Mesenchymal Stem/Stromal Cells: FAR-INFRARED IRRADIATION EMITTED FROM CARBON FIBER SHEETS INCREASES OSTEOGENIC DIFFERENTIATION OF HUMAN TONSIL-DERIVED MESENCHYMAL STEM CELLS

Background & Aim: Far-infrared (FIR) is an electromagnetic radiation spectrum subdivided into 3–1000 μm, as defined by the International Commission on Illumination. FIR irradiation exerts various biological effects on cellular activities. Our previous study demonstrated that FIR induces osteogenesis of MSCs but inhibits adipogenesis, suggesting its potential therapeutic implication for treating osteoporosis, which is caused by an imbalance between osteogenic and adipogenic differentiation of MSCs in the bone marrow. Based on this finding, we attempted to devise a new tool that makes FIR irradiation more comfortable for clinical application. Methods, Results & Conclusion: Recently, we have designed the carbon fiber sheets (CFS) planar heating element device, which is coparatively flexible in adjusting its shape and has adequate FIR emissivity at a relatively lower temperature range. The cytotoxicity of the FIR emitted from the CFS (FIR-CFS) on tonsil-derived mesenchymal stem cells (TMSCs) was initially evaluated by assessing its effect on cell viability and proliferation using MTT, FITC-Annexin V apoptosis, and BrdU assays at 60 (CFS60), 70 (CFS70), or 80°C (CFS80) for 0.5, 1, and 2 h. The optimum conditions of the FIR-CFS were determined to be CFS60 and CFS70 for 1 h, and significantly induced the osteogenesis of the TMSCs. Their osteogenic potentials on TMSCs were also compared using Alizarin red S staining, and FIR-CFS70 for 1 h resulted in the highest induction of osteogenesis compared to other conditions. The western blotting analyses also confirmed that the TMSCs exposed to CFS70 for 1 h had the significantly increased level of osteo blast markers, osteocalcin (OCN) and alkaline phosphatase (ALP) with the decreased level of osteoclast markers, osteopontin (OPN) and type I collagen (COL1) compared to unirradiated control. In summary, our study demonstrates that the FIR-CFS increases the osteogenic potentials of TMSCs in vitro, indicating that this device could alleviate the progress of osteoporosis by increasing bone formation in the bone marrow. Further studies are required to identify the osteogenic mechanisms of FIR and to validate its osteogenic potential in vivo.