High power-pulsed Nd:YAG laser as a new stimulus to induce BMP-2 expression in MC3T3-E1 osteoblasts.
OBJECTIVE
High-power laser has recently become a physical stimulus for bone regeneration. Little is known about how high-power laser irradiation affects osteoblast differentiation. This study investigated osteoblast responses to high-power laser and combined irradiation with BMP-2 treatment.


METHODS
MC3T3-E1 pre-osteoblasts were exposed to laser irradiation, 100 ng/ml BMP-2 or both. Cells were irradiated with a Q-switched, pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) laser, with a 1,064 nm wavelength and 0.75 W output power under 1.5, 3, or 5 J/cm(2) energy densities. Cell proliferation was evaluated using tetrazolium salt, WST-8. To determine the effect of these treatments on in vitro osteogenesis, we examined alkaline phosphatase (ALP) activity, mineral deposition, and expression of genes associated with osteogenesis. Quantitative real time PCR or ELISA was used to examine cytokine expression. In each experiment, either non-irradiated or BMP-2 (100 ng/ml)-treated cells were used as controls.


RESULTS
High-power, low-level, Nd:YAG laser irradiation significantly increased ALP activity, when combined with BMP-2 or not. Cell proliferation declined in the irradiation and combined irradiation/BMP-2 groups. Interestingly, Nd:YAG laser stimulation resulted in significant induction of endogenous BMP-2 protein and gene expression. The increased expression of upstream regulators cbfa1 by Nd:YAG laser alone was comparable to exogenous BMP-2 treatment (100 ng/ml). Combined laser/BMP-2 treatment was synergistic in the expression of some genes (IGF-1, cbfa1) and ALP activity, compared to both BMP-2 treatment and laser irradiation alone. In vitro matrix mineralization was significantly accelerated by laser stimulation compared to that of the control, more so than with the combined laser/BMP-2 treatment.


CONCLUSIONS
The present in vitro findings demonstrate that high-power, low-level Nd:YAG laser increased osteoblast activity, very efficiently accelerating mineral deposition. Osteoinductive effect of laser is likely mediated by activation of BMP-2-related signaling pathway.
Kim
In Sook
IS
Dental Research Institute, Seoul National University, 28 Yeongun-Dong, Chongro-Gu, Seoul, 110-749, Republic of Korea.
Cho
Tae Hyung
TH
Kim
Kwansik
K
Weber
Franz E
FE
Hwang
Soon Jung
SJ
D000469:Alkaline Phosphatase / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism* / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D007334:Insulin-Like Growth Factor I / Q000235:genetics; D053844:Lasers, Solid-State; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects*; D010012:Osteogenesis / Q000187:drug effects / Q000528:radiation effects; D016133:Polymerase Chain Reaction
C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D050659:Core Binding Factor Alpha 1 Subunit; D007334:Insulin-Like Growth Factor I; D000469:Alkaline Phosphatase