title: Ovariectomy sensitizes rat cortical bone to whole-body vibration.
abstract: 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.
authors: Bone Metabolic Unit, Scientific Institute San Raffaele, Via Olgettina 60, Milan 20132, Italy. a.rubinacci@hsr.it
authors: Alessandro
authors: A
authors: Rubinacci
authors: Massimo
authors: M
authors: Marenzana
authors: Francesco
authors: F
authors: Cavani
authors: Federica
authors: F
authors: Colasante
authors: Isabella
authors: I
authors: Villa
authors: Johannes
authors: J
authors: Willnecker
authors: Gian Luigi
authors: GL
authors: Moro
authors: Luigi Paolo
authors: LP
authors: Spreafico
authors: Marzia
authors: M
authors: Ferretti
authors: Francesca
authors: F
authors: Guidobono
authors: Gastone
authors: G
authors: Marotti
mesh_terms: 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