Hypertrophic scarring and keloids: pathomechanisms and current and emerging treatment strategies

Excessive scars form as a result of aberrations of physiologic wound healing and may arise following any insult to the deep dermis. By causing pain, pruritus and contractures, excessive scarring significantly affects the patient's quality of life, both physically and psychologically. Multiple studies on hypertrophic scar and keloid formation have been conducted for decades and have led to a plethora of therapeutic strategies to prevent or attenuate excessive scar formation. However, most therapeutic approaches remain clinically unsatisfactory, most likely owing to poor understanding of the complex mechanisms underlying the processes of scarring and wound contraction. In this review we summarize the current understanding of the pathophysiology underlying keloid and hypertrophic scar formation and discuss established treatments and novel therapeutic strategies.

A genomic storm in critically injured humans

Critical injury in humans induces a genomic storm with simultaneous changes in expression of innate and adaptive immunity genes.

Human survival from injury requires an appropriate inflammatory and immune response. We describe the circulating leukocyte transcriptome after severe trauma and burn injury, as well as in healthy subjects receiving low-dose bacterial endotoxin, and show that these severe stresses produce a global reprioritization affecting >80% of the cellular functions and pathways, a truly unexpected “genomic storm.” In severe blunt trauma, the early leukocyte genomic response is consistent with simultaneously increased expression of genes involved in the systemic inflammatory, innate immune, and compensatory antiinflammatory responses, as well as in the suppression of genes involved in adaptive immunity. Furthermore, complications like nosocomial infections and organ failure are not associated with any genomic evidence of a second hit and differ only in the magnitude and duration of this genomic reprioritization. The similarities in gene expression patterns between different injuries reveal an apparently fundamental human response to severe inflammatory stress, with genomic signatures that are surprisingly far more common than different. Based on these transcriptional data, we propose a new paradigm for the human immunological response to severe injury.

Burn injury

Burn injuries are under-appreciated injuries that are associated with substantial morbidity and mortality. Burn injuries, particularly severe burns, are accompanied by an immune and inflammatory response, metabolic changes and distributive shock that can be challenging to manage and can lead to multiple organ failure. Of great importance is that the injury affects not only the physical health, but also the mental health and quality of life of the patient. Accordingly, patients with burn injury cannot be considered recovered when the wounds have healed; instead, burn injury leads to long-term profound alterations that must be addressed to optimize quality of life. Burn care providers are, therefore, faced with a plethora of challenges including acute and critical care management, long-term care and rehabilitation. The aim of this Primer is not only to give an overview and update about burn care, but also to raise awareness of the ongoing challenges and stigmata associated with burn injuries.

Long-term persistance of the pathophysiologic response to severe burn injury

Background

Main contributors to adverse outcomes in severely burned pediatric patients are profound and complex metabolic changes in response to the initial injury. It is currently unknown how long these conditions persist beyond the acute phase post-injury. The aim of the present study was to examine the persistence of abnormalities of various clinical parameters commonly utilized to assess the degree hypermetabolic and inflammatory alterations in severely burned children for up to three years post-burn to identify patient specific therapeutic needs and interventions.

Methodology/Principal Findings

Patients: Nine-hundred seventy-seven severely burned pediatric patients with burns over 30% of the total body surface admitted to our institution between 1998 and 2008 were enrolled in this study and compared to a cohort non-burned, non-injured children. Demographics and clinical outcomes, hypermetabolism, body composition, organ function, inflammatory and acute phase responses were determined at admission and subsequent regular intervals for up to 36 months post-burn. Statistical analysis was performed using One-way ANOVA, Student's t-test with Bonferroni correction where appropriate with significance accepted at p<0.05. Resting energy expenditure, body composition, metabolic markers, cardiac and organ function clearly demonstrated that burn caused profound alterations for up to three years post-burn demonstrating marked and prolonged hypermetabolism, p<0.05. Along with increased hypermetabolism, significant elevation of cortisol, catecholamines, cytokines, and acute phase proteins indicate that burn patients are in a hyperinflammatory state for up to three years post-burn p<0.05.

Conclusions

Severe burn injury leads to a much more profound and prolonged hypermetabolic and hyperinflammatory response than previously shown. Given the tremendous adverse events associated with the hypermetabolic and hyperinflamamtory responses, we now identified treatment needs for severely burned patients for a much more prolonged time.

