Biomedical Engineering Reference
In-Depth Information
body tissue or organ. In the last few years, such new scientific methods and concepts
have emerged in two relevant areas. One is the progress in the study and manipulation
of stem cells. The other is the progress in research on repair of damaged spinal cord
systems of animals (Okada et al., 2007; Yoshii et al., 2009).
The use of stem cells as a biological basis for tissue engineering has opened up an
entirely new chapter in medicine and revealed the possibility of breakthrough in at-
tempts to repair and regenerate damaged parts of nervous systems. Stem cells have ca-
pacity for self-renewal they can differentiate into multiple cell types and have capabil-
ity of
in vivo
reconstitution of a given tissue. Both embryonic and adult (somatic) stem
cells have shown great promise. Rapidly accelerating rates of progress are evident in
more effective ways of controlling cell differentiation, in understanding the mecha-
nisms of cell engraftment into host tissue and in growing cell cultures in bioreactors.
The future of use of stem cell therapy will depend on the availability of means of
delivering the cells to the location of nerve damage. No applicable scaffold is currently
available for implantation in the spinal cord and there is no evidence of an advanced
state of development of such a scaffold (Tanaka and Ferretti, 2009). The requirement
is for an implantable scaffold, biologically, chemically and physically compatible with
the spinal cord environment. It will have to be designed to deliver preselected neural
stem cells to the location of nerve damage and then to support, guide and co-ordinate
the regeneration of the nerve and of the damaged tissue. In addition to stem cells, the
scaffold will have to deliver therapeutic factors and cells identified as essential or help-
ful to reconstruction of nerves. Looking further ahead, a requirement may emerge for
the scaffold to act also as a genetic delivery tool, for non-viral and viral gene delivery,
with or without targeted genomic integration. The underlying therapeutic concept is
that combination strategies will maximize the ability to recreate nerve connections and
regenerate spinal cord tissue.
To summarise, a tissue engineering device for repair and regeneration of spinal
cord nerves will consist of two components: stem cells which are in an advanced state
of development and scaffold, which is yet to be developed. The aim of this program
is to design and develop the required scaffold. The design stage will be preceded by
research to establish the principal design parameters which are not yet known.
scaffolds for therapeutic treatment of injuries to Central and Peripheral
Nervous systems
The tissue engineering scaffolds for repair and regeneration of brain and spinal cord
protective dura mater, designed and developed by the author of this chapter, have
outstanding clinical success. But they were constructed, like virtually all clinically
successful scaffolds for implanting into connective tissue. For this reason, they had
structure resembling that of connective tissue. In connective tissue, the fibrillar col-
lagen ECM is more plentiful than the cells and surrounds individual cells on all sides,
determining the physical properties of the tissue. The tissue engineering scaffolds for
connective tissue are constructed to have similar internal structure, where individual
cells are surrounded by biopolymer on all sides, while providing conditions for cell
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