Active wound coverings: bioengineered skin and dermal substitutes

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.

Acellular Dermal Matrix for Treatment of Diabetic Foot Ulcer: An Overview of Systematic Reviews

Aims: To evaluate the reliability of the methodological quality and outcome measures of systematic reviews (SRs)/metaanalyses (MAs) of the acellular dermal matrix (ADM) for diabetic foot ulcer (DFU). Methods: We searched and retrieved SRs and MAs on the application of ADM for DFU from PubMed, Web of Science, The Cochrane Library, EMBASE, CNKI, CBM, WanFang, and VIP databases. We employed AMSTAR 2 to assess methodological quality, Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system to grade, and the strength of evidence of included SRs/MAs. We excluded the overlapping randomized controlled trials (RCTs) and conducted a re-MA of the primary RCTs. Results: A total of 7 SRs/MAs were included. Results from the AMSTAR 2 evaluation revealed a low overall quality; the GRADE system showed that the evidence was of moderate to very low quality. Our re-MA showed that ADM was superior to standard of care (SOC), with regards to complete wound healing rate at 12 weeks (RR = 1.74, 95% CI:1.34-2.25, P < .0001), complete wound healing rate at 16 weeks (RR = 1.50, 95% CI: 1.26-1.77, P ＜ .00001); healing time (MD = -2.06, 95% CI: -2.57 to -1.54, P < .00001) and adverse events (RR = 0.62, 95% CI: 0.49-0.80, P = .0002). However, a consensus has not yet been reached between ADM and SOC groups with regard to outcome indicators of the reduction of ulcer area and quality of life; and subgroup analyses showed no statistically significant differences between the xenograft ADM and SOC groups (RR = 1.36, 95% CI: 0.95-1.93, P = .09) at 12 weeks. Conclusion: Current evidence suggests that ADM is more effective than the standard of care in the treatment of DFU, particularly for full-thickness, noninfected, and nonischemic foot ulcers, but with low evidence quality. Therefore, the results of this overview should be interpreted dialectically and prudently, and the role of ADM in DFU needs further exploration.

Polymeric biomaterials for wound healing

Skin indicates a person's state of health and is so important that it influences a person's emotional and psychological behavior. In this context, the effective treatment of wounds is a major concern, since several conventional wound healing materials have not been able to provide adequate healing, often leading to scar formation. Hence, the development of innovative biomaterials for wound healing is essential. Natural and synthetic polymers are used extensively for wound dressings and scaffold production. Both natural and synthetic polymers have beneficial properties and limitations, so they are often used in combination to overcome overcome their individual limitations. The use of different polymers in the production of biomaterials has proven to be a promising alternative for the treatment of wounds, as their capacity to accelerate the healing process has been demonstrated in many studies. Thus, this work focuses on describing several currently commercially available solutions used for the management of skin wounds, such as polymeric biomaterials for skin substitutes. New directions, strategies, and innovative technologies for the design of polymeric biomaterials are also addressed, providing solutions for deep burns, personalized care and faster healing.

In vivo efficacy proof of concept of a large-size bioprinted dermo-epidermal substitute for permanent wound coverage

Introduction: An autologous split-thickness skin graft (STSG) is a standard treatment for coverage of full-thickness skin defects. However, this technique has two major drawbacks: the use of general anesthesia for skin harvesting and scar sequelae on the donor site. In order to reduce morbidity associated with STSG harvesting, researchers have developed autologous dermo-epidermal substitutes (DESs) using cell culture, tissue engineering, and, more recently, bioprinting approaches. This study assessed the manufacturing reliability and in vivo efficacy of a large-size good manufacturing practice (GMP)-compatible bio-printed human DES, named Poieskin®, for acute wound healing treatment. Methods: Two batches (40 cm2 each) of Poieskin® were produced, and their reliability and homogeneity were assessed using histological scoring. Immunosuppressed mice received either samples of Poieskin® (n = 8) or human STSG (n = 8) immediately after longitudinal acute full-thickness excision of size 1 × 1.5 cm, applied on the skeletal muscle plane. The engraftment rate was assessed through standardized photographs on day 16 of the follow-up. Moreover, wound contraction, superficial vascularization, and local inflammation were evaluated via standardized photographs, laser Doppler imaging, and PET imaging, respectively. Histological analysis was finally performed after euthanasia. Results: Histological scoring reached 75% ± 8% and 73% ± 12%, respectively, displaying a robust and homogeneous construct. Engraftment was comparable for both groups: 91.8% (SD = 0.1152) for the Poieskin® group versus 100% (SD = 0) for the human STSG group. We did not record differences in either graft perfusion, PET imaging, or histological scoring on day 16. Conclusion: Poieskin® presents consistent bioengineering manufacturing characteristics to treat full-thickness cutaneous defects as an alternative to STSG in clinical applications. Manufacturing of Poieskin® is reliable and homogeneous, leading to a clinically satisfying rate of graft take compared to the reference human STSG in a mouse model. These results encourage the use of Poieskin® in phase I clinical trials as its manufacturing procedure is compatible with pharmaceutical guidelines.

