Biomedical Engineering Reference
In-Depth Information
Fig. 5.6
Comparative mor-
phological views of normal
dermis, regenerated dermis
and scar. Observed at day 483
after grafting the dermis-
free defect in the guinea pig
with the keratinocyte-seeded
dermis regeneration template.
Polarized microscopy was
used to elicit differences in
collagen fiber orientation in
tissue sections from normal
skin.
Top left
: normal dermis.
Bottom left
: scar.
Top right
:
skin regenerated using DRT.
Bottom right
: identical micro-
scopic field to that in
top
right
except viewed in natural
light.
Bar
: 50 µm. (Source:
Orgill 1983)
in ungrafted controls, were observed by electron microscopy between mononucle-
ar cells and scaffold fibers. These associations involved prominent extension of
pseudopod-like processes from cells toward the fiber surface. See also Fig. 9.4. By
day 10, the ECM analog had been degraded to a large extent and extensive neo-
vascularization was observed in various stages of formation. By day 14, the long
axes of dermal fibroblasts in the grafted site showed random orientation. See also
Fig. 8.9. A fibroblast fraction less than 10 % of total number exhibited features of
myofibroblasts in the grafted site whereas a fraction greater than 50 % of dermal
fibroblasts in ungrafted sites were identified as myofibroblasts, with their axes ori-
ented in the plane of the epidermis. The scaffold fibers were present as scattered
fragments engulfed by macrophages by day 14 and were completely dissolved by
day 21. Blood vessels formed a discrete, subepidermal plexus oriented parallel to
the epidermal plane by days 14-17 in grafted but not in ungrafted defects. Deposi-
tion of randomly oriented collagen fibers occurred progressively at grafted defects
during the first year; by contrast, collagen fibers in ungrafted sites were oriented
in a horizontal plane, reminiscent of scar. After a year, the grafted sites resembled
