In Vitro Effect of Low-Level Laser Therapy on Undifferentiated Mouse Pulp Cells

AbstractLow-level laser therapy has been investigated as a possible stimulus for enhancement of proliferation and differentiation of various cell types, but few reports relate undifferentiated mouse pulp cells (OD-21) response to irradiation in in vitro models. The aim of this study was to analyze the influence of low-level laser therapy (λ=660 nm), with three different irradiation times, on the behavior of OD-21 cell line. The cells were cultivated and divided into three groups: non-irradiated/control (group I); irradiated with 88 s (group II); irradiated with 177 s (group III) and irradiated with 265 s (group IV). Cell growth and viability were assessed after 7 and 10 days. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests (α=.05). At day 7, there was a higher cell growth in groups I and II, as compared to group IV (p<.01). At the 10th day, group I showed a higher cell growth as compared to group II (p<.05). Cell viability in group IV was significantly lower at the 7th day, as compared to groups I (p<.001), II (p<.01) and III (p<.001). Cell viability in all the groups was over 80%, except in group IV at day 7. Irradiation time of group I influenced positively the proliferation and viability of OD-21 cells in late cell culture period. Keywords: Low-Level Laser Therapy. Cell Culture. Stem Cells. ResumoA terapia a laser de baixa intensidade tem sido investigada como possivel estimulo para aumento da proliferacao e diferenciacao de varios tipos de celulas, mas poucos relatos relacionam a resposta de celulas indiferenciadas da polpa dentaria de camundongos (OD-21) a irradiacao em modelos in vitro. O objetivo deste estudo foi analisar a influencia do laser de baixa intensidade (λ=660 nm), com tres periodos de irradiacao diferentes, no comportamento das celulas da linhagem OD-21. As celulas foram cultivadas e distribuidas em tres grupos: nao irradiado / controle (grupo I); irradiado com 88 s (grupo II); irradiado com 177 s (grupo III) e irradiado com 265 s (grupo IV). O crescimento e a viabilidade celular foram avaliados apos 7 e 10 dias. Os dados foram analisados pelos testes de Kruskal-Wallis e Mann-Whitney (α = 0,05). No dia 7, houve crescimento celular maior nos grupos I e II, em comparacao ao grupo IV (p <0,01). No decimo dia, o grupo I apresentou crescimento celular superior ao grupo II (p <0,05). A viabilidade celular no grupo IV foi significativamente menor no setimo dia, em comparacao aos grupos I (p <0,001), II (p <0,01) e III (p <0,001). A viabilidade celular em todos os grupos foi superior a 80%, exceto no grupo IV no dia 7. O tempo de irradiacao do grupo I influenciou positivamente a proliferacao e a viabilidade das celulas OD-21 no periodo mais tardio da cultura celular. Palavras-chave: Laserterapia de Baixa Intensidade. Cultura Celular. Celulas Tronco.