Functionalised-biomatrix for wound healing and cutaneous regeneration: future impactful medical products in clinical translation and precision medicine

Skin tissue engineering possesses great promise in providing successful wound injury and tissue loss treatments that current methods cannot treat or achieve a satisfactory clinical outcome. A major field direction is exploring bioscaffolds with multifunctional properties to enhance biological performance and expedite complex skin tissue regeneration. Multifunctional bioscaffolds are three-dimensional (3D) constructs manufactured from natural and synthetic biomaterials using cutting-edge tissue fabrication techniques incorporated with cells, growth factors, secretomes, antibacterial compounds, and bioactive molecules. It offers a physical, chemical, and biological environment with a biomimetic framework to direct cells toward higher-order tissue regeneration during wound healing. Multifunctional bioscaffolds are a promising possibility for skin regeneration because of the variety of structures they provide and the capacity to customise the chemistry of their surfaces, which allows for the regulated distribution of bioactive chemicals or cells. Meanwhile, the current gap is through advanced fabrication techniques such as computational designing, electrospinning, and 3D bioprinting to fabricate multifunctional scaffolds with long-term safety. This review stipulates the wound healing processes used by commercially available engineered skin replacements (ESS), highlighting the demand for a multifunctional, and next-generation ESS replacement as the goals and significance study in tissue engineering and regenerative medicine (TERM). This work also scrutinise the use of multifunctional bioscaffolds in wound healing applications, demonstrating successful biological performance in the in vitro and in vivo animal models. Further, we also provided a comprehensive review in requiring new viewpoints and technological innovations for the clinical application of multifunctional bioscaffolds for wound healing that have been found in the literature in the last 5 years.

Preparation of laser microporous porcine acellular dermal matrix and observation of wound transplantation

To prepare a new type of porcine acellular dermis matrix (PADM) with the new laser microporous technique and verify its safety and feasibility. A novel porcine acellular dermis matrix (ADM) was prepared by using sequential combined decellularization of trypsin, neutral protease and SDS solution method and fully rinsed with ultrasonic wave. Specific laser microporous technology was used to prepare the laser micropore porcine acellular dermal matrix (LPADM). SD rats were chose as the animal models and autologous skin was transplanted by one-step method to observe and detect the graft activity, immunogenicity and vascularization degree of the novel PADM. A porcelain white, shiny, soft and elastic dermal matrix was prepared in this study, the results showed low DNA residue and low cytotoxicity. HE staining and SEM observation revealed that the PADM had neither residual cells nor cell fragments, while the collagen bundles were intact and orderly arranged. All the SD rats survived. No infection or skin allergy was found after surgery. None of the animals lost weight. Histological examination showed that the LPADM was fully vascularized with little tissue destruction in the experiment group. Immunohistochemical staining for CD31 showed ideal vascularization in the experiment group, and immunohistochemical staining for TNF-α showed there were no statistical significance of inflammatory reaction in both groups. This study demonstrated that the novel PADM prepared by sequential combined decellularization of trypsin, neutral protease and SDS solution method and new laser microporous technique was effective and safe in animal transplantation.

Comparing the application of various engineered xenografts for skin defects: A systematic review

INTRODUCTION

Xenografts are a now a cornerstone in the management of wound dressings. Promising results were achieved since 1960 in the application of skin substitute for skin defects.

OBJECTIVE

The objective of this study was to evaluate the efficacy of various xenografts.

METHODS

A literature research was conducted using the following query: 'Porcine skin dermatology substitute', 'bovine skin dermatology substitute', 'xenograft skin substitute dermatology', 'xenografts skin defect', 'porcine skin defect', 'bovine skin defect'.

RESULTS

The review yielded 35 articles pertaining to the topic. Main indications for porcine and bovine xenograft application were burn wounds and post-traumatic wounds, respectively. Mean discharge date or length of stay was at the 6th day after porcine application, and the time of graft healing was reported for 33.7% (n = 510) of patients. Promising results were seen with Matriderm and split-thickness skin graft. Most wounds achieved an excellent cosmetic result with full range of motion and a smooth contour appearance. A great variety of tissue substitutes exist, and the choice of graft application should depend on a patient's factors, product availability, wound type, size, and physician's factors.

CONCLUSION

In summary, xenografts are more economic and affordable but have higher risk of infections compared to allografts.

Clinical outcomes of a novel porcine small intestinal submucosa patch for full-thickness hand skin defects: a retrospective investigation

OBJECTIVE

To investigate the clinical outcomes of a novel soft tissue repair patch (porcine small intestinal submucosa patch, SIS patch) in the treatment of full-thickness hand skin defects.

METHODS

From January 2017 to July 2019, 80 patients with hand soft tissue defects, who met the inclusion criteria, were retrospectively reviewed and divided into two groups. After debridement, patients in group A were treated with the novel SIS patch to cover the wound, and patients in group B were treated with autologous skin graft. The dimensions of skin defect area and healing outcome were evaluated and recorded. Scar assessment was carried out using Scar Cosmesis Assessment and Rating Scale (SCAR scale) at the last follow-up postoperation, and the recovery of wound sensation was assessed at the same time using British Medical Research Council (BMRC) grading of sensorimotor recovery. All the data were collected and statistically analyzed.

RESULTS

A total of 80 patients were enrolled in the study with 40 patients in each group. Four patients in group A and 5 patients in group B were excluded due to wound infection and lost to follow-up. There were 36 patients in group A and 35 patients in group B finally got follow-up postoperation with mean interval of 12.75 ± 5.61 months in group A and 14.11 ± 5.42 months in group B. The dimensions of skin defect area in group A ranged from 7.5 to 87.5 cm² (mean 25.97 ± 18.66 cm²) and in group B ranged from 7.5 to 86.25 cm² (mean 33.61 ± 19.27 cm²) which have no significant difference (P > 0.05). SCAR scale results of group A and group B were 10.98 ± 0.33 and 9.49 ± 0.35, respectively, and the difference was statistically significant (P < 0.05). BMRC grading results showed 6 cases of S4, 11 cases of S3+, 5 cases of S3, 6 cases of S2, 6 cases of S1 and 2 cases of S0 in group A, and 8 cases of S4, 10 cases of S3+, 7 cases of S3, 4 cases of S2, 5 cases of S1, and 1 case of S0 in group B, which had no significant difference between them (P > 0.05).

