Effects of laser irradiation on pulp cells under nutritional deficit

It has been demonstrated that cells under stress may be biostimulated by low level laser (LLL) irradiation. However, the ideal condition of stress to assess the effects of LLL therapy on cultured cells has not yet been established. Objectives: The aim of the present in vitro study was to evaluate the effects of a defined parameter of LLL irradiation on the metabolism (MTT assay), alkaline phosphatase (ALP) expression and total protein content of odontoblast-like cells (MDPC-23) under distinct nutritional stress conditions. Methods: A special irradiation device was developed (LASERTable) for this study. The cells were seeded (20,000 cells/cm² in wells of 24-well plates using complete culture medium (DMEM), and incubated for 24 hours at 37ºC, with 5% CO₂. After this period, the complete DMEM was replaced by a new culture medium with different concentrations of fetal bovine serum (FBS) giving rise to the following groups: Group 1: 2% FBS; Group 2: 5% FBS; and Group 3: 10% FBS. The cells were irradiated three times with LLL in specific parameters (808±3 nm, 100 mW, 3 J/cm²) every 24 hours. In Group 4 (control) the cells were not irradiated. Results: The groups in which the pulp cells were submitted to LLL irradiation showed enhanced cell metabolism, regardless of the serum concentration present in the culture medium. The highest cell metabolism and total protein content was observed in the Group 2 (Mann-Whitney; p≤0.05). The ALP expression decreased only in Group 1. Conclusion: According to the experimental conditions, it was concluded that the cell nutritional stress caused by reducing the concentration of FBS to 5% is the most suitable method to evaluate the biostimulation of MDPC-23 cells submitted to LLL irradiation.

Supported by: FAPESP - grant # 2007/50646-3 and CNPq - grant # 301029/2007-5