The use of human deceased donor skin allograft in burn care

NovoSorb® Biodegradable Temporising Matrix (BTM): What we learned from the first 300 consecutive cases

INTRODUCTION

Extensive full-thickness soft-tissue defects remain a challenge in reconstructive surgery. NovoSorb® Biodegradable Temporising Matrix (BTM) represents a novel dermal substitute and was evaluated in wounds deriving from different aetiologies and to highlight risk factors for poor take rates.

METHODS

All patients treated with BTM at our department between March 2020 and October 2022 were included. Differences in univariate and linear regression models identified predictors and risk factors for take rates of BTM and split-thickness skin grafts (STSG).

RESULTS

Three hundred patients (mean age 54.2 ± 20.1 years, 66.3% male, 59.7% burns, 19.7% trauma and 20.6% others) were evaluated. Mean take rates of BTM and STSG after BTM delamination were 82.7 ± 25.2% and 86.0 ± 22.6%, respectively. Multiple regression analyses showed that higher body mass index (BMI, OR 0.43, 95% CI 0.86, -0.01, p = 0.44), prior allograft transplantation (OR 15.12, 95% CI 26.98, -3.31, p = 0.041), longer trauma-to-BTM-application intervals (OR 0.01, 95% CI 0.001, -0.001, p = 0.038), positive wound swabs before BTM (OR 7.15, 95% CI 13.50, -0.80, p = 0.028) and peripheral artery disease (OR 10.80, 95% CI 18.63, -2.96, p = 0.007) were associated with poorer BTM take. Higher BMI (OR 0.40, 95% CI 0.76, -0.08, p = 0.026), increasing BTM graft surface areas (OR 0.58, 95% CI -1.00, -0.17, p = 0.005), prior allograft (OR 12.20, 95% CI -21.99, -2.41, p = 0.015) or autograft transplantations (OR 22.42, 95% CI 38.69, -6.14, p = 0.001), tumour as the aetiology of the wound (OR 37.42, 95% CI 57.41, -17.83, p = 0.001), diabetes (OR 6.64, 95% CI 12.80, -0.48, p = 0.035) and impaired kidney function (OR 5.90, 95% CI 10.94, -0.86, p = 0.021) were associated with poorer STSG take after delamination of BTM, whereas higher BTM take rates were associated with better STSG take (OR 0.40, 95% CI 0.31,0.50, p < 0.001).

CONCLUSION

Extensive complex wounds of different aetiologies unsuitable for immediate STSG can be successfully reconstructed by means of two-staged BTM application and subsequent skin grafting. Importantly, presence of wound contamination or infection and prior allograft coverage appear to jeopardise good BTM and STSG take.

Current Approaches to Wound Repair in Burns: How far Have we Come From Cover to Close? A Narrative Review

Burn injuries are a significant global health concern, with more than 11 million people requiring medical intervention each year and approximately 180,000 deaths annually. Despite progress in health and social care, burn injuries continue to result in socioeconomic burdens for victims and their families. The management of severe burn injuries involves preventing and treating burn shock and promoting skin repair through a two-step procedure of covering and closing the wound. Currently, split-thickness/full-thickness skin autografts are the gold standard for permanent skin substitution. However, deep burns treated with split-thickness skin autografts may contract, leading to functional and appearance issues. Conversely, defects treated with full-thickness skin autografts often result in more satisfactory function and appearance. The development of tissue-engineered dermal templates has further expanded the scope of wound repair, providing scar reductive and regenerative properties that have extended their use to reconstructive surgical interventions. Although their interactions with the wound microenvironment are not fully understood, these templates have shown potential in local infection control. This narrative review discusses the current state of wound repair in burn injuries, focusing on the progress made from wound cover to wound closure and local infection control. Advancements in technology and therapies hold promise for improving the outcomes for burn injury patients. Understanding the underlying mechanisms of wound repair and tissue regeneration may provide new insights for developing more effective treatments in the future.

Organization of Hannover Skin Bank: Sterile culture and procurement protocols for viable cryopreserved allogeneic skin grafts of living donors

Preserved allogeneic donor skin still represents one of the gold standard therapies in temporary wound coverage in severely burned patients or chronic wounds. Allogeneic skin grafts are currently commercially available as cryo- or glycerol-preserved allografts through skin tissue banks all over the world. Most of the skin tissue banks rely on human cadaveric skin donations. Due to the chronic shortage of human allogeneic transplants, such as skin, and increasing costs in the procurement of allografts from other skin tissue banks, Hannover Medical School has been building up its own skin tissue bank based on allogeneic skin grafts from living donors who underwent surgical treatment (i.e., body-contouring procedures, such as abdominioplasties). This article presents procedures and protocols for the procurement and processing of allogeneic skin grafts according to national legislation and European regulations and guidelines. Beside protocols, initial microbiological data regarding the sterility of the harvested grafts are presented. The results currently form the basis for further investigations as well as clinical applications. In summary, a microbiological testing and acceptance procedure is presented that ensures adequate patient safety and skin viability.

Human amniotic membranes as an allogenic biological dressing for the treatment of burn wounds: Protocol for a randomized-controlled study

Background

Burn wounds pose significant challenges in medical treatment due to their devastating nature and resource-intensive requirements. Temporary coverage of burn wounds using synthetic or biological dressings allows for reepithelization before definitive skin grafting. Allogenic skin grafts have been widely used but come with drawbacks such as rejection and disease transmission. The use of amniotic membranes (AMs) offers a promising alternative for temporary coverage, as they possess biological properties that promote faster healing and improved scar quality. The various components of the amniotic membrane, including pluripotent stem cells, extracellular matrix proteins, and regenerative factors, contribute to cell growth, migration, and differentiation, as well as preservation of the original epithelial phenotype.

Objective

Reliable information on the treatment of burn wounds with AM is needed. The knowledge gained in this project may help to include this advantageous modern concept of biological dressings in clinical practice. The purpose of this study is to use human amniotic membranes from our in hospital laboratory, as an allogenic biological dressing after enzymatic debridement in superficial partial thickness, deep partial thickness or full thickness burn wounds.

