Rat an experimental model for burns: a systematic review

Photopolymerized silk fibroin gel for advanced burn wound care

The future of burn wound treatment lies in developing bioactive dressings for faster and more effective healing and regeneration. Silk fibroin (SF) hydrogels have proven regenerative abilities and are being explored as a burn wound dressing. However, unfavorable gelation conditions limit the processability and clinical application. Herein a white light-responsive photopolymerization technique was adapted for gelation via photooxidation of tyrosine. To render the gel suitable for application to irregular and non-planar burn surfaces, SF gel-incorporated dressing (SFD) was fabricated. The mild gelation conditions using white light afforded the loading of drugs for local delivery. The moisture balance ability of the dressing was confirmed by the favorable measures of swelling capacity (106 ± 1 %) and moisture retention (≈10 h). The in vitro cytocompatibility of the gel was confirmed using HaCaT cells. Finally, in vivo performance of the SFD was tested on a second-degree burn in a rodent model. The gross analysis and histological assessment revealed scarless healing in SFD-treated groups. Overall, the SFD developed in this work is shown to be a promising candidate for advanced burn wound care.

Developing a third-degree burn model of rats using the Delphi method

Animal experiments play an essential role in advances in the research and treatment of burns. Currently, researchers often rely on personal experience or the literature to complete the construction of animal disease models, which may lead to a lack of scientific rigor and a wide range of animal disease models with reference value. The purposes of this study were to establish a third-degree burn model of rats using the Delphi method to provide a reference. Two rounds of a Delphi expert consultation survey were conducted on experts (n = 13) in this study, and then the boundary value method was used to screen, modify and supplement the indicators. Next, the indicator weight was determined by dividing the boundary value, and finally, the index system of the rat model of third-degree burns was established. The statistical analysis results show that the positive coefficients of the two rounds of expert consultation are 100% and 88.67% respectively. The expert authority coefficient values were 0.73 and 0.67, respectively, and the expert coordination coefficient test was P < 0.001. According to the experts' suggestion, the third-degree burn model of rats with 8 first-degree indexes, 14 second-degree indexes and 46 third-degree indexes was finally established. According to the characteristics and quality requirements of animal models, this study constructs a rat model of third degree burns, which is expected to expressively improve the overall proficiency of burn research quality.

Effects of resveratrol topical ointment on wound healing of full-thickness cutaneous burns in albino rats

OBJECTIVE

In this study, the effects of resveratrol topical ointment on wound contraction and histopathology of full-thickness cutaneous burn wounds were evaluated.

METHOD

Adult albino rats were grouped into four equal-sized groups of 15 rats each, as follows: Group A-no wound, no treatment (control); Group B-1% silver sulphadiazine; Group C-5% resveratrol, and Group D-wound without treatment (control). A burn wound measuring 23.5mm was created on the skin at the dorsum of all rats in groups B-D after shaving. The percentage of wound contraction was measured using a digital Vernier Caliper on days 1, 3, 5, 7, 10, 14, 16, 18 and 21, post-wounding. From each group, five rats were then euthanised and tissue samples of the skin, liver and kidney were collected in 10% buffered formalin for histopathology.

RESULTS

The percentage of wound contraction was significant (p<0.05) on 7, 14 and 18 days post treatment. Histopathologically, 5% resveratrol topical ointment application resulted in a thicker epidermis with neovascularisation and an increased collagen distribution. Resveratrol topical ointment ameliorated the extent of hepatocellular and nephrotubular injuries following burn-induced hepatocellular and acute kidney injuries.

CONCLUSION

In this study, topical application of 5% resveratrol ointment appeared to enhance burn wound healing by increasing the rate of wound contraction through collagen fibre synthesis, granulation tissue formation and epithelial regeneration.

Ameliorative effect of bone marrow-derived mesenchymal stem cells on burn-induced hepatic and metabolic derangements in rats

AIMS

The current study aims to investigate the therapeutic potential of bone marrow-derived mesenchymal stem cells (MSCs) as a solo therapy in ameliorating both skin lesions and liver injury induced by cutaneous severe burn injury (SBI) in rats.

MAIN METHODS

In anesthetized male adult Wistar albino rats, 30 % total burn surface area and established hepatic injury was achieved via direct contact of each experimental animal's dorsum with heated metal rod (100 °C) for 10 s. On the next day following burn, human MSCs or mouse MSCs was administered locally around the burn site and intraperitonially (0.5 × 10⁶ cells/rat for each route) and outcomes were investigated at 4 and 14 days following burn induction.