CONCLUSIONS

The novel SIS patch is an applicable biological material in the treatment of hand skin defect, which could achieve a better cosmetic appearance of the newborn skin tissue.

Skin substitutes for the management of mohs micrographic surgery wounds: a systematic review

The data on skin substitute usage for managing Mohs micrographic surgery (MMS) wounds remain limited. This systematic review aimed to provide an overview of skin substitutes employed for MMS reconstruction, summarize clinical characteristics of patients undergoing skin substitute-based repair after MMS, and identify advantages and limitations of skin substitute implementation. A systematic review of Ovid MEDLINE, EMBASE, Cochrane Library, and Web of Science databases, from inception to April 7, 2021, identified all cases of MMS defects repaired using skin substitutes. A total of 687 patients were included. The mean patient age was 70 years (range: 6-98 years). Commonly used skin substitutes were porcine collagen (n = 397), bovine collagen (n = 78), Integra (n = 53), Hyalofill (n = 43), amnion/chorion-derived grafts (n = 40), and allogeneic epidermal-dermal composite grafts (n = 35). Common factors influencing skin substitute selection were cost, healing efficacy, cosmetic outcome, patient comfort, and ease of use. Some articles did not specify patient and wound characteristics. Skin substitute usage in MMS reconstruction is not well-guided. Blinded randomized control trials comparing the efficacy of skin substitutes and traditional repair methods are imperative for establishing evidence-based guidelines on skin substitute usage following MMS.

Treatment of diabetic foot ulcers: review of the literature with regard to the TIME clinical decision support tool

OBJECTIVE

The aim of this clinically orientated paper is to offer an overview of diabetic foot ulcer (DFU) dressings generally, and more specifically, their use in the treatment of DFUs.

METHOD

The TIME clinical decision support tool (CDST) has been used as a clinical tool that can help clinicians bring together the different aspects of dressings for DFU treatment into a holistic approach to patient care.

RESULTS

DFUs are often difficult to heal, are painful and impact negatively on the individual's quality of life. Most DFU dressings are designed to support the healing of hard-to-heal wounds and represent one part of the management of DFUs. Apart from providing a moist environment, absorbing increased exudate, enhancing granulation and assisting in autolysis, the dressings need to be cost-effective. Wound dressing selection is based on clinical knowledge that ensures the dressing is most appropriate for the individual and the wound, taking into account the comorbidities that the individual may have.

CONCLUSION

This paper has highlighted how the use of the TIME CDST model can enhance clinical care and is a further tool clinicians should consider when developing and executing DFU treatment plans. Future research needs to focus on large multicentre studies using robust methodologies, given the current gaps in the evidence, to determine the effectiveness of dressing products for DFUs.

The utility of dermal fibroblasts in treatment of skin disorders: A paradigm of recessive dystrophic epidermolysis bullosa

Dermal fibroblasts are the most accessible cells in the skin that have gained significant attention in cell therapy. Applying dermal fibroblasts' regenerative capacity can introduce new patterns to develop cell-based therapies to treat skin disorders. Dermal fibroblasts originate from mesenchymal cells and are located within the dermis. These cells are mainly responsible for synthesizing glycosaminoglycans, collagens, and components of extracellular matrix supporting skin's structural integrity. Preclinical studies suggested that allogeneic and autologous dermal fibroblasts provide widespread and beneficial applications for wound healing, burn ulcers, and inherited skin disorders. In this regard, generating induced pluripotent stem cells (iPSCs) from fibroblasts and gene-edited fibroblasts are promising approaches for treating skin disorders. Here, we aimed to review literature about ongoing and completed clinical trials that applied fibroblasts and bioengineered fibroblasts as therapeutic agents for various skin disorders. This review explores cell therapy protocols from the earliest phase of allogeneic and autologous fibroblasts development in different benches to translating them into bedside-level treatment for skin disorders, particularly recessive dystrophic epidermolysis bullosa.

Biopolymer-based Scaffolds for Tissue Engineering Applications

Tissue engineering is governed by the use of cells and polymers. The cells may be accounted for the type of tissue to be targeted, while polymers may vary from natural to synthetic. The natural polymers have advantages such as non-immunogenic and complex structures that help in the formation of bonds in comparison to the synthetic ones. Various targeted drug delivery systems have been prepared using polymers and cells, such as nanoparticles, hydrogels, nanofibers, and microspheres. The design of scaffolds depends on the negative impact of material used on the human body and they have been prepared using surface modification technique or neo material synthesis. The dermal substitutes are a distinctive array that aims at the replacement of skin parts either through grafting or some other means. This review focuses on biomaterials for their use in tissue engineering. This article shall provide the bird's eye view of the scaffolds and dermal substitutes, which are naturally derived.

