Intracutaneous Transplantation of Islets Within a Biodegradable Temporizing Matrix as an Alternative Site for Islet Transplantation.

Intrahepatic islet transplantation for type 1 diabetes is limited by the need for multiple infusions and poor islet viability posttransplantation. The development of alternative transplantation sites is necessary to improve islet survival and facilitate monitoring and retrieval. We tested a clinically proven biodegradable temporizing matrix (BTM), a polyurethane-based scaffold, to generate a well-vascularized intracutaneous "neodermis" within the skin for islet transplantation. In murine models, BTM did not impair syngeneic islet renal-subcapsular transplant viability or function, and it facilitated diabetes cure for over 150 days. Furthermore, BTM supported functional neonatal porcine islet transplants into RAG-1-/- mice for 400 days. Hence, BTM is nontoxic for islets. Two-photon intravital imaging used to map vessel growth through time identified dense vascular networks, with significant collagen deposition and increases in vessel mass up to 30 days after BTM implantation. In a preclinical porcine skin model, BTM implants created a highly vascularized intracutaneous site by day 7 postimplantation. When syngeneic neonatal porcine islets were transplanted intracutaneously, the islets remained differentiated as insulin-producing cells, maintained normal islet architecture, secreted c-peptide, and survived for over 100 days. Here, we show that BTM facilitates formation of an islet-supportive intracutaneous neodermis in a porcine preclinical model, as an alternative islet-transplant site. ARTICLE HIGHLIGHTS: Human and porcine pancreatic islets were transplanted into a fully vascularized biodegradable temporizing matrix (Novosorb) that creates a unique intracutaneous site outside of the liver in a large-animal preclinical model. The intracutaneous prevascularized site supported pancreatic islet survival for 3 months in a syngeneic porcine-transplant model. Pancreatic (human and porcine) islet survival and function were demonstrated in an intracutaneous site outside of the liver for the first time in a large-animal preclinical model.

Comparison of biopolymer scaffolds for the fabrication of skin substitutes in a porcine wound model.

This study compared three acellular scaffolds as templates for the fabrication of skin substitutes. A collagen-glycosaminoglycan (C-GAG), a biodegradable polyurethane foam (PUR) and a hybrid combination (PUR/C-GAG) were investigated. Scaffolds were prepared for cell inoculation. Fibroblasts and keratinocytes were serially inoculated onto the scaffolds and co-cultured for 14 days before transplantation. Three pigs each received four full-thickness 8 cm × 8 cm surgical wounds, into which a biodegradable temporising matrix (BTM) was implanted. Surface seals were removed after integration (28 days), and three laboratory-generated skin analogues and a control split-thickness skin graft (STSG) were applied for 16 weeks. Punch biopsies confirmed engraftment and re-epithelialisation. Biophysical wound parameters were also measured and analysed. All wounds showed greater than 80% epithelialisation by day 14 post-transplantation. The control STSG displayed 44% contraction over the 16 weeks, and the test scaffolds, C-GAG 64%, Hybrid 66.7% and PUR 67.8%. Immunohistochemistry confirmed positive epidermal keratins and basement membrane components (Integrin alpha-6, collagens IV and VII). Collagen deposition and fibre organisation indicated the degree of fibrosis and scar produced for each graft. All scaffold substitutes re-epithelialised by 4 weeks. The percentage of original wound area for the Hybrid and PUR was significantly different than the STSG and C-GAG, indicating the importance of scaffold retainment within the first 3 months post-transplant. The PUR/C-GAG scaffolds reduced the polymer pore size, assisting cell retention and reducing the contraction of in vitro collagen. Further investigation is required to ensure reproducibility and scale-up feasibility.

Advances in Skin Tissue Bioengineering and the Challenges of Clinical Translation.

