26-05-2014, 12:56 PM
What are Stem Cells
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Definition: What are Stem Cells?
Stem cells are undifferentiated or ‘blank’ cells found in the human body that have the
potential to develop into many different cell types that carry out different functions.
Most cells in the human body are differentiated. That means they are built to function in a
particular organ system and carry out a specific function. A red blood cell, for example, is
designed to carry oxygen, while a white blood cell is designed to fight off disease. These
differentiated cells result from the process of cell division, a process that begins with
undifferentiated stem cells.
Pluripotent stem cells, found in embryos, can give rise to all the cells found in the human
body – cells as diverse as those found in the brain, bone, heart and skin.
Multipotent stem cells, found in adults or in babies' umbilical cords, have a more limited
capacity. Their development is limited to the cells that make up the organ system that
they originated from. For example, a multipotent stem cell in the bone marrow can
develop into a red blood cell, a blood platelet or a white blood cell, but not into a skin cell
or brain cell.
Researchers believe that stem cells, especially pluripotent stem cells, hold much potential
for medical therapies and medical research such as:
Growing replacement cells or whole replacement organs. Human stem cells can
be used to generate specialized cells in a laboratory and then be transplanted to
replace damaged cells in the body. These could be used to treat a range of
conditions from Parkinson disease to heart failure to spinal injuries. For example,
in the case of a spinal injury, neural stem cells could be generated to replace
damaged tissue.
"Patching" organs that don't work properly - like helping a diabetic person's
pancreas produce insulin. The newest therapies in research on stem cells and
diabetes involve generating islet cells that produce insulin to replace those that a
diabetic person’s immune system destroys.
In the study of human development, stem cells could help researchers determine
why, in the early stages of development, some cells become cancerous or how
genetic diseases develop. This could lead to answers as to how they might be
prevented.
Ethical Issues
Research that uses multipotent stem cells (which are
found in adults and in umbilical cords) is not
generally considered controversial. However, because
their ability to differentiate is limited, so is their
usefulness in research.
However, research with pluripotent stem cells is controversial because it requires
destroying an artificially-fertilized embryo at the 5-14 day stage. Because pluripotent
stem cells can differentiate into all the cell types in the human body, they have the
greatest application in research for new medical treatments.
Recently, researchers at the biotech company, Advanced Cell Technology, claim to have
succeeded in harvesting stem cells from mouse embryos without killing them. If this
technique is valid and its reliability improved, it could alleviate many of the ethical
problems related to stem cell research.