From Grafts to Human Bioengineered Vascularized Skin Substitutes

The skin plays an important role in the maintenance of the human's body physiological homeostasis. It acts as a coverage that protects against infective microorganism or biomechanical impacts. Skin is also implied in thermal regulation and fluid balance. However, skin can suffer several damages that impede normal wound-healing responses and lead to chronic wounds. Since the use of autografts, allografts, and xenografts present source limitations and intense rejection associated problems, bioengineered artificial skin substitutes (BASS) have emerged as a promising solution to address these problems. Despite this, currently available skin substitutes have many drawbacks, and an ideal skin substitute has not been developed yet. The advances that have been produced on tissue engineering techniques have enabled improving and developing new arising skin substitutes. The aim of this review is to outline these advances, including commercially available skin substitutes, to finally focus on future tissue engineering perspectives leading to the creation of autologous prevascularized skin equivalents with a hypodermal-like layer to achieve an exemplary skin substitute that fulfills all the biological characteristics of native skin and contributes to wound healing.

Biologic and Synthetic Cellular and/or Tissue-Based Products and Smart Wound Dressings/Coverings

Cellular and/or tissue-based products (CTPs) have advanced greatly in the past several decades and improve the ability to heal wounds more efficiently. Products can be characterized as nonviable cells, tissue based, animal; nonviable cells, tissue based, human; viable human cells, cultured in vitro, animal substrate; viable human cells, cultured in vitro, synthetic substrate; viable human cells, noncultured, intact tissue. There are approximately 77 different CTPs at the time of this writing, with many more being investigated. Cellular and/or tissue-based product selection, application, postapplication course, and patient selection depend on patient attributes, CTP specifications, and surgeon preference.

Therapeutic advances in wound healing

Wound healing is a complex physiological process that occurs in the human body involving the sequential activation of multiple cell types and signaling pathways in a coordinated manner. Chronic wounds and burns clearly decrease quality of life of the patients since they are associated with an increase in physical pain and socio-economical complications. Furthermore, incidence and prevalence of chronic wounds (unlike burns) have been increasing mainly due to population aging resulting in increased costs for national health systems. Thus, the development of new and more cost-effective technologies/therapies is not only of huge interest but also necessary to improve the long-term sustainability of national health systems. This review covers the current knowledge on recent technologies/therapies for skin regeneration, such as: wound dressings; skin substitutes; exogenous growth factor based therapy and systemic therapy; external tissue expanders; negative pressure; oxygen; shock wave, and photobiomodulation wound therapies. Associated benefits and risks as well as the clinical use and availability are all addressed for each therapy. Moreover, future trends in wound care including novel formulations using metallic nanoparticles and topical insulin are herein presented. These novel formulations have shown to be promising therapeutic options in the near future that may change the wound care paradigm.

Skin substitutes for acute and chronic wound healing: an updated review

Background: Skin substitutes are designed to accelerate wound healing by providing replacement of extracellular matrix and can be used to promote healing of both acute and chronic wounds.Aim: To describe advantages, disadvantages, and indications for different skin substitutes with the intention of providing a systematic framework that clinicians can easily utilize in clinical practice.Materials and method: We conducted a PubMed, Cochrane Library, and company website search for publications using various search terms associated with skin substitutes.Results: Skin substitutes can be categorized as epidermal, dermal, and composite, depending on the skin component they contain, and further split into different categories depending on their composition and source of material, including xenograft, acellular allograft, cellular allograft, autograft, and synthetic skin substitutes. Because there is no ideal option for skin substitutes that meet all the criteria for optimal wound healing, there is ongoing research evaluating and developing different skin substitute options.Conclusion: Our model of skin substitutes was organized based on the different layers of cutaneous involvement and the origin of the product material. We believe that this framework provides a practical guide for selection of the most appropriate skin substitute based on clinical indication.

Prediction of stump healing in lower limb amputation: a narrative review

Both types of diabetes, as well as different forms of acquired diabetes, are associated with diabetic peripheral neuropathy. Diabetic foot ulcers (DFU) is the condition most commonly related to somatic peripheral neuropathy, often leading to gangrene and limb amputation. Independent from large-vessel disease, sensory loss may result in DFU development and even amputation. The crucial part of any lower limb amputation is the stump healing process, which represents the central goal of postoperative management. Despite the importance attributed to this process, a standard set of guidelines regarding efficient healing methods is yet to be formulated. Health professionals are faced with the challenge of assessing the different risk factors and deciding which has a greater influence on the stump healing rate. There is currently an insufficient number of studies regarding factors effecting lower limb amputation. The main purpose of this review is to discuss the markers that can be helpful in the prediction of stump healing in patients who have undergone lower limb amputation.

Soybean-modified polyamide-6 mats as a long-term cutaneous wound covering

Engineered skin coverings have been adopted clinically to support extensive and deep wounds that result in fewer healthy skin remaining and therefore take longer to heal. Nonetheless, these biomaterials demand intensive labor and an expensive final cost. In comparison to conventional bandages, which do not meet all the requirements of wound care, electrospun fiber mats could potentially provide an excellent environment for healing. In this work, we developed two nanostructured scaffolds based on polyamide-6 (PA-6) to be tested as a wound covering in a rat model of full-thickness incisional wound healing. The central idea was to create a bioconstruct that is simple to implement and biologically safe, with a high survival rate, which provides physical support and biological recognition for new functional tissues. An unmodified PA-6 and a soybean-modified PA-6 were employed as nanofibrillar matrices in this study. The biomaterials showed a dimensional homology to natural extracellular matrix components and neither in vitro toxicity nor in vivo side effects. Both polymeric scaffolds were resistant to the sterilization process and could promote the attachment of 3T3 fibroblast cells, besides successfully incorporating the growth factor PDGF-BB, which had its bioactivity extended for up to 12 h under simulated conditions. The modification of PA-6 chains with a fatty acid derivative increased the scaffold's surface free energy, favoring cell proliferation, collagen formation, and ECM secretion. These results confirm the potential of these materials as a topical dermal covering for skin regeneration.

