What's new in burns and metabolism

Current and Emerging Topical Scar Mitigation Therapies for Craniofacial Burn Wound Healing

Burn injury in the craniofacial region causes significant health and psychosocial consequences and presents unique reconstructive challenges. Healing of severely burned skin and underlying soft tissue is a dynamic process involving many pathophysiological factors, often leading to devastating outcomes such as the formation of hypertrophic scars and debilitating contractures. There are limited treatment options currently used for post-burn scar mitigation but recent advances in our knowledge of the cellular and molecular wound and scar pathophysiology have allowed for development of new treatment concepts. Clinical effectiveness of these experimental therapies is currently being evaluated. In this review, we discuss current topical therapies for craniofacial burn injuries and emerging new therapeutic concepts that are highly translational.

Anabolic and anticatabolic agents used in burn care: What is known and what is yet to be learned

Major thermal injury induces profound metabolic derangements secondary to an inflammatory "stress-induced" hormonal environment. Several pharmacological interventions have been tested in an effort to halt the hypermetabolic response to severe burns. Insulin, insulin growth factor 1, insulin growth factor binding protein 3, metformin, human growth hormone, thyroid hormones, testosterone, oxandrolone, and propranolol, among others, have been proposed to have anabolic or anticatabolic effects. The aim of this broad analysis of pharmacological interventions was to raise awareness of treatment options and to help establishing directions for future clinical research efforts. A PubMed search was conducted on the anabolic and anticatabolic agents used in burn care. One hundred and thirty-five human studies published between 1999 and 2017 were included in this review. The pharmacological properties, rationale for the treatments, efficacy considerations and side effect profiles are summarized in the article. Many of the drugs tested for investigational purposes in the severely thermally injured are not yet gold-standard therapies in spite of their potential benefit. Propranolol and oxandrolone have shown great promise but further evidence is still needed to clarify their potential use for anabolic and anticatabolic purposes.

Effect of N-(2-aminoethyl) ethanolamine on hypertrophic scarring changes in vitro: Finding novel anti-fibrotic therapies

Hypertrophic scars (HS) limit movement, decrease quality of life, and remain a major impediment to rehabilitation from burns. However, no effective pharmacologic therapies for HS exist. Here we tested the in vitro anti-fibrotic effects of the novel chemical N-(2-aminoethyl) ethanolamine (AEEA) at non-toxic concentrations. Scanning electron microscopy showed that AEEA markedly altered the structure of the extracellular matrix (ECM) produced by primary dermal fibroblasts isolated from a HS of a burn patient (HTS). Compression atomic force microscopy revealed that AEEA stiffened the 3D nanostructure of ECM formed by HTS fibroblasts. Western blot analysis in three separate types of primary human dermal fibroblasts (including HTS) showed that AEEA exposure increased the extractability of type I collagen in a dose- and time-dependent fashion, while not increasing collagen synthesis. A comparison of the electrophoretic behavior of the same set of samples under native and denaturing conditions suggested that AEEA alters the 3D structure of type I collagen. The antagonization effect of AEEA to TGF-β1 on ECM formation was also observed. Furthermore, analyses of the anti-fibrotic effects of analogs of AEEA (with modified pharmacophores) suggest the existence of a chemical structure-activity relationship. Thus, AEEA and its analogs may inhibit HS development; further study and optimization of analogs may be a promising strategy for the discovery for effective HS therapies.

Establishment and assessment of new formulas for energy consumption estimation in adult burn patients

OBJECTIVE

An accurate knowledge of energy consumption in burn patients is a prerequisite for rational nutrition therapy. This study sought to create a formula that accounts for the metabolic characteristics of adult burn patients to accurately estimate energy consumption of patients with different areas and extents of burn and at different times after injury.

METHODS

Resting energy expenditure (REE) data on 66 burn patients, with total body surface area (TBSA) of burns ranging from 4% to 96%, were evaluated at different times after injury. REE values were determined in patients using indirect calorimetry at days 1, 2, 3, 7, 14, 21, and 28 after injury. We then constructed a mathematical model of REE changes post-burn. Next, established two new formulas (one non-linear and the other linear) for energy consumption estimation using model-based analytical solution and regression analysis. The new formulas were compared with measured REE and commonly used formulas including those of Carlson, Xie, Curreri, and Milner to determine accuracy and reliability.

