Efficacy of femtosecond lasers for application of acupuncture therapy
Lasers Med Sci
Efficacy of femtosecond lasers for application of acupuncture therapy
Mika Ohta 0 1 2 3 4
Yoichiroh Hosokawa 0 1 2 3 4
Naoya Hatano 0 1 2 3 4
Aki Sugano 0 1 2 3 4
Akihiko Ito 0 1 2 3 4
Yutaka Takaoka 0 1 2 3 4
0 Graduate School of Materials Science, Nara Institute of Science and Technology , Nara 630-0912 , Japan
1 Genome Science Research Unit, Life Science Research Center, Kobe Tokiwa University , Kobe 653-0838 , Japan
2 Division of Medical Informatics and Bioinformatics, Kobe University Hospital , Kobe 650-0017 , Japan
3 Department of Pathology, Kindai University Faculty of Medicine , Osaka 589-8511 , Japan
4 The Integrated Center for Mass Spectrometry, Kobe University Graduate School of Medicine , Kobe 650-0017 , Japan
Acupuncture treatment utilizes the stimulation of metal acupuncture needles that are manually inserted into a living body. In the last decades, laser light has been used as an alternative to needles to stimulate acupuncture points. We previously reported suppression of myostatin (Mstn) gene expression in skeletal muscle by means of femtosecond laser (FL) irradiation, after electroacupuncture, in which acupunct u r e n e e d l e s a r e s t i m u l a t e d w i t h a l o w - f r e q u e n c y microcurrent. The purpose of the study here was to investigate the efficacy of FL irradiation in mouse skeletal muscle with regard to protein synthesis. After irradiation of the hindlimbs, we first analyzed Mstn gene expression and Mstn protein level in the skeletal muscle. We then evaluated phosphorylation of the mammalian target of rapamycin (mTOR) and its downstream target 70-kDa ribosomal protein S6 kinase (p70S6K). The results showed that FL irradiation significantly reduced the amount of Mstn protein and enhanced the phosphorylation of p70S6K in of the mTOR/S6K signaling pathway. We suggest that FL irradiation activated the protein synthetic pathway in the skeletal muscle. In conclusion, we determined that FL irradiation can serve as an alternative for acupuncture needles and has the potential of being a new non-invasive acupuncture treatment of skeletal muscle.
Femtosecond laser; Acupuncture therapy; Skeletal muscle; Myostatin; mTOR; p70S6K
Introduction
Low-level lasers have been used in laser acupuncture, and
their analgesic effects have been reported [
1, 2
]. Low-level
lasers normally generate heat during irradiation, whereas heat
generation at femtosecond laser (FL) focal spots is suppressed
because of effective conversion of energy to kinetic waves [3].
In our previous FL study, we did not detect heat denaturation
in animal tissues after irradiation [
4
]. The damage caused by
the irradiation was observed in the epidermis and dermis, and
the diameter of the damaged area and its depth were
approximately 400 and 1100 μm, respectively. Such effects on
animal tissue are similar to those of acupuncture treatment with
acupuncture needles. Therefore, we believed that the FL was a
good candidate for laser acupuncture.
We also elucidated expression of the Mstn gene after
electroacupuncture (EA) treatment, which is one type of
acupuncture stimulation [
5
]. Mstn, a member of the transforming
growth factor-β superfamily, is a potent negative regulator of
skeletal muscle mass [
6
]. Mstn has inhibited activation of
satellite cells in skeletal muscle [
7
]. Mstn inactivation induced
skeletal muscle hypertrophy in humans and mice [
8, 9
]. Our
previous study indicated that EA treatment suppressed Mstn
expression, which led to a satellite cell-related proliferative
reaction and repair in skeletal muscle [5]. Other results
showed that EA-induced Mstn gene suppression may help
prevent muscle atrophy in mice [
10
]. We subsequently found
suppression of expression of the Mstn gene in mouse skeletal
muscle after FL irradiation, just as with EA [
4, 11
].
On the basis of the results of our previous studies, we
expected activation of the protein synthetic pathway because
Mstn inhibits activation of the Akt/mTOR pathway [
12, 13
].
The Akt/mTOR pathway regulates protein synthesis and is
upregulated during skeletal muscle hypertrophy. The mTOR/
S6K pathway includes the 70-kDa ribosomal protein S6
kinase (p70S6K) protein downstream, and the protein functions
in the mTOR/S6K signaling pathway, which regulates protein
synthesis and cell growth [14].
This study aimed to elucidate the efficacy of FL irradiation
of mouse skeletal muscle. We investigated Mstn gene
expression, the amount of Mstn protein, and phosphorylation of
mTOR and p70S6K after irradiation.
Materials and methods
Animals and treatment
C57BL/6J male mice, 8 weeks old, were purchased from
Charles River Laboratories, Yokohama, Japan. We divided
the mice into three groups: controls, n = 5; acupuncture
(ACP) stimulation, n = 6; and FL, n = 6. After anesthesia to
all the three groups, hair on the hind legs of FL mice was
removed by using hair removal cream, and FL treatment
focused on the lower legs. A single-shot (...truncated)