Study of biological effects of laser irradiation on cell factions and differentiation.

使用CO_2激光的低强度激光治疗（LLLT）已知激活周围细胞和组织。然而，很少有关于使用硬激光LLLT的研究已经进行，很多关于LLLT的生物学机制仍然不确定。本文报道了未经手术治疗的CO_2激光照射大鼠胫骨后的形态学变化。本研究旨在从组织学角度观察CO_2激光照射对大鼠胫骨骨形成的影响。左侧胫骨接受CO_2激光照射，右侧胫骨不接受CO_2激光照射（对照组）。用CO_2激光从体外照射大鼠胫骨。在以下功率和暴露设置下进行辐照：功率，1.0 W ;持续时间：15 min ;计算的能量密度，100%。1千焦/立方厘米。照射后第7天取出钛片，进行软X线分析。制备连续切片进行类骨质染色（Yoshiki法）和ALP（碱性磷酸酶）染色，并检查矿化沉积率（钙黄绿素标记）。软X线检查显示对照组和CO_2激光照射组之间无差异。然而，在激光照射的胫骨表面上显著的类骨质形成（Yoshiki方法）和年轻的ALP阳性成骨细胞存在于类骨质组织中。有趣的是，钙黄绿素标记显示，激光照射后皮质骨骨膜上的矿物质沉积率明显高于对照组。结果表明，CO_2激光LLLT不仅能诱导成骨细胞分化，而且能诱导矿化。目前的研究表明，激光可以应用于骨再生治疗。

Low Level Laser Therapy (LLLT) using CO_2 lasers is known to activate surrounding cells and tissue. However, few studies concerning LLLT using hard lasers have been performed, and much about the biological mechanisms of LLLT remains uncertain. In the present study, we report the morphological changes in rat tibiae irradiated by a CO_2 laser without surgical treatment. The purpose of this study was to histologically evaluate the effects of LLLT using a CO_2 laser on bone formation in rat tibiae. The left tibia underwent CO_2 laser irradiation, while the right tibia did not undergo CO_2 laser irradiation (Control). Rat tibiae were irradiated by CO_2 laser from the outside of the body. Irradiation was performed at the following power and exposure settings : power, 1.0 W ; duration : 15 min ; calculated energy density, 〜1. 1 kJ/cm^3. On the 7th day after irradiation, tibiae were removed and were analyzed by Soft X-ray. Serial sections were prepared for osteoid staining (Yoshiki's method) and ALP (Alkaline phosphatase) staining, and were examined for mineralized apposition rate (Calcein labeling). Soft X-ray examination revealed no differences between the control and CO_2 laser-irradiated groups. However, marked osteoid formation (Yoshiki's method) on the surface of laser-irradiated tibiae and young ALP-positive osteoblasts were present in the osteoid tissue. Interestingly, calcein labeling demonstrated that mineral apposition rate on the periosteum of laser-irradiated cortical bone was much higher than that in control tibiae. These results demonstrate that LLLT using CO_2 laser induced not only mineralization but also osteoblast differentiation. The present study suggests that lasers can be applied to bone regeneration treatment.