Stem Cells and the Future of Regenerative Medicine (2002) / Chapter Skim
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1. Project Overview and Definitions
1. Project Overview and Definitions
Pages 7-18
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From page 7... ...
There are confirmed sources of stem cells in adult tissues, such as bone marrow, that maintain the ability to differentiate into the diverse cell types of that tissue throughout the life of an organism. However, cells that maintain the ability to divide and differentiate into more specialized cells of different tissue types are rare in the adult.
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From page 8... ...
The hope of using stem cells to produce regenerative therapies poses fundamental questions: Do human ESCs hold all the clinical promise attributed to them? Is realization of that promise imminent?
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From page 9... ...
The workshop will examine several aspects of stem cell research, including: the biological properties of stem cells in general, the current state of knowledge about the molecular and cellular controls that govern transdifferentiation in cells originating from different types of tissues, the use of stem cells to generate neurons, heart, kidney, blood, liver and other tissues, and the prospective clinical uses of these tissues. The workshop will consider the biological differences of cells obtained from different sources, for example, embryos, fetal tissues, or adult tissues, and discuss concerns about the use of various sources of stem cells.
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From page 10... ...
The committee organized the workshop to address key issues in the status of stem cell research by gathering information from scientific leaders in the field. In addition, the workshop provided an opportunity for the committee to hear from both those who support embryonic stem cell research and those who oppose it on ethical grounds.
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From page 11... ...
Project Overview and Definitions 1 1
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From page 12... ...
In humans, stem cells have been identified in the inner cell mass of the early embryo; in some tissues of the fetus, the umbilical cord and placenta; and in several adult organs. In some adult organs, stem cells can give rise to more than one specialized cell type within that organ (for example, neural stem cells give rise to three cell types found in the brainneurons, glial cells, and astrocytes)
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From page 13... ...
Researchers are just beginning to learn how to achieve this differentiation. Fetal stem cells are primitive cell types in the fetus that eventually develop into the various organs of the body, but research with fetal tissue so far has been limited to only a few cell types: neural stem cells, including neural crest cells; hematopoletic stem cells; and pancreatic islet progenitors.
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From page 14... ...
STEM CELLS AND THE FUTURE OF REGENERATIVE MEDICINE FIGURE 1 Stages of Development of the Human Embryo Egg Sperm Fertilization it. Zygote Cell Division Blastocyst Embryo Implantation 1 Fetus 14
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From page 15... ...
Project Overview and Definitions Egg Sperm Fertilization Differentiation into Specific Cell and Tissue Types Zygote Cell Division Blastocyst Inner .~ Cell Mass Cells from Inner Cell Mass Cultured ESCs Other Cell Smooth Macrophage Neuron Adipocyte Types Muscle Cell FIGURE 2 Isolation and Culture of Human ESCs from Blastocysts 15
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From page 16... ...
Tissue extracted from the fetal pancreas has been shown to stimulate insulin production when transplanted into diabetic mice, but it is not clear whether this is due to a true stem cell, a more mature progenitor cell, or to the presence of fully mature insulinproducing pancreatic islet cells themselves (Beattie et al., 1997~. Finally, multipotent cells called primordial germ cells have been isolated from the gonadal ridge, a structure that arises at an early stage of the fetus that wiD eventually develop into eggs or sperm in the adult.
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From page 17... ...
Finding ways to culture adult stems cells outside the body is a high priority of stem cell research. Additional terms used throughout this report are defined in the Glossary.
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From page 18... ...
The relationship between stem cell type and environmental cues makes problematic the assumption that stem cells cultured in vitro can be expected to perform with predictable results when transplanted in viva (Mornson, S.~., 2001~. It might be possible someday to provide cues to reprogram one cell type into another and even to culture these cells in vitro, but evidence of the normal physiological and restorative function of adult stem cells is very limited today.
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