Solmaz Hakan, Ulgen Yekta, Gulsoy Murat
Bogazici University, Institute of Biomedical Engineering, Kandilli Kampusu, Uskudar, 34684, Istanbul, Turkey.
Lasers Med Sci. 2017 May;32(4):903-910. doi: 10.1007/s10103-017-2191-0. Epub 2017 Mar 20.
Fibroblast cells are known to be one of the key elements in wound healing process, which has been under the scope of research for decades. However, the exact mechanism of photobiomodulation on wound healing is not fully understood yet. Photobiomodulation of 635 and 809 nm laser irradiation at two different energy densities were investigated with two independent experiments; first, in vitro cell proliferation and then in vivo wound healing. L929 mouse fibroblast cell suspensions were exposed with 635 and 809 nm laser irradiations of 1 and 3 J/cm energy densities at 50 mW output power separately for the investigation of photobiomodulation in vitro. Viabilities of cells were examined by means of MTT assays performed at the 24th, 48th, and 72nd hours following the laser irradiations. Following the in vitro experiments, 1 cm long cutaneous incisional skin wounds on Wistar albino rats (n = 24) were exposed with the same laser sources and doses in vivo. Wound samples were examined on 3rd, 5th, and 7th days of healing by means of mechanical tensile strength tests and histological examinations. MTT assay results showed that 635 nm laser irradiation of both energy densities after 24 h were found to be proliferative. One joule per square centimeter laser irradiation results also had positive effect on cell proliferation after 72 h. However, 809 nm laser irradiation at both energy densities had neither positive nor negative affects on cell viability. In vivo experiment results showed that, 635 nm laser irradiation of both energy densities stimulated wound healing in terms of tensile strength, whereas 809 nm laser stimulation did not cause any stimulative effect. The results of mechanical tests were compatible with the histological evaluations. In this study, it is observed that 635 nm laser irradiations of low energy densities had stimulative effects in terms of cell proliferation in vitro and mechanical strength of incisions in vivo. However, 809 nm laser irradiations at the same doses did not have any positive effect.
成纤维细胞是伤口愈合过程中的关键要素之一，数十年来一直处于研究范围之内。然而，光生物调节对伤口愈合的确切机制尚未完全了解。通过两项独立实验研究了635和809纳米激光在两种不同能量密度下的光生物调节作用；首先是体外细胞增殖，然后是体内伤口愈合。将L929小鼠成纤维细胞悬液分别以50毫瓦输出功率、1和3焦耳/平方厘米的能量密度用635和809纳米激光照射，以研究体外光生物调节作用。在激光照射后的第24、48和72小时通过MTT法检测细胞活力。体外实验后，对24只Wistar白化大鼠进行1厘米长的皮肤切开伤口，在体内用相同的激光源和剂量照射。在愈合的第3、5和7天，通过机械拉伸强度测试和组织学检查对伤口样本进行检查。MTT分析结果表明，24小时后两种能量密度的635纳米激光照射均具有增殖作用。每平方厘米1焦耳的激光照射结果在72小时后对细胞增殖也有积极影响。然而，两种能量密度的809纳米激光照射对细胞活力既无积极影响也无消极影响。体内实验结果表明，两种能量密度的635纳米激光照射在拉伸强度方面刺激了伤口愈合，而809纳米激光刺激未产生任何刺激作用。机械测试结果与组织学评估结果一致。在本研究中，观察到低能量密度的635纳米激光照射在体外细胞增殖和体内切口机械强度方面具有刺激作用。然而，相同剂量的809纳米激光照射没有任何积极作用。
