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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

A model mimicking the clinical scenario of burn injury and infection is necessary for furthering burn research. The present protocol demonstrates a simple and reproducible rat burn infection model comparable to that in humans. This facilitates the study of burn and infections following burn for developing new topical antibiotic treatments.

Abstract

Burn induction methodologies are inconsistently described in rat models. A uniform burn wound model, which represents the clinical scenario, is necessary to perform reproducible burn research. The present protocol describes a simple and reproducible method to create ~20% total body surface area (TBSA) full-thickness burns in rats. Here, a 22.89 cm2 (5.4 cm diameter) copper rod heated at 97 °C in a water bath was applied to the rat skin surface to induce the burn injury. A copper rod with a high thermal conductivity was able to dissipate the heat deeper in the skin tissue to create a full-thickness burn. Histology analysis shows attenuated epidermis with coagulative damage to the full-thickness extent of the dermis and the subcutaneous tissue. Additionally, this model is representative of the clinical situations observed in hospitalized burn patients following burn injury such as immune dysregulation and bacterial infections. The model can recapitulate the systemic bacterial infection by both Gram-positive and Gram-negative bacteria. In conclusion, this paper presents an easy-to-learn and robust rat burn model that mimics the clinical situations, including immune dysregulation and bacterial infections, which is of considerable utility for the development of new topical antibiotic drugs for burn wound and infections.

Introduction

Burn injuries are among the most devastating forms of trauma, with mortality rates reaching 12% even in specialized burn centers1,2,3. According to recently published reports, ~486,000 burn patients require medical care annually in the United States, with nearly 3,500 deaths1,2,3,4,5,6. Burn injury imposes a major challenge for patients' immune system and creates a signif....

Protocol

All procedures were approved by the Institutional Animal Care and Use Committee (IACUC) of The University of North Carolina and were conducted in accordance with its established guidelines. Male and female Sprague Dawley rats (250-300 g) aged 7-9 weeks old were used for the experiments. All animals were housed in a 12 h:12 h light-dark cycle with free access to food and water ad libitum. Always work with your institutional veterinarian about an analgesic plan prior to study initiation. 

Representative Results

The protocol presented here is highly reproducible and resulted in a third-degree, full-thickness burn injury in rats. The burn wound appears waxy white after burn induction (Figure 2B). The color of the burn injury changed from white to brown over the course of 72 h post burn (Figure 2B-E).

Histological analysis confirmed a full-thickness burn (depth >2.61 mm at 24 h post burn;

Discussion

Several burn models have been presented to study the pathophysiology of burn injury8,12,16,17. In the present study, we employed a rat model to develop a simple and reproducible protocol to induce a full-thickness burn followed by bacterial infection to simulate an infected burn trauma in patients. The choice of the rat as the animal model to mimic human conditions is based on a balance of cost.......

Acknowledgements

The authors thank the Division of Comparative Medicine at the University of North Carolina for the provision and care of animals. We thank Lauren Ralph and Mia Evangelista in the Pathology Services Core for expert technical assistance with Histopathology/Digital Pathology, including tissue sectioning and imaging. This research was supported by a research grant from the Department of Defense (Award number W81XWH-20-1-0500, GR and TV).

....

Materials

NameCompanyCatalog NumberComments
1 mL syringeBD, USA309597Used to inject the analgesic
1.7 mL MicrotubeOlympus, USA24-282Used to carry morphine
10% NBFVWR, USA16004-115Used to fix the skin piece for staining
30 mL syringeBD, USA302832Used to inject the lactate ringer solution
70% ethyl alcoholFischer Scientific, USABP28184
Aperio AT2 Digital Pathology  Slide Scanner with ImageScope softwareAperio, Technologies Inc., Vista, CA, USAn/aScanning of H & E slides and analysis
Cetrimide agar platesBD, USA285420Selective media plates for Pseudomonas aeruginosa growth
Copper rodsn/an/aUsed to induce the burn injury
Cotton tipped applicatorsOMEGA Surgical supply, USA4225-IMCUsed to apply eye ointment
Electric shaverOster, USAGolden A5Used to remove the dorsal side hairs
Eye lubeDechra, UKn/aThe eye wetting agent to provide long lasting comfort and avoid eye dryness
Fluff filled underpadsMedline, USAMSC281225Used in the burn procedure
ForcepF.S.T.11027-12Used to hold the skin piece
Gauze spongesOasis, USAPK412Used to clean the applied nair cream from the dorsal side 
Heat-resistant glovesn/an/aUsed to hold the heated copper rods
Hematology AnalyzerIDEXX laboratories, USAProCyte Dx
Induction chamberKent Scientific, USAvetFlo-0730Used to anesthesize the animals
Insulin syringeBD, USA329461
IsofluranePivetal, USANDC46066-755-04Used to anesthesized rats to induce a loss of consciousness
Isoflurane vaporisern/an/a
Lactated ringer's solutionicumedical, USANDC0990-7953-09Used to resuscitate the rats
L-shaped spreaderFischer Scientific, USA14-665-230
Mannitol AgarBD, USA211407Selective media plates for Staphylococcus aureus growth
Minicollect tubes (K2EDTA)greiner bio-one, USA450480Used to collect the blood
MorphineMallinckrodt, UKNDC0406-8003-30This analgesia was used to induce the inability to feel burn injury pain
Muller Hinton BrothBD, USA275730
Muller Hinton II AgarBD, USA211438
Nair hair removal lotionNair, USAn/aUsed to remove the residual hairs on dorsal side
Needle 23 GBD, USA305193Used to inject the lactate ringer solution
Normal salinen/an/a
SpectrophotometerThermoScientific, USAGenesys 30
Sprague-Dawley rats, male and femaleCharles River Labsn/a7-9 weeks old for burn induction
Surgical ScissorF.S.T.14501-14Used to cut the desired skin piece
Tissue collection tubesGlobe Scientific220101236
Tissue HomogenizerKinematica, Inc, USAPOLYTRON PT2100Used to homogenize the tissue samples
Water bathFischer Scientific, USAn/aUsed to induce the burn injury
Weighted heating padComfytemp, USAn/aUsed during the procedure to keep rat's body warm

References

  1. Peck, M., Molnar, J., Swart, D. A global plan for burn prevention and care. Bulletin of the World Health Organization. 87, 802-803 (2009).
  2. American Burn Association. Burn incidence and treatment in the United States: 2011 fact sheet.

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