Advancements in Regenerative Strategies Through the Continuum of Burn Care

Pro-inflammatory effect of obesity on rats with burn wounds

Objective

A burn is an inflammatory injury to the skin or other tissue due to contact with thermal, radioactive, electric, or chemical agents. Burn injury is an important cause of disability and death worldwide. Obesity is a significant public health problem, often causing underlying systemic inflammation. Studying the combined impact of burn injuries on obese patients has become critical to the successful treatment of these patients. The aim of this paper is to highlight the effect of inflammation associated with burn injuries on several body weight group in a rat study.

Materials and methods

Different degrees of obesity and burns were established in rats and divided into a normal weight group, overweight group, obese group, second-degree burn group, third-degree burn group, over-weight second-degree burn group, over-weight third-degree burn group, obese second-degree burn group, and obese third-degree burn group (20 rats per group). Changes in inflammatory factors and growth factor were measured on the 1st, 3rd, 7th and 14th days after burns were inflicted.

Results

The ELISA test showed that in the unburned control group, MCP-1, IL-1β and TNF-α protein expressions in the obese and over-weight groups were higher than the normal-weight group (P < 0.05). RT-PCR test showed that the expressions of MCP-1, IL-1β and TNF-α genes in the obese group were higher compared to the overweight and normal weight groups (P < 0.05). Three and 7 days after burns were inflicted, the level of VEGF in the normal weight group was higher than the obese group (P < 0.05), however increased VEGF was not observed on days 1 and 14.

Conclusion

Burn injury and obesity have a mutually synergistic effect on the body’s inflammatory response.

Determining clinically meaningful thresholds for innovative burn care products to reduce autograft: A US burn surgeon Delphi panel

Reducing the amount of donor skin needed for definitive wound closure can improve outcomes in patients with severe burns. This Delphi Consensus Panel (DCP) aimed to achieve expert consensus on the percentage reduction in donor skin for autograft that constitutes a clinically meaningful benefit. A two-round DCP of fifteen US burn surgeons was conducted via a web-based survey platform. Fourteen panelists (93.3%) completed both rounds. In Round 2, consensus, defined as ≥70% agreement, was achieved for five of the seven consensus statements. All panelists agreed that a clinically meaningful reduction in the amount of donor skin required would facilitate wound management and decrease donor site morbidity experienced by patients. Furthermore, based on three treatment scenarios, consensus was achieved for a clinically meaningful reduction in the amount of donor skin required for autograft for the adult population in deep partial-thickness and full-thickness burns. Findings from this DCP indicate that an innovative cellular and/or tissue product that would reduce the needed amount of donor skin, by the identified thresholds, has the potential to improve the outcomes for patients with severe burn injuries in a meaningful way.

Burns Depth Assessment Using Deep Learning Features

Purpose

Burns depth evaluation is a lifesaving task and very challenging that requires objective techniques to accomplish. While the visual assessment is the most commonly used by surgeons, its accuracy reliability ranges between 60 and 80% and subjective that lacks any standard guideline. Currently, the only standard adjunct to clinical evaluation of burn depth is Laser Doppler Imaging (LDI) which measures microcirculation within the dermal tissue, providing the burns potential healing time which correspond to the depth of the injury achieving up to 100% accuracy. However, the use of LDI is limited due to many factors including high affordability and diagnostic costs, its accuracy is affected by movement which makes it difficult to assess paediatric patients, high level of human expertise is required to operate the device, and 100% accuracy possible after 72 h. These shortfalls necessitate the need for objective and affordable technique.

Method

In this study, we leverage the use of deep transfer learning technique using two pretrained models ResNet50 and VGG16 for the extraction of image patterns (ResFeat50 and VggFeat16) from a a burn dataset of 2080 RGB images which composed of healthy skin, first degree, second degree and third-degree burns evenly distributed. We then use One-versus-One Support Vector Machines (SVM) for multi-class prediction and was trained using 10-folds cross validation to achieve optimum trade-off between bias and variance.

Results

The proposed approach yields maximum prediction accuracy of 95.43% using ResFeat50 and 85.67% using VggFeat16. The average recall, precision and F1-score are 95.50%, 95.50%, 95.50% and 85.75%, 86.25%, 85.75% for both ResFeat50 and VggFeat16 respectively.

Conclusion

The proposed pipeline achieved a state-of-the-art prediction accuracy and interestingly indicates that decision can be made in less than a minute whether the injury requires surgical intervention such as skin grafting or not.

Skin xenotransplantation: technological advances and future directions

PURPOSE OF REVIEW

To summarize the evolution of skin xenotransplantation and contextualize technological advances and the status of clinically applicable large animal research as well as prospects for translation of this work as a viable future treatment option.

RECENT FINDINGS

Porcine xenografts at the start of the millennium were merely biologic dressings subject to rapid rejection. Since then, numerous important advances in swine to nonhuman primate models have yielded xenotransplant products at the point of clinical translation. Critical genetic modifications in swine from a designated pathogen-free donor herd have allowed xenograft survival reaching 30 days without preconditioning or maintenance immunosuppression. Further, xenograft coverage appears not to sensitize the recipient to subsequent allograft placement and vice versa, allowing for temporary coverage times to be doubled using both xeno and allografts.

