Effect of Poloxamer 188 on deepening of deep second-degree burn wounds in the early stage

Early cutaneous inflammatory response at different degree of burn and its significance for clinical diagnosis and management

A complete characterization of the burn wound based on cutaneous architectural changes and inflammatory response is extremely important to provide evidence for progressive changes in the burn wound. Burn wounds are highly susceptible to conversion into deeper wounds, which need special care and attention; thereby, the complete characterization of burn wound type and their subsequent inflammatory status in the cutaneous system at the earliest is of paramount importance. Inflammatory markers at different degrees will help clinicians devise better and more specific treatment strategies for each burn type. The present study is carried out to profile pro-inflammatory gene expression along with immune cell quantification, vascular perfusion, and histopathological assessment in the cutaneous system of murine models. The study revealed that burn injury caused an immediate increase in vascular perfusion in superficial and partial-thickness burns, whereas there was a decrease in vascular perfusion in full-thickness burns. An influx of lymphocytes at the edges of burn wounds in each type of burn injury was well-orchestrated with the event of vascular perfusion. Further, pro-inflammatory gene expression profiling revealed significant upregulation vis-à-vis upregulation of TNF-α and MCP-1 genes, with an increase in the number of neutrophils following 72 h of injury that evidently cemented the conversion of superficial burn into partial-thickness burn. The molecular findings were profoundly supported by the histopathological changes. Thus, our foundational studies show distinct characteristic cutaneous changes correlated with the expression of key pro-inflammatory genes in three different types of burn injuries. Characterization of these cutaneous inflammatory responses provides a promising future for medical interventions involved with different degrees of burn injury, and it will also help in the pre-clinical testing of therapies for burn injury.

Combined Silver Sulfadiazine Nanosuspension with Thermosensitive Hydrogel: An Effective Antibacterial Treatment for Wound Healing in an Animal Model

Introduction

Silver sulfadiazine (AgSD) is widely used in burn wound treatment due to its broad-spectrum antibacterial activity. However, its application in wound healing is greatly hindered by the low solubility of AgSD particles and their cellular cytotoxicity. Herein, we studied the safety and in vivo efficacy of nano-sized silver sulfadiazine loaded in poloxamer thermosensitive hydrogel (NS/Gel).

Methods

In NS/Gel, silver sulfadiazine was prepared into silver sulfadiazine nanosuspension (NS) to improve the solubility and enhance its antibacterial activity, whereas the poloxamer thermosensitive hydrogel was selected as a drug carrier of NS to achieve slow drug release and reduced cytotoxicity. The acute toxicity of silver sulfadiazine nanosuspension was first evaluated in healthy mice, and its median lethal dose (LD₅₀) was calculated by the modified Karber method. Furthermore, in vivo antibacterial effect and wound healing property of NS/Gel were evaluated on the infected deep second-degree burn wound mice model.

Results

The mortality ratio of mice was concentration-dependent, and the LD₅₀ for silver sulfadiazine nanosuspension was estimated to be 252.1 mg/kg (230.8 to 275.4 mg/kg, 95% confidence limit). The in vivo dosages used for burn wound treatment (40-50 mg/kg) were far below LD₅₀ (252.1 mg/kg). NS/Gel significantly accelerated wound healing in the deep second wound infection mice model, achieving > 85% wound contraction on day 14. Staphylococcus aureus in the wound region was eradicated after 7 days in NS/Gel group, while the bacterial colony count was still measurable in the control group. Histological analysis and cytokines measurement confirmed that the mice treated with NS/Gel exhibited well-organized epithelium and multiple keratinized cell layers compared to control groups with the modulated expression of IL-6, VEGF, and TGF-β.

Conclusion

The combination of silver sulfadiazine nanosuspension and thermo-responsive hydrogel has great potential in clinical burn wound treatment.

Ameliorative effect of bone marrow-derived mesenchymal stem cells on burn-induced hepatic and metabolic derangements in rats

AIMS

The current study aims to investigate the therapeutic potential of bone marrow-derived mesenchymal stem cells (MSCs) as a solo therapy in ameliorating both skin lesions and liver injury induced by cutaneous severe burn injury (SBI) in rats.

MAIN METHODS

In anesthetized male adult Wistar albino rats, 30 % total burn surface area and established hepatic injury was achieved via direct contact of each experimental animal's dorsum with heated metal rod (100 °C) for 10 s. On the next day following burn, human MSCs or mouse MSCs was administered locally around the burn site and intraperitonially (0.5 × 10⁶ cells/rat for each route) and outcomes were investigated at 4 and 14 days following burn induction.

KEY FINDINGS

Both types of MSCs significantly improved skin and liver histology, decreased liver enzymes, and ameliorated oxidative stress in hepatocytes of SBI-rats. Further, SBI-induced rises in hepatic apoptotic marker (caspase-3, Bax) and serum inflammatory markers (TNF-α, IL-1β, and IL-6) were reduced following either human or mouse MSC administration. In addition, MSCs augmented insulin receptor substrate-1, phosphorylated protein kinase-B (phospho-Akt), while alleviating serum glucose levels in SBI-rats. These previous effects persisted even at the 14-day time point.

