Gene Expression of Leukoplakia Cells After Influence of Electric Field

Objectives: Different metallic dental materials can induce oral galvanism, and therefore, in this study gene expression of oral leukoplakia cells grown inside electric field in vitro is analysed.
Methods: Culture dishes with subconfluent MSK-LEUK1 cells were placed in an approved pseudo-realistic device generating electric fields without polarisation. Electrodes immersed into the cell culture medium were connected to a direct current supply that generated voltage pulses with durations of 0.9 s each. Electric fields caused by this assembly amounted to 1-16 V/m, similar to oral conditions. After exposure to different field strengths, RNA was isolated and reversely transcribed to cDNA. Gene expression was analysed using PCR arrays, single genes (THBS1, MTSS1) were validated by real-time PCR. Student’s t-test was used to assess differences in gene expression.
Results: 35 genes were significantly dysregulated, 9 (out of 13) of these belonging to the adhesion signalling pathway, of which 5 are part of the integrin family. MTSS1 (Metastasis suppressor 1) was significantly downregulated (16 V/m: -9.58; p=.008). Adhesion plays a crucial role in cell movement, signalling and metastasis. THBS1 (Thrombospondin 1) was highly downregulated with rising field strength and showed more than ten times reduced expression in experiments with 16 V/m (2 V/m: -2.95, p=.042; 10 V/m: -3.04, p=.169; 16 V/m: -13.68, p=.018). THBS1 is found among others in odontoblasts and is potentially playing a role in biomineralisation and dentinogenesis.
Conclusions: Exposure to electric field strength up to 16 V/m (possibly due to formation of reactive oxygen species) influences the gene expression of oral leukoplakia cells in vitro. It was shown that many genes of the adhesion signalling pathway are downregulated which could be important for malignant transformation of cells.