Skin tissue bioengineering is an emerging field that brings together interdisciplinary teams to promote successful translation to clinical care. Extensive deep tissue injuries, such as large burns and other major skin loss conditions, are medical indications where bioengineered skin substitutes (that restore both dermal and epidermal tissues) are being studied as alternatives. These may not only reduce mortality but also lessen morbidity to improve quality of life and functional outcome compared with the current standards of care. A common objective of dermal-epidermal therapies is to reduce the time required to accomplish stable closure of wounds with minimal scar in patients with insufficient donor sites for autologous split-thickness skin grafts. However, no commercially-available product has yet fully satisfied this objective. Tissue engineered skin may include cells, biopolymer scaffolds and drugs, and requires regulatory review to demonstrate safety and efficacy. They must be scalable for manufacturing and distribution. The advancement of technology and the introduction of bioreactors and bio-printing for skin tissue engineering may facilitate clinical products' availability. This mini-review elucidates the reasons for the few available commercial skin substitutes. In addition, it provides insights into the challenges faced by surgeons and scientists to develop new therapies and deliver the results of translational research to improve patient care.

Biodegradable Temporizing Matrix Reconstruction of Complex Perineal Burn Wound: A Case Report.

This case report details our experience using a two-stage Biodegradable Temporizing Matrix (NovoSorb® PolyNovo Ltd) and autograft for acute reconstruction of a complex perineal burn wound in an elderly comorbid patient. A 77-year-old man sustained 42% full-thickness burns extending circumferentially from bilateral thighs and buttocks, across the entire perineal and genital regions up to his mid-trunk, following self-immolation using an accelerant. Early total burn wound excision was carried out with acute application of Biodegradable Temporizing Matrix to all affected sites. Excellent integration and vascularization of Biodegradable Temporizing Matrix took place despite the challenge of intermittent fecal contamination affecting the perineal and buttock burn sites and matrix colonization with multidrug-resistant organisms. Delamination and serial split-thickness skin autografting were carried out 42 days after the first matrix application with complete and robust graft take. Perineal burns present a reconstructive challenge due to the proximity of specialized structures such as the genitalia, urethral, and anal orifices. Restoration of complex anatomy and function may be required after debridement with increased risks of infection, contracture formation, and mortality compared with burns affecting other anatomical sites. Two-stage Biodegradable Temporizing Matrix represents a reliable reconstruction option for complex extensive perineal wounds in frail elderly patients, despite an unfavorable local microbial environment.

Scale-up of a Composite Cultured Skin Using a Novel Bioreactor Device in a Porcine Wound Model.

Extensive deep-burn management with a two-stage strategy can reduce reliance on skin autografts; a biodegradable polyurethane scaffold to actively temporize the wound and later an autologous composite cultured skin (CCS) for definitive closure. The materials fulfilling each stage have undergone in vitro and in vivo pretesting in "small" large animal wounds. For humans, producing multiple, large CCSs requires a specialized bioreactor. This article reports a system used to close large porcine wounds. Three Large White pigs were used, each with two wounds (24.5 cm × 12 cm) into which biodegradable dermal scaffolds were implanted. A sample from discarded tissue allowed isolation/culture of autologous fibroblasts and keratinocytes. CCS production began by presoaking a 1-mm-thick biodegradable polyurethane foam in autologous plasma. In the bioreactor cassette, fibroblasts were seeded into the matrix with thrombin until established, followed by keratinocytes. The CCSs were applied onto integrated dermal scaffolds on day 35, alongside a sheet skin graft (30% of one wound). Serial punch biopsies, trans-epidermal water loss readings (TEWL), and wound measurements indicated epithelialization. During dermal scaffold integration, negligible wound contraction was observed (average 4.5%). After CCS transplantation, the control skin grafts were "taken" by day 11 when visible islands of epithelium were clinically observed on 2/3 CCSs. Closure was confirmed histologically, with complete epithelialization by day 63 post-CCS transplantation (CCS TEWL ~ normal skin average 11.9 g/m2h). Four of six wounds demonstrated closure with robust, stratified epithelium. Generating large pieces of CCS capable of healing large wounds is thus possible using a specialized designed bioreactor.

Mortality data 2004-2019: an audit of the Royal Adelaide Hospital Adult Burn Service.

