Efeito da irradiação com LED vermelho (630nm) sobre ciclo celular, potencial elétrico mitocondrial e senescência de células-tronco da polpa de dentes

Abstract

Studies have evaluated the best way to preserve the self-renewal and viability of stem cells. Phototherapy has demonstrated the capacity to modulate the proliferation of stem cells collected from different sites of the human body. However, there are few reports on the effects of light-emitting diode (LED) irradiation on deciduous teeth stem cell (SHED). The aim of the present study was to investigate the effect of red LED (630nm, 37mW/cm2 and 75mW) at different energy densities on the cell cycle, mitochondrial electrical potential and senescence of DTST. Previously characterized SHED cultures were expanded (through to the sixth passage) and irradiated with LED at energy densities of 2J/cm2, 4J/cm2, 8J/cm2, 16J/cm2 and 32J/cm2. Non-irradiated cultures served as control. After 24h of incubation, assays were conducted using flow cytometry to evaluate the cell cycle (using propidium iodide) and mitochondrial electrical potential (using rhodamine-123) of the cultures in each group. For the purposes of data analysis, the two energy densities that induced the best proliferative response were chosen for the analysis cell senescence (based on the enzyme expression of ß-galactosidase). Cultures irradiated with 2 J/cm2 and 16 J/cm2 had the higher percentages of cells in the synthesis phase in comparison to control cultures, but the difference was only significant in cells irradiated with 16 J/cm2 (p<0.05). No significant differences were found between irradiated and control cells regarding other cell cycle phases. Moreover, no significant differences were found regarding the percentage of cells with viable mitochondria (evaluated based on mitochondrial electrical potential) between irradiated and control cultures. With regard to cell senescence, no significant differences were found between control cultures and cultures irradiated with 2 J/cm2 or 16 J/cm2. LED irradiation at 630nm with irradiance of 37 mW/cm2, output power of 75 mW and energy density of 16J/cm2 was capable of inducing a proliferative response in deciduous tooth stem cells without affecting mitochondrial function or inducing senescence.