Strategy for a Biomimetic Paradigm in Dental and Craniofacial Tissue Engineering - Biomimetics: Advancing Nanobiomaterials and Tissue Engineering - page 124

6.3 Developmental Biology in Dental and

Craniofacial Tissue Engineering: Biomimetics in
Development and Growth (e.g. model of wound
healing)

An understanding of the complex interfaces that exist between proteins,
minerals, cells and their environment in biological systems is critically
important in craniofacial development because reactions and interactions
occurring at these interfaces govern their properties and functionalities. A
new strategy of tissue engineering is to mimic the hierarchical structural
assemblages and mechanisms of simplicity and elegance that are con-
served throughout generations and species.
The craniofacial region is the most developmentally and anatomi-
cally sophisticated part in vertebrates. Its development and growth is a
complex, strictly controlled continuous biological process that involves
an interrelationship between its various components developmentally,
structurally and functionally. It could be broadly divided into three over-
lapping stages. The fi rst stage is the soft tissue stage during which the
framework of the craniofacial region is formed. During the second stage,
the chondrocranium together with the cartilaginous facial skeleton are
formed, Meckel's cartilage in the lower jaw and nasal capsule in the naso-
maxillary complex. The third stage (consolidation stage) is characterized
by formation of skeletal and muscular elements.
The fi rst stage of human craniofacial development begins at the end of
the second week of prenatal life by formation of the prochordal plate in
bilaminar embryonic disc. Formation of the prochordal plate establishes
the antro-posterior axis of the embryo and determines the future posi-
tion of the buccopharyngeal membrane. On the third week, primitive
streak mesoderm or embryonic mesoderm emerges to form the trilaminar
embryonic disc (Gastrulation). Later on that week, the neural plate, folds
and forms a tube together with formation of a distinctive type of ecto-
mesenchymal cells or the neural crest cells. Induction of neural crest cells
requires contact mediated interactions between surface ectoderm and
neuroepithelium [41]. Interestingly, BMP signaling seems to play a critical
role in positioning the border of the neural plate as well as induction and
migration of neural crest cells, since BMP4 and BMP7 could substitute for
non-neural ectoderm in neural crest cell induction [42].
Concomitant with their induction along the dorsolateral edge of the
neural plate, neural crest cells undergo complete or partial epithelial-
mesenchymal transition that is marked by changes in cell adhesion and
cytoarchitecture. This delamination of neural crest cells depends on regu-
lated cadherin expression since overexpression of neuroepithelial cadher-
ins prevents neural crest emigration [43]. Following delamination from