SIGNIFICANCE

Following single administration, bone marrow-derived MSCs is capable of counteracting SBI-induced skin lesions as well as related hepatic complications, specifically via mitigating postburn hyperglycemia and hyperinflammation.

Therapeutic Strategies to Reduce Burn Wound Conversion

Burn wound conversion refers to the phenomenon whereby superficial burns that appear to retain the ability to spontaneously heal, convert later into deeper wounds in need of excision. While no current treatment can definitively stop burn wound conversion, attempts to slow tissue damage remain unsatisfactory, justifying the need for new therapeutic interventions. To attenuate burn wound conversion, various studies have targeted at least one of the molecular mechanisms underlying burn wound conversion, including ischemia, inflammation, apoptosis, autophagy, generation of reactive oxygen species, hypothermia, and wound rehydration. However, therapeutic strategies that can target various mechanisms involved in burn wound conversion are still lacking. This review highlights the pathophysiology of burn wound conversion and focuses on recent studies that have turned to the novel use of biologics such as mesenchymal stem cells, biomaterials, and immune regulators to mitigate wound conversion. Future research should investigate mechanistic pathways, side effects, safety, and efficacy of these different treatments before translation into clinical studies.

Poloxamer-188 Exacerbates Brain Amyloidosis, Presynaptic Dystrophies, and Pathogenic Microglial Activation in 5XFAD Mice

Background:

Alzheimer’s disease (AD) is initiated by aberrant accumulation of amyloid beta (Aβ) protein in the brain parenchyma. The microenvironment surrounding amyloid plaques is characterized by the swelling of presynaptic terminals (dystrophic neurites) associated with lysosomal dysfunction, microtubule disruption and impaired axonal transport. Aβ-induced plasma membrane damage and calcium influx could be potential mechanisms underlying dystrophic neurite formation.

Objective:

We tested whether promoting membrane integrity by brain administration of a safe FDA approved surfactant molecule poloxamer-188 (P188) could attenuate AD pathology in vivo.

Methods:

Three-month-old 5XFAD male mice were administered several concentrations of P188 in the brain for 42 days with mini-osmotic pumps. After 42 days, mice were euthanized and assessed for amyloid pathology, dystrophic neurites, pathogenic microglia activation, tau phosphorylation and lysosomal / vesicular trafficking markers in the brain.

Results:

P188 was lethal at the highest concentration of 10mM. Lower concentrations of P188 (1.2, 12 and 120μM) were well tolerated. P188 increased brain Aβ burden, potentially through activation of the γ-secretase pathway. Dystrophic neurite pathology was exacerbated in P188 treated mice as indicated by increased LAMP1 accumulation around Aβ deposits. Pathogenic microglial activation was increased by P188. Total tau levels were decreased by P188. Lysosomal enzyme cathepsin D and calcium-dependent vesicular trafficking regulator synaptotagmin-7 (SYT7) were dysregulated upon P188 administration.

Conclusion:

P188 brain delivery exacerbated amyloid pathology, dystrophic neurites and pathogenic microglial activation in 5XFAD mice. These effects correlated with lysosomal dysfunction and dysregulation of plasma membrane vesicular trafficking. P188 is not a promising therapeutic strategy against AD pathogenesis.

Analysis of the Curative Effect and Influencing Factors of Collagen Sponge Combined with Autologous Skin Graft in the Treatment of Deep Burn Patients

Burn is one of the common traumatic diseases in clinics. After deep burn, the complicated changes of the condition are caused by the burn wound, which ends with the repair of the wound. For patients with deep burns, whether the wound can be repaired as soon as possible is the key to the success of clinical treatment. For patients with deep burns, due to the lack of an autologous skin source, scar hyperplasia at donor site, skin graft repair at donor site, postoperative flap necrosis, and other problems in traditional surgical procedures, the method of improving function only by an autologous skin source has been unable to perform the later function reconstruction in patients with deep burns. In this study, collagen sponge combined with autologous skin graft was used to treat patients with deep burn, and the clinical efficacy of the patients was observed, and the related factors affecting the efficacy of the patients were analyzed. The results showed that collagen sponge combined with autologous skin graft was effective in the treatment of deep burn patients, and it was worth popularizing. Deep III-IV degree burns, wound infection, and hospital stay >3 months are all risk factors affecting the postoperative curative effect of patients. Therefore, in the clinical work, we should focus on patients with deep III-IV degree burns, perform surgery as soon as possible, and actively deal with wounds to prevent infection, which is beneficial to improve the curative effect.

Secondary Burn Progression Mitigated by an Adenosine 2A Receptor Agonist

BACKGROUND

Current burn therapy is largely supportive with limited therapies to curb secondary burn progression. Adenosine 2A receptor (A2AR) agonists have anti-inflammatory effects with decreased inflammatory cell infiltrate and release of pro-inflammatory mediators. Using a porcine comb burn model, we examined whether A2AR agonists could mitigate burn progression.

