Biomedical Engineering Reference
In-Depth Information
Chapter 14
Engineering Graded Tissue Interfaces
Neethu Mohan and Michael Detamore
14.1 Complexity at the Interface
Tissues in biological systems are arranged in discrete layers with gradient
interfaces, in which each layer has a definite role. Together they form a functional
organ. The interface has a complex structure with tissue-specific cell types, extra-
cellular matrix, biological signals, and mechanical properties. At the interface,
there is a well-defined pattern of chemical and physical gradients to enable a
smooth transition from one tissue to another with different functions. The impor-
tance of protein and chemical gradients during development, chemotaxis [ 1 , 2 ],
capillary sprouting, wound healing [ 3 - 5 ], and axonal growth in nervous tissue [ 6 ]is
well documented. Developmental biologists have for many years known the impor-
tance of cell organization, boundaries, and interfaces between tissues in regulating
tissue development. The three-dimensional form of organisms is achieved through a
process called pattern formation. The general features of animal body plans are
initially laid out during embryogenesis in broad strokes. The differential fates are
specified along the rostral-caudal axis. During subsequent development, the cells
that make up the field itself are defined; further specific signaling centers are
established within the field, which serve to provide positional information; and
finally, cells differentiate in response to additional cues according to their already-
encoded positional information [ 7 ].
A similar patterning is present at tissue interfaces. The most widely studied
interfaces include cartilage-bone, ligament-bone, tendon-bone, tendon-ligament,
and dentin-enamel junctions. Transitions are observed in composition, architec-
ture, mechanical properties, and biological functions. The chemical gradients
constitute the gradient in extracellular matrix (ECM) proteins, growth factors,
and other biochemical components. The spatial localization and gradient length of
N. Mohan • M. Detamore ( * )
Department of Chemical and Petroleum Engineering, University of Kansas, Lawrence, KS, USA
e-mail: ;
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