Use of a collagen-elastin matrix with split-thickness skin graft for defect coverage in complex wounds.

OBJECTIVE: Severe soft tissue damage with destruction of the dermis requires plastic reconstructive treatment. For multimorbid patients or patients unable to undergo major reconstructive surgery, use of dermal substitutes, such as a collagen-elastin matrix (CEM) with a split-thickness skin graft (STSG), instead of local or free flap surgery, may be a valid and easy treatment option. We aimed to investigate and compare the outcomes and rate of successful defect reconstruction using CEM plus STSG, using either a one-step approach (simultaneous CEM and STSG) or a two-step approach (CEM and negative wound pressure therapy (NPWT), with secondary STSG transplantation). METHOD: A single-centre, retrospective follow-up study of patients who had received CEM was conducted. Wounds had been treated with an STSG transplantation covering a CEM (MatriDerm, MedSkin Solutions Dr. Suwelack AG, Germany). Previous attempts at wound closure with conventional methods had failed in the selected patient population, which would usually have resulted in flap surgery. RESULTS: Overall, 46 patients were included (mean age 60.9±20.0 years), with a total of 49 wound sites. We analysed 38 patients with wounds that did not require flap coverage; 18 patients received the one-step approach and 20 patients received the two-step approach. The mean follow-up in these patients was 22±11.5 months, and one patient was lost to follow-up. Overall, 29 (78.4%) wounds remained closed. Wounds which did not successfully heal were related to comorbidities, such as diabetes, alcohol misuse and smoking. Using the one-step approach, long-term defect coverage was achieved in 13 (76.5%) wounds and 16 (80.0%) wounds were closed using the two-step approach. However, there was no statistically significant differences between the one- or two-step approaches regarding the rate of development of a wound healing disorder. CONCLUSION: Wound closure was achieved in 38 complex wounds using CEM plus STSG, while 11 wounds needed secondary flap coverage. In the flap-free wounds, there were no statistically significant differences between the one-step versus two-step approach. Using a simple defect reconstruction algorithm, we successfully used CEM plus STSG to treat complex wounds.

Engineered elastin-like polypeptide-based hydrogel delivering chemotherapeutics and PD-L1 antibodies for potentiated cancer immunotherapy.

Immune checkpoint inhibitors (ICIs) have effectively eradicated advanced tumors by inducing durable and systematic antitumor immune responses. However, when used as a standalone treatment, ICIs typically exhibit a low response rate in many cancers. In this study, we engineered an in situ-formed gel depot using elastin-like polypeptides (ELPs) to efficiently deliver PD-L1 antibodies (aPD-L1) and gemcitabine (GEM) for enhanced immunotherapy in melanoma. Sustainably released chemotherapeutics from gel depots could kill melanoma cells and promote PD-L1 upregulation in tumor cells. Moreover, aPD-L1/GEM-encapsulated ELP hydrogel promoted a 3.0-fold increase of tumor-infiltrated CD8+ T cells and 60% Tregs depletion compared with PBS group, eliciting a robust antitumor immune response for immunotherapy in melanoma mouse models. This research highlights the promising potential of ELP-based hydrogels in delivering ICIs and chemotherapeutic agents for potentiated cancer immunotherapy.

A Histological and Clinical Study of MatriDerm® Use in Burn Reconstruction.

Dermal substitutes are well established in the reconstructive ladder. MatriDerm® (Dr. Otto Suwelack Skin & Health Care AG, Billerbeck, Germany) is a single-layer dermal substitute composed of a bovine collagen (type I, III, and V) and elastin hydrolysate, that allows for immediate split-thickness skin grafting (SSG). The aim of this study was to histologically characterize the integration of MatriDerm® when used during burns surgery reconstruction. Eight subjects with nine burn scars and one acute burn wound underwent reconstruction with MatriDerm® and an immediate SSG. MatriDerm® integration and skin graft take were assessed with serial biopsies performed at weeks 1, 2, 3, and 4 and months 2, 3, 6, 9, and 12. Biopsies were assessed with standard special stains and immunohistochemistry, and representative slides were imaged with a transmission electron microscope. Patient satisfaction and clinical scar outcome were assessed with the Vancouver Scar Scale and a patient questionnaire. Histological analysis showed similar stages of wound healing as shown in other dermal templates but on a different timescale. There is early evidence of vascularization and an inflammatory infiltrate in the first 2 weeks. MatriDerm® is resorbed earlier than other dermal substitutes, with evidence of resorption at week 3, to be completely replaced by a neodermis at 2 months. The use of MatriDerm® in reconstruction with immediate skin grafting is supported histologically with early evidence of vascularization to support an epidermal autograft. Future histological studies may help further characterize the ideal dermal substitute.