Hypertrophic scarring: the greatest unmet challenge after burn injury

Improvements in acute burn care have enabled patients to survive massive burns that would have once been fatal. Now up to 70% of patients develop hypertrophic scars after burns. The functional and psychosocial sequelae remain a major rehabilitative challenge, decreasing quality of life and delaying reintegration into society. Approaches to optimise healing potential of burn wounds use targeted wound care and surgery to minimise the development of hypertrophic scarring. Such approaches often fail, and modulation of the established scar is continued although the optimal indication, timing, and combination of therapies have yet to be established. The need for novel treatments is paramount, and future efforts to improve outcomes and quality of life should include optimisation of wound healing to attenuate or prevent hypertrophic scarring, well-designed trials to confirm treatment efficacy, and further elucidation of molecular mechanisms to allow development of new preventive and therapeutic strategies.

Emerging infections in burns

BACKGROUND

Patients who suffer severe burns are at higher risk for local and systemic infections. In recent years, emerging resistant pathogens have forced burn care providers world wide to search for alternative forms of treatment. Multidrug-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter spp., and various fungal strains have been the major contributors to the increase in morbidity and mortality rates. Multi-drug-resistant S. aureus remains the major cause of gram-positive burn wound infections world wide. Treatment strategies include rigorous isolation protocols and new types of antibiotics where necessary.

METHODS

We reviewed 398 severely burned patients (burns >40% total body surface area [TBSA]) admitted to our hospital between 2000 and 2006. Patients who did not contract multi-drug-resistant gram-negative organisms during their hospital course and received our standard antibiotic regimen-vancomycin and piperacillin/tazobactam-served as controls (piperacillin/tazobactam; n = 280). The treatment group consisted of patients who, during their acute hospital stay, developed infections with multi-drug-resistant gram-negative pathogens and were treated with vancomycin and colistin for at least three days (colistin; n = 118).

RESULTS

Gram-negative organisms continue to cause the most severe infections in burn patients. Colistin has re-emerged as a highly effective antibiotic against multiresistant Pseudomonas and Acinetobacter infections of burns. Patients who required colistin therapy had a significantly larger average total and full-thickness burn than patients treated with piperacillin/tazobactam and vancomycin, and the mortality rate was significantly higher in the colistin group (p < 0.05). However, there was no significant difference between the colistin and piperacillin/tazobactam groups in the incidence of neurotoxicity, hepatic toxicity, or nephrotoxicity. The main fungal pathogens in burn patients are Candida spp., Aspergillus spp., and Fusarium spp. A definitive diagnosis is more difficult to obtain than in bacterial infections. Amphotericin B and voriconazole remain the two most important anti-fungal substances in our practice.

CONCLUSIONS

Innovations in fluid management, ventilatory support, surgical care, and antimicrobial therapy have contributed to a significant reduction in morbidity and mortality rates in burn patients. Vancomycin and clindamycin are the two most important reserve antibiotics for methicillin-resistant Staphylococcus aureus infection. Oxazolidinones and streptogramins have showed high effectiveness against gram-positive infections. Colistin has re-emerged as a highly effective antibiotic against multiresistant Pseudomonas and Acinetobacter infections. Current challenges include Candida, Aspergillus, and molds. The development of new agents, prudent and appropriate use of antibiotics, and better infection control protocols are paramount in the ongoing battle against multi-resistant organisms.

The leading causes of death after burn injury in a single pediatric burn center

INTRODUCTION

Severe thermal injury is characterized by profound morbidity and mortality. Advances in burn and critical care, including early excision and grafting, aggressive resuscitation and advances in antimicrobial therapy have made substantial contributions to decrease morbidity and mortality. Despite these advances, death still occurs. Our aim was to determine the predominant causes of death in burned pediatric patients in order to develop new treatment avenues and future trajectories associated with increased survival.

METHODS

Primary causes of death were reviewed from 144 pediatric autopsy reports. Percentages of patients that died from anoxic brain injuries, sepsis, or multi-organ failure were calculated by comparing to the total number of deaths. Data was stratified by time (from 1989 to 1999, and 1999 to 2009), and gender. Statistical analysis was done by chi-squared, Student's t-test and Kaplan-Meier for survival where applicable. Significance was accepted as P < 0.05.