BACKGROUND: Burns are complex, multifaceted injuries that can pose significant challenges to the treating team. The Royal Adelaide Hospital (RAH) Burns Service has undergone a major evolution over the past two decades, with perceived improvement in outcomes. We present here a longitudinal audit of the RAH Burns Service Mortality Data between 2004 and 2019. METHODS: An audit was conducted of all index admissions to the RAH Burns Unit from 1 January 2004 to 31 December 2019. Age at admission, total body surface area, burn depth, presence of inhalation injury and outcome were recorded. Baux and revised Baux Scores were calculated. Lethal Area 50% for different time points and age groups, Baux50/100 and Revised Baux50/100 values were then calculated using logistical regression. RESULTS: During 2004-2019, there were 5653 index admissions to the RAH Burns Unit. The mean total body surface area of burn injuries admitted was 5.1% and the survival rate was 99.17%. The Lethal Area 50% for the study period was 74%, with an improvement from 70% (2004-2011) to 80% (2012-2019). The Baux50 score for the time period was 120 and the Revised Baux50 was 129. CONCLUSION: The RAH results are comparable with other high-income country Burn Services and demonstrated significant improvement across the study period. The data also highlight areas for ongoing focus such as the elderly burns patient.

A paradigm shift in practice-the benefits of early active wound temporisation rather than early skin grafting after burn eschar excision.

After major burn injury, once survival is achieved by the immediate excision of all deep burn eschar, we are faced with a patient who is often physiologically well but with very extensive wounds. While very early grafting yields excellent results after the excision of small burns, it is not possible to achieve the same results once the wound size exceeds the available donor site. In patients where 50%-100% of the total body surface area is wound, we rely on serial skin graft harvest, from finite donor site resources, and the massive expansion of those harvested grafts to effect healing. The result is frequently disabling and dysaesthetic. Temporisation of the wounds both passively, with cadaver allograft, and actively, with dermal scaffolds, has been successfully employed to ameliorate some of the problems caused by our inability to definitively close wounds early. Recent advances in technology have demonstrated that superior functional and cosmetic outcomes can be achieved in actively temporised areas even when compared with definitive early closure with skin graft. This has several beneficial implications for both patient and surgeon, affecting the timing of definitive wound closure and creating a paradigm shift in the care of the burned patient.

Advantages of immediate excision of burn eschar.

Early excision of deep burn eschar and the expeditious closure of the resultant wounds have become established as gold standard burn care. However, early burn excision has been accepted as up to four days post injury based on a series of misconceptions, not least that the patient is too unwell to undergo surgery and tolerate anaesthesia too soon after injury. There are several reasons why immediate burn excision yields superior survival outcomes, and these are expounded in this article. The systemic pathophysiology following major burn injury, especially when complicated by the respiratory pathophysiology accompanying smoke inhalation, evolves. The hours immediately after burn injury offer several windows of surgical opportunity, windows closed by the pathophysiological events that peak 24 hours later and make surgery and anaesthesia at that time both dangerous and ill-advised.

A Synthetic Biodegradable Temporising Matrix in Degloving Lower Extremity Trauma Reconstruction: A Case Report.

Presented is the case of an obese, 72 year-old diabetic man with a dorsal foot de-gloving injury. Whilst the tendons of extensor hallucis longus, extensor digitorum longus to all digits, and extensor digitorum brevis to hallux and second toe were intact after surgical debridement, none had any covering paratenon. The joint between the medial cuneiform and first metatarsal was open. Reconstructive options were limited by his age and co-morbidities. A novel, completely synthetic dermal matrix (NovoSorb BTM) was applied, after which the patient was discharged home to attend for dressings and review of integration progress as an outpatient. He was allowed to mobilise without limitation. Because of the poor quality of the wound bed (and patient), the material integrated slowly over 9 weeks. Delamination of the matrix, and definitive closure by application of sheet split skin autograft, produced a robust, soft, mobile and excellent aesthetic result, over which he could wear footwear immediately. Clinically, the paratenon-denuded tendons glided under the neo-dermis without tethering to the overlying integrated matrix, allowing a full range of digital movement. This was confirmed on ultrasound examination, which also demonstrated no inflammation or oedema. Already proven in extensive burns, necrotising fasciitis and complex surgical wounds, BTM represents a useful addition to the reconstructive surgeon's toolbox.

Reconstruction of an Anterior Cervical Necrotizing Fasciitis Defect Using a Biodegradable Polyurethane Dermal Substitute.

