Although it is known that mechanical forces are needed for normal bone
development, the current understanding of how biophysical stimuli are
interpreted by and integrated with genetic regulatory mechanisms is limited.
Mechanical forces are thought to be mediated in cells by
βmechanosensitiveβ genes, but it is a challenge to
demonstrate that the genetic regulation of the biological system is dependant on
particular mechanical forces in vivo. We propose a new means of selecting
candidate mechanosensitive genes by comparing in vivo gene expression patterns
with patterns of biophysical stimuli, computed using finite element analysis. In
this study, finite element analyses of the avian embryonic limb were performed
using anatomically realistic rudiment and muscle morphologies, and patterns of
biophysical stimuli were compared with the expression patterns of four candidate
mechanosensitive genes integral to bone development. The expression patterns of
two genes, Collagen X (ColX) and Indian hedgehog (Ihh), were shown to colocalise
with biophysical stimuli induced by embryonic muscle contractions, identifying
them as potentially being involved in the mechanoregulation of bone formation.
An altered mechanical environment was induced in the embryonic chick, where a
neuromuscular blocking agent was administered in ovo to modify skeletal muscle
contractions. Finite element analyses predicted dramatic changes in levels and
patterns of biophysical stimuli, and a number of immobilised specimens exhibited
differences in ColX and Ihh expression. The results obtained indicate that
computationally derived patterns of biophysical stimuli can be used to inform a
directed search for genes that may play a mechanoregulatory role in particular
in vivo events or processes. Furthermore, the experimental data demonstrate that
ColX and Ihh are involved in mechanoregulatory pathways and may be key mediators
in translating information from the mechanical environment to the molecular
regulation of bone formation in the embryo