Effects of bio-strength electric field on the motility and CD9 expression of human epidermal cell line HaCaT and mouse epidermal cells

Objective To investigate the regulatory effect of bio-strength electric field (EF) on the motility and CD9 expression of human epidermal cell line HaCaT and mouse epidermal cells. Methods The experimental research method was used. Human immortal epidermal cell line HaCaT cells in logarithmic growth phase and primary epidermal cells isolated from 16 BALB/c mice (no matter male or female) aged 1-3 days were used for experiments. HaCaT cells were divided into EF group treated for 3 h at the EF intensity of 200 mV/mm and sham EF group with simulated treatment. The cell migration (direction, displacement velocity, and trajectory velocity, with 46 samples in EF group and 34 samples in sham EF group) and arrangement were observed in the living cell workstation, and the distribution and expression of CD9 protein were detected by immunofluorescence method. Both HaCaT cells and mouse epidermal cells were divided into sham EF group (simulated treatment) and EF groups treated respectively for 3 h at the corresponding EF intensity of 50, 100, 200, and 400 mV/mm. Both HaCaT cells and mouse epidermal cells were divided into blank control group without any treatment, and 1 h group, 3 h group, and 6 h group treated with EF at the intensity of 200 mV/mm for corresponding time respectively. The expression of CD9 protein was detected by Western blotting (

=3). Data were statistically analyzed with Mann-Whitney

test, one-way analysis of variance, independent sample

test and least significant difference test. Results Within 3 hours of treatment, HaCaT cells in EF group tended to move towards the negative electrode obviously, while HaCaT cells in sham EF group moved randomly around the origin; compared with those of sham EF group, the directivity of HaCaT cells in EF group was significantly enhanced, and the displacement velocity and trajectory velocity were significantly increased (

=-3.975, -6.052, -6.299,

<0.01). After 3 hours of treatment, the long axis of HaCaT cells in EF group was perpendicular to the direction of EF, while HaCaT cells in sham EF group arranged randomly. After 3 hours of treatment, the expression of CD9 protein in HaCaT cells in EF group was significantly down-regulated compared with that of sham EF group (

=4.527,

<0.01), although both expressed on cytomembrane. After 3 hours of treatment, the expression of CD9 protein in HaCaT cells and mouse epidermal cells in sham EF group, 50 mV/mm group, 100 mV/mm group, 200 mV/mm group, and 400 mV/mm group were 0.332±0.021, 0.283±0.032, 0.254±0.020, 0.231±0.041, 0.212±0.031 and 0.565±0.021, 0.453±0.022, 0.389±0.020, 0.338±0.021, 0.233±0.011, respectively. For both types of cells, compared with that of sham EF group, the expression of CD9 protein in cells was significantly decreased in the four groups of EF treatment (

<0.01); compared with that of 50 mV/mm group, the expression of CD9 protein in cells was significantly decreased in the other three groups of EF treatment (

<0.01); compared with that of 100 mV/mm group, the expression of CD9 protein in cells was significantly decreased in 200 mV/mm group and 400 mV/mm group (

<0.01); compared with that of 200 mV/mm group, the expression of CD9 protein in cells was significantly decreased in 400 mV/mm group (

<0.01). The expression levels of CD9 protein in HaCaT cells and mouse epidermal cells in blank control group, 1 h group, 3 h group, and 6 h group were 0.962±0.031, 0.784±0.020, 0.531±0.021, 0.409±0.011 and 0.963±0.031, 0.872±0.031, 0.778±0.040, 0.591±0.041, respectively. For both types of cells, compared with that of blank control group, the expression of CD9 protein in cells was significantly decreased in 1 h group, 3 h group, and 6 h group (

<0.01); compared with that of 1 h group, the expression of CD9 protein in cells was significantly decreased in 3 h group and 6 h group (

<0.05 or

<0.01); compared with that of 3 h group, the expression of CD9 protein in cells was significantly decreased in 6 h group (

<0.01). Conclusions The bio-strength intensity EF can induce the directional migration and arrangement of HaCaT cells and down-regulate the expression of CD9 in HaCaT cells and mouse epidermal cells in a time-dependent and intensity-dependent manner.