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We Know: All About Stem Cells
What are stem cells?
Stem cells have two important characteristics that distinguish them from other types of cells.
- Stem cells are unspecialized cells that renew themselves for long periods through cell division
- Stem cells can be induced to become cells with special functions, such as the beating cells of the heart muscle or the insulin-producing cells of the pancreas.
Where do stem cells come from?
Scientists primarily work with two kinds of stem cells from animals and humans:
- Embryonic stem cells are extracted from embryos created for infertility purposes through in vitro fertilization and donated for research when no longer needed. In 1998, Scientists discovered how to isolate stem cells from human embryos and grow the cells in the laboratory.
- Adult stem cells are undifferentiated cells found among differentiated cells in a tissue or organ, can renew
themselves, and can differentiate to yield the major specialized cell types of the tissue or organ. Adult stem cells have been identified in many organs and tissues. There are a very small number of stem cells in each tissue.
Adult tissues reported to contain stem cells include brain, bone marrow, peripheral blood, blood vessels, skeletal muscle, skin and liver.
Why are stem cells important?
Stem cells are important for living organisms for many reasons.
- In the 3- to 5-day-old embryo, called a blastocyst, stem cells in developing tissues give rise to the multiple specialized cell types that make up the heart, lung, skin, and other tissues.
- In some adult tissues, such as bone marrow, muscle, and brain, discrete populations of adult stem cells generate replacements for cells that are lost through normal wear and tear, injury, or disease.
What are scientists hoping to do with stem cells?
Scientists want to study stem cells in the laboratory with hopes of:
- Determining precisely how stem cells remain unspecialized and self renewing for many years
- Identifying the signals that cause stem cells to become specialized cells
It has been hypothesized by scientists that stem cells may become the basis for treating diseases such as Parkinson's disease, diabetes, and heart disease.
Why are stem cells controversial?
Research using embryonic stem cells derived from humans is controversial because, in order to start a stem cell 'line' or lineage, the destruction of a human embryo and/or therapeutic cloning is usually required.
Many believe this could be slippery slope to reproductive cloning and tantamount to the objectification,
devaluing and destruction of a human being. In an attempt to overcome these moral, political and ethical hurdles, medical researchers have been experimenting with alternative techniques of obtaining embryonic stem cells by extraction, which does not involve cloning and/or the destruction of a human embryo.
Additionally, the use of adult stem cells is showing much promise, and are
already being used in treatments for over 100 diseases and conditions.
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