STUDY DESIGN

Eight full-thickness comb burns (4 prongs with 3 spaces per comb) per pig were generated with the following specifications: temperature 115° C, 3 kg force, and 30 second application time. In a randomized fashion, animals (4 per group) were then treated with A2AR agonist (ATL-1223, 3 ng/kg/min, intravenous infusion over 6 hours) or vehicle control. Necrotic interspace development was the primary outcome and additional histologic assessments were conducted.

RESULTS

Analysis of unburned interspaces (72 per group) revealed that ATL-1223 treatment decreased the rate of necrotic interspace development over the first 4 days following injury (p<0.05). Treatment significantly decreased dermal neutrophil infiltration at 48 hours following burn (14.63±4.30 vs 29.71±10.76 neutrophils/high-power field, p=0.029). Additionally, ATL-1223 treatment was associated with fewer interspaces with evidence of microvascular thrombi through post-burn day 4 (18.8% vs 56.3%, p=0.002). Two weeks following insult, the depth of injury at distinct burn sites (adjacent to interspaces) was significantly reduced by ATL-1223 treatment (2.91±0.47 vs 3.28±0.58 mm, p=0.038).

CONCLUSION

This work demonstrates the ability of an A2AR agonist to mitigate burn progression through dampening local inflammatory processes. Extended dosing strategies may yield additional benefit and improve cosmetic outcome in those with severe injury.

Poloxamer 188 exerts a cryoprotective effect on rooster sperm and allows decreasing glycerol concentration in the freezing extender

Glycerol is the most widely used cryoprotectant for rooster sperm because it declines the mechanical damage to sperm during the freezing process. Despite its high molecular weight and viscosity, which may be cytotoxic, glycerol can cause damage to cells during the cryopreservation process, resulting in less fertility. Poloxamer 188 (P188) is an embryo cryopreservation supplement effective in many species and also for cell lines and plant cells. We tested the suitability of P188 in the cryopreservation of rooster sperm, considering post-thawing motility, abnormalities, membrane functionality (hypo-osmotic swelling test), mitochondrial activity, viability, apoptosis status, reactive oxygen species production, and ATP content after thawing and the fertility and hatchability after AI. We carried out a factorial experiment with glycerol concentrations of 2% glycerol (G2) and 8% glycerol (G8) and P188 concentrations of 0% (P0), 0.1% (P0.1), 0.5% (P0.5), and 1% (P1) as fixed effects, with replicate (seven) as a random effect. Interactions between glycerol and P188 were found, with G2P1 yielding higher quality and fertility. G8P0.5 yielded better in most parameters, however, not reaching G2P1. G2P1 showed significantly higher results for total and progressive motility, kinetic parameters (average path velocity, straight-line velocity, and linearity), membrane functionality, viability, mitochondrial activity, and ATP content and lower apoptosis, dead sperm, and reactive oxygen species production. G2P1 resulted in the highest percentages of fertilized and hatched eggs, with no effects in the hatched eggs ratio. Interestingly, G2 was less efficient in many parameters than G8 when combined with P0 and P0.1, being equivalent to G8 with P0.5 and superior to any G8 treatment as G2P1. In conclusion, P188 could improve rooster semen cryopreservation and allow reduction of glycerol in extenders, with a consequent impact in the poultry industry.

Argon Atmospheric Plasma Treatment Promotes Burn Healing by Stimulating Inflammation and Controlling the Redox State

Burns are a public health problem, with second-degree burns as one of the most common types. Although intense inflammation worsens burn healing, effective therapies are scarce. Thus, infections and hypertrophic scars may occur, which compromise patient quality of life and may delay healing. Argon atmospheric plasma (AP) has been shown to positively influence wound healing. In the context of identifying effective and alternative therapies for the treatment of second-degree burns, the present study evaluated AP in the treatment of second-degree burns in rats compared to that for sham treatment on the 2nd, 7th, 14th, and 21st days post-injury. Our results revealed proinflammatory effect for AP by recruiting predominantly neutrophils on the 7th day and macrophages on the 21st day compared to sham treatment, allowing a greater production of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-17, and also controlled the inflammation by IL-10 and transforming growth factor (TGF)-β1. AP also showed antioxidant activity important for controlling oxidative damage on the 2nd day. This favored the induction of angiogenesis from the 2nd day and induction fibroplasia and fibrillogenesis after the 14th day, which enhanced burn healing with the formation of a thinner burn eschar before the 21st day post-burn. Thus, AP effectively modulated the inflammatory phase of second-degree burn healing through the control of oxidative damage that favored the following phases. Therefore, AP is a relevant alternative in the treatment of second-degree burns.

Comparison of a topical surfactant and a topical antibiotic in the rat comb burn model

BACKGROUND

Burn injury progression in the secondary zone of ischemia is common leading to delayed healing and increased scarring. We hypothesized that a topical surfactant, would reduce burn injury progression in a validated rat comb burn model compared with topical antibiotic ointment.

