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Stem Cells: Background



What are Stem Cells?

Stem cells have two important characteristics that distinguish them from other types of cells. First, they are unspecialized cells that renew themselves for long periods through cell division. The second is that under certain physiologic or experimental conditions, they 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.

Scientists primarily work with two kinds of stem cells from animals and humans: embryonic stem cells and adult stem cells, which have different functions and characteristics that will be explained in this document. Scientists discovered ways to obtain or derive stem cells from early mouse embryos more than 20 years ago. Many years of detailed study of the biology of mouse stem cells led to the discovery, in 1998, of how to isolate stem cells from human embryos and grow the cells in the laboratory. These are called human embryonic stem cells. The embryos used in these studies were created for infertility purposes through in vitro fertilization procedures and when they were no longer needed for that purpose, they were donated for research with the informed consent of the donor.

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.1

1Information from the National Institutes of Health “Stem Cell Resource Page.” For more information, visit http://stemcells.nih.gov/info/basics/


What is Stem Cell Research?

Stem cell research involves cells that can potentially develop into any kind of cell, tissue, or organ in the body (“totipotent stem cells”) and that may one day soon be able to replace damaged or sick cells in a patient with an injury or degenerative disease. Totipotent stem cells are commonly obtained by using somatic cell nuclear transfer (SCNT) technology. This technique, commonly referred to as cloning, involves the removal of the nucleus of an unfertilized, mature egg and its replacement with a genetically complete nucleus obtained from another adult or fetal organism. Since almost all of the hereditary genetic material of a cell is contained within its nucleus, the entity into which this egg develops is genetically identical to the organism that was the source of the transferred nucleus.


What is the Difference Between “Therapeutic Cloning” and “Reproductive Cloning”

Therapeutic cloning uses SCNT technology to create cells that develop only until the pre-embryo stage, at which point the stem cells are removed. These stem cells are then used to research possible cures for serious medical diseases and conditions. In contrast, “reproductive cloning” attempts to use this technology to produce a living, breathing human being.

What Promises Does Stem Cell Research Hold for Medical Science?

Therapeutic stem cell research has already provided, and holds out tremendous promise to continue to provide, great progress for finding a cure or treatment for conditions including breast and prostate cancer, leukemia, diabetes, Parkinson’s disease, Alzheimer’s disease, spinal cord injuries and Huntington’s chorea. It also holds the potential to repair and regenerate human tissues, nerve cells, and skin cells. With the advent of therapeutic cloning through SCNT technology, American medicine stands on the brink of being able to drastically improve the lives and futures of more than 128 million Americans who currently suffer from debilitating diseases and conditions. Use of stem cells is the best way to advance this crucial research.