Modulating effect of low intensity pulsed ultrasound on the phenotype of inflammatory cells

Aims: The purpose of this study was toclarify the effect of low intensity pulsed ultrasound (LIPUS) on the phenotype of the inflammatory infiltrate in muscle tissue following acute injury. Main methods: Forty Wistar rats were submitted to cryoinjury of the tibialis anterior muscle and only half were treated with LIPUS. After 1, 2, 3 and 7 days macrophages and neutrophils were quantified. Key findings: With one day, LIPUS led to reductions in the number of neutrophils and M1 macrophages. After two days, muscles treated with LIPUS had fewer total macrophages and M1 macrophages, but a greater number of M2 macrophages. Muscles treated with LIPUS showed fewer macrophages after three and seven days. Significance: As the permanence of cells with pro-inflammatory and anti-inflammatory action can lead to the perpetuation of inflammation with consequent tissue damage and tissue fibrosis, respectively, the ability of LIPUS to modulate the occurrence of these cells demonstrates the therapeutic potential of this resource.