Low current electrical stimulation upregulates cytokine expression in the anal sphincter

Stem cells are an emerging treatment for regeneration of damaged anal sphincter tissues. Homing to the site of injury can be potentiated by stromal derived factor 1 (SDF-1) and monocyte chemotactic protein 3 (MCP-3) expression. The effects of electrical stimulation (ES) on upregulation of these cytokines were investigated.

The anal sphincter complex of Sprague Dawley rats was stimulated with current of 0.25 mA, pulse duration of 40 pulses/s, pulse width of 100 μs, and frequency of 100 Hz for 1 or 4 h. Sham was created using the same needle which was inserted into the anal sphincter without electrical stimulation in different groups of animals. The rats were euthanized immediately or 24 h after stimulation. Cytokine analysis was performed using real-time polymerase chain reaction. Statistical analysis was performed.

Results are presented as a fold increase compared to sham that was normalized to 1. SDF-1 and MCP-3 immediately after 1 h were 2.5 ± 0.77 and 3.1± 0.93 vs. sham, respectively, showing significant increase. After 1-h stimulation and euthanasia 24 h after, SDF-1 and MCP-3 were 1.49 ± 0.16 and 1.51± 0.14 vs. sham, respectively, showing significant increase. Immediately and 24 h after 4-h stimulation, SDF-1 was 1.21 ± 0.16 and 0.54 ± 0.16 vs. sham, respectively, and was not significantly different. Immediately and 24 h after 4-h stimulation, MCP-3 was 1.29 ± 0.41 and 0.35 ±1.0 vs. sham, respectively, and was not significantly different. SDF-1 and MCP-3 after 1 h were significantly higher than after 4 h of stimulation at both time points.

Electrical stimulation for 1 h significantly upregulates SDF-1 and MCP-3 expression that persists for 24 h. Prolonged stimulation reduced chemokine expression, suggesting electrolysis of cells.