Methods

We will include 30 patients in a randomized-controlled trial with each patient receiving the study intervention and the control intervention. Two 7 × 7 cm burn wound areas will be compared regarding percentage of skin graft take, healing time, healing percentage value and total healing time. Human amniotic membranes will be compared to allogenic skin grafts.

Progress in bioprinting technology for tissue regeneration

In recent years, due to the increase in diseases that require organ/tissue transplantation and the limited donor, on the other hand, patients have lost hope of recovery and organ transplantation. Regenerative medicine is one of the new sciences that promises a bright future for these patients by providing solutions to repair, improve function, and replace tissue. One of the technologies used in regenerative medicine is three-dimensional (3D) bioprinters. Bioprinting is a new strategy that is the basis for starting a global revolution in the field of medical sciences and has attracted much attention. 3D bioprinters use a combination of advanced biology and cell science, computer science, and materials science to create complex bio-hybrid structures for various applications. The capacity to use this technology can be demonstrated in regenerative medicine to make various connective tissues, such as skin, cartilage, and bone. One of the essential parts of a 3D bioprinter is the bio-ink. Bio-ink is a combination of biologically active molecules, cells, and biomaterials that make the printed product. In this review, we examine the main bioprinting strategies, such as inkjet printing, laser, and extrusion-based bioprinting, as well as some of their applications.

The Role of Cell-Based Therapies in Acute Burn Wound Skin Repair: A Review

Tissue engineering solutions for skin have been developed over the last few decades with a focus initially on a two-layered structure with epithelial and dermal repair. An essential element of skin restoration is a source of cells capable of differentiating into the appropriate phenotype. The need to repair areas of skin when traditional techniques were not adequate addressed led to cell based therapies being developed initially as a laboratory-based tissue expansion opportunity, both as sheets of cultured epithelial autograft and in composite laboratory-based skin substitutes. The time to availability of the cell-based therapies has been solved in a number of ways, from using allograft cell-based solutions to the use of point of care skin cell harvesting for immediate clinical use. More recently pluripotential cells have been explored providing a readily available source of cells and cells which can express the broad range of phenotypes seen in the mature skin construct. The lessons learnt from the use of cell based techniques has driven the exploration of the use of 3D printing technology, with controlled accurate placement of the cells within a specific printed construct to optimise the phenotypic expression and tissue generation.

Skin Grafting, Cryopreservation, and Diseases: A Review Article

Food supplements may be consumed through diet and have been shown to modify skin functions, making them helpful in the management of skin aging. However, there are not many clinical trials that back up these assertions. The stratum corneum, which acts as the organism's contact with its environment, is the principal function of the epidermis of land vertebrates. Antioxidants are chemicals that slow down or prevent other molecules from oxidizing. In people's diets, their use has considerably expanded in recent years. Due to their benefits for health, nutrition, and therapy, natural antioxidants are increasingly being used in place of synthetic antioxidant components. A popular component thought to be an antioxidant is hydrolyzed collagen. With aging comes a steady loss of physiological integrity, capacity to handle stress from the inside out, and function. This is a byproduct of several intricate biological processes that are affected by diseases both local and systemic as well as constitutive and environmental variables. Systemic and constitutive (genetic) variables influence skin aging and its phenotypic manifestation. The biological process of skin aging is complicated and impacted by both external and endogenous causes. The primary contributor to skin cancer is sun exposure. Ultraviolet radiation from the sun can kill skin cells by directly absorbing DNA damage. The skin's hydration is a crucial factor that affects its mechanical and physical characteristics. This study looks at how the stratum corneum's molecular and macroscopic characteristics interact and change with skin wetness. Although there is little information written about them and even less is understood about them, moisturizers are a crucial component of a dermatologist's toolkit. There is a plethora of anticipated skin products on the market, but their true scientific function is yet unknown. These items play a well-known part in many skin problems, while occasionally being dismissed as simple cosmetics.

Human skin processing affects clinical outcome in allograft recipients

Skin allografts represent a milestone in burn patient treatment. However, skin procurement is still burdened by high rates of contamination, and validation procedures have not yet been standardized. In addition, it is not clear if tissue viability affects allograft skin outcomes. In 2120 skin samples from 610 donors, a retrospective analysis was performed to identify donor and procurement variables associated with bacterial contamination and tissue viability. Post-processing contamination was associated significantly with the donor type, cause of death, length of hospitalization, procurement site, surgeon, interval between procurement and banking, and decontamination method. Tissue viability appeared to be negatively associated with freezing. In two series of skin allograft recipients (155 and 195 patients), we evaluated the role of skin characteristics and procurement variables on clinical outcomes. We found that the length of hospitalization was associated significantly with donor age. Procalcitonin and PCR values in allograft recipients were correlated with the decontamination method. No significant associations were observed between tissue viability and clinical outcomes (length of hospitalization, cause of donor death, or inflammatory parameters) after allograft transplantation. In these large case series, we identified donor and procurement variables that may affect allograft skin recipients. The decontamination method appeared to be a critical step for skin allograft requiring better standardization.

Comamonas testosteroni bacteremia: A rare unusual pathogen detected in a burned patient: Case report and literature review

Introduction and importance

Comamonas testosteroni is a rare human pathogen that is not part of the human microbiome. There are only 51 cases reported worldwide with 7 cases resulted in death.

Case presentation

We report a case of a 16-year-old boy with an extended burn complicated by catheter-related bloodstream C. testosteroni infection.

Clinical discussion

Comamonas species are usually community-acquired pathogens that are susceptible to a wide variety of antibiotics including aminoglycosides, fluoroquinolones, carbapenems, piperacillin-tazobactam, trimethoprim-sulfamethoxazole, and cephalosporins. However, in our case, we reported a nosocomial multidrug-resistant infection by C. testosteroni that responded only to colistin.

Conclusion

Reporting unusual cases of nosocomial sepsis due to rare multidrug-resistant pathogens is detrimental. As it sheds light on how virulent nosocomial infections are becoming, and can be very alarming to other practitioners and clinical microbiologists, in order to achieve a better awareness of the importance of controlled antibiotics use.

