Biomedical Engineering Reference
In-Depth Information
a
c
DRT
M
DRT
b
M
DRT
Fig. 9.4
Ultrastuctural view of cell-scaffold interactions 7 days after grafting of a full thickness skin
defect in the guinea pig with DRT.
a
Mononuclear cell (not identified further) exhibits pseudopods
(
black arrow
) and contact with the DRT surface.
b
Mononuclear cell exhibits pseudopods (
black
arrows
) and contact with the DRT surface.
c
Mononuclear cells (M) formed a contiguous monolayer
along the surface of DRT. Magnification:
a
× 5500.
b
× 14,000.
c
× 4500 (Murphy et al. 1990)
(Yannas et al. 1989; Troxel and Yannas 1991; Yannas 1998). Independent studies of
the forces that maintain contractile cells assembled during normal contraction suggest
that cell-cell contact and consequent coordination among myofibroblasts are required
for generation of mechanical forces between cells in normally contracting wounds
(Follonnier et al. 2008; Follonier et al. 2010; Goodbout et al. 2013).
Disorientation of long axes of contractile cells present inside the pores of the DRT
scaffold is clearly evident in photographs of myofibroblasts in skin wounds and nerve
wounds (Fig.
9.1
). Such disorientation stands in contrast to the high orientation ob-
served in the absence of DRT, where long cell axes are oriented in the plane of the
epidermis in skin wounds or circumferentially around the stumps of transected nerves
(Fig. 8.5; Troxel and Yannas 1991; Chamberlain et al. 2000a). The resulting random-
ization of force vectors contributed by individual cells is expected to lead to extensive
mutual cancellation of vectors, leading to reduction of the resultant macroscopic force.
Binding of contractile cells on the DRT surface is the simplest explanation for
dispersion of cell assemblies and disorientation of long axes of cells in the pres-
ence of DRT. These morphological changes in contractile cells are not observed in
the presence of very similar collagen scaffolds used as controls or in the absence
of DRT, suggesting that DRT possesses molecular features that distinguish it from
closely related controls. Direct evidence of close approach and contact of contrac-
tile cells to the scaffold surface has been obtained by transmission electron micros-
copy (Fig.
9.4
; Murphy et al. 1990); however, such evidence at the ultrastructural
scale contains no molecular evidence that confirms cell-matrix binding.
