Increase of bone volume by a nanosecond pulsed laser irradiation is caused by a decreased osteoclast number and an activated osteoblasts.

The biostimulatory effects of laser irradiation focus not only in the field of soft tissue but also bone formation. Studies have shown that the light of a nanosecond pulsed laser which has a high peak power can produce stress waves in tissue. We have hypothesized that nanosecond pulsed laser irradiation stimulates bone formation. Our aim was to clarify the mechanism of increased bone volume by nanosecond pulsed laser irradiation. Rat femur was irradiated with a Q-switched Nd:YAG laser, which has a wavelength of 1064 nm. The quantification of trabecular architecture using three-dimensional morphometric analysis and measurement of bone mineral density (BMD) using pQCT was performed on day 1, day 3, day 5, and day 7 after laser irradiation. The laser effects on bone cells were also investigated using histological and immunohistochemical analysis. On day 1 after laser irradiation, bone volume (BV/TV), trabecular thickness (Tb.Th), and other parameters of the irradiated group did not significantly differ from the non-irradiation group (control). However, the mean BV/TV, Tb.Th, mineral apposition rate, and BMD of the laser group on day 7 after laser irradiation were significantly greater than those of the control. On histological analysis, the number of TRAP-positive osteoclasts was lower on day 3 after laser irradiation. Osteoblasts with activated clearance were seen in the laser irradiated group on day 1 and day 3. These data reveal that the increased bone volume by nanosecond pulsed laser irradiation causes an increase in osteoblast activity and a decrease in osteoclast number.

[1]  C. Turner,et al.  Mechanotransduction in the cortical bone is most efficient at loading frequencies of 5-10 Hz. , 2004, Bone.

[2]  S. F. Cleary,et al.  Laser Pulses and the Generation of Acoustic Transients in Biological Material , 1977 .

[3]  S. Goldstein,et al.  Effect of compressive loading on chondrocyte differentiation in agarose cultures of chick limb‐bud cells , 2000, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[4]  Y Abiko,et al.  Low-energy laser irradiation stimulates bone nodule formation at early stages of cell culture in rat calvarial cells. , 1998, Bone.

[5]  M. Drezner,et al.  Bone histomorphometry: Standardization of nomenclature, symbols, and units: Report of the asbmr histomorphometry nomenclature committee , 1987, Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research.

[6]  M A Trelles,et al.  Bone fracture consolidates faster with low‐power laser , 1987, Lasers in surgery and medicine.

[7]  R. Recker,et al.  Static and tetracycline‐based bone histomorphometric data from 34 normal postmenopausal females , 1988, Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research.

[8]  J Y Rho,et al.  Mechanical loading thresholds for lamellar and woven bone formation , 1994, Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research.

[9]  M. Obara,et al.  Nanosecond, high‐intensity pulsed laser ablation of myocardium tissue at the ultraviolet, visible, and near‐infrared wavelengths: In‐vitro study , 2001, Lasers in surgery and medicine.

[10]  C M Cobb,et al.  Biostimulation of wound healing by low-energy laser irradiation. A review. , 1996, Journal of clinical periodontology.

[11]  S. Cowin,et al.  Strain Amplification in the Bone Mechanosensory System , 1998 .

[12]  M. Wolbarsht.  Laser Applications in Medicine and Biology , 1989, Springer US.

[13]  R Lubart,et al.  A possible explanation of laser-induced stimulation and damage of cell cultures. , 1991, Journal of photochemistry and photobiology. B, Biology.

[14]  N. Shimizu,et al.  Effects of low‐energy laser irradiation on bone remodeling during experimental tooth movement in rats , 2000, Lasers in surgery and medicine.

[15]  U. Oron,et al.  Low-level laser irradiation promotes proliferation and differentiation of human osteoblasts in vitro. , 2005, Photomedicine and laser surgery.

[16]  A. Aoki,et al.  Effect of low-level Er:YAG laser irradiation on cultured human gingival fibroblasts. , 2005, Journal of periodontology.

[17]  S. Dekel,et al.  Effect of low‐power laser irradiation on the mechanical properties of bone fracture healing in rats , 1998, Lasers in surgery and medicine.

