Burn Wound Progression Research Articles

Topical application of anti-inflammatory agents on burn wounds and their effect on healing

Advancements in the treatment of burns have considerably improved overall survival rates, but they have also highlighted several long-term sequelae related to the injury. Hypertrophic scars can impair function, reduce quality of life, and require multiple procedures as well as physical therapy. The purpose of this study was to investigate the effects of topical application of anti-inflammatory drugs in the treatment of burns. Up to 15 deep-partial thickness burns were created on the dorsum of four anesthetized swine. Subsequently, the burn wounds were randomized to receive amiloride, celecoxib, dexamethasone or minocycline mixed in a hydrogel. Silver sulfadiazine cream and blank hydrogel acted as controls. The animals were followed for 90 days and the wounds were assessed on days 3, 7, 14, 28 and 90 post-burn. Assessments were performed using photographs (macroscopic healing, contraction), laser-speckle imaging (blood perfusion), 3D camera (scarring, pigmentation), and histology (inflammation, burn depth, epidermal maturation). Inflammation was present in all burn wound histology specimens and peaked on day 7 in all groups. Regardless of the treatment the burns progressed and were deeper on day 7 in comparison to day 3. The burns were 50 – 80 % healed by day 14, but no significant differences were observed. No differences in epidermal thickness, rete ridges, contraction, hypopigmentation, or scar elevation were seen on day 90. Topical anti-inflammatories did not significantly decrease inflammation or mitigate burn wound progression in deep partial thickness burns in pigs. Also, no significant differences in wound healing or quality of healing were observed.

Comparative analysis of thermal damage to laser-irradiated breast tumor based on Fourier conduction and non-Fourier heat conduction models: A numerical study

In recent decades, laser technology has been widely used in surgeries and thermal therapies. To ensure patient safety and enhance therapeutic effectiveness in laser applications, it is crucial to accurately analyze burn injuries during the treatment process. In this study, a bioheat transfer model that includes the effects of metabolic heat generation, capillary blood vessels, and relaxation times of heat flux and temperature gradient was developed to study the non-Fourier heat conduction behavior in 2-D spherical breast tumor during the laser hyperthermia process. By employing different heat conduction models and the Arrhenius burn integration, the temperature distribution and laser-induced thermal damage to tumors were obtained. The progression of burn injury in time and the effect of various parameters on it were investigated. It was observed that the DPL model provides more reliable results in comparison with the CV model in predicting thermal damage to bio-tissue when non-Fourier effects are taken into consideration. The results showed that increasing heat flux phase lag leads to severe thermal damage, earlier onset of empyrosis, and wider and deeper burn injury. However, a greater phase lag of temperature gradient results in lower and superficial thermal damage, milder burn, later onset of empyrosis, and smaller burned area. The effect of laser power density on the onset time of different degrees of burn and their sensitivity to input power were investigated, and the results were represented graphically. Finally, investigation of wave propagation in various tissues revealed that the wave propagation speed is not constant and reduces as time increases.

76 Resuscitation Volumes Affect Perfusion and Inflammatory Cytokine Expression in Peri-Burn Skin: Implications for Burn Conversion