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Comamonas testosteroni is a rare human pathogen that is not part of the human microbiome, and is rarely recognized as a human pathogen.

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The majority of C.testosteroni infections are community-acquired rather than nosocomial. Most of the previously reported patients were immunodeficient (burn patient in our case).

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Till now, there are 51 cases reported (52 if our case is published) which most of these are due to intra-abdominal source.

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Comamonas species are usually susceptible to a wide spectrum of antibiotics. However, we report a nosocomial infection by C. testosterone which was sensitive only to colistin.

Sterilized human skin graft with a dose of 25 kGy provides a privileged immune and collagen microenvironment in the adhesion of Nude mice wounds

This study aimed to report the effects of different doses of ionizing radiation on inflammatory and repair stage of human skin graft adherence in Nude mice wounds. Animals were divided into transplanted with irradiated human skin grafts (IHSG) at 25 and 50 kGy (IHSG 25 kGy; IHSG 50 kGy) and non-IHSG and euthanized on the 3rd, 7th and 21st days after the surgery, by gross and microscopic changes, immunostaining for human type I collagen (Col I) and mouse Col I and Col III and inflammatory cells. We found an effectiveness of human split-thickness graft adherence in mice transplanted with IHSG 25 kGy, as well decrease in dermo-epidermal necrosis and neutrophils, lower loss of skin thickness, epithelization and neo-vascularization. Day 21 post-transplantation with IHSG 25 kGy was observed a well-preserved human skin in the border of the graft, a prominent granulation tissue in an organization by proliferated fibroblasts, Col III deposition and increased B-cells and macrophages. A complete adherence of human skin graft occurred with IHSG 25 kGy. We suggest that the ionizing radiation at 25 kGy mediates inflammation and the repair stage of human skin graft adherence in murine model, thus emerging as a potential tool in healing cutaneous wounds.

Applications of electrospun scaffolds with enlarged pores in tissue engineering

Despite electrospinning has multiple advantages over other methods such as creating materials with superfine fiber diameter, high specific surface area, and good mechanical properties, the pore diameter of scaffolds prepared...

An Anhydrous Sodium Chloride Skin Preservation Model for Studies on Keratinocytes Grafting into the Wounds

Background. Human skin is needed for covering large body areas lost by trauma. The shortcomings of contemporary methods of skin storage are limited preservation time and high immunogenicity if allogeneic. Methods. We investigated whether long-lasting skin preservation in anhydrous sodium chloride (NaCl) may be the source of keratinocytes (KCs) for transplantation. Dehydrated skin fragments were preserved for a time frame from 1 week to 12 months. Then, skin fragments were rehydrated, and KCs were isolated. The viability of KCs was assessed in viability/cytotoxicity test. NaCl-preserved KCs were cultured for 7 days and transplanted to the dorsum of SCID mice. Results. The morphology of NaCl-preserved KCs was unaltered. KCs from all epidermal layers could be identified. All grafts were accepted by the recipients. Transplanted KCs: synthesized keratins 10 and 16 expressed antigens specific for stem cells and transient-amplifying cells, and remained HLA-I-positive. Moreover, they expressed the proliferative marker PCNA. Cells isolated from transplants remained viable and produced enzymes. Conclusions. Transplantation of KCs obtained from human skin and stored in anhydrous NaCl may be considered for the closure of extensive skin wounds. The originality of this method consists of an effective storage procedure and easy preparation of keratinocytes for transplantation.

Edward F. Adolph Distinguished Lecture. It's more than skin deep: thermoregulatory and cardiovascular consequences of severe burn injuries in humans

Each year, within the United States, tens of thousands of individuals are hospitalized for burn-related injuries. The treatment of deep burns often involves skin grafts to accelerate healing and reduce the risk of infection. The grafting procedure results in a physical disruption between the injured and subsequently debrided host site and the skin graft placed on top of that site. Both neural and vascular connections must occur between the host site and the graft for neural modulation of skin blood flow to take place. Furthermore, evaporative cooling from such burn injured areas is effectively absent, leading to greatly impaired thermoregulatory responses in individuals with large portions of their body surface area burned. Hospitalization following a burn injury can last weeks to months, with cardiovascular and metabolic consequences of such injuries having the potential to adversely affect the burn survivor for years postdischarge. With that background, the objectives of this article are to discuss 1) our current understanding of the physiology and associated consequences of skin grafting, 2) the effects of skin grafts on efferent thermoregulatory responses and the associated consequences pertaining to whole body thermoregulation, 3) approaches that may reduce the risk of excessive hyperthermia in burn survivors, 4) the long-term cardiovascular consequences of burn injuries, and 5) the extent to which burn survivors can "normalize" otherwise compromised cardiovascular responses. Our primary objective is to guide the reader toward an understanding that severe burn injuries result in significant physiological consequences that can persist for years after the injury.

Engineered Pullulan-Collagen-Gold Nano Composite Improves Mesenchymal Stem Cells Neural Differentiation and Inflammatory Regulation

Tissue repair engineering supported by nanoparticles and stem cells has been demonstrated as being an efficient strategy for promoting the healing potential during the regeneration of damaged tissues. In the current study, we prepared various nanomaterials including pure Pul, pure Col, Pul–Col, Pul–Au, Pul–Col–Au, and Col–Au to investigate their physicochemical properties, biocompatibility, biological functions, differentiation capacities, and anti-inflammatory abilities through in vitro and in vivo assessments. The physicochemical properties were characterized by SEM, DLS assay, contact angle measurements, UV-Vis spectra, FTIR spectra, SERS, and XPS analysis. The biocompatibility results demonstrated Pul–Col–Au enhanced cell viability, promoted anti-oxidative ability for MSCs and HSFs, and inhibited monocyte and platelet activation. Pul–Col–Au also induced the lowest cell apoptosis and facilitated the MMP activities. Moreover, we evaluated the efficacy of Pul–Col–Au in the enhancement of neuronal differentiation capacities for MSCs. Our animal models elucidated better biocompatibility, as well as the promotion of endothelialization after implanting Pul–Col–Au for a period of one month. The above evidence indicates the excellent biocompatibility, enhancement of neuronal differentiation, and anti-inflammatory capacities, suggesting that the combination of pullulan, collagen, and Au nanoparticles can be potential nanocomposites for neuronal repair, as well as skin tissue regeneration in any further clinical treatments.

