Evaluation of electrical stimulation for ischemic wound therapy: a feasibility study using the lapine wound model

Chronic wounds are a major secondary complication for many people with impaired mobility. Electrical stimulation (ES) has been recommended as a adjunctive therapy, however optimal treatment paradigms have not been established. Our group seeks to determine the basic mechanisms underlying ES wound therapy, an area where understanding is currently limited. A feasibility study was carried out to develop the Ahn/Mustoe lapine wound model for systematic investigation of the effects of electrical stimulation on ischemic wound therapy. A standardized surgical procedure incorporated a hybrid stimulation system comprising an implantable mini-stimulator and surface electrodes, with creation of repeatable ischemic wounds. Twenty mature male New Zealand white rabbits (3 kg weight) were employed to evaluate the effects of two empirically selected stimulation paradigms applied continuously for 7-21 days, using each animal as its own control. Outcomes measures included transcutaneous blood gas levels, histology, total RNA content and analysis of alpha2 (I) collagen (COL-I), type IV collagen (COL-IV), alpha1 (V) collagen (COL-V), and vascular endothelial growth factor (VEGF) expression using real-time quantitative PCR. All markers for stimulated wounds showed increased activity relative to non-stimulated control wounds between 7 and 14 days following injury, with peak activity at 14 days. By 21 days post-injury, all activity had returned to near baseline level. VEGF and COL-IV levels were found to be significantly higher for pattern A (110 mus pulse width) compared to pattern B (5 mus pulse width) at 14 days, implying that pattern A may be more effective at promoting angiogenesis. All wounds were fully re-epithelialized by 10 days post-injury. Both COL-I and COL-V showed statistically significant (P < 0.05) increased activity between day 7 and day 14 for pattern A, potentially indicating a continued effect on matrix remodeling. The early closure of all wounds implies that the rabbit ear model may not be valid for chronic wound studies.