Abstract Introduction Fluid resuscitation after thermal injury is paramount to avoiding the effects of burn shock and restoring organ perfusion. Both over and under resuscitation can lead to unintended consequences affecting patient outcomes. While many studies have focused on the systemic effects of resuscitation, there is limited information on how fluid resuscitation might affect the burn wound, specifically burn wound progression, in the acute period. Furthermore, the mechanisms underlying burn wound progression are not fully understood. For these reasons, a polytrauma swine model was used to investigate varying levels of resuscitation on burn wound dynamics. Methods Nine female Yorkshire pigs were used in this experiment. Pigs were anesthetized and subjected to 40% total body surface area burn and 15% hemorrhage. Pigs were randomized (n=3) to receive different resuscitative strategies: decision support driven (adequate, 2-4ml/kg/%TBSA), fluid withholding (under, < 2ml/kg/%TBSA) or high constant rates (over, > >4ml/kg/%TBSA). Pigs were then monitored for 24hrs in an intensive care setting prior to necropsy. Laser Doppler Imaging (LDI) was conducted over the burn wound and peri-wound skin at pre-determined timepoints to assess perfusion. Skin biopsies were also taken from the burn, peri-burn (within 2cm of burn) and normal skin areas. RNA was isolated from normal skin and peri-burn skin biopsies at hour 6 and qRT-PCR was conducted to assess levels of common inflammatory cytokines: interlukein-6 (IL-6), chemokine CXC motif ligand-8 (CXCL8), and interferon-gamma (IFN-y). Results At hour 2, LDI analysis demonstrated increased perfusion in the peri-burn skin of over-resuscitated animals when compared to adequate and under-resuscitated groups (p=0.002 and p=0.007, respectively). At hour 6, peri-burn skin of over-resuscitated animals showed increased perfusion when compared to the adequate resuscitation groups (p=0.01). At hour 6, peri-burn skin samples showed increased expression of all 3 cytokines in adequately resuscitated animals when compared to over and under resuscitated groups (IL-6: 2.94 vs. 1.47 and -0.11-fold, CXCL8: 9.04 vs. 0.82 and -0.31-fold, IFN-g: 2.09 vs. -0.48 and -0.81-fold). Conclusions This animal model shows differences in both perfusion and inflammatory cytokine expression in peri-burn skin samples based on resuscitation strategy. Varying levels of resuscitation following burn can have wide ranging consequences that may affect burn wound progression. Applicability of Research to Practice Under or over-resuscitation may lead to local changes in the burn wound that could affect the overall severity and evolution of the injury over time. Judicious fluid resuscitation may not only be useful in dampening the possible systemic complications associated with fluid creep (eg. compartment syndrome), but may have direct effects on the local wound bed. By further elucidating mechanisms for burn conversion, interventions may be developed.

Nanomodulators Capable of Timely Scavenging ROS for Inflammation and Prognosis Control Following Photothermal Tumor Therapy

AbstractDespite the accuracy advantages of photothermal therapy (PTT), heat stress‐initiated free radicals and damage‐activated immune cells form a malignant positive feedback cycle following light irradiation. Herein, a 2D allomelanin nanomodulator with perpendicularly oriented oligomer planes is prepared by the guidance of DNA to achieve timely scavenging of reactive oxygen species (ROS) for inflammation and prognosis control following PTT. A large exposure degree of phenol groups and the effective transfer of delocalized electrons result in ultra‐fast redox reactions that can be boosted by a self‐amplifying process through structure disintegration. Compared with conventional photothermal agents, the nanodisks reduce the accumulation of ROS during PTT by 25‐fold, downregulate the proinflammatory factors, and adjust inflammation levels to baseline. Thereby, successful modulation of M2‐type macrophages in paratumor tissues significantly prevents burn wound progression and accelerates tissue repair, while well‐controlled neutrophil extracellular traps and largely recruited CD4+/CD8+ T cells (1.6–3.2‐fold) in the ablation site suppress the relapse of distant tumors. The study provides a useful inspiration on rationally modulating redox active nanostructures to address prognosis issues following PTT.

Mitochondrial dysfunction and mitophagy: crucial players in burn trauma and wound healing.

Burn injuries are a significant cause of death worldwide, leading to systemic inflammation, multiple organ failure and sepsis. The progression of burn injury is explicitly correlated with mitochondrial homeostasis, which is disrupted by the hyperinflammation induced by burn injury, leading to mitochondrial dysfunction and cell death. Mitophagy plays a crucial role in maintaining cellular homeostasis by selectively removing damaged mitochondria. A growing body of evidence from various disease models suggest that pharmacological interventions targeting mitophagy could be a promising therapeutic strategy. Recent studies have shown that mitophagy plays a crucial role in wound healing and burn injury. Furthermore, chemicals targeting mitophagy have also been shown to improve wound recovery, highlighting the potential for novel therapeutic strategies based on an in-depth exploration of the molecular mechanisms regulating mitophagy and its association with skin wound healing.

Cedrus deodara: In Vivo Investigation of Burn Wound Healing Properties.