Introduction: Although we have previously described the use of a novel polyurethane biodegradable dermal substitute in the reconstruction of 20 free flap donor sites, and extensive cutaneous defects, including a large area of exposed calvarium secondary to burn injury, our experience with this material now extends to 35 free flap donor site reconstructions and 13 major or complex burns. Methods: The polyurethane material (NovoSorb BTM; PolyNovo Biomaterials Pty Ltd, Port Melbourne, Victoria, Australia) was recently employed in another complex wound scenario, implanted into a large anterior cervical cutaneous and soft-tissue defect remaining after serial radical debridement for necrotizing fasciitis. Results: Implantation, integration, delamination, and split-skin graft application proceeded without complication, mirroring our previous experience in other wounds (including major burns). The result was a robust, supple, mobile, and well-contoured reconstruction over the deep tissues of the neck. The functional and cosmetic outcomes exceeded all expectation. Discussion: The wound environment created after necrotizing fasciitis infection and debridement is austere. In this particular case, reconstructive options were limited to large free flap repair, skin graft alone, and skin graft augmented by commercially available collagen/glycosaminoglycan dermal matrix. Each option was discarded for various reasons. Our previous success with NovoSorb BTM, developed at our center, prompted its use following regulatory approval. The patient was physiologically stronger after the temporization afforded by the biodegradable temporizing matrix over 4 weeks of integration. Conclusion: This is the first description of the successful use of an entirely synthetic biodegradable dermal substitute for the reconstruction of both necrotizing fasciitis and an anterior cervical defect.

The Burns Registry of Australia and New Zealand: progressing the evidence base for burn care.

OBJECTIVE: Analysis of data from the Burns Registry of Australia and New Zealand (BRANZ) to determine the extent of variation between participating units in treatment and in specific outcomes during the first 4 years of its operation. DESIGN: BRANZ, an initiative of the Australian and New Zealand Burn Association, is a clinical quality registry developed in accordance with the Australian Commission on Safety and Quality in Healthcare national operating principles. SETTING: Patients with burn injury who fulfil pre-defined criteria are transferred to and managed in designated burn units. There are 17 adult and paediatric units in Australia and New Zealand that manage almost all patients with significant burn injury. Twelve of these units treat adult patients. PARTICIPANTS: Data on 7184 adult cases were contributed by ten acute adult burn units to the registry between July 2010 and June 2014.Major outcomes: In-hospital mortality, hospital length of stay, skin grafting rates, and rates of admission to intensive care units. RESULTS: Considerable variations in unit profiles (including numbers of patients treated), in treatment and in outcomes were identified. CONCLUSIONS: Despite the highly centralised delivery of care to patients with severe or complex burn injury, and the relatively small number of specialist burn units, we found significant variation between units in clinical management and in outcomes. BRANZ data from its first 4 years of operation support its feasibility and the value of further development of the registry. Based on these results, the focus of ongoing research is to improve understanding of the reasons for variations in practice and of their effect on outcomes for patients, and to develop evidence-informed clinical guidelines for burn management in Australia and New Zealand.

A Novel Biodegradable Polyurethane Matrix for Auricular Cartilage Repair: An In Vitro and In Vivo Study.

Auricular reconstruction poses a challenge for reconstructive and burns surgeons. Techniques involving cartilage tissue engineering have shown potential in recent years. A biodegradable polyurethane matrix developed for dermal reconstruction offers an alternative to autologous, allogeneic, or xenogeneic biologicals for cartilage reconstruction. This study assesses such a polyurethane matrix for this indication in vivo and in vitro. To evaluate intrinsic cartilage repair, three pigs underwent auricular surgery to create excisional cartilage ± perichondrial defects, measuring 2 × 3 cm in each ear, into which acellular polyurethane matrices were implanted. Biopsies were taken at day 28 for histological assessment. Porcine chondrocytes ± perichondrocytes were cultured and seeded in vitro onto 1 × 1 cm polyurethane scaffolds. The total culture period was 42 days; confocal, histological, and immunohistochemical analyses of scaffold cultures were performed on days 14, 28, and 42. In vivo, the polyurethane matrices integrated with granulation tissue filling all biopsy samples. Minimal neocartilage invasion was observed marginally on some samples. Tissue composition was identical between ears whether perichondrium was left intact, or not. In vitro, the polyurethane matrix was biocompatible with chondrocytes ± perichondrocytes and supported production of extracellular matrix and Type II collagen. No difference was observed between chondrocyte culture alone and chondrocyte/perichondrocyte scaffold coculture. The polyurethane matrix successfully integrated into the auricular defect and was a suitable scaffold in vitro for cartilage tissue engineering, demonstrating its potential application in auricular reconstruction.

