This work was supported by generous funding from Shriners Children&#39;s Research Grant to S.N.T. Y.B. was supported by Shriners Hospital for Children. We also gratefully acknowledge funding to S.N.T. from the US National Institute of Health (K99/R00 HL1431149; R01HL157803; R01DK134590, R24OD034189), American Heart Association (18CDA34110049), Harvard Medical School Eleanor and Miles Shore Fellowship, Polsky Family Foundation, and the Claflin Distinguished Scholar Award on behalf of the MGH Department of Surgery and/or MGH Executive Committee on Research. Further, we acknowledge the support provided by the Massachusetts General Hospital Executive Committee of Research for awarding the Fund for Medical Discovery (FMD) award to R.J. Finally, support from &#34;Fondation des Gueules Cass&#233;es&#34; (France), Rennes University (France), CHU de Rennes (France) and the French Society of Plastic Surgery to Y.B. is greatly acknowledged. The authors thank Knight Surgery Research Laboratory for their contribution and help with the anesthesia of the animals.

All animal work was performed in accordance with the ARRIVE (Animal Research: Reporting In Vivo Experiments) checklist37 and was compliant with the Massachusetts General Hospital Institutional Animal Care and Use Committee (IACUC) under protocol #2021N000271. Humane care was provided to the animals, following the National Institute of Health Guide for the Care and Use of Laboratory Animals38. Five 30 kg female Yucat&#225;n minipigs were used for these experiments. The anima...

Yucatan Minipig Burn Wound Model for Analysis of Multi-Depth Burns

Wound healing following burn injuries is a long process that can take up to several months, with various treatment options and considerations for patient care2,13. In order to study it, a reliable and reproducible model is needed. Several animal models have been described, mainly including rodents29,45,46 and swine29,4...