KEY FINDINGS

Both types of MSCs significantly improved skin and liver histology, decreased liver enzymes, and ameliorated oxidative stress in hepatocytes of SBI-rats. Further, SBI-induced rises in hepatic apoptotic marker (caspase-3, Bax) and serum inflammatory markers (TNF-α, IL-1β, and IL-6) were reduced following either human or mouse MSC administration. In addition, MSCs augmented insulin receptor substrate-1, phosphorylated protein kinase-B (phospho-Akt), while alleviating serum glucose levels in SBI-rats. These previous effects persisted even at the 14-day time point.

SIGNIFICANCE

Following single administration, bone marrow-derived MSCs is capable of counteracting SBI-induced skin lesions as well as related hepatic complications, specifically via mitigating postburn hyperglycemia and hyperinflammation.

Cinnamaldehyde-Based Self-Nanoemulsion (CA-SNEDDS) Accelerates Wound Healing and Exerts Antimicrobial, Antioxidant, and Anti-Inflammatory Effects in Rats’ Skin Burn Model

Cinnamaldehyde, the main phytoconstituent of the cinnamon oil, has been reported for its potential wound healing activity, associated to its antimicrobial and anti-inflammatory effects. In this study, we are reporting on the cinnamaldehyde-based self-nanoemulsifying drug delivery system (CA-SNEDDS), which was prepared and evaluated for its antimicrobial, antioxidant, anti-inflammatory, and wound healing potential using the rat third-degree skin injury model. The parameters, i.e., skin healing, proinflammatory, and oxidative/antioxidant markers, were evaluated after 3 weeks of treatment regimens with CA-SNEDDS. Twenty rats were divided randomly into negative control (untreated), SNEDDS control, silver sulfadiazine cream positive control (SS), and CA-SNEDDS groups. An aluminum cylinder (120 °C, 10-s duration) was used to induce 3rd-degree skin burns (1-inch square diameter each) on the rat’s dorsum. At the end of the experiment, skin biopsies were collected for biochemical analysis. The significantly reduced wound size in CA-SNEDDS compared to the negative group was observed. CA-SNEDDS-treated and SS-treated groups demonstrated significantly increased antioxidant biomarkers, i.e., superoxide dismutase (SOD) and catalase (CAT), and a significant reduction in the inflammatory marker, i.e., NAP-3, compared to the negative group. Compared to SNEDDS, CA-SNEDDS exhibited a substantial antimicrobial activity against all the tested organisms at the given dosage of 20 µL/disc. Among all the tested microorganisms, MRSA and S. typhimurium were the most susceptible bacteria, with an inhibition zone diameter (IZD) of 17.0 ± 0.3 mm and 19.0 ± 0.9 mm, respectively. CA-SNEDDS also exhibited strong antifungal activity against C. albicans and A. niger, with IZD of 35.0 ± 0.5 mm and 34.0 ± 0.5 mm, respectively. MIC and MBC of CA-SNEDDS for the tested bacteria ranged from 3.125 to 6.25 µL/mL and 6.25 to 12.5 µL/mL, respectively, while the MIC and MBC for C. albicans and A. niger were 1.56 µL/mL and 3.125 µL/mL, respectively. The MBIC and MBEC of CA-SNEDDS were also very significant for the tested bacteria and ranged from 6.25 to 12.5 µL/mL and 12.5 to 25.0 µL/mL, respectively, while the MBIC and MBEC for C. albicans and A. niger were 3.125 µL/mL and 6.25 µL/mL, respectively. Thus, the results indicated that CA-SNEDDS exhibited significant wound healing properties, which appeared to be attributed to the formulation’s antimicrobial, antioxidant, and anti-inflammatory effects.

