Department of Biosystems & Biomaterials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea.
Electrical and Biological Physics, Kwangwoon University, Seoul, 01897, Republic of Korea.
Sci Rep. 2018 Feb 1;8(1):2057. doi: 10.1038/s41598-018-19395-x.
Low power light (LPL) treatment has been widely used in various clinical trials, which has been known to reduce pain and inflammation and to promote wound healing. LPL was also shown to enhance differentiation of stem cells into specific lineages. However, most studies have used high power light in mW order, and there was lack of studies about the effects of very low power light in μW. In this study, we applied 810 nm LPL of 128 μW/cm energy density in vitro. Upon this value, continuous wave (CW) irradiation did not induce any significant changes for differentiation of human dental pulp stem cells (hDPSCs). However, the membrane hyperpolarization, alkaline phosphatase activity, and intracellular oxidative stress were largely enhanced in the pulsed wave (PW) with 30% of duty cycle and 300-3000 Hz frequencies-LPL in which LED driver work in the form of square wave. After 21 days of daily LPL treatment, Western blot revealed the dentinogenesis in this condition in vitro. This study demonstrates that the very low power light at 810 nm enhanced significant differentiation of hDPSCs in the PW mode and there were duty cycle dependency as well as pulsing frequency dependency in the efficiency.
低强度光（LPL）治疗已广泛应用于各种临床试验中，其已被证实可减轻疼痛和炎症，并促进伤口愈合。LPL 还被证明可以促进干细胞向特定谱系分化。然而，大多数研究都使用了毫瓦量级的高功率光，而关于微瓦量级的非常低功率光的研究则很少。在本研究中，我们在体外应用了 810nm 的 LPL，其能量密度为 128μW/cm。在这个值下，连续波（CW）辐照不会引起人牙髓干细胞（hDPSCs）分化的任何显著变化。然而，当使用占空比为 30%、频率为 300-3000Hz 的脉冲波（PW）时，细胞膜超极化、碱性磷酸酶活性和细胞内氧化应激会大大增强，其中 LED 驱动器以方波形式工作。在每天接受 LPL 治疗 21 天后，Western blot 显示在这种条件下体外有牙本质生成。本研究表明，810nm 的极低功率光在 PW 模式下显著增强了 hDPSCs 的分化，并且在效率上存在占空比依赖性和脉冲频率依赖性。