Regression of calcinosis cutis after inkless tattoo in a patient with dermatomyositis: therapeutic potential of microneedling.

Calcinosis cutis is defined as abnormal deposition of calcium salts in the skin and subcutaneous tissues. Dystrophic calcification, the most common form of calcinosis cutis, is associated with autoimmune connective tissue diseases. This condition is associated with severe pain and can affect the patient's quality of life and lead to long-term disability. Treatment is often challenging, and there is a very limited evidence base for potential treatments of calcinosis cutis associated with systemic sclerosis and dermatomyositis. Inkless tattoo is very similar to microneedling, a minimally invasive procedure stimulating the wound-healing cascade contributing to elastin and collagen formation as well as neovascularization. This technique has not been reported as a potential therapeutic option for calcinosis cutis. Here, we present a patient with calcinosis cutis in the setting of dermatomyositis that responded dramatically to inkless tattoo application. Our results support the need for future studies of microneedling in patients with this disorder.

Machine learning to determine optimal conditions for controlling the size of elastin-based particles.

This paper evaluates the aggregation behavior of a potential drug and gene delivery system that combines branched polyethyleneimine (PEI), a positively-charged polyelectrolyte, and elastin-like polypeptide (ELP), a recombinant polymer that exhibits lower critical solution temperature (LCST). The LCST behavior of ELP has been extensively studied, but there are no quantitative ways to control the size of aggregates formed after the phase transition. The aggregate size cannot be maintained when the temperature is lowered below the LCST, unless the system exhibits hysteresis and forms irreversible aggregates. This study shows that conjugation of ELP with PEI preserves the aggregation behavior that occurs above the LCST and achieves precise aggregate radii when the solution conditions of pH (3, 7, 10), polymer concentration (0.1, 0.15, 0.3 mg/mL), and salt concentration (none, 0.2, 1 M) are carefully controlled. K-means cluster analyses showed that salt concentration was the most critical factor controlling the hydrodynamic radius and LCST. Conjugating ELP to PEI allowed crosslinking the aggregates and achieved stable particles that maintained their size below LCST, even after removal of the harsh (high salt or pH) conditions used to create them. Taken together, the ability to control aggregate sizes and use of crosslinking to maintain stability holds excellent potential for use in biological delivery systems.

Acellular dermal matrix reconstruction of a nail bed avulsion in a 13-year-old child.

Nail bed avulsion injuries often require reconstruction, particularly in cases where the avulsed fragment is lost. We describe a simple way to reconstruct a large nail bed defect, with no donor site. A 13-year-old boy with a hypoplastic left heart and autism accidentally sustained a left little distal phalanx injury with an avulsion of 60% of the nail bed, exposing the distal phalanx. This boy had a history of poor compliance, qualifying the need to find a technique that would minimise operative time and dressing changes. As such, it was elected to use an acellular dermal matrix (ADM) (Matriderm) as a one-step reconstruction. Signs of vascularisation of the ADM were noted at 2 weeks, and 3-month follow-up demonstrated integration, with normal nail growth. We found that Matriderm was able to support the regeneration of a full thickness wound in a simple one-step procedure.

Improving the regenerative microenvironment during tendon healing by using nanostructured fibrin/agarose-based hydrogels in a rat Achilles tendon injury model.

