Unformatted text preview: of using embryonic stem cells
in clinical transplantation therapies.
Mouse embryonic stem cells are grown in the presence of a growth factor
called LIF (for leukemia inhibitory factor), which signals through the
JAK/STAT pathway (see Figure 15.40) and is required to maintain these
cells in their undifferentiated state (Figure 17.24). If LIF is removed from the
medium, the cells aggregate into structures that resemble embryos (embryoid bodies) and then differentiate into a wide range of cell types, including
neurons, adipocytes, blood cells, epithelial cells, vascular smooth muscle
cells, and even beating heart muscle cells. Human embryonic stem cells do
not require LIF but are similarly maintained in the undifferentiated state by
other growth factors, which are not yet fully characterized.
Importantly, embryonic stem cells can be directed to differentiate along
specific pathways by the addition of appropriate growth factors to the culture medium. It may thus be possible to derive populations of specific types
of cells, such as heart cells or nerve cells, for transplantation therapy. For
example, methods h...
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