Abstract
To better understand the molecular mechanism underlying cellular responses to low-intensity pulsed
ultrasound (LIPUS), we investigated gene expression profiles in mouse MC3T3-E1 preosteoblastic cells
exposed to LIPUS using DNA microarray and bioinformatics analysis tools. Although treatment of the cells
with a single 20-min LIPUS (1.5 MHz, 30 mW/cm2; SAFHS 4000J; Teijin Pharma, Ltd.) did not affect the cell
growth or alkaline phosphatase activity (an osteoblast differentiation marker), the treatment significantly
increased the mRNA level of BGLAP, an osteoblast differentiation marker protein. Microarray analysis
demonstrated that 38 genes were up-regulated and 37 genes were down-regulated by 1.5-fold or more in the
cells treated with LIPUS. Gene network analysis also demonstrated that the gene network U contained many
up-regulated genes that were mainly associated with bone morphology in the category of biological functions
of skeletal and muscular system development and function. The biological function of the gene network D,
which contained down-regulated genes, was associated with gene expression, the cell cycle, and connective
tissue development and function. These findings will provide a basis for understanding the detailed molecular
mechanisms of the LIPUS response in osteoblasts.
