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

Abstract

Different species respond differently to severe injury, such as limb loss. In species that regenerate, limb loss is met with complete restoration of the limbs’ form and function, whereas in mammals the amputated limb’s stump heals and scars. In in vitro studies, electrical stimulation (EStim) has been shown to promote cell migration, and osteo- and chondrogenesis. In in vivo studies, after limb amputation, EStim causes significant new bone, cartilage and vessel growth. Here, in a rat model, the stumps of amputated rat limbs were exposed to EStim, and we measured extracellular matrix (ECM) deposition, macrophage distribution, cell proliferation and gene expression changes at early (3 and 7 days) and later stages (28 days). We found that EStim caused differences in ECM deposition, with less condensed collagen fibrils, and modified macrophage response by changing M1 to M2 macrophage ratio. The number of proliferating cells was increased in EStim treated stumps 7 days after amputation, and transcriptome data strongly supported our histological findings, with activated gene pathways known to play key roles in embryonic development and regeneration. In conclusion, our findings support the hypothesis that EStim shifts injury response from healing/scarring towards regeneration. A better understanding of if and how EStim controls these changes, could lead to strategies that replace scarring with regeneration.

Electrical stimulation in bone tissue engineering treatments

“…EStim's effect of upregulating osteogenic gene (Spp2 and Bmp2) transcription in macrophages could help explain its role in stimulating osteogenesis [89]. In vivo, low-voltage EStim was shown to modify macrophage response by changing the M1 to M2 macrophage ratio [97]. Overall, these findings suggest that EStim can exert a significant effect on these macrophage sub-populations.…”

“…During this process, progenitor cells differentiate into chondrocytes which later undergo maturation and mineralization, finally resulting in new bone tissue (reviewed in [95]). Whereas the positive effects of EStim on endochondral ossification have been shown in previous studies [29,96,97], there few studies focused on analyzing the effects EStim has on endochondral ossification and MSC chondrogenic differentiation (reviewed in [98]). In our own in vitro studies, we were not able to detect a positive effect of direct current EStim on rat MSC chondrogenic differentiation (unpublished data).…”

Biomedical applications of electrical stimulation

“…For skin cells, EStim has shown to guide the migration of epidermal stem cells (EpSCs) to regulate wound healing [57]. EStim can shift injury response from healing/scarring toward regeneration by promoting cell proliferation, generating less condensed collagen ibrils, and by modifying macrophage responses [58]. AC EStim of 50 µA, generated by a triboelectric nanogenerator (TENG), has been shown to promote ibroblast cell proliferation [59].…”

Organic Bioelectronics: Using Highly Conjugated Polymers to Interface with Biomolecules, Cells, and Tissues in the Human Body

“…[ 51,52,66 ] Within the field of regenerative medicine, there are multiple approaches to electrical stimulation. These methods have been used to heal bone fractures ( Figure ), [ 67,68 ] induce regenerative healing responses, [ 69 ] and have been proposed for a range of other applications. [ 47 ] Ultimately, the complexity and influence of bioelectric signals is a major motivation for developing better bioelectronic interfaces.…”