METHODS

We created 40 comb burns on 20 rats which were randomized to daily topical application of the surfactant or a triple antibiotic ointment. The comb burns consisted of 4 full thickness burns with 3 unburned interspaces between the 4 burns. These unburned interspaces represented the zone of ischemia, and when left untreated, generally progress to full thickness necrosis within several days. Comb burns were assessed daily for the presence of gross necrosis of the interspaces. At 7 days the comb burns were excised and blindly evaluated for the presence of histological evidence of necrosis. The study had 80% power to detect a 25% difference in the percentages of necrotic interspaces on day 7.

RESULTS

There were no differences in the percentages of histologically necrotic interspaces at 7 days in burns treated with the surfactant or antibiotic ointment (85% [95%CI, 74 to 92] vs. 75% [95%CI, 63 to 84]; mean difference 10% [95%CI -4 to 24]). There were also no between group differences in the percentages of grossly necrotic interspaces on any of the seven days of the experiment. The surfactant remained intact and adherent while the antibiotic had been absorbed at each daily dressing change.

CONCLUSIONS

A topical surfactant did not reduce injury progression in the rat comb burn model when compared with antibiotic ointment. The surfactant was more durable than the antibiotic ointment.

Effects of a surfactant-based gel on acute and chronic paediatric wounds: a panel discussion and case series

On 20 November 2018, following the International Society for Paediatric Wound Care conference, a closed panel meeting took place in which the use of a surfactant-based gel (PluroGel (PMM), Medline Industries, Illinois, US) in paediatric wound care was discussed. The authors shared their experiences, thoughts, experimental data and clinical results. The panel identified the need for a product that can gently cleanse paediatric wounds and remove devitalised tissue without causing discomfort or skin reactions, as well as potentially promote healing. In adults, PMM has been shown to assist healing by hydrating the wound, controlling exudate and debriding non-viable tissue. Islands of neo-epithelium have also been reported to appear rapidly in different parts of the wound bed. No adverse effects on these proliferating cells have been observed. In vitro data suggest that PMM can remove biofilm, as well as potentially promote healing through cell salvage. The panel, therefore, set out to discuss their experiences of using PMM in the paediatric patients and to establish a consensus on the indications for its use and application in this population. This article will describe the main outcomes of that discussion and present case studies from paediatric patients with a variety of wound types, who were treated with PMM by members of the panel.

Cell salvage in acute and chronic wounds: a potential treatment strategy. Experimental data and early clinical results

On 9 May 2018, the authors took part in a closed panel discussion on the impact of cell salvage in acute and chronic wounds. The goal was to deliberate the possible use of plurogel micelle matrix (PMM) as a new treatment strategy for wound healing and the authors openly shared their experiences, thoughts, experimental data and early clinical results. The outcome of the panel discussion has been abridged in this paper. The cell membrane consists of a lipid bilayer, which provides a diffusion barrier separating the inside of a cell from its environment. Cell membrane injury can result in acute cellular necrosis when defects are too large and cannot be resealed. There is a potential hazard to the body when these dying cells release endogenous alarm signals referred to as 'damage (or danger) associated molecular patterns' (DAMPs), which trigger the innate immune system and modulate inflammation. Cell salvage by membrane resealing is a promising target to ensure the survival of the individual cell and prevention of further tissue degeneration by inflammatory processes. Non-ionic surfactants such as poloxamers, poloxamines and PMM have the potential to resuscitate cells by inserting themselves into damaged membranes and stabilising the unstable portions of the lipid bilayers. The amphiphilic properties of these molecules are amenable to insertion into cell wall defects and so can play a crucial, reparative role. This new approach to cell rescue or salvage has gained increasing interest as several clinical conditions have been linked to cell membrane injury via oxidative stress-mediated lipid peroxidation or thermal disruption. The repair of the cell membrane is an important step in salvaging cells from necrosis to prevent further tissue degeneration by inflammatory processes. This is applicable to acute burns and chronic wounds such as diabetic foot ulcers (DFUs), chronic venous leg ulcers (VLUs), and pressure ulcers (PUs). Experimental data shows that PMM is biocompatible and able to insert itself into damaged membranes, salvaging their barrier function and aiding cell survival. Moreover, the six case studies presented in this paper reveal the potential of this treatment strategy.

Design and characterization of an organogel system containing ascorbic acid microparticles produced with propolis by-product

This study aimed to prepare and characterize organogels containing microparticles of ascorbic acid (AA) obtained from propolis by-product. The formulations F1 (5% of microparticles) and F2 (10% of microparticles) were evaluated regarding rheological and textural properties, antioxidant and radical scavenging activity, in vitro release and cellular studies. The organogels showed plastic flow behavior and rheopexy. The textural parameters were within acceptable values for semisolid formulations. The antioxidant capacity of organogels F1 and F2 by the DPPH assay demonstrated IC₅₀ ranging from 1523.59 to 1166.97 μg/mL, respectively. For the FRAP assay, the values found were 842.88 and 956.14 μmol of FSE/g formulation, respectively. Good scavenging activity against nitrogen species was observed. The concentration of 63 μg/mL did not present toxicity on HaCaT and HFF-1 cells. In vitro release profile of AA from organogels showed a slow pattern of drug release, mainly for F2. Therefore, the proposed organogel containing AA microparticles with propolis by-product matrix represents a promising platform for topical drug delivery with antioxidant effect.

