Electrical stimulation promotes wound healing by enhancing dermal fibroblast activity and promoting myofibroblast transdifferentiation.

Mahmoud Rouabhia,Habib Derbali,Ze Zhang,Hyunjin Park,Shiyun Meng,David T Eddington

doi:10.1371/journal.pone.0071660

Abstract

Electrical stimulation (ES) has long been used as an alternative clinical treatment and an effective approach to modulate cellular behaviours. In this work we investigated the effects of ES on human skin fibroblast activity, myofibroblast transdifferentiation and the consequence on wound healing. Normal human fibroblasts were seeded on heparin-bioactivated PPy/PLLA conductive membranes, cultured for 24 h, and then exposed to ES of 50 or 200 mV/mm for 2, 4, or 6 h. Following ES, the cells were either subjected to various analyses or re-seeded to investigate their healing capacity. Our findings show that ES had no cytotoxic effect on the fibroblasts, as demonstrated by the similar LDH activity levels in the ES-exposed and non-exposed cultures, and by the comparable cell viability under both conditions. Furthermore, the number of viable fibroblasts was higher following exposure to 6 h of ES than in the non-exposed culture. This enhanced cell growth was likely due to the ES up-regulated secretion of FGF-1 and FGF-2. In an in vitro scratch-wound assay where cell monolayer was used as a healing model, the electrically stimulated dermal fibroblasts migrated faster following exposure to ES and recorded a high contractile behaviour toward the collagen gel matrix. This enhanced contraction was supported by the high level of α-smooth muscle actin expressed by the fibroblasts following exposure to ES, indicating the characteristics of myofibroblasts. Remarkably, the modulation of fibroblast growth continued long after ES. In conclusion, this work demonstrates for the first time that exposure to ES promoted skin fibroblast growth and migration, increased growth factor secretion, and promoted fibroblast to myofibroblast transdifferentiation, thus promoting wound healing.

Highlights

It is well known that the endogenous electrical field (EF) in the human body plays several critical physiological roles, including the electrical activation of the nervous system and the muscles
The release of lactate dehydrogenase (LDH) activity showed no significant difference when human skin fibroblasts were exposed to 50 or 200 mV/mm for 2, 4, or 6 h and cultured for 24 h post-exposure compared to non-Electrical stimulation (ES)-exposed cells (Ctrl) (Figure 1)
It is interesting to note that no difference was found in LDH levels between the ES intensities and exposure times, which suggests that ES had no toxic effect on the fibroblasts

Summary

Introduction

It is well known that the endogenous electrical field (EF) in the human body plays several critical physiological roles, including the electrical activation of the nervous system and the muscles. Injured epidermis is characterised by a TEP short circuit that gives rise to a measurable DC current efflux between 1 and 10 mA/cm and an estimated current density up to 300 mA/cm near the edge of the wound [3,4,5]. This wound current corresponds to a relatively steady local EF between 40 and 200 mV/mm. The EF persists until complete wound re-epithelialisation is achieved [4,6,7,8]

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Conclusion