Cedrus deodara (Roxb. Ex Lamb.) G. Don possesses various biological activities, which have been documented in modern and traditional medicine. In this study, burn wound healing activity of the methanol extract of C. deodara wood was evaluated via a burn wound model in Wistar rats. The methanol extract of C. deodara was evaluated for the contents of phenolic compounds, flavonoids, and tannins. Also, its antioxidant activity was determined using the DPPH assay. Then, a topical ointment containing the methanol extract of C. deodara (10%) was used to evaluate the healing effects on a model of second-degree thermal burn in 4 groups of 7 rats within 21 days. In this respect, average wound surface area, wound closure, and various histological features were examined. Our findings revealed that the wounds treated with the methanol extract of C. deodara showed higher wound contraction (33.6, 87.1, and 93.4% on days 7, 14, and 21, respectively) compared with the positive control (27.6, 80.7, and 88.3% on days 7, 14, and 21, respectively) and the negative control (20.1, 77.9, and 80.2% on days 7, 14, and 21, respectively). According to the results from epitheliogenesis score, the number of inflammatory cells, neovascularization, and collagen density, good burn wound healing activity of the methanol extract of C. deodarawas demonstrated. Using the methanol extract of C. deodara in an ointment formulation can be developed to prevent or reduce burn injury progression.

The Immune and Regenerative Response to Burn Injury.

Burn are diverse and complex injuries that not only have local effects but also serious systemic consequences through severe and prolonged inflammatory response. They are caused by heat, electricity, friction, chemicals, or radiation and are commonly divided into superficial, superficial partial-, deep partial- and full-thickness injuries. The severity of the burn depends mainly on the size and depth of the injury but also on location, age, and underlying systemic diseases. A prolonged and strong immune response makes major burns even worse by causing multiple systemic effects including damage to the heart, lungs, blood vessels, kidneys, and other organs. Burns that do not require surgical excision, superficial and superficial partial-thickness, follow the known progression of wound healing (inflammation, proliferation, remodeling), whilst deep partial- and full thickness injuries requiring excision and grafting do not. For these burns, intervention is required for optimal coverage, function, and cosmesis. Annually millions of people worldwide suffer from burns associated with high morbidity and mortality. Fortunately, over the past decades, burn care has significantly improved. The improvement in understanding the pathophysiology of burn injury and burn wound progression has led to developments in skin grafting, fluid resuscitation, infection control and nutrition This review article focuses on the immune and regenerative responses following burn injury. In the Introduction, we describe the epidemiology of burns and burn pathophysiology. The focus of the following chapter is on systemic responses to burn injury. Next, we define the immune response to burns introducing all the different cell types involved. Subsequently, we discuss the regenerative cell response to burns as well as some of the emerging novel treatments in the battle against burns.

Evaluation of Topical Off-The-Shelf Therapies to Improve Prolonged Field Care of Burn-Injured Service Members.

Burns are common injuries on the battlefield. Given austere environments, surgical debridement of injured service members is often not feasible in these settings. Delays in surgical debridement create a risk of infection and deranged healing for burn patients. As such, this study attempts to identify the best commercially available off-the-shelf (OTS) therapies with field-deployable potential to improve prolonged field care (PFC) of burn-injured soldiers. Deep partial-thickness (DPT) burns (25 cm2) were created on the dorsum of 5 anesthetized pigs utilizing a thermocouple burn device at 100°C for 15 seconds. Nonsurgical debridement was done 1-hour after burn creation using sterile saline water and gauze to remove excess eschar tissue. Animals were then randomized into 5 experimental groups, and OTS therapies were applied to 6 of the 12 created DPT burns. The remaining 6 burns were treated with 1% silver sulfadiazine cream (Ascend Laboratories, LLC, Parsippany, NJ) as the PFC standard of care (SOC) controls. The 5 randomized OTS therapies were: irradiated sterile human skin allograft (IHS), biodegradable temporizing matrix (BTM), polylactic acid skin substitute, hyaluronic acid ester matrix (HAM), and decellularized fish skin graft (FSG). Wounds were serially assessed on post-burn days 3, 7, 14, 21, and 28. Assessments were conducted using a combination of photographs, histology, and quantitative bacteriology. Endpoints included burn wound progression, re-epithelialization, wound contraction, scar elevation index, and colony-forming units (CFU). The analysis demonstrated that by day 3, the FSG prevented burn wound progression the most efficiently. In terms of wound healing, the results showed re-epithelialization percentages close to 100% by day 28 for all treatment groups. No statically significant differences were observed. Quality of healing analyses demonstrated that the BTM-treated wounds had contracted less and the difference to the IHS-treated wounds was statistically significant (P < .05). As regards to antimicrobial properties, the CFU results showed no statistically significant differences between the OTS therapies and the SOC on days 3, 7, and 14. The impact of Food and Drug Administration-approved OTS therapies was compared to the current PFC SOC for the treatment of DPT burns in a porcine model. Several topical options exist for the management of burns prior to definitive treatment in the operating room and warrant further evaluation. These therapies are actively used on civilian burn counterparts and have far-forward, field-deployable potential for use at the point of injury so that injured service members may not need evacuation to higher roles of care and combat power may be preserved. Our results demonstrated that all the studied OTS therapies performed well when compared to the SOC in terms of burn wound progression, wound healing, quality of healing, and quantitative bacteriology.

