| Summary: | 碩士 === 中原大學 === 醫學工程研究所 === 96 === Low-level laser irradiation is a physical treatment, which can lead to cell proliferation, increase of ATP synthesis, change in mitochondrial membrane potential and the induction of the synthesis of cell cycle regulatory proteins. The propose of the study was to explore the effects on proliferation and differentiation of mesenchymal stem cells (MSCs) derived from rat bone marrow using near-infrared (850 nm) light emitting diodes (LEDs) irradiation. Four different parameters of irradiation (irradiance: 10 or 15 mW/cm2; radiant exposure: 2 or 4 J/cm2), were used to stimulate MSCs once per day or every other day. To demonstrate the effect of biomodulation was due to photochemical effect, the temperatures of PBS and culture medium during irradiation were monitored. No apparent change in temperature (26.1 to 26.3 oC) was found. The result showed that the proliferation of MSCs was promoted at the irradiance of 10 mW/cm2 and radiant exposures of 2 and 4 J/cm2, particularly at 10 mW/cm2 and 4 J/cm2. The parameter was used in the following research. It was found that alkaline phosphatase activity and osteocalcin secretion were promoted during osteoblastogenesis while triacylglycerol accumulation was inhibited during adipogenesis in the MSCs treated with LLLI. The expression level of adipogenic transcription factor, PPARγ, was down-regulated. LLLI not only decreased the production of reactive oxygen species but also the activity of senescence associated β-galactosidase. Meanwhile, the level of intracellular ATP was found to increase after LLLI. No apparent cellular damage was seen after LLLI by LDH release assay. In addition, the expression level of heat shock protein hsp70 but not c-fos was enhanced. To sum up, near infrared LED irradiation with combined irradiance of 10 mW/cm2 and the light dosage of 4 J/cm2 could enhance cell proliferation and osteogenic capability of MSCs. Adipogenic capability of MSCs was reduced after LLLI. LLLI may have anti-aging affects by increasing intracellular ATP level and decreasing ROS production. An irradiation device for LLLI used in vivo will be under development in order to improve the efficacy of stem cell therapy in clinical treatments.
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