The relationship between protease/anti-protease profile, angiogenesis and re-epithelialisation in acute burn wounds

Wound fluid sampling methods for proteomic studies: A scoping review

Understanding why some wounds are hard to heal is important for improving care and developing more effective treatments. The method of sample collection used is an integral step in the research process and thus may affect the results obtained. The primary objective of this study was to summarise and map the methods currently used to sample wound fluid for protein profiling and analysis. Eligible studies were those that used a sampling method to collect wound fluid from any human wound for analysis of proteins. A search for eligible studies was performed using MEDLINE, Embase and CINAHL Plus in May 2020. All references were screened for eligibility by one reviewer, followed by discussion and consensus with a second reviewer. Quantitative data were mapped and visualised using appropriate software and summarised via a narrative summary. After screening, 280 studies were included in this review. The most commonly used group of wound fluid collection methods were vacuum, drainage or use of other external devices, with surgical wounds being the most common sample source. Other frequently used collection methods were extraction from absorbent materials, collection beneath an occlusive dressing and direct collection of wound fluid. This scoping review highlights the variety of methods used for wound fluid collection. Many studies had small sample sizes and short sample collection periods; these weaknesses have hampered the discovery and validation of novel biomarkers. Future research should aim to assess the reproducibility and feasibility of sampling and analytical methods for use in larger longitudinal studies.

Preclinical efficacy study of a porous biopolymeric scaffold based on gelatin-hyaluronic acid-chondroitin sulfate in a porcine burn injury model: role of critical molecular markers (VEGFA, N-cadherin, COX-2), gamma sterilization efficacy and a comparison of healing potential to Integra™

Development of scaffold from biopolymers can ease the requirements for donor skin autograft and plays an effective role in the treatment of burn wounds. In the current study, a porous foam based, bilayered hydrogel scaffold was developed using gelatin, hyaluronic acid and chondroitin sulfate (G-HA-CS). The fabricated scaffold was characterized physicochemically for pre- and post-sterilization efficacy by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA).In-vitrostudies proved that the scaffold promoted cellular proliferation. The efficacy of G-HA-CS scaffold was compared with Integra™ at different time points (7, 14, 21 and 42 days), in a swine second degree burn wound model. Remarkable healing potential of the scaffold was evident from the wound contraction rate, reduction of IL-6, TNF-αand C3. The expression of healing markers TGF-β1 and collagen 1 revealed significant skin regeneration with regulated fibroblast activation towards the late phase of healing (p< 0.001 at day 21 and 42 vs. control). Expression of Vascular Endothelial Growth Factor A (VEGFA), vimentin and N-cadherin were found to favor angiogenesis and skin regeneration. Mechanistically, scaffold promoted wound healing by modulation of CD-45, cyclooxygenase-2 and MMP-2. Thus, the promising results with foam based scaffold, comparable to Integra™ in swine burn injury model offer an innovative lead for clinical translation for effective management of burn wound.

Protease levels are significantly altered in pediatric burn wounds

Burn wounds contain high levels of protease activity due to the need to remodel the damaged extracellular matrix proteins. While necessary, excessive protease activity can lead to improper wound healing and is associated with increased contraction and fibrosis. No studies to date have investigated the expression changes of all the collagenases and elastases in burn wounds. The present study compares gene expression changes and changes in collagenase and elastase activity between burn wound eschar and normal skin in a pediatric population. Deidentified pediatric tissues were used for these experiments. Burn wound tissue was excised as part of normal standard care within a week from injury; normal skin was removed during elective plastic surgery procedures. RNA-sequencing was performed and significant results were confirmed with qRT-PCR. Activity assays showed a significant increase in both collagenase and elastase activity in the burn wound tissue compared to the normal skin. Western blotting and substrate zymography of tissue homogenates evaluated the results at the protein levels. Four elastases and three collagenases were determined to be significantly upregulated in the wound tissues by both RNA-sequencing and qRT-PCR. Cathepsin V was the only protease that was significantly downregulated. All but one metalloproteinase studied was significantly upregulated. None of the serine proteases were significantly altered in the wound tissues. In conclusion, matrix metalloproteinases appear to be the most highly elevated proteases after a pediatric burn wound injury, at least within the first 3-7 days. The data warrant further investigation into the effects of MMPs on burn wound healing.