RESULTS

Five-thousand two-hundred-sixty patients were admitted after burn injury from July 1989 to June 2009, and of those, 145 patients died after burn injury. Of these patients, 144 patients had an autopsy. The leading causes of death over 20 years were sepsis (47%), respiratory failure (29%), anoxic brain injury (16%), and shock (8%). From 1989 to 1999, sepsis accounted for 35% of deaths but increased to 54% from 1999 to 2009, with a significant increase in the proportion due to antibiotic resistant organisms (P < 0.05).

CONCLUSIONS

Sepsis is the leading cause of death after burn injury. Multiple antibiotic resistant bacteria now account for the bulk of deaths due to sepsis. Further improvement in survival may require improved strategies to deal with this problem.

Cytokine expression profile over time in severely burned pediatric patients

A severe burn leads to hypermetabolism and catabolism resulting in compromised function and structure of essential organs. The massive release of cytokines is implicated in this hypermetabolic response. The aim of the present study was to compare cytokine expression profiles from severely burned children without signs of infections or inhalation injury (n = 19) to the cytokine profiles from normal, noninfected, nonburned children (n = 14). The Bio-Plex suspension array system was used to measure the concentration of 17 cytokines. The expression of proinflammatory and anti-inflammatory cytokines was maximal during the first week after thermal injury. Significant increases were measured for 15 mediators during the first week after thermal injury: interleukin (IL) 1beta, IL-2, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12 p70, IL-13, IL-17, interferon gamma, monocyte chemoattractant protein 1, macrophage inflammatory protein 1beta, and granulocyte colony-stimulating factor (P < 0.05). Granulocyte-macrophage colony-stimulating factor was significantly increased during the second week after burn (P < 0.05). Within 5 weeks, the serum concentrations of most cytokines decreased, approaching normal levels. When compared with the cytokine levels measured in normal children, a total of 16 cytokines were significantly altered (P < 0.05). After severe burn, a specific cytokine expression profile is observed in patients without complications such as inhalation injury or sepsis. The cytokine concentrations decrease during 5 weeks after burn but remain elevated over nonburned values. Furthermore, the elevation in most serum cytokine levels during the first week after burn may indicate a potential window of opportunity for therapeutic intervention.

Burn size determines the inflammatory and hypermetabolic response

Background

Increased burn size leads to increased mortality of burned patients. Whether mortality is due to inflammation, hypermetabolism or other pathophysiologic contributing factors is not entirely determined. The purpose of the present study was to determine in a large prospective clinical trial whether different burn sizes are associated with differences in inflammation, body composition, protein synthesis, or organ function.

Methods

Pediatric burned patients were divided into four burn size groups: <40% total body surface area (TBSA) burn, 40–59% TBSA burn, 60–79% TBSA burn, and >80% TBSA burn. Demographic and clinical data, hypermetabolism, the inflammatory response, body composition, the muscle protein net balance, serum and urine hormones and proteins, and cardiac function and changes in liver size were determined.

Results

One hundred and eighty-nine pediatric patients of similar age and gender distribution were included in the study (<40% TBSA burn, n = 43; 40–59% TBSA burn, n = 79; 60–79% TBSA burn, n = 46; >80% TBSA burn, n = 21). Patients with larger burns had more operations, a greater incidence of infections and sepsis, and higher mortality rates compared with the other groups (P < 0.05). The percentage predicted resting energy expenditure was highest in the >80% TBSA group, followed by the 60–79% TBSA burn group (P < 0.05). Children with >80% burns lost the most body weight, lean body mass, muscle protein and bone mineral content (P < 0.05). The urine cortisol concentration was highest in the 80–99% and 60–79% TBSA burn groups, associated with significant myocardial depression and increased change in liver size (P < 0.05). The cytokine profile showed distinct differences in expression of IL-8, TNF, IL-6, IL-12p70, monocyte chemoattractant protein-1 and granulocyte–macrophage colony-stimulating factor (P < 0.05).

Conclusion

Morbidity and mortality in burned patients is burn size dependent, starts at a 60% TBSA burn and is due to an increased hypermetabolic and inflammatory reaction, along with impaired cardiac function.

A review of gene and stem cell therapy in cutaneous wound healing

Different therapies that effect wound repair have been proposed over the last few decades. This article reviews the emerging fields of gene and stem cell therapy in wound healing. Gene therapy, initially developed for treatment of congenital defects, is a new option for enhancing wound repair. In order to accelerate wound closure, genes encoding for growth factors or cytokines showed the greatest potential. The majority of gene delivery systems are based on viral transfection, naked DNA application, high pressure injection, or liposomal vectors. Embryonic and adult stem cells have a prolonged self-renewal capacity with the ability to differentiate into various tissue types. A variety of sources, such as bone marrow, peripheral blood, umbilical cord blood, adipose tissue, skin and hair follicles, have been utilized to isolate stem cells to accelerate the healing response of acute and chronic wounds. Recently, the combination of gene and stem cell therapy has emerged as a promising approach for treatment of chronic and acute wounds.

