Low-energy shock waves evoke intracellular Ca2+ increases independently of sonoporation

Toru Takahashi,Shigeru Tada,Keiichi Nakagawa,Akira Tsukamoto

doi:10.1038/s41598-019-39806-x

Toru Takahashi, Shigeru Tada + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-39806-x

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Abstract

Low-energy shock waves (LESWs) accelerate the healing of a broad range of tissue injuries, including angiogenesis and bone fractures. In cells, LESW irradiations enhance gene expression and protein synthesis. One probable mechanism underlying the enhancements is mechanosensing. Shock waves also can induce sonoporation. Thus, sonoporation is another probable mechanism underlying the enhancements. It remains elusive whether LESWs require sonoporation to evoke cellular responses. An intracellular Ca2+ increase was evoked with LESW irradiations in endothelial cells. The minimum acoustic energy required for sufficient evocation was 1.7 μJ/mm2. With the same acoustic energy, sonoporation, by which calcein and propidium iodide would become permeated, was not observed. It was found that intracellular Ca2+ increases evoked by LESW irradiations do not require sonoporation. In the intracellular Ca2+ increase, actin cytoskeletons and stretch-activated Ca2+ channels were involved; however, microtubules were not. In addition, with Ca2+ influx through the Ca2+ channels, the Ca2+ release through the PLC-IP3-IP3R cascade contributed to the intracellular Ca2+ increase. These results demonstrate that LESW irradiations can evoke cellular responses independently of sonoporation. Rather, LESW irradiations evoke cellular responses through mechanosensing.

Highlights

Shock waves were first applied in medicine as extracorporeal shock wave therapies (ESWT) in the early 1980 s
To obtain a spatial distribution of acoustic energy, peak pressures of shock waves were measured along the X- and Y-axes, which were set perpendicular to the shock-wave transmission (Fig. 1A, Supplementary S1A)
The intracellular Ca2+ increase did not involve microtubules (Fig. 4A). These results indicate that the intracellular Ca2+ increase evoked by Low-energy shock waves (LESWs) involves a part of cytoskeletons

Summary

Introduction

Shock waves were first applied in medicine as extracorporeal shock wave therapies (ESWT) in the early 1980 s. Through the transient pores formed by shock waves, intracellular biomolecules could be released into extracellular space Those released biomolecules can evoke cellular signals in pore-formed cells themselves or in neighboring cells. Cellular responses those were evoked by LESW irradiations were detected as a result of enhancements of gene expression and protein syntheses. Those detections require large numbers of cells. By detecting an intracellular Ca2+ increase, it is expected that the acoustic energy of shock waves required to detect a cellular response could be suppressed. Acoustic energy, an intracellular Ca2+ increase is expected to be evoked under conditions in which sonoporation is suppressed or excluded

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