SUMMARY

Studies in large animal models have led to significant progress in the creation of living, functional skin xenotransplants with clinically relevant shelf-lives to improve the management of patients with extensive burns.

Nanomedicines to Treat Skin Pathologies with Natural Molecules

The skin and mucous membranes are subjected to many disorders and pathological conditions. Nature offers a wide range of molecules with antioxidant activity able to neutralize, at least in part, the formation of free radicals and therefore to counteract the phenomena of cellular aging. Since synthetic drugs for the treatment of skin diseases can induce resistance, it is particularly interesting to use compounds of plant origin, transporting them in pharmaceutical forms capable of controlling their release and absorption. This review provides an overview of new findings about the use of lipid-based nanosystems for the delivery of natural molecules useful on the topical treatment of skin disorders. Several natural molecules encapsulated in lipid nanosystems have been considered in the treatment of some skin pathologies or diseases. Particularly, the use of rosemary and eucalyptus essential oil, saffron derivatives, curcumin, eugenol, capsaicin, thymol and lycopene has been reported. The molecules have been alternatively encapsulated in viscous systems, such as the organogels, or in liquid systems, such as ethosomes, transferosomes, solid lipid nanoparticles and monoolein based dispersions thickened by inclusion in carbomer gels. The nanostructured forms have been in vitro and in vivo investigated for the treatment of skin disorders due to dehydration, inflammation, melanoma, wound healing, fungal infections or psoriasis. The data reported in the different studies have suggested that the cutaneous application of lipid nanosystems allows a deep interaction between lipid matrix and skin strata, promoting a prolonged release and efficacy of the loaded natural molecules. This review suggests that the application of natural molecules onto the skin by lipid-based nanosystems can provide numerous clinician benefits in dermatology and cosmetics.

Injectable Enzyme-Based Hydrogel Matrix with Precisely Oxidative Stress Defense for Promoting Dermal Repair of Burn Wound

Burn wound healing remains a challenging health problem worldwide due to the lack of efficient and precise therapy. Inherent oxidative stress following burn injury is importantly responsible for prolonged inflammation, fibrotic scar, and multiple organ failure. Herein, a bioinspired antioxidative defense system coupling with in situ forming hydrogel, namely, multiresponsive injectable catechol-Fe³⁺ coordination hydrogel (MICH) matrix, is engineered to promote burn-wound dermal repair by inhibiting tissue oxidative stress. This MICH matrix serves as the special traits of "Fe-superoxide dismutases," small molecular antioxidant (vitamin E), and extracellular matrix (ECM) in alleviating cellular oxidative damage, which demonstrates precise scavenging on reactive oxygen species (ROS) of different cellular locations, blocking lipid peroxidation and cell apoptosis. In in vivo burn-wound treatment, this MICH promptly integrates with injured surrounding tissue to provide hydration microenvironment and physicochemical ECM for burn wounds. Importantly, the MICH matrix suppresses tissue ROS production, reducing the inflammatory response, prompting re-epithelization and neoangiogenesis during wound healing. Meanwhile, the remodeling skin treated with MICH matrix demonstrates low collagen deposition and normal dermal collagen architecture. Overall, the MICH prevents burn wound progression and enhances skin regeneration, which might be a promising biomaterial for burn-wound care and other disease therapy induced by oxidative stress.

Relationship Between Patient Characteristics and Number of Procedures as well as Length of Stay for Patients Surviving Severe Burn Injuries: Analysis of the American Burn Association National Burn Repository

This study establishes important, national benchmarks for burn centers to assess length of stay (LOS) and number of procedures across patient profiles. We examined the relationship between patient characteristics such as age and total body surface area (TBSA) burned and number of procedures and LOS in the United States, using the American Burn Association National Burn Repository (NBR) database version 8.0 (2002–2011). Among 21,175 surviving burn patients (TBSA > 10–60%), mean age was 33 years, and mean injury size was 19.9% TBSA. Outcomes included the number of debridement, excision, autograft procedures, and LOS. Independent variables considered were: age (linear, squared, and cubed to account for nonlinearity), TBSA, TBSAs of partial-thickness and mixed/full-thickness burns, sex, hospital-acquired infection, other infection, inhalation injury, and diabetes status. Regression methods included a mixed-effects model for LOS and ordinary least squares for number of procedures. A backward stepwise procedure (P <0.2) was used to select variables. Number of excision and autografting procedures increased with TBSA; however, this relationship did not hold for debridement. After adjusting for sex, age, and comorbidities, predicted LOS for adults (18+) was 12.1, 21.7, 32.2, 43.7, and 56.1 days for 10, 20, 30, 40, and 50% TBSA, respectively. Similarly, predicted LOS for pediatrics (age < 18) was 8.1, 18.8, 33.2, 47.6, and 56.1 days for the same TBSA groups, respectively. While average estimates for adults (1.12 days) and pediatrics (1.01) are close to the one day/TBSA rule-of-thumb, consideration of other important patient and burn features in the NBR can better refine predictions for LOS.

