Abstract
BackgroundUltrasound induces mechanical vibration and heat, causing differentiation and proliferation in osteoblasts. All known in vitro evaluations of ultrasound are, however, performed with longitudinal ultrasound waves. We addressed a question: Do other forms of ultrasound waves, such as guided waves (longitudinal and guided flexural) transduced at a remote location, enhance differentiation of osteoblast cells?MethodsIn this study, we employed guided Lamb waves that were induced in a borosilicate glass slide (cortical bone mimic). An average energy of 10–30 mW/cm2 for 20 min per day was applied to MC3T3 osteoblast-like cells, which were placed 30–75 mm distant from the transducer.ResultsThe result revealed that guided waves significantly stimulated the differentiation and mineralization of MC3T3 cells. In particular, guided waves elevated mRNA expression levels of bone formation-related genes such as alkaline phosphatase, osteopontin, osteocalcin, osteoprotegerin, and bone sialoprotein on days 8 and 16. In addition, the amount of mineralization found via Alizarin red staining was increased by 157 % (p = 0.034). The amount of mineralization was found to be independent of distance from the transducer (p = 0.967).ConclusionWe demonstrate herein that ultrasound in a form of guided Lamb waves is capable of inducing osteoblast differentiation in vitro, and it may enable the stimulation of osteoblasts in vivo over a distance from the site of ultrasound application.
Highlights
Ultrasound induces mechanical vibration and heat, causing differentiation and proliferation in osteoblasts
The bone is treated via longitudinal waves, allowing waves to travel through soft tissue and reach the outer cortical surface
We explore the use of guided waves through a stimulated cortex in an effort to stimulate in vitro cells with guided Lamb waves
Summary
Ultrasound induces mechanical vibration and heat, causing differentiation and proliferation in osteoblasts. We addressed a question: Do other forms of ultrasound waves, such as guided waves (longitudinal and guided flexural) transduced at a remote location, enhance differentiation of osteoblast cells?. For instance, it is utilized to evaluate mechanical properties of bone in which guided waves are induced into the cortical bone [1,2,3,4]. Ultrasound in a form of longitudinal waves has been used to enhance bone growth and repair fracture including nonunion [7,8,9,10,11,12]. The waves can have conversion to shear and longitudinal components [16], even when induced at an angle to try to isolate these wave components [17]
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