Polarized Th2 cytokine production in patients with hypertrophic scar following thermal injury

hsa_circ_0007755 competitively adsorbs miR-27b-3p to mediate CXCL2 expression and recruit Th1 cells to promote hypertrophic scars development

Background and objective

The circular RNA hsa_circ_0007755 is markedly upregulated in hypertrophic scars (HS), yet its functional roles in this fibroproliferative disorder remain to be elucidated. This investigation aims to delineate the regulatory mechanisms of hsa_circ_0007755 in HS and to decode its downstream molecular signaling pathways.

Methods

We established a murine model of HS. Tissue histopathology was assessed using Hematoxylin and Eosin and Masson's trichrome staining. Peripheral blood from the animals was collected and the ratio of T-helper 1 (Th1) to T-helper 2 (Th2) cells was quantified via flow cytometry. The proliferation and apoptosis rates of human hypertrophic scar fibroblasts (hHSFs) were evaluated using the Cell Counting Kit-8 assay and flow cytometry, respectively. The invasive capacity of hHSFs was assessed via a Transwell assay. Co-culture experiments of hHSFs with T cells were conducted, and alterations in Th1/Th2 ratios were monitored using flow cytometry. Levels of cytokines, fibrosis-associated proteins, nuclear factor-kappaB (NF-κB) pathway-related protein, and C-X-C Motif Chemokine Ligand 2 (CXCL2) were quantified using Enzyme-Linked Immunosorbent Assay or Western blot analysis. The interactions between hsa_circ_0007755, miR-27b-3p, and CXCL2 were investigated using dual-luciferase reporter assays and RNA immunoprecipitation.

Results

Both hsa_circ_0007755 and CXCL2 were highly expressed in HS, whereas miR-27b-3p was downregulated. Knockdown of hsa_circ_0007755 inhibited the proliferation and invasion of hHSFs, promoted apoptosis, and reduced the expression of fibrotic proteins α-SMA and Collagen I, as well as the phosphorylation of the inflammatory pathway protein p65. Co-culture experiments confirmed that hHSFs lowly expressing hsa_circ_0007755 showed a decreased Th1 cell proportion and an increased Th2 cell proportion, alongside lower levels of TNF-α and INF-γ and higher levels of IL-4 and IL-10. The effects of either knocking down or overexpressing hsa_circ_0007755 were reversed by knocking down either miR-27b-3p or CXCL2, respectively. hsa_circ_0007755 acted as a "molecular sponge" for miR-27b-3p, sequestering and diminishing its availability, thereby alleviating its suppression of the target gene CXCL2.

Conclusion

hsa_circ_0007755 plays a pivotal role in modulating the immune response of HS by influencing the miR-27b-3p/CXCL2 axis, regulating the function and proportion of Th1 and Th2 cells, and thereby affecting the inflammatory and fibrotic processes in scar tissue.

Presentation, Management, and Outcomes of Pathologic Scars Within a Pediatric Otolaryngology Practice

OBJECTIVES

This study aims to review the spectrum of scarring that may present to an urban, pediatric otolaryngology practice and determine if associations exist between race, scar location, treatment modality, and outcomes following interventions for scarring.

METHODS

Retrospective cohort study among 115 pediatric patients with 138 unique keloids or hypertrophic scars (HTS), and 141 children presenting for tonsillectomy at Tufts Medical Center. Age at presentation and sex assigned at birth were collected for both populations. For those presenting for pathologic scars, income quintile, self-identified race/ethnicity, anatomical location, treatment number and type, and clinical outcome were also analyzed. Multivariate analyses calculated adjusted odds ratios (aORs) and 95% confidence intervals to assess associations between scar subsite, intervention type, and persistence after treatment.

RESULTS

Compared to individuals presenting for tonsillectomy, a disproportionate percentage of patients presenting for scarring identified as Black (26.6% vs. 13.5%) or Asian (17.4% vs. 7.1%, p = 0.016) or were male (61.7% vs. 49.7%, p = 0.053). Individuals identifying as Black or Asian were more likely to present with ear lobe and neck scars, respectively (50.0% vs. 45.5%, p = <0.001). Ear scars were significantly more likely to receive excision at initial treatment (aOR = 5.86 [1.43-23.96]) compared to other subsites, and were more likely to require >1 treatment (aOR = 5.91 [1.53-22.75]).

CONCLUSION

Among pediatric patients presenting with keloids or HTS, children who identified as Black or Asian were more likely to present with ear and neck scars, respectively. Ear scars were frequently treated with excision and appear more likely to require adjuvant treatments and multiple interventions.

LEVEL OF EVIDENCE

3 Laryngoscope, 134:3127-3135, 2024.

Exosomes Derived from Hypertrophic Scar Fibroblasts Suppress Melanogenesis in Normal Human Epidermal Melanocytes

Post-burn hypertrophic scars often exhibit abnormal pigmentation. Exosomes play important roles in maintaining normal physiological homeostasis and in the pathological development of diseases. This study investigated the effects of the exosomes derived from hypertrophic scar fibroblasts (HTSFs) on melanocytes, which are pigment-producing cells. Normal fibroblasts (NFs) and HTSFs were isolated and cultured from normal skin and hypertrophic scar (HTS) tissue. Both the NF- and HTSF-exosomes were isolated from a cell culture medium and purified using a column-based technique. The normal human epidermal melanocytes were treated with both exosomes at a concentration of 100 μg/mL at different times. The cell proliferation, melanin content in the medium, apoptotic factors, transcription factors, melanin synthesis enzymes, signaling, signal transduction pathways, and activators of transcription factors (STAT) 1, 3, 5, and 6 were investigated. Compared with the Dulbecco's phosphate-buffered saline (DPBS)-treated controls and NF-exosomes, the HTSF-exosomes decreased the melanocyte proliferation and melanin secretion. The molecular patterns of apoptosis, proliferation, melanin synthesis, Smad and non-Smad signaling, and STATs were altered by the treatment with the HTSF-exosomes. No significant differences were observed between the DPBS-treated control and NF-exosome-treated cells. HTSF-derived exosomes may play a role in the pathological epidermal hypopigmentation observed in patients with HTS.

