Biomedical Engineering Reference
In-Depth Information
5a.4.2 Agarose
Agarose is a purified extract from sea creatures such as agar or
agar-bearing algae. Structurally, agarose is a linear polymer that
consists of alternating β-D-galactose and 3,6-anhydro-α-L-galactose
units. Agarose gel has been utilized in tissue culture and tissue
engineering applications. Yang et al. have created agarose gel patches
containing ADSCs as a source of angiogenic factors for promoting
vascularization in an infarcted heart [26]. A patch was put into a
nylon bag and transplanted onto the cryoinjured epicardium of a pig.
Four weeks after infarction, ADSC grafts showed greatly improved
blood perfusion and microvascular density of the scar tissue.
5a.4.3
Collagen Type I
Collagens are major components of the extracellular matrix (ECM)
and facilitate, integrate, and maintain the integrity of a wide variety
of tissues. Collagen type I is present in the skin, tendon, cornea,
dentin, and fascia. In addition, it can be formed into sponges, meshes,
films, sheets, and gels for use in various types of tissue engineering
applications. Kofidis et al. created a hydrogel by preparing an in vitro
tissue construct by mixing mouse ESCs and collagen type I [27]. ESC-
seeded patches were implanted into the infarct wall by surgically
creating an intramural pouch in an athymic nude rat heterotopic heart
transplant model. Transplanted ESCs formed stable intramyocardial
grafts that were incorporated into the surrounding area without
distorting myocardial geometry, thereby preventing infarct wall
thinning and improving fractional shortening. The Simpson group
mixed human MSCs with collagen type I to form a cardiac patch,
which was implanted into the epicardial surface of rat MI hearts
with a fibrin sealant [28]. The collagen grafts embedding MSCs
improved myocardial remodeling and LV function. Moreover, they
also investigated the efficacy of cardiac patches composed of human
ESC-derived mesenchymal cells and collagen hydrogel for cardiac
repair after MI [29]. The use of these cells provided an efficacy
similar to MSCs for cellular cardiomyoplasty. On the other hand,
Zimmermann et al. developed an engineered heart tissue (EHT)
reconstituted by mixing rat cardiomyocytes with collagen type I and
Matrigel [30]. EHTs were designed in a circular shape to fit around
the circumference of hearts. Fourteen days after implantation to
