Low level laser therapy modulates viability, alkaline phosphatase and matrix metalloproteinase-2 activities of osteoblasts

- Low intensity laser is osteogenic inducer, but its role on MMPs is little explored.
- Infrared laser increases alkaline phosphatase activity.
- Red laser activates MMP-2.
- Very low energy doses of LLL modulate osteoblast proliferation and differentiation.

Low level laser therapy (LLLT) has been shown to stimulate bone cell metabolism but their impact on the matrix metalloproteinase (MMP) expression and activity is little explored. This study evaluated the influence of LLLT at two different wavelengths, red and infrared, on MC3T3-E1 preosteoblast viability, alkaline phosphatase (ALP) and MMP-2 and -9 activities. To accomplish this, MC3T3-E1 cells were irradiated with a punctual application of either red (660 nm; InGaAIP active medium) or infrared (780 nm; GaAlAs active medium) lasers both at a potency of 20 mW, energy dose of 0.08 or 0.16 J, and energy density of 1.9 J/cm2 or 3.8 J/cm2, respectively. The control group received no irradiation. Cellular viability, ALP and MMP-2 and -9 activities were assessed by MTT assay, enzymatic activity and zymography, respectively, at 24, 48 and 72 h. The treatment of cells with both red and infrared lasers significantly increased the cellular viability compared to the non-irradiated control group at 24 and 48 h. The ALP activity was also up modulated in infrared groups at 24 and 72 h, depending on the energy densities. In addition, the irradiation with red laser at the energy density of 1.9 J/cm2 promoted an enhancement of MMP-2 activity at 48 and 72 h. However, no differences were observed for the MMP-9 activity. In conclusion, when used at these specific parameters, LLL modulates both preosteoblast viability and differentiation highlighted by the increased ALP and MMP-2 activities induced by irradiation.