A standard burn model using rats

Effects of photobiomodulation therapy with red LED on inflammatory cells during the healing of skin burns

The aim of this study was to evaluate the effects of red light emitting diode (LED) photobiomodulation therapy protocol on inflammatory cells during the healing of third-degree skin burns. Fifty Wistar rats were randomly divided into control group (CTRL) (n = 25) and red group (RED) (n = 25), with subgroups (n = 5) for each time of euthanasia (7, 14, 21, 28, and 32 days). Treatment animals were daily irradiated (630 nm ± 10 nm, 300 mW, 9 J/cm² per point, 30 s, continuous emission mode) at the 4 angles of the wound (total: 36 J/cm²). After specimen removal, histological sections were stained with hematoxylin and eosin for quantitative analysis of the inflammatory infiltrate (neutrophils and lymphocytes) under light microscopy. Greater number of inflammatory cells was observed in irradiated groups when compared to CTRL at 7, 14, 21, and 28 days, but with statistically significant difference only at 14 days (p = 0.02). At 32 days, higher inflammatory cell value was observed in CTRL when compared to RED, but with no statistically significant difference (p = 0.91). The results suggest that red LED, according to the protocol used, modulates the number of inflammatory cells in the early stages of the healing of third-degree skin burns. Nevertheless, this low-intensity light therapy may not, be efficient in reducing the number of neutrophils and lymphocytes in advanced stages of the repair process of skin burns. Further studies with other therapy protocols are needed to assess the effects of this type of light on the inflammatory response of skin burns.

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.

Therapeutic and Ameliorative Effects of Active Compounds of Combretum molle in the Treatment and Relief from Wounds in a Diabetes Mellitus Experimental Model

Foot ulcers are one of the leading causes of severe and high mortality in diabetics. It is known that wound healing in diabetics is a very complicated process due to the direct severe effect of diabetes mellitus on blood vessels, causing difficulty in wound healing. Many methods of treatment have recently been employed for novel dressings for the promotion of tissue regeneration and rapid wound closure. Combretum molle is composed of chemical compounds, such as lignin, gallic acid, and ellagic acid. Twenty male rats that were 4 months of age were divided into a I-a diabetic foot ulcer group as the control group and a II-a diabetic group (wound + Combretum molle). This study investigated the antioxidant and excellent healing effects of the extract of Combretum molle in repairing skin damaged by diabetes. This was confirmed by elevated antioxidant enzymes in the animals’ tissues in diabetic rats treated with this extract. The recovery of the alterations in the skin layers led to great improvements, which proved the Combretum molle’s promising capacity for wound healing in diabetics with wounds that mimic diabetic foot ulcers. This treatment can be considered a promising opportunity for patients with severe foot ulcers and may open the door to more discoveries about this plant’s medical capabilities.

Effect of PDGF-B Gene-Activated Acellular Matrix and Mesenchymal Stem Cell Transplantation on Full Thickness Skin Burn Wound in Rat Model

BACKGROUND

Full thickness burn wounds are lack of angiogenesis, cell migration, epithelialisation and finally scar tissue formation. Tissue engineered composite graft can provide sustained release of growth factor and promote the wound healing by cell migration, early angiogenesis and proliferation of extracellular matrix and wound remodeling. The objective of this study was to evaluate the gene embedded (pDNA-platelet-derived growth factor, PDGF-B) porcine acellular urinary bladder matrix with transfected mesenchymal stem cells (rBMSC) on healing of full thickness burn wound in rat model.

METHODS

Full thickness burn wound of 2 × 2 cm size was created in dorsum of rat model under general anesthesia. Burn wounds were treated with silver sulfadiazine; porcine acellular urinary bladder matrix (PAUBM); PAUBM transfected with pDNA-PDGF-B; PAUBM seeded with rBMSC; PAUBM seeded with rBMSC transfected with pDNA-PDGF-B in groups A, B, C, D and E respectively. The wound healing was assessed based on clinical, macroscopically, immunologically, histopathological and RT-qPCR parameters.

RESULTS

Wound was significantly healed in group E and group D with early extracellular matrix deposition, enhanced granulation tissue formation and early angiogenesis compared to all other groups. The immunologic response against porcine acellular matrix showed that PDGF-B gene activated matrix along with stem cell group showed less antibody titer against acellular matrix than other groups in all intervals. PDGF gene activated matrix releasing the PDGF-B and promote the healing of full thickness burn wound with neovascularization and neo tissue formation. PDGF gene also enhances secretion of other growth factors results in PDGF mediated regenerative activities. This was confirmed in RT-qPCR at various time intervals.

CONCLUSION

Gene activated matrix encoded for PDGF-B protein transfected stem cells have been clinically proven for early acceleration of angiogenesis and tissue regeneration in burn wounds in rat models. Evaluation of PDGF-B gene-activated acellular matrix and mesenchymal stem cell in full thickness skin burn wound in rat.

