Fluence and wavelength of low intensity laser Irra Diation affect Acti Vity and Pro Liferation of human adipose derived stem cells

Background: Stem cells are undifferentiated cells that divide to replenish dying cells and regenerate damaged tissue. Low Intensity Laser Irradiation (LILI) has been shown to increase stem cell viability, proliferation, migration, and protein expression. This study aimed to compare the effects of two different wavelengths, at different fluencies, on human adult adipose derived stem cells (hADSCs). Materials and Methods: hADSCs were irradiated at 680 or 830 nm at fluencies of 5, 10 or 15 J/cm2. Cellular responses that were measured included cell morphology, viability and proliferation. Expression of stem cell markers were also determined by immunofluorescence (IF). Results: Indirect IF confirmed successful stem cell isolation and character with the expression of marker ALCAM (CD166). Morphologically, LILI did not induce any changes to the hADSCs as observed between control cells (0 J/cm2) and irradiated cells. hADSCs irradiated at 680 nm showed no statistical significant differences in viability and proliferation compared to non-irradiated cells at all fluencies, while irradiation at 830 nm showed a significant decrease in both viability and proliferation at 10 and 15 J/cm2 compared to both the non-irradiated and irradiated cells at 680 nm. Conclusion: Irradiation of hADSCs does not appear to induce differentiation. There is a wavelength as well as a fluence dependent effect, with cells irradiated in the visible range (680 nm) and low fluence (5 J/cm2) responding better than cells irradiated in the infra-red range (830 nm) and higher fluencies (10 and 15 J/cm2).