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Lecture Summaries Thursday, November 30, 2006 Lecture One Webcast 10:00 a.m.-11:00 a.m. ET & PT During embryonic development, stem cells generate all the specialized cells that populate body tissues such as muscle, the nervous system, and blood. The term embryonic stem cells, or ES cells, is used by researchers for cells that can be isolated from early embryos, before they differentiate into specific types of cells. Depending on when they are isolated, embryonic stem cells are pluripotent—able to become virtually any type of cell—or multipotent—able to become many, but not all, types of cells. Because stem cells have the potential to generate fresh, healthy cells of nearly any type, there is interest in exploring their use to treat and cure various diseases. The societal controversy regarding human ES cells relates primarily to their derivation from very early embryos. In addition, certain stem cell lines are developed using a cloning technique called somatic cell nuclear transfer, which can generate cells that are an exact genetic match to a patient. Break Lecture Two Webcast 11:30 a.m.-12:30 p.m. ET & PT Mature organisms have stem cells of various sorts, called adult stem cells. Adult stem cells supply cells that compensate for the loss of cells from normal cell death and turnover, such as the ever-dying cells of our skin, our blood, and the lining of our gut. They are also an essential source of cells for healing and regeneration in response to injury. Some animals, such as sea stars, newts, and flatworms, are capable of dramatic feats of regeneration, producing replacement limbs, eyes, or most of a body. It is an evolutionary puzzle why mammals have more limited powers of regeneration. Researchers are interested in pinpointing where adult stem cells reside and in understanding how flexible adult stem cells are in their ability to produce divergent cells such as muscle and red blood cells. Understanding the sources and the rules for the differentiation of adult stem cells is essential for tapping their therapeutic potential. Since consenting adults can provide adult stem cells, some people think that adult stem cells may be a less controversial area of research than embryonic stem cells. Friday, December 1, 2006 Lecture Three Webcast 10:00 a.m.-11:00 a.m. ET & PT There are two main approaches to using stem cells to fight human diseases: develop stem cells to produce therapeutic replacement cells and study stem cells as a model for understanding the biology of a disease. Significant progress has been made in producing stem cell lines that, for example, participate in the regeneration of damaged nervous tissue. Many human diseases, such as juvenile diabetes (type 1 diabetes), involve malfunctioning genes and environmental triggers. Usually, a specific type of cell is primarily affected by the disease, and the cellular dysfunction produces the symptoms. In juvenile diabetes, the insulin-producing islet cells of the pancreas are destroyed. Insulin is critical to the proper regulation of sugar by the body, and its absence causes the severe condition called diabetes. Researchers want to coax embryonic stem cells into becoming healthy insulin-producing cells. These cells might then be transplanted into people with diabetes to produce the insulin they lack. Researchers are also interested in producing stem cells that malfunction exactly like the diseased cells in order to understand fundamental aspects of the disease and also to test treatments. Break Lecture 4 Webcast 11:30 a.m.-12:30 p.m. ET & PT Human tissues vary in their ability to heal and regenerate. The nervous system has weak powers of regeneration, while the skin is quick to make new cells for repair. Mammalian muscle cells are intermediate in their ability to regenerate. Human muscle can regenerate in response to minor wounds and normal wear and tear, but humans will not grow a new bicep, for example, in response to amputation. The heart is the most important muscle in the body and yet has feeble regenerative capabilities. Research into the wholesale production of new replacement organs and limbs is in its infancy, but research into enhancing normal levels of regeneration is progressing rapidly. Recent discoveries concerning the location and characteristics of adult stem cells and the signals that wounded tissue produces to activate stem cells have increased our understanding of regeneration. Insulin-like growth factor 1 (IGF1) is an example of an important stem cell communication molecule. If the activity of the growth factor is experimentally enhanced, muscle regeneration improves.
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