Human Bone Marrow Mesenchymal Stem Cell Conditioned Medium Promotes Wound Healing in Deep Second-Degree Burns in Male Rats

Burn wound treatment is difficult and one of the most challenging problems in the clinic. Researchers have examined the applications of mesenchymal stem cells as a cell-based therapy for skin regeneration. But the role of human bone marrow mesenchymal stem cell conditioned medium (hBM-MSC-CM) in the treatment of burn injury remains unclear. This research aims at detecting whether hBM-MSC-CM can increase the wound healing of deep second-degree burns in male rats. In this study, 32 adult male rats per each time point were randomly divided into four groups: (1) control group, (2) sham group (DMEM), (3) common treatment group (CT), and (4) conditioned media group (CM). A 3 × 3 cm circular burn was created on the back of the rats. On postsurgical days 7, 15, and 28, the wound closure area of each wound was measured and then the skin samples were removed and analyzed using stereological methods. Wound closure area was significantly increased in the CM and CT groups on the 15th and the 28th day after burn injury compared to the control and DMEM groups. The stereological parameters and immunohistochemistry analysis of the wounds revealed significantly improved healing in the CM group compared to the control and other groups. It is concluded that these findings indicate that hBM-MSC-CM promotes skin wound healing by increasing cell proliferation, regulating collagen synthesis and collagen composition, and inducing angiogenesis at the injury site.

Effect of blue LED on the healing process of third-degree skin burns: clinical and histological evaluation

The aim of this study was to evaluate the effects of blue light-emitting diode (LED) on the healing process of third-degree skin burns in rats through clinical and histological parameters. Forty male Wistar rats were divided into two groups: control (CTR) (n = 20) and blue LED (BLUE) (n = 20), with subgroups (n = 5) for each time of euthanasia (7, 14, 21, and 28 days). LED (470 nm, 1 W, 12.5 J/cm² per point, 28 s) was applied at four points of the wound (total, 50 J/cm²). Feed intake was measured every other day. It was observed that there were no statistically significant differences in the Wound Retention Index (WRI) of the BLUE group in relation to CTR group (p > 0.05) at the evaluation times. After 14, 21, and 28 days, it was observed that the animals in the BLUE group consumed more feed than animals in the CTR group (p < 0.05). At 7 days, there was a statistically significant increase in the angiogenic index (AI) in BLUE (median: 6.2) when compared to CTR (median: 2.4) (p = 0.01) and all animals in BLUE had already started re-epithelialization. This study suggests that blue LED, at the dosimetry used, positively contributed in important and initial stages of the healing process of third-degree skin burns.

Beneficial effects of Salvia miltiorrhiza in the healing of burn wounds: an experimental study in rats

INTRODUCTION

Burn healing is a complicated process and very few treatments can positively alter its effects. The aim of this study was to investigate the effects Salvia miltiorrhiza (SM -Danshen), a traditional Chinese medicine, on burn wound healing.

MATERIAL AND METHODS

Twenty rats were included in this study and divided into two groups. 3 × 2 cm wide burn areas were created in the dorsal skin of all the animals with thermal contact. Intraoral 1 ml/day saline and 1 g/kg/day SM were given in control and experiment groups, respectively. Fourteen days following the burn injury burn zones were evaluated with indocyanine green-SPY imaging device, and multiple samples were collected for histopathological evaluation. Standard photographs were taken for the evaluation of necrotic skin areas.

RESULTS

Neovascularization was increased in the SM group when compared with the control group (p = 0.0406). SPY studies revealed a meaningful increase in the tissue perfusion in the SM group (p = 0.0286). The average amount of necrotic area in the control and experiment group on the postoperative 14th day was 71.6% (±16.51) and 42.5% (±10.64) respectively (p = 0.0002).

CONCLUSION

Our study shows that SM can decrease the amount of necrosis in burn wounds by increasing tissue perfusion and neovascularization.

Alternative animal model for studies of total skin thickness burns

PURPOSE

To present an alternative experimental model of third degree burn of easy reproducibility.

METHODS

Eighteen male Wister rats were randomly divided into three groups, 6 of which were allocated to each group. A soldering iron coupled to an aluminum plate was used to produce burn, at a temperature of 150ºC, with different exposure times per group. Group 5 (G5) animals were burned at 150°C with exposure time of 5 seconds; Group 10 (G10) the animals were burned at 150°C with exposure time of 10 seconds and group 15 (G15) the animals were burned at 150°C with exposure time of 15 seconds.

RESULTS

Histopathological analyzes showed that all three groups had similar morphological characteristics, with total thickness involvement.

CONCLUSION

The technique is effective to reproduce a third degree burn and suggests the temperature of 150ºC with 5 seconds of exposure in order to minimize the risks to the animals.