AIMS: Achilles tendon injuries are a frequent problem in orthopaedic surgery due to their limited healing capacity and the controversy surrounding surgical treatment. In recent years, tissue engineering research has focused on the development of biomaterials to improve this healing process. The aim of this study was to analyze the effect of tendon augmentation with a nanostructured fibrin-agarose hydrogel (NFAH) or genipin cross-linked nanostructured fibrin-agarose hydrogel (GP-NFAH), on the healing process of the Achilles tendon in rats. METHODS: NFAH, GP-NFAH, and MatriDerm (control) scaffolds were generated (five in each group). A biomechanical and cell-biomaterial-interaction characterization of these biomaterials was then performed: Live/Dead Cell Viability Assay, water-soluble tetrazolium salt-1 (WST-1) assay, and DNA-released after 48 hours. Additionally, a complete section of the left Achilles tendon was made in 24 Wistar rats. Animals were separated into four treatment groups (six in each group): direct repair (Control), tendon repair with MatriDerm, or NFAH, or GP-NFAH. Animals were euthanized for further histological analyses after four or eight weeks post-surgery. The Achilles tendons were harvested and a histopathological analysis was performed. RESULTS: Tensile test revealed that NFAH and GP-NFAH had significantly higher overall biomechanical properties compared with MatriDerm. Moreover, biological studies confirmed a high cell viability in all biomaterials, especially in NFAH. In addition, in vivo evaluation of repaired tendons using biomaterials (NFAH, GP-NFAH, and MatriDerm) resulted in better organization of the collagen fibres and cell alignment without clinical complications than direct repair, with a better histological score in GP-NFAH. CONCLUSION: In this animal model we demonstrated that NFAH and GP-NFAH had the potential to improve tendon healing following a surgical repair. However, future studies are needed to determine the clinical usefulness of these engineered strategies. Cite this article: Bone Joint J 2020;102-B(8):1095-1106.

Aplasia cutis congenita of both knees: A new therapeutic strategy.

Aplasia cutis congenita is defined as the absence of all layers of the skin. The condition involves mainly the scalp but it can affect any area of skin on the body. A clear therapeutic strategy is not available. Here, we describe the 6-year clinical outcome of a patient with aplasia cutis congenita of both knees following treatment with an artificial dermis and a thin skin graft.

Nanotoxicology of an Elastin-like Polypeptide Rapamycin Formulation for Breast Cancer.

The clinical utility of rapamycin (Rapa) is limited by solubility, bioavailability, and side effects. To overcome this, our team recently reported an elastin-like polypeptide (ELP) nanoparticle with high affinity, noncovalent drug binding, and integrin-mediated cellular uptake. Given the scarcity of pharmacology/toxicology studies of ELP-based drug carriers, this article explores safety and efficacy of ELP-Rapa. ELP-Rapa nanoparticles tested negative for hemolysis, did not interfere in plasma coagulation nor in platelet function, and did not activate the complement. Upon incubation with HepG2 cells, ELP-Rapa revealed significant cellular uptake and trafficking to acidic organelles, consistent with lysosomes. Internalized ELP-Rapa nanoparticles increased oxidative stress 4-fold compared to free drug or free ELP controls. However, mice bearing orthotopic hormone receptor positive BT-474 breast tumors, given a high dose (∼10-fold above therapeutic dose) of 1 month administration of ELP-Rapa, did not induce hepatotoxicity. On the other hand, tumor growth and mTOR signaling were suppressed without affecting body weight. Nanoparticles assembled using ELP technology appear to be a safe and efficient strategy for delivering Rapa.

DERMAL REPLACEMENT WITH MATRIDERM - FIRST EXPERIENCE AT THE PRAGUE BURN CENTRE.

INTRODUCTION: The quality of resulting scar tissue plays an important role in patients return to normal life and full functioning in society. The use of artificial skin substitutes in clinical practice improves functional and cosmetic outcomes. This is true for any patient, and not only those suffering from burns. MATERIAL AND METHODS: The collagen elastin dermal substitute Matriderm® allows for immediate application of a dermal substitute together with a skin graft. The authors present a group of 10 patients representing their first experience in utilizing Matriderm® as a dermal substitute in the treatment of skin losses due to various etiologies. RESULTS: The average healing time in the group was 19.6 days. Healing took place without serious infectious complications and with good functional results. CONCLUSION: Matriderm® can be utilized as an alternative to the most commonly used dermal substitute so far, Integra®, in the treatment of acute skin loss due to various etiologies and in reconstructive surgery.

