Biomedical Engineering Reference
In-Depth Information
DRT
Fig. 9.3
Identification of the dermis regeneration template (DRT). The average pore diameter
of a collagen scaffold profoundly affects its ability to block wound contraction and its regen-
erative activity. Full-thickness excisional skin defects in the guinea pig were treated with several
scaffolds, differing in pore diameter but otherwise identical in structure that were members of a
collagen library. The delay in inset of defect contraction is shown on the vertical axis. The hori-
zontal axis is logarithmic to accommodate the wide range in pore size in this study. DRT is defined
within the range 20 to 125 µm where contraction delay is maximized and regeneration occurs.
(Yannas et al. 1989)
the large pores in analog B contained thick clusters of cells, approximately 30-50
cells per pore cross section, while the much smaller pores of DRT contained only
2-5 cells per pore cross section (Yannas 2001f). The overall lower cell content of
the DRT scaffold can be explained in terms of the lower cell density that character-
izes wounds grafted with DRT. Furthermore, cell-scaffold binding would be ex-
pected to be much more extensive than cell-cell binding inside DRT due to a purely
physical reason; the active scaffold had a lower pore size, corresponding to a higher
specific surface, relative to analog B (estimated 12-fold higher specific surface in
DRT than in analog B; see Yannas 2001f).
The isolated presence of cells inside DRT shows that the assemblies of myofibro-
blasts, based on intercellular adherens junctions (AJs), as described above for normal-
ly contracting skin wounds (Hinz et al. 2004), were dispersed in the presence of DRT.
Assemblies of contractile cells appear to scale up the contractile force of individual
cells to the macroscopic contractile forces that deform wound tissues and eventually
close the wound. Such deformation was prominent in the presence of the regenera-
tively inactive analog B, where contraction takes place almost unchanged from the
