title: Stimulation of osteoblast differentiation with guided ultrasound waves.
abstract: BACKGROUND
  Ultrasound 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?
  
  
  METHODS
  In 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/cm(2) for 20 min per day was applied to MC3T3 osteoblast-like cells, which were placed 30-75 mm distant from the transducer.
  
  
  RESULTS
  The 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).
  
  
  CONCLUSIONS
  We 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.
authors.affiliation: Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 USA.
authors.forename: James
authors.initials: J
authors.lastname: Macione
authors.affiliation: Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Long
authors.affiliation: Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 USA.
authors.forename: Sterling
authors.initials: S
authors.lastname: Nesbitt
authors.affiliation: Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Wentzell
authors.affiliation: Department of Biomedical Engineering, Indiana University Purdue University Indianapolis, Indianapolis, IN 46202 USA.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Yokota
authors.affiliation: Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 USA.
authors.forename: Vaibhav
authors.initials: V
authors.lastname: Pandit
authors.affiliation: Department of Biomedical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 USA.
authors.forename: Shiva
authors.initials: S
authors.lastname: Kotha