Gallic Acid Treats Hypertrophic Scar in Rabbit Ears via the TGF-β/Smad and TRPC3 Signaling Pathways

Hypertrophic scars (HSs) develop due to excessive collagen deposition and abnormal fibroblast proliferation during wound healing, significantly impacting patient quality of life. Three dosages of GA ointments were administered to rabbit ear HS models to investigate the potential efficacy and mechanism of gallic acid (GA) on HS. Daily application of ointment was performed on the matrix group, the GA ointment groups, and the silicone gel group for 28 days. (No drug treatment was performed on the skin and model groups as a blank group and vehicle group, and silicone gel ointment was topically administered to the silicone gel group as a positive control group.) Scar specimens were collected for histopathology analysis, RNA sequencing analysis, real-time quantitative polymerase chain reaction, and Western blot analysis at the first, second, and fourth weeks after the treatment. Low-dose and medium-dose GA effectively suppressed HS formation and markedly decreased fibroblast infiltration levels and scar thickness. Moreover, decreased expression of TRPC3 mRNA and TGF-β1, p-Smad2/3, and Smad2/3 protein was observed in the low- and medium-dose GA groups and the silicone gel group. This study provides evidence for the efficacy of GA in treating HS and sheds light on its potential underlying pharmacological mechanisms.

Characterization of the skin keloid microenvironment

Keloids are a fibroproliferative skin disorder that develops in people of all ages. Keloids exhibit some cancer-like behaviors, with similar genetic and epigenetic modifications in the keloid microenvironment. The keloid microenvironment is composed of keratinocytes, fibroblasts, myofibroblasts, vascular endothelial cells, immune cells, stem cells and collagen fibers. Recent advances in the study of keloids have led to novel insights into cellular communication among components of the keloid microenvironment as well as potential therapeutic targets for treating keloids. In this review, we summarized the nature of genetic and epigenetic regulation in keloid-derived fibroblasts, epithelial-to-mesenchymal transition of keratinocytes, immune cell infiltration into keloids, the differentiation of keloid-derived stem cells, endothelial-to-mesenchymal transition of vascular endothelial cells, extracellular matrix synthesis and remodeling, and uncontrolled angiogenesis in keloids with the aim of identifying new targets for therapeutic benefit. Video Abstract.

Advances in Immunomodulatory Mechanisms of Mesenchymal Stem Cells-Derived Exosome on Immune Cells in Scar Formation

Pathological scars are the result of over-repair and excessive tissue proliferation of the skin injury. It may cause serious dysfunction, resulting in psychological and physiological burdens on the patients. Currently, mesenchymal stem cells-derived exosomes (MSC-Exo) displayed a promising therapeutic effect on wound repair and scar attenuation. But the regulatory mechanisms are opinions vary. In view of inflammation has long been proven as the initial factor of wound healing and scarring, and the unique immunomodulation mechanism of MSC-Exo, the utilization of MSC-Exo may be promising therapeutic for pathological scars. However, different immune cells function differently during wound repair and scar formation. The immunoregulatory mechanism of MSC-Exo would differ among different immune cells and molecules. Herein, this review gave a comprehensive summary of MSC-Exo immunomodulating different immune cells in wound healing and scar formation to provide basic theoretical references and therapeutic exploration of inflammatory wound healing and pathological scars.

Immune cells and associated molecular markers in dermal fibrosis with focus on raised cutaneous scars

Raised dermal scars including hypertrophic, and keloid scars as well as scalp-associated fibrosing Folliculitis Keloidalis Nuchae (FKN) are a group of fibrotic raised dermal lesions that mostly occur following cutaneous injury. They are characterized by increased extracellular matrix (ECM) deposition, primarily excessive collagen type 1 production by hyperproliferative fibroblasts. The extent of ECM deposition is thought to be proportional to the severity of local skin inflammation leading to excessive fibrosis of the dermis. Due to a lack of suitable study models, therapy for raised dermal scars remains ill-defined. Immune cells and their associated markers have been strongly associated with dermal fibrosis. Therefore, modulation of the immune system and use of anti-inflammatory cytokines are of potential interest in the management of dermal fibrosis. In this review, we will discuss the importance of immune factors in the pathogenesis of raised dermal scarring. The aim here is to provide an up-to-date comprehensive review of the literature, from PubMed, Scopus, and other relevant search engines in order to describe the known immunological factors associated with raised dermal scarring. The importance of immune cells including mast cells, macrophages, lymphocytes, and relevant molecules such as cytokines, chemokines, and growth factors, antibodies, transcription factors, and other immune-associated molecules as well as tissue lymphoid aggregates identified within raised dermal scars will be presented. A growing body of evidence points to a shift from proinflammatory Th1 response to regulatory/anti-inflammatory Th2 response being associated with the development of fibrogenesis in raised dermal scarring. In summary, a better understanding of immune cells and associated molecular markers in dermal fibrosis will likely enable future development of potential immune-modulated therapeutic, diagnostic, and theranostic targets in raised dermal scarring.

Prominent Role of Type 2 Immunity in Skin Diseases-Beyond Atopic Dermatitis

Type 2 immunity, illustrated by T helper 2 lymphocytes (Th2) and downstream cytokines (IL-4, IL-13, IL-31) as well as group 2 innate lymphoid cells (ILC2), is important in host defense and wound healing.¹ The hallmark of type 2 inflammation is eosinophilia and/or high IgE counts and is best recognized in atopic diathesis. Persistent eosinophilia, such as seen in hypereosinophilic syndromes, leads to fibrosis and hence therapeutic Type 2 inhibition in fibrotic diseases is of high interest. Furthermore, as demonstrated in cutaneous T cell lymphoma, advanced disease is characterized by Th1 to Th2 switch allowing cancer progression and immunosuppression. Development of targeted monoclonal antibodies against IL-4Rα (eg, dupilumab) led to a paradigm shift for the treatment of atopic dermatitis (AD) and stimulated research to better understand the role of Type 2 inflammation in other skin conditions. In this review, we summarize up to date knowledge on the role of Type 2 inflammation in skin diseases other than AD and highlight whether the use of Type 2 targeted therapies has been documented or is being investigated in clinical trials. This manuscript reviews the role of Type 2 inflammation in dermatitis, neurodermatitis, IgE-mediated dermatoses (eg, bullous pemphigoid, chronic spontaneous urticaria), sclerodermoid conditions and skin neoplasms.