Role of Autophagy Biomarkers In Burn-Age Estimation and Progression

BACKGROUND

Determination of time passed since burn injury in the living is critical in forensic science. Autophagy biomarkers and vitronectin can play an important role in determination of the age of burn injuries through their levels in the tissue.

OBJECTIVE

The aim of this study was to investigate the role of autophagy biomarkers in dating burn injury and to correlate them with the histopathological effects of deep second-degree thermal burn.

METHOD

Fifty-four male rats were used in this study after infliction of second-degree thermal burns to their skin. Samples were taken from them after 30 minutes and one, four, 24, 48, and 72 hours following burn to be examined histologically and also for autophagy biomarkers and vitronectin.

RESULTS

Significant reduction in the autophagy biomarkers (p < 0.001) over the first 24 hours then began to increase but still not reach the normal level up to 72 hours after burn. Vitronectin level increased after burn infliction 1.5-fold after first hour, then up to four-fold after four hours and after that began to decline but still did not reach the normal level up to 72 hours.

CONCLUSION

Autophagy biomarkers can be used as a forensic tool in determination of the time passed since burn infliction in living.

Surfactants: Role in biofilm management and cellular behaviour

Appropriate and effective wound cleaning represents an important process that is necessary for preparing the wound for improved wound healing and for helping to dislodge biofilms. Wound cleaning is of paramount importance to wound bed preparation for helping to enhance wound healing. Surfactant applications in wound care may represent an important area in the cleaning continuum. However, understanding of the role and significance of surfactants in wound cleansing, biofilm prevention and control, and enhancing cellular viability and proliferation is currently lacking. Despite this, some recent evidence on poloxamer-based surfactants where the surfactants are present in high concentration have been shown to have an important role to play in biofilm management; matrix metalloproteinase modulation; reducing inflammation; and enhancing cellular proliferation, behaviour, and viability. Consequently, this review aims to discuss the role, mode of action, and clinical significance of the use of medically accepted surfactants, with a focus on concentrated poloxamer-based surfactants, to wound healing but, more specifically, the role they may play in biofilm management and effects on cellular repair.

Novel pharmacotherapy for burn wounds: what are the advancements

INTRODUCTION

The prognosis for severe burns has improved significantly over the past 50 years. Meanwhile, burns have become an affliction mainly affecting the less well-developed regions of the world. Early excision and skin grafting has led to major improvements in therapeutic outcomes.

AREAS COVERED

The purpose of this article is to survey the use of pharmacotherapy to treat different pathophysiological complications of burn injury. The author, herein, discusses the use of drug treatments for a number of systemic metabolic disturbances including hyperglycemia, elevated catabolism, and gluconeogenesis.

EXPERT OPINION

Advancements in personalized and molecular medicine will make an impact on burn therapy. Similarities between severe burns and other critically ill patients will lead to cross-fertilization between different medical specialties. Furthermore, advances in stem cells and tissue regeneration will lead to improved healing and less lifelong disability. Indeed, research in new drug therapy for burns is actively progressing for many different complications.

Biological function evaluation and effects of laser micro-pore burn-denatured acellular dermal matrix

OBJECTIVE

In the field of burns repairs, many problems exist in the shortage of donor skin, the expense of allograft or xenograft skin, temporary substitution and unsatisfactory extremity function after wound healing. Previous studies showed that burn-denatured skin could return to normal dermis formation and function. This study investigates the application of laser micro-pore burn-denatured acellular dermis matrix (DADM) from an escharotomy in the repair of burn wounds and evaluates the biological properties and wound repair effects of DADM in implantation experiments in Kunming mice.

METHODS

Specific-pathogen-free (SPF) Kunming mice were used in this study. A deep II° burn wound was created on the dorsum of the mice by an electric heated water bath. The full-thickness wound tissue was harvested. The necrotic tissue and subcutaneous tissue were removed. The denatured dermis was preserved and treated with 0.25% trypsin, 0.5% Triton X-100. The DADM was drilled by laser micro-pore. The biological properties and grafting effects of laser micro-pore burn-DADM were evaluated by morphology, cytokine expression levels and subcutaneous implantation experiments in Kunming mice.

RESULTS

We found statistical significance (P<0.05) of the elastic modulus (MPa), maximum load force (N) and contraction measurement (CM) of the laser micro-pore burn-DADM (experimental group) compared to the control group (no laser micro-pore burn-DADM). Cytokine expression level was different in the dermal matrixes harvested at various time points after burn (24h, 48h, 72h and infected wound group). Comparing the dermal matrix from 24h burn tissue to infected wound tissue, the expression level of IL-6, MMP-24, VE-cadherin and VEGF were decreased. We found no inflammatory cells infiltration in the dermal matrix were observed in both experimental and control groups (24h burn group), while the obviously vascular infiltration and fiber fusion were observed in the experimental group after subcutaneous implantation experiments.