Antibiotic Delivery Strategies to Treat Skin Infections When Innate Antimicrobial Defense Fails

The epidermal skin barrier protects the body from a host of daily challenges, providing protection against mechanical insults and the absorption of chemicals and xenobiotics. In addition to the physical barrier, the epidermis also presents an innate defense against microbial overgrowth. This is achieved through the presence of a diverse collection of microorganisms on the skin (the "microbiota") that maintain a delicate balance with the host and play a significant role in overall human health. When the skin is wounded, the local tissue with a compromised barrier can become colonized and ultimately infected if bacterial growth overcomes the host response. Wound infections present an immense burden in healthcare costs and decreased quality of life for patients, and treatment becomes increasingly important because of the negative impact that infection has on slowing the rate of wound healing. In this review, we discuss specific challenges of treating wound infections and the advances in drug delivery platforms and formulations that are under development to improve topical delivery of antimicrobial treatments.

CD163 overexpression using a macrophage-directed gene therapy approach improves wound healing in ex vivo and in vivo human skin models

Large tissue damage or wounds cause serious comorbidities and represent a major burden for patients, families, and health systems. Due to the pivotal role of immune cells in the proper resolution of inflammation and tissue repair, we focus our current study on the interaction of macrophages with skin cells, and specifically on the effects of CD163 gene induction in macrophages in wound healing. We hypothesize that the over-expression of the scavenger receptor gene CD163 in human macrophages would result in a more efficient wound healing process. Using 3D human wounded skin organotypic tissues, we observed that CD163 overexpression in THP-1 and human primary macrophages induced a more efficient re-epithelization when compared to control cells. Using human primary skin cells and an in vitro scratch assay we observed that CD163 overexpression in THP-1 macrophages promoted a more rapid and efficient wound healing process through a unique interaction with fibroblasts. The addition of CD163-blocking antibody, but not isotype control, blocked the efficient wound healing process induced by CD163 overexpression in macrophages. We found that the co-culture of skin cells and CD163 overexpressing macrophages reduced monocyte chemoattractant protein (MCP)-1 and enhanced tumor growth factor (TGF)-α, without altering interleukin (IL)-6 or TGF-β. Our findings show that CD163 induces a more efficient wound healing and seems to promote a wound milieu with a pro-resolution molecular profile. Our studies set the foundation to study this approach in in vivo clinically relevant settings to test its effects in wound healing processes such as acute major injuries, large surgeries, or chronic ulcers.

Spatial frequency domain imaging: a quantitative, noninvasive tool for in vivo monitoring of burn wound and skin graft healing

There is a need for noninvasive, quantitative methods to characterize wound healing in the context of longitudinal investigations related to regenerative medicine. Such tools have the potential to inform the assessment of wound status and healing progression and aid the development of new treatments. We employed spatial frequency domain imaging (SFDI) to characterize the changes in optical properties of tissue during wound healing progression in a porcine model of split-thickness skin grafts and also in a model of burn wound healing with no graft intervention. Changes in the reduced scattering coefficient measured using SFDI correlated with structural changes reported by histology of biopsies taken concurrently. SFDI was able to measure spatial inhomogeneity in the wounds and predicted heterogeneous healing. In addition, we were able to visualize differences in healing rate, depending on whether a wound was debrided and grafted, versus not debrided and left to heal without intervention apart from topical burn wound care. Changes in the concentration of oxy- and deoxyhemoglobin were also quantified, giving insight into hemodynamic changes during healing.

PEG-Plasma Hydrogels Increase Epithelialization Using a Human Ex Vivo Skin Model

In vitro cell culture methods are used extensively to study cellular migration, proliferation, and differentiation, which play major roles in wound healing but the results often do not translate to the in vivo environment. One alternative would be to establish an ex vivo model utilizing human discarded skin to evaluate therapies in a more natural setting. The purpose of this study was to institute such a model by creating ‘wounds’ in the center of a piece of discarded skin and treating them with three different biomaterials: collagen, polyethylene glycol (PEG)-fibrin, or PEG-platelet free plasma (PFP). Explants were cultured for 14 days with supernatant and microscopy images collected every 3 days to assess cytotoxicity and epithelialization. After 14 days, the explants were fixed, sectioned, and stained for cytokeratin-10 (CK-10), alpha-smooth muscle actin (α-SMA), and wheat germ (WG). Compared to controls, similar levels of cytotoxicity were detected for 12 days which decreased slightly at day 14. The PEG-PFP hydrogel-treated wounds epithelialized faster than other treatments at days 6 to 14. A 6-8 cell layer thick CK-10+ stratified epidermis had developed over the PEG-PFP hydrogel and cells co-stained by WG and α-SMA were observed within the hydrogel. An ex vivo model was established that can be used practically to screen different therapies exploring wound healing.