Alkalis and Skin.

The aim of this editorial is to provide an overview of the chemical interactions occurring in the skin of our patients on contact with alkaline agents. Strongly basic alkali is highly aggressive and will readily hydrolyze (or cleave) key biological molecules such as lipids and proteins. This phenomenon is known as saponification in the case of lipids and liquefactive denaturation for peptides and proteins. A short section on current first-aid concepts is included. A better understanding of the basic science behind alkali burns will make us better teachers and provide an insight into the urgency needed in treating these common and dangerous chemical injuries.

The effectiveness of moisturizers in the management of burn scars following burn injury: a systematic review.

BACKGROUND: The common mantra with which patients often leave a burns unit is "moisturize and massage". Various products have been reported for use in practice including aqueous cream BP, bees wax and herbal oil creams, silicone based creams, paraffin/petroleum/mineral oil based products and aloe vera gels. Often combined with other scar management techniques such as pressure therapy, massage and contact media, moisturizers convey active properties of their own.  To date no published review on the optimal moisturizer for burn scar management has been identified via searches of recognized databases. OBJECTIVES: The objective of this review was to identify and synthesize the best available evidence on the effectiveness of moisturizer use in the management of active burn scars following burn injury.  More specifically, this review focused on the following questions:  Does moisturizer use have an effect on scar outcomes following burn injury, including scar formation, skin breakdown, patient acceptance and water loss?  What is the optimal base composition of moisturizers used in scar management for patients who have sustained a burn injury? INCLUSION CRITERIA: Types of participants:  Patients of any age who have sustained a burn injury of any size, and have been admitted to a hospital or regional burn unit or burn centre for the management of their injury.  Types of intervention(s)/phenomena of interest:  Studies evaluating moisturizer applied to healed skin following burn injury were considered for inclusion. Moisturizer may have been compared to usual care as defined by the individual study, other interventions, or a different type of moisturizer. Studies comparing moisturizer and massage compared to moisturizer alone were excluded.  Types of studies:  This review primarily considered experimental study designs, including randomized and pseudo-randomized controlled trials.  Types of outcomes:  Primary outcomes for examination in this review included scar formation and skin breakdown, measured by objective tools or subjective scales.  Secondary outcomes included product acceptance, patient compliance and transepidermal water loss. SEARCH STRATEGY: A search was conducted to identify published and unpublished studies via electronic databases. Reference lists of all papers selected for full text retrieval were then hand searched for potential additional citations. METHODOLOGICAL QUALITY: Articles meeting pre-determined eligibility criteria for the review were assessed by two independent reviewers using standardized checklists from the Joanna Briggs Institute Meta Analysis of Statistics Assessment and Review Instrument. Corresponding authors were contacted where additional information was required; however this strategy did not yield additional information that altered study eligibility status. DATA COLLECTION: Data was extracted from the included paper using the standardized data extraction tool from the Joanna Briggs Institute Meta Analysis of Statistics Assessment and Review Instrument. DATA SYNTHESIS: Narrative synthesis of the included study was undertaken. RESULTS: One study, following a randomized controlled design, was eligible for inclusion in this review. This study investigated the effect of vitamin E cream versus a base moisturizing cream on outcomes including range of motion, scar thickness, cosmetic appearance and graft size. No significant differences between groups for all reported outcomes were observed. CONCLUSIONS: Despite the common practice involving moisturizers TRUNCATED AT 500 WORDS.

Free Flap Donor Site Reconstruction: A Prospective Case Series Using an Optimized Polyurethane Biodegradable Temporizing Matrix.