RESULTS

Comparative analysis showed that the new formulas offered significantly higher accuracy and reliability than the Milner formula, which is considered the most accurate of commonly used burn energy consumption estimate formulas. The accuracy of the new nonlinear formula (94.29%) and that of the linear formula (91.43%) were significantly higher than that of Milner formula (72.86%) when compared to measured REE (χ2  =  11.706, P  =  0.001; χ2  =  8.230, P  =  0.004, respectively). The reliabilities of the new estimation formulas were both 100% and that of Milner formula was 74.24% (χ2  =  19.513, P  =  0.000).

CONCLUSION

The new formulas constructed in this study provide reliable simulation of the impact of the degree of burn and post-burn days on energy consumption and offer notably higher accuracy and reliability than other formulas. These formulas will help determine nutritional needs of burn patients.

TRIAL REGISTRATION

The study was registered on Chinese Clinical Trial Registry as ChiCTR-TRC-13003806.

Mitochondria-targeted antioxidant promotes recovery of skeletal muscle mitochondrial function after burn trauma assessed by in vivo 31P nuclear magnetic resonance and electron paramagnetic resonance spectroscopy

Burn injury causes a major systemic catabolic response that is associated with mitochondrial dysfunction in skeletal muscle. We investigated the effects of the mitochondria-targeted peptide antioxidant Szeto-Schiller 31 (SS-31) on skeletal muscle in a mouse burn model using in vivo phosphorus-31 nuclear magnetic resonance ((31)P NMR) spectroscopy to noninvasively measure high-energy phosphate levels; mitochondrial aconitase activity measurements that directly correlate with TCA cycle flux, as measured by gas chromatography mass spectrometry (GC-MS); and electron paramagnetic resonance (EPR) to assess oxidative stress. At 6 h postburn, the oxidative ATP synthesis rate was increased 5-fold in burned mice given a single dose of SS-31 relative to untreated burned mice (P=0.002). Furthermore, SS-31 administration in burned animals decreased mitochondrial aconitase activity back to control levels. EPR revealed a recovery in redox status of the SS-31-treated burn group compared to the untreated burn group (P<0.05). Our multidisciplinary convergent results suggest that SS-31 promotes recovery of mitochondrial function after burn injury by increasing ATP synthesis rate, improving mitochondrial redox status, and restoring mitochondrial coupling. These findings suggest use of noninvasive in vivo NMR and complementary EPR offers an approach to monitor the effectiveness of mitochondrial protective agents in alleviating burn injury symptoms.

The IL-6 trans-signaling-STAT3 pathway mediates ECM and cellular proliferation in fibroblasts from hypertrophic scar

The molecular mechanisms behind the pathogenesis of post-burn hypertrophic scar (HS) remain unclear. Here, we investigate the role of interleukin-6 (IL-6) trans-signaling-STAT3 pathway in HS fibroblasts (HSF) derived from burned-induced HS skin. HSF showed increased Tyr 705 STAT3 phosphorylation over normal fibroblast (NF) after IL-6•IL-6Rα stimulation by immunoassays. The endogenous STAT3 target gene, SOCS3, was upregulated in HSF and showed increased STAT3 binding on its promoter relative to NF in Chromatin Immunoprecipitation assay. We observed that the cell surface signaling transducer glycoprotein 130 is upregulated in HSF using Q-RT-PCR and flow cytometry. The production of excessive extracellular matrix (ECM), including the expression of alpha2 (1) procollagen (Col1A2) and fibronectin 1 (FN) were seen in HSFs. A STAT3 peptide inhibitor abrogated FN and Col1A2 gene expression in HSF indicating involvement of STAT3 in ECM production. The cellular proliferation markers Cyclin D1, Bcl-Xl and c-Myc were also upregulated in HSF and knockdown of STAT3 by siRNA attenuated c-Myc expression indicating the essential role of STAT3 in fibroblast proliferation. Taken together, our results suggest that the IL-6-trans-signaling-STAT3 pathway may play an integral role in HS pathogenesis and disruption of this pathway could be a potential therapeutic strategy for the treatment of burn-induced HS.

