Geometric and material contributions to whole bone structural behavior in GDF-7-deficient mice.
The growth/differentiation factors (GDFs) are a subfamily of bone morphogenetic proteins (BMPs) known to play a role in a variety of skeletal processes. Previous work using the brachypod mouse demonstrated that mice deficient in GDF-5 have long bones with diminished material properties and ash content compared with control littermates. Our aim was to examine the role of a related GDF family member, GDF-7 (BMP-12), in cortical bone by examining the geometric and material contributions to whole bone structural behavior in GDF-7-deficient mice. Femora from 16-week-old GDF-7 -/- animals had significantly smaller bone cross-sectional geometric parameters (e.g., -20% medial/lateral and anterior/posterior moments of inertia). Despite having smaller bone cross-sections, all structural parameters obtained from four-point bending tests were comparable to those of wild-type bones due to elevated cortical bone material properties (+18% modulus of elasticity, +28% yield strength, and +18% ultimate strength). No significant differences in ash content or collagen content were detected, however. These data suggest that GDF-7 deficiency is associated with elevated cortical bone material properties that compensate for decreased geometric properties, thereby preserving bone structural integrity. The compositional and/or microstructural bases for these altered material properties remain to be determined, however.
Maloul
A
A
Picker Engineering Program, Smith College, Northampton, Massachusetts 01063, USA.
Rossmeier
K
K
Mikic
B
B
Pogue
V
V
Battaglia
T
T
D000818:Animals; D001696:Biomechanical Phenomena; D019485:Bone Morphogenetic Proteins / Q000172:deficiency* / Q000235:genetics; D019245:Compressive Strength; D004548:Elasticity; D005260:Female; D005269:Femur / Q000378:metabolism / Q000473:pathology* / Q000502:physiology*; D055412:Growth Differentiation Factors; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D013314:Stress, Mechanical; D016474:Weight-Bearing
D019485:Bone Morphogenetic Proteins; C499471:Gdf7 protein, mouse; D055412:Growth Differentiation Factors