INTRODUCTION: We recently published a 10-patient case series where free flap donor site reconstruction was performed as a 2-stage procedure using an integrating biodegradable polyurethane matrix (to form a neodermis), followed by definitive closure with an autologous split-skin graft. Two issues were revealed by this pilot study that led to further modification of the biodegradable temporizing matrix. This involved alterations to the seal thickness and bonding to the foam matrix and the introduction of fenestrations to the seal. OBJECTIVE: This article documents a second cohort of patients requiring free flap (fibular and radial forearm) donor site reconstruction with this optimized material. METHODS: The biodegradable temporizing matrix was implanted when the free flap was detached from its donor site. Subsequent integration was monitored closely. Five weeks was the usual time of integration before delamination (seal removal), dermabrasion, and definitive closure with autograft. RESULTS: Integration was complete and uncomplicated in every case, delamination occurred in 1 piece in 1 action, and subsequent graft take was 100% for every patient. Long-term scar outcomes improved compared with the pilot group. Degradation is complete by 12 months, other than occasional microscopic remnants undergoing phagocytosis. CONCLUSION: This study has reiterated that the biodegradable temporizing matrix can be implanted into humans, followed by neovascularization and integration. No infection was observed, and split-skin overgrafting was successful and uncomplicated.

A biodegradable polyurethane dermal matrix in reconstruction of free flap donor sites: a pilot study.

We have developed a biodegradable temporizing matrix (BTM) capable of supporting secondary split-skin graft-take in animal studies. We report its first long-term implantation and use as a dermal scaffold in humans. This preliminary study assesses its ability to integrate, its ease of delamination, its ability to sustain split-skin graft in complex wounds, the degree of wound contraction, and ultimately the quality of the scar at 1 year postimplantation. Ten patients were recruited, each requiring elective free flap reconstruction. Free flap donor sites created were anterolateral thigh flaps, fibular osseocutaneous flaps, or radial/ulnar forearm (RF/UF) flaps. The BTM was implanted when the flap was detached from its donor site. Dressing changes were performed twice weekly. The time elapsed between implantation and delamination depended on the type of flap and thus the wound bed left. Once integrated, the BTMs were delaminated in theatre, and the surface of the "neodermis" was refreshed by dermabrasion, prior to application of a split-skin graft. The BTM integration occurred in all patients (100% in 6 patients, with 90%, 84%, 76%, and 60% integration in the remainder). Integrated BTM sustained successful graft-take in all patients. Complete take was marred in 2 patients, over areas of BTM that had not integrated and graft application was performed too early. The BTM can be applied into wounds in humans and can integrate, persist in the presence of infection, and sustain split-skin overgrafting, despite the trial group presenting with significant comorbidities.

Peroxidase enzymes regulate collagen extracellular matrix biosynthesis.

Myeloperoxidase and eosinophil peroxidase are heme-containing enzymes often physically associated with fibrotic tissue and cancer in various organs, without any direct involvement in promoting fibroblast recruitment and extracellular matrix (ECM) biosynthesis at these sites. We report herein novel findings that show peroxidase enzymes possess a well-conserved profibrogenic capacity to stimulate the migration of fibroblastic cells and promote their ability to secrete collagenous proteins to generate a functional ECM both in vitro and in vivo. Mechanistic studies conducted using cultured fibroblasts show that these cells are capable of rapidly binding and internalizing both myeloperoxidase and eosinophil peroxidase. Peroxidase enzymes stimulate collagen biosynthesis at a post-translational level in a prolyl 4-hydroxylase-dependent manner that does not require ascorbic acid. This response was blocked by the irreversible myeloperoxidase inhibitor 4-amino-benzoic acid hydrazide, indicating peroxidase catalytic activity is essential for collagen biosynthesis. These results suggest that peroxidase enzymes, such as myeloperoxidase and eosinophil peroxidase, may play a fundamental role in regulating the recruitment of fibroblast and the biosynthesis of collagen ECM at sites of normal tissue repair and fibrosis, with enormous implications for many disease states where infiltrating inflammatory cells deposit peroxidases.

Optimization of a polyurethane dermal matrix and experience with a polymer-based cultured composite skin.