CONCLUSION

There was better bio-performance, low immunogenicity and better dermal incorporation after treated by laser micro-pore drilling and decellularized deep II° burn-DADM, which may be considered as a better substitute for dermal matrix. Furthermore, the earlier harvested DADM after burn (24h) shows the better transplantation effect.

PEO-PPO Diblock Copolymers Protect Myoblasts from Hypo-Osmotic Stress In Vitro Dependent on Copolymer Size, Composition, and Architecture

Poloxamer 188, a triblock copolymer of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO), protects cellular membranes from various stresses. Though numerous block copolymer variants exist, evaluation of alternative architecture, composition, and size has been minimal. Herein, cultured murine myoblasts are exposed to the stresses of hypotonic shock and isotonic recovery, and membrane integrity was evaluated by quantifying release of lactate dehydrogenase. Comparative evaluation of a systematic set of PEO-PPO diblock and PEO-PPO-PEO triblock copolymers demonstrates that the diblock architecture can be protective in vitro. Short PPO blocks hinder protection with >9 PPO units needed for protection at 150 μM and >16 units needed at 14 μM. Addition of a tert-butyl end group enhances protection at reduced concentration. When the end group and PPO length are fixed, increasing the PEO length improves protection. This systematic evaluation establishes a new in vitro screening tool for evaluating membrane-sealing amphiphiles and provides mechanistic insight to guide future copolymer design for membrane stabilization in vivo.

3,4-Methylenedioxy-β-Nitrostyrene Ameliorates Experimental Burn Wound Progression by Inhibiting the NLRP3 Inflammasome Activation

BACKGROUND

Burn wound progression remains a challenging problem in the clinic. Secondary tissue damage caused by unlimited inflammatory response is considered to be one of the key factors contributing to this clinical problem. Nucleotide-binding oligomerization domain-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome has recently been found to play important roles in immune activation and the inflammatory response after burn/trauma. This experimental study aims (1) to observe the expression and distribution of NLRP3 inflammasome in burn wounds of a rat burn model and (2) to study whether inhibiting the NLRP3 inflammasome activation would ameliorate burn wound progression.

METHODS

A deep second-degree burn was inflicted on the backs of Wistar rats. The expression of NLRP3 inflammasome components and interleukin-1β were determined by Western blot and coimmunoprecipitation. The distribution of NLRP3 inflammasome was assessed by immunohistochemical staining and double-labeling immunofluorescence. Neutrophil infiltration, wound perfusion, burn depth, and wound healing time were assessed.

RESULTS

Burn induced remarkable NLRP3 inflammasome activation and cleavage of interleukin-1β. The NLRP3 inflammasome was observed mainly in macrophages of the zone of stasis. 3,4-Methylenedioxy-β-nitrostyrene significantly inhibited NLRP3 inflammasome activation and inflammatory cytokine production in burn wounds. Consequently, neutrophil infiltration was reduced, wound perfusion was restored, burn wound progression was ameliorated, and wound healing was accelerated.

CONCLUSIONS

In this study, the authors demonstrated that burn induced NLRP3 inflammasome activation and inflammatory response in wounds, which may be associated with burn wound progression. Treatment with 3,4-methylenedioxy-β-nitrostyrene inhibited NLRP3 inflammasome activation, ameliorated burn wound progression, and promoted wound healing.

Far-infrared promotes burn wound healing by suppressing NLRP3 inflammasome caused by enhanced autophagy

Understanding the underlying molecular mechanisms in burn wound progression is crucial to providing appropriate diagnoses and designing therapeutic regimens for burn patients. When inflammation becomes unregulated, recurrent, or excessive, it interferes with burn wound healing. Autophagy, which is a homeostatic and catabolic degradation process, was found to protect against ischemic injury, inflammatory diseases, and apoptosis in some cases. In the present study, we investigated whether far-infrared (FIR) could ameliorate burn wound progression and promote wound healing both in vitro and in a rat model of deep second-degree burn. We found that FIR induced autophagy in differentiated THP-1 cells (human monocytic cells differentiated to macrophages). Furthermore, FIR inhibited both the NLRP3 inflammasome and the production of IL-1β in lipopolysaccharide-activated THP-1 macrophages. In addition, FIR induced the ubiquitination of ASC, which is the adaptor protein of the inflammasome, by increasing tumor necrosis factor receptor-associated factor 6 (TRAF6), which is a ubiquitin E3 ligase. Furthermore, the exposure to FIR then promoted the delivery of inflammasome to autophagosomes for degradation. In a rat burn model, FIR ameliorated burn-induced epidermal thickening, inflammatory cell infiltration, and loss of distinct collagen fibers. Moreover, FIR enhanced autophagy and suppressed the activity of the NLRP3 inflammasome in the rat skin tissue of the burn model. Based on these results, we suggest that FIR-regulated autophagy and inflammasomes will be important for the discovery of novel therapeutics to promote the healing of burn wounds.

