to differentiate into all cell types in the body. Their sources, characteristics, differentiation and therapeutic applications are discussed. 2 Therefore, this review will sort stem cells into two categories based on their biologic properties - pluripotent stem cells and multipotent stem cells.
#Stem cell how to#
Commonly, the modifiers, “embryonic,” and “adult” are used to distinguish stem cells by the developmental stage of the animal from which they come, but these terms are becoming insufficient as new research has discovered how to turn fully differentiated adult cells back into embryonic stem cells and, conversely, adult stem cells, more correctly termed “somatic” stem cells meaning “from the body”, are found in the fetus, placenta, umbilical cord blood and infants. The general designation, “stem cell” encompasses many distinct cell types. Therefore, it is important to note the additional requirement for stem cells they must be able to give rise to a specialized cell type that becomes part of the healthy animal. This trait is also true of cancer cells that divide in an uncontrolled manner whereas stem cell division is highly regulated. First, stem cells must have the ability of unlimited self-renewal to produce progeny exactly the same as the originating cell. In order for cells to fall under the definition of “stem cells,” they must display two essential characteristics. Stem cells have the ability to build every tissue in the human body, hence have great potential for future therapeutic uses in tissue regeneration and repair.
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