Infection in Burns

BACKGROUND

Developments in critical care and surgical approaches to treating burn wounds, together with newer antimicrobial treatments, have significantly reduced the morbidity and mortality rates associated with this injury.

METHODS

Review of the pertinent English-language literature.

RESULTS

Several resistant organisms have emerged as the maleficent cause of invasive infection in burn patients, including methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus, Pseudomonas, Acinetobacter, non-albicans Candida spp., and Aspergillus. Advances in antimicrobial therapies and the release of new classes of antibiotics have certainly added to the armamentarium of therapeutic resources for the clinician.

CONCLUSION

Strict infection control measures, constant wound surveillance with regular sampling of tissues for quantitative culture, and early excision and wound closure remain the principal adjuncts to control of invasive infections in burn patients.

Insulin treatment improves the systemic inflammatory reaction to severe trauma

OBJECTIVE

Determine the effect of insulin on the systemic inflammatory response, pro- and anti-inflammatory cytokines and hepatic acute-phase-response in severely burned pediatric patients.

SUMMARY BACKGROUND DATA

The systemic inflammatory and hepatic acute-phase-response contribute to hypermetabolism, multi-organ failure, and mortality. Insulin has been recently shown to decrease mortality and to prevent the incidence of multi-organ failure in critically ill patients; however, the underlying mechanisms have not been defined.

METHODS

Thirteen thermally injured children received insulin to maintain blood glucose at a range from 120 to 180 mg/dl, 15 children received no insulin with blood glucose levels also at range from 120 to 180 mg/dl and served as controls. Our outcome measures encompassed the effect of insulin on pro-inflammatory mediators, the hepatic acute-phase-response, fat, and the IGF-I system.

RESULTS

Insulin administration decreased pro-inflammatory cytokines and proteins, while increasing constitutive-hepatic proteins (P < 0.05). Burned children receiving insulin required significantly less albumin substitution to maintain normal levels compared with control (P < 0.05). Insulin decreased free fatty acids and serum triglycerides when compared with controls (P < 0.05). Serum IGF-I and IGFBP-3 significantly increased with insulin administration (P < 0.05).

CONCLUSION

Insulin attenuates the inflammatory response by decreasing the pro-inflammatory and increasing the anti-inflammatory cascade, thus restoring systemic homeostasis, which has been shown critical for organ function and survival in critically ill patients.

The hypermetabolic response to burn injury and interventions to modify this response

Severe burn injury is followed by a profound hypermetabolic response that persists up to 24 months after injury. It is mediated by up to 50-fold elevations in plasma catecholamines, cortisol, and inflammatory cells that lead to whole-body catabolism, elevated resting energy expenditures, and multiorgan dysfunction. All of these metabolic and physiologic derangements prevent full rehabilitation and acclimatization of burn survivors back into society. Modulation of the response by early excision and grafting of burn wounds, thermoregulation, early and continuous enteral feeding with high-protein high-carbohydrate feedings, and pharmacologic treatments have markedly decreased morbidity.

Insulin attenuates the systemic inflammatory response in endotoxemic rats

Insulin decreases the mortality and prevents the incidence of infection and sepsis in critically ill patients. The molecular and cellular mechanisms by which insulin improves survival have not been defined. The purpose of the present study was to determine the effect of insulin on the inflammatory reaction during endotoxemia. Endotoxemic rats were randomly divided into two groups to receive either saline or insulin. The effects of insulin on hepatic signal transcription factor mRNA expression, proinflammatory and antiinflammatory cytokine mRNA and protein concentration were determined. Insulin administration did not change glucose or electrolyte levels, but significantly decreased proinflammatory signal transcription factors [CCAAT/enhancer-binding protein-beta, signal transducer and activator of transcription-3 and-5, RANTES (regulated on activation, normal T cell expressed and secreted)] and cytokine expression in the liver and serum levels of IL-1beta, IL-6, macrophage inflammatory factor, and TNFalpha. Insulin administration further decreased high mobility group 1 protein in the serum compared with controls. In addition, insulin increased antiinflammatory cytokine expression in the liver; serum levels of IL-2, IL-4, and IL-10; and hepatic suppressor of cytokine signaling-3 mRNA expression. Insulin modulates the inflammatory response by decreasing the proinflammatory and increasing the antiinflammatory cascade. Because glucose and electrolyte levels did not differ between insulin-treated patients and controls, we hypothesize that the effects are direct antiinflammatory mechanisms of insulin, rather than indirect, through modulation of glucose or electrolyte metabolism.