Burns are a major public health problem and affect more than 480,000 patients in the US each year, according to the National Burn Repository1,2. This leads to more than 50,000 yearly hospitalizations for non-fatal complex cases requiring in-depth care2. Moreover, burns are a fundamental cause of military mortality and morbidity and are responsible for 10% to 30% of military casualties3,4. The management of burns has remained nearly unchanged for a long time, despite its immense and diverse impacts on patients, ranging from physical to psychological and emotional5.
Initial diagnosis and evaluation of burn injuries lead to a baseline classification according to the type of burns (first, second, and third) or the depth of the affected tissue (superficial, partial thickness, and deep burns)6,7,8. Partial-thickness burns (first and second-degree) involve the epidermis and different depths of the dermis (superficial or deep dermis, i.e., superficial and deep second-degree burns)9. In particular, damage to the appendages in the deep dermis excludes the possibility of re-epithelialization from the adnexal epithelium10. By definition, full-thickness burns reach the subcutaneous fat, fascia and/or the underlying muscle (third-degree burns), and sometimes the bone (also referred to as fourth-degree burns)11,12.
Following hospitalization, burn patients receive special care involving a strategy consisting of a delicate balance between tissue debridement and preservation. The damaged and/or secondarily infected soft tissue needs to be progressively removed until healthy tissue is exposed, allowing for the use of specific dressings and skin grafts to improve the healing process13,14,15,16. Yet, caution is required during surgery to avoid unintentional removal of healing tissue and reduce complications for optimal recovery. Biologically, burns exhibit a central necrotic area encircled by a &#39;shadow&#39; or &#39;stasis&#39; zone, indicating potentially reversible ischemia. This area can either deteriorate, resulting in an extended necrosis zone, or heal by reversing the apoptotic process17,18. This varying severity of burns presents challenges for surgeons to assess accurately, complicating the balance between conservative treatments and surgical excision19. To date, no efficient tool is available to help characterize this &#34;shadow zone&#34; preceding burn conversion. Developing such tools is crucial for optimizing this delicate balance.
Several treatments have been tested to help decrease secondary burn conversion. Yet, no specific therapy is currently available in the clinic18. Other examples of advances in burn treatments include the development of modern wound dressings and nanomaterials20,21, tissue-engineered skin22,23, and novel epidermal culture approaches24,25. Also, modern reconstructive surgery and fasciocutaneous flaps have improved the management of long-term after-effects, particularly burn contractures following pathologic healing of fold areas26,27. These advancements give promising prospects for burn patients, improving their treatment strategies and quality of life, but recent results show that the functional impact still remains substantial, both in the physical and psychological spheres28. Taken together, the demand for innovative advancements in both burn diagnosis and burn treatment is substantial.
Overall, many approaches are aiming at improving the diagnosis, management, and treatment of complex burn cases, and researchers need a reproducible and relevant model to test these new approaches. Due to its biological complexity, involving several organs and systemic reactions, no in vitro model proved itself relevant to study the burn wound process29. Rodent models have shown major discrepancies with humans due to major differences in biology, skin architecture, elasticity, and lack of adherence to the underlying structures29. In contrast, the swine model has proven to be relevant due to the structural similarity of swine skin to human skin30,31,32. It presents with a similar vascularization, elastic fiber composition, and renewal timing. Moreover, the hair follicle and apocrine annexes allow for islanded re-epithelialization, as can be observed in clinical superficial burns33,34. More specifically, Yucatan minipig models provide interesting features, making them relevant to studying pigmented skin35 and long-term outcomes with minimal physical changes36.
The purpose of this article is to describe a reliable multi-degree burn model in Yucat&#225;n pigs, enabling the study of several second and third-degree burns on the same subject. This provides a relevant and reproducible model for studying diagnostic and therapeutic innovations for the management of burns. Further, this model features different burn types and severity, a long-term follow-up allowing the study of burn contracture and pathologic healing, and pigmented skin differential behavior, which is known to have specific characteristics.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Adson tissue forceps</td>
			<td>Jarit</td>
			<td>130-234</td>
			<td></td>
		</tr>
		<tr>
			<td>Aluminum beads</td>
			<td>Lab Armor</td>
			<td>42370-002</td>
			<td>Lab Armor Beads&#160;</td>
		</tr>
		<tr>
			<td>Buprenorphine hydrochloride</td>
			<td>Ranbaxy Pharmaceuticals</td>
			<td>NDC:12469-0757-01</td>
			<td>Buprenex Injectable</td>
		</tr>
		<tr>
			<td>Carprofen</td>
			<td>Pfizer</td>
			<td>NADA 141-199</td>
			<td>Rymadyl 50mg/ml injectable&#160;</td>
		</tr>
		<tr>
			<td>Cylindric brass block</td>
			<td>Hand-made</td>
			<td>N/A</td>
			<td>Engineering drawing included in the manuscript</td>
		</tr>
		<tr>
			<td>Dermographic pen</td>
			<td>McKesson</td>
			<td>Surgical Skin Marker Sterile</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable #15 surgical scalpels</td>
			<td>Medline</td>
			<td>MDS15315</td>
			<td>Scalpel blades</td>
		</tr>
		<tr>
			<td>Fentanyl patch</td>
			<td>Mylan</td>
			<td>NDC:60505-7082</td>
			<td>Fentanyl Transdermal System</td>
		</tr>
		<tr>
			<td>Isoflurane&#160;</td>
			<td>Piramal</td>
			<td>NDC:66794-013-25</td>
			<td>Isoflurane, USP</td>
		</tr>
		<tr>
			<td>McPherson Bipolar coagulation forceps</td>
			<td>Bovie</td>
			<td>A842</td>
			<td>Reusable, autoclavable</td>
		</tr>
		<tr>
			<td>Miltex assorted biopsy punches (3,4 and 5 mm)</td>
			<td>Integra</td>
			<td>33-38</td>
			<td>Biopsy punches- size to adapt to the study</td>
		</tr>
		<tr>
			<td>Non woven gauze</td>
			<td>Starryshine</td>
			<td>GZNW22</td>
			<td>2 x 2&#34; non woven 4 ply medical gauze pads</td>
		</tr>
		<tr>
			<td>Povidone-Iodine</td>
			<td>Betadine</td>
			<td>NDC:0034-9200-88</td>
			<td>Surgical scrub 7.5%&#160;</td>
		</tr>
		<tr>
			<td>Sterile isotonic sodium chloride solution 0.9%</td>
			<td>Aqualite System</td>
			<td>RL-2095</td>
			<td>Sterile saline solution</td>
		</tr>
		<tr>
			<td>Tattoo ink</td>
			<td>Spaulding &#38; Rogers</td>
			<td>Black - 2 oz - #9053</td>
			<td></td>
		</tr>
		<tr>
			<td>Tattoo marker</td>
			<td>Spaulding &#38; Rogers</td>
			<td>Special Electric Tattoo Marker</td>
			<td></td>
		</tr>
		<tr>
			<td>Tattoo needle</td>
			<td>Spaulding &#38; Rogers</td>
			<td>1310251</td>
			<td>Tattoo 5 point needle</td>
		</tr>
		<tr>
			<td>Tegaderm Transparent Film Dressing</td>
			<td>3M</td>
			<td>1.628</td>
			<td>Large transparent adhesive dressing</td>
		</tr>
		<tr>
			<td>Temperature-controlled hot plate</td>
			<td>Cole-Parmer</td>
			<td>03407-11</td>
			<td>StableTemp hot plate stirrer</td>
		</tr>
		<tr>
			<td>Thermometer</td>
			<td>American Scientific</td>
			<td>U14295</td>
			<td>Tube mercury thermometerr</td>
		</tr>
		<tr>
			<td>Tiletamine and zolazepam hydrochloride</td>
			<td>Zoetis</td>
			<td>NDC:54771-9050</td>
			<td>Telazol</td>
		</tr>
		<tr>
			<td>Tincture of Benzoin Spray</td>
			<td>Smith&#38;Nephew</td>
			<td>407000</td>
			<td>Adhesive layer spray</td>
		</tr>
		<tr>
			<td>Triple Antibiotic ointment</td>
			<td>Fougera</td>
			<td>NDC 0168-0012-31</td>
			<td>Triple antibiotic ointment</td>
		</tr>
		<tr>
			<td>Tubular stockinette</td>
			<td>Medline</td>
			<td>NONNET02</td>
			<td>Curad Medline Latex Free Elastic Nets</td>
		</tr>
		<tr>
			<td>Warming blanket</td>
			<td>3M</td>
			<td>Bair Hugger 750 warming unit</td>
			<td></td>
		</tr>
		<tr>
			<td>Xeroform Occlusive Gauze Strip</td>
			<td>Covidien</td>
			<td>8884433301</td>
			<td>Xeroform petrolatum wound dressings</td>
		</tr>
		<tr>
			<td>Xylazine</td>
			<td>Vetone</td>
			<td>NDC:13985-704-10</td>
			<td>AnaSed LA</td>
		</tr>
		<tr>
			<td>Yucat&#224;n minipigs (female, 30 kg)</td>
			<td>Sinclair Bio Resources</td>
			<td>N/A</td>
			<td>Full pigmentation&#160;</td>
		</tr>
	</tbody>
</table>