Optimization, Characterization and In Vivo Evaluation of Mupirocin Nanocrystals for Topical Administration

Treatment of infectious skin conditions resulting from wounds and burns with topical antibiotics is challenging, particularly those caused by methicillin-resistant Staphylococcus aureus bacteria (MRSA). This is due to the formation of bacterial biofilms characterized by antimicrobial resistance. Mupirocin (MP), a widely used topical antibiotic, is active against gram-positive bacteria including MRSA. However, MP suffers from sub-optimal therapeutic efficacy due to its poor water-solubility and the significant rise in MP-resistant S. aureus. In this study, the physico-chemical characteristics of MP were modified through nanocrystallization to improve its therapeutic efficacy for the treatment of skin infections. Mupirocin-nanocrystals (MP-NC) were prepared using a nanoprecipitation technique and optimized using a D-optimal response surface design. The optimization of MP-NC produced ultra-small monodisperse spherical particles with a mean diameter of 70 nm and a polydispersity index of 0.2. The design resulted in two optimal MP-NC formulations that were evaluated by performing series of in vitro, ex vivo, microbiological, and in vivo studies. In-vitro results showed a 10-fold increase in the saturation solubility and a 9-fold increase in the dissolution rate of MP-NC. Ex vivo permeation studies, using pig ears skin, showed a 2-fold increase in the dermal deposition of MP-NC with the highest drug deposition occurring at 500-µm skin depth. Moreover, the optimal MP-NC formulations were lyophilized and incorporated into a 2% w/w cream. Microbiological studies revealed a 16-fold decrease in the minimum inhibitory concentration and the minimum bactericidal concentration of MP-NC. In vivo studies, using a rat excision burn wound model, demonstrated rapid and complete healing of infected burn wounds in rats treated with MP-NC cream in comparison to marketed Avoban ointment. Our results suggest that nanocrystallization of MP may provide an avenue through which higher levels of a topically applied MP can be permeated into the skin to reach relevant infectious areas and exert potential local antibacterial effects.

A modified burn comb model with a new dorsal frame that allows for local treatment in partial-thickness burns in rats

Burn wound progression (BWP) leads to vertical and horizontal injury extension. The "burn comb model" is commonly used, in which a full-thickness burn with intercalated unburned interspaces is induced. We aimed to establish an injury progressing to the intermediate dermis, allowing repeated wound evaluation. Furthermore, we present a new dorsal frame that enables topical drug application. 8 burn field and 6 interspaces were induced on each of 17 rats' dorsa with a 10-second burn comb application. A developed 8-panel aluminum frame was sutured onto 12 animals and combined with an Elizabethan collar. Over 14 days, macroscopic & histologic wound assessment and Laser-Speckle-Contrast-Imaging (LSCI) were performed besides evaluation of frame durability. The 10-second group was compared to 9 animals injured with a full-thickness 60-second model. Frame durability was sufficient up to day 4 with 8 of 12 frames (67%) still mounted. The 60-second burn led to an increased extent of interspace necrosis (p=0.002). The extent of necrosis increased between days 1 and 2 (p=0.001), following the 10-second burn (24%±SEM 8% to 40%±SEM 6%) and the 60-second burn (57%±SEM 6% to 76%±SEM 4%). Interspace LSCI perfusion was higher than burn field perfusion. It earlier reached baseline levels in the 10-second group (on day 1: 142%±SEM 9% vs. 60%±SEM 5%; p<0.001). Within day 1, the 10-second burn showed histological progression to the intermediate dermis, both in interspaces and burn fields. This burn comb model with its newly developed fixed dorsal frame allows investigation of topical agents to treat BWP in partial-thickness 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.

VEGETABLE CELLULOSE NANOFIBER DRESSING AIDS IN THE HEALING PROCESS OF THIRD-DEGREE BURNS? STUDY ON RATS

BACKGROUND

The treatment of 3rd degree burns represents a major medical challenge. Pinus vegetable cellulose is a biomaterial with characteristic similar to bacterial cellulose.

AIM

To evaluate the safety of cellulose membrane (Pinus sp) in the treatment of 3rd burns in rats and to compare its effectiveness with the bacterial membrane already on the market.

METHOD

Thirty-three Wistar rats were beaten with a 3rd degree burn on back skin by applying water at 98º C for 30 s. Then, they were divided into three groups (n=11): group 1 - simple dressing with gauze; group 2 - dressing with bacterial cellulose membrane; and group 3 - dressing with vegetable cellulose membrane. The animals were maintained for 15 days to check the general clinical status, macroscopic aspect, contraction of the wounds and microscopic analysis for the degree of healing and collagenization.

RESULTS

They were clinically well during the experiment. During the removal of the dressing, there was bleeding in the wound of the control group, unlike the groups treated with cellulose membranes, which protected the bed from injury. The macroscopic evaluation showed a greater contraction of the wounds treated with the membranes in relation to the control. A microscopic analysis revealed that most of the wounds were in advanced healing degree with predominance of mature collagen in all groups.