Pharmacological blockade of adenosine A2A receptors diminishes scarring

Adenosine A2A receptor (A2AR) stimulation promotes wound healing and is required for the development of fibrosis in murine models of scleroderma and cirrhosis. Nonetheless, the role of A2AR in the formation of scars following skin trauma has not been explored. Here, we examined the effect of pharmacological blockade of A2AR, with the selective adenosine A2AR-antagonist ZM241385 (2.5 mg/ml), in a murine model of scarring that mimics human scarring. We found that application of the selective adenosine A2AR antagonist ZM241385 decreased scar size and enhanced the tensile strength of the scar. Within the scar itself, collagen alignment and composition (marked reduction in collagen 3), but not periostin, biglycan, or fibronectin accumulation, was improved by application of ZM241385. Moreover, A2AR blockade reduced the number of myofibroblasts and angiogenesis but not macrophage infiltration in the scar. Taken together, our work strongly suggests that pharmacological A2AR blockade can be used to diminish scarring while improving the collagen composition and tensile strength of the healed wound.

Tissue-engineered provisional matrix as a novel approach to enhance diabetic wound healing

Inherent pathologies associated with diabetic wound microenvironment including increased proteolysis, inflammatory dysregulation, and impaired neovascularization prevent timely resolution of chronic diabetic ulcers. It is hypothesized that augmentation of local wound microenvironment with a stable provisional matrix formed by proteolysis-resistant angiogenic peptide nanofibers (NFs) will create permissive environment for attenuated inflammation, enhanced neovascularization, and improved diabetic wound healing. Using murine excisional wound healing models, full-thickness dorsal skin wounds were treated with either NFs or control solutions (phosphate buffered saline; hyaluronic acid) and analyzed for morphology, inflammatory response, neovascularization, and biomechanical properties. NF treatment of diabetic wounds stimulated formation of a robust pro-angiogenic in situ tissue-engineered provisional matrix leading to a significant decrease in wound inflammatory cell infiltration and proinflammatory interleukin-6 levels, a significant increase in endothelial and endothelial progenitor cell infiltration, vascular endothelial growth factor levels, and neovascularization (day 7), as well as improved wound morphology, accelerated wound closure, and significantly stronger repair tissue (day 28). These results suggest that appropriate design of provisional matrix may compensate for some of the complex disruptions in diabetic wound microenvironment and provide missing cues to cells and direct in situ responses toward improved healing, which is promising for future development of new therapies for diabetic ulcers.

Current concepts in scar evolution and control

The basic principles influencing scar expression and outcome have long been defined. Although these were relatively clear at the time, the exact events at a molecular level were poorly defined. The past decade has delineated the myriad of events that occur in the run-up to scar evolution far more clearly, although the intricate details have yet to be elucidated. What is clear is that a series of conversations and crosstalk takes place in the cell cytosol, in the cellular nucleus, and outside the cell within in the extracellular matrix. This interaction or "dynamic reciprocity" takes place via a series of signals, protein activation, ionic translocations, and receptor transactions. Marrying the previously defined principles with current described cellular/extracellular matrix (ECM) interactions enables us to describe more accurately the crosstalk occurring in scar evolution and possibly to influence the "wording" of that crosstalk to improve scar outcome. Thus, the principles of mechanostimulation and scar support, hydration occlusion, controlled inflammation, and collagen/extracellular remodeling are discussed with possible interventions in each category.

Cellular/extracellular matrix cross-talk in scar evolution and control

The principles of scar evolution and control are recognized and defined. Further clarity has been shed on these principles with the elucidation and elaboration of the sequence of events occurring at a molecular level. Cellular cross-talk among structures in the cell cytosol, in the cellular nucleus, and outside the cell within in the extracellular matrix is continuous and controlling in nature. This interaction or "dynamic reciprocity" takes place via a series of signals, ionic messenger shifts, protein activation, and receptor transactions. The described principles are now able to be defined in terms of cellular/extracellular matrix interactions and the identification of the cross-talk involved in scar evolution and maturation presents the possibility of influencing the "wording" of this cross-talk to improve scar outcome. The principles of mechanostimulation and scar support, hydration occlusion, controlled inflammation, and collagen/extracellular remodeling are discussed with possible interventions in each category.