Study of negative pressure wound therapy as an adjunct treatment for acute burns in children (SONATA in C): protocol for a randomised controlled trial

BACKGROUND

Although negative pressure wound therapy (NPWT) is widely used in the management of several wound types, its efficacy as a primary therapy for acute burns has not yet been adequately investigated, with research in the paediatric population particularly lacking. There is limited evidence, however, that NPWT might benefit children with burns, amongst whom scar formation, wound progression and pain continue to present major management challenges. The purpose of this trial is to determine whether NPWT in conjunction with standard therapy accelerates healing, reduces wound progression and decreases pain more effectively than standard treatment alone.

METHODS/DESIGN

A total of 104 children will be recruited for this trial. To be eligible, candidates must be under 17 years of age and present to the participating children's hospital within 7 days of their injury with a thermal burn covering <5% of their total body surface area. Facial and trivial burns will be excluded. Following a randomised controlled parallel design, participants will be allocated to either an active control or intervention group. The former will receive standard therapy consisting of Acticoat™ and Mepitel™. The intervention arm will be treated with silver-impregnated dressings in addition to NPWT via the RENASYS TOUCH™ vacuum pump. Participants' dressings will be changed every 3 to 5 days until their wounds are fully re-epithelialised. Time to re-epithelialisation will be studied as the primary outcome. Secondary outcomes will include pain, pruritus, wound progression, health-care-resource use (and costs), ease of management, treatment satisfaction and adverse events. Wound fluid collected during NPWT will also be analysed to generate a proteomic profile of the burn microenvironment.

DISCUSSION

The study will be the first randomised controlled trial to explore the clinical effects of NPWT on paediatric burns, with the aim of determining whether the therapy warrants implementation as an adjunct to standard burns management.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry, ACTRN12618000256279 . Registered on 16 February 2018.

A Descriptive Study of the Temporal Patterns of Volume and Contents Change in Human Acute Burn Edema: Application in Evidence-Based Intervention and Research Design

Edema after burn contributes significantly to burn wound depth conversion. In humans after burn injury, there is a lack of detailed understanding of the contents and temporal changes in volume of acute tissue edema. The novel findings of these studies relate to the collection of edema fluid after partial-thickness burn injury. Edema volume peaks on day 1 after burn without formal fluid resuscitation. The studies indicated that the peak was on day 2 for a resuscitated burn. In contrast, animal studies suggest that the peak of edema occurs by or before day 1 after injury. The findings confirm the pitfalls of evidence derived from animal models and assuming direct transference to humans. Postburn edema was demonstrated to be a high-protein fluid (ie, ≥10 g/L) for the duration of the inflammatory period. The presence of high-protein edema presents greater challenges to clinicians developing novel treatment options. The rate of volume change over time tapered to insignificant levels after day 4 following burn. Greater than 98% of the edema contents was fluid. However, the size of particulate matter did not preclude it passing through patent lymphatic collectors. The results indicate a necessity for urgent postburn intervention, which should incorporate the active stimulation of the lymphatic system to improve efficacy of edema removal.

Topical Negative Pressure on Burns: An Innovative Method for Wound Exudate Collection

Supplemental Digital Content is available in the text.

Burn wound exudate is an important source of information on the wound-healing process and systemic improvement of burn patients. Identification of biomarkers for the prediagnosis of local or systemic complications in patients will have a great impact on adapting personalized procedures in burn treatment. No efficient exudate collection method exists that offers a direct and continuous collection over time. We developed an innovative system based on the negative pressure wound therapy technique to directly collect exudate from burn wounds over several days after burn. This method did not cause any complication or pain for patients, and positive influence on wound healing was seen. Exudate samples were further used in different projects for studying biochemical profile, trace element content, kinetics of bacterial growth, and cell cytotoxicity.

