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Stem Cells. What are stem cells?. Stem cells are unspecialized cells capable of developing into many different types of cell. Stem cells found in embryos are called embryonic stem cells and develop into all the different types of cell in the body.
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What are stem cells? Stem cells are unspecialized cells capable of developing into many different types of cell. Stem cells found in embryos are called embryonic stem cells and develop into all the different types of cell in the body. Adults also contain stem cells. These are found in small numbers in many organs, including bone marrow, brain, skin and muscle.
cardiac muscle red bloodcells nerve cells cells Embryonic stem cells Up until the eight cell stage, all of the cells in a human embryo are identical. At this stage, these stem cells are unspecialized and can therefore differentiateinto many different types of cell. After the eight cell stage, most of the embryonic cells become specialized and can no longer differentiate. Some will become nerve cells, others will become blood cells, muscle cells, bone cells, etc.
Adult stem cells Adult stem cells are found in small numbers in many organs and tissues, such as bone marrow. Adult stem cells normally maintain and repair damaged tissue, and, unlike embryonic stem cells, can usually only make a small number of cell types. For example, adult stem cells in the skin only normally form skin cells. Research has shown that some adult stem cells can be manipulated to produce many different cell types (e.g. brain stem cells can make muscle cells). This is called plasticity.
Plant stem cells Plants also have stem cells.Plant cells can differentiate to form specific cells throughout the plant’s life. Animal cells lose this ability early in their life cycle. Unspecialized plant cells are found in tissues called meristems. Plant stem cells can become specialized to form tissues such as: • xylem: these cells transport water and minerals up the stem from the roots to the shoots and leaves • phloem: these cells transport sugars, produced in the leaves, up and down the stem. These new types of tissue can be found in the flowers, leaves, stems and roots of the plant.
Super starfish! What do plants and starfish have in common? Chop the stem of a plant and it will grow back. What’s more, the cut stem can grow into a completely new plant. The same is true of the starfish! If it loses an arm to a predator, it will grow back. Even better, if the predator manages to eat everything but the arm, a new individual can grow out of the remaining arm!
Animal regeneration Why can a starfish regenerate missing limbs? The starfish contains stem cells that can divide, differentiate and produce new tissues to replace those that are lost. Humans and most other animals cannot do this, but scientists are studying how stem cells could be used to create new tissue and even new organs to treat disease, injury and conditions such as paralysis. What type of stem cells should be used?
A controversial source? Most stem cell research has used cells obtained from embryos left over from fertility treatment. These are called embryonic stem cells (ESCs) and are the most powerful type because they can turn into any type of cell. Their use in research is strongly criticized by people who believe it is unethical to kill embryos for their cells. Work involving embryonic stem cells is subject to government regulation.
Advantages of using adult stem cells Adult stem cells are not as powerful as embryonic stem cells, but they do have other advantages. • They come from volunteers so they are more ethically acceptable. • A patient’s own stem cells could be used to treat their own disease, avoiding the problem of immune rejection. • It might be easier to guide their development into specific cell types. • They are less likely to become cancerous. There is a great deal of research into using adult stem cells to treat diseases. They could reduce the need for organ transplants, which have long waiting lists.
