## 3 Results
### The miRNA Expression Level in the NHDF Cells after Treatment with Fluoride Ions and an SMF  
Analysis of our results showed that the miRNAs that regulate the expression of the _NFE2L2_ gene, i.e., miR-28-3p, miR-29b-1-5p and miR-365a-3p, were overexpressed in the NHDF cells that had been treated with fluoride compared to the control ([PERSON] post hoc test, \(p\) = 0.003, \(p\) = 0.010 and \(p\) = 0.005, respectively), while the action of an SMF caused their silencing compared to the F-treated cells (miR-28-3p: [PERSON] post hoc test, \(p\) = 0.086 for F + SMF vs. F and \(p\) = 0.076 for SMF vs. F; miR-365a-3p: [PERSON] post hoc test, \(p\) = 0.070 for F + SMF vs. F; a trend toward statistical significance) (Figure 2A-C, Table 3). There was also a negative correlation between the _NFE2L2_ gene expression and the selected miRNAs (miR-28-3p: r = \(-\)0.30, \(p\) = 0.050 and miR-29b-1-5p: r = \(-\)0.25, \(p\) = 0.062), which confirms their roles in regulating the _NFE2L2_ gene expression (Figure 3A,B). However, no such relationship was observed for miR-365a-3p (r = 0.043). \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Groups**} & \multicolumn{4}{c}{**mRNA Level**} \\ \cline{2-5}  & \multicolumn{2}{c}{**NFE2L2**} & \multicolumn{2}{c}{**KEAP1**} \\ \cline{2-5}  & **FC vs. C** & **FC vs. F** & **FC vs. C** & **FC vs. F** \\ \hline F & \(-1.48\) & - & \(-1.10\) & - \\ F + SMF & \(-1.27\) & \(1.17\) & \(-1.43\) & \(-1.30\) \\ SMF & \(-1.42\) & \(1.04\) & \(-2.21\) & \(-2.00\) \\ \hline \hline \end{tabular}  
* FC—fold change; C—control cells; F—cells that had been treated with fluoride ions; F + SMF—cells that had been treated with fluoride ions and simultaneously exposed to a static magnetic field; SMF—cells that had only been exposed to a static magnetic field.  
\end{table} 
Table 2: Comparison of the gene expression levels (fold change) among the studied cell groups. Figure 1: Relative mRNA expression of the _NFE2L2_ (**A**) and _KEAP1_ (**B**) genes in cells that had been treated with fluoride and cells that had been exposed to a static magnetic field. The results are presented as the mean \(\pm\) SD; C—control cells; F—cells that had only been treated with fluoride; SMF—cells that had only been exposed to a static magnetic field; F + SMF—cells that had simultaneously been exposed to fluoride and a static magnetic field; * \(p\) < 0.05 vs. C, # \(p\) < 0.05 vs. F.  
Figure 2: Relative miRNA expression of miR-28-3p (**A**), miR-29b-1-5p (**B**), miR-365a-3p (**C**) and miR-141-3p (**D**) in the cells that had been treated with fluoride and the cells that had been exposed to a static magnetic field. The results are presented as the mean \(\pm\) SD; C—control cells; F—cells that had been treated with fluoride; SMF—cells that had been exposed to a static magnetic field; F + SMF—cells that had simultaneously been exposed to fluoride and a static magnetic field; * \(p\) < 0.05 vs. C. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Groups**} & \multicolumn{6}{c}{**miRNA Level**} \\ \cline{2-9}  & \multicolumn{2}{c}{**miR-28-3p**} & \multicolumn{2}{c}{**miR-29b-1-5p**} & \multicolumn{2}{c}{**miR-365a-3p**} & \multicolumn{2}{c}{**miR-141-3p**} \\ \cline{2-9}  & **FC vs. C** & **FC vs. F** & **FC vs. C** & **FC vs. F** & **FC vs. C** & **FC vs. F** & **FC vs. C** & **FC vs. F** \\ \hline F & 1.49 & - & 1.54 & - & 1.39 & - & 1.18 & - \\ F + SMF & 1.17 & \(-\)1.28 & 1.26 & \(-\)1.22 & 1.14 & \(-\)1.21 & 1.58 & 1.34 \\ SMF & 1.17 & \(-\)1.27 & 1.42 & \(-\)1.08 & 1.22 & \(-\)1.14 & 1.90 & 1.62 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of the miRNA expression levels (fold change) among studied cell groups. In the case of miR-141-3p regulating the expression of the _KEAP1_ gene, no statistically significant differences in its level were observed between the studied groups of cells (Figure 2D, Table 3). However, it can be seen that an SMF may increase its expression level.