CONCLUSION

Pinus sp cellulose membrane showed efficacy similar to that of the bacterial membrane in the treatment of 3rd degree burns.

New Chimeric Groin Flap: Experimental Model in Rats

AIM

Increased emphasis is on using tissue substitutes and stem cells to improve flap applicability and survival rates. To accomplish this, the first step is to have a versatile experimental flap, easy to harvest and use as a template. We sought to develop a reliable experimental chimeric groin flap with free mobility and reliable bloods supply that can be twisted, relocated, and integrated easily with other materials.

MATERIALS AND METHODS

Ten male Wistar rats were included. The flap consists of a 2.5-cm skin paddle centered on the medial branch of the inferior epigastric artery and a 4.5/2-cm fat pad supplied by the lateral branch of the inferior epigastric artery. After being raised, flaps were resutured in their anatomical position. Flaps were followed up for 15 days. At the end of the study, the viability of flaps was analyzed by ultrahigh-frequency ultrasound, nontargeted contrast study, and histology assessment.

RESULTS

All flaps survived without significant complications. Nontargeted microbubbles spread evenly in both the superficial and deep flap. Ultrasound assessment at day 15 showed no significant areas of necrosis or edema. Histology examination of 3 random flaps confirmed vessel patency and flap viability.

CONCLUSION

We propose a simple, easy to harvest and reliable experimental flap which offers a main advantage of all-around mobility through its chimeric design. It is a suitable model for bioengineering studies as it can be used as a template for integration of tissue substitutes or stem cells, between its 2 components.

Effects of Xenogen Mesenchymal Stem Cells and Cryo-Platelet Gel on Intractable Wound Healing in Animal

BACKGROUND

Today, the effects of growth factors and mesenchymal stem cells (MSCs) in promoting wound healing have been confirmed.

OBJECTIVE

This study aimed to investigate the effect of MSCs and platelet cryogel on wound healing.

METHODS

40 male Wistar rats were randomly divided into five groups (n=8). The control group just dressed, the second group received platelet cryogel, the third group received platelet cryogel containing MSCs, the fourth group received plasma, and the fifth group received plasma plus MSCs. The biopsy was obtained from the wounds in 2, 4, 6, and 8 days of the treatment. Then pathological evaluation was conducted. Finally, qRT-PCR was performed to determine angiogenesis.

RESULTS

The intervention groups had faster wound healing and lower wound area than the control group (p<0.05). The highest wound healing rate and the smallest wound area were observed in the group after receiving platelet cryogel plus MSCs. Angiogenesis, fibrosis, myoepithelial and epithelialization in the pathologic examination using H & E staining were not significantly different between the groups. The expression of Ang-1 in the intervention groups was higher than the control group and the highest expression was observed in the platelet cryogel plus MSCs, followed by the platelet cryogel group. The expression of VEGF in the plasma plus MSCs was higher than in the other groups.

CONCLUSION

Further studies require to determine the effects of combined use of platelet cryogel plus MSCs on other types of wounds and evaluate mechanisms involved in wound healing like collagenases and inflammatory factors.

A Practical Noncontact Model to Create Standardized Experimental Burn Wounds of Any Thickness: Blue Beam Laser Pointer for Burn Induction

The objective of this study was to describe a predictable and easy-to-use model that can create standardized burn wounds. A 450-nm 1000-mW blue beam laser pointer was used to create burn wounds on the dorsal skin of 24 Sprague Dawley rats. Twelve distinct areas of dorsal skin were pulsed for 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, and 23 seconds with the help of a punched plastic card template. Three groups of 8 animals were killed immediately after on the third day and on the seventh day of the procedure and tissue samples were taken for histological evaluation and measurements. A second-degree burn was obtained in all animals with 3 and 5 seconds of laser application on the same day, third day, and seventh day measurements. Seven seconds of application resulted in a burn depth of 84.87% of dermis on the application day which deepened to involve the whole dermal layer on the third and seventh day. Nine seconds and longer application times resulted in third-degree burn wounds. Burn induction with blue beam laser pointer is an easy-to-use, predictable and safe model to create a standardized burn wound of desired thickness.

Effects of Hair Follicle Stem Cells on Partial-Thickness Burn Wound Healing and Tensile Strength

Background:

The recent improvements in wound healing have led to new strategies in regenerative medicine. Burn wound healing is an important issue in skin regeneration and has multiple indications for stem cell therapy. HFSCs are a highly promising source of stem cells for healing use, as these cells are accessible, active and pluripotent adult stem cells.