Hypertrophic Scarring: Current Knowledge of Predisposing Factors, Cellular and Molecular Mechanisms

Hypertrophic scarring (HSc) is an age-old problem that still affects millions of people physically, psychologically, and economically. Despite advances in surgical techniques and wound care, prevention and treatment of HSc remains a challenge. Elucidation of factors involved in the development of this common fibroproliferative disorder is crucial for further progress in preventive and/or therapeutic measures. Our knowledge about pathophysiology of HSc at the cellular and molecular level has grown considerably in recent decades. In this article, current knowledge of predisposing factors and the cellular and molecular mechanisms of HSc has been reviewed.

Therapeutic Strategies by Regulating Interleukin Family to Suppress Inflammation in Hypertrophic Scar and Keloid

Hypertrophic scar (HS) and keloid are fibroproliferative disorders (FPDs) of the skin due to aberrant wound healing, which cause disfigured appearance, discomfort, dysfunction, psychological stress, and patient frustration. The unclear pathogenesis behind HS and keloid is partially responsible for the clinical treatment stagnancy. However, there are now increasing evidences suggesting that inflammation is the initiator of HS and keloid formation. Interleukins are known to participate in inflammatory and immune responses, and play a critical role in wound healing and scar formation. In this review, we summarize the function of related interleukins, and focus on their potentials as the therapeutic target for the treatment of HS and keloid.

Smad‑binding decoy reduces extracellular matrix expression in human hypertrophic scar fibroblasts

The exact mechanisms underlying hypertrophic scarring is yet to be fully understood. However, excessive collagen deposition by fibroblasts has been demonstrated to result in hypertrophic scar formation, and collagen synthesis in dermal fibroblasts is regulated by the transforming growth factor-β1/Smad signaling pathway. In view of this, a Smad-binding decoy was designed and its effects on hypertrophic scar-derived human skin fibroblasts was evaluated. The results of the present study revealed that the Smad decoy attenuates the total amount of collagen, collagen I and Smad2/3 expression in scar fibroblasts. Data from RNA sequencing indicated that the Smad decoy induced more than 4-fold change in 178 genes, primarily associated with to the extracellular matrix, compared with the untreated control. In addition, results from quantitative real-time polymerase chain reaction further confirmed that the Smad decoy significantly attenuated the expression of extracellular matrix-related genes, including COL1A1, COL1A2 and COL3A1. Furthermore, the Smad decoy reduced transforming growth factor-β1-induced collagen deposition in scar fibroblasts. Data generated from the present study provide evidence supporting the use of the Smad decoy as a potential hypertrophic scar treatment.

T Cells in Fibrosis and Fibrotic Diseases

Fibrosis is the extensive deposition of fibrous connective tissue, and it is characterized by the accumulation of collagen and other extracellular matrix (ECM) components. Fibrosis is essential for wound healing and tissue repair in response to a variety of triggers, which include infection, inflammation, autoimmune disorder, degenerative disease, tumor, and injury. Fibrotic remodeling in various diseases, such as liver cirrhosis, pulmonary fibrosis, renal interstitial fibrosis, myocardial infarction, systemic sclerosis (SSc), and graft-versus-host disease (GVHD), can impair organ function, causing high morbidity and mortality. Both innate and adaptive immunity are involved in fibrogenesis. Although the roles of macrophages in fibrogenesis have been studied for many years, the underlying mechanisms concerning the manner in which T cells regulate fibrosis are not completely understood. The T cell receptor (TCR) engages the antigen and shapes the repertoire of antigen-specific T cells. Based on the divergent expression of surface molecules and cell functions, T cells are subdivided into natural killer T (NKT) cells, γδ T cells, CD8⁺ cytotoxic T lymphocytes (CTL), regulatory T (Treg) cells, T follicular regulatory (Tfr) cells, and T helper cells, including Th1, Th2, Th9, Th17, Th22, and T follicular helper (Tfh) cells. In this review, we summarize the pro-fibrotic or anti-fibrotic roles and distinct mechanisms of different T cell subsets. On reviewing the literature, we conclude that the T cell regulations are commonly disease-specific and tissue-specific. Finally, we provide perspectives on microbiota, viral infection, and metabolism, and discuss the current advancements of technologies for identifying novel targets and developing immunotherapies for intervention in fibrosis and fibrotic diseases.

The IL-4/IL-13 axis in skin fibrosis and scarring: mechanistic concepts and therapeutic targets

Skin fibrosis, characterized by excessive fibroblast proliferation and extracellular matrix deposition in the dermis, is the histopathologic hallmark of dermatologic diseases such as systemic sclerosis, hypertrophic scars, and keloids. Effective anti-scarring therapeutics remain an unmet need, underscoring the complex pathophysiologic mechanisms of skin fibrosis. The Th2 cytokines interleukin (IL)-4 and IL-13 have been implicated as key mediators in the pathogenesis of fibroproliferative disorders. The goal of this article is to summarize the current understanding of the role of the IL-4/IL-13 axis in wound healing and skin fibrosis. We conducted a literature search to identify research studies investigating the roles of IL-4 and IL-13 in fibrotic skin diseases. While transforming growth factor-beta has long been regarded as the main driver of fibrotic processes, research into the cellular and molecular biology of wound healing has revealed other pathways that promote scar tissue formation. IL-4 and IL-13 are important mediators of skin fibrosis, supported by evidence from in vitro data, animal models of fibrosis, and clinical studies. Overactive signaling of the IL-4/IL-13 axis contributes to the initiation and perpetuation of fibrotic skin diseases. Further insights into the IL-4/IL-13 axis may reveal potential targets for the development of novel therapies that prevent or treat fibrotic skin diseases.

Biological approaches for hypertrophic scars

Scar formation is usually the pathological consequence of skin trauma. And hypertrophic scars (HSs) frequently occur in people after being injured deeply. HSs are unusually considered as the result of tissue contraction and excessive extracellular matrix component deposition. Myofibroblasts, as the effector cells, mainly differentiated from fibroblasts, play the crucial role in the pathophysiology of HSs. A number of growth factors, inflammatory cytokines involved in the process of HS occurrence. Currently, with in-depth exploration and clinical research of HSs, various creative and effective treatments budded. In here, we summarize the progress in the molecular mechanism of HSs, and review the available biotherapeutic methods for their pathophysiological characteristics. Additionally, we further prospected that the comprehensive therapy may be more suitable for HS treatment.

