Biomedical Engineering Reference
In-Depth Information
Skin and Vascular Grafts
Skin is a highly proliferative and regenerative tissue. It consists of two main layers: the
dermis, whose main cellular components are
stromal cells
or fibroblasts, and the epidermis,
whose main cellular components are epidermal cells at various stages of differentiation into
keratinocytes (Figure 6.4). Both cell types grow well in culture, and ex vivo cultivation is not
the limiting factor with this tissue. Interestingly, transplanted dermal fibroblasts have
proven to be surprisingly nonimmunogenic.
Skin transplants and engineered skin technologies have been applied to victims of burns
and patients with diabetic ulcers who have severe problems with skin healing. To treat these
problems, skin may be cultured ex vivo and applied to the affected areas. Technologically this
cell therapy is relatively well developed, and currently there are several “engineered skin”
products available, including Apligraf
W
(Organogenesis Inc.) and Dermagraft
W
(Advanced
BioHealing Inc.). Figure 6.5 shows an expansion bioreactor for creating skin grafts from
human foreskins developed by Advanced Tissue Sciences Inc., the now defunct company
that originally developed Dermagraft
W
. The bioreactor is constructed with one mechanical
hinge and two ports for constant “bleed-feed” flow (left panel). The graft products—which
are similar to autologous skin grafts without hair follicles—are easily removed from the
bioreactor, as shown in the right panel. In spite of these successes, important challenges
remain in bringing such products to wide clinical use. The relatively high cost of the
squame about
to flake off
from surface
keratinized
squames
granular
cell layer
prickle
cell layers
basal
cell layer
basal
lamina
connective
tissue of
dermis
basal cell
passing into
prickle cell layer
basal cell dividing
30
μ
m
FIGURE 6.4
The cellular arrangement and differentiation in skin. The cross section of skin and the cellular
arrangement in the epidermis and the differentiation stages that the cells undergo.
From [1].