The Use of Allograft Skin for the Treatment of Darier Disease

Darier disease is an autosomal dominant skin disorder characterized by keratotic papules. After their appearance, these lesions tend to grow over time, producing large and exudative plaques that compromise the general condition of the affected patient's skin. The authors report the clinical case of a patient affected by Darier disease with superinfected de-epithelialized areas over 30% of his body. In addition to antibiotic and antifungal therapy, providers used allograft skin to cover the injured areas and stimulate their progressive re-epithelialization with complete healing after 2 months. To the authors' knowledge, this is the first clinical case of treating Darier disease with allograft skin on an extensively damaged area. The effectiveness of this treatment may lead clinicians to consider allograft skin tissue a new, alternative dressing to treat Darier disease when this pathologic condition manifests with extensive eroded skin.

Intra-Operative Bioprinting of Hard, Soft, and Hard/Soft Composite Tissues for Craniomaxillofacial Reconstruction

Reconstruction of complex craniomaxillofacial (CMF) defects is challenging due to the highly organized layering of multiple tissue types. Such compartmentalization necessitates the precise and effective use of cells and other biologics to recapitulate the native tissue anatomy. In this study, intra-operative bioprinting (IOB) of different CMF tissues, including bone, skin, and composite (hard/soft) tissues, is demonstrated directly on rats in a surgical setting. A novel extrudable osteogenic hard tissue ink is introduced, which induced substantial bone regeneration, with ≈80% bone coverage area of calvarial defects in 6 weeks. Using droplet-based bioprinting, the soft tissue ink accelerated the reconstruction of full-thickness skin defects and facilitated up to 60% wound closure in 6 days. Most importantly, the use of a hybrid IOB approach is unveiled to reconstitute hard/soft composite tissues in a stratified arrangement with controlled spatial bioink deposition conforming the shape of a new composite defect model, which resulted in ≈80% skin wound closure in 10 days and 50% bone coverage area at Week 6. The presented approach will be absolutely unique in the clinical realm of CMF defects and will have a significant impact on translating bioprinting technologies into the clinic in the future.

Utility of Porcine-Derived Xenograft as an Adjunct to Split-Thickness Skin Grafting in Lower-Extremity Wounds

OBJECTIVE

Porcine-derived xenograft biological dressings (PXBDs) are occasionally used to prepare chronic wound beds for definitive closure before split-thickness skin grafts (STSGs). We sought to determine whether PXBD influences rate of STSG take in lower-extremity wounds.

METHODS

Lower-extremity wounds treated with STSGs were retrospectively reviewed. Patients were included in one of two groups: wound bed preparation with PXBD before STSG or no preparation. Patients were excluded if they received wound bed preparation via another method. Patient demographics, comorbidities, wound history, wound bed preparation, and 30- and 60-day outcomes were collected.

RESULTS

There was no difference in healing outcomes between the PXBD (n = 27) and no preparation (n = 39) groups. At 30- and 60-day follow-up, percentage of STSG take was not significantly different between groups (77.9% versus 79.0%, P30 = .818; 82.2% versus 80.9%, P60 = .422). Mean wound sizes at these follow-up periods were not different (4.4 cm2 versus 5.1 cm2, P30 = .902; 1.2 cm2 versus 1.1 cm2, P60 = .689). The PXBD group had a higher mean ± SD hemoglobin A1c level (8.3 ± 3.5 versus 6.9 ± 1.6; P = .074) and age (64.9 ± 12.8 years versus 56.3 ± 11.9 years; P = .007) versus the no preparation group.

CONCLUSIONS

Application of PXBDs for wound bed preparation had no effect on wound healing compared with no wound bed preparation. The two groups varied only by mean age and hemoglobin A1c level. The PXBD may be beneficial, but these results call for randomized controlled trials to determine the true impact of PXBDs on wound healing. In addition, PXBDs may have utility outside of clinically oriented outcomes, and future work should address patient-reported outcomes and pain scores with this adjunct.

Clinical Applications of Allograft Skin in Burn Care

Allograft skin has been widely used for wound management in burn centers. Functional as biologic dressing, it can not only provide ideal temporary wound coverage in extensive burns when autograft is not immediately available but also prepare the wound bed for definitive autografting. In this article, the up-to-date clinical application of allograft in burn care was reviewed, including coverage of extensive burn wounds, combined use with meshed autograft, template for delayed application of cultured epidermal autografts, and the use of human acellular dermal matrix. Although it has potential disadvantages of rejection and disease transmission, allograft skin remains a workhorse in treatment of severe burn wounds.

Ovine model of burn wounds grafted with ovine cadaver skin

Shortage in autograft to cover burn wounds involves a frequent use of cadaver skin (CS) as a temporary cover to prevent infection, dehydration and preparation of wounds for subsequent autografting. We aimed to establish an ovine model of burn wound healing using ovine CS (OCS). Quality and efficacy of fresh and frozen OCS overlaid on to excised 3rd degree flame burn wounds in sheep were evaluated in comparison to autograft. Histologically, autografted wounds maintained normal skin structure at different time points. Wounds overlaid with fresh OCS graft showed signs of rejection starting from day 7. At day 14, the epidermis was mostly rejected. The rejection was completed by day 20 with signs of immunoreaction and presence of many immune cells. Frozen OCS was rejected in the same pattern. Immediately prior to grafting, the thickness was comparable between freshly prepared and frozen OCS for 10 or 40 days. Significant reduction in viability was detected in OCS frozen for 40 days. Both fresh or frozen ovine OCS were rejected within 10 days that mimics CS rejection time in humans (∼8.4 days), suggesting that ovine model of burn wound grafted with OCS can successfully be used in burn wound research mimicking clinical scenario.