The role of Th1/Th2 cell chemokine expression in hypertrophic scar

The aim of this study was to study the role of Th1/Th2 cell-associated chemokines in the formation of hypertrophic scars in rabbit ears. Twenty-six New Zealand white rabbits were used to establish the hypertrophic scar model of rabbit ear and the normal scar model of rabbit's back. Two rabbits were sacrificed on days 0 and 21, 28, 35, 42, 49, 56, and 63 after operation. The specimens were stained with haematoxylin-eosin (HE). Scar elevation index (SEI) was used to detect the expression of 10 chemokines related to Th1/Th2 cells in both scar formation expressions. Real-time polymerase chain reaction (PCR) results showed that two chemokines (CXCL10, CXCL12) were highly expressed during the formation of normal scar, and there was almost no expression during the formation of hypertrophic scar (*P < 0.05). The chemokines (CCL2, CCL3, CCL4, CCL5, CCL7, CCL13, CX3CL1) were almost non-expressed in the formation of normal scars but were expressed for a long time in the formation of hypertrophic scars. The four chemokines, CCL2, CCL4, CCL5, and CX3CL1, maintained a long-term high expression level during the formation of hypertrophic scars (P < 0.01). There were also three chemokines (CCL14, CCL19, CCL21) that were almost undetectable in normal scarring, but there was transiently low-level expression (P < 0.05) only during the peak proliferative phase in proliferative scarring. Th1/Th2 cell-associated chemokines are different in the type, quantity and expression, and maintenance time of rabbit ear hypertrophic scars.

Imiquimod regulating Th1 and Th2 cell-related chemokines to inhibit scar hyperplasia

Immunological factors play important roles in the occurrence of hypertrophic scars. Imiquimod can be used as an immunosuppressive agent to regulate the function of T-helper (Th) cell subsets Th1 and Th2. In this article, we explored the impact of imiquimod on scar hyperplasia through Th cells. A rabbit ear hypertrophic scar model was built. Four round wounds were cut in each rabbit's ears ventrally with a diameter of 1 cm and bilateral symmetry. All the right ear wounds were treated with 5% imiquimod cream. The blank control group contained all the left ear wounds, which were treated with Vaseline ointment at the same time. Haematoxylin and eosin and Masson staining showed that imiquimod collagen deposition was significantly reduced compared with the control group, scar index (SEI) showed that the proliferative degree reached its peak on the 28th day after operation in blank group, and the degree of hyperplasia was significantly higher than that of the imiquimod group (P < .05). Real-time Polymerase chain reaction results showed that the imiquimod induced the expression of Th2 cell-related chemokines CCL2, CCL3, CCL5, CCL7, and CCL13 at each time point, which were significantly lower than that of the blank control group, and the expressions of Th1 cell-associated chemokines CXCL10 and CXCL12 at each time point was significantly higher than the blank control group (P < .05). Imiquimod can be used to regulate the expression of Th1 and Th2 cell-associated chemokines to control scar hyperplasia.

Mesenchymal Stromal Cell Preconditioning: The Next Step Toward a Customized Treatment For Severe Burn

Over the last century, the clinical management of severe skin burns significantly progressed with the development of burn care units, topical antimicrobials, resuscitation methods, early eschar excision surgeries, and skin grafts. Despite these considerable advances, the present treatment of severe burns remains burdensome, and patients are highly susceptible to skin engraftment failure, infections, organ dysfunction, and hypertrophic scarring. Recent researches have focused on mesenchymal stromal cell (MSC) therapy and hold great promises for tissue repair, as reported in several animal studies and clinical cases. In the present review, we will provide an up-to-date outlook of the pathophysiology of severe skin burns, clinical treatment modalities and current limitations. We will then focus on MSCs and their potential in the burn wound healing both in in vitro and in vivo studies. A specific attention will be paid to the cell preconditioning approach, as a means of improving the MSC efficacy in the treatment of major skin burns. In particular, we will debate how several preconditioning cues would modulate the MSC properties to better match up with the burn pathophysiology in the course of the cell therapy. Finally, we will discuss the clinical interest and feasibility of a MSC-based therapy in comparison to their paracrine derivatives, including microvesicles and conditioned media for the treatment of major skin burn injuries.

Computational analysis identifies putative prognostic biomarkers of pathological scarring in skin wounds

Background

Pathological scarring in wounds is a prevalent clinical outcome with limited prognostic options. The objective of this study was to investigate whether cellular signaling proteins could be used as prognostic biomarkers of pathological scarring in traumatic skin wounds.

Methods

We used our previously developed and validated computational model of injury-initiated wound healing to simulate the time courses for platelets, 6 cell types, and 21 proteins involved in the inflammatory and proliferative phases of wound healing. Next, we analysed thousands of simulated wound-healing scenarios to identify those that resulted in pathological (i.e., excessive) scarring. Then, we identified candidate proteins that were elevated (or decreased) at the early stages of wound healing in those simulations and could therefore serve as predictive biomarkers of pathological scarring outcomes. Finally, we performed logistic regression analysis and calculated the area under the receiver operating characteristic curve to quantitatively assess the predictive accuracy of the model-identified putative biomarkers.

Results

We identified three proteins (interleukin-10, tissue inhibitor of matrix metalloproteinase-1, and fibronectin) whose levels were elevated in pathological scars as early as 2 weeks post-wounding and could predict a pathological scarring outcome occurring 40 days after wounding with 80% accuracy.

Conclusion

Our method for predicting putative prognostic wound-outcome biomarkers may serve as an effective means to guide the identification of proteins predictive of pathological scarring.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1406-x) contains supplementary material, which is available to authorized users.

Dermis, acellular dermal matrix, and fibroblasts from different layers of pig skin exhibit different profibrotic characteristics: evidence from in vivo study

To explore the profibrotic characteristics of the autografted dermis, acellular dermal matrix, and dermal fibroblasts from superficial/deep layers of pig skin, 93 wounds were established on the dorsa of 7 pigs. 72 wounds autografted with the superficial/deep dermis and acellular dermal matrix served as the superficial/deep dermis and acellular dermal matrix group, respectively, and were sampled at 2, 4, and 8 weeks post-wounding. 21 wounds autografted with/without superficial/deep dermal fibroblasts served as the superficial/deep dermal fibroblast group and the control group, respectively, and were sampled at 2 weeks post-wounding. The hematoxylin and eosin staining showed that the wounded skin thicknesses in the deep dermis group (superficial acellular dermal matrix group) were significantly greater than those in the superficial dermis group (deep acellular dermal matrix group) at each time point, the thickness of the cutting plane in the deep dermal fibroblast group was significantly greater than that in the superficial dermal fibroblast group and the control group. The western blots showed that the α-smooth muscle actin expression in the deep dermis group (superficial acellular dermal matrix group) was significantly greater than that in the superficial dermis group (deep acellular dermal matrix group) at each time point. In summary, the deep dermis and dermal fibroblasts exhibited more profibrotic characteristics than the superficial ones, on the contrary, the deep acellular dermal matrix exhibited less profibrotic characteristics than the superficial one.