Burn Induces Browning of the Subcutaneous White Adipose Tissue in Mice and Humans

Burn is accompanied by long-lasting immunometabolic alterations referred to as hypermetabolism that are characterized by a considerable increase in resting energy expenditure and substantial whole-body catabolism. In burned patients, the length and magnitude of the hypermetabolic state is the highest of all patients and associated with profoundly increased morbidity and mortality. Unfortunately, the mechanisms involved in hypermetabolism are essentially unknown. We hypothesized that the adipose tissue plays a central role for the induction and persistence of hypermetabolism post-burn injury. Here, we show that burn induces a switch in the phenotype of the subcutaneous fat from white to beige, with associated characteristics such as increased mitochondrial mass and UCP1 expression. Our results further demonstrate the significant role of catecholamines and interleukin-6 in this process. We conclude that subcutaneous fat remodeling and browning represent an underlying mechanism that explains the elevated energy expenditure in burn-induced hypermetabolism.

Intensive insulin therapy in severely burned pediatric patients: a prospective randomized trial

RATIONALE

Hyperglycemia and insulin resistance have been shown to increase morbidity and mortality in severely burned patients, and glycemic control appears essential to improve clinical outcomes. However, to date no prospective randomized study exists that determines whether intensive insulin therapy is associated with improved post-burn morbidity and mortality.

OBJECTIVES

To determine whether intensive insulin therapy is associated with improved post-burn morbidity.

METHODS

A total of 239 severely burned pediatric patients with burns over greater than 30% of their total body surface area were randomized (block randomization 1:3) to intensive insulin treatment (n = 60) or control (n = 179).

MEASUREMENTS AND MAIN RESULTS

Demographics, clinical outcomes, sepsis, glucose metabolism, organ function, and inflammatory, acute-phase, and hypermetabolic responses were determined. Demographics were similar in both groups. Intensive insulin treatment significantly decreased the incidence of infections and sepsis compared with controls (P < 0.05). Furthermore, intensive insulin therapy improved organ function as indicated by improved serum markers, DENVER2 scores, and ultrasound (P < 0.05). Intensive insulin therapy alleviated post-burn insulin resistance and the vast catabolic response of the body (P < 0.05). Intensive insulin treatment dampened inflammatory and acute-phase responses by deceasing IL-6 and acute-phase proteins compared with controls (P < 0.05). Mortality was 4% in the intensive insulin therapy group and 11% in the control group (P = 0.14).

CONCLUSIONS

In this prospective randomized clinical trial, we showed that intensive insulin therapy improves post-burn morbidity. Clinical trial registered with www.clinicaltrials.gov (NCT00673309).

Handheld skin printer: in situ formation of planar biomaterials and tissues

We present a handheld skin printer that enables the in situ formation of biomaterial and skin tissue sheets of different homogeneous and architected compositions. When manually positioned above a target surface, the compact instrument (weight <0.8 kg) conformally deposits a biomaterial or tissue sheet from a microfluidic cartridge. Consistent sheet formation is achieved by coordinating the flow rates at which bioink and cross-linker solution are delivered, with the speed at which a pair of rollers actively translate the cartridge along the surface. We demonstrate compatibility with dermal and epidermal cells embedded in ionically cross-linkable biomaterials (e.g., alginate), and enzymatically cross-linkable proteins (e.g., fibrin), as well as their mixtures with collagen type I and hyaluronic acid. Upon rapid crosslinking, biomaterial and skin cell-laden sheets of consistent thickness, width and composition were obtained. Sheets deposited onto horizontal, agarose-coated surfaces were used for physical and in vitro characterization. Proof-of-principle demonstrations for the in situ formation of biomaterial sheets in murine and porcine excisional wound models illustrate the capacity of depositing onto inclined and compliant wound surfaces that are subject to respiratory motion. We expect the presented work will enable the in situ delivery of a wide range of different cells, biomaterials, and tissue adhesives, as well as the in situ fabrication of spatially organized biomaterials, tissues, and biohybrid structures.