The Optimal Treatment for Partial Thickness Burns: A Cost-Utility Analysis of Skin Allograft vs. Topical Silver Dressings

INTRODUCTION

Partial thickness burns not undergoing surgical excision are treated with topical silver products including silver sulfadiazine (SSD) and Mepilex Ag. Skin allograft is a more costly alternative that acts as definitive wound coverage until autogenous epithelialization. Economic constraints and the movement toward value-based care demand cost and outcome justification prior to adopting more costly products.

METHODS

A cost-utility analysis was performed comparing skin allograft to SSD and Mepilex Ag using decision tree analysis. The base case modeled a superficial partial thickness 20% total body surface area burn. Utilities were derived from expert opinion on the basis of personal experience. Costs were derived from 2019 Medicare payments. Quality adjusted life years were calculated using rollback method assuming standard life expectancies in the United States. Probabilistic sensitivity analysis was performed to asses model robustness.

RESULTS

The incremental costs of skin allograft to Mepilex Ag and SSD were $907.71 and $1257.86, respectively. The incremental quality adjusted life year (QALY) gains from allograft over Mepilex Ag and SSD were 0.011 and 0.016. This yielded an incremental cost-utility ratio for allograft vs. Mepilex Ag of $84,189.29/QALY compared with an incremental cost-utility ratio of $79,684.63/QALY for allograft vs. SSD. Assuming willingness-to-pay thresholds of $100,000/QALY, probabilistic sensitivity analysis demonstrated that allograft was cost effective to Mepilex Ag in 62.1% of scenarios, and cost effective to SSD in 64.9% of simulations.

CONCLUSION

Skin allograft showed greater QALYs compared with topical silver dressings at a higher cost. Depending on willingness-to-pay thresholds, skin allograft may be a considered a cost-effective treatment of partial-thickness burns.

Long-term expansion of directly reprogrammed keratinocyte-like cells and in vitro reconstitution of human skin

Background

Human keratinocytes and derived products are crucial for skin repair and regeneration. Despite substantial advances in engineered skin equivalents, their poor availability and immunorejection remain major challenges in skin grafting.

Methods

Induced keratinocyte-like cells (iKCs) were directly reprogrammed from human urine cells by retroviral transduction of two lineage-specific transcription factors BMI1 and △NP63α (BN). Expression of keratinocyte stem cell or their differentiation markers were assessed by PCR, immunofluorescence and RNA-Sequencing. Regeneration capacity of iKCs were assessed by reconstitution of a human skin equivalent under air-interface condition.

Results

BN-driven iKCs were similar to primary keratinocytes (pKCs) in terms of their morphology, protein expression, differentiation potential, and global gene expression. Moreover, BN-iKCs self-assembled to form stratified skin equivalents in vitro.

Conclusions

This study demonstrated an approach to generate human iKCs that could be directly reprogrammed from human somatic cells and extensively expanded in serum- and feeder cell-free systems, which will facilitate their broad applicability in an efficient and patient-specific manner.

Human Skin Allograft: Is it a Viable Option in Management of Burn Patients?

Tangential excision and autologous split-thickness skin grafting is the standard management of the burn wound, but autograft has limitation of donor-site availability and morbidity. Human skin allograft is an alternate option of wound coverage when autograft is not available. Various synthetic skin substitute dressings are now available in the market, and thus use of human skin allograft has decreased. This case report explores the role of human skin allograft in burn wound management. Allograft facilitates excision of burn wounds during acute phase of burn injury in pediatric patients. It is cost-effective, reduces pain and risk of infection, and avoids frequent dressing changes. Availability of allograft and risk of infection are the two main constraints in its regular use.

Local Expression of Indoleamine 2,3, Dioxygenase Prolongs Allogenic Skin Graft Take in a Mouse Model

Background and Objective: Despite the effectiveness of skin autotransplantation, the high degree of immunogenicity of the skin precludes the use of allografts and systemic immunosuppression is generally inappropriate for isolated skin grafts. Indoleamine 2,3 dioxygenase (IDO) is a potent immunoregulatory factor with allo- and autoimmune suppression and tolerance induction properties. This study examines the potential use of locally expressed IDO to prolong the allogeneic skin graft take in a mouse model. Approach: Syngeneic-fibroblasts were transfected with noncompetent IDO viral vector and the level of Kynurenine (Kyn) in conditioned medium was measured as an index for IDO activity. Either 1 or 3 × 10⁶ IDO-fibroblasts were introduced intra/hypo-dermally to the mouse skin. The expression, localization, and functionality of IDO were then evaluated. The cell-injected areas were harvested and grafted on the back of allogeneic mice. The graft survival, immune-cells infiltration, and interaction with dendritic cells were evaluated. Results: The results showed a significant improvement in allogeneic graft take injected with 1 × 106 IDO-fibroblasts (18.4 ± 3.3 days) compared with control (12.2 ± 1.9 days). This duration increased to 35.4 ± 4.7 days in grafts injected with 3 × 10⁶ IDO-expressing cells. This observation might be due to a significantly lower T cells infiltration within the IDO-grafts. Further, the result of a flow cytometric analysis showed that the expression of PD-L1/PD-L2 on CD11c+/eFluor+ cells in the regional lymph nodes of injected skin areas was significantly higher in IDO groups compared with control. Conclusion: These data suggest that allogeneic skin graft survival outcome can be prolonged significantly by local overexpression of IDO without any systemic effect.

The impact of skin allograft on inpatient outcomes in the treatment of major burns 20-50% total body surface area - A propensity score matched analysis using the nationwide inpatient sample

BACKGROUND

Human cadaveric skin (allograft) is used in treating major burns both as temporizing wound coverage and a means of testing wound bed viability following burn excision. There is limited information on outcomes, and clinicians disagree on indications for application in intermediate-sized burns. This study aims to improve understanding of allograft use in 20-50% total body surface burns by assessing current utilization and evaluating inpatient outcomes.