Therapeutic strategies for skin regeneration based on biomedical substitutes

Regenerative medicine and tissue engineering (TE) have experienced significant advances in the development of in vitro engineered skin substitutes, either for replacement of lost tissue in skin injuries or for the generation of in vitro human skin models to research. However, currently available skin substitutes present different limitations such as expensive costs, abnormal skin microstructure and engraftment failure. Given these limitations, new technologies, based on advanced therapies and regenerative medicine, have been applied to develop skin substitutes with several pharmaceutical applications that include injectable cell suspensions, cell-spray devices, sheets or 3Dscaffolds for skin tissue regeneration and others. Clinical practice for skin injuries has evolved to incorporate these innovative applications to facilitate wound healing, improve the barrier function of the skin, prevent infections, manage pain and even to ameliorate long-term aesthetic results. In this article, we review current commercially available skin substitutes for clinical use, as well as the latest advances in biomedical and pharmaceutical applications used to design advanced therapies and medical products for wound healing and skin regeneration. We highlight the current progress in clinical trials for wound healing as well as the new technologies that are being developed and hold the potential to generate skin substitutes such as 3D bioprinting-based strategies.

Synthetic polymeric biomaterials for wound healing: a review

Wounds are of a variety of types and each category has its own distinctive healing requirements. This realization has spurred the development of a myriad of wound dressings, each with specific characteristics. It is unrealistic to expect a singular dressing to embrace all characteristics that would fulfill generic needs for wound healing. However, each dressing may approach the ideal requirements by deviating from the 'one size fits all approach', if it conforms strictly to the specifications of the wound and the patient. Indeed, a functional wound dressing should achieve healing of the wound with minimal time and cost expenditures. This article offers an insight into several different types of polymeric materials clinically used in wound dressings and the events taking place at cellular level, which aid the process of healing, while the biomaterial dressing interacts with the body tissue. Hence, the significance of using synthetic polymer films, foam dressings, hydrocolloids, alginate dressings, and hydrogels has been reviewed, and the properties of these materials that conform to wound-healing requirements have been explored. A special section on bioactive dressings and bioengineered skin substitutes that play an active part in healing process has been re-examined in this work.

Advances in Skin Regeneration Using Tissue Engineering

Tissue engineered skin substitutes for wound healing have evolved tremendously over the last couple of years. New advances have been made toward developing skin substitutes made up of artificial and natural materials. Engineered skin substitutes are developed from acellular materials or can be synthesized from autologous, allograft, xenogenic, or synthetic sources. Each of these engineered skin substitutes has their advantages and disadvantages. However, to this date, a complete functional skin substitute is not available, and research is continuing to develop a competent full thickness skin substitute product that can vascularize rapidly. There is also a need to redesign the currently available substitutes to make them user friendly, commercially affordable, and viable with longer shelf life. The present review focuses on providing an overview of advances in the field of tissue engineered skin substitute development, the availability of various types, and their application.

Production of a Bilayered Self-Assembled Skin Substitute Using a Tissue-Engineered Acellular Dermal Matrix

Our bilayered self-assembled skin substitutes (SASS) are skin substitutes showing a structure and functionality very similar to native human skin. These constructs are used, in life-threatening burn wounds, as permanent autologous grafts for the treatment of such affected patients even though their production is exacting. We thus intended to shorten their current production time to improve their clinical applicability. A self-assembled decellularized dermal matrix (DM) was used. It allowed the production of an autologous skin substitute from patient's cells. The characterization of SASS reconstructed using a decellularized dermal matrix (SASS-DM) was performed by histology, immunofluorescence, transmission electron microscopy, and uniaxial tensile analysis. Using the SASS-DM, it was possible to reduce the standard production time from about 8 to 4 and a half weeks. The structure, cell differentiation, and mechanical properties of the new skin substitutes were shown to be similar to the SASS. The decellularization process had no influence on the final microstructure and mechanical properties of the DM. This model, by enabling the production of a skin substitute in a shorter time frame without compromising its intrinsic tissue properties, represents a promising addition to the currently available burn and wound treatments.

Real-time three-dimensional imaging of epidermal splitting and removal by high-definition optical coherence tomography

While real-time 3-D evaluation of human skin constructs is needed, only 2-D non-invasive imaging techniques are available. The aim of this paper is to evaluate the potential of high-definition optical coherence tomography (HD-OCT) for real-time 3-D assessment of the epidermal splitting and decellularization. Human skin samples were incubated with four different agents: Dispase II, NaCl 1 M, sodium dodecyl sulphate (SDS) and Triton X-100. Epidermal splitting, dermo-epidermal junction, acellularity and 3-D architecture of dermal matrices were evaluated by High-definition optical coherence tomography before and after incubation. Real-time 3-D HD-OCT assessment was compared with 2-D en face assessment by reflectance confocal microscopy (RCM). (Immuno) histopathology was used as control. HD-OCT imaging allowed real-time 3-D visualization of the impact of selected agents on epidermal splitting, dermo-epidermal junction, dermal architecture, vascular spaces and cellularity. RCM has a better resolution (1 μm) than HD-OCT (3 μm), permitting differentiation of different collagen fibres, but HD-OCT imaging has deeper penetration (570 μm) than RCM imaging (200 μm). Dispase II and NaCl treatments were found to be equally efficient in the removal of the epidermis from human split-thickness skin allografts. However, a different epidermal splitting level at the dermo-epidermal junction could be observed and confirmed by immunolabelling of collagen type IV and type VII. Epidermal splitting occurred at the level of the lamina densa with dispase II and above the lamina densa (in the lamina lucida) with NaCl. The 3-D architecture of dermal papillae and dermis was more affected by Dispase II on HD-OCT which corresponded with histopathologic (orcein staining) fragmentation of elastic fibres. With SDS treatment, the epidermal removal was incomplete as remnants of the epidermal basal cell layer remained attached to the basement membrane on the dermis. With Triton X-100 treatment, the epidermis was not removed. In conclusion, HD-OCT imaging permits real-time 3-D visualization of the impact of selected agents on human skin allografts.