Elastin Biomaterials in Dermal Repair.

Wound healing has historically relied on endogenous processes, but engineered materials are increasingly being used to assist tissue repair. Elastin is an essential functional component of the dermal extracellular matrix and is an important part of skin wound repair that encompasses an elastic dermis. Advances in modern technology have better elucidated the specific signaling factors and cells that contribute to the physiological process and have led to new developments in wound care technology. We review elastin-based materials that are used to encourage wound repair. Elastin-related biomaterials, particularly those based on tropoelastin, are particularly promising because tropoelastin is assembled to make elastin. We present insights into the roles of elastin-related biomaterials and their associated in vitro and in vivo benefits on wound healing.

Comparative long-term study between two dermal regeneration templates for the reconstruction of burn scar contractures in humans: Clinical and histological results.

The advent of dermal regeneration templates has fostered major advances in the treatment of acute burns and their sequelae, in the last three decades. Both data on morphological aspects of the newly-formed tissue, and clinical trials comparing different templates, are few. The goal of this study was to prospectively analyze the outcome of randomized patients treated with two of the existing templates, followed by thin skin autograft. They are both 2 mm-thick bovine collagen templates (Matriderm® and Integra®), the latter includes a superficial silicone layer. Surgery was performed on patients with impaired mobility resulting from burn sequelae (n = 12 per template) in a two-step procedure. Negative pressure therapy was applied after surgery; patients were monitored for 12 months. No intra or postoperative complications were observed. Data on scar skin quality (Vancouver scar scale), rate of mobility recovery, and graft contraction were recorded; as well as morphological analyses at light microscopical level. Improvement in mobility and skin quality were demonstrated along with graft contraction, in all patients. The double layer template showed the best performance in retraction rate, skin quality and mobility recovery. The subepidermal newly-formed connective tissue showed no histoarchitectural differences between the templates. The double layer template was not absorbed up to 12 months after placement.

Reconstruction of Nasal Defects With Dermal Skin Substitutes-A Retrospective Study of 36 Defects.

OBJECTIVES: It is uncertain whether dermal regeneration templates (DRTs) are helpful to reconstruct nasal defects. The aim of this study was to assess whether the aesthetic subunits determine the outcome. METHODS: In this unicentric, retrospective study, the surgical procedures and outcomes of patients who received DRTs to reconstruct nasal defects were assessed and compared with the involved aesthetic subunits. RESULTS: DRTs were used for reconstruction of 36 nasal defects in 35 patients with involvement of 76 aesthetic subunits: nasal sidewall (n = 21), nasal ala (n = 13), nasal tip/columella (n = 12, n = 1, respectively), nasal dorsum (n = 12), and extranasal aesthetic areas (n = 17). Fifty-eight nasal and 8 extranasal aesthetic subunits were reconstructed with DRTs, 10 subunits with a flap. Twenty-nine of 36 defects healed without any complications (80.5%). All reconstructed nasal tips/columella and the nasal dorsa healed without any complications. Region-specific complications were retraction of the ala rim (4/12; 33.3% of the patients with involvement of the nasal ala) and the formation of a fistula in the nasal sidewall (1/21; 4.8%). Region-specific complications of extranasal subunits were the development of an ectropium (2/3; 66.7% of the patients with involvement of the lower lid). CONCLUSIONS: DRTs can be helpful to reconstruct nasal defects. However, if the defect involves the aesthetic subunits nasal ala or the infraorbital region, different techniques should be preferred.

Inhibition of Bromelain Activity During Enzymatic Debridement of Burn Wounds Pretreated With Frequently Used Products.