a swine burn model for investigating the healing process in multiple depth burn wounds

Burn wound healing is a complex and long process. Despite extensive experience, plastic surgeons and specialized teams in burn centers still face significant challenges. Among these challenges, the extent of the burned soft tissue can evolve in the early phase, creating a delicate balance between conservative treatments and necrosing tissue removal. Thermal burns are the most common type, and burn depth varies depending on multiple parameters, such as temperature and exposure time. Burn depth also varies in time, and the secondary aggravation of the &#34;shadow zone&#34; remains a poorly understood phenomenon. In response to these challenges, several innovative treatments have been studied, and more are in the early development phase. Nanoparticles in modern wound dressings and artificial skin are examples of these modern therapies still under evaluation. Taken together, both burn diagnosis and burn treatments need substantial advancements, and research teams need a reliable and relevant model to test new tools and therapies. Among animal models, swine are the most relevant because of their strong similarities in skin structure with humans. More specifically, Yucatan minipigs show interesting features such as melanin pigmentation and slow growth, allowing for studying high phototypes and long-term healing. This article aims to describe a reliable and reproducible protocol to study multi-depth burn wounds in Yucatan minipigs, enabling long-term follow-up and providing a relevant model for diagnosis and therapeutic studies.

Author Spotlight: A Multi-Depth Porcine Model for Comprehensive Study of Burn Injuries and Healing Processes

A Swine Burn Model for Investigating the Healing Process in Multiple Depth Burn Wounds

Figure 2A,B display the results of multiple burns on the dorsum of a Yucat&#224;n minipig. Wounds (I) and (VII) are control wounds (37 &#176;C). Second-degree wounds (II; III and VIII) present with intense redness and blisters. In contrast, third-degree wounds (IV; V; and VI) are pale and indurated to palpation. It is to be noted that wound VIII looks intermediate between second and third degree: for the purpose of an ongoing study, we increased the contact time to 45 s at 6...

Read this Scientific Article Protocol about Author Spotlight: A Multi-Depth Porcine Model for Comprehensive Study of Burn Injuries and Healing Processes at JoVE.com

This protocol describes a reproducible multi-depth burn wound model in a Yucatan minipigs.

A Swine Burn Model for Investigating the Healing Process in Multiple Depth Burn Wounds

Abstract