Temporal cytokine profiles in severely burned patients: a comparison of adults and children

A severe burn leads to hypermetabolism and catabolism resulting in compromised function and structural changes of essential organs. The release of cytokines has been implicated in this hypermetabolic response. The severity of the hypermetabolic response following burn injury increases with age, as does the mortality rate. Due to the relationship between the hypermetabolic and inflammatory responses, we sought to compare the plasma cytokine profiles following a severe burn in adults and in children. We enrolled 25 adults and 24 children who survived a flame burn covering more than 20% of total body surface area (TBSA). The concentrations of 22 cytokines were measured using the Linco multiplex array system (St. Charles, MO, USA). Large perturbations in the expression of pro- and anti-inflammatory cytokines were seen following thermal injury. During the first week following burn injury, IFN-gamma, IL-10, IL-17, IL-4, IL-6, and IL-8 were detected at significantly higher levels in adults compared with children, P < 0.05. Significant differences were measured during the second week post-burn for IL-1beta (higher in children) and IL-5 (higher in adults), P < 0.05. IL-18 was more abundant in children compared with adults during the third week post-burn, P < 0.05. Between post-burn d 21 and d 66, IL-1alpha was detected at higher concentrations in pediatric compared with adult patients, P < 0.05. Only GM-CSF expression was significantly different at all time points; it was detected at lower levels in pediatric patients, P < 0.05. Eotaxin, G-CSF, IL-13, IL-15, IP-10, MCP-1, and MIP-1alpha were detected at significantly different concentrations in adult compared with pediatric patients at multiple time points, P < 0.05. There were no differences in IL-12, IL-2, IL-7, or TNF levels in adult compared with pediatric burn patients at any of these time points. Following severe flame burns, the cytokine profiles in pediatric patients differ compared with those in adult patients, which may provide insight with respect to the higher morbidity rate in adults. Furthermore, the dramatic discrepancies observed in plasma cytokine detection between children and adults suggest that these two patient populations may benefit from different therapeutic interventions to achieve attenuation of the post-burn inflammatory response.

Abnormal insulin sensitivity persists up to three years in pediatric patients post-burn

CONTEXT

The acute hypermetabolic response post-burn is associated with insulin resistance and hyperglycemia, significantly contributing to adverse outcome of these patients.

OBJECTIVE

The aim of the study was to examine the persistence of abnormalities of various clinical parameters commonly utilized to assess the degree of insulin resistance in severely burned children for up to 3 yr after the burn injury.

DESIGN, SETTING AND PATIENTS

A total of 194 severely burned pediatric patients, admitted to our institute between 2002 and 2007, were enrolled in this prospective study and compared to a cohort of 95 nonburned, noninjured children.

MAIN OUTCOME MEASURES

Urinary cortisol, epinephrine, and norepinephrine, serum cytokines, and resting energy requirements were determined at admission and 1, 2, 6, 9, 12, 18, 24, and 36 months post-burn. A 75-g oral glucose tolerance test was performed at similar time points; serum glucose, insulin, and C-peptide were measured; and insulin sensitivity indices, such as ISI Matsuda, homeostasis model assessment, quantitative insulin sensitivity check index, and ISI Cederholm, were calculated. Statistical analysis was performed by ANOVA with Bonferroni correction with significance accepted at P < 0.05.

RESULTS

Urinary cortisol and catecholamines, serum IL-7, IL-10, IL-12, macrophage inflammatory protein-1b, monocyte chemoattractant protein-1, and resting energy requirements were significantly increased for up to 36 months post-burn (P < 0.05). Glucose values were significantly augmented for 6 months post-burn (P < 0.05), associated with significant increases in serum C-peptide and insulin that remained significantly increased for 36 months compared to nonburned children (P < 0.05). Insulin sensitivity indices, ISI Matsuda, ISI quantitative insulin sensitivity check index, and homeostasis model assessment were abnormal throughout the whole study period, indicating peripheral and whole body insulin resistance. The insulinogenic index displayed physiological values, indicating normal pancreatic beta-cell function.

CONCLUSIONS

A severe burn is associated with stress-induced insulin resistance that persists not only during the acute phase but also for up to 3 yr post-burn.

