Experimental models for controlled burn injuries in rats: a systematic analysis of original methods and burn devices

AIM Despite a wide variety of models found in literature, choosing the right one can be difficult as many of them are lacking precise methodology. This study aims to analyze and compare original burn models in terms of burn device and technique, parameters, and wound depth assessment. METHODS A systematic search was performed according to PRISMA guidelines on studies describing original experimental burn models in rats. The adapted PICO formula and ARRIVE checklist were followed for inclusion and assessment of quality of studies. Characteristics of animals, burn technique, burn parameters and method of histological confirmation of burn depth were recorded. RESULTS Twenty-seven studies were included in the final analysis. Most studies used direct contact with skin for burn infliction (n=20). The rat’s dorsum was the most common site (n=18). Ten studies used manually controlled burn devices, while ten designed automatic burn devices with control over temperature (n=10), exposure time (n=5), and pressure (n=5). Most studies (n=7) used a single biopsy taken from the center of the wound to confirm burn depth immediately after burn infliction. CONCLUSION From the wide variety of burn models in current literature, our study provides an overview of the most relevant experimental burn models in rats aiding researchers to understand what needs to be addressed when designing their burn protocol. Models cannot be compared as burn parameters variate significantly. Assessment of burn depth should be done in a standardized, sequential fashion in future burn studies to increase reproducibility.

Recent Advances in Experimental Burn Models

Experimental burn models are essential tools for simulating human burn injuries and exploring the consequences of burns or new treatment strategies. Unlike clinical studies, experimental models allow a direct comparison of different aspects of burns under controlled conditions and thereby provide relevant information on the molecular mechanisms of tissue damage and wound healing, as well as potential therapeutic targets. While most comparative burn studies are performed in animal models, a few human or humanized models have been successfully employed to study local events at the injury site. However, the consensus between animal and human studies regarding the cellular and molecular nature of systemic inflammatory response syndrome (SIRS), scarring, and neovascularization is limited. The many interspecies differences prohibit the outcomes of animal model studies from being fully translated into the human system. Thus, the development of more targeted, individualized treatments for burn injuries remains a major challenge in this field. This review focuses on the latest progress in experimental burn models achieved since 2016, and summarizes the outcomes regarding potential methodological improvements, assessments of molecular responses to injury, and therapeutic advances.

Model to Predict Probability of Significant Skin Burn Injury From a Directed-Energy Source

ABSTRACT Introduction Millimeter wave directed energy in the frequency regime of 94-95 GHz has potential for use in numerous military applications including crowd control and area denial. Although proven to be very safe, millimeter wave energy has the potential, because of accidental over exposure, to produce significant injuries. Currently, the Dynamic Thermal Model (DTM), developed by Beason and colleagues, is used to calculate the temperature profile in skin undergoing (millimeter wave) heating, using an all-or-nothing threshold of injury. Risk of significant injury (RSI) is determined by product of the probability of an injury outcome on a region of the body times the probability of that the injury will occur. Thus, a threshold injury determination may over predict burn probability and fail safety requirements. This work augments the DTM, replacing the current threshold value of injury with a probabilistic risk of injury to better quantify the risk of significant injury. Materials and Methods In this study, continuous probabilistic dose–response models using logistic regression analysis have been developed to account for mild second-degree, deep second-degree, and third-degree burn injuries based on a historic experimental burn dataset. Statistical analysis methods such as Hosmer–Lemeshow statistics, McFadden’s pseudo R2 and receiver operator characteristic were used to validate the models against an independent experimental burn dataset. Results Comparison of logistic models fit using damage coefficients from the literature showed that Mehta and Wong provided the best fits historic burn data, which was corroborated by the McFadden pseudo R2 statistic for mild second-degree, deep second-degree, and third-degree severity. Conclusion The dose–response models developed in this study are shown to be an excellent predictor of burn injury for each severity. The DTM was repackaged with the probabilistic burn models to more accurately determine the risk of significant burn injury.

