Differential responses of myoblasts and myotubes to photobiomodulation are associated with mitochondrial number

Abstract

Objective Photobiomodulation (PBM) is the application of light to promote tissue healing. Current indications suggest PBM induces its beneficial effects in vivo through upregulation of mitochondrial activity. However, how mitochondrial content influences such PBM responses have yet to be evaluated. Hence, the current study assessed the biological response of cells to PBM with varying mitochondrial contents. Methods DNA was isolated from myoblasts and myotubes (differentiated myoblasts), and mitochondrial DNA (mtDNA) was amplified and quantified using a microplate assay. Cells were seeded in 96‐wellplates, incubated overnight and subsequently irradiated using a light‐emitting diode array (400, 450, 525, 660, 740, 810, 830 and white light, 24 mW/cm2, 30‐240 seconds, 0.72‐5.76J/cm2). The effects of PBM on markers of mitochondrial activity including reactive‐oxygen‐species and real‐time mitochondrial respiration (Seahorse XFe96) assays were assessed 8 hours post‐irradiation. Datasets were analysed using general linear model followed by one‐way analysis of variance (and post hoc‐Tukey tests); P = 0.05). Results Myotubes exhibited mtDNA levels 86% greater than myoblasts (P < 0.001). Irradiation of myotubes at 400, 450 or 810 nm induced 53%, 29% and 47% increases (relative to non‐irradiated control) in maximal respiratory rates, respectively (P < 0.001). Conversely, irradiation of myoblasts at 400 or 450 nm had no significant effect on maximal respiratory rates. Conclusion This study suggests that mitochondrial content may influence cellular responses to PBM and as such explain the variability of PBM responses seen in the literature.

Comparative Effect of Low‐intensity Laser Radiation in Green and Red Spectral Regions on Functional Characteristics of Sturgeon Sperm

“…At the same time, according to the data of the studies (78,(87)(88)(89), carried out at equal energy doses, the stimulatory effect of green light on cell culture was higher compared with the effect of radiation in red spectral region.…”

Wavelength- and irradiance-dependent changes in intracellular nitric oxide level

“… 59 Although red (630 to 670 nm) and NIR (780 to 940 nm) wavelengths are the most commonly used in PBM applications, 2 , 5 , 17 , 18 , 60 – 63 various studies have provided evidence of PBM effects in the blue and green wavelength ranges. 2 , 5 , 17 , 18 , 62 – 66 As such, we conducted assays to determine if any of these wavelengths also had the ability to increase NO levels in this system. We chose 635 and 808 nm as our red and NIR lasers, respectively, as these wavelengths are common in PBM applications.…”

“…5,62,64 Our choice of 532-nm green was the best available laser that matched this wavelength range with sufficient power. Blue wavelengths are becoming more frequently used in PBM, and while many of these use wavelengths in the 400-to 420-nm range, exposures from 445 to 450 nm are not uncommon, 63,65,66 The 447-nm laser we chose fell roughly in the center of this range and lies near the soret band for COX at 443 nm. 67 Therefore, we conducted exposures to 635-nm red, 447-nm blue, 532-nm green, and 808-nm NIR lasers ( For all four wavelengths, exposed cells exhibited statistically greater DAF-FM fluorescence compared to control cells at all time points after 30 min, indicating increased levels of free NO.…”

Photobiomodulation of oral fibroblasts stimulated with periodontal pathogens

“…Detailed experimental procedures have been previously reported [42]. Calculated beam area is described in Table 1 and representative beam profile images have been previously reported by Serrage et al [43].…”

“…Radiant exposure is also reported for each time interval (30-480 s) and was calculated through multiplication of average irradiance output (W/cm 2 ) with irradiation time (s). Experimental design and setup are described in detail in Serrage et al [43]. All parameters were determined over a 240-s irradiation period.…”