Pro-diff erentiating eff ects of red photobiomodulation on skeletal myoblasts: morpho-functional evidences

Adult skeletal muscle possesses the ability to regenerate lost damaged tissue mainly thanks to the activity of a small population of resident stem cells, namely satellite cells (SCs). In the case of chronic or severe damage, the functionality of SCs may be compromised by the occurrence of an aberrant fibrotic reparative response. Strategies aimed to improve the muscle intrinsic regenerative capacity while limiting the excessive deposition of fi brotic tissue may be promising. In this perspective, photobiomodulation (PBM) (i. e. application of light with 400-1100 nm wavelength using different laser or LED devices, power density less than 100 mW/cm2 and energy density less than 10 J/ cm2 at target) may represent a valid option based on its well-known pro-regenerative effects and increasing evidence of its antifibrotic potential. However, results on the PBM actual benefits on skeletal muscle are controversial and light-tissue interactions need to be better elucidated. To this aim we evaluated the effects of a treatment of red PBM (laser diode 635±5 nm, energy density: 0.4, 4 and 8 J/cm2, single exposure) on myoblastic cells undergoing differentiation and on differentiated cells (myotubes). Preliminary results obtained by morphological analyses (cell viability, myogenic markers, myotubes) and electrophysiological investigations (cell membrane passive properties and ion currents) suggest the capability of red PBM to positively affect myoblast differentiation. At the same time, PBM treatment did not alter myotube viability and dimension. Experiments are ongoing to explore the effects of red PBM on mitochondria and on myoblasts induced to differentiate on a liquid crystalline network used as a cell instructive scaffold to support a correct myogenic differentiation.