KEY MESSAGES

Far-infrared (FIR) induced autophagy in THP-1 macrophages. FIR suppressed the NLRP3 inflammasome through the activation of autophagy. FIR induced the ubiquitination of ASC by increasing TRAF6. FIR ameliorated burn wound progression and promoted wound healing in a rat burn model.

Current concepts on burn wound conversion-A review of recent advances in understanding the secondary progressions of burns

Burn wound conversion describes the process by which superficial partial thickness burns convert into deeper burns necessitating surgical intervention. Fully understanding and thus controlling this phenomenon continues to defy burn surgeons. However, potentially guiding burn wound progression so as to obviate the need for surgery while still bringing about healing with limited scarring is the major unmet challenge. Comprehending the pathophysiologic background contributing to deeper progression of these burns is an essential prerequisite to planning any intervention. In this study, a review of articles examining burn wound progression over the last five years was conducted to analyze trends in recent burn progression research, determine changes in understanding of the pathogenesis of burn conversion, and subsequently examine the direction for future research in developing therapies. The majority of recent research focuses on applying therapies from other disease processes to common underlying pathogenic mechanisms in burn conversion. While ischemia, inflammation, and free oxygen radicals continue to demonstrate a critical role in secondary necrosis, novel mechanisms such as autophagy have also been shown to contribute affect significantly burn progression significantly. Further research will have to determine whether multiple mechanisms should be targeted when developing clinical therapies.

Boron and Poloxamer (F68 and F127) Containing Hydrogel Formulation for Burn Wound Healing

Burn injuries, the most common and destructive forms of wounds, are generally accompanied with life-threatening infections, inflammation, reduced angiogenesis, inadequate extracellular matrix production, and lack of growth factor stimulation. In the current study, a new antimicrobial carbopol-based hydrogel formulated with boron and pluronic block copolymers was evaluated for its healing activity using in vitro cell culture techniques and an experimental burn model. Cell viability, gene expression, and wound healing assays showed that gel formulation increased wound healing potential. In vitro tube-like structure formation and histopathological examinations revealed that gel not only increased wound closure by fibroblastic cell activity, but also induced vascularization process. Moreover, gel formulation exerted remarkable antimicrobial effects against bacteria, yeast, and fungi. Migration, angiogenesis, and contraction-related protein expressions including collagen, α-smooth muscle actin, transforming growth factor-β1, vimentin, and vascular endothelial growth factor were considerably enhanced in gel-treated groups. Macrophage-specific antigen showed an oscillating expression at the burn wounds, indicating the role of initial macrophage migration to the wound site and reduced inflammation phase. This is the first study indicating that boron containing hydrogel is able to heal burn wounds effectively. The formulation promoted burn wound healing via complex mechanisms including stimulation of cell migration, growth factor expression, inflammatory response, and vascularization.

Sodium pentaborate pentahydrate and pluronic containing hydrogel increases cutaneous wound healing in vitro and in vivo

After a disruption of skin integrity, the body produces an immediate response followed by a functional and comparable regeneration period, referred to as wound healing. Although normal wounds do not need much attention during the healing period, chronic (non-healing) wounds are the major challenge of current dermatological applications. Therefore, developing new, safe, and effective wound healing drugs has always been an attractive area of international research. In the current study, sodium pentaborate pentahydrate (NaB), pluronics (Plu; F68 and F127), and their combinations were investigated for their wound healing activities, using in vitro and in vivo approaches. The results revealed that NaB significantly increased migration capacity and superoxide dismutase activity in primary human fibroblasts. Combinations of optimized concentrations for pluronic block co-polymers further increased cell migration, and the messenger RNA (mRNA) expression levels of important growth factor and cytokines (vascular endothelial growth factor (VEGF), transforming growth factor beta (TGF-β), and tumor necrosis factor alpha (TNF-α)). NaB containing hydrogel co-formulated with pluronics was also investigated for their wound healing activities using a full thickness wound model in rats. Macroscopic and histopathological analysis confirmed that wounds in combination gel-treated groups healed faster than those of control groups. NaB/Plu gel application was found to increase wound contraction and collagen deposition in the wound area. Therefore, our results suggest that NaB, and its pluronics combination, could be used in dermatological clinics and be a future solution for chronic wounds. However, further studies should be conducted to explore its exact action of mechanism and effects of this formulation on chronic wounds.

Role of autophagy and apoptosis in wound tissue of deep second-degree burn in rats

OBJECTIVES

The pathogenesis of burn wound progression is poorly understood. Contributing factors include continuous loss of blood perfusion, excessive inflammation, and elevated apoptosis levels in wound tissue. Macroautophagy (here referred to simply as "autophagy") is associated with many chronic diseases. The authors hypothesized that autophagy is involved in burn wound progression in a rat model of deep second-degree burn.