Evaluation of haemoglobin in blister fluid as an indicator of paediatric burn wound depth

The early and accurate assessment of burns is essential to inform patient treatment regimens; however, this first critical step in clinical practice remains a challenge for specialist burns clinicians worldwide. In this regard, protein biomarkers are a potential adjunct diagnostic tool to assist experienced clinical judgement. Free circulating haemoglobin has previously shown some promise as an indicator of burn depth in a murine animal model. Using blister fluid collected from paediatric burn patients, haemoglobin abundance was measured using semi-quantitative Western blot and immunoassays. Although a trend was observed in which haemoglobin abundance increased with burn wound severity, several patient samples deviated significantly from this trend. Further, it was found that haemoglobin concentration decreased significantly when whole cells, cell debris and fibrinous matrix was removed from the blister fluid by centrifugation; although the relationship to depth was still present. Statistical analyses showed that haemoglobin abundance in the fluid was more strongly related to the time between injury and sample collection and the time taken for spontaneous re-epithelialisation. We hypothesise that prolonged exposure to the blister fluid microenvironment may result in an increased haemoglobin abundance due to erythrocyte lysis, and delayed wound healing.

The burn wound exudate-an under-utilized resource

INTRODUCTION

The burn wound exudate represents the burn tissue microenvironment. Extracting information from the exudate relating to cellular components, signaling mediators and protein content can provide much needed data relating to the local tissue damage, depth of the wound and probable systemic complications. This review examines the scientific data extracted from burn wound exudates over the years and proposes new investigations that will provide useful information from this underutilized resource.

METHOD

A literature review was conducted using the electronic database PubMed to search for literature pertaining to burn wound or blister fluid analysis. Key words included burn exudate, blister fluid, wound exudate, cytokine burn fluid, subeschar fluid, cytokine burns, serum cytokines. 32 relevant articles were examined and 29 selected as relevant to the review. 3 papers were discarded due to questionable methodology or conclusions. The reports were assessed for their affect on management decisions and diagnostics. Furthermore, traditional blood level analysis of these mediators was made to compare the accuracy of blood versus exudate in burn wound management. Extrapolations are made for new possibilities of burn wound exudate analysis.

RESULTS

Studies pertaining to burn wound exudate, subeschar fluid and blister fluid analyses may have contributed to burn wound management decisions particularly related to escharectomies and early burn wound excision. In addition, information from these studies has the potential to impact on areas such as healing, scarring, burn wound conversion and burn wound depth analysis.

CONCLUSION

Burn wound exudate analysis has proven useful in burn wound management decisions. It appears to offer a far more accurate reflection of the burn wound pathophysiology than the traditional blood/serum investigations undertaken in the past. New approaches to diagnostics and treatment efficacy assessment are possible utilizing data from this fluid. Burn wound exudate is a useful, currently under-utilized resource that is likely to take a more prominent role in burn wound management.

Local and systemic treatments for acute edema after burn injury: a systematic review of the literature

Burn injury is a complex trauma that results in local and generalized edema. Edema fluid limits the exchange of vital nutrients in healing the burn wound and will compromise vulnerable tissues. Although the importance of edema control in tissue salvage is recognized, treatments targeted at edema control have not been critically reviewed. Thus, the objective was to assess the evidence for the effectiveness of local and systemic treatments for edema management immediately after burn injury. Searches for randomized controlled trials were conducted of online databases, research and thesis registers, and grey literature repositories. Handsearches included journals, bibliographies, and proceedings. Authors were contacted to clarify and submit extra study details. Eight studies were included. Management of acute major burn resuscitation including colloid increases lung edema (mean difference [MD], 0.04 ml/ml alv vol; 95% confidence interval [CI], 0.03-0.04; P < .00001) and mortality (risk ratio, 3.67; 95% CI, 1.16-11.58; P = .03). Continuous administration of vitamin C in acute burn resuscitation reduces local wound edema (MD, -3.50 ml/g; 95% CI, -4.63 to -2.37; P < .00001) and systemic fluid retention (MD, -8.60 kg; 95% CI, -13.47 to -3.73; P = .0005). Local acute hand burn edema is reduced (MD, -29.00 ml; 95% CI, -53.14 to -4.86; P = .02), and active hand motion increased (MD, 10.00°; 95% CI, 4.58-15.42; P = .0003), using electrical stimulation with usual physiotherapy. Each review outcome was based on a small single-facility study. Thus, future research in intervention for acute burn edema must focus on multicentre trials and validation of outcome measures in the burn population.