The use of dermal substitutes in burn surgery: acute phase

Major burns represent a challenge in autologous skin coverage and may lead to severe functional and cosmetic sequelae. Dermal substitutes are increasingly becoming an essential part of burn care during the acute phase of treatment. In the long term dermal substitutes improve functional and cosmetic results and thus enhance quality of life. In the chronic wound setting, dermal substitutes are used to reconstruct and improve burn scars and defects. Despite the potential of dermal substitutes, further research is required to strengthen scientific evidence regarding their effects and also to develop new technologies and products. Furthermore, dermal substitutes have a pivotal role in future research strategies as they have the potential to provide adequate scaffold for stem cells, tissue engineering, and regenerative medicine with conceivable application of obtaining long-lasting and scarless artificial skin. This review discusses the status quo of dermal substitutes and novel strategies in the use of dermal substitutes with a focus on burn care.

Biomaterials for Skin Substitutes

Patients with extensive burns rely on the use of tissue engineered skin due to a lack of sufficient donor tissue, but it is a challenge to identify reliable and economical scaffold materials and donor cell sources for the generation of a functional skin substitute. The current review attempts to evaluate the performance of the wide range of biomaterials available for generating skin substitutes, including both natural biopolymers and synthetic polymers, in terms of tissue response and potential for use in the operating room. Natural biopolymers display an improved cell response, while synthetic polymers provide better control over chemical composition and mechanical properties. It is suggested that not one material meets all the requirements for a skin substitute. Rather, a composite scaffold fabricated from both natural and synthetic biomaterials may allow for the generation of skin substitutes that meet all clinical requirements including a tailored wound size and type, the degree of burn, the patient age, and the available preparation technique. This review aims to be a valuable directory for researchers in the field to find the optimal material or combination of materials based on their specific application.

Development of new reconstructive techniques: use of Integra in combination with fibrin glue and negative-pressure therapy for reconstruction of acute and chronic wounds

Large wounds resulting from severe injuries are generally treated with extended reconstructive operations (e.g., free flaps), which are accompanied by long hospitalizations and risks of infection, thrombosis, and flap loss. Integra is a collagen template that can be used for reconstruction of defects. The take rate and the rate of infection are essential for the successful use of Integra (Johnson and Johnson, Hamburg, Germany). Whether the take rate and integration of Integra could be improved with the use of fibrin glue and negative-pressure therapy was assessed. Between January of 2002 and December of 2002, patients with large defects who underwent Integra grafting for reconstruction were randomly divided into groups receiving either a new treatment with fibrin glue-anchored Integra and postoperative negative-pressure therapy or conventional treatment. Demographic features, cause of the wound, location of the wound, take rate, complications of Integra coverage, time from Integra coverage to skin transplantation, and functional and aesthetic results were assessed. Twelve patients (with similar group distributions with respect to sex, age, and location and cause of the injury) were included in the study. The take rate was 78 +/- 8 percent in the conventional treatment group and 98 +/- 2 percent in the fibrin/negative-pressure therapy group (p < 0.003). The mean period from Integra coverage to skin transplantation was 24 +/- 3 days in the conventional treatment group but only 10 +/- 1 days in the fibrin/negative-pressure therapy group (p < 0.002). The decrease in the interval between coverage with Integra and skin transplantation resulted in shorter hospital stays. The use of fibrin glue and negative-pressure therapy in combination with Integra could shorten the period from coverage to integration, which would be beneficial in terms of decreased risks of infection, thrombosis, and catabolism. Therefore, it is suggested that Integra be used in combination with fibrin glue and negative-pressure therapy to improve clinical outcomes and shorten hospital stays, with decreased risks of accompanying complications.

Burn size and survival probability in paediatric patients in modern burn care: a prospective observational cohort study

BACKGROUND

Patient survival after severe burn injury is largely determined by burn size. Modern developments in burn care have greatly improved survival and outcomes. However, no large analysis of outcomes in paediatric burn patients with present treatment regimens exists. This study was designed to identify the burn size associated with significant increases in morbidity and mortality in paediatric patients.

METHODS

We undertook a single-centre prospective observational cohort study using clinical data for paediatric patients with burns of at least 30% of their total body surface area (TBSA). Patients were stratified by burn size in 10% increments, ranging from 30% to 100% TBSA, with a secondary assignment made according to the outcome of a receiver operating characteristic (ROC) analysis. Statistical analysis was done with Student's t test, χ(2) test, logistic regression, and ROC analysis, as appropriate, with significance set at p<0·05.