Important Developments in Burn Care

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Explain the epidemiology of severe burn injury in the context of socioeconomic status, gender, age, and burn cause. 2. Describe challenges with burn depth evaluation and novel methods of adjunctive assessment. 3. Summarize the survival and functional outcomes of severe burn injury. 4. State strategies of fluid resuscitation, endpoints to guide fluid titration, and sequelae of overresuscitation. 5. Recognize preventative measures of sepsis. 6. Explain intraoperative strategies to improve patient outcomes, including hemostasis, restrictive transfusion, temperature regulation, skin substitutes, and Meek skin grafting. 7. Translate updates in the pathophysiology of hypertrophic scarring into novel methods of clinical management. 8. Discuss the potential role of free tissue transfer in primary and secondary burn reconstruction.

SUMMARY

Management of burn-injured patients is a challenging and unique field for plastic surgeons. Significant advances over the past decade have occurred in resuscitation, burn wound management, sepsis, and reconstruction that have improved outcomes and quality of life after thermal injury. However, as patients with larger burns are resuscitated, an increased risk of nosocomial infections, sepsis, compartment syndromes, and venous thromboembolic phenomena have required adjustments in care to maintain quality of life after injury. This article outlines a number of recent developments in burn care that illustrate the evolution of the field to assist plastic surgeons involved in burn care.

Biological Principles of Scar and Contracture

Hypertrophic scar and contracture in burn patients is a complex process. Contributing factors include critical injury depth and activation of key cell subpopulations, including deep dermal fibroblasts, myofibroblasts, fibrocytes, and T-helper cells, which cause scarring rather than regeneration. These cells influence each other via cellular profibrotic and antifibrotic signals, which help to determine the outcome. These cells also both modify and interact with extracellular matrix of the wound, ultimately forming hypertrophic scar. Current treatments reduce hypertrophic scar formation or improve remodeling by targeting these pathways and signals.

Transplanting Human Skin Grafts onto Nude Mice to Model Skin Scars

Hypertrophic scar (HTS) is a common outcome of deep dermal wound healing mainly followed mechanical, chemical, and thermal injuries in the skin. Because of the lack of the most effective prevention and treatment, it is particularly important to establish an ideal dermal animal model for improving the understanding of the pathogenesis and exploring therapeutic approaches of HTS. Compared to other dermal fibrotic animal models in rabbits, red Duroc pigs, guinea pigs, rats, and mice, the approach that uses normal human split-thickness skin grafted onto nude or other immunodeficient mice which develop scars that resemble human HTS offers the advantages of lower cost, easier manipulation, and shorter research period. In this chapter, we will introduce the detailed procedures to create the ideal dermal fibrotic mouse model.

Association of plasminogen activator inhibitor-1 and vitamin D receptor expression with the risk of keloid disease in a Chinese population

Keloid disease (KD) is a benign fibroproliferative scarring condition of unknown etiopathogenesis. Plasminogen activator inhibitor-1 (PAI-1) and vitamin D receptor (VDR) have been shown to play important roles in the progression of tissue fibrosis; therefore, both these genes are potential susceptibility genes for KD. We aimed to determine whether the gene expression levels of PAI-1 and VDR are altered in Chinese KD patients. We measured the expression of PAI and VDR in human peripheral blood lymphocytes in 236 patients with keloid and 219 age- and sex-matched healthy controls by quantitative real-time polymerase chain reaction. We found that PAI-1 expression in peripheral blood lymphocytes was significantly higher in patients with KD than in control individuals (p < 0.0001), while VDR expression was significantly lower in KD patients than in control individuals (p < 0.0001). High levels of PAI-1 and low levels of VDR expression were significantly associated with an increased risk for KD. PAI-1 and VDR might play important roles in keloid development. Gene expression levels of PAI-1 and VDR may, therefore, be used as potential markers for the prediction of keloid development after scarring.

The evidence for natural therapeutics as potential anti-scarring agents in burn-related scarring

Though survival rate following severe thermal injuries has improved, the incidence and treatment of scarring have not improved at the same speed. This review discusses the formation of scars and in particular the formation of hypertrophic scars. Further, though there is as yet no gold standard treatment for the prevention or treatment of scarring, a brief overview is included. A number of natural therapeutics have shown beneficial effects both in vivo and in vitro with the potential of becoming clinical therapeutics in the future. These natural therapeutics include both plant-based products such as resveratrol, quercetin and epigallocatechin gallate as examples and includes the non-plant-based therapeutic honey. The review also includes potential mechanism of action for the therapeutics, any recorded adverse events and current administration of the therapeutics used. This review discusses a number of potential 'treatments' that may reduce or even prevent scarring particularly hypertrophic scarring, which is associated with thermal injuries without compromising wound repair.

Innate and adaptive immunity gene expression of human keratinocytes cultured of severe burn injury

PURPOSE

Evaluate the expression profile of genes related to Innate and Adaptive Immune System (IAIS) of human Primary Epidermal keratinocytes (hPEKP) of patients with severe burns.

METHODS

After obtaining viable fragments of skin with and without burning, culture hKEP was initiated by the enzymatic method using Dispase (Sigma-Aldrich). These cells were treated with Trizol(r) (Life Technologies) for extraction of total RNA. This was quantified and analyzed for purity for obtaining cDNA for the analysis of gene expression using specific IAIS PCR Arrays plates (SA Biosciences).

RESULTS

After the analysis of gene expression we found that 63% of these genes were differentially expressed, of which 77% were repressed and 23% were hyper-regulated. Among these, the following genes (fold increase or decrease): IL8 (41), IL6 (32), TNF (-92), HLA-E (-86), LYS (-74), CCR6 (- 73), CD86 (-41) and HLA-A (-35).

CONCLUSIONS

This study contributes to the understanding of the molecular mechanisms underlying wound infection caused by the burn. Furthermore, it may provide new strategies to restore normal expression of these genes and thereby change the healing process and improve clinical outcome.