615 Evaluation of Topical Off-The-Shelf Therapies to Improve Burn Wound Healing During Prolonged Field Care

IntroductionBurns are common injuries in the battlefield. Given austere environments, prolonged field care (PFC) is often necessary. Delays in surgical debridement create a risk of infection and deranged healing for burn patients. As such, this study attempts to identify the best commercially available off-the-shelf (OTS) dressings with field-deployable potential.MethodsDeep-partial thickness burns (1" diameter) were created on the dorsum of 3 anesthetized pigs utilizing a thermocoupled burn device at 100°C for 15s. Non-surgical debridement was done 1-h post-burn creation and either an OTS dressing or standard-of-care (SOC) treatment (Silver Sulfadiazine) was applied to the wound in order to simulate a PFC environment. OTS dressings were randomized and included irradiated sterile human skin allograft (ISHSA), alloplastic absorbable skin substitute (AASS), and synthetic polyurethane dermal matrix (SPDM). Wounds were serially assessed on post-burn days 3, 7, 14, 21, and 28. Assessments were conducted using a combination of photographs, histology, and quantitative bacteriology. Endpoints included burn wound progression, re-epithelialization, wound contraction, scar elevation index (SEI), and colony forming units (CFU).ResultsNo statistically significant differences in burn wound progression were seen on days 3 and 7 for the ISHSA or SPDM and the SOC. The differences between the AASS and the SOC were statistically significant on both days (p≤0.05). Day 21 re-epithelialization results for the ISHSA, AASS, SPDM and SOC treated wounds were 30%, 85%, 95%, and 78% re-epithelialized, respectively. The difference between the AASS and the SOC was statistically significant (p≤0.05). Results showed that by day 28, wound contraction for the ISHSA, AASS, SPDM and SOC treated wounds were 65%, 80%, 82%, and 78%, respectively. No statistically significant differences in wound contraction were seen for any of the OTS dressings and the SOC. SEI showed no statistically significant difference in scar hypertrophy between the OTS dressings and the SOC on day 28. CFU results showed no statistically significant differences between the OTS dressings and the SOC on days 3 and 7.ConclusionsThree OTS dressings were compared to the SOC for use in the PFC setting. Generally, all the dressings performed well when compared to the SOC in terms of burn wound progression, re-epithelialization, wound contraction, SEI, and CFU. Although significant differences in burn progression and re-epithelialization for burns treated with AASS were seen. In the future, we hope to continue to discover and test various OTS dressings to determine their appropriateness for use in the PFC setting.

47 Successful Prevention of Secondary Burn Progressions Using Topical Tacrolimus and Infliximab Hydrogel

IntroductionThe pathophysiology of partial- to full-thickness burn wound conversion remains poorly understood. Recent studies have demonstrated that an altered inflammatory response may play be implicated in this secondary conversion to deeper wounds. Therefore, reduction in early inflammation may decrease burn severity and morbidity.Specifically, TNF-ɑ has been shown to detrimentally affect the healing process after injury through a variety of mechanisms. We hypothesized that microcapillary alginate hydrogel loaded with immunosuppressive medications applied to partial-thickness burns would reduce inflammation and prevent further progression to full-thickness burns.The purpose of this study was to determine whether topical application of infliximab or tacrolimus could decrease burn wound depth.MethodsAssembly of the microfluidic hydrogels was achieved by embedding microfibers within a hydrogel scaffold composed of an alginate blend. The treatment cohorts received either (1) infliximab loaded hydrogel or (2) tacrolimus skin ointment covered by hydrogel. The control cohort only received an occlusive dressing.There were 12 young (2-4 months) and 12 old ( >16 months) mice, which were separated into treatment and control cohorts. All mice were anesthetized and given partial thickness burns by a validated scalding protocol. Mice were euthanized on post-burn day 3, and skin samples were taken. Burn depth was evaluated using Vimentin immunostaining.ResultsIn young mice, infliximab hydrogel (p=.002) and tacrolimus hydrogel (p=.002) significantly decreased burn depth compared to controls. In old mice, infliximab hydrogel (p=.005) and tacrolimus hydrogel (p< .001) significantly decreased burn depth compared to controls.In young mice, infliximab and tacrolimus were similarly efficacious (p > .05). In old mice, tacrolimus significantly decreased burn depth compared to infliximab (p=.002).In controls, old mice had deeper burn wound progression than young mice (p< .001). Similarly, in those treated with infliximab, old mice had deeper burn wound progression than young mice (p=.002). Interestingly, tacrolimus was able to decrease burn wound depth in old mice such that their burn wound thickness was similar to young mice (p >.05).ConclusionsApplication of a novel microcapillary alginate hydrogel infused with infliximab or topical tacrolimus reduced partial- to full-thickness burn wound conversion in mice. Application of immunosuppressive dressings may be a promising avenue for further clinical investigation to reduce morbidity and mortality associated with burn injuries.

