Biomedical Engineering Reference
In-Depth Information
glycosylation patterns during fluorophore-assisted carbohydrate electrophoresis.
Disaccharides isolated from the glycosaminoglycan component consist exclu-
sively of 4-sulfated chondroitin sulfate and hyaluronic acid (
Fig. 10.4(b)
). Although
the relative levels of each glycosaminoglycan tend to vary from donor sample to
donor sample, both glycosaminoglycan components are consistently detected in
all samples analyzed. Furthermore, no other form of chondroitin sulfate is identi-
fied indicating that the glycosaminoglycan component of decorin and biglycan in
the acellular dermis is composed solely of 4-sulfated chondroitin sulfate
glycosaminoglycan chains.
The biochemical analyses described above demonstrate the AlloDerm RTM
maintains the expected molecular composition characteristic of dermal ECM.
Thus, upon introduction to a wound, the RTM provides the necessary biochemical
components needed to support wound healing. This characteristic of the RTM is
exemplified by its ability to bind growth factors. Using platelet rich plasma (PRP)
as a source of growth factors relevant to wound healing, the RTM matrix has been
shown to bind nearly 50% or more of initial PRP content of growth factors TGF-
β
, PDGF, VEGF and EGF (
Fig. 10.5(a))
. Moreover, this growth factor matrix
combination has been shown to induce fibroblast proliferation in a dose-dependent
manner (Fig. 10.5(b)) (Pietramaggiori
et al
., 2008).
While the biochemical composition and ability to regulate biochemical environ-
ment are essential attributes necessary for function, maintenance of the native
organizational structure is equally important. Histological analysis demonstrates
that the RTM appears structurally intact with collagen fibers arranged in distinct
bundles throughout the tissue
(Fig. 10.6(a
)). Both papillary and reticular dermal
layers are easily identified by differences in the collagen staining intensity. The
efficacy of the decelluarization process is demonstrated by the absence of
hematoxylin stained nuclei or nuclear remnants. The absence of cellular material
is supported by the failure to detect major histocompatibility factor (MHC)
antigens using immunohistochemical staining (Fig. 10.6(b) and (c). Histologic
staining is also useful in identifying additional ECM components that are not
characterizable during biochemical analyses. Elastin, which contributes to the
resilient nature of the matrix, is distributed widely throughout the matrix but
localizes in regions between the bundles of collagen. This elastin network is
revealed through Verhoff's staining which indicates it is maintained following
processing (Fig. 10.6(d)). Immunostaining with an anti-collagen type IV antibody
shows an intact, contiguous basement membrane on the superficial dermal surface
at the epidermal-dermal interface (Fig. 10.6(e)). Collagen type VII and laminin are
protein constituents of the basement membrane necessary for cellular adhesion
and staining demonstrates both are retained in AlloDerm RTM (Fig. 10.6(f) and
(g)). In addition to basement membrane components, small blood vessels distrib-
uted throughout the matrix are also revealed through staining.
The overall three-dimensional organization of RTM can be visualized at the
ultrastructural level using scanning electron microscopy (SEM). Cross-sectional
