Biomedical Engineering Reference
In-Depth Information
Unfortunately, cartilage has a poor natural regeneration
capacity,
3
and this structure is commonly lost. Thus, articular car-
tilage damage, primarily osteoarthritis, causes severe pain, limits
the ability to perform basic activities, and causes significant eco-
nomic loss
4
in developed and developing countries. In the United
States, this disease affects 27 million people,
5
and by 2015, it
is predicted to lead to the replacement of 2 million knees and
hips.
6
In Indonesia, this disease disables approximately 4.4 million
people.
7
Current efforts to restore cartilage function have many limi-
tations in terms of cost, risk, availability of donor, success rate,
and performance of the final tissue. Therefore, significant research
has focused on developing tissue engineering-based cartilage
treatments. Since 1987, autologuous chondrocyte transplantation
(ACT),
8
the first cartilage tissue engineering approach applied clini-
cally, has been used to treat full-thickness chondral defects in more
than 12,000 patients. This method involves harvesting a small num-
ber of chondrocytes through microsurgery, propagating them in
the laboratory, and then injecting the cell suspension underneath
a sealed periosteal flap, or bilayered collagen membrane.
9
Since it
is an autologous technique, this method has low risk of immune
response. However, there are risks of chondrocyte leakage and
unwanted periosteal response (e.g., hyperthrophy), and the surgi-
cal procedures are complex.
10
Further, the cells typically undergo
dedifferentiation during expansion, as characterized by changes in
morphology and gene expression, and the resultant tissues do not
commonly attain the zonal structure that is functionally important
in normalarticular cartilage.
11
Hydrogel-/matrix-based cartilage tissue engineering has gained
interest, especially because of its capability to provide three-
dimensional growth space, while maintaining chondrocyte viabil-
ity and phenotype. Hydrogels are also interesting because of their
high permeability (necessary for nutrient and metabolite trans-
port), low toxicity (because of the small amount of materials being
used), range of mechanical properties (Fig. 36.2), and capacity for
functionalization.
12
,
13
There are several different types of hydro-
gel matrices that have been used for cartilage tissue engineer-
ing, that is, carbohydrate based, protein or amino acid based, and
Search WWH ::
Custom Search