613 Evaluation of Non-Euphoric Phytocannabinoid Elixir 14 (NEPE-14) Application in Deep Partial-Thickness Burn Wounds

IntroductionCombat-related burn wounds can be caused by exposure to a wide variety of agents including heat, electricity, radiation, chemicals, and friction. Early intervention can decrease injury severity by preventing excess inflammation and improve long term healing outcomes. In recent years, numerous studies have demonstrated that cannabinoids can trigger anti-inflammatory responses and promote wound closure. This study investigates whether a proprietary, non-euphoric, topical cannabinoid formulation (NEPE-14) facilitates burn wound healing when compared with Silverlon®, the military standard of care for burns incurred while in the field.MethodsForty-eight deep-partial thickness burns were created on the dorsum of four anesthetized swine (Sus scrofa domestica) using a thermocoupled burn device at 100°C. One hour following burn, biopsies from each site were collected and either NEPE-14, NEPE-14 Vehicle Control, Silverlon®, or dry gauze was placed on the wound. Wounds were assessed on post-burn days (PBD) 3, 7 and 14. Assessments consisted of digital photographs, Laser-Speckle imagery (blood perfusion), FLIR imagery, MolecuLight® imagery and biopsies for histology and immunohistochemistry.ResultsBy PBD 14, no significant differences in re-epithelialization or contraction were observed between any of the tested treatment groups. Silverlon® had the highest percent re-epithelialization with 42%, and the Vehicle control has the lowest percent re-epithelialization with 28 %. Both NEPE-14 and dry gauze performed intermediately with 29% and 34% re-epithelialization, respectively. On PBD 14, the wounds of the NEPE-14 treated wounds contracted 8%, the vehicle control 7%, Silverlon® treated wounds 10%, and gauze treated wounds showed 9% contraction compared with the original wound area. Blood perfusion at PBD 14 indicated that NEPE-14 treated wounds had the lowest amount of observed blood flow and the gauze treated wounds contained the highest amount of observed blood flow. However, no statistically significant differences were observed.ConclusionsNo statistically significant results were seen between treatment groups for contraction, re-epithelialization, or blood perfusion. Although not significant, blood perfusion results indicate that NEPE-14 treatment had the lowest amount of blood flow, which can be seen as an indicator of healthy underlying tissue and a wound re-epithelializing. At PBD 14, all treatment groups had slightly contracted after increasing in wound area on PBD 3 and 7, which is a pattern seen in similar burn injury studies. We are currently awaiting histological analysis to strengthen our re-epithelialization results and evaluate burn wound progression.

Severity of thermal burn injury is associated with systemic neutrophil activation

Burn injuries elicit a unique and dynamic stress response which can lead to burn injury progression. Though neutrophils represent crucial players in the burn-induced immunological events, the dynamic secretion pattern and systemic levels of neutrophil-derived factors have not been investigated in detail so far. Serum levels of neutrophil elastase (NE), myeloperoxidase (MPO), citrullinated histone H3 (CitH3), and complement factor C3a were quantified in burn victims over 4 weeks post injury. Furthermore, the potential association with mortality, degree of burn injury, and inhalation trauma was evaluated. In addition, leukocyte, platelet, neutrophil, and lymphocyte counts were assessed. Lastly, we analyzed the association of neutrophil-derived factors with clinical severity scoring systems. Serum levels of NE, MPO, CitH3, and C3a were remarkably elevated in burn victims compared to healthy controls. Leukocyte and neutrophil counts were significantly increased on admission day and day 1, while relative lymphocytes were decreased in the first 7 days post burn trauma. Though neutrophil-derived factors did not predict mortality, patients suffering from 3rd degree burn injuries displayed increased CitH3 and NE levels. Accordingly, CitH3 and NE were elevated in cases with higher abbreviated burn severity indices (ABSI). Taken together, our data suggest a role for neutrophil activation and NETosis in burn injuries and burn injury progression. Targeting exacerbated neutrophil activation might represent a new therapeutic option for severe cases of burn injury.