Evidence-Based Approach to Advanced Wound Care Products

There is increasing pressure from industry to use advanced wound care products and technologies. Many are very expensive but promise to reduce overall costs associated with wound care. Compelling anecdotal evidence is provided that inevitably shows wounds that failed all other treatments but responded positively to the subject product. Evidence-based medicine is the standard by which physician-scientists must make their clinical care decisions. In an attempt to provide policy makers with the most current evidence on advanced wound care products, the Department of Veteran Affairs conducted an Evidence-based Synthesis Program review of advanced wound care products. This paper suggests how to take this information and apply it to policy to drive evidence-based care to improve outcomes and fiduciary responsibility.

Advanced Therapeutic Dressings for Effective Wound Healing--A Review

Advanced therapeutic dressings that take active part in wound healing to achieve rapid and complete healing of chronic wounds is of current research interest. There is a desire for novel strategies to achieve expeditious wound healing because of the enormous financial burden worldwide. This paper reviews the current state of wound healing and wound management products, with emphasis on the demand for more advanced forms of wound therapy and some of the current challenges and driving forces behind this demand. The paper reviews information mainly from peer-reviewed literature and other publicly available sources such as the US FDA. A major focus is the treatment of chronic wounds including amputations, diabetic and leg ulcers, pressure sores, and surgical and traumatic wounds (e.g., accidents and burns) where patient immunity is low and the risk of infections and complications are high. The main dressings include medicated moist dressings, tissue-engineered substitutes, biomaterials-based biological dressings, biological and naturally derived dressings, medicated sutures, and various combinations of the above classes. Finally, the review briefly discusses possible prospects of advanced wound healing including some of the emerging physical approaches such as hyperbaric oxygen, negative pressure wound therapy and laser wound healing, in routine clinical care.

Evaluation of Antimicrobial and Healing Activities of Frog Skin on Guinea Pigs Wounds

Background:

Frog skin secretions have potentials against a wide spectrum of bacteria. Also, frog skin compositions have healing properties.

Objectives:

The aim of this study was to investigate the antibacterial potentials along with healing properties of frog skin Rana ridibunda, a species which thoroughly lives in Iran marshes, as a biological dressing on wounds.

Materials and Methods:

In this study, excisional wounds, dressed with frog skin, were compared between experimental and control groups of guinea pigs. In the experimental groups, wounds were dressed with the dermal (FS) and epidermal (RFS) sides of fresh frog R. ridibunda skin, while only usual cotton gauze covered the wounds of the control group. Furthermore, microbial samples were taken on different days (0, 3, 5, and 7 days post injury) to count the number of the colony-forming units. Additionally, the microbial penetration test was performed on frog skin and then the progression of wound closure was evaluated.

Results:

In the microbial studies, the bacterial load considerably declined in the wounds treated with FS and RFS compared with the control wounds. On day 7 post injury, the numbers of the colony-forming units for the FS, RFS, and control groups were 6.75, 105, and 375, respectively. In the penetration test, fresh frog skin showed to be a bacterial resistant dressing. The results revealed that the rate of wound closure in the experimental groups significantly was accelerated in comparison with that in the control group.

Conclusions:

Our results demonstrated the antimicrobial properties of frog skin as a wound dressing, which has antimicrobial effects per se. This biological dressing shows promise as an effective biological wound dressing insofar as not only is it capable of resisting microbes and accelerating wound healing but also it is cost-effective and easy to use.

Human acellular dermal wound matrix for treatment of DFU: literature review and analysis

Diabetic foot ulcers (DFUs) affect a significant number of people and the treatment is challenging and costly. Since only a small portion of patients respond to standard care, the majority require more advanced wound healing interventions. Human acellular dermal matrices-regenerative tissue matrices derived from human tissue and processed from screened donated skin-can aid wound closure by restoring the missing physiological factors to the microenvironment. A literature review of the clinical literature was performed to estimate the comparative effectiveness of one specific human acellular dermal wound matrix (HADWM; Graftjacket regenerative tissue matrix) versus standard care in healing DFUs. Outcomes from three prospective, controlled clinical trials, which included 154 patients with DFUs, were pooled. A comparative analysis revealed a statistically significant reduction in mean wound healing time, 1.7 weeks, as well as a nearly four-fold improvement in the chance of healing ulcers treated with HADWM versus moist wound-care. These pooled results suggest that HADWM may improve healing outcomes for these difficult-to-heal lower extremity wounds.

DECLARATION OF INTEREST

Alexander Reyzelman is a consultant for KCI, an Acelity company.