Design and Testing of an Experimental Steam-Induced Burn Model in Rats

Background

Most of the current models for experimental burns pose difficulties in ensuring consistency and standardization.

Aim of Study

We aimed to develop an automated, reproducible technique for experimental burns using steam-based heat transfer.

Methods

The system developed for steam exposure was based on a novel, integrated, computer-controlled design. Three groups of rats were exposed to steam for 1, 3, and 7 seconds. The lesions were evaluated after 20 minutes, 48 hours, and 72 hours after burn induction.

Results

One-second steam application produced a superficial second-degree burn; three-second application induced deep second-degree burn; and seven-second application led to a third-degree burn.

Conclusion

The high level of automation of our integrated, computer-controlled system makes the difference between our system and other models, by ensuring the control of the duration of exposure, temperature, and pressure and eliminating as many potential human generated errors as possible. The automated system can accurately reproduce specific types of burns, according to histological assessment. This model could generate the reproducible data needed in the study of burn pathology and in order to assess new treatments.

Use of platelet-rich plasma in deep second- and third-degree burns

Unfortunately burns are a common occurrence, leading to scarring or death. Platelet-rich plasma (PRP) contains many growth factors that can accelerate wound healing. We analyzed the use of PRP in deep second-degree (dSD), deep second-degree associated with diabetes mellitus (dSDD), and third-degree (TD) burns in rats. Sixty syngeneic rats divided into three groups (dSD, dSDD, and TD) were burned, half receiving topical PRP and half being used as control; 10 additional rats per group were used for PRP preparation. On day 21, the animals were sacrificed and skin biopsies were collected. dSD and dSDD wounds treated with PRP showed faster wound closure, reduction in CD31-, CD68-, CD163-, MPO-, and in TGF-β-positive cells, and an increase in MMP2-positive cells. The neo-epidermis was thinner in the control of both the dSD and dSDD groups and granulation tissue was less reduced in the control of both the dSDD and TD groups. These results indicate that PRP can accelerate the healing process in dSD and dSDD, but not in TD burns.

Healing activity of Casearia sylvestris Sw. in second-degree scald burns in rodents

BACKGROUND

Every year thousands of people are victims of burns, mainly scald burns. Many of these victims have small size wounds and superficial partial thickness and do not seek specialized medical care. As in Brazil Casearia sylvestris Sw., popularly known as guaçatonga is widely used for its analgesic, antiseptic and anti-inflammatory activities, this study sought to evaluate the effects of its hydroalcoholic extract in healing process of burns injuries.

METHODS

The obtained extract was validated applying a thin layer chromatography and sophisticated validation method using Bothrops jararacussu snake venom that is necrotic and inflammatory, and by which guaçatonga extract was able to neutralize the irreversible neuromuscular blockade induced by the venom. After induction of the scald injury, the animals were treated daily with saline solution spray; spray containing extract; biofilm; or biofilm impregnated with extract.

RESULTS

Significant differences were observed between the four groups studied considering: extension of the healing area, neovascularization, fibroblast proliferation, and epithelialization.

CONCLUSION

The anti-inflammatory and bactericidal effects of C. sylvestris Sw. suggests a potential therapeutic benefit in the treatment of inflammatory conditions in second-degree scald burn injuries, as well as, counteracting against the in vitro paralysis induced by B. jararacussu venom.

Niosomally encapsulated silver sulfadiazine gel for burn treatment

Silver sulfadiazine (SSD) is the antibacterial of choice for the treatment of burn. The current marketed formulation of SSD is 1% w/w water soluble cream, which requires frequent applications, which is very painful to patients. Niosomes were prepared by a thin film hydration method. The in vitro antimicrobial efficiency of niosomal SSD (18 ± 0.5 mm) was as good as that of marketed cream (17 ± 0.5 mm) against Staphylococcus aureus even when used in half the concentration (0.5%) of marketed cream (1%). Further SSD (0.5% w/w) niosomal gel was prepared using 1.6% carbopol 934. It was evident through in vitro permeation studies that SSD release was considerably retarded from both niosomes and niosomal gel in comparison with marketed cream thereby decreasing the dosing frequency. In-vivo study demonstrated that a niosomal gel containing 0.5% w/w SSD was more effective in burn wound healing compared to 1% w/w marketed cream even when applied once a day.

An optimized animal model for partial and total skin thickness burns studies

PURPOSE

Development of an improved animal model for studying skin burns in rats.

