A novel in vitro assay for electrophysiological research on human skin fibroblasts: Degenerate electrical waves downregulate collagen I expression in keloid fibroblasts

Electrical stimulation (ES) has been used for the treatment of wounds and has been shown to alter gene expression and protein synthesis in skin fibroblasts in vitro. Here, we have developed a new in vitro model system for testing the effects of precisely defined, different types of ES on the collagen expression of normal and keloid human skin fibroblasts. Keloid fibroblasts were studied because they show excessive collagen production. Both types of fibroblasts were electrically stimulated with alternating current (AC), direct current (DC) or degenerate waves (DW). Cells were subjected to 20, 75 and 150 mV/mm electric field strengths at 10 and 60 Hz frequencies. At lower electric fields, all types of ES upregulated collagen I in both cell types compared to controls. However, at higher electric field strength (150 mV/mm) and frequency (60 Hz), DW maximally downregulated collagen I in keloid fibroblasts, yet had significantly lower cytotoxic effects on normal fibroblasts than AC and DC. Compared to unstimulated cells, both normal skin and keloid fibroblasts showed a significant decrease in collagen I expression after 12 h of DW and AC stimulation. In contrast, increasing amplitude of DC upregulated collagen I and PAI-1 gene transcription in normal and keloid fibroblasts, along with increased cytotoxicity effects. Thus, our new preclinical assay system shows highly differential effects of specific types of ES on human fibroblast collagen expression and cytotoxicity and identifies DW of electrical current (DW) as a promising, novel therapeutic strategy for suppressing excessive collagen I formation in keloid disease.