Biomedical Engineering Reference
In-Depth Information
a
b
Plasma membrane
Plasma membrane
Cytoplasm
Cytoplasm
Microstructure
Focal adhesion
Focal adhesion
Actin stress fiber
Actin stress fiber
S
< 10
μ
m
10
μ
m <
S
Spacing,
S
Microstructure
Fig. 11.4
Formation of an actomyosin contractile complex in cells in a regular array of micropil-
lars. In fi broblasts, (
a
) the actomyosin contractile complexes bridge the pillars in cells on the
micropillars spaced at
S
< 10
m, whereas (
b
) the contractile complexes are formed along the edge
of the pillars in cells on the micropillars spaced at
S
< 10
μ
μ
m
Saltzman
2002
) arrays of micropillars (Miyoshi et al.
2012
,
2010
; Frey et al.
2006
;
Ghibaudo et al.
2009
).
In cells on a micro-grooved structure, actin fi laments align with the longer axis
of the grooves. This effect causes various cells such as epithelial, endothelial, glial
cells, fi broblasts, osteoblasts, and neutrophils, to align (Clark et al.
1990
; Crouch
et al.
2009
; Ohara and Buck
1979
; Zhu et al.
2004
) and migrate (Kaiser et al.
2006
;
Tan and Saltzman
2002
) along the grooves.
Consistent with the idea of the contact guidance, in cells within the regular
array of micropillars, the actin fi laments and focal adhesions are limited only at
the top of the pillars (Fig.
11.4a
) (Frey et al.
2006
; Ghibaudo et al.
2009
; Seo
et al.
2011
). On the other hand, if there is enough spacing between the pillars,
actin fi laments are constrained between the pillars, and the focal adhesions are
present only on the side and/or the bottom of the pillars (Fig.
11.4b
) (Ghibaudo
et al.
2009
). The threshold of spacing that determines whether actin fi laments are
limited on the top of the pillars or between them is 10
m in 3 T3 fi broblasts
(Ghibaudo et al.
2009
) (Fig.
11.4
). The threshold of spacing is supposed to
depend on the fl exibility of actin cytoskeleton specifi c to each cell type (Miyoshi
et al.
2010
; Clark et al.
1987
). The threshold of pillar diameter that determines
whether the actin cytoskeleton is constrained on top of or between the pillars is
reported to be 1
μ
m, which closely correlates with the minimum size of the actin-
myosin contractile complex: a minimum length of approximately 1
μ
μ
m (Ghassemi
et al.
2012
; Verkhovsky et al.
1995
).
