Biomedical Engineering Reference
In-Depth Information
In response to these varied criteria, a number of scaffold materials have been examined as
scaffolds: porcine small intestine submucosa,
(Musahl V at al. 2004) (Rodeo SA et al. 2004)
silk fibers,(Altman et GH al. 2002) (Chen J at al. 2003) (Altman GH et al. 2003)
semitendinosus tendon
(Martinek V 2002), fibronectin/fibrinogen fibres. (Ahmed Z et al.
2000)
In addition to these, historically, three major categories of scaffolding materials have been
employed. These are polyesters, polysaccharides, and collagen derivatives.
However, approaches to mimic the native extracellular matrix of tendon have limitetd to
their inappropiate mechanical strength or the lack of cell adhesion sites. The use of an
acellular graft may prevent the initial cell necrosis observed when autografts and allografts
are used wich leads to the deterioration of mechanical strength following implantation.
Natural tissue scaffolds have the advantage of preserved ECM proteins important for cell
attachment and the desired mechanical properties.
Natural scaffolds are composed of extracellular matrix proteins that are conserved among
different species and wich can act as scaffolds for cell attachment, migration and
proliferation.
Natural scaffolds have been decellularized in order to reduce their immunogenicity, a major
hurdle to overcome in acellular scaffolds is their capacity for recellularization and
regeneration with cellular components in vitro or in vivo, in order to achieve optimal
biological and biochemical functions.(Gilbert TW 2006)
2.1 Collagen scaffolds
Collagen derivatives have been intensively investigated for use in tendon tissue engineering
applications. Tendon extracellular matrix are mainly composed of type I collagen, so scaffolds
based on collagen derivatives are highly biocompatible, then collagen derivatives also exhibit
superior bio-functionality: they better support cell adhesion and cell proliferation.
Cells cultured in collagen gels produce extracellular matrix and align longitudinally with
the long axis of the tissue equivalent, thereby mimicking cell alignment in ligaments
in
vivo
.(Goulet F et al. 2000) (Huang D 1993)
Fibroblasts seeded in collagen gels change their shape and orientation over time (Huang D
1993) (Bell E at al. 1979) (Klebe RJ et al.1989) (Nishiyama T et al. 1993) and these
organizational changes have been correlated with cell proliferation, protein synthesis, and
matrix morphogenesis. (Ben-Ze'ev A et al. 1980) (Harris AK et al. 1981) (Maciera-Coelho A
1971) Fibroblast-seeded collagen scaffolds have been investigated with regard to their ability
to accommodate cell attachment, proliferation, and differentiation.
(Goulet F et al. 2000)
,
(Huang D 1993) (Bellincampi LD et al. 1998) (Dunn MG et al. 1995)
Collagen gel has been reported to augment the quality of tendon repair, but collagen gel
does not possess sufficient mechanical strength, it is often accompanied by a high-strength
component. For instance, Awad et al. (Awad HA et al. 2003) studied collagen gels in
combination with a polyglyconate suture for patellar tendon repair. The biomechanical
properties of the resulting tendon tissues were significantly better than those of naturally
healed tendons, yet still much inferior to those of uninjured tendons.
Compared with collagen gel, collagen sponges exhibit greater mechanical competence.
Given that collagen gels exhibit superior cell-seeding efficiency, a combination of collagen
gels with collagen fibres or sponges represents a promising strategy. Juncosa-Melvin et al.
(Juncosa-Melvin N et al. 2006) showed that gel-collagen sponge constructs could greatly
enhance functional tendogenesis.
