Kim In Sook, Cho Tae Hyung, Kim Kwansik, Weber Franz E, Hwang Soon Jung
Dental Research Institute, Seoul National University, 28 Yeongun-Dong, Chongro-Gu, Seoul, 110-749, Republic of Korea.
Lasers Surg Med. 2010 Aug;42(6):510-8. doi: 10.1002/lsm.20870.
High-power laser has recently become a physical stimulus for bone regeneration. Little is known about how high-power laser irradiation affects osteoblast differentiation. This study investigated osteoblast responses to high-power laser and combined irradiation with BMP-2 treatment.
STUDY DESIGN/MATERIALS AND METHODS: MC3T3-E1 pre-osteoblasts were exposed to laser irradiation, 100 ng/ml BMP-2 or both. Cells were irradiated with a Q-switched, pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) laser, with a 1,064 nm wavelength and 0.75 W output power under 1.5, 3, or 5 J/cm(2) energy densities. Cell proliferation was evaluated using tetrazolium salt, WST-8. To determine the effect of these treatments on in vitro osteogenesis, we examined alkaline phosphatase (ALP) activity, mineral deposition, and expression of genes associated with osteogenesis. Quantitative real time PCR or ELISA was used to examine cytokine expression. In each experiment, either non-irradiated or BMP-2 (100 ng/ml)-treated cells were used as controls.
High-power, low-level, Nd:YAG laser irradiation significantly increased ALP activity, when combined with BMP-2 or not. Cell proliferation declined in the irradiation and combined irradiation/BMP-2 groups. Interestingly, Nd:YAG laser stimulation resulted in significant induction of endogenous BMP-2 protein and gene expression. The increased expression of upstream regulators cbfa1 by Nd:YAG laser alone was comparable to exogenous BMP-2 treatment (100 ng/ml). Combined laser/BMP-2 treatment was synergistic in the expression of some genes (IGF-1, cbfa1) and ALP activity, compared to both BMP-2 treatment and laser irradiation alone. In vitro matrix mineralization was significantly accelerated by laser stimulation compared to that of the control, more so than with the combined laser/BMP-2 treatment.
The present in vitro findings demonstrate that high-power, low-level Nd:YAG laser increased osteoblast activity, very efficiently accelerating mineral deposition. Osteoinductive effect of laser is likely mediated by activation of BMP-2-related signaling pathway.
高功率激光最近已成为促进骨再生的一种物理刺激因素。关于高功率激光照射如何影响成骨细胞分化，目前所知甚少。本研究调查了成骨细胞对高功率激光以及联合骨形态发生蛋白-2（BMP-2）处理的反应。
研究设计/材料与方法：将MC3T3-E1前成骨细胞暴露于激光照射、100 ng/ml BMP-2或两者联合处理。细胞用调Q脉冲掺钕钇铝石榴石（Nd:YAG）激光照射，波长为1064 nm，输出功率为0.75 W，能量密度为1.5、3或5 J/cm²。使用四唑盐WST-8评估细胞增殖。为确定这些处理对体外成骨的影响，我们检测了碱性磷酸酶（ALP）活性、矿物质沉积以及与成骨相关基因的表达。采用定量实时PCR或酶联免疫吸附测定（ELISA）检测细胞因子表达。在每个实验中，未照射或BMP-2（100 ng/ml）处理的细胞用作对照。
无论是否与BMP-2联合，高功率、低强度Nd:YAG激光照射均显著增加ALP活性。照射组和联合照射/BMP-2组的细胞增殖均下降。有趣的是，Nd:YAG激光刺激导致内源性BMP-2蛋白和基因表达显著上调。单独Nd:YAG激光使上游调节因子cbfa1表达增加的程度与外源性BMP-2处理（100 ng/ml）相当。与单独的BMP-2处理和激光照射相比，联合激光/BMP-2处理在某些基因（胰岛素样生长因子-1、cbfa1）表达和ALP活性方面具有协同作用。与对照组相比，激光刺激显著加速了体外基质矿化，联合激光/BMP-2处理的加速作用不如激光刺激明显。
目前的体外研究结果表明，高功率、低强度Nd:YAG激光可增加成骨细胞活性，非常有效地加速矿物质沉积。激光的骨诱导作用可能是通过激活与BMP-2相关的信号通路介导的。