Methods:

HFSCs of the rat whisker were isolated, cultured, and labeled with DiI. Flow cytometry method was used to detect special markers of HFSCs. Deep partial-thickness burn wound was created, and labeled HFSCs were injected around the wound bed. Wound closure was recorded via digital photographs. The inflicted rats were sacrificed at 3, 7, or 14 days post burn and used for subsequent histological and tensiometry analysis.

Results:

Our results indicated that HFSCs were positive for Nestin and CD34 markers, but negative for Kr15. Morphological and histological photographs revealed that wound closure rate was accelerated in stem cell-treated group compared with other groups. In addition, faster re-epithelialization and collagen deposition were observed. The immunohistochemical analysis suggested that CD31 expression and vascular density enhanced in the stem cell-treated group. Further, tissue tensile strength increased in HFSCs-treated rats in comparison to the control group.

Conclusion:

The present study demonstrates that HFSCs could accelerate burn wound healing as well as tensile strength in rats.

A new model for standardising and treating thermal injury in the rat

Thermal burn injury methodologies are inconsistently described within the current literature. To permit the advancement of new treatments there is an urgent need for the development and standardisation of an acute rat model. We describe a rat thermal burn model that involves: anaesthesia, chronic catheterisation, skin preparation, baseline hemodynamic and physiological monitoring, and a quantifiable method to reproduce a severe full-thickness burns injury affecting ∼30% percent of the total body surface area (%TBSA). Following a 15 min post-burn period, treatment commences with an acute monitoring phase lasting up to 8 h, which can be modified according to individual protocols. This model reflects the clinical continuum-of-care from point-of-injury, a 15 min ambulance response time, a 60 min prehospital phase and hospital treatment monitoring phase. The model is validated with histological evidence of full-thickness injury, evidence of the hypermetabolic response (K+, Base Excess, lactate) and changes in complete blood counts. •It has been 50 years since Walker and Mason published their widely popular "A Standard Animal Burn Model".•The model, however, lacks quantifiable methodology for the assessment of burn thickness, surface area burnt and physiological status.•We present a new standardised method for evaluation of drug and interventional therapies that mimic the clinical scenario including ambulance response, pre-hospital and hospital phases after burn.

Antibiofilm Potential of Silver Sulfadiazine-Loaded Nanoparticle Formulations: A Study on the Effect of DNase-I on Microbial Biofilm and Wound Healing Activity

Biofilm resistance is one of the severe complications associated with chronic wound infections, which impose extreme microbial tolerance against antibiotic therapy. Interestingly, deoxyribonuclease-I (DNase-I) has been empirically proved to be efficacious in improving the antibiotic susceptibility against biofilm-associated infections. DNase-I hydrolyzes the extracellular DNA, a key component of the biofilm responsible for the cell adhesion and strength. Moreover, silver sulfadiazine, a frontline therapy in burn wound infections, exhibits delayed wound healing due to fibroblast toxicity. In this study, a chitosan gel loaded with solid lipid nanoparticles of silver sulfadiazine (SSD-SLNs) and supplemented with DNase-I has been developed to reduce the fibroblast cytotoxicity and overcome the biofilm-imposed resistance. The extensive optimization using the Box-Behnken design (BBD) resulted in the formation of SSD-SLNs with a smooth surface as confirmed by scanning electron microscopy and controlled release (83%) for up to 24 h. The compatibility between the SSD and other formulation excipients was confirmed by Fourier transform infrared, differential scanning calorimetry, and powder X-ray diffraction studies. Developed SSD-SLNs in combination with DNase-I inhibited around 96.8% of biofilm of Pseudomonas aeruginosa as compared to SSD with DNase-I (82.9%). In line with our hypothesis, SSD-SLNs were found to be less toxic (cell viability 90.3 ± 3.8% at 100 μg/mL) in comparison with SSD (Cell viability 76.9 ± 4.2%) against human dermal fibroblast cell line. Eventually, the results of the in vivo wound healing study showed complete wound healing after 21 days' treatment with SSD-SLNs along with DNase-I, whereas marketed formulations SSD and SSD-LSNs showed incomplete healing after 21 days. Data in hand suggest that the combination of SSD-SLNs with DNase-I is an effective treatment strategy against the biofilm-associated wound infections and accelerates wound healing.