METHODS

Deep second-degree burns were modeled using a brass rod heated to 100°C applied for 6 seconds to the back skin of Wistar rats. Full-thickness biopsies were obtained from burned and nonburned controls at several times postburn. Western blotting and immunohistochemical (IHC) staining determined expression of the autophagy markers Light Chain 3 (LC3) and beclin-1. Apoptosis was determined by terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL) assay and laser Doppler flowmetry (LDF)-measured tissue perfusion. Myeloperoxidase (MPO) activity assay measured inflammation. Hematoxylin and eosin (H&E) and Masson's trichrome staining-determined pathology and wound depth.

RESULTS

The LC3 and beclin-1 protein level in burn wounds decreased to one-fourth of normal levels (p<0.01) over 24 hours and then began to increase but still did not reach their normal level. TUNEL-positive cells in burn wounds were 3.7-fold (p<0.01) elevated over 48 hours and then decreased slightly, yet still remained higher than in normal skin. The burn wound progressed in depth over 72 hours. In addition, significant decrease in LDF values and upregulation of MPO activity were observed. Enhanced LC3-positive cells were observed in the deep dermal layer of burn wounds as shown by IHC staining.

CONCLUSIONS

A reduction in autophagy and blood flow and an increase in apoptosis and inflammation were observed in burn wounds early during the course of burn injury progression. This suggests that autophagy, complemented by apoptosis, play important roles in burn progression. Enhanced autophagy in the deep dermis may be a prosurvival mechanism against ischemia and inflammation after burn injury.

Human umbilical cord mesenchymal stem cells transplantation promotes cutaneous wound healing of severe burned rats

BACKGROUND

Severe burns are a common and highly lethal trauma. The key step for severe burn therapy is to promote the wound healing as early as possible, and reports indicate that mesenchymal stem cell (MSC) therapy contributes to facilitate wound healing. In this study, we investigated effect of human umbilical cord MSCs (hUC-MSCs) could on wound healing in a rat model of severe burn and its potential mechanism.

METHODS

Adult male Wistar rats were randomly divided into sham, burn, and burn transplanted hUC-MSCs. GFP labeled hUC-MSCs or PBS was intravenous injected into respective groups. The rate of wound closure was evaluated by Image Pro Plus. GFP-labeled hUC-MSCs were tracked by in vivo bioluminescence imaging (BLI), and human-specific DNA expression in wounds was detected by PCR. Inflammatory cells, neutrophils, macrophages, capillaries and collagen types I/III in wounds were evaluated by histochemical staining. Wound blood flow was evaluated by laser Doppler blood flow meter. The levels of proinflammatory and anti-inflammatory factors, VEGF, collagen types I/III in wounds were analyzed using an ELISA.

RESULTS

We found that wound healing was significantly accelerated in the hUC-MSC therapy group. The hUC-MSCs migrated into wound and remarkably decreased the quantity of infiltrated inflammatory cells and levels of IL-1, IL-6, TNF-α and increased levels of IL-10 and TSG-6 in wounds. Additionally, the neovascularization and levels of VEGF in wounds in the hUC-MSC therapy group were markedly higher than those in other control groups. The ratio of collagen types I and III in the hUC-MSC therapy group were markedly higher than that in the burn group at indicated time after transplantation.

CONCLUSION

The study suggests that hUC-MSCs transplantation can effectively improve wound healing in severe burned rat model. Moreover, these data might provide the theoretical foundation for the further clinical application of hUC-MSC in burn areas.

Poloxamer 188 (p188) as a membrane resealing reagent in biomedical applications

Maintenance of the integrity of the plasma membrane is essential for maintenance of cellular function and prevention of cell death. Since the plasma membrane is frequently exposed to a variety of mechanical and chemical insults the cell has evolved active processes to defend against these injuries by resealing disruptions in the plasma membrane. Cell membrane repair is a conserved process observed in nearly every cell type where intracellular vesicles are recruited to sites of membrane disruption where they can fuse with themselves or the plasma membrane to create a repair patch. When disruptions are extensive or there is an underlying pathology that reduces the membrane repair capacity of a cell this defense mechanism may prove insufficient and the cell could die due to breakdown of the plasma membrane. Extensive loss of cells can compromise the integrity and function of tissues and leading to disease. Thus, methods to increase membrane resealing capacity could have broad utility in a number of disease states. Efforts to find reagents that can modulate plasma membrane reseal found that specific tri-block copolymers, such as poloxamer 188 (P188, or Pluronic F68), can increase the structural stability and resealing of the plasma membrane. Here we review several current patents and patent applications that present inventions making use of P188 and other copolymers to treat specific disease states such as muscular dystrophy, heart failure, neurodegenerative disorders and electrical injuries, or to facilitate biomedical applications such as transplantation. There appears to be promise for the application of poloxamers in the treatment of various diseases, however there are potential concerns with toxicity with long term application and bioavailability in some cases.