Effect of reversed polarity microcurrent electrical stimulation on an experimentally induced Achilles tendon injury in male albino rats: a histological and immunohistochemical study

Background:The application of electrical stimulation can lead to a greater and faster increase in the rate of wound healing, especially when applying the cathodal (negative) stimulation for the first week, followed by the anodal (positive) polarity for the rest of the treatment period.Aim:The present work aimed to study the effect of polarity reversal of microelectrical current stimulation (MES) on the healing process in an experimentally induced Achilles tendon injury in rats. Materials and methods;Forty three male albino rats were used in this study; they were classified into group I (control group) and group II (experimentally injured group), which was further classified into subgroups I, II, III, and IV. Subgroup I represents the injured tendon without MES treatment, whereas subgroups II, III, and IV represent the MES-treated ones. The obtained tendon sections were subjected to H E staining, Masson’s trichrome stain, and immunohistochemical staining for alpha smooth muscle actin (αSMA), followed by morphometric study and statistical analysis. Results:Subgroup I showed signs of inflammation, a few thin irregularly arranged collagen, active fibroblasts that start to align in rows on the regenerating collagen bundles, and αSMA immunoreactivity. In anodal-treated tendons, signs of inflammation had started to disappear; collagen fibers appeared thin and irregularly arranged, active fibroblasts were obviously observed and minimal αSMA immunoreactivity were recorded only in subgroup II. Cathodal-treated tendons showed rapid disappearance of cellular infiltration; most collagen fibers appeared regularly arranged with mature fibrocytes in between and multiple ovoid αSMA immunoreactive myofibroblasts were maximally observed in subgroup II. Conclusion:αSMA was suggested to play a role in wound healing due to its high immunoreactivity in myofibroblasts during wound healing. Moreover, the application of electrical stimulation by applying cathodal (negative) stimulation for the first week, followed by anodal (positive) polarity for the rest of the treatment period may lead to better repaired tissue due to myofibroblast directional attraction to the cathode, especially when applied for 4-week duration.