Electrical stimulation shifts healing/scaring towards regeneration in a rat limb amputation model

Severe Injury, such as limb loss, meets elicits different tissue response in different species. Whereas in regenerative species injury response leads to restoration of both form and function of lost limb, in mammals this response ends in scar formation. Previous studies demonstrated that electrical stimulation (EStim) influences cellular responses in vitro, and induces significant new bone, cartilage and vessel growth after limb amputation in vivo. Here, we question if EStim modifies events occurring after limb amputation in favor of a regenerative response. Therefore the effects of EStim on extracellular matrix (ECM) deposition, macrophage distribution, cell proliferation and gene expression changes were investigated in rat limb ampuitation model in early (3 and 7 days) and later stages (28 days) by means of histological, immunohistochemical and gene expression analysis. Results show differences in ECM deposition of EStim treated and non-treated limb stumps, with less condensed collagen fibrils deposited in EStim group. EStim treatment modified macrophages response by increasing the ratio of both, M1 and M2, macrophages at day 3 and the ratio of M2 macrophages at day 7. Increased number of proliferating cells was also observed in EStim treated stumps 7 days after amputation. Transcriptome analysis data support our histological findings and additionally show that EStim activates gene pathways playing role in development and regeneration. In conclusion, our observations support the hypothesis that EStim could shift injury response from healing/scarring towards regeneration. A greater understanding of underlying mechanisms will bring us closer to the possibility of controlling injury response, which could later be translated into new treatments.