EMBRYONIC
STEM CELLS
Created By Cate Brown, Jared Eddy,
Ajay Kusnoor & Aaron Prosnitz
Picture Credit: (7)
AN INTRODUCTION TO STEM CELLS
Stem cells, which are populations of cells that are not committed to a specific cell lineage, are important in both the development and in the function of vertebrate organisms. The body maintains a number of stem cells, which are characterized by their ability to maintain their own populations and regenerate other tissue. Satellite cells of the muscle and cells of the corneal epithelium of skin are both examples of stem cell populations in the vertebrate body. The stem cells of the adult body are not totipotent in their developmental capabilities; rather, they are only able to regenerate specific cell types.
STEM CELLS OF THE
EARLY EMBRYO
There are many types of stem cells, but the focus of this web site is on embryonic stem cells. Embryonic stem cells are derived from the inner cell mass of the blastocyst (21). Embryonic stem cells are different from the stem cells of the adult body in that they are totipotent, meaning that they have not undergone differentiation and are unlimited in terms of their developmental capabilities. Differentiation of these stem cells into mature structures involves selective gene expression, which usually leads to morphological alterations and the development of new functional capabilities. Differentiation is associated with a vast array of transcription factors, chemical signals that encourage the expression of certain genes within the genome. The first step in differentiation involves a commitment of the embryonic stem cell to a specific germ layer (endoderm, ectoderm, or mesoderm) within the gastrula. Researchers have identified many different strategies to encourage differentiation in vitro.
BENEFITS OF TOTIPOTENCY
The undifferentiated state of embryonic stem cells has made them particularly valuable to scientists, who have manipulated ES cells to differentiate into a vast array of adult structures in vitro, including liver cells, hematopoietic cells, pancreatic cells, and neural cells. This in vitro manipulation could potentially be used to alleviate many diseases that are currently considered incurable. In vitro study of stem cells may also help scientists understand embryological development in vivo.
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