IADR Abstract Archives
Accelerated Chondral Growth of the Cranial Base Cartilage Upon Tensile Biomechanical Stimuli
The sphenooccipital synchondrosis (SOS) is one of the few centers of endochondral
osteogenesis in the cranial base. An enigma about the growth of the SOS stems from a
common belief that genetically programmed mitosis and apoptosis takes place with little
influence of exogenous biomechanical stimuli. Objective: We investigated whether the
SOS growth can be modulated by exogenous tensile biomechanical stimuli in a rabbit
model. Methods: Twenty-three male, 6-week-old, NZW rabbits were randomly allocated
into three groups: 1) dynamic tensile forces at 2 Newtons (N) and with f (frequency)=1
Hz, 2) static tensile forces of matching peak magnitude (2 N) with f=0 Hz and 3) sham
controls. Tensile biomechanical stimuli were delivered 20 min per day over 12 days,
resulting in a daily dosage of 1200 cycles per day (cpd) for dynamic stimuli and 1 cpd
for static stimuli. Upon euthanasia the SOS was harvested, decalcified, embedded,
sectioned at 8 micron each and stained with H&E and safranin O/fast green. Results:
Quantitative histomorphometric analysis demonstrated that both the total length and
overall area of the SOS treated with dynamic stimuli were significantly higher than sham
controls and static stimuli (p < 0.01). Cell counting revealed that the proliferating zone
of dynamically stimulated SOS samples contained significantly more chondrocytes than
the corresponding zone of sham controls and statically stimulated samples (p < 0.01).
Conclusion: Chondral growth of the sphenooccipital synchondrosis is modulated by
exogenous biomechanical stimuli beyond the amount that is genetically programmed to
take place. These findings provide the basis for a hypothesis that the growth and
maturation of the growth plate are regulated by postnatal upregulation of certain genes
upon not only extrinsic, but also intrinsic biomechanical stimuli. Supported by Whitaker
Biomedical Engineering Research Grant and NIH grants, DE 13964 and DE13088.