DESIGNING NANOFIBROUS SCAFFOLDS FOR TISSUE ENGINEERING - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 464

function of cartilage occurs. Thus, there is a need for an alternative strategy that
can promote cartilage tissue regeneration and restore normal functioning of
the joint.
Cartilage is a relatively simple tissue, as it does not require vasculature
for maintenance and consists of only a single cell type. Thus, it is well suited for
tissue engineering, which involves an appropriate combination of scaffolds,
cells and chemical cues (GFs) for structural and functional regeneration of
cartilage [240].
As stated earlier, type II collagen and proteoglycans form a fi brous mesh and
are the major constituents of the ECM of articular cartilage [35]. Thus, electros-
pun polymeric nanofi bers that can mimic ECM constituents may have the poten-
tial to facilitate cartilage regeneration [36].

13.5.2.2.1 POTENTIAL CELL SOURCE FOR CARTILAGE TISSUE ENGINEERING.
Transplantation of cells at the defect site is an approach that can provide a new
cell population at the site of damage, which in turn can lead to ECM production
in vivo [244]. Brittberg et al. reported a cell-therapy-based approach for repair of
injured cartilage in human knee joints. Autologous chondrocytes were isolated
from a healthy site (upper medial femoral condyle of the damaged knee), cul-
tured in vitro , and then re-implanted at the damaged site [12]. Their results dem-
onstrated that the defects treated with autologous chondrocytes were eventually
fi lled with hyaline cartilage with a gradual reduction in disease symptoms [12].
Although autologous chondrocytes are promising candidates, they are available
in limited numbers. Consequently allogenic cells were used for cartilage repair.
Freed et al. reported the possible use of allogenic chondrocytic cells for in vivo
application in rabbit cartilage repair; however, the regenerated subchondral bone
was not similar to the native subchondral bone [245]. In spite of the potential for
using chondrocytes from autologous and allogenic sources for cartilage regenera-
tion, the limited number of chondrocytes ( 2% of the total weight of cartilage)

combined with dedifferentiation in monolayer expansion has led to the explora-
tion of alternative cell source. Mesenchymal stem cells [MSCs] can be an attrac-
tive cell source for cartilage repair due to their multipotency, easy availability,
and demonstrated capability of monolayer expansion [246,247]. Chemical cues/
growth factors can enhance the chondrogenesis of MSCs [248,249]. Thus, they
could be a promising cell source for cartilage tissue engineering.

∼

13.5.2.2.2 SCAFFOLDS FOR CARTILAGE TISSUE ENGINEERING. The search for
an optimal scaffold for cartilage tissue regeneration has resulted in the study of
both synthetic and natural materials including natural constituents of ECM. Col-
lagen type II, the major protein constituent of native ECM of articular cartilage
has been studied for regeneration of cartilage [238]. Shields et al. explored the
potential of electrospun collagen type II nanofi brous scaffolds for cartilage tissue
engineering [101] . Their in vitro studies demonstrated the ability of chondrocytes
to adhere, proliferate, and infi ltrate into the scaffold matrix [101]. The results indi-
cated that electrospun collagen type II scaffolds provide a native environment for