[18]  I. Owan,et al.  Recruitment and proliferative responses of osteoblasts after mechanical loading in vivo determined using sustained-release bromodeoxyuridine. , 1998, Bone.

[19]  U. Oron,et al.  Effect of low-energy laser (He-Ne) irradiation on the process of bone repair in the rat tibia. , 1995, Bone.

[20]  Hana Kolarova,et al.  Penetration of the laser light into the skin in vitro , 1999 .

[21]  C. Turner,et al.  Effects of Loading Frequency on Mechanically Induced Bone Formation , 2001, Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research.

[22]  Tadashi Ninomiya,et al.  High-intensity pulsed laser irradiation accelerates bone formation in metaphyseal trabecular bone in rat femur , 2003, Journal of Bone and Mineral Metabolism.

[23]  T. Nakamura,et al.  Effect of mechanical unloading and reloading on periosteal bone formation and gene expression in tail-suspended rapidly growing rats. , 1998, Bone.

[24]  Noriyoshi Shimizu,et al.  Effects of pulse frequency of low-level laser therapy (LLLT) on bone nodule formation in rat calvarial cells. , 2003, Journal of clinical laser medicine & surgery.

[25]  H. Anderson,et al.  PHOSPHATASES OF EPIPHYSEAL CARTILAGE STUDIED BY ELECTRON MICROSCOPIC CYTOCHEMICAL METHODS , 1971, The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society.

[26]  L.,et al.  Tartrate-resistant acid phosphatase in bone and cartilage following decalcification and cold-embedding in plastic. , 1987, The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society.

[27]  Raymond J. Lanzafame,et al.  Photomodulation of Oxidative Metabolism and Electron Chain Enzymes in Rat Liver Mitochondria , 1997, Photochemistry and photobiology.

[28]  F. L'Esperance.  Laser Applications in Medicine and Biology, vol 1. , 1972 .

[29]  Q Q Wu,et al.  Mechanoregulation of chondrocyte proliferation, maturation, and hypertrophy: ion-channel dependent transduction of matrix deformation signals. , 2000, Experimental cell research.

[30]  A. Hosoya,et al.  Effects of fixation and decalcification on the immunohistochemical localization of bone matrix proteins in fresh-frozen bone sections , 2005, Histochemistry and Cell Biology.

[31]  Xin Wang,et al.  Accelerated Chondrogenesis of the Rabbit Cranial Base Growth Plate by Oscillatory Mechanical Stimuli , 2002, Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research.

[32]  A. Robling,et al.  Mechanisms by which exercise improves bone strength , 2009, Journal of Bone and Mineral Metabolism.

[33]  V. O. Wagner,et al.  Evaluation of potential genotoxicity of pulsed electric and electromagnetic fields used for bone growth stimulation. , 1997, Mutation research.

[34]  H. Anderson,et al.  Matrix vesicle biogenesis in vitro by rachitic and normal rat chondrocytes. , 1990, The American journal of pathology.

[35]  Localization of alkaline phosphatase and osteopontin during matrix mineralization in the developing cartilage of coccygeal vertebrae. , 2000, Archives of histology and cytology.

[36]  T Nishisaka,et al.  Comparison of phototoxicity mechanism between pulsed and continuous wave irradiation in photodynamic therapy. , 1999, Journal of photochemistry and photobiology. B, Biology.

[37]  T. Tagawa,et al.  Effect of low-level laser irradiation on osteoglycin gene expression in osteoblasts , 2003, Lasers in Medical Science.

[38]  T J Chambers,et al.  Characterization of osteogenic response to mechanical stimulation in cancellous bone of rat caudal vertebrae. , 1993, The American journal of physiology.

[39]  E. Chao,et al.  Low intensity ultrasound treatment increases strength in a rat femoral fracture model , 1994, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[40]  K. Mustafa,et al.  Effect of laser therapy on attachment, proliferation and differentiation of human osteoblast-like cells cultured on titanium implant material. , 2005, Biomaterials.

[41]  T. Karu,et al.  Photobiology of low-power laser effects. , 1989, Health physics.

[42]  Makoto Kikuchi,et al.  Effect of low‐intensity argon laser irradiation on mitochondrial respiration , 1994, Lasers in surgery and medicine.