Biomedical Engineering Reference
In-Depth Information
cell therapies that would bypass these defects. The studies described above
suggest that brain tumor and neural stem cells resemble one another at a cel-
lular and molecular level. Whether brain tumors actually arise from NSCs in
most cases remains unclear, and a definitive answer may have to await the
development of better markers for neural stem cells and progenitors.
Nevertheless the fact that these cells express similar genes and show activation
of similar signaling pathways suggests that they use similar strategies to
achieve self-renewal and to generate heterogeneous populations of cells within
a tissue. Understanding stem cell signaling pathways and developing ways to
manipulate them will be critical in our effort to develop new treatments for
tumors of the nervous system.
Potential Use of Stem Cells in Neurological and Other
Diseases: Tissue Engineering at the Bench Site
Repair of damaged organ/tissue (myocardial, neuronal, liver, cartilage and bone,
etc.) is the ultimate goal of stem cell therapy. The experimental and clinical trials
have shown both in animal models and humans the neovascularization and myocar-
dial tissue repair through transdifferentiation into myocardiocytes, or some other
mechanisms (
15,
35
and
39-
45
) .
•
Organogenesis from stem cells
How do a small number of stem cells give rise to a complex three-dimensional
tissue with different types of mature cells in different locations? This is the most
fundamental question in organogenesis. The hematopoietic and nervous systems
employ very different strategies for generating diversity from stem cells. The
hematopoietic system assiduously avoids regional specialization by stem cells.
Hematopoietic stem cells are distributed in different hematopoietic compart-
ments throughout the body during fetal and adult life, and yet these spatially
distinct stem cells do not exhibit intrinsic differences in the types of cells they
generate (
15,
46,
47
). This contrasts with the nervous system, where even small
differences in position are associated with the acquisition of different fates by
stem cells.
While local environmental differences play an important role in this genera-
tion of “neural diversity,” we have found that intrinsic differences between stem
cells are also critical. Part of the reason why different types of cells are generated
in different regions of the nervous system is that intrinsically different types of
stem cells are present in different regions of the nervous system. To understand
the molecular basis for the regional patterning of neural stem cell function, we
are studying how these differences are encoded.
•
Therapeutic implications for tissue-committed stem cells (TCSCs)
