Genetic response to low-intensity ultrasound on mouse ST2 bone marrow stromal cells

Although low-intensity ultrasound (LIUS) is a clinically established procedure, the early cellular effect of LIUS on a genetic level has not yet been studied. The current study investigated the early response genes elicited by LIUS in bone marrow stromal cells (BMSCs) using global-scale microarrays and computational gene expression analysis tools. Mouse ST2 BMSCs were treated with LIUS [I(SATA), 25 mW/cm(2) for 20 min with a frequency of 1.11 MHz in a pulsed-wave mode (0.2-s burst sine waves repeated at 1 kHz)], then cultured for 0.5, 1 and 3 h at 37°C. The time course of changes in gene expression was evaluated using GeneChip(®) high-density oligonucleotide microarrays and Ingenuity(®) Pathway Analysis tools. The results were verified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). A single exposure of LIUS did not affect cell morphology, cell growth or alkaline phosphatase activity. However, 61 upregulated and 103 downregulated genes were identified from 0.5 to 3 h after LIUS treatment. Two significant gene networks, labeled E and H, were identified from the upregulated genes, while a third network, labeled T, was identified from the downregulated genes. Gene network E or H containing the immediate-early genes FBJ osteosarcoma oncogene and early growth response 1 or the heat shock proteins heat shock protein 1a/b was associated mainly with the biological functions of bone physiology and protein folding or apoptosis, respectively. Gene network T containing transcription factors fos-like antigen 1 and serum response factor was also associated with the biological functions of the gene expression. RT-qPCR indicated that the expression of several genes in the gene networks E and H were elevated in LIUS-treated cells. LIUS was demonstrated to induce gene expression after short application in mouse ST2 BMSCs. The results of the present study provide a basis for the elucidation of the detailed molecular mechanisms underlying the cellular effects of LIUS.