An enzyme mixture containing bromelain (NexoBrid®) was found to be suitable for enzymatic debridement of burn wounds, as determined by the criteria of patient comfort and pain, selectivity, and efficiency. Nevertheless, daily experience showed that pretreatment of burn wounds with several other clinical agents may inhibit debridement efficiency. Therefore, the current study was performed to identify those agents and evaluate their debridement inhibition capabilities. The impact of several common agents as well pH, on NexoBrid® debridement efficiency was evaluated in vitro. A collagen-based dermal substitute (MatriDerm®) was exposed to NexoBrid® in the presence of different agents of varying concentrations. Digestion was documented. The criteria used for judging digestion were independently classified by 3 investigators at least 3 times in succession. When a low concentration (1.0 mg/ml) of NexoBrid® was used, a ≥ 50% concentration of Prontosan® had an impact on enzymatic activity. Comparable results were obtained when even lower concentrations of Octenisept® (≥ 10%) were used. A 100-µmol/L concentration of copper inhibited the enzymatic activity of both a low (1.0 mg/ml) and high (10 mg/ml) concentration of NexoBrid®. Silver-sulfadiazine at concentrations of 10% and 90% inhibited the activity of 1 mg/ml NexoBrid®. No complete inhibition of NexoBrid® activity occurred at any concentration of iron. We recommend using polyhexanide-containing agents (Prontosan®) to rinse and presoak burn wounds. Pretreatment of burn wounds with agents containing silver and copper should be avoided. Experimentally, we found a partial inhibition of NexoBrid® activity at the distinct pH values of 3 and 11.

Semi-IPN- and IPN-Based Hydrogels.

Semi-interpenetrating polymer networks (semi-IPNs) and interpenetrating polymeric networks (IPNs) have emerged as innovative materials for biomedical and pharmaceutical applications. The interest in these structures is due to the possibility of combining the favorable properties of each polymeric component of the IPNs or semi-IPNs leading to a new system with properties that often differ from those of the two single components. In this respect, polysaccharides represent an opportunity in this field, combining a general biocompatibility and a good availability. Moreover, the functional groups along the polymer chains allow chemical derivatization, widening the possibilities in semi-IPNs and IPNs building up. At the same time, materials based on proteins are often used in this field, due to their similarity to the materials present in the human body. All these overall properties allow tailoring new materials, thus designing desired properties and preparing new hydrogels useful in the biomedical field. In the present chapter, we chose to describe systems prepared starting from the most important and studied hydrogel-forming polysaccharides: alginate, hyaluronic acid, chitosan, dextran, gellan, and scleroglucan. Besides, systems based on proteins, such as gelatin, collagen, and elastin, are also described. With this chapter, we aim describing the routes already traveled in this field, depicting the state of the art and hoping to raise interest in designing new promising strategies useful in biomedical and pharmaceutical applications.

Improvement of physical properties of calcium phosphate cement by elastin-like polypeptide supplementation.

Calcium phosphate cements (CPCs) are synthetic bioactive cements widely used as hard tissue substitutes. Critical limitations of use include their poor mechanical properties and poor anti-washout behaviour. To address those limitations, we combined CPC with genetically engineered elastin-like polypeptides (ELPs). We investigated the effect of the ELPs on the physical properties and biocompatibility of CPC by testing ELP/CPC composites with various liquid/powder ratios. Our results show that the addition of ELPs improved the mechanical properties of the CPC, including the microhardness, compressive strength, and washout resistance. The biocompatibility of ELP/CPC composites was also comparable to that of the CPC alone. However, supplementing CPC with ELPs functionalized with octaglutamate as a hydroxyapatite binding peptide increased the setting time of the cement. With further design and modification of our biomolecules and composites, our research will lead to products with diverse applications in biology and medicine.

Self-Assembly of Thermoresponsive Recombinant Silk-Elastinlike Nanogels.

