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Hypertrophic scar is a major clinical outcome of deep-partial thickness to full thickness thermal burn injury. Appropriate animal models are a limitation to burn research due to the lack of, or access to, animal models which address the endpoint of hypertrophic scar. Lower species, such as rodents, heal mainly by contracture, which limits the duration of study. Higher species, such as pigs, heal more similarly to humans, but are associated with high cost, long duration for scar development, challenges in quantifying scar hypertrophy, and poor manageability. Here, we present a quantifiable deep-partial thickness burn model in the rabbit ear. Burns were created using a dry-heated brass rod for 10 and 20 seconds at 90 °C. At the time of eschar excision on day 3, excisional wounds were made on the contralateral ear for comparison. Burn wound progression, in which the wound size expands over time is a major distinction between excisional and thermal injuries, was quantified at 1 hour and 3 days after the injuries using calibrated photographs and histology and the size of the wounds was found to be unchanged from the initial wound size at 1 hour, but 10% in the 20 seconds burn wounds at 3 days. A quantifiable hypertrophic scar, measured by histology as the scar elevation index, was present in both 20 seconds burn wounds and excisional wounds at day 35. ImageJ measurements revealed that the 20 seconds burn wound scars were 22% larger than the excisional wound scars and the 20 seconds burn scar area measurements from histology were 26% greater than in the excisional wound scar. The ability to measure both burn progression and scar hypertrophy over a 35-day time frame suits this model to screening early intervention burn wound therapeutics or scar treatments in a burn-specific scar model.

Biomaterials capable of neutralizing specific cytokines could form the basis for treating a broad range of conditions characterized by intense, local inflammation. Severe burns, spanning partial- to full-thickness of the dermis, can result in complications due to acute inflammation that contributes to burn progression, and early mediation may be a key factor in rescuing thermally injured tissue from secondary necrosis to improve healing outcomes. In this work, we examined the effects on burn progression and influence on the inflammatory microenvironment of topical application of anti-tumor necrosis factor-α (anti-TNF-α) alone, mixed with hyaluronic acid (HA) or conjugated to HA. We found that non-conjugated anti-TNF-α decreased macrophage infiltration to a greater extent than that conjugated to HA; however, there was little effect on the degree of progression or IL-1β levels. A simple transport model is proposed to analyze the results, which predicts qualitative and quantitative differences between untreated burn sites and those treated with the conjugates. Our results indicate that conjugation of anti-TNF-α to high molecular weight HA provides sustained, local modulation of the post-injury inflammatory responses compared to direct administration of non-conjugated antibodies.

In this study, we explored whether topical application of antibodies targeting tumor necrosis factor-α (TNF-α) or interleukin-6 (IL-6) conjugated to hyaluronic acid (HA) could reduce the extension of necrosis by modulating inflammation locally in a partial-thickness rat burn model. Partial-thickness to deep partial-thickness burn injuries present significant challenges in healing, as these burns often progress following the initial thermal insult, resulting in necrotic expansion and increased likelihood of secondary complications. Necrotic expansion is driven by a microenvironment with elevated levels of pro-inflammatory mediators, and local neutralization of these using antibody conjugates could reduce burn progression. Trichrome-stained tissue sections indicated the least necrotic tissue in (anti-TNF-α)-HA-treated sites, while (anti-IL-6)-HA-treated sites displayed similar outcomes to saline controls. This was confirmed by vimentin immunostaining, which demonstrated that HA treatment alone reduced burn progression by nearly 30%, but (anti-TNF-α)-HA reduced it by approximately 70%. At all time points, (anti-TNF-α)-HA-treated sites showed reduced tissue levels of IL-1β compared to controls, suggesting inhibition of a downstream mediator of inflammation. Decreased macrophage infiltration in (anti-TNF-α)-HA-treated sites compared to controls was elucidated by immunohistochemical staining of macrophages, suggesting a reduction in overall inflammation in all time points. These results suggest that local targeting of TNF-α may be an effective strategy for preventing progression of partial-thickness burns.