Senescence in a cell culture model for burn wounds

Thermal injuries cause severe damage on the cellular and tissue level and are considered especially challenging in the clinical routine. Complex interactions of different cell types and pathways dictate the formation of burn wounds. Thus, complications like burn wound progression, where so far viable tissue becomes necrotic and the size and depth of the wound increases, are difficult to explain, mainly due to the lack of simple model systems. We tested the behavior of human fibroblasts after heat treatment. A prominent response of the cells is to activate the heat shock response (HSR), which is one of the primary emergency mechanisms of the cell to proteotoxic stress factors such as heat. However, after a powerful but not lethal heat shock we observed a delayed activation of the HSR. Extending this model system, we further investigated these static cells and observed the emergence of senescent cells. In particular, the cells became β-galactosidase positive, increased p16 levels and developed a senescence-associated secretory phenotype (SASP). The secretion of cytokines like IL-6 is reminiscent of burn wounds and generates a bystander effect in so far non-senescent cells. In agreement with burn wounds, a wave of cytokine secretion enhanced by invading immune cells could explain complications like burn wound progression. A simple cell culture model can thus be applied for the analysis of highly complex conditions in human tissues.

Dermal Nanoemulsion Treatment Reduces Burn Wound Conversion and Improves Skin Healing in a Porcine Model of Thermal Burn Injury.

Burn wound progression is an inflammation-driven process where an initial partial-thickness thermal burn wound can evolve over time to a full-thickness injury. We have developed an oil-in-water nanoemulsion formulation (NB-201) containing benzalkonium chloride for use in burn wounds that is antimicrobial and potentially inhibits burn wound progression. We used a porcine burn injury model to evaluate the effect of topical nanoemulsion treatment on burn wound conversion and healing. Anesthetized swine received thermal burn wounds using a 25-cm2 surface area copper bar heated to 80°C. Three different concentrations of NB-201 (10, 20, or 40% nanoemulsion), silver sulfadiazine cream, or saline were applied to burned skin immediately after injury and on days 1, 2, 4, 7, 10, 14, and 18 postinjury. Digital images and skin biopsies were taken at each dressing change. Skin biopsy samples were stained for histological evaluation and graded. Skin tissue samples were also assayed for mediators of inflammation. Dermal treatment with NB-201 diminished thermal burn wound conversion to a full-thickness injury as determined by both histological and visual evaluation. Comparison of epithelial restoration on day 21 showed that 77.8% of the nanoemulsion-treated wounds had an epidermal injury score of 0 compared to 16.7% of the silver sulfadiazine-treated burns (P = .01). Silver sulfadiazine cream- and saline-treated wounds (controls) converted to full-thickness burns by day 4. Histological evaluation revealed reduced inflammation and evidence of skin injury in NB-201-treated sites compared to control wounds. The nanoemulsion-treated wounds often healed with complete regrowth of epithelium and no loss of hair follicles (NB-201: 4.8 ± 2.1, saline: 0 ± 0, silver sulfadiazine: 0 ± 0 hair follicles per 4-mm biopsy section, P < .05). Production of inflammatory mediators and sequestration of neutrophils were also inhibited by NB-201. Topically applied NB-201 prevented the progression of a partial-thickness burn wound to full-thickness injury and was associated with a concurrent decrease in dermal inflammation.