Development of a reproducible in vivo laser-induced scar model for wound healing study and management

The aim of the current study was to establish animal scar models in a simple and rapid manner by comparing three methods. Wounds were created on the buttocks of Sprague Dawley rats. For Group 1, the initial wound was created by surgical incision. For Groups 2 and 3, a 1470-nm laser was employed to generate dermal burns as the initial wound. The wounds in Groups 1 and 3 were then sutured for three days. After the wound healing, Group 2 generated the largest collagen proportion with abundant collagen type I and significant increases in α-SMA and TGF-β1. The proposed method can be an efficient way to develop rat scar models in a simple manner for evaluating scar treatment.

Collagen-Polyvinyl Alcohol-Indomethacin Biohybrid Matrices as Wound Dressings

The aim of this study is to design, develop and evaluate new biohybrid sponges based on polymers (collagen and polyvinyl alcohol) with and without indomethacin as anti-inflammatory drug model to be used for tissue regeneration in wound healing. Type I fibrillar collagen in the form of a gel and different concentrations of polyvinyl alcohol were mixed together to prepare composite gels. Both control samples, without indomethacin and with indomethacin, were obtained. All samples were crosslinked with glutaraldehyde. By freeze-drying of hydrogels, the spongious forms (matrices) were obtained. The matrices were characterized by FT-IR spectroscopy, scanning electron microscopy (SEM), water absorption, enzymatic degradation and in vitro indomethacin release. The pharmacological effect of the spongious biohybrid matrices was determined on an experimental model of burns induced to Wistar rats. The SEM images showed a porous structure with interconnected pores. Collagen sponges present a structure with pore sizes between 20 and 200 µm, which became more and more compact with polyvinyl alcohol addition. The FT-IR showed interactions between collagen and polyvinyl alcohol. The enzymatic degradation indicated that the most stable matrix is the one with the ratio 75:25 of collagen:polyvinyl alcohol (ACI75), the other ones being degradable in time. The kinetic data of indomethacin release from matrices were fitted with different kinetic models and highlighted a biphasic release of the drug. Such kinetic profiles are targeted in skin wound healing for which important aspects are impaired inflammation and local pain. The treatment with sponges associated with anti-inflammatory drug had beneficial effects on the healing process in experimentally induced burns compared to the corresponding matrices without indomethacin and the classical treated control group.

Physical Properties of Implanted Porous Bioscaffolds Regulate Skin Repair: Focusing on Mechanical and Structural Features

Porous bioscaffolds are applied to facilitate skin repair since the early 1990s, but a perfect regeneration outcome has yet to be achieved. Until now, most efforts have focused on modulating the chemical properties of bioscaffolds, while physical properties are traditionally overlooked. Recent advances in mechanobiology and mechanotherapy have highlighted the importance of biomaterials' physical properties in the regulation of cellular behaviors and regenerative processes. In skin repair, the mechanical and structural features of porous bioscaffolds are two major physical properties that determine therapeutic efficacy. Here, first an overview of natural skin repair with an emphasis on the major biophysically sensitive cell types involved in this multistage process is provided, followed by an introduction of the four roles of bioscaffolds as skin implants. Then, how the mechanical and structural features of bioscaffolds influence these four roles is discussed. The mechanical and structural features of porous bioscaffolds should be tailored to balance the acceleration of wound closure and functional improvements of the repaired skin. This study emphasizes that decoupling and precise control of the mechanical and structural features of bioscaffolds are significant aspects that should be considered in future biomaterial optimization, which can build a foundation to ultimately achieve perfect skin regeneration outcomes.

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.

Comparative evaluations of hypertrophic scar formation in in vivo models

BACKGROUND AND OBJECTIVE

Hypertrophic scar (HTS) results from a connective tissue reaction to trauma, inflammation, surgery, or burn on skin. In spite of various techniques for wound generation, the degree of scar in animal models after healing is still unpredictable and less reproducible. The objective of the current study was to identify the appropriate method to create the maximal HTS tissue in a reliable manner by comparing three different methods in vivo.

MATERIALS AND METHODS

A 27 ICR mice were tested for the in vivo evaluations. Three different methods were applied to develop wounds on the back of each mice for quantitative evaluations on collagen formation: Group 1 (thermal burn), Group 2 (chemical burn), and Group 3 (physical punch). After injury, each lesion was photographed to examine physical variations in the wound areas. Histological analysis was conducted on days 0, 7, and 28 to assess the extent of the injury in the tissue and to quantitatively compare the amount of collagen formation after wound healing.