How to assess scar hypertrophy--a comparison of subjective scales and Spectrocutometry: a new objective method

Scar hypertrophy is a significant clinical problem involving both linear scars from elective surgery and scars caused by trauma or burns. The treatment of hypertrophic scars is often time consuming, and patients may need to be followed up for months or even years. The methods for reliable quantification of scar hypertrophy are at present unsatisfying. We have developed a new, objective method, Spectrocutometry, for documentation and quantification of scar hypertrophy. The instrument is based on standardized digital imaging and spectral modeling and calculates the estimated concentration change of hemoglobin and melanin from the entire scar and also provides standardized images for documentation. Three plastic surgeons have assessed 37 scars from melanoma surgery using Spectrocutometry, the Vancouver scar scale, and the patient and observer scar assessment scale. The intraclass correlation coefficient for the Vancouver scar scale and the patient and observer scar assessment scale was lower than required for reliable assessment (r=0.66 and 0.60, respectively). The intraclass correlation coefficient for Spectrocutometry was high (r=0.89 and 0.88). A Bayesian network analysis revealed a strong dependency between the estimated concentration change of hemoglobin and scar pain. Spectrocutometry is a feasible method for measuring scar hypertrophy. It is shown to be more reliable than subjective rating in assessing linear surgical scars.

Systematic care management: a comprehensive approach to catastrophic injury management applied to a catastrophic burn injury population--clinical, utilization, economic, and outcome data in support of the model

The new standard for successful burn care encompasses both patient survival and the burn patient's long-term quality of life. To provide optimal long-term recovery from catastrophic injuries, including catastrophic burns, an outcome-based model using a new technology called systematic care management (SCM) has been developed. SCM provides a highly organized system of management throughout the spectrum of care that provides access to outcome data, consistent oversight, broader access to expert providers, appropriate allocation of resources, and greater understanding of total costs. Data from a population of 209 workers' compensation catastrophic burn cases with a mean TBSA of 27.9% who were managed under the SCM model of care were analyzed. The data include treatment type, cost, return to work, and outcomes achieved. Mean duration of management to achieve all guaranteed outcomes was 20 months. Of the 209 injured workers, 152 (72.7%) achieved sufficient recovery to be released to return to work, of which 97 (46.8%) were both released and competitively employed. Assessment of 10 domains of functional independence indicated that 47.2% of injured workers required total assistance at initiation of SCM. However, at termination of SCM, 84% of those injured workers were fully independent in the 10 functional activities. When compared with other burn research outcome data, the results support the value of the SCM model of care.

What's new in critical care of the burn-injured patient?

The number of cases of mortality after burn injury continues to decline, in part because of advances in respiratory, fluid, and sepsis management. However, care needs to be exercised in the application of these new techniques and technologies, many of which have never been assessed or have been incompletely studied in patients who have burn injury. Use of any of these advances in critical care needs to be individualized for any given patient and altered based on the patient's response to therapy. Future advances in the critical care of burns will require multicenter prospective trials at dedicated burn centers to define the optimal therapy for the patient who has burn injury.

Microarray analysis suggests that burn injury results in mitochondrial dysfunction in human skeletal muscle