FINDINGS

952 severely burned paediatric patients were admitted to the centre between 1998 and 2008. All groups were comparable in age (mean 7·3 [SD 5·3] years, ranging from 6·1 [5·1] years in the 30-39% TBSA group to 9·6 [5·4] years in the 90-100% TBSA group) and sex distribution (628 [66%] boys, ranging from 59% [73/123] in the 60-69% TBSA group to 82% [42/51] in the 90-100% TBSA group). 123 (13%) patients died (increasing from 3% [five of 180] in the 30-39% TBSA group to 55% [28/51] in the 90-100% TBSA group; p<0·0001), 154 (16%) developed multiorgan failure (increasing from 6% [ten] in the 30-39% TBSA group to 45% [23] in the 90-100% TBSA group; p<0·0001), and 89 (9%) had sepsis (increasing from 2% [three] in the 30-39% TBSA group to 26% [13] in the 90-100% TBSA group; p<0·0001). Burn size of 62% TBSA was a crucial threshold for mortality (odds ratio 10·07, 95% CI 5·56-18·22, p<0·0001).

INTERPRETATION

We established that, in a modern paediatric burn care setting, a burn size of roughly 60% TBSA is a crucial threshold for postburn morbidity and mortality. On the basis of these findings, we recommend that paediatric patients with greater than 60% TBSA burns be immediately transferred to a specialised burn centre. Furthermore, at the burn centre, patients should be treated with increased vigilance and improved therapies, in view of the increased risk of poor outcome associated with this burn size.

FUNDING

Shriners Hospitals for Children, US National Institutes of Health, US National Institute on Disability and Rehabilitation Research, Institute for Translational Sciences, CFI Leaders Opportunity Fund, Physicians' Services Incorporated Foundation.

Human Wharton's jelly mesenchymal stem cells promote skin wound healing through paracrine signaling

INTRODUCTION

The prevalence of nonhealing wounds is predicted to increase due to the growing aging population. Despite the use of novel skin substitutes and wound dressings, poorly vascularized wound niches impair wound repair. Mesenchymal stem cells (MSCs) have been reported to provide paracrine signals to promote wound healing, but the effect of human Wharton's jelly-derived MSCs (WJ-MSCs) has not yet been described in human normal skin.

METHODS

Human WJ-MSCs and normal skin fibroblasts were isolated from donated umbilical cords and normal adult human skin. Fibroblasts were treated with WJ-MSC-conditioned medium (WJ-MSC-CM) or nonconditioned medium.

RESULTS

Expression of genes involved in re-epithelialization (transforming growth factor-β2), neovascularization (hypoxia-inducible factor-1α) and fibroproliferation (plasminogen activator inhibitor-1) was upregulated in WJ-MSC-CM-treated fibroblasts (P≤0.05). WJ-MSC-CM enhanced normal skin fibroblast proliferation (P≤0.001) and migration (P≤0.05), and promoted wound healing in an excisional full-thickness skin murine model.

CONCLUSIONS

Under our experimental conditions, WJ-MSCs enhanced skin wound healing in an in vivo mouse model.

Early fluid resuscitation improves outcomes in severely burned children

BACKGROUND

Recent evidence suggests that timely fluid resuscitation can significantly reduce multiorgan failure and mortality in thermally injured children. In this study, children who received fluid resuscitation within 2 h of a thermal injury were compared with children in which fluid resuscitation was delayed by 2-12 h. We hypothesized that fluid resuscitation given within 2 h of a thermal injury attenuates renal failure, cardiac arrest, cardiac arrest deaths, incidence of sepsis, and overall mortality.

METHODS

A retrospective chart review was made on 133 children admitted to our institute from 1982 to 1999 with scald or flame burns covering more than 50% of their body surface area. Comparisons between early (< 2 h of injury) or delayed (> or = 2 h of injury) fluid resuscitation were made in children experiencing renal failure, sepsis, non-survivors with cardiac arrest requiring pulmonary and advanced life support, and overall mortality. Comparisons were made using the chi2-test with Yates' continuity correction and joint binomial confidence intervals using the Bonferroni correction.

RESULTS

The incidence of sepsis, renal failure, non-survivors with cardiac arrest, and overall mortality was significantly higher in burned children receiving fluid resuscitation that was delayed by 2 h or more compared with those receiving fluid resuscitation within 2 h of thermal injury (P < 0.001).

CONCLUSIONS

Data suggest that fluid resuscitation, given within 2 h of a thermal injury, may be one of the most important steps in the prevention of multi-organ failure and mortality.