RESULTS

Compared with Groups 1 and 3, Group 2 demonstrated the largest wound area that gradually decreased with healing time. However, the minimal axial damage (along tissue depth) occurred to Group 2 at day 0 (183.7 ± 28.9, 38.1 ± 9.2, and 296.0 ± 81.7 µm for Groups 1, 2, and 3, respectively). After 28 days, all the groups showed the complete healing and accompanied a significant increase in the number of fibroblast and collagen generation with well-oriented and denser collagen fibers, in comparison with normal skin. Group 2 yielded twice thicker skin (both epidermis and dermis) than the other groups (970.8 ± 108.8 µm for Group 2 vs. 381.5 ± 30.8 µm for Group 1 and 442.9 ± 56.3 µm for Group 3; P < 0.001).

CONCLUSION

The proposed chemical burn can be the optimal method to create collagenous scar tissue in the mouse model. Further in vivo investigations with rat models will be performed to validate the current technique for laser scar treatment in terms of reliability and immunohistochemical responses. Lasers Surg. Med. 9999:XX-XX, 2017. © 2017 Wiley Periodicals, Inc.

Prediction of Scar Size in Rats Six Months after Burns Based on Early Post-injury Polarization-Sensitive Optical Frequency Domain Imaging

Hypertrophic scars remain a major clinical problem in the rehabilitation of burn survivors and lead to physical, aesthetic, functional, psychological, and social stresses. Prediction of healing outcome and scar formation is critical for deciding on the best treatment plan. Both subjective and objective scales have been devised to assess scar severity. Whereas scales of the first type preclude cross-comparison between observers, those of the second type are based on imaging modalities that either lack the ability to image individual layers of the scar or only provide very limited fields of view. To overcome these deficiencies, this work aimed at developing a predictive model of scar formation based on polarization sensitive optical frequency domain imaging (PS-OFDI), which offers comprehensive subsurface imaging. We report on a linear regression model that predicts the size of a scar 6 months after third-degree burn injuries in rats based on early post-injury PS-OFDI and measurements of scar area. When predicting the scar area at month 6 based on the homogeneity and the degree of polarization (DOP), which are signatures derived from the PS-OFDI signal, together with the scar area measured at months 2 and 3, we achieved predictions with a Pearson coefficient of 0.57 (p < 10⁻⁴) and a Spearman coefficient of 0.66 (p < 10⁻⁵), which were significant in comparison to prediction models trained on randomly shuffled data. As the model in this study was developed on the rat burn model, the methodology can be used in larger studies that are more relevant to humans; however, the actual model inferred herein is not translatable. Nevertheless, our analysis and modeling methodology can be extended to perform larger wound healing studies in different contexts. This study opens new possibilities for quantitative and objective assessment of scar severity that could help to determine the optimal course of therapy.

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.

Poor methodological quality and reporting standards of systematic reviews in burn care management

The methodological and reporting quality of burn-specific systematic reviews has not been established. The aim of this study was to evaluate the methodological quality of systematic reviews in burn care management. Computerised searches were performed in Ovid MEDLINE, Ovid EMBASE and The Cochrane Library through to February 2016 for systematic reviews relevant to burn care using medical subject and free-text terms such as 'burn', 'systematic review' or 'meta-analysis'. Additional studies were identified by hand-searching five discipline-specific journals. Two authors independently screened papers, extracted and evaluated methodological quality using the 11-item A Measurement Tool to Assess Systematic Reviews (AMSTAR) tool and reporting quality using the 27-item Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist. Characteristics of systematic reviews associated with methodological and reporting quality were identified. Descriptive statistics and linear regression identified features associated with improved methodological quality. A total of 60 systematic reviews met the inclusion criteria. Six of the 11 AMSTAR items reporting on 'a priori' design, duplicate study selection, grey literature, included/excluded studies, publication bias and conflict of interest were reported in less than 50% of the systematic reviews. Of the 27 items listed for PRISMA, 13 items reporting on introduction, methods, results and the discussion were addressed in less than 50% of systematic reviews. Multivariable analyses showed that systematic reviews associated with higher methodological or reporting quality incorporated a meta-analysis (AMSTAR regression coefficient 2.1; 95% CI: 1.1, 3.1; PRISMA regression coefficient 6·3; 95% CI: 3·8, 8·7) were published in the Cochrane library (AMSTAR regression coefficient 2·9; 95% CI: 1·6, 4·2; PRISMA regression coefficient 6·1; 95% CI: 3·1, 9·2) and included a randomised control trial (AMSTAR regression coefficient 1·4; 95%CI: 0·4, 2·4; PRISMA regression coefficient 3·4; 95% CI: 0·9, 5·8). The methodological and reporting quality of systematic reviews in burn care requires further improvement with stricter adherence by authors to the PRISMA checklist and AMSTAR tool.