Burn injuries to extensive areas of the body are complicated by muscle catabolism. Elucidating the molecular mechanisms that mediate this catabolism may facilitate the development of a medical intervention. Here, we assessed the functional classification of genes that were differentially expressed in skeletal muscle following burn injury in 19 children (5.2+/-4.0 years of age), (64+/-15% total burn surface area, TBSA) relative to 13 healthy controls (11.9+/-6.0 years of age). Microarray analysis of samples taken within 10 days of burn injury revealed altered expression of a variety of genes, including some involved in cell and organelle organization and biogenesis, stress response, wound response, external stimulus response, regulation of apoptosis and intracellular signaling. The genes that encode peroxisome proliferator-activated receptors (PPARs; 3 isotypes PPARalpha, PPARgamma and PPARdelta also known as PPARbeta or PPARbeta/delta), which may serve as transcriptional nodal points and therapeutic targets for metabolic syndromes, were among those affected. In particular, expression of the main mitochondrial biogenesis factor PPARgamma-1beta (or PGC-1beta) was downregulated (P<0.0001), while the expression of PPARdelta was upregulated (P<0.001). Expression of PGC-1alpha, the closest homolog of PGC-1beta was upregulated (P=0.0037), and expression of the gene encoding mitochodrial uncoupling protein 2 (UCP2) was also upregulated (P=0.008). These results suggest that altered PPAR and mitochondrial gene expression soon after burn injury may lead to metabolic and mitochondrial dysfunction in human skeletal muscle.

Nonlinear spectral imaging of human hypertrophic scar based on two-photon excited fluorescence and second-harmonic generation

BACKGROUND

A noninvasive method using microscopy and spectroscopy for analysing the morphology of collagen and elastin and their biochemical variations in skin tissue will enable better understanding of the pathophysiology of hypertrophic scars and facilitate improved clinical management and treatment of this disease.

OBJECTIVE

To obtain simultaneously microscopic images and spectra of collagen and elastin fibres in ex vivo skin tissues (normal skin and hypertrophic scar) using a nonlinear spectral imaging method, and to compare the morphological structure and spectral characteristics of collagen and elastin fibres in hypertrophic scar tissues with those of normal skin, to determine whether this approach has potential for in vivo assessment of the pathophysiology of human hypertrophic scars and for monitoring treatment responses as well as for tracking the process of development of hypertrophic scars in clinic.

METHODS

Ex vivo human skin specimens obtained from six patients aged from 10 to 50 years old who were undergoing skin plastic surgery were examined. Five patients had hypertrophic scar lesions and one patient had no scar lesion before we obtained his skin specimen. A total of 30 tissue section samples of 30 mum thickness were analysed by the use of a nonlinear spectral imaging system consisting of a femtosecond excitation light source, a high-throughput scanning inverted microscope, and a spectral imaging detection system. The high-contrast and high-resolution second harmonic generation (SHG) images of collagen and two-photon excited fluorescence (TPEF) images of elastin fibres in hypertrophic scar tissues and normal skin were acquired using the extracting channel tool of the system. The emission spectra were analysed using the image-guided spectral analysis method. The depth-dependent decay constant of the SHG signal and the image texture characteristics of hypertrophic scar tissue and normal skin were used to quantitatively assess the amount, distribution and orientation of their collagen and elastin components.

RESULTS

Our experiments and data analyses demonstrated apparent differences between hypertrophic scar tissue and normal skin in terms of their morphological structure and the spectral characteristics of collagen and elastin fibres. These differences can potentially be used to distinguish hypertrophic scar tissues from normal skin and to evaluate treatment responses.

CONCLUSIONS

All the measurements were performed in backscattering geometry and demonstrated that nonlinear spectral imaging has the ability to differentiate hypertrophic scar tissue from normal skin based on noninvasive SHG imaging, and TPEF imaging revealed the microstructure and spectral features of collagen and elastin fibres. With the advances in spectral imaging apparatus miniaturization, we have good reason to believe that this approach can become a valuable tool for the in vivo pathophysiology study of human skin hypertrophic scars and for assessing the treatment responses of this disfiguring disease in clinic. It can also be used to track the development of hypertrophic scars and to study wound healing processes in a noninvasive fashion without biopsy, fixation, sectioning and the use of exogenous dyes or stains.

Metabolic implications of severe burn injuries and their management: a systematic review of the literature

BACKGROUND

Severe burn patients are some of the most challenging critically ill patients, with an extreme state of physiologic stress and an overwhelming systemic metabolic response. A major component of severe burn injury is a hypermetabolic state associated with protein losses and a significant reduction of lean body mass. The second prominent component is hyperglycemia. Reversal of the hypermetabolic response by manipulating the patient's physiologic and biochemical environment through the administration of specific nutrients, growth factors, or other agents, often in pharmacologic doses, is emerging as an essential component of the state of the art in severe burn management. The present review aims at summarizing the new treatment modalities established to reduce the catabolic burden of severe burn injuries, for which there is some evidence-based support.