METHODS

Twenty-four male Wistar rats were randomly assigned to four groups (n=6): G1-Control, G2- T100°C, G3-T150°C and G4-T200°C. Two 10 x 10 mm squares were outlined with a sterile surgical marker on each side and along the vertebral column using a prepared template positioned between the anterior and posterior limbs. G2-G4 rats were subjected to 100°C, 150°C and 200ºC thermal burns, respectively. G1 rats served as controls. Burns were inflicted by applying a copper plate connected to an electronic temperature controlling device to the dorsal skin of anesthetized rats. Four burns were produced on each animal (total area: 4 cm²/animal) leaving about 1 cm of undamaged skin between burn areas. Analgesia was administered during 24 h after burn injury by adding 30 mg codeine phosphate hemihydrate to 500 ml tap water.

RESULTS

The application of 100°C and 150ºC resulted in partial thickness skin burns with central reepithelialization of the burned area only at 100°C. In G4 group the whole thickness of the skin was injured without central reepithelialization. However, there was marginal reepithelialization in all groups.

CONCLUSION

The model studied is inexpensive and easily reproducible, enabling the achievement of controlled burns with partial or total impairment of the skin in experimental animals.

Development of animal model for studying deep second-degree thermal burns

Thermal lesions were produced in 12 male Wistar rats, positioning a massive aluminum bar 10 mm in diameter (51 g), preheated to 99°C ± 2°C/10 min. on the back of each animal for 15 sec. After 7, 14, 21, and 28 days, animals were euthanized. The edema intensity was mild, with no bubble and formation of a thick and dry crust from the 3rd day. The percentage of tissue shrinkage at 28 days was 66.67 ± 1.66%. There was no sign of infection, bleeding, or secretion. Within 28 days reepithelialization was incomplete, with fibroblastic proliferation and moderate fibrosis and presence of modeled dense collagen fibers. It is concluded that the model established is applicable in obtaining deep second-degree thermal burns in order to evaluate the healing action of therapeutic agents of topical use.

Effects of hyperbaric oxygen therapy on fibrovascular ingrowth in porous polyethylene blocks implanted under burn scar tissue: An experimental study

Effects of hyperbaric oxygen (HBO) therapy on biointegration of porous polyethylene (PP) implanted beneath dorsal burn scar and normal skin were experimentally examined in Sprague-Dawley rats. In Group One (n=20), daily HBO treatments were given after the implantation of PP material under dorsal burn scar, whereas, in Group Two (n=20) no treatment was given following the same surgical procedure. In Group Three (n=20), PP was placed under dorsal normal skin and subsequently HBO therapy protocol was applied while Group Four (n=20) stayed without HBO treatment after the implantation. One, 2, 3 and 4 weeks after the implantations, sections were respectively taken from five rats from each group. Biointegration process and effects of HBO therapy were evaluated microscopically and the ratio of fibrovascular ingrowth (FVI) was determined for each rat. The results showed significantly superior FVI in Group One compared to Group Two and again FVI into PP under normal skin treated with HBO revealed better results against Group Four (p<0.05). Well-vascularized capsule formation and tissue integration was delayed both in Group Two and in Group Three in the first 3 weeks. In conclusion, HBO therapy enhances biointegration of PP in hypoxic burn scar areas via improving collagen synthesis and neovascularization; otherwise, it apparently delays tissue ingrowth into porous structure implanted in normal healthy tissues.

Ketamine reduces mortality of severely burnt rats, when compared to midazolam plus fentanyl

Ketamine can provide protective effects, through its anti-inflammatory properties, as shown in animal models of septic shock and endotoxemia, and has elicited the heat-shock response (HSR) in experimental studies. The HSR has reduced the mortality after severe burns in rats. This study has tested the hypothesis that ketamine could be protective in experimental burns and that it could generate the HSR. One hundred and twenty adult male Fischer rats were randomly divided into five groups. Rats in the first group (n = 20) were sham-anesthetized. In the second group (n = 20), rats were anesthetized with ketamine and shaved. In the third group (n = 20) rats were anesthetized with midazolam plus fentanyl and shaved. In the fourth group (n = 30), rats were anesthetized with ketamine, shaved and submitted to 29% body surface third-degree burns using a brass bar. In the fifth group (n = 30), rats were anesthetized with midazolam plus fentanyl, shaved and submitted to 29% body surface third-degree burns using a brass bar. Mortality rates were measured at 1, 2, 3, 5, 7, 10, 15 and 25 days. Liver and lung samples were collected from all groups for heat-shock protein 70 (HSP70) detection. No animals died in the first, second or third group. Animals anesthetized with ketamine showed significantly decreased mortality, as compared to those anesthetized with midazolam plus fentanyl, from day 2 to day 10 (P < 0.01, Fischer's exact test) and from day 10 to day 25 (P < 0.05). HSP70 was positive in the lungs of animals from all groups, without any differences among them, and was found in none of the liver samples. In conclusion, the mortality was significantly lesser in ketamine-anesthetized burnt rats than in burnt animals anesthetized with midazolam plus fentanyl. Ketamine has not elicited the HSR in this model of experimental burns and, therefore, its protective effects were not shown to be mediated through this mechanism.