Dermal matrices and bioengineered skin substitutes: a critical review of current options

From Bank Preparation to Clinical Use of Homologous Skin Allografts in Wound Healing: A Sustainable Approach

Given progressive population ageing and the increase in the number of patients with comorbidities, the management of chronic and/or hard-to-heal wounds (HHWs) nowadays represents a common problem in many clinical settings. In these cases, standard strategies may not be sufficient. Autologous grafting represent the gold standard for permanent wound closure, but is almost never realized when the skin loss is extensive/the patient is young. The grafting of homologous skin/dermal tissue procured from cadaver donors (i.e., allografting) represents the best alternative, especially when the dermal component is lost. This request supports the activities of skin bank establishments (including donor screening, skin procurement, processing, storage, and distribution) that are regulated by specific guidelines and need to continuously meet quality standard requirements. The aim of this work is to both give specific insights of all the procedures implied in allograft preparation as well as an overview of their practical application in the treatment of different HHWs. The particular characteristics of each skin/dermal allograft released by Siena Skin Bank (cryopreserved/glycerol-preserved skin/de-epidermized dermis, acellular lyophilized de-epidermized dermis/reticular dermis) are also discussed. The exemplificative series of HHWs managed in the Dermatology Department of Siena were classified according their etiology into post-traumatic, vascular (arterial/venous/mixed/lymphatic), inflammatory, surgical, and heat/chemical burns. Globally, the clinical advantages obtained include: acceleration of healing process, pain sparing, resistance to bacterial contamination, dermal regeneration (instead of scarring), and better aesthetic-functional outcome.

Engineering Shape to Overcome Contraction: The Role of Polymer-Collagen Hybrids in Advanced Dermal Substitutes

Collagen gels are the standard dermal equivalents par excellence, however the problem of rapid cell-mediated contraction remains unresolved. Therefore, the development of hybrid constructs (HCs) based on collagen and polymeric scaffolds is proposed to address the mechanical instability that usually limits the formation of new, functional tissue. Equally important, these synthetic structures should be temporary (degradable) while ensuring that cells are well-adapted to the new extracellular environment. In this study, we screened a library of scaffolds made of various polymers, including homopolymers of polycaprolactone (PCL) and poly D,L-lactide (PLA50), their blends (PCL/PLA50), and copolymers (poly(D,L-lactide-co-caprolactone), PCLLA50) to prepare HCs in a layer-by-layer fashion. The properties of polymers and copolymers along with their processability by electrospinning and 3D-printing were evaluated. Then, we assessed the HCs resistance toward cell-mediated contraction as well as the degradation of the polymeric scaffolds. Our results indicate that scaffolds with higher PLA50 content (e.g., PLA50 100%, PCL/PLA50 or PCLLA50, both at 50/50 caprolactone-to-D,L-lactide molar ratio) presented more drawbacks in terms of handleability and processing, while those with greater PCL presence showed structural steadiness and ease to use. All the scaffolds integrated well with the collagen gel to form the corresponding HCs. With few exceptions, the HCs demonstrated good resistance to cell-derived contraction over 3 weeks. Notably, HCs based on PCLLA50 90/10 (both versions, electrospun or 3D-printed) performed best, showing only a 5%-17% area reduction compared to the 93% observed in collagen-only gels. This copolymer displayed hydrolytic degradation depending on its shape, with up to 45% and 65% loss of molecular weight for the electrospun and 3D-printed forms, respectively, correlating with their progressive change in mechanical features. HCs containing PCLLA50 90/10 also exhibited a better fibroblast distribution, enhanced myofibroblastic differentiation, and a three-fold increase in cell proliferation (when the electrospun type was used) compared to collagen controls. These findings were instrumental in selecting a potential HC that might be used for future experiments in vivo.

Nanofat Improves Vascularization and Tissue Integration of Dermal Substitutes without Affecting Their Biocompatibility

Dermal substitutes require sufficient tissue integration and vascularization to be successfully covered with split-thickness skin grafts. To rapidly achieve this, we provide the proof of principle for a novel vascularization strategy with high translational potential. Nanofat was generated from subcutaneous adipose tissue of green fluorescence protein (GFP)+ C57BL/6J donor mice and seeded onto small samples (4 mm in diameter) of the clinically approved dermal substitute Integra®. These samples and non-seeded controls were then implanted into full-thickness skin defects in the dorsal skinfold chamber of C57BL/6J wild-type mice and analyzed by intravital fluorescence microscopy, histology and immunohistochemistry over a 14-day period. Nanofat-seeded dermal substitutes exhibited an accelerated vascularization, as indicated by a significantly higher functional microvessel density on days 10 and 14 when compared to controls. This was primarily caused by the reassembly of GFP+ microvascular fragments inside the nanofat into microvascular networks. The improved vascularization promoted integration of the implants into the surrounding host tissue, which finally exhibited an increased formation of a collagen-rich granulation tissue. There were no marked differences in the inflammatory host tissue reaction to nanofat-seeded and control implants. These findings demonstrate that nanofat significantly improves the in vivo performance of dermal substitutes without affecting their biocompatibility.

Analysis of the Radial Forearm Phalloplasty Donor Site: Do Dermal Matrices Improve Donor Site Morbidity?

Background

The radial forearm free flap is frequently chosen for phalloplasty; however, flap size required for phalloplasty is associated with a large scar burden and functional concerns. We sought to investigate donor site functionality, aesthetics, and volume deficits in a cohort of individuals who underwent radial forearm phalloplasty (RFP) with donor site skin grafting alone or dermal substitute and subsequent skin grafting.

Methods

Donor site functionality was assessed using the quick Disabilities of Arm, Shoulder, and Hand (qDASH). Patient- and clinician-reported aesthetics were assessed using the Patient and Observer Scar Assessment Scale (POSAS). An Artec Leo three-dimensional scanner was used to measure volumetric differences from the donor site forearm and contralateral forearm.

Results

Fifteen patients who underwent RFP agreed to participate. No statistically significant differences were identified between different donor site closure methods regarding qDASH, patient-reported POSAS, or total volumetric deficits. A blinded clinician reported that POSAS approached significance at 4.7 for biodegradable temporizing matrix (BTM), 4.2 for Integra