Influence of Neodymium-Doped Yttrium Aluminum Garnet Laser Irradiation on Cell Proliferation and Bone Morphogenetic Protein-2 Secretion in MG-63 Osteoblast-Like Cells

The aim of this in vitro study was to assess the influence of neodymium-doped yttrium aluminum garnet (Nd:YAG) laser irradiation on proliferation and bone morphogenetic protein-2 (BMP-2) secretion in MG-63 osteoblast-like cells. MG-63 cells were cultured in plastic 96-well plates and exposed to Nd:YAG laser irradiation (1064 nm). Independent variables included power (0.25 to 5.0 W) and irradiation time (10 to 60 s). In test and control groups, BMP-2 secretion was assessed using two methods: enzyme-linked immunosorbent assay (ELISA) and magnetic microsphere BMP-2 immunoassay. In addition, cell viability and proliferation were evaluated using water-soluble tetrazolium (WST-1) and cell counting kit-8 (CCK-8) assays. Outcome variables were assessed 24 and 72 h following laser exposure. Mann-Whitney U tests and Kruskal-Wallis tests were applied to assess differences in cell cultures across the independent variables of interest. Magnetic microsphere immunoassay analysis failed to identify any statistically significant influence of laser energy on BMP-2 secretion irrespective of power or irradiation time. In the ELISA analysis, BMP-2 concentration was significantly higher for irradiation time of 10 versus 60 seconds (p=0.009) at the 24-hour assessment only. CCK-8 analysis showed that, compared with control cultures, cell proliferation was significantly higher at the 24-hour recording for cells receiving power of 0.25 W (p=0.0048), 1 W (p=0.0048), 3 W (p=0.0048), or 5 W (p=0.0048). Similar effects on cell proliferation were noted at the 24- and 72-hour assessments. Under the conditions described, Nd:YAG laser irradiation consistently increased proliferation of MG-63 cells. However, in almost all experiments, BMP-2 secretion in control and laser-treated cell cultures were not statistically different. Differences in target cell types and laser irradiation parameters likely account for discordance between findings of the present investigation and those reported in prior studies.