A novel subpopulation of peripheral blood mononuclear cells presents in major burn patients

Hypertrophic scars (HTS) are generally believed to result from proliferation and activation of resident connective tissue fibroblasts after burns. To demonstrate a potential role of blood-borne cells, the peripheral blood mononuclear cells (PBMCs) and the effect of PBMCs on dermal fibroblast behavior was investigated. Flow cytometry was used to analyze the surface and intracellular protein expression of PBMCs and fibroblasts. Transwell migration assay, enzyme-linked immunosorbent assay and real-time reverse transcription polymerase chain reaction was performed to assess fibroblast functions. We identified a novel subpopulation of PBMCs in burn patients in vivo that appears at an early stage following major thermal injuries, which primarily express procollagen 1, leukocyte specific protein 1, CD204, toll-like receptor 4 and stromal cell-derived factor 1 (SDF-1) receptor CXCR4. In vitro, the conditioned media from burn patient PBMCs up-regulated the expression of fibrotic growth factors and extracellular matrix molecules, down-regulated antifibrotic factor decorin, enhanced cell chemotaxis and promoted cell differentiation into contractile myofibroblasts in dermal fibroblasts. After thermal injury, this novel subpopulation of PBMCs is systemically triggered and attracted to the wounds under SDF-1/CXCR4 signaling where they appear to modulate the functions of resident connective tissue cells and thus contribute to the development of HTS.

In vivo profiling reveals immunomodulatory effects of sorafenib and dacarbazine on melanoma

Sorafenib is a multi-kinase inhibitor used alone or in combination with dacarbazine to treat metastasized melanoma. Our study investigated the relationship between metabolic response assessed by PET-CT and global transcriptome changes during sorafenib and dacarbazine therapy in patients with advanced melanoma. We conducted an open-label, investigator-initiated study that enrolled 13 sorafenib-naïve Stage IV melanoma patients, whose metastases were accessible for repeated biopsies. Treatment regimen included orally administered sorafenib and intravenous dacarbazine. Biopsies of skin or superficial lymph node metastases were taken before treatment (baseline), during sorafenib and after dacarbazine therapy and used for transcriptional profiling and validation experiments. Serum samples were evaluated for cytokine production. Metabolic response to therapy was observed in 45.5% of patients. The study drugs were well tolerated. We observed a clear upregulation of interferon (IFN)-stimulated immune response genes in profiled metastases. The IFNγ-induced gene signature seemed to be enhanced after addition of dacarbazine to sorafenib. Serum IFNγ also increased during therapy, particularly after addition of dacarbazine. Induction of IFNγ stimulated genes correlating with increased serum IFNγ was predictive of better clinical outcome and responders who had significantly higher serum IFNγ levels lived longer. Our data reveal in situ changes in melanoma metastases during treatment with sorafenib and dacarbazine and suggest an additional mechanism of action through immunomodulation.

Interleukin-12 preserves the cutaneous physical and immunological barrier after radiation exposure

The United States continues to be a prime target for attack by terrorist organizations in which nuclear detonation and dispersal of radiological material are legitimate threats. Such attacks could have devastating consequences to large populations, in the form of radiation injury to various human organ systems. One of these at risk organs is the cutaneous system, which forms both a physical and immunological barrier to the surrounding environment and is particularly sensitive to ionizing radiation. Therefore, increased efforts to develop medical countermeasures for treatment of the deleterious effects of cutaneous radiation exposure are essential. Interleukin-12 (IL-12) was shown to elicit protective effects against radiation injury on radiosensitive systems such as the bone marrow and gastrointestinal tract. In this article, we examined if IL-12 could protect the cutaneous system from a combined radiation injury in the form of sublethal total body irradiation and beta-radiation burn (β-burn) directly to the skin. Combined radiation injury resulted in a breakdown in skin integrity as measured by transepidermal water loss, size of β-burn lesion and an exacerbated loss of surveillant cutaneous dendritic cells. Interestingly, intradermal administration of IL-12 48 h postirradiation reduced transepidermal water loss and burn size, as well as retention of cutaneous dendritic cells. Our data identify IL-12 as a potential mitigator of radiation-induced skin injury and argue for the further development of this cytokine as a radiation countermeasure.

Burn wound γδ T-cells support a Th2 and Th17 immune response

Major burn triggers immune dysfunction, which is associated with wound healing complications. Gamma-δ T-cells have been shown to be important in postburn inflammation and wound healing; however, their cytokine phenotype at the burn wound site is unknown. C57BL/6 male mice were subjected to a major burn (25% TBSA, third degree) or sham treatment. At 3 hours, 3 days, and 7 days thereafter, skin samples were collected and subjected to dispase and trypsin digestion to isolate single cells. The cells were phenotyped and evaluated for cytokine profiles by flow cytometry. Th1 cells were defined as interferon (IFN)γ positive, Th2 cells were defined as interleukin (IL)-10 positive, and Th17 cells were defined as IL-17 positive. At 7 days after burn a shift toward Th2 and Th17 positive T-cells at the wound site was observed. Further analysis revealed that at 3-hour postinjury the percentage of γδ T-cells positive for IFNγ, IL-10, and IL-17 were comparable between sham and burn skin samples. At 3 days and 7 days postinjury the percentage of cells positive for each cytokine increased; however, the increase was significantly greater for IL-10 and IL-17, as compared with IFNγ (ie, 9-20-fold vs 3-fold). Skin αβ T-cells preferentially produced IFNγ (~20%), which was unaffected by burn injury. These data demonstrate that burn wound γδ T-cells are activated for enhanced cytokine production and display a shift toward a Th2 and/or Th17 phenotype. In contrast, burn wound αβ T-cells were not activated for enhanced cytokine production.

Biology and principles of scar management and burn reconstruction

Hypertrophic scarring is extremely common and is the source of most morbidity related to burns. The biology of hypertrophic healing is complex and poorly understood. Multiple host and injury factors contribute, but protracted healing of partial thickness injury is a common theme. Hypertrophic scarring and heterotopic ossification may share some basic causes involving marrow-derived cells. Several traditional clinical interventions exist to modify hypertrophic scar. All have limited efficacy. Laser interventions for scar modification show promise, but as yet do not provide a definitive solution. Their efficacy is only seen when used as part of a multimodality scar management program.

Disclosure of the Culprits: Macrophages-Versatile Regulators of Wound Healing

SIGNIFICANCE

Macrophages are invariably present and tightly regulate all phases of adult wound healing, including inflammation, granulation tissue formation, and matrix deposition with the unavoidable outcome of scar formation. In response to environmental cues, macrophages mount a "classical" pro-inflammatory M1 activation as opposed to the "alternative" M2 phenotype, with wound macrophages having long been viewed as M2 macrophages.

