Biomedical Engineering Reference
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Together, these modified HA hydrogels serve as the signal or guiding
cue to direct the NSC adhesion and then towards their spreading,
growth or differentiation. The adhesive modifications provide
adaptable and stable microenvironments for the cells and subsequently
affect cell response. Following the adhesion, cells can migrate along
the scaffold, and their differentiation is then also affected [50].
This has been proven in the report of HA fibres conjugated with RGD,
in which the focal adhesion formation, spreading and proliferation of
cells are dependent on the density of RGD, while the differentiation
of cells is influenced by the adhesive capacity of the cells and by the
density of RGD [51].
1.4.2 Cell Migration
Many findings have shown that the HA gels may promote different
modes of NSC migration. For example, HA hydrogels modified by the
NgR antibody and/or PLL support the neural precursor cell survival
and migration from neurospheres [50], and such migration is also
seen in the HA gels modified by BDNF and VEGF in the study of
Wang and co-workers [52]. As
Figure 1.3
shows, NSC grow on the
HA hydrogel, exhibiting a good adhesion and migration on the gel,
with long neurites along the surface of HA scaffold.
The network structure of HA gel contributes to a better support and
guidance for cell spreading. The adhesion and migration of many
kinds of cells including NSC on the hydrogels are along the backbone
of the gel. However, it may not be the only reason for the migration,
because other factors also contribute to the migration of the cells.
The HA molecule itself affects cell migration to some extent, since
a high level of HA remains in adult brain areas where the NSC
persist, proliferate and migrate. The migrated neuroblasts in these
areas express the HA-mediated motility receptor, indicating that HA
may be involved in regulating NSC migration [2]. In addition to the
NSC, some other cells, such as cancer cells, also show similar effects
on HA-based hydrogels since their motility is promoted on the gel.
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