Musculoskeletal Response to Whole-Body Vibration During Fracture Healing in Intact and Ovariectomized Rats

Abstract

This study investigated the effect of vibration on bone healing and muscle in intact and ovariectomized rats. Thirty ovariectomized (at 3 months of age) and 30 intact 5-month old female Sprague-Dawley rats underwent bilateral metaphyseal osteotomy of tibia. Five days later, half of the ovariectomized and of the intact rats were exposed to whole-body vertical vibration (90 Hz, 0.5 mm, 4 × g acceleration) for 15 min twice a day during 30 days. The other animals did not undergo vibration. After decapitation of rats, one tibia was used for computed tomographic, biomechanical, and histological analyses; the other was used for gene expression analyses of alkaline phosphatase (Alp), osteocalcin (Oc), tartrate-resistant acid phosphatase 1, and insulinlike growth factor 1. Serum Alp and Oc were measured. Mitochondrial activity, fiber area and distribution, and capillary densities were analyzed in M. gastrocnemius and M. longissimus. We found that vibration had no effect on body weight and food intake, but it improved cortical and callus densities (97 vs. 99%, 72 vs. 81%), trabecular structure (9 vs. 14 trabecular nodes), blood supply (1.7 vs. 2.1 capillaries/fiber), and oxidative metabolism (17 vs. 23 pmol O2/s/mg) in ovariectomized rats. Vibration generally increased muscle fiber size. Tibia biomechanical properties were diminished after vibration. Oc gene expression was higher in vibrated rats. Serum Alp was increased in ovariectomized rats. In ovariectomized rats, vibration resulted in an earlier bridging; in intact rats, callus bridging occurred later after vibration. The chosen vibration regimen (90 Hz, 0.5 mm, 4 × g acceleration, 15 min twice a day) was effective in improving musculoskeletal tissues in ovariectomized rats but was not optimal for fracture healing.

Effect of the Lipoxygenase Inhibitor Baicalein on Muscles in Ovariectomized Rats

“…If the standardized tibia osteotomy, performed bilaterally in all rats, would have any effect on muscles, it would be similar in all treatment groups. On the basis of previous studies [35, 36], we assumed that, at around this time point, that is, 8 weeks after OVX, the rats would have developed osteoporosis with sarcopenia. Baicalein treatments were started one day after osteotomy.…”

Identification of a Vibration Regime Favorable for Bone Healing and Muscle in Estrogen-Deficient Rats

“…In groups 3, 4, 5, and 6, OVX rats were treated with either 35, 50, 70, or 90 Hz of vertical vibration, respectively. Vibrations were applied using a previously described device [10] consisting of a vibration desk, two alternating current engines, and a force transducer that adjusts the vibration frequency from 35 to 90 Hz.…”

“…The cortical width and density distal to the osteotomy line, periosteal callus width and density, endosteal callus density, and trabecular density and width were measured in microradiographs (Fig. 1c) [10]. The callus area (μm 2 ) was measured according to the ROI and fluorescence labeling in histological sections (Fig.…”

“…The effects of different vibration-loading parameters (frequency, magnitude, duration) on the musculoskeletal system are well understood, partly because of the large variability in the vibration regimes used in clinical and experimental trials. Different vibration regimes can either stimulate bone healing or impair the bone regeneration process [9, 10]. Similarly, WBV may exert beneficial or adverse effects on muscle tissue [10].…”

“…Different vibration regimes can either stimulate bone healing or impair the bone regeneration process [9, 10]. Similarly, WBV may exert beneficial or adverse effects on muscle tissue [10]. …”