Arachidonic acid promotes skin wound healing through induction of human MSC migration by MT3-MMP-mediated fibronectin degradation

Arachidonic acid (AA) is largely released during injury, but it has not been fully studied yet how AA modulates wound repair with stem cells. Therefore, we investigated skin wound-healing effect of AA-stimulated human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs) in vivo and its molecular mechanism in vitro. We found that transplantation of hUCB-MSCs pre-treated with AA enhanced wound filling, re-epithelization, and angiogenesis in a mouse skin excisional wound model. AA significantly promoted hUCB-MSCs migration after a 24 h incubation, which was inhibited by the knockdown of G-protein-coupled receptor 40 (GPR40). AA activated mammalian target of rapamycin complex 2 (mTORC2) and Akt^ser473 through the GPR40/phosphoinositide 3-kinase (PI3K) signaling, which was responsible for the stimulation of an atypical protein kinase C (PKC) isoform, PKCζ. Subsequently, AA stimulated phosphorylation of p38 MAPK and transcription factor Sp1, and induced membrane type 3-matrix metalloproteinase (MT3-MMP)-dependent fibronectin degradation in promoting hUCB-MSCs motility. Finally, the silencing of MT3-MMP in AA-stimulated hUCB-MSCs failed to promote the repair of skin wounds owing to impaired cell motility. In conclusion, AA enhances skin wound healing through induction of hUCB-MSCs motility by MT3-MMP-mediated fibronectin degradation, which relies on GPR40-dependent mTORC2 signaling pathways.

Methods for the preparation of an autologous serum-free cultured epidermis and for autografting applications

Cell culture techniques for producing a three-dimensional autologous epidermal autograft (cultured epidermal autograft) suitable for tissue grafting and wound healing procedures are described. This chapter commences with surgical biopsy of patient's skin tissue, further reduction of skin tissues to keratinocyte cells by enzymatic treatment, and recovery of viable adult keratinocytes in a new balanced buffered salt media supportive of the growth of clonally enriched isolated basal keratinocytes. Culture techniques required for the formation of a hole-free monolayer of undifferentiated basal keratinocytes without the use of an organotypic matrix substrate are accomplished with a specially designed nutrient basal media (HECK 109) that is a chemically defined and subsequent culture in this serum-free culture media supplemented with hormones and two human recombinant protein growth factors (EGF and IGF-1). Further culture techniques and media manipulations, including brief exposure to β-TGF to induce reversible G1-phase growth arrest, are followed by para-synchronous induction of a multilayered stratification and keratinizing epidermal differentiation, yielding a living three-dimensional epidermis formed entirely in cell culture. Protocols are listed for its enzymatic removal, floatation, and transfer for shipment to the clinic ready for surgical grafting to the self-same patient's debrided chronic leg ulcers. Recent clinical trial results have demonstrated the utility and efficacy of these grafts in forming durably healed chronic wounds.

Progress towards cell-based burn wound treatments

Cell therapy as part of the concept of regenerative medicine represents an upcoming platform technology. Although cultured epidermal cells have been used in burn treatment for decades, new developments have renewed the interest in this type of treatment. Whereas early results were hampered by long culture times in order to produce confluent sheets of keratinocytes, undifferentiated proliferating cells can nowadays be applied on burns with different application techniques. The application of cells on carriers has improved early as well as long-term results in experimental settings. The results of several commercially available epidermal substitutes for burn wound treatment are reviewed in this article. These data clearly demonstrate a lack of randomized comparative trials and application of measurable outcome parameters. Experimental research in culture systems and animal models has demonstrated new developments and proof of concepts of further improvements in epidermal coverage. These include combinations of epidermal cells and mesenchymal stem cells, and the guidance of both material and cell interactions towards regeneration of skin appendages as well as vascular and nerve structures.

Dermal skin substitutes for upper limb reconstruction: current status, indications, and contraindications

Dermal skin substitutes are a group of biologically engineered materials composed of collagen and glycosaminoglycans and are devoid of cellular structures. These biodegradable materials act as an artificial dermis to promote neovascularization and neodermis formation. Their applications in soft tissue reconstructions are rapidly expanding. In this article, the indications, advantages, and limitations of dermal skin substitutes for reconstruction of soft tissue defects of the upper extremity are reviewed.

Animal derived products may conflict with religious patients' beliefs

Background

Implants and drugs with animal and human derived content are widely used in medicine and surgery, but information regarding ingredients is rarely obtainable by health practitioners. A religious perspective concerning the use of animal and human derived drug ingredients has not thoroughly been investigated. The purpose of this study was to clarify which parts of the medical and surgical treatments offered in western world-hospitals that conflicts with believers of major religions.

Methods

Religious and spiritual leaders of the six largest religions worldwide (18 branches) were contacted. A standardised questionnaire was sent out regarding their position on the use of human and animal derived products in medical and surgical treatments.

Results

Of the 18 contacted religious branches, 10 replied representing the 6 largest religions worldwide. Hindus and Sikhs did not approve of the use of bovine or porcine derived products, and Muslims did not accept the use of porcine derived drugs, dressings or implants. Christians (including Jehovah’s Witnesses), Jews and Buddhists accepted the use of all animal and human derived products. However, all religions accepted the use of all these products in case of an emergency and only if alternatives were not available.

Conclusions

The views here suggest that religious codes conflict with some treatment regimens. It is crucial to obtain informed consent from patients for the use of drugs and implants with animal or human derived content. However, information on the origin of ingredients in drugs is not always available to health practitioners.

Stem Cells and Healing: Impact on Inflammation

SIGNIFICANCE

The number of patients with nonhealing wounds has rapidly accelerated over the past 10 years in both the United States and worldwide. Some causative factors at the macro level include an aging population, epidemic numbers of obese and diabetic patients, and an increasing number of surgical procedures. At the micro level, chronic inflammation is a consistent finding.