METHODS

A systematic review of the literature was conducted. Search tools included Elsevier ScienceDirect, EMBASE.com, Medline (OVID), MedlinePlus, and PubMed. Topics searched were Nutrition and Burns, Metabolic Response and Burns, Hypermetabolism and Burns, Hyperglycemia and Burns, and several more specific topics when indicated. With a focus on the most recently published articles, abstracts were reviewed and, when found relevant, were included as references. Full text articles, whenever available, were retrieved.

RESULTS

Many issues remain unanswered. Unfortunately, the present state of our knowledge does not allow the formulation of clear-cut guidelines. Only general trends can be outlined, and these will certainly have some practical applications but above all will dictate future research in the field.

Hypertrophic scar formation following burns and trauma: new approaches to treatment

The authors examine the process of hypertrophic scar formation, the results of current treatments, and areas of research likely to lead to significant advances in the field.

Mechanical load initiates hypertrophic scar formation through decreased cellular apoptosis

Hypertrophic scars occur following cutaneous wounding and result in severe functional and esthetic defects. The pathophysiology of this process remains unknown. Here, we demonstrate for the first time that mechanical stress applied to a healing wound is sufficient to produce hypertrophic scars in mice. The resulting scars are histopathologically identical to human hypertrophic scars and persist for more than six months following a brief (one-week) period of augmented mechanical stress during the proliferative phase of wound healing. Resulting scars are structurally identical to human hypertrophic scars and showed dramatic increases in volume (20-fold) and cellular density (20-fold). The increased cellularity is accompanied by a four-fold decrease in cellular apoptosis and increased activation of the prosurvival marker Akt. To clarify the importance of apoptosis in hypertrophic scar formation, we examine the effects of mechanical loading on cutaneous wounds of animals with altered pathways of cellular apoptosis. In p53-null mice, with down-regulated cellular apoptosis, we observe significantly greater scar hypertrophy and cellular density. Conversely, scar hypertrophy and cellular density are significantly reduced in proapoptotic BclII-null mice. We conclude that mechanical loading early in the proliferative phase of wound healing produces hypertrophic scars by inhibiting cellular apoptosis through an Akt-dependent mechanism.

Pediatric surgical site and soft tissue infections

OBJECTIVE

The purpose of this review is to provide background and a concise set of definitions for pediatric surgical site and wound infections.

DESIGN

The information discussed in this report is derived from a literature review and discussion at an international consensus conference on pediatric sepsis.

MEASUREMENTS AND MAIN RESULTS

There is a paucity of literature on pediatric surgical site and wound infection definitions. Excluding burn wounds, surgical site and wound infections rarely lead to overwhelming sepsis. Nevertheless, surgical site or wound infections including pressure ulcers can lead to significant morbidity in the pediatric critical care setting.

CONCLUSIONS

Although surgical site and wound infections rarely lead to intensive care unit admissions, definitions are still valuable for stratifying potential candidates for sepsis trials.

Primeiro atendimento em queimaduras: a abordagem do dermatologista

Apesar dos crescentes progressos obtidos ultimamente no tratamento dos grandes queimados, ainda são consideráveis as taxas de mortalidade e morbidade. As estratégias preventivas implementadas ainda não foram capazes de alterar significativamente o dramático quadro epidemiológico das queimaduras. Os sobreviventes de queimaduras graves ainda carregam um pesado fardo de seqüelas físicas e psicossociais que geram grande sofrimento a ser superado. Não há dúvida de que o prognóstico final de uma queimadura depende essencialmente de um pronto e adequado primeiro atendimento. Daí a importância de todo médico, inclusive o dermatologista, estar habilitado a orientar os primeiros socorros e a prestar o primeiro atendimento médico à vítima de queimadura. Este artigo procura fazer uma revisão das bases fisiopatológicas das queimaduras e dos princípios de avaliação do queimado, além de discutir de forma simples e objetiva a abordagem médica de urgência até a remoção da vítima para uma unidade de queimados, se houver indicação.