Chapter 069. Tissue Engineering (Part 3) pps

Chapter 069. Tissue Engineering
(Part 3)

Table 69-2 Tissue-Engineering Products in Clinical Trials
TRC (Aastrom)
Autologous adult bone marrow cells for
bone grafting
LiverX2000 (Algenix) Extracorporeal liver assist device
Encapsulated proliferated
islet (Amcyte)
Encapsulated islet cells
Myocell (Bioheart)
Encapsulated cells for myocardial
infarction
BioSeed-C, BioSeed-
Oral
Bone (Biotissue Technologies)
Autologous tissue repair for bone and
cartilage
E-matrix (Encelle) Repair or regeneration of disea
sed or
damaged tissue
MarkII (Excorp) Extracorporeal liver assist device
ICX-PRO, ICX-
TRC
(Intercytex)
Wound repair and hair regeneration
HuCNS-
SC (Stem Cell
Inc)
Human central nervous system stem

cells
NT-501 (Neurotech SA) Encapsulated cell technology for long-
term delivery of therapeutic factors to retina
Procord (Proneuron)
Autologous activated macrophage
therapy for patients with acute complete spinal
cord injury
ChondroCelect (Tigenix) Autologous chondrocyte implantation
Spheramine (Titan
Pharmaceutical)
Retinal pigment epithelial cells in
microcarriers to provide continuous source of
dopamine in the brain
ELAD (Vigagen) Extracorporeal liver assist device
Challenges to Tissue Engineering
The greatest success in tissue engineering to date has been in tissues such
as skin and cartilage where the requirements for nutrients and oxygen are
relatively low. Due to oxygen diffusion limitations, the maximal thickness of an
engineered tissue is 150–200 µm if there is not an intrinsic capillary network.
Strategies used to overcome this limitation include transplantation of the tissue
directly into the patient's vasculature or trying to induce angiogenesis by
incorporating growth factors such as vascular endothelial cell growth factor into
the scaffold. A more recent approach involves the creation of an intrinsic network
of vascular channels immediately adjacent to the engineered tissue. A combination
of microelectro mechanical systems (MEMS) fabrication technology and
computational models of fractal branching allows the construction of an intrinsic
microvascular network scaffold within a biocompatible polymer. This preformed
capillary-like network can be seeded with cells and ultimately sustains the growth
and function of complex three-dimensional tissues.
Immune rejection of allogenic cells is another major obstacle. The use of

immunosuppressive drugs is not considered an optimal solution to this problem.
One potential solution is to develop "universal donor" cells by masking the
histocompatibility proteins on the cell surface.
Off-the-shelf availability will need to be addressed for tissue engineering
products to be used widely. Ideally, products should be reproducible and available
at a wide variety of hospitals, including those without sophisticated facilities for
cell culture and cell proliferation.
Further Readings
Ahsan T, Nerem RM: Bioengineered tissues: The science, the technology,
and the industry. Orthod Craniofacial Res 8:134, 2005 [PMID: 16022714]
Lavik E, Langer R: Tissue engineering: Current st
ate and perspectives.
Appl Microbiol Biotechnol 65:1, 2004 [PMID: 15221227]
Lysaght MJ, Hazlehurst AL: Tissue engineering: The end of the beginning.
Tissue Engineering 10:12, 2004
Sheih SJ, Vacanti JP: State-of-the-
art tissue engineering: From tissue
engineering to organ building. Surgery 137:1, 2005
Yow KH et al: Tissue engineering of vascular conduits. Br J Surg
93(6):652, 2006 [PMID: 16703652]