METHODS

Discharge data from the Nationwide Inpatient Sample (NIS), Healthcare Cost and Utilization Project (HCUP), Agency for Healthcare Research and Quality assessed 3557 major burn patients (>second degree depth and 20-50% TBSA) undergoing operative treatment. Outcomes were evaluated with propensity score matching. The primary outcome was mortality with secondary outcomes including complications, length of stay, total burn operations, and charges.

RESULTS

After matching, 771 allografted patients were paired with 1774 controls. Covariate mean standard differences were all <11% after matching. The average treatment effect (ATE) of allograft on inpatient mortality was an increase of 2.8% (95% CI 0.2-5.3%, p=0.041). Allograft ATEs were all significantly higher for secondary outcomes: composite complication index increased 0.13 (95% CI 0.07-0.20, p<0.001), length of stay 8.4days (95% CI 6.1-1.9 days, p<0.001), total burn operations 1.6 (95% CI 1.4-1.9, p<0.001), and total charges $139,476 [$100,716-178,236, p<0.001).

CONCLUSIONS

Allograft use in major burns 20-50% TBSA was associated with a significant increase in inpatient mortality. There was a notable correlation with increased inpatient complications, longer length of stay, more burn operations, and greater total charges. Better studies are needed to justify the use of this costly and limited resource in the intermediate sized major burn population.

Scar management in burn injuries using drug delivery and molecular signaling: Current treatments and future directions

In recent decades, there have been tremendous improvements in burn care that have allowed patients to survive severe burn injuries that were once fatal. However, a major limitation of burn care currently is the development of hypertrophic scars in approximately 70% of patients. This significantly decreases the quality of life for patients due to the physical and psychosocial symptoms associated with scarring. Current approaches to manage scarring include surgical techniques and non-surgical methods such as laser therapy, steroid injections, and compression therapy. These treatments are limited in their effectiveness and regularly fail to manage symptoms. As a result, the development of novel treatments that aim to improve outcomes and quality of life is imperative. Drug delivery that targets the molecular cascades of wound healing to attenuate or prevent hypertrophic scarring is a promising approach that has therapeutic potential. In this review, we discuss current treatments for scar management after burn injury, and how drug delivery targeting molecular signaling can lead to new therapeutic strategies.

Stem cells, niches and scaffolds: Applications to burns and wound care

The importance of skin to survival, and the devastating physical and psychological consequences of scarring following reparative healing of extensive or difficult to heal human wounds, cannot be disputed. We discuss the significant challenges faced by patients and healthcare providers alike in treating these wounds. New state of the art technologies have provided remarkable insights into the role of skin stem and progenitor cells and their niches in maintaining skin homeostasis and in reparative wound healing. Based on this knowledge, we examine different approaches to repair extensive burn injury and chronic wounds, including full and split thickness skin grafts, temporising matrices and scaffolds, and composite cultured skin products. Notable developments include next generation skin substitutes to replace split thickness skin autografts and next generation gene editing coupled with cell therapies to treat genodermatoses. Further refinements are predicted with the advent of bioprinting technologies, and newly defined biomaterials and autologous cell sources that can be engineered to more accurately replicate human skin architecture, function and cosmesis. These advances will undoubtedly improve quality of life for patients with extensive burns and difficult to heal wounds.

Immunological challenges associated with artificial skin grafts: available solutions and stem cells in future design of synthetic skin

The repair or replacement of damaged skins is still an important, challenging public health problem. Immune acceptance and long-term survival of skin grafts represent the major problem to overcome in grafting given that in most situations autografts cannot be used. The emergence of artificial skin substitutes provides alternative treatment with the capacity to reduce the dependency on the increasing demand of cadaver skin grafts. Over the years, considerable research efforts have focused on strategies for skin repair or permanent skin graft transplantations. Available skin substitutes include pre- or post-transplantation treatments of donor cells, stem cell-based therapies, and skin equivalents composed of bio-engineered acellular or cellular skin substitutes. However, skin substitutes are still prone to immunological rejection, and as such, there is currently no skin substitute available to overcome this phenomenon. This review focuses on the mechanisms of skin rejection and tolerance induction and outlines in detail current available strategies and alternatives that may allow achieving full-thickness skin replacement and repair.

Creation of Nepal's First Skin Bank: Challenges and Outcomes

Background

In Nepal, burn trauma causes more than 55,000 injuries each year. Burn-related mortality is high in Nepal, in part due to lack of allograft, leading to high infection rates. To address this challenge, our collaboration between Kirtipur Hospital, America Nepal Medical Foundation, Stanford University, and ReSurge International established Nepal's first skin bank.

Methods

We identified 3 major tasks to create a sustainable skin banking program: 1) identify and acquire the equipment and personnel needed to collect, process, store, and graft cadaveric skin for burn injuries; 2) develop safe donation protocols and documentation tools that remain feasible for low-resource settings; and 3) develop a long-term awareness program to educate the Nepali people on skin donation, a previously foreign concept.

Results

Kirtipur Hospital acquired the necessary equipment and materials for the skin bank through a combination of local and international fundraising efforts. Existing U.S. skin banking protocols were adapted for the Nepali setting and piloted on potential patients, donors, and physicians. For the first time in the hospital's history, patients with > 40% total body surface area burns were successfully treated with extensive allografts.

Conclusions

It is feasible to create a skin bank in a country with no tradition of allograft skin use. Long-term sustainability now depends on spreading awareness and education in the Kathmandu Valley to overcome religious and cultural barriers that have hindered donor recruitment. Our low-cost and high-impact skin bank provides a model to expand this system to other hospitals both within Nepal and beyond.

Hypertrophic scarring: the greatest unmet challenge after burn injury

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

Smoke inhalation increases intensive care requirements and morbidity in paediatric burns

Burn survival has improved with advancements in fluid resuscitation, surgical wound management, wound dressings, access to antibiotics and nutritional support for burn patients. Despite these advancements, the presence of smoke inhalation injury in addition to a cutaneous burn still significantly increases morbidity and mortality. The pathophysiology of smoke inhalation has been well studied in animal models. Translation of this knowledge into effectiveness of clinical management and correlation with patient outcomes including the paediatric population, is still limited. We retrospectively reviewed our experience of 13 years of paediatric burns admitted to a regional burn's intensive care unit. We compared critical care requirements and patient outcomes between those with cutaneous burns only and those with concurrent smoke inhalation injury. Smoke inhalation increases critical care requirements and mortality in the paediatric burn population. Therefore, early critical care input in the management of these patients is advised.

