LOW-ENERGY DIODE-LASER IRRADIATION REDUCED PLASMINOGEN-ACTIVATOR ACTIVITY IN HUMAN PERIODONTAL-LIGAMENT CELLS

Background and Objective: The plasminogen activator (PA)-plasmin prote olytic system is implicated in the degradation of the extracellular ma trix in inflammation. Since human periodontal ligament (PDL) cells pro duced high PA activity in response to mechanical stress, excessive mec hanical stress to PDL cells such as occlusal trauma may induce collage n breakdown through activation of the PA-plasmin system. As low-energy laser irradiation has anti-inflammatory effects, we examined the effe cts of low-energy laser irradiation on the PA-plasmin system in stretc hed PDL cells in vitro. Study Design/Materials and Methods: Human PDL cells obtained from healthy premolars were mechanically stretched and Ga-Al-As low-energy laser was irradiated (830nm, 3.95 to 7.90 J/cm(2)) to the stretched cells. Results: PDL cells showed a marked elevation in PA activity in response to stretching, which was significantly inhi bited by a laser irradiation in a dose-dependent manner (55-86%, p < 0 .001). This effect could involve transcriptional events of tissue type (t) PA gene. Conclusion: These results suggests that laser irradiatio n may reduce collagen breakdown around the PDL associated with traumat ic occlusion. (C) 1997 Wiley-Liss, Inc.