A 2-Wavelength Low Level Laser Irradiation In-duces More In Vitro Cell Viability of Human Adipose Stem Cells Than Human Bone Marrow-Drived Stem Cells

Background: The goal of the current experiment is to explore the influence of combined and/or single applications of red and near infrared (NIR) photobiomodulation (PBM) irradiation at dif-ferent energy densities and sessions on cell viability, population doubling time (PDT), and apoptosis of in vitro cultures of human bone marrow-derived mesenchymal stem cells (hBMMSCs) and adipose-derived mesenchymal stem cells (hASCs).Materials and Methods: Both in vitro hBMMSCs and hASCs were irradiated via 36 protocols that consisted of 4 different la-ser wavelengths (He-Ne laser, 630 nm, 810 nm, 630+810 nm); 3 different energy densities (0.6 J/cm2, 1.2 J/cm2, 2.4 J/cm2); and 3 different PBM sessions (1, 2, and 3).Results: Irradiation with the 630 nm PBM significantly stim-ulated cellular viability and decreased PDT of both types of MSCs. The 630+810 nm NIR laser was statistically more ef-fective and presented a synergistic effect compared to sole ap-plications of the 630 nm and 810 lasers in terms of hBMMSC viability and PDT. However, there was significantly greater cell viability and PDT in hASCs irradiated 3 times with the 660+810 nm NIR laser at an energy density of 2.4 J/cm2 com-pared to the control group and hBMMSCs irradiated with the same protocol. PBM with 630 nm and the combined 630+810 nm wavelengths had a stimulatory effect on cell viability of in vitro hBMMSCs and hASCs.Conclusion: However, the 630+810 nm PBM was statistically more effective. hASCs had a statistically better response to PBM in terms of cell viability and PDT than hBMMSCs .