Rigenera protocol in the treatment of surgical wound dehiscence

The effective management of post-operative wounds is important to prevent potential complications such as surgical-site infections and wound dehiscence. The purpose of this study was to treat wound dehiscence in elderly patients who were subjected to orthopaedic surgical interventions. The dehisced wounds were treated with autologous micro-grafts obtained using a promising CE-certified medical device called Rigeneracons. This instrument is a biological disruptor of human tissues able to specifically select progenitor cells that, as already reported in previous studies, maintain high cell viability but mainly have a high regenerative potential, allowing the repair of damaged tissues. Autologous micro-grafts obtained by Rigeneracons are ready to use and can be applied alone or in combination with biological scaffolds directly on the injured area. We observed in our patients a complete remission of dehisced wounds, on average, after 30 days from micro-grafts application and a total wound re-epithelialisation after 1 year from the surgical intervention. In conclusion, although we reported only three patients, autologous micro-grafts can be considered a promising approach for the treatment of dehisced wounds, improving the wound-healing process and in general the patient's quality of life without using other dressings.

Application areas of 3D bioprinting

Three dimensional (3D) bioprinting has been a powerful tool in patterning and precisely placing biologics, including living cells, nucleic acids, drug particles, proteins and growth factors, to recapitulate tissue anatomy, biology and physiology. Since the first time of cytoscribing cells demonstrated in 1986, bioprinting has made a substantial leap forward, particularly in the past 10 years, and it has been widely used in fabrication of living tissues for various application areas. The technology has been recently commercialized by several emerging businesses, and bioprinters and bioprinted tissues have gained significant interest in medicine and pharmaceutics. This Keynote review presents the bioprinting technology and covers a first-time comprehensive overview of its application areas from tissue engineering and regenerative medicine to pharmaceutics and cancer research.

Assessment of cryopreserved donor skin viability: the experience of the regional tissue bank of Siena

Skin allografts from cadaver donors are an important resource for treating extensive burns, slow-healing wounds and chronic ulcers. A high level of cell viability of cryopreserved allografts is often required, especially in burn surgery, in Italy. Thus, we aimed to determine which conditions enable procurement of highly viable skin in our Regional Skin Bank of Siena. For this purpose, we assessed cell viability of cryopreserved skin allografts procured between 2011 and 2013 from 127 consecutive skin donors, before and after freezing (at day 15, 180, and 365). For each skin donor, we collected data concerning clinical history (age, sex, smoking, phototype, dyslipidemia, diabetes, cause of death), donation process (multi-tissue or multi-organ) and timing of skin procurement (assessment of intervals such as death-harvesting, harvesting-banking, death-banking). All these variables were analysed in the whole case study (127 donors) and in different groups (e.g. multi-organ donors, non refrigerated multi-tissue donors, refrigerated multi-tissue donors) for correlations with cell viability. Our results indicated that cryopreserved skin allografts with higher cell viability were obtained from female, non smoker, heartbeating donors died of cerebral haemorrhage, and were harvested within 2 h of aortic clamping and banked within 12 h of harvesting (13-14 h from clamping). Age, cause of death and dyslipidaemia or diabetes did not appear to influence cell viability. To maintain acceptable cell viability, our skin bank needs to reduce the time interval between harvesting and banking, especially for refrigerated donors.

Development of a biological scaffold engineered using the extracellular matrix secreted by skeletal muscle cells

The performance of implantable biomaterials derived from decellularized tissue, including encouraging results with skeletal muscle, suggests that the extracellular matrix (ECM) derived from native tissue has promising regenerative potential. Yet, the supply of biomaterials derived from donated tissue will always be limited, which is why the in-vitro fabrication of ECM biomaterials that mimic the properties of tissue is an attractive alternative. Towards this end, our group has utilized a novel method to collect the ECM that skeletal muscle myoblasts secrete and form it into implantable scaffolds. The cell derived ECM contained several matrix constituents, including collagen and fibronectin that were also identified within skeletal muscle samples. The ECM was organized into a porous network that could be formed with the elongated and aligned architecture observed within muscle samples. The ECM material supported the attachment and in-vitro proliferation of cells, suggesting effectiveness for cell transplantation, and was well tolerated by the host when examined in-vivo. The results suggest that the ECM collection approach can be used to produce biomaterials with compositions and structures that are similar to muscle samples, and while the physical properties may not yet match muscle values, the in-vitro and in-vivo results indicate it may be a suitable first generation alternative to tissue derived biomaterials.

Acellular dermal matrix-based gene therapy augments graft incorporation

BACKGROUND

Acellular dermal matrix (ADM) is widely used for structural or dermal replacement purposes. Given its innate biocompatibility and its potential to vascularize, we explored the possibility of ADM to function as a small interfering RNA (siRNA) delivery system. Specifically, we sought to improve ADM vascularization by siRNA-mediated inhibition of prolyl hydroxylase domain-2 (PHD2), a cytoplasmic protein that regulates hypoxia inducible factor-1α, and improve neovascularization.

MATERIALS AND METHODS

Fluorescently labeled siRNA was used to rehydrate thin implantable ADM. Pharmacokinetic release of siRNA was determined. Twelve millimeter sections of ADM reconstituted with PHD2 siRNA (nonsense siRNA as control) and applied to dorsal wounds of 40 FVB mice. Grafts were sewn in, bolstered, and covered with occlusive dressings. Photographs were taken at 0, 7, and 14 d. Wounds were harvested at 7 and 14 d and analyzed (messenger RNA, protein, histology, and immunohistochemistry).

