Low pulse energy Nd:YAG laser irradiation exerts a biostimulative effect on different cells of the oral microenvironment: "An in vitro study"

• Published in: Lasers in surgery and medicine 2010-08, Vol.42 (6), p.527-539
• Main Authors: Chellini, Flaminia, Sassoli, Chiara, Nosi, Daniele, Deledda, Cristiana, Tonelli, Paolo, Zecchi-Orlandini, Sandra, Formigli, Lucia, Giannelli, Marco
• Format: Article
• Language: English
• Subjects: alkaline phosphatase (ALP); Alkaline Phosphatase - metabolism; Animals; Calcium (intracellular); Calcium - metabolism; Calcium influx; calcium transients; Cbfa-1 protein; Cell proliferation; Cell Proliferation - radiation effects; Cell Survival - radiation effects; Cells, Cultured; Collagen Type I - metabolism; Core Binding Factor Alpha 1 Subunit - metabolism; Endothelial cells; Endothelial Cells - metabolism; Endothelial Cells - radiation effects; Energy; Enzyme Inhibitors - pharmacology; Fibroblasts; Fibroblasts - metabolism; Fibroblasts - radiation effects; Fluorescent Antibody Technique; Humans; Immunofluorescence; Ion channels; Lasers; Lasers, Solid-State; Low-Level Light Therapy; Methylene Blue - pharmacology; Mice; Microenvironments; Mouth Mucosa - cytology; Osteoblastogenesis; Osteoblasts; Osteoblasts - metabolism; Osteoblasts - radiation effects; Osteopontin; Osteopontin - metabolism; peri-implantitis; periodontitis; Photosensitization; Polymerase Chain Reaction; Repetition; Runt-related transcription factor 2 (Runx2); Therapeutic applications; transient receptor potential canonical channel 1 (TRPC1); TRPC Cation Channels - physiology; vinculin; Vinculin - metabolism
• ISSN: 0196-8092; 1096-9101; 1096-9101
• DOI: 10.1002/lsm.20861

Background and Objectives Dental lasers represent a promising therapeutic tool in the treatment of periodontal and peri‐implant diseases. However, their clinical application remains still limited. Here, we investigated the potential biostimulatory effect of low pulse energy neodymium:yttrium–aluminum–garnet (Nd:YAG) laser irradiation on different cells representative of the oral microenvironment and elucidated the underlying molecular mechanisms. Materials and Methods Saos‐2 osteoblasts, H‐end endothelial cells, and NIH/3T3 fibroblasts pre‐treated or not with photosensitizing dye methylene blue (MB), were irradiated with low pulse energy (20 mJ) and high repetition rate (50–70 Hz) Nd:YAG laser, and evaluated for cell viability and proliferation as well as for the expression of specific differentiation markers by confocal immunofluorescence and real‐time RT‐PCR. Changes in intracellular Ca2+ levels after laser exposure were also evaluated in living osteoblasts. Results Nd:YAG laser irradiation did not affect cell viability in all the tested cell types, even when combined with pre‐treatment with MB, and efficiently stimulated cell growth in the non‐sensitized osteoblasts. Moreover, a significant induction in the expression of osteopontin, ALP, and Runx2 in osteoblasts, type I collagen in fibroblasts, and vinculin in endothelial cells could be observed in the irradiated cells. Pre‐treatment with MB negatively affected cell differentiation in the unstimulated and laser‐stimulated cells. Notably, laser irradiation also caused an increase in the intracellular Ca2+ in osteoblasts through the activation of TRPC1 ion channels. Moreover, the pharmacologic or genetic inhibition of these channels strongly attenuated laser‐induced osteopontin expression, suggesting a role for the laser‐mediated Ca2+ influx in regulating osteoblast differentiation. Conclusion Low pulse energy and high repetition rate Nd:YAG laser irradiation may exert a biostimulative effect on different cells representative of the oral microenvironment, particularly osteoblasts. Pre‐treatment with MB prior to irradiation hampers this effect and limits the potential clinical application of photosensitizing dyes in dental practice. Lasers Surg. Med. 42:527–539, 2010. © 2010 Wiley–Liss, Inc.