Biomedical Engineering Reference
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and bone diseases utilizing the zebrafi sh system were fi rst proposed by
Cui et al. from 1999 [47]. Investigations have shown that zebrafi sh have
an endochondral ossifi cation behavior similar to that of human bone [48].
Although there is no complete Haversian system in the zebrafi sh skeleton,
it does have both the lamellar structure and the impressive hierarchical
organization consistent with the description of human long bone. Together
with its predominance in studies of systematic mutagenesis using recent
advances in genetic techniques, zebrafi sh are thought to provide a poten-
tially powerful and simple model system for the study of bone mineraliza-
tion and bone diseases at the molecular level [49]. Therefore, it is of great
importance to investigate the mineralization characteristics of collagen
fi brils in zebrafi sh skeleton, which could have the potential to provide fur-
ther but simplifi ed insight in understanding the bone structure-function
relations.
As illustrated in Figure 2.4, there are also seven-level hierarchical of
organization in zebrafi sh skeletal bone with levels ranging in scale from
micrometers to nanometers [14, 20, 49, 50]. In the zebrafi sh system, the
basic building block of bone material is that of the mineralized collagen
fi bril (level 2), which itself is composed of a very hard material, the min-
eral, and a much softer material, the collagen fi brils (level 1). Mineralized
collagen fi brils are always present in bundles or arrays aligned along
their length (level 3). These fi bril arrays are organized into two common
patterns-arrays of parallel fi brils and a plywood-like structure (level 4).
At a higher level of organization, the initially deposited bone undergoes
internal remodeling to form the circular lamellar structure bone with a
central canal for the notochord and two arches for the neural tube and
blood vessels from the dorsal and ventral sides of the centra (level 5).
Levels 6 refers to vertebrae and levels 7 refers to the whole skeletal bone.
The formation and organization of mineralized collagen fi brils in
zebrafi sh bone are similar to those of human Haversian system. Cui et al.
Level 1 Major components
Level 3 Fibril array
Level 5 Lamellar structure
Level 7 Skeleton bone
Level 2 Mineralized collagen fibril
Level 4 Fibril array patterns
Level 6 Vertebra
Figure 2.4 The seven hierarchical levels of organization of the zebrafi sh skeleton
bone. Reprinted with permission from [50].
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