RESULTS

Release kinetics was first-order with 80% release by 12 h. By day 14, PHD2-containing ADM appeared viable and adherent, whereas controls appeared nonviable and nonadherent. Real-time reverse transcription-polymerase chain reaction demonstrated near-complete knockdown of PHD2, whereas vascular endothelial growth factor and FGF-2 were increased 2.3- and 4.7-fold. On enzyme-linked immunosorbent assay, vascular endothelial growth factor was increased more than fourfold and stromal cell-derived factor doubled. Histology demonstrated improved graft incorporation in treated groups. Immunohistochemical demonstrated increased vascularity measured by CD31 staining and increased new cell proliferation by denser proliferating cell nuclear antigen staining in treated versus controls.

CONCLUSIONS

We concluded that ADM is an effective matrix for local delivery of siRNA. Strategies to improve the matrix and/or genetically alter the local tissue environment can be envisioned.

The effects of constant flow bioreactor cultivation and keratinocyte seeding densities on prevascularized organotypic skin grafts based on a fibrin scaffold

Organotypic full-thickness skin grafts (OTSG) are already an important technology for treating various skin conditions and are well established for skin research and development. These obvious benefits are often impaired by the need of laborious production, their noncomplete autologous composition, and, most importantly, their lack of included vasculature. Therefore, our study focused on combining a prevascularized dermal layer with an epidermis to cultivate full-thickness skin grafts incorporating capillary-like networks. It has been shown that prevascularization accelerates ingrowth of tissue-engineered grafts, and it is a prerequisite to circumvent diffusion limits due to graft thickness. To obtain such a graft, we chose a dermal layer incorporating human umbilical vein endothelial cells (HuVEC) amid human dermal fibroblasts within a fibrin-based scaffold, seeded apically with human foreskin keratinocytes (hfKC). Our research investigated the used concept's feasibility, as well as the effect of hfKC addition on the development of a well-connected capillary-like network after approximately 21 days. In addition, we evaluated the utilization of a custom-made constant flow bioreactor for simplified cultivation of these grafts, therefore possibly easing graft production and presumably increasing their cost effectiveness. Skin grafts were assessed by conventional two-dimensional histology. In addition, software-assisted three-dimensional evaluation of the capillary-like structure networks was performed by two-photon laser scanning microscopy (TPLSM) and subsequent image processing was done with ImagePro(®) Analyzer 7.0 software, thereby evaluating its platform technology power in the field of prevascularized skin grafts. All samples showed a capillary-like structure network, but we could report a significant reduction of its total length after 14 days of tri-culture with 5×10(5)/cm(2) seeded hfKC, possibly indicating nutritional deficiencies for this particular high cell density experimental setup. Lower concentrations of hfKC did not affect the formation of the capillary-like structures significantly. The developed bioreactor simplified cultivation of prevascularized OTSG. However, a flow-dependent reduction of capillary-like structures in 1 and 5 mL/min flow conditions occurred. We conclude that our technique for creating prevascularized OTSG is feasible. In addition, TPLSM is well suited for analyzing the prevascularization process. We hypothesize that the handling benefits of our bioreactor can be preserved by using considerably lower flow rates while not impairing the forming of capillary-like structure networks.

Genetically modified porcine split-thickness skin grafts as an alternative to allograft for provision of temporary wound coverage: preliminary characterization

Temporary coverage of severely burned patients with cadaver allograft skin represents an important component of burn care, but is limited by availability and cost. Porcine skin shares many physical properties with human skin, but is susceptible to hyperacute rejection due to preformed antibodies to α-1,3-galactose (Gal), a carbohydrate on all porcine cells. Our preliminary studies have suggested that skin grafts from α-1,3-galactosyltransferase knock out (GalT-KO) miniature swine might provide temporary wound coverage comparable to allografts, since GalT-KO swine lack this carbohydrate. To further evaluate this possibility, eight non-human primates received primary autologous, allogeneic, GalT-KO, and GalT+xenogeneic skin grafts. Additionally, secondary grafts were placed to assess whether sensitization would affect the rejection time course of identical-type grafts. We demonstrate that both GalT-KO xenografts and allografts provide temporary coverage of partial- and full-thickness wounds for up to 11 days. In contrast, GalT+xenografts displayed hyperacute rejection, with no signs of vascularization and rapid avulsion from wounds. Furthermore, secondary GalT-KO transplants failed to vascularize, demonstrating that primary graft rejection sensitizes the recipient. We conclude that GalT-KO xenografts may provide temporary coverage of wounds for a duration equivalent to allografts, and thus, could serve as a readily available alternative treatment of severe burns.

Novel, silver-ion-releasing nanofibrous scaffolds exhibit excellent antibacterial efficacy without the use of silver nanoparticles

Nanofibers, with their morphological similarities to the extracellular matrix of skin, hold great potential for skin tissue engineering. Over the last decade, silver nanoparticles have been extensively investigated in wound-healing applications for their ability to provide antimicrobial benefits to nanofibrous scaffolds. However, the use of silver nanoparticles has raised concerns as these particles can penetrate into the stratum corneum of skin, or even diffuse into the cellular plasma membrane. We present and evaluate a new silver ion release polymeric coating that we have found can be applied to biocompatible, biodegradable poly(l-lactic acid) nanofibrous scaffolds. Using this compound, custom antimicrobial silver-ion-releasing nanofibers were created. The presence of a uniform, continuous silver coating on the nanofibrous scaffolds was verified by XPS analysis. The antimicrobial efficacy of the antimicrobial scaffolds against Staphylococcus aureus and Escherichia coli bacteria was determined via industry-standard AATCC protocols. Cytotoxicity analyses of the antimicrobial scaffolds toward human epidermal keratinocytes and human dermal fibroblasts were performed via quantitative analyses of cell viability and proliferation. Our results indicated that the custom antimicrobial scaffolds exhibited excellent antimicrobial properties while also maintaining human skin cell viability and proliferation for silver ion concentrations below 62.5μgml(-1) within the coating solution. This is the first study to show that silver ions can be effectively delivered with nanofibrous scaffolds without the use of silver nanoparticles.