| Summary: | 碩士 === 中原大學 === 生物醫學工程研究所 === 99 === Low level light irradiation (LLLI) was shown to enhance the proliferation and osteogenic capability of rat bone marrow mesenchymal stem cells (rbMSCs) previously. The purposes of the study were to understand whether LLLI can promote rbMSCs migration using the optimal parameters for cell proliferation and to elucidate the mechanism of rbMSCs migration induced by LLLI. Red (630 nm, 15 mW/ cm2) and near infrared (NIR, 850 nm, 10 mW/ cm2) light emitting diodes (LEDs) were used as light sources. Cells were irradiated at radiant exposure of 4 J/ cm2 of red and NIR light, respectively. The result of cell proliferation assay showed that the number of rbMSCs with NIR illumination increased 27 %, whereas the number of cells with red light irradiation increased 5.6%, compared to non-irradiated control group at the fourth day post-irradiation. The result of CFU-F assay showed that the number of large-size colonies (> 0.5 cm) increased after red and NIR light exposure. The results of transwell migration and wound healing assays showed that both red and NIR light irradiation could enhance cell migration, especially for near infrared. The addition of NF-κB inhibitor decreased the transmembrane migration enhanced by red and NIR light irradiation. We further observed the short term effect after LLLI and found that intracellular cytochrome c oxidase activity, mitochondrial membrane potential, ATP level and reactive oxygen species (ROS) production were enhanced immediately after illumination. Gene expression study demonstrated that red and NIR light irradiation increased HSP 70 expression, and reduced TIMP-1 and TIMP-2 expression. Protein expression study demonstrated that pFAK expression was elevated, and the secretion of MMP-2 and MMP-9 was facilitated after LLLI. The study demonstrated that red and NIR LLLI could enhance mitochondrial photoacceptor-cytochrome c oxidase activity, mitochondrial membrane potential, intracellular ATP level synthesis and ROS level in rbMSCs, thereby activating NF-κB. The increase of ATP synthesis led to HSP 70 activation and thus cell proliferation was enhanced through NF-κB signal pathway. The increase of ATP synthesis also resulted in enhanceing cell migration via phosphorylation of FAK protein, reducing TIMPs expression and activating MMPs activities.
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