Deep partial thickness burn blister fluid promotes neovascularization in the early stage of burn wound healing

The effect of burn blister fluid in neovascularization during burn wound healing is unknown. Burn blister fluid, containing a large amount of chemokines, is thought to play a role in the early stage of neovascularization. This process includes angiogenesis and vasculogenesis. Because of different healing time of burn wounds, we hypothesized that neovascularization in superficial partial thickness burn (SPTB) and deep partial thickness burn (DPTB) wounds were different. The neovasculogenic effects of two different burn blister fluids were also different. We found Day 7 DPTB wounds had a significant increase in blood vessels compared with SPTB wounds by immunohistochemistry. DPTB blister fluid significantly promoted neovascularization via increasing endothelial cell proliferation, and migration and differentiation of circulating angiogenic cells relative to SPTB blister fluids. In the animal study, DPTB blister fluids markedly promoted new blood vessel formation compared with those from SPTB blister fluids using in vivo Matrigel plug assay. These results suggest that DPTB wounds require more new vessel formation than SPTB. Furthermore, the measurement of angiogenic activities in burn blister fluids serves as a possible tool for assessing burn wound status.

Molecular dissection of abnormal wound healing processes resulting in keloid disease

Keloids are locally aggressive scars that typically invade into healthy surrounding skin and cause both physical and psychosocial distress to the patient. These pathological scars occur following minimal skin trauma after a variety of causes including burns and trauma. Although the pathogenesis of keloid disease is not well understood, it is considered to be the end product of an abnormal healing process. The aim of this review was to investigate the molecular and cellular pathobiology of keloid disease in relation to the normal wound healing process. The molecular aberrances in keloids that correlate with the molecular mechanisms in normal wound healing can be categorized into three groups: (1) extracellular matrix proteins and their degradation, (2) cytokines and growth factors, and (3) apoptotic pathways. With respect to cellular involvements, fibroblasts are the most well-studied cell population. However, it is unclear whether the fibroblast is the causative cell; they are modulated by other cell populations in wound repair, such as keratinocytes and macrophages. This review presents a detailed account of individual phases of the healing process and how they may potentially be implicated in aberrant raised scar formation, which may help in clarifying the mechanisms involved in keloid disease pathogenesis.

Potential cellular and molecular causes of hypertrophic scar formation

A scar is an expected result of wound healing. However, in some individuals, and particularly in burn victims, the wound healing processes may lead to a fibrotic hypertrophic scar, which is raised, red, inflexible and responsible for serious functional and cosmetic problems. It seems that a wide array of subsequent processes are involved in hypertrophic scar formation, like an affected haemostasis, exaggerated inflammation, prolonged reepithelialization, overabundant extracellular matrix production, augmented neovascularization, atypical extracellular matrix remodeling and reduced apoptosis. Platelets, macrophages, T-lymphocytes, mast cells, Langerhans cells and keratinocytes are directly and indirectly involved in the activation of fibroblasts, which in turn produce excess extracellular matrix. Following the chronology of normal wound healing, we unravel, clarify and reorganize the complex molecular and cellular key processes that may be responsible for hypertrophic scars. It remains unclear whether these processes are a cause or a consequence of unusual scar tissue formation, but raising evidence exists that immunological responses early following wounding play an important role. Therefore, when developing preventive treatment modalities, one should aim to put the early affected wound healing processes back on track as quickly as possible.