Fotoativação mobiliza pericitos e células de origem neural no reparo da polpa dentária

Abstract

Introduction: Laser light has proven to be capable of photoactivate endogenous stem cells inducing their differentiation into multiple tissues, in addition to modulating inflammatoryand immune processes in injured microenvironments. This therapy is now called photobiomodulation therapy (PBM). Glial cells and pericytes – the perivascular cells – have been identified as the true stem cells of our body. However, the effects of PBM on these cells have never been explored using elegant (state-of-art) tracking techniques, which could providerelevant information about the laser's interactions with these labeled cellular components. Objectives: The goal of this study is to verify the stimulating capacity of PBM in the mobilization of pericytes and other endogenous cells in the repair of the dental pulp upon tissueinjury in vivo using a murine model (NG2-DsRed/Nestin-GFP) with transgenes for pericytes (NG2) and undifferentiated cells (Nestin). Methods: The dental pulps of the animals' first upper molars (n = 12) were exposed using drill 3195 and K#20 file. The PBM group (n = 6) was treated for 3 consecutive days with a diode laser (InGalP; 660nm; 20mW; 5J/cm2 ; 0.71 W/cm2 ;7s; continuous and in contact) and the other group was maintained as control (n = 6) without any treatment. On the 4 th day, the animals were euthanized and the effects of the application ofPBM on the mobilization of pericytes and on the dental pulp repair were verified by confocal microscopy and histological analysis (H&E and toluidine blue), respectively. Healthy dental pulps were used as a normality parameter (n = 6). The data were analyzed by the ANOVA testfollowed by the Tukey's poshoc (α = 0.05). Results: PBM showed an intense proliferation of terminal capillaries in the photoactivated teeth (p<0.05), while signs of pup vitality were observed in the coronal thirds adjacent to the injury site. In addition, the therapy promoted significant mobilization of pericytes and undifferentiated cells in the coronary pulp horns contiguous to the injury concerning the control group (p<0.05). Mast cells could not be identified in the dental pulp of any of the studied groups but could be seen mostly degranulated in the smooth tissues adjacent to the mesial root of the teeth of the photoactivated group (p<0.05). Conclusion: PBM stimulates the pulp tissue microvasculature neoformation and contributes to the influx of potent cells into the injured site. PBM may be a promise adjunct tool in regenerative endodontic procedures of the pulp tissue