RECENT ADVANCES

Recent studies rather point to large temporal and phenotypic variations of wound macrophages subsets. Therefore, a functional classification of macrophages according to wound-healing phases appears to better meet the in vivo complexity. In an ideal but simplistic scenario grossly reflecting normal wound healing, initial tissue injury induces inflammatory M1-like macrophages, which, upon engulfment of apoptotic neutrophils or in response to other inflammation dampening stimuli, switch toward anti-inflammatory M2-like macrophages and further toward growth factor-producing pro-fibrotic M2a-like macrophages. Although not yet documented for skin wounds, a subset of metalloproteinase-producing fibrolytic M2c-like macrophages may contribute to fibrosis resolution. Recent work identified a diversity of novel macrophage phenotypes associated with normal and pathologic wound healing, most of them ranging out of the M1/M2 paradigm. Iron-overloaded M1-like macrophages represent such a novel phenotypic subset driving the non-healing state of chronic venous leg ulcers.

CRITICAL ISSUES

Despite growing evidence that macrophage dysfunctions are, at least in part, responsible for pathologic wound healing, including nonhealing wounds and excessive scar formation, these are hardly specifically addressed even by modern therapeutic strategies.

FUTURE DIRECTIONS

If characterized in sufficient detail, distinct macrophage subsets and their impaired functions provide ideal targets for improving wound healing.

Detrimental dermal wound healing: what can we learn from the oral mucosa?

Wounds in adults are frequently accompanied by scar formation. This scar can become fibrotic due to an imbalance between extracellular matrix (ECM) synthesis and ECM degradation. Oral mucosal wounds, however, heal in an accelerated fashion, displaying minimal scar formation. The exact mechanisms of scarless oral healing are yet to be revealed. This review highlights possible mechanisms involved in the difference between scar-forming dermal vs. scarless oral mucosal wound healing. Differences were found in expression of ECM components, such as procollagen I and tenascin-C. Oral wounds contained fewer immune mediators, blood vessels, and profibrotic mediators but had more bone marrow-derived cells, a higher reepithelialization rate, and faster proliferation of fibroblasts compared with dermal wounds. These results form a basis for further research that should be focused on the relations among ECM, immune cells, growth factors, and fibroblast phenotypes, as understanding scarless oral mucosal healing may ultimately lead to novel therapeutic strategies to prevent fibrotic scars.

Site-specific immunophenotyping of keloid disease demonstrates immune upregulation and the presence of lymphoid aggregates

BACKGROUND

Keloid disease (KD) is a common fibroproliferative disorder of unknown aetiology. T cells and macrophages are increased in KD and are thought to contribute to its pathogenesis. However, while a link between inflammation and fibrotic disorders is well known for other disorders, it remains undetermined in KD.

OBJECTIVES

Systematically to immunophenotype the inflammatory infiltrate of KD in situ in a site-specific manner, and to compare this with normal skin and scar tissue.

METHODS

Sixty-eight keloid cases were screened for the presence of all three (intralesional, perilesional and extralesional) keloid-associated specific tissue sites. Subsequently, a complete set of 25 keloid biopsies (from different patients) was compared with normal skin (n = 11) and normal scar (n = 11) samples and subjected to systematic, site-specific quantitative immunohistomorphometry and histochemistry, using a range of immunological markers of B cells, T cells, macrophages, mast cells (MCs) and Langerhans cells.

RESULTS

T cells, B cells, degranulated and mature MCs (coexpressing OX40 ligand) and alternative macrophages (M2) were all significantly increased in intralesional and perilesional KD sites compared with normal skin and scar tissue (P < 0·05). Additionally, 10 of 68 KD cases (15%) showed the presence of distinctive lymphoid aggregates, which resembled mucosa-associated lymphoid tissue (MALT).

CONCLUSIONS

The increased number and activity of MCs and M2 may implicate inflammation in the fibrotic process in KD. The distinct KD-associated lymphoid aggregate resembles MALT, for which we propose the term 'keloid-associated lymphoid tissue' (KALT). It may perpetuate inflammatory stimuli that promote KD growth. KALT, MCs and M2 are promising novel targets for future KD therapy.

The molecular mechanism of hypertrophic scar

Hypertrophic scar (HTS) is a dermal form of fibroproliferative disorder which often develops after thermal or traumatic injury to the deep regions of the skin and is characterized by excessive deposition and alterations in morphology of collagen and other extracellular matrix (ECM) proteins. HTS are cosmetically disfiguring and can cause functional problems that often recur despite surgical attempts to remove or improve the scars. In this review, the roles of various fibrotic and anti-fibrotic molecules are discussed in order to improve our understanding of the molecular mechanism of the pathogenesis of HTS. These molecules include growth factors, cytokines, ECM molecules, and proteolytic enzymes. By exploring the mechanisms of this form of dermal fibrosis, we seek to provide some insight into this form of dermal fibrosis that may allow clinicians to improve treatment and prevention in the future.

Transdermal siRNA-TGFβ1-337 patch for hypertrophic scar treatment

Hypertrophic scarring (HSc) is a fibroproliferative disorder of the dermis characterized by erythematous, swollen, and pruritic lesions of healing skin. An increased understanding of the role of TGFβ1 in the development of HSc provides the potential for treating HSc by down-regulating TGFβ1 expression. siRNAs that effectively interfered with TGFβ1 expression were screened. It was concluded that the siRNA-TGFβ1-337 was able to effectively down-regulate TGFβ1 expression in HSc fibroblasts. The effects of siRNA-TGFβ1-337 on cell proliferation, cell cycle, and apoptosis of HSc fibroblasts were investigated. It was shown that it inhibited cell proliferation, arrested cells in the G1 stage of the cell cycle, and induced apoptosis of HSc fibroblasts. The transdermal patch of siRNA-TGFβ1-337 was a combination of siRNA-TGFβ1-337 and a pressure-sensitive adhesive hydrogel. The treatment effects of the transdermal patch were assessed in an animal model established by transplanting human HSc to nude mice. Decreased expression of TGFβ1 was observed with treatment with the transdermal siRNA-TGFβ1-337 patch. Consequently, the treatment resulted in type I collagen down-regulation and regularly arranged scar fibroblasts being significantly reduced and undergoing apoptosis; the scar size was decreased significantly. Thus, our findings indicate that a transdermal siRNA-TGFβ1-337 patch is a potential treatment for hypertrophic scars.

