Effect of single and multiple doses of low-level laser therapy on viability and proliferation of stem cells from human exfoliated deciduous teeth (SHED)

• Published in: Lasers in medical science 2019-12, Vol.34 (9), p.1917-1924
• Main Authors: Almeida-Junior, Luciano Aparecido, Marques, Nádia Carolina Teixeira, Prado, Mariel Tavares de Oliveira, Oliveira, Thais Marchini, Sakai, Vivien Thiemy
• Format: Article
• Language: English
• Subjects: Cell Count; Cell growth; Cell proliferation; Cell Proliferation - radiation effects; Cell Survival - radiation effects; Cell viability; Dentistry; Dose-Response Relationship, Radiation; Energy; Humans; Irradiation; Lasers; Low-Level Light Therapy; Medicine; Medicine & Public Health; Optical Devices; Optics; Original Article; Photonics; Quantum Optics; Regeneration; Stem cells; Stem Cells - cytology; Stem Cells - radiation effects; Sulforhodamine; Tooth Exfoliation - radiotherapy; Tooth, Deciduous - radiation effects
• ISSN: 0268-8921; 1435-604X
• DOI: 10.1007/s10103-019-02836-y

The present study aimed to evaluate in vitro whether the low-level laser (LLL) delivering fractionated total energy (multiple irradiation) or single irradiation stimulates regeneration-associated events (viability and proliferation) in stem cells from human exfoliated deciduous teeth (SHED). Cells received LLL irradiation (InGaAlP–660 nm), according to the following experimental groups: G1 (single irradiation 2.5 J/cm 2 , 10 mW, 10 s, 0.10 J), G2 (single irradiation 5.0 J/cm 2 , 10 mW, 20 s, 0.20 J), G3 (single irradiation 7.5 J/cm 2 , 10 mW, 30 s, 0.30 J), G4 (two irradiations 2.5 J/cm 2 , 10 mW, 10 s; total energy 0.20 J), G5 (three irradiations 2.5 J/cm 2 , 10 mW, 10 s; total energy 0.30 J), and G6 (non-irradiated). Cell viability was assessed by MTT and trypan blue exclusion (TBE) methods, while cell proliferation was evaluated by crystal violet (CV) and sulforhodamine B (SRB) assays after 24, 48, and 72 h after the first irradiation. By MTT, there was no difference between groups at 24 and 72 h. At 48 h, the groups subjected to multiple irradiation (G4 and G5) presented higher cell viability rates. The average percentages of viable cells for all groups by TBE method were 91.04%, 96.63%, and 97.48% at 24, 48, and 72 h, respectively. By CV, there was no significant difference between groups at 24 and 48 h; at 72 h, G2, G3, and G4 presented higher cell proliferation. By SRB, G1 and G4 presented lower proliferation rates in all the periods. When the groups presenting the same total energy were compared, G2 (0.20 J) presented lower cell viability rates and higher cell proliferation rates in comparison with G4; G3 (0.30 J) presented similar results to those of G5, with higher cell viability and proliferation. The application of laser delivering fractionated total energy (two or three applications of 2.5 J/cm 2 ) induced higher cell viability at 48 h, while the single irradiation with 2.5 J/cm 2 did not stimulate metabolic activity in such period and the proliferation over time. The 5.0 and 7.5 J/cm 2 single doses and the three applications of 2.5 J/cm 2 maintained cell viability and stimulated proliferation of SHED at 72 h.