Biomedical Engineering Reference
In-Depth Information
FIGURE 6.6
Encapsulation of islets in semiporous plastic is one promising way to protect them from attack by
the immune system.
From Lacey, 2001.
Chondrocytes can be cultured ex vivo to increase their numbers by up to tenfold. Using
this technique, deep cartilage defects in the knee can be treated by autologous cell
transplantation. In this case, a biopsy is collected from the patient's knee outside the
affected area (Figure 6.7) and the chondrocytes are liberated from the matrix by an enzy-
matic treatment. The cells are allowed to grow in a two-stage cell ex vivo culture process
to increase their number. The cells are then harvested and reintroduced into the affected
area within the knee joint. This type of therapy has been shown to aid in healing of cartilage
defects and is the basis of the Carticel
W
cell-therapy product (Genzyme Inc.). Numerous
patients are afflicted with knee problems that effectively leave them immobile. It is esti-
mated that over 200,000 patients are candidates for this type of cellular therapy annually
in the United States alone.
Hepatic, Neural, and Cardiovascular Cell Therapies
Other forms of cell therapies are being developed to treat complex tissues such as the liver,
brain, and heart. It is difficult to obtain and culture the main cell types of these complex
tissues, and therefore progenitor and stem cell-based approaches are being actively investi-
gated. Clinical trials for each of these tissues have been initiated using both adult
mesen-
chymal
stem cells as well as tissue-specific stem cells. The derivation of liver cells from
stem cells is of interest both to treat hepatic failure, as well as to produce improved in vitro
screens for drugs. Bone marrow and stem cell transplantation into the heart to treat ischemia
and prevent the progression to heart failure has shown promise in the clinic, but there are
still many important issues that need to be resolved for such procedures to be used widely.
Cell transplantation to the brain also has been attempted clinically with mixed results.
Recently, Geron Corporation was given clearance to start the first human clinical trial of