RECENT ADVANCES

A number of treatment modalities are currently used to accelerate wound healing, including energy-based modalities, scaffoldings, the use of mechano-transduction, cytokines/growth factors, and cell-based therapies. The use of stem cell therapy has been hypothesized as a potentially useful adjunct for nonhealing wounds. Specifically, mesenchymal stem cells (MSCs) have been shown to improve wound healing in several studies. Immune modulating properties of MSCs have made them attractive treatment options.

CRITICAL ISSUES

Current limitations of stem cell therapy include the potentially large number of cells required for an effect, complex preparation and delivery methods, and poor cell retention in targeted tissues. Comparisons of published in-vitro and clinical trials are difficult due to cell preparation techniques, passage number, and the impact of the micro-environment on cell behavior.

FUTURE DIRECTIONS

MSCs may be more useful if they are preactivated with inflammatory cytokines such as tumor necrosis factor alpha or interferon gamma. This article will review the current literature with regard to the use of stem cells for wound healing. In addition the anti-inflammatory effects of MSCs will be discussed along with the potential benefits of stem cell preactivation.

Autologous skin substitute for hard-to-heal ulcers: retrospective analysis on safety, applicability, and efficacy in an outpatient and hospitalized setting

Chronic ulcers ((arterio)venous, decubitus, or postoperative) have no tendency to heal within a period of at least 3 months despite optimal therapy according to internationally accepted guidelines. This retrospective study evaluates the safety and efficacy of an autologous, dermal-epidermal skin substitute (SS) for treating ulcers of various origins. Ulcers were treated within 7 Dutch centers over 5 years. Sixty-six ulcers (size: 0.75-150 cm²; duration: 0.25-32 years) with a follow-up time of 24 weeks after a single-skin substitute application were assessed. Wound-bed preparation consisted of vacuum-assisted-closure-therapy (5 days, hospitalized) or application of acellular dermis (5-7 days, outpatient). Time to heal, adverse events, and recurrence 1 year after complete healing were recorded. Complete ulcer healing occurred in 36 of 66 ulcers (55%) at 24 weeks. At that time point, a further 29% of ulcers showed decrease in ulcer size between 50 and 99%. No difference was observed between the hospitalized vs. outpatient treatment with complete healing. There were 32 of 36 healed ulcers that were available for follow-up 1 year after complete closure, of which 27 (84%) were still closed. Only two minor/moderate possibly related adverse events were recorded. This retrospective analysis shows that SS provides a safe and successful treatment for particularly chronic ulcers of various origins.

Successful treatment of complex traumatic and surgical wounds with a foetal bovine dermal matrix

A foetal bovine dermal repair scaffold (PriMatrix, TEI Biosciences) was used to treat complex surgical or traumatic wounds where the clinical need was to avoid skin flaps and to build new tissue in the wound that could be reepithelialised from the wound margins or closed with a subsequent application of a split-thickness skin graft (STSG). Forty-three consecutive cases were reviewed having an average size of 79·3 cm(2) , 50% of which had exposed tendon and/or bone. In a subset of wounds (44·7%), the implantation of the foetal dermal collagen scaffold was also augmented with negative pressure wound therapy (NPWT). Complete wound healing was documented in over 80% of the wounds treated, whether the wound was treated with the foetal bovine dermal scaffold alone (95·2%) or when supplemented with NPWT (82·4%). The scaffold successfully incorporated into wounds with exposed tendon and/or bone to build vascularised, dermal-like tissue. The new tissue in the wound supported STSGs however, in the majority of the cases (88·3%); wound closure was achieved through reepithelialisation of the incorporated dermal scaffold by endogenous wound keratinocytes. The foetal bovine dermal repair scaffold was found to offer an effective alternative treatment strategy for definitive closure of challenging traumatic or surgical wounds on patients who were not suitable candidates for tissue flaps.

Topical effects of frog "Rana ridibunda" skin secretions on wound healing and reduction of wound microbial load

ETHNOPHARMACOLOGICAL RELEVANCE

Study of the interrelationships between human and the animals in their environment has always been a subject of interest and caused discoveries of the animal applications in medicine. From the latest century, these remedies called back in traditional medicine of Vietnam and South America and frog skin was used as a biological dressing and had good effects in healing wounds. Also, frog skin secretions have wound healing properties and reduce inflammation. In this study we applied these secretions in the form of ointment to investigate their healing activities.

MATERIALS AND METHODS

Skin secretions were extracted from Rana ridibunda to evaluate their effects on wound healing in mice. Secretion used as raw extract (RE) and ultrafiltrated extract, using a membrane with cutoff 10kDa as under 10kDa (U10E), was administrated as ointment every 48h on wound site. Control group was left without any treatment and also there was other group treated with ointment (O group) alone. On 2, 4 and 6 days post injury, animals were euthanized and images were taken for wound closure evaluation. Then wound locations were removed for histological assays. Also wound microbial load was examined. Observational parameters including wound closure and wound microbiology in experimental groups compared with the control and O groups have been studied.

RESULTS

The results showed U10E group has better effects than RE, O and control groups. Histological parameters, including numbers of inflammatory and fibroblast cells and amount of collagen fibers, neovascularization, as well, represented greater degree of wound healing in U10E group compared with RE, O, and control groups.

CONCLUSIONS

Our results showed that frog skin secretions were significantly effective in promoting wound healing process. The U10E extract from the frog R. ridibunda possesses a potent accelerating wound healing effect that promises good potential for clinical application in wound care. Further studies will be required to characterize special molecules encompassing healing properties.