CD4+ T Lymphocytes, especially Th2 cells, contribute to the progress of renal fibrosis

BACKGROUND

Renal tubulointerstitial fibrosis is the final common stage of renal failure. CD4+ T lymphocyte recruitment and activation after injury could be the very important early event that mediates the onset of renal fibrogenesis. But the role of CD4+ T lymphocytes in renal fibrosis is controversial and its cellular mechanism needs to be further investigated.

METHODS

Biopsy specimens were from patients with minimal-change or IgA nephropathy. Mouse renal fibrosis was induced by unilateral ureteral obstruction (UUO). CD4+ T lymphocytes of wild BALB/c mice were depleted with anti-CD4 antibody. BALB/c Nu/Nu mice were reconstituted with polarized Th1 or Th2 cells by tail vein injection.

RESULTS

Our study demonstrated that massive CD4+ T lymphocytes infiltrated fibrotic kidneys of patients. The depletion of CD4+ T lymphocytes inhibited UUO-induced mouse renal fibrosis. In the process of UUO-induced renal fibrosis, the ratios of Th2/Th1 increased with time. Results have also shown that Th2-reconstituted mice developed renal fibrosis more easily than Th1-reconstituted mice, which manifested by interstitial expansion and collagen deposition, higher expression of α-SMA and vimentin and increased expression of fibronectin, TGF-β and collagen I. We also found that CD4+ T cells from Th1-reconstitued mice tended to secrete IL-4 and IL-13 Th2-like cytokines.

CONCLUSION

In conclusion, our study demonstrated the importance of CD4+ T lymphocytes in renal fibrosis and gave the first direct evidence that Th2 cells play a pivotal role in UUO-induced renal fibrosis. Inhibition of CD4+ T lymphocyte differentiation to Th2 would be a potential therapeutic intervention to prevent renal fibrosis.

Wound healing in adult skin: aiming for perfect regeneration

Wound healing in adult skin, a complex process involving many cell types and processes such as epidermal, fibroblastic, and endothelial cell proliferation, cell migration, matrix synthesis, and wound contraction, almost invariably results in scar tissue formation and wound induration. Unlike in adult skin, wound healing in embryos involves repair processes that result in the essentially perfect regeneration of damaged tissue. This paper discusses key mechanisms that lead to scar tissue formation in adult human skin and treatment modalities, including curcumin gel, that may result in essentially perfect skin regeneration following surgical procedures.

Mechanical force prolongs acute inflammation via T-cell-dependent pathways during scar formation

Mechanical force significantly modulates both inflammation and fibrosis, yet the fundamental mechanisms that regulate these interactions remain poorly understood. Here we performed microarray analysis to compare gene expression in mechanically loaded wounds vs. unloaded control wounds in an established murine hypertrophic scar (HTS) model. We identified 853 mechanically regulated genes (false discovery rate <2) at d 14 postinjury, a subset of which were enriched for T-cell-regulated pathways. To substantiate the role of T cells in scar mechanotransduction, we applied the HTS model to T-cell-deficient mice and wild-type mice. We found that scar formation in T-cell-deficient mice was reduced by almost 9-fold (P < 0.001) with attenuated epidermal (by 2.6-fold, P < 0.01) and dermal (3.9-fold, P < 0.05) proliferation. Mechanical stimulation was highly associated with sustained T-cell-dependent Th2 cytokine (IL-4 and IL-13) and chemokine (MCP-1) signaling. Further, T-cell-deficient mice failed to recruit systemic inflammatory cells such as macrophages or monocytic fibroblast precursors in response to mechanical loading. These findings indicate that T-cell-regulated fibrogenic pathways are highly mechanoresponsive and suggest that mechanical forces induce a chronic-like inflammatory state through immune-dependent activation of both local and systemic cell populations.

Lack of Th17 cell generation in patients with severe burn injuries

Immunodeficient patients with severe burn injuries are extremely susceptible to infection with Candida albicans. In addition to Th1 cells, IL-17-producing CD4(+) T cells (Th17 cells) have recently been described as an important effector cell in host anti-Candida resistance. In this study, therefore, we tried to induce Th17 cells in cultures of severely burned patient PBMC by stimulation with the C. albicans Ag (CAg). In the results, the biomarkers for Th17 cells (IL-17 production and intracellular expression of IL-17 and retinoic acid receptor-related orphan receptor γt) were not displayed by burn patient PBMC stimulated with CAg, whereas these biomarkers of Th17 cells were detected in cultures of healthy donor PBMC stimulated with CAg. Burn patient sera were shown to be inhibitory on CAg-stimulated Th17 cell generation in healthy donor PBMC cultures; however, Th17 cells were induced by CAg in healthy donor PBMC cultures supplemented with burn patient sera that were previously treated with anti-IL-10 mAb. Also, the biomarkers of Th17 cells were not induced by CAg in healthy donor PBMC cultures supplemented with rIL-10. IL-10 was detected in serum specimens derived from severely burned patients. These results indicate that Th17 cells are not generated in burn patient PBMC cultures supplemented with CAg. IL-10, produced in response to burn injuries, is shown to be inhibitory on Th17 cell generation. The high susceptibility of severely burned patients to C. albicans infection might be influenced if burn-associated IL-10 production is intervened.

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

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

Burn injury suppresses human dermal dendritic cell and Langerhans cell function

Human skin contains epidermal Langerhans cells (LCs) and dermal dendritic cells (DCs) that are key players in induction of adaptive immunity upon infection. After major burn injury, suppressed adaptive immunity has been observed in patients. Here we demonstrate that burn injury affects adaptive immunity by altering both epidermal LC and dermal DC functions. We developed a human ex vivo burn injury model to study the function of DCs in thermally injured skin. No differences were observed in the capacity of both LCs and dermal DCs to migrate out of burned skin compared to unburned skin. Similarly, expression levels of co-stimulatory molecules were unaltered. Notably, we observed a strong reduction of T cell activation induced by antigen presenting cell (APC) subsets that migrated from burned skin through soluble burn factors. Further analyses demonstrated that both epidermal LCs and dermal DCs have a decreased T cell stimulatory capacity after burn injury. Restoring the T cell stimulatory capacity of DC subsets might improve tissue regeneration in patients with burn wounds.