SCAFFOLD CONSIDERATIONS FOR OSTEOCHONDRAL TISSUE ENGINEERING - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 788

combinations of these materials have been used to create osteo-
chondral tissue-engineered grafts. Single-phase scaffolds have been
employed to engineer both cartilage and bone layers; however,
increasingly, research has begun to focus on multiphase scaffolds
employing different material types, pore architecture, and porosi-
ties to better suit the biomechanical requirements of the cartilage
andbonelayers. 35 , 36 Mostexistingcommercialscaffoldsconsistofa
single phase and are not optimized for cartilage repair, resulting in
poor healing of hyaline-likecartilage. 37
A recent review by Martin et al . concisely described (some of)
the different approaches for the fabrication of osteochondral com-
posite constructs with specific considerations for scaffold type and
cell source. 2 In this review they describe four construct options and
four cell optionsas follows:
(a) A scaffold for the bone component but a scaffold-free approach
for the cartilage component. In this approach, researchers
generally made use of stiff bonelike scaffolds comprised of
ceramic 38 or HA 39 or composites thereof. Upon these they
seeded large volumes of cells, which would self-organize into a
cartilage-like matrix. 40 The approach of using cells in high den-
sities to generate cartilage-like tissue has been demonstrated
independent ofthe bonecomponent. 41
(b) Different scaffolds for the bone and the cartilage components
combined at the time of implantation. While combining two
scaffolds might be easier than generation of a bilayer or mul-
tiphase construct, researchers are then faced with a second site
where integration might pose a problem, namely, at the bone-
cartilage interface. One of the reasons to attempt this approach
was a lack of technology/capability to generate biphasic scaf-
folds. Nevertheless, some success was observed seeding and
culturing the two phases separately and then suturing 35 or
gluing them together afterward. 42 This was also demonstrated
in vivo , 43 but integration with the surrounding cartilage tissue
remained a problem, despite the relatively favorable environ-
ment of the rabbitknee.
(c) A single but heterogeneous composite scaffold. This approach
might offer the best option of the four of these described