Recombinant silk-elastinlike protein polymers (SELPs) combine the biocompatibility and thermoresponsiveness of human tropoelastin with the strength of silk. Direct control over structure of these monodisperse polymers allows for precise correlation of structure with function. This work describes the fabrication of the first SELP nanogels and evaluation of their physicochemical properties and thermoresponsiveness. Self-assembly of dilute concentrations of SELPs results in nanogels with enhanced stability over micelles due to physically crosslinked beta-sheet silk segments. The nanogels respond to thermal stimuli via size changes and aggregation. Modifying the ratio and sequence of silk to elastin in the polymer backbone results in alterations in critical gel formation concentration, stability, aggregation, size contraction temperature, and thermal reversibility. The nanogels sequester hydrophobic compounds and show promise in delivery of bioactive agents.

Development of Tissue-Engineered Ligaments: Elastin Promotes Regeneration of the Rabbit Medial Collateral Ligament.

When ligaments are injured, reconstructive surgery is sometimes required to restore function. Methods of reconstructive surgery include transplantation of an artificial ligament and autotransplantation of a tendon. However, these methods have limitations related to the strength of the bone-ligament insertion and biocompatibility of the transplanted tissue after surgery. Therefore, it is necessary to develop new reconstruction methods and pursue the development of artificial ligaments. Elastin is a major component of elastic fibers and ligaments. However, the role of elastin in ligament regeneration has not been described. Here, we developed a rabbit model of a medial collateral ligament (MCL) rupture and treated animal knees with exogenous elastin [100 µg/(0.5 mL·week)] for 6 or 12 weeks. Elastin treatment increased gene expression and protein content of collagen and elastin (gene expression, 6-fold and 42-fold, respectively; protein content, 1.6-fold and 1.9-fold, respectively), and also increased the elastic modulus of MCL increased with elastin treatment (2-fold) compared with the controls. Our data suggest that elastin is involved in the regeneration of damaged ligaments.

Matriderm for Management of Scalp Necrosis Following Surgical Treatment of Giant Parietal Encephalocele.

BACKGROUND: Management of encephaloceles is challenging when massive brain herniation is present. In such instances, an expansile cranioplasty may be attempted so as to preserve some herniated brain tissue. Complications such as wound dehiscence, cerebrospinal fluid leak, and scalp necrosis are postoperative concerns. The treatment of scalp necrosis with dural and brain exposure is certainly a challenge due to the complexity of flap techniques in such a young age. Herein we describe the use of a novel technique for the management of a scalp necrosis and dehiscence in an infant. CASE DESCRIPTION: A patient with a giant parietal encephalocele and massive brain herniation underwent an expansile cranioplasty. A large scalp necrosis ensued as a complication and later progressed to a suture dehiscence despite a new surgical intervention, with resultant brain exposure. A scalp reconstruction was subsequently performed using an artificial dermal substitute, laid directly onto the brain, followed by a split-thickness skin graft. We observed a rapid engraftment, without any further complications, with an acceptable cosmetic result in the long-term follow-up. CONCLUSION: A simple technique, such as the use of an artificial dermal matrix with simultaneous split-thickness skin graft, may be an effective treatment for the repair of scalp defects, even when coverage of exposed brain tissue is necessary, when no other techniques are found to be suitable.

The development of a novel wound healing material, silk-elastin sponge.

Silk-elastin is a recombinant protein polymer with repeating units of silk and elastin blocks. This novel wound healing promoting material has the ability to self-assemble from a liquid to a gel. We have already reported that an aqueous solution of silk-elastin has the potential to accelerate wound healing; however, there are several problems in applying silk-elastin in the clinical setting. To solve these problems, we developed a silk-elastin sponge that is easy to use in the clinical setting. In the present study, we examined whether the wound healing effect of the silk-elastin sponge is equal to the aqueous solution of silk-elastin in vivo. The granulation tissue formation promoting effect of the silk-elastin sponge was equal to that of the aqueous solution the silk-elastin, as after application to the wound surface, the sponge was absorbed and dissolved by the exudate. At body temperature the silk-elastin then formed temperature gel. The silk-elastin gel that was obtained contained abundant cytokines from the exudate. We believe that silk-elastin sponge can be applied to various wounds that are difficult to treat with the aqueous solution.