Replacing Cells - Biotechnology and Your Health: Pharmaceutical Applications - page 114

into many different types of specialized cells. Two different types of
cells are the focus of interest, embryonic stem (ES) cells and adult stem
cells . The ES cells are found in the very early-stage embryo. Adult stem
cells refer to cells found in one tissue that may be able to develop into
specialized cells of another tissue or organ. Think of a cell found in
liver that, under the right circumstances, might be persuaded to
develop into a nerve cell. In the laboratory, ES cells can divide over
and over again, under the right conditions, producing many more
ES cells that, with the addition of certain chemicals, can change into
one of many different kinds of specialized cells. Animal experiments
have shown that a single embryonic stem cell can become any cell in
the body. Because, as the source of the entire adult body, ES cells can
become every kind of cell, they are called totipotent .
Stop and Consider
What are the possible uses of ES cells in healthcare? What are
some of the scientific barriers to the potential of ES cells? What
approaches are being explored to overcome these barriers?
Adult stem cells are tucked away in specialized tissues and
organs, such as bone marrow, skin, liver, fat, kidney, and even the
brain. The accepted and established role of adult stem cells appears
to be to help maintain the organ in which they are found and to
allow that organ to repair itself if damaged. But is the potential of
adult stem cells limited to just a few options? Some scientists believe
that stem cells in some adult tissues may have the ability, under the
right conditions, to become many different kinds of specialized
cells and not just the cells of the tissue in which they are found.
That would mean that some adult stem cells, though not totipotent
like embryonic stem cells, are pluripotent , meaning that they could
change into a number of different types of specialized cells, given
the right circumstances.