A Rehabilomics framework for personalized and translational rehabilitation research and care for individuals with disabilities: Perspectives and considerations for spinal cord injury

Despite many people having similar clinical presentation, demographic factors, and clinical care, outcome can differ for those sustaining significant injury such as spinal cord injury (SCI) and traumatic brain injury (TBI). In addition to traditional demographic, social, and clinical factors, variability also may be attributable to innate (including genetic, transcriptomic proteomic, epigenetic) biological variation that individuals bring to recovery and their unique response to their care and environment. Technologies collectively called "-omics" enable simultaneous measurement of an enormous number of biomolecules that can capture many potential biological contributors to heterogeneity of injury/disease course and outcome. Due to the nature of injury and complex disease, and its associations with impairment, disability, and recovery, rehabilitation does not lend itself to a singular "protocolized" plan of therapy. Yet, by nature and by necessity, rehabilitation medicine operates as a functional model of "Personalized Care". Thus, the challenge for successful programs of translational rehabilitation care and research is to identify viable approaches to examine broad populations, with varied impairments and functional limitations, and to identify effective treatment responses that incorporate personalized protocols to optimize functional recovery. The Rehabilomics framework is a translational model that provides an "-omics" overlay to the scientific study of rehabilitation processes and multidimensional outcomes. Rehabilomics research provides novel opportunities to evaluate the neurobiology of complex injury or chronic disease and can be used to examine methods and treatments for person-centered care among populations with disabilities. Exemplars for application in SCI and other neurorehabilitation populations are discussed.

Creation of consistent burn wounds: a rat model

Background

Burn infliction techniques are poorly described in rat models. An accurate study can only be achieved with wounds that are uniform in size and depth. We describe a simple reproducible method for creating consistent burn wounds in rats.

Methods

Ten male Sprague-Dawley rats were anesthetized and dorsum shaved. A 100 g cylindrical stainless-steel rod (1 cm diameter) was heated to 100℃ in boiling water. Temperature was monitored using a thermocouple. We performed two consecutive toe-pinch tests on different limbs to assess the depth of sedation. Burn infliction was limited to the loin. The skin was pulled upwards, away from the underlying viscera, creating a flat surface. The rod rested on its own weight for 5, 10, and 20 seconds at three different sites on each rat. Wounds were evaluated for size, morphology and depth.

Results

Average wound size was 0.9957 cm² (standard deviation [SD] 0.1845) (n=30). Wounds created with duration of 5 seconds were pale, with an indistinct margin of erythema. Wounds of 10 and 20 seconds were well-defined, uniformly brown with a rim of erythema. Average depths of tissue damage were 1.30 mm (SD 0.424), 2.35 mm (SD 0.071), and 2.60 mm (SD 0.283) for duration of 5, 10, 20 seconds respectively. Burn duration of 5 seconds resulted in full-thickness damage. Burn duration of 10 seconds and 20 seconds resulted in full-thickness damage, involving subjacent skeletal muscle.

Conclusions

This is a simple reproducible method for creating burn wounds consistent in size and depth in a rat burn model.

Animal models in burn research

Burn injury is a severe form of trauma affecting more than 2 million people in North America each year. Burn trauma is not a single pathophysiological event but a devastating injury that causes structural and functional deficits in numerous organ systems. Due to its complexity and the involvement of multiple organs, in vitro experiments cannot capture this complexity nor address the pathophysiology. In the past two decades, a number of burn animal models have been developed to replicate the various aspects of burn injury, to elucidate the pathophysiology, and to explore potential treatment interventions. Understanding the advantages and limitations of these animal models is essential for the design and development of treatments that are clinically relevant to humans. This review aims to highlight the common animal models of burn injury in order to provide investigators with a better understanding of the benefits and limitations of these models for translational applications. While many animal models of burn exist, we limit our discussion to the skin healing of mouse, rat, and pig. Additionally, we briefly explain hypermetabolic characteristics of burn injury and the animal model utilized to study this phenomena. Finally, we discuss the economic costs associated with each of these models in order to guide decisions of choosing the appropriate animal model for burn research.