Building better bone grafts with light
Bone tissue engineering
and in vivo bioluminescence imaging are relatively new research fields, but the
latter is being used increasingly to aid the former.
Investigators in such diverse fields
as materials science and stem cell and molecular biology are working to improve
artificial grafts to treat patients who have large defects in their bones. Various
polymers and ceramics, and metals such as titanium, comprise the base structures,
or scaffolds, upon which bone cells are seeded and grown. However, quantifying the
success of potential replacement tissue depends not just on viewing a finished product,
but also on monitoring how the scaffold materials affect subsequent tissue formation,
control the release of bioactive compounds and create the proper environment for
tissue growth. Increasingly, this means observing bone tissue formation —
both natural and artificial — at the molecular level in small animals.
According to Jan de Boer and Clemens
van Blitterswijk of the University of Twente in Bilthoven and Clemens Löwik
of Leiden University Medical Center, both in the Netherlands, in vivo bioluminescence
imaging has great potential to provide information about the molecular interactions
that occur with bone formation.
In a review of noninvasive imaging
of bone tissue engineering, the authors provide a summary of bioluminescence imaging
techniques, focusing on the use of luciferase and its derivatives in transgenic
animals. They also discuss the application of imaging techniques toward the monitoring
of cell numbers and distribution across a tissue scaffold, of the differentiation
of osteogenic cells, and of inflammatory, apoptotic, vasculogenetic and signal transduction
processes.
They note that bioluminescence imaging
is constrained by two-dimensional imaging methods, which cannot resolve depth —
although recently introduced three-dimensional imaging systems may address this
issue — and by tissue scattering and absorption of light, which limit spatial
resolution. Nonetheless, ongoing improvements in imaging equipment, luciferase reporters
and software likely mean that bioluminescence imaging will strongly contribute to
the understanding of the in vivo dynamics of bone tissue engineering. (
Biomaterials,
March 2006, pp. 1851-1858.)
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