Effect of low-power laser irradiation on bone formation

观察低功率激光照射对体外骨结节形成的影响。分离培养大鼠胎鼠颅骨成骨样细胞，用低功率激光照射10min/d。无论是每天照射还是脉冲激光照射，都会显著增加培养皿中形成的骨结节的数量。在传代培养后1~13d内进行脉冲照射，骨结节的形成明显增加。而在传代培养14d后，激光照射对骨结节的形成无影响。在传代培养的早期(13d内)进行放射治疗，可获得较大的平均骨结节大小。这很可能是激光照射在早期刺激了细胞的分化和增殖，这些细胞形成了更多和更大小的骨结节。因此，激光照射到未成熟的成骨细胞，而不是成熟的成骨细胞ma…激光照射可提高细胞外胶原水平和碱性磷酸酶(ALP)活性，增高率为20%~30%，提示激光照射对成骨细胞功能也有一定的刺激作用。用JEOL JED-2000能谱仪测定矿化结节中钙、磷的含量时，激光组钙磷净强度明显高于对照组(钙：1.3倍；磷：1.3倍)。然而，两组的Ca/P摩尔比的平均值相似。用RT-PCR方法研究了脉冲激光照射(10min)对骨结节中I型胶原和碱性磷酸酶基因表达的影响。激光照射后24 h，胶原和碱性磷酸酶基因表达均较对照组增加。这些数据表明，激光照射可能直接影响细胞，刺激大鼠颅骨细胞的分化和功能，导致大量和大小的骨结节形成。较少

Effects of low-power laser irradiation on bone nodule formation in vitro were assessed. Osteoblast-like cells isolated from rat calvariae of rat fetuses were cultured and were irradiated with a low-power laser for 10 min per day. Both every day and pulsed laser irradiation significantly increased the number of bone nodules formed in a dish. When pulsed irradiation was performed within 1 to 13 d after subculture, bone nodule formation significantly increased. However, irradiation had no effects on bone nodule formation when laser was irradiated after 14 d of subculture. Furthermore, irradiation was performed in the earlier period (within 13 d) after subculture to the cells resulting in larger average size of bone nodules. It is most likely that laser irradiation stimulated differentiation and proliferation of the cells in the earlier period and these cells formed a larger number and size of bone nodules. Therefore, laser irradiation to immature osteoblasts, but not mature osteoblasts ma … More y effective to stimulate bone nodule formation.The extra-cellular collagen level and alkaline phosphatase (ALP) activity were increased by laser irradiation and increased rates were 20 to 30% suggesting that osteoblasts function may be also stimulated by laser irradiation. When Ca and P contents in mineralized nodules were assessed by JEOL JED-2000 energy-dispersive X-ray microanalyzer, net intensities of Ca and P were significantly higher (Ca : 1.3 fold ; P : 1.3 fold) in laser group than in control group. However, the mean values of Ca/P mole ratio were similar in both groups. It may show that laser irradiation stimulated mineralization of bone nodules.Effects of pulsed laser irradiation (10min) on gene expression of type 1 collagen and ALP were investigated using RT-PCR method. Gene expression of both collagen and ALP increased 24 h after laser irradiation compared to those in the controls. These data suggest that laser irradiation may directly affect cells and stimulate differentiation and function of rat calvarial cells resulting a large number and size of bone nodule formation. Less