Thermal injury induces early blood vessel occlusion in a porcine model of brass comb burn

Burn wound progression is an important determinant of patient morbidity and mortality after injury. In this study, we used the brass comb contact burn to determine burn wound vertical injury progression with a focus on blood vessel occlusion and endothelial cell death. Class A 3-month-old Yorkshire pigs received a brass comb contact burn. Burn wounds were sampled at 0, 30 min, 1, 2, 4, and 24 h. Hematoxylin Phloxin Saffron staining and vimentin immunostaining were performed to determine the depth of blood vessel occlusion and endothelial cell death, respectively. The depth of blood vessel occlusion increased by 30 min (p < 0.005) and peaked by 1 to 4 h (p > 0.05). The depth of endothelial cell death risen to a plateau at 30 min (p < 0.005) to 2 h and then peaked at 24 h (p < 0.03). We observed a progression of blood vessel occlusion and vascular endothelial cell death from the middle of the dermis to the hypodermis within 2 h to 4 h after the initial injury, namely a progression from a second-degree (partial thickness) to third-degree (full thickness) burn. These data suggest that therapeutic interventions during this time window may provide a better outcome by reducing or preventing vertical progression of blood vascular occlusion or endothelial cell death.

Erythrocyte Aggregation in Hyperthermic Hypoxic Conditions Significantly Related to Self‐identified Race

Our purpose was to identify the kinetics of erythrocyte (RBC) reversible aggregation (Agg) during stop flow (SF) experiments as a function of temperature and O2 for RBC from healthy subjects self-identified as Black (B, n=8), Hispanic (H, 4) or Caucasian (C, 4) (48+/- 9 y). Whole blood (EDTA, BioIVT, Westbury, NY), vendor verified to be viral free, and used within 1 week of donation, was centrifuged and the platelet poor plasma (PPP) was recovered. All RBCs were resuspended in autologous PPP, and incubated at specified temperatures (37, 41, 45, 49 C) and O2 (0, 5, 10%, saturating). Flow was initiated in a microchannel system at 0.1-0.2 Re, then stopped while recording the entire microchannel width. The greyscale range of the images showed a significant Fahraeus effect with flow (cell free layer at wall). With SF, as Agg proceeded, the aggregates accumulated within the centerline of the microchannel, increasing the variability of the greyscale range from white at the microchannel wall to black in the centerline. The change in variability indicated kinetics of Agg that occurred over 3 min of recording. The primary data of greyscale vs time (custom software) was fit to a sigmoid (dose response) curve, where the fitted EC50 was the T1/2 for Agg and with the fitted slope (p) indicated the kinetics of Agg. At 37 C the T1/2 was 93 s in 0% O2, 75 s with venous (5%) or arterial (10%) and was not different by group. As temperature increased, the T1/2 became significantly faster in blood from B or H (to 65 s), but not C. Correlation between temperature and the fitted T1/2 were significant in B (slope, R2; -2.9, 0.92), H (-2.7, 0.97) and C (-1.1, 0.6), but the F-test on the slope was significant for B (p=0.02) and H (0.04) not C (0.6). This coincided with a significantly steeper p for B and H. At venous, arterial or saturating O2, the effect of increasing temperature to decrease the T1/2 was much less pronounced, and not different between groups. This data shows that in only hypoxic conditions, with temperatures of 41 C (105.8 F) or higher, RBC from self-identified B or H subjects aggregates more readily than C. These results pertain to our focus of microvascular compromise in thermal burn injury progression, but also clinical conditions of localized cautery to control bleeding, high fevers or malignant hyperthermia.

ASMq protects against early burn wound progression in rats by alleviating oxidative stress and secondary mitochondria‑associated apoptosis via the Erk/p90RSK/Bad pathway.

Burn wounds present an evolutionary progression, in which the initial wound tissue deepens and expands following thermal injury. Progressive tissue damage in the zone of stasis may worsen burn injury, which is associated with oxidative stress and secondary apoptosis, and worsen the prognosis of patients with burn wounds. The mitochondrial apoptotic pathway is involved in receiving oxidative signals and regulating tissue apoptosis. Previously, Abnormal Savda Munziq (ASMq), a natural compound of traditional Uyghur Medicine, which includes ten types of herb, has been reported to exhibit a number of effects, including anti-inflammatory, antioxidative and anti-apoptotic activities. The present study demonstrated that ASMq protected against early burn wound progression following thermal injury in rats; this effect may be mediated by its ability to attenuate oxidative stress-induced mitochondria-associated apoptosis. The present study may provide a novel therapeutic method to prevent early burn wound progression following burn injury.