The aims were to (1) describe the in vivo studies leading to an optimized model of the biodegradable temporizing matrix (BTM), (2) describe our efforts in effecting closure over this optimized matrix after integration with a cultured composite skin (CCS), and (3) reexamine the ability of the CCS to definitively close fresh wounds (without BTM). Foam scaffolds of biodegradable polyurethane were created to allow in vivo tissue ingrowth or in vitro co-culture. Using the porcine surgical model, multiple BTM optimization studies took place before the BTM-CCS main study was conducted. For the CCS study, optimized sealed 2 mm matrices were implanted into 6-mm deep, 8 × 8 cm wounds (three per pig) and allowed to integrate for 21 days, whereas collected blood and harvested skin tissue were used to prepare autologous composite skins in similar (unsealed) 1 mm matrices. These were then applied at day 21 either over the integrated BTMs or into a freshly created fourth wound. All of the optimized matrices integrated fully, without loss, and were found to resist wound contraction effectively until the composites were ready for application at day 21. The composites demonstrated the ability to generate a bilayer repair with robust epidermis anchored by a basement membrane visible from day 7 after application. The final optimized sealed BTM delaminates easily to produce a clean, temporized wound bed and will be used in the upcoming burn clinical trial. Although the CCS is a magnitude away from human trials, it is still capable of generating a bilayer repair in both BTM-integrated and fresh wounds (onto fat), and with further refinement and optimization of foam structure, seeding densities, and timing, consistent success should be possible.

A novel murine model of hypertrophic scarring using subcutaneous infusion of bleomycin.

BACKGROUND: The development of new therapies for hypertrophic scarring has been hampered by the lack of an appropriate animal model. The authors' objective was to establish a reproducible murine model of hypertrophic scarring by infusing bleomycin over a prolonged period to stimulate dermal fibroproliferation. METHODS: Osmotic pumps filled with 90 µl of 2.8 mg/ml bleomycin or a control solution (phosphate-buffered saline) were inserted subcutaneously under the dorsal skin of BALB/c mice. The pumps delivered their content at a constant rate of 0.11 µl/hour for 28 days before mice were euthanized or kept alive for a further 28 days and euthanized at day 56. The resulting lesions were analyzed using histological and immunohistochemical techniques. RESULTS: The lesions displayed histopathological features of hypertrophic scar similar to those observed in humans and had increased cellularity, abnormal collagen I-collagen III ratios, elevated levels of the proscarring cytokine transforming growth factor ß1, and increased numbers of myofibroblasts. The 28-day model displayed features analogous to those of a developing human hypertrophic scar, while the 56-day model was analogous to a mature hypertrophic scar. CONCLUSIONS: The bleomycin infusion model stimulates dermal fibroproliferation, creating reproducible murine scars that are comparable to human hypertrophic scars in terms of histological features, collagen content and organization, cellularity, the presence of myofibroblasts, and expression of transforming growth factor ß1. The bleomycin model represents a promising technique for studying scar formation and testing new antiscarring therapies.

"Take" of a polymer-based autologous cultured composite "skin" on an integrated temporizing dermal matrix: proof of concept.

This study aimed to investigate the ability of an autologous cultured composite skin (CCS) to close similar biodegradable temporizing matrix (BTM)-integrated wounds, and its effectiveness in healing fresh full-thickness wounds after the failure of cultured epithelial autograft in its two forms (sheets and suspensions) to epithelialize over an integrated polymer BTM. Using a porcine model, autologous split-skin grafts were harvested three of four dorsal 8 × 8 cm treatment sites. These three sites were subsequently converted to full-thickness wounds and BTMs were implanted. The grafts were used to produce autologous CCSs for each pig. These consisted of a 1 mm thick biodegradable polymer foam scaffold into which fibroblasts and keratinocytes harvested from the grafts were cocultured. At Day 28, on each animal, the autologous CCSs were applied to two of the integrated BTMs, an autologous split-skin graft was applied to the third integrated BTM, and one CCS was applied immediately into a fresh, "naked" (no BTM applied) wound. The CCSs were capable of generating a bilayer repair over the naked wound's fat base and BTM-integrated wounds, which consisted of dermal elements and a keratinized stratified squamous epidermis anchored with a basement membrane by day 7. The CCSs behaved in different ways: either as a delivery vehicle allowing similar development of a bilayer repair while the polymer foam was shed from the wound, or generating a bilayer repair with the foam scaffold being retained (composite "take"). These results conclude our porcine program and provide proof of concept that the integrated BTM can be closed with an autologous CCS. Once fully optimized, this may provide robust repair without resorting to the split-skin graft, important in those cases where unburned donor site is unavailable.