Glossary Term Name
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Summary:
Stem cells are the essential cellular building blocks that allow the body to regenerate new cells and repair tissue. Scientists are investigating the therapeutic potential of both embryonic and adult stem cells as a research tool to better understand-and develop treatments for-diseases that affect over 100 million Americans in their lifetime, including diabetes, cancer, heart disease, spinal cord injuries, Alzheimer's, Parkinson's, and other debilitating conditions.
Research involving the use of stem cells has taken place in the U.S. for about 50 years. Most has been on adult stem cells found in organ systems, which need a constant supply of new cells, such as the blood, skin, brain, and the gastrointestinal track. Adult stem cells are capable of developing only into the cells of the organ system from which they are derived. Scientists continue to seek ways to make adult stem cells more versatile and able to produce cells for a variety of organ systems. For example, research on adult stem cells found in the placenta and umbilical cord blood have shown potential to differentiate into other cell types.
Human embryonic stem cells (ESCs) were first isolated in 1998. Currently, these stem cells are derived from a "blastocyst," a 5-day-old embryo, which has been fertilized in vitro. ESCs can differentiate into any cell type in the body. They are easy to work with in a laboratory and can be kept in their "undifferentiated" (unspecialized) state for long periods before developing into specialized cells from various organ systems. Scientists have only begun to investigate the therapeutic potential of ESCs in the study of disease processes and the development of techniques that may have applications in treating numerous diseases.
Researchers are investigating alternative methods for producing ESCs. One technique, somatic cell nuclear transfer (SCNT), is sometimes called therapeutic cloning. Scientists remove the nucleus of an unfertilized egg and replace it with the nucleus of an adult cell. After the egg is stimulated to divide, researchers can derive from it new embryonic stem cell lines that are genetically identical to the patient. Though there has been success in using this process with animal cells, SCNT has not yet produced human ESCs.
Another new research technique that 'reprogrammed' human skin cells to behave like embryonic stem cells was announced in November 2007. These induced pluripotent stem (IPS) cells were created by introducing a set of four genes that regulate embryo development encased in retroviruses into a human skin cell. The genes change the nature of the skin cell by integrating into the cell's DNA and altering it until it resembles an ESC. The reprogramming research, like many other new techniques, is still in its infancy. It is important to pursue all avenues of stem cell research that will lead us to a cure.
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