The Effects of Systemic Use of Epigallocatechin Gallate in Thermal Injury Progression

The burn wound progression is a complex process caused by inadequate tissue perfusion, free radical damage, and altered cytokine levels in burn patients. Epigallocatechin gallate (EGCG) has vasodilator, antioxidant, and skin protective properties. In this study, we investigated the effects of epigallocatechin gallate (EGCG) on burn wounds. Nine male Wistar albino rats were randomly assigned to the control group and received no burn insult. The other rats were exposed to thermal injury with a brass comb and randomly divided into two groups: burn with no further treatment (group 1, n:3) and burn with enteral EGCG treatment (group 2, n:3). The administration of EGCG was initiated 5 min after the burn procedure at a dose of 1 mg/kg by gastric lavage and repeated for 3 days at an infusion rate of 1 mg/kg/day. Skin sections were stained with Hematoxylin-Eosin and Masson’s trichrome for histochemistry. The primary antibodies used for immunohistochemistry included rabbit anti-4-hydroxynonenal (protein-HNE), rabbit anti-malondialdehyde (protein-MDA, mouse monoclonal anti-acrolein (protein-ACR), rabbit anti-ALDH1A1, and rabbit anti-ALDH2. Systemic administration of EGCG after burn injury significantly ameliorated the histological alterations in burn sites, especially in the zone of stasis. The expression of reactive aldehyde products (HNE, MDA, ACR) as a result of thermal injury significantly decreased in the EGCG group. EGCG reduced reactive aldehyde products independent of ALDH1 and ALDH2 pathway and improved histological alterations with cytoprotective and antioxidant effects. Early systemic use of EGCG prevents burn wound from progressing to deep structures and limits its extension to the adjacent zones.

Locally activated mitophagy contributes to a “built-in” protection against early burn-wound progression in rats

AimsDeep burn-wounds undergo a dynamic progression in the initial or periburn area after insults, and the zone of stasis is the crucial region suffering the deterioration, considered as salvageable. Few studies explored the role of mitochondria in this process. This study is to clarify a possible “built-in” protection of mitophagy. Main methodsA classic “comb” scald rat model was established. Histological and blood-flow observation were processed based on hematoxylin-eosin staining and laser analysis. Oxidative and apoptotic status were analyzed by commercial kits. Transmission-electron microscope, immunofluorescence staining, and western blot were applied to detect the mitophagy in the zone of stasis and potential regulators. Adenovirus-based gene-silence contributed to determine the role of HIF-1α as a regulatory mediator. Key findingsWe found that burn-caused typical ischemia and histological deterioration in the zone of stasis, in parallel with increases in oxidative stress and apoptosis. Mitochondrial damage was involved in the aforementioned changes. Furthermore, we detected mitophagy in burn-wounds, which was contradictory to the burn-wound conversion. HIF-1α expression was closely related to the level of mitophagy, while BNIP3 and PARKIN are involved downstream. SignificanceWe demonstrate that burn-induced mitochondrial impairment contributes to the mobilization of injurious mechanisms in the zone of stasis and that mitophagy provides a beneficial way to protect against burn-wound progression via the elimination of damaged mitochondria. Our findings offer insights into mitochondrial quality control in burn-wound progression and suggest the novel concept that HIF-1α may be a therapeutic target due to its possible regulation on BNIP3- or PARKIN-mediated mitophagy.

Modeling Burn Progression Using Comb Burns: The Impact of Thermal Contact Duration on Model Outcomes

BackgroundBurn progression is a phenomenon that remains poorly characterized. The mechanisms of burn conversion are not completely understood, and consequently, both predictive diagnostic tools and interventions are limited. The rat comb burn model is a commonly used approach to study horizontal burn conversion. However, there is significant variability in how the model is performed. Skin contact duration, comb device heating method, comb heating duration, amount of pressure applied, the weight of the comb, and associated depth of burn are all variables that are heterogeneous in studies utilizing the model. Materials and methodsHere, contact duration was examined to determine the impact the duration of burn delivery has on the conversion of interspaces in this model. Data from multiple experiments consisting of 10, 15, 20, 30, 40, and 45 s comb burns were compiled and assessed. Burns were made using combs heated in a 100°C dry bath and then monitored for 2 d. Interspace viability was assessed by digital and laser doppler imaging and biopsy procurement. ResultsLaser Doppler Imaging and viable interspace measurements showed that as burn duration increased, the percentage of the viable interspace and interspace perfusion decreased. Additionally, a contact time of 30 s or greater was required to result in 100% interspace conversion. ConclusionsThese results demonstrate a need to better characterize and potentially standardize the rat comb burn model to reduce variation and maintain it as a valuable tool for controlled studies of the pathophysiology of burn wound progression.