Mechanobiology of Bone - Engineered Bone: Tissue Engineering Intelligence Unit - page 37

Figure 6. Tissue differentiation in fracture healing and DOG is affected by many factors. Here is depicted
a simplified scheme of how mechanical factors can play a role in this process. Mechanical load stimulates
cells to produce cytokines and growth factors, which affect cell differentiation and proliferation. It may also
directly stimulate the differentiation of a cell towards a certain phenotype. Mechanical load also stimulates
matrix production, which in turn affects the tissue properties and thereby the mechanical loads on the cells.
is influenced by mechanical loading. We are a long way from understanding the complex mul-
tifactorial process of fracture healing and DOG. Also the precise role of mechanical factors is
still poorly understood. On the one hand, the gradual stiffening and stabilization of the tissue
is required for ossification. On the other hand, tissue deformation plays a role in the stimula-
tion of cell proliferation, matrix production and the release of various growth factors. The
interaction of these factors result in the progressive development of the tissue (Fig. 6). Pres-
ently, in vitro experiments are only able to mimic aspects of this process. In vivo bone engineer-
ing is, however, a very promising practice. Several factors determining the success of bone
formation can be identified. These factors include the release of growth factors and cytokines,
the availability of a population of mesenchymal stem cells, good blood supply and appropriate
mechanical conditions. The future of bone engineering lies in the manipulation of these fac-
tors. The possibility of treatments using growth factors, such as BMP-2, has already been stud-
ied extensively. 125 In DOG, the appropriate cellular and chemical environment is created by
the callus tissue and the existing bone. Bone development is further stimulated by manipula-
tion of mechanical factors.
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