Biomedical Engineering Reference
In-Depth Information
Hwang et al. compared the chondrogenic potential of ES cells in three-
dimensional environments by encapsulating them within a PEGDA hydrogel
scaffold with their monolayer culture (Hwang et al, 2005, personal commu-
nication). They observed enhanced chondrogenesis in the 3D system as com-
pared to the conventional monolayer system. These findings further support
the argument that the differentiation of ES can be modulated by 3D systems.
Langer and coworkers also observed a similar trend in three-dimensional
scaffolds leading to the formation of neural, hepatic, and cartilage tissues [72,
318]. They further investigated the role of mechanical properties of the scaf-
fold on hES differentiation by using matrices such as matrigel, and a three-
dimensional PLGA-co PLA scaffold coated with matrigel [72]. Although ma-
trigel provides a three-dimensional environment to the encapsulated cells, it
failed to support 3D tissue formation compared to the matrigel-coated PLGA-
PLA scaffold. These findings indicate the importance of mechanical stiffness
of the scaffold as well as the presence of biochemical cues in the scaffold on
hES differentiation [72]. Philip et al. studied the effect of various ECM com-
ponents on differentiation of rhesus ES cells. Their in vivo results show that
the presence of cartrigel, an extract of cartilage matrix components, resulted
in enhanced musculoskeletal differentiation of the ES cells [222]. These re-
sults indicate that the differentiation of ES cells can be directed to a particular
lineage by using scaffolds containing ECM components derived from similar
tissues. Xu et al. developed a feeder-free culture system for the proliferation
of hES while retaining their undifferentiated state by exploiting the biological
functions of Matrigel which is rich in ECM components [223].
The ongoing discussion clearly indicates the need for designing biomate-
rial scaffolds with desired biological cues and physical properties for the con-
trolled differentiation of ES cells. To identify interactions between stem cells
with a large array of biomaterials and growth factors, Anderson et al. applied
high throughput microarray technology to screening biomaterials [319]. The
advantage of this approach is that it enables the screening of large libraries of
biomaterials in small quantities. Their findings indicate that certain bioma-
terials significantly induce the differentiation of hES cells into epithelial-like
cells, whereas other biomaterials support the differentiation only in the pres-
ence or absence of specific growth factors.
8
Chemical Integration of Engineered Tissue with Native Tissues
Biomaterials have played a significant role in creating tissue-engineered im-
plants and moving the field of regenerative medicine forward. The hurdle of
moving from in vitro design of tissue engineering systems to their in vivo
application still presents a challenge due to the lack of integration between
the implant and the host tissue. While biomaterials such as hydrogels may be
 
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