Ovariectomy sensitizes rat cortical bone to whole-body vibration.
This study was designed to determine the modulatory effect of estrogen on mechanical stimulation in bone. Trabecular and cortical bone compartments of ovariectomized rats exposed to whole-body vibration of different amplitudes were evaluated by peripheral quantitative computed tomographic (pQCT) analysis and histomorphometry and compared to controls not exposed to vibration. Rats underwent whole-body vibration (20 minutes/day, 5 days/week) on a vibration platform for 2 months. The control rats were placed on the platform without vibration for the same time. We divided rats into six groups: a sham control (SHAM); a sham vibrated (SHAM-V) at 30 Hz, 0.6 g; a SHAM-V at 30 Hz, 3g; an ovariectomized control (OVX); an ovariectomized vibrated (OVX-V) at 30 Hz, 0.6 g; and an OVX-V at 30 Hz, 3g. In vivo, pQCT analyses of the tibiae were performed at the start of the experiment and after 4 and 8 weeks. After 8 weeks the tibiae were excised for histomorphometric and for in vitro pQCT analyses. In the SHAM-V group, vibration had no effect upon the different bone parameters. In the OVX-V group, vibration induced a significant increase compared to the OVX group of the cortical and medullary areas (P < 0.01) and of the periosteal (P < 0.01) and endosteal (P < 0.05) perimeters at the 3 g vibration. The strain strength index increased in the OVX-V group significantly (P < 0.01) at the higher vibration. The results showed that low-amplitude, high-frequency whole-body vibration is anabolic to bone in OVX animals. The osteogenic potential is limited to the modeling of the bone cortex and depends on the amplitude of the vibration.
Rubinacci
Alessandro
A
Bone Metabolic Unit, Scientific Institute San Raffaele, Via Olgettina 60, Milan 20132, Italy. a.rubinacci@hsr.it
Marenzana
Massimo
M
Cavani
Francesco
F
Colasante
Federica
F
Villa
Isabella
I
Willnecker
Johannes
J
Moro
Gian Luigi
GL
Spreafico
Luigi Paolo
LP
Ferretti
Marzia
M
Guidobono
Francesca
F
Marotti
Gastone
G
D000818:Animals; D015519:Bone Density; D001842:Bone and Bones / Q000473:pathology* / Q000648:ultrastructure; D003430:Cross-Sectional Studies; D005260:Female; D008855:Microscopy, Electron, Scanning; D010052:Ovariectomy / Q000379:methods*; D010805:Physical Conditioning, Animal; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D013977:Tibia / Q000473:pathology / Q000648:ultrastructure; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods; D014732:Vibration