MONITORING OF THE STATE OF THE SKIN BLOOD FLOW IN THE DYNAMICS OF EXPERIMENTAL BURN DISEASE DEVELOPMENT

The purpose of this study was to study the state of skin microcirculation in healthy and burned rats. It was found that thermal trauma has a negative impact on the microcirculation system, which is manifested in a decrease in the intensity of blood flow through small-diameter vessels

Effects of carnosine, ankaferd and silver sulfadiazine on an experimental burn model; roles of irisin and HSP70

In this study, the effects of carnosine, ankaferd and 1% silver sulfadiazine applied topically on second-degree burns were investigated and the roles of irisin and Heat shock protein 70 (HSP70) in this healing process were evaluated. Ninety male albino rats were used and divided into 5 groups. The groups classified as; control, burn, burn + carnosine (CAR), burn + ankaferd (ABS) and burn + silver sulfadiazine (SS). It was found that level of irisin increased in the first week and decreased in the second week in the burn and CAR groups. In the ABS and SS groups, the level of irisin was determined that started to increase in the first week and continued to increase in the second week. The level of HSP70 was found to increased in the first week in burn and CAR groups and decreased in the second week, but started to increase in the second week in ABS and SS groups. Both levels of irisin and HSP70 were observed to decreased in all treatment groups in the third week. In this study, it was shown that ankaferd and silver sülfadiazine treatments cause an increase in the irisin levels in the early period and a gradually increase in HSP70 levels in the later period in burns. The inflammatory response was observed to be limited in the early period in the ankaferd and sulfadiazin groups. It was concluded that these findings were effective in early wound healing in burns.

Human keratinocyte (HaCaT) stimulation and healing effect of the methanol fraction from the decoction from leaf from Sideroxylon obtusifolium (Roem. & Schult.) T.D. Penn on experimental burn wound model

The larger number of plants, with therapeutic potential, popularly used in Northeastern Brazil is due to their easy access and the great Brazilian biodiversity. Previously, was demonstrated that the methanol fraction from Sideroxylon obtusifolium (MFSOL) promoted an anti-inflammatory and healing activity in excisional wounds. Thus, this work aimed to investigate the healing effects of MFSOL on human keratinocytes cells (HaCaT) and experimental burn model injuries. HaCaT cells were used to investigate migration and proliferation of cell rates. Female Swiss mice were subjected to second-degree superficial burn protocol and divided into four treatment groups: Vehicle (cream-base), 1.0% Silver Sulfadiazine (Sulfa), and 0.5% or 1.0% MFSOL cream (CrMFSOL). Samples were collected for quantification of the inflammatory mediators and histological analyses after 3, 7 and 14 days on evaluation. As result, MFSOL (50 μg/ml) stimulated HaCaT cells by increasing proliferation and migration rates. Moreover, CrMFSOL 0.5% attenuated myeloperoxidase (MPO) activity and also stimulated the release of IL-1β and IL-10, after 3 days with treatment. CrMFSOL 0.5% enhanced wound contraction, promoted tissue remodeling improvement and highest collagen production after 7 days, and VEGF release after 14 days. Therefore, MFSOL evidenced the stimulation of human keratinocyte (HaCaT) cells and improvements on wound healing via inflammatory modulation on burn injuries.

Temporal variability of greenhouse gas and reactive gas emission factors during a two-week-long tropical peatland experimental burn

<p>Smoke from peatland wildfires contributes significantly to global greenhouse gas (GHG) emissions, while reactive gases and particulates cause transboundary haze episodes. Haze is the large-scale accumulation of smoke at low altitudes, especially frequent in Southeast Asia during dry periods. Understanding emissions from peatland fires plays a vital role in calculating GHG budgets, forecasting haze events and modelling future climate change. However, only a handful of field studies or laboratory experiments on tropical peat fire smoke have been undertaken to date. Of the few studies that have investigated tropical peatland fire emissions, there exists substantial inter-study variabilities of emission factors (EFs) with some gas emission factors varying by a factor of 10 between studies. Explaining the nature of such variability remains a challenge. In August/September 2018 in Riau, Indonesia, we carried out the first field-scale experimental burn on a tropical peatland (the GAMBUT Workshop), aiming to understand how fires ignite, how they spread, and how emissions vary across the life-cycle of a peatland fire. Our site was a heavily degraded tropical peatland subjected to long-term drainage, logging, and agricultural conversion. Here we present the field measurements of gas emissions from the fire experiment. Open-path Fourier transform infrared spectroscopy (OP-FTIR) was used to retrieve mole fractions of 13 gas species. EFs from 40 measurement sessions over two weeks of burning during different fire stages (e.g., slash and burn ignition, smouldering spread or suppression) and weather events (e.g., wind or rainfall) were calculated and reported. We present field evidence to indicate that EFs vary significantly among fire stages and weather events. Heterogenous physicochemical properties of our peatland site (e.g. moisture content, inorganic content and bulk density) were also found to affect the EFs. We discuss the implications for air quality forecasting, suggesting the necessity for more complex mapping of peatland heterogeneity/land-use for emissions inventories and temporally variable emissions factors, depending on the time since the initiation of a fire event.</p>