Abstract
ObjectiveThis study aimed to investigate the effects of low-magnitude, high-frequency vibration with rest days on bone quality at multiple levels.MethodsForty-nine three-month-old male Wistar rats were randomly divided into seven groups, namely, vibrational loading for X day followed by X day rest (VLXR, X = 1, 3, 5, 7), vibrational loading every day (VLNR), tail suspension (SPD), and baseline control (BCL). One week after tail suspension, rats were loaded by vibrational loading (35 Hz, 0.25 g, 15 min/day) except SPD and BCL. Fluorescence markers were used in all rats. Eight weeks later, femora were harvested to investigate macromechanical properties, and micro-computed tomography scanning and fluorescence test were used to evaluate microarchitecture and bone growth rate. Atomic force microscopy analyses and nanoindentation test were used to analyze the nanostructure and mechanical properties of bone material, respectively. Inductively coupled plasma optical emission spectroscopy was used for quantitative chemical analyses.ResultsMicroarchitecture, mineral apposition rate and bone formation rate and macromechanical properties were improved in VL7R. Grain size and roughness were significantly different among all groups. No statistical difference was found for the mechanical properties of the bone material, and the chemical composition of all groups was almost similar.ConclusionsLow-magnitude, high-frequency vibration with rest days altered bone microarchitecture and macro-biomechanical properties, and VL7R was more efficacious in improving bone loss caused by mechanical disuse, which provided theoretical basis and explored the mechanisms of vibration for improving bone quality in clinics.
Highlights
Bone tissue is a complex composite biological material with the ability for functional adaptation
All rats were randomly divided into seven groups, namely, vibrational loading for X day followed by X day rest (VLXR, X = 1, 3, 5, 7), vibrational loading every day (VLNR), tail suspension (SPD), and baseline control (BCL)
Further groups were created as follows: vibrational loading for 3 d followed by 3 d rest (VL3R, n = 7), vibrational loading for 5 d followed by 5 d rest (VL5R, n = 7), vibrational loading for 7 d followed by 7 d rest (VL7R, n = 7), and no rest day or vibrational loading every day (VLNR, n = 7)
Summary
Bone tissue is a complex composite biological material with the ability for functional adaptation. Mechanical environment is an important factor in controlling and influencing bone structure. Osteoporosis is a systemic skeletal disease characterized by low bone mass and microarchitecture deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture [1]. Many factors contribute to onset of bone loss. For astronauts staying four to six months in space, the mineral content of lower limb bones decreases remarkably, and the rate of loss of bone mineral density (BMD) is almost 1.6% per month [2,3]. In a gravitational environment for the duration of space travel, deterioration of some bone structures is irreversible though the bone mass has started to increase [4]
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