Low-level laser irradiation induces in vitro proliferation of stem cells from human exfoliated deciduous teeth.

Abstract

The aim of this study was to evaluate the effect of low-level laser irradiation (LLLI) on the proliferation and viability of stem cells from human exfoliated deciduous teeth (SHED). Cells were irradiated or not (control) with an InGaAlP laser diode (660nm, 30mW, continuous action mode) using two different energy densities (0.5J/cm2-16s; 1.0J/cm2-33s). Irradiation was performed at 0 and 48h, with the laser probe fixed at a distance of 0.5cm from the cells. Cell proliferation was analyzed at 0, 24, 48, and 72h by the Trypan blue exclusion method and MTT assay. Cell cycle and Ki67 expression were analyzed by flow cytometry. Apoptosis-related events were evaluated by expression of annexin V/PI and nuclear morphological changes by staining with DAPI. Differences between groups at each time were analyzed by the Kruskal-Wallis and Mann-Whitney tests, adopting a level of significance of 5% (p<0.05). The results showed that an energy density of 1.0J/cm2 promoted an increase in cell proliferation at 48 and 72h compared to the control and 0.5J/cm2 groups. Cell cycle analysis revealed a predominance of cells in the S and G2/M phases in the irradiated groups. This finding was confirmed by the increased expression of Ki67. Low positive staining for annexin V and PI was observed in all groups, and no nuclear changes were detected, indicating that cell viability was not affected by the energy densities tested. It can be concluded that the LLLI parameters used (660nm, 30mW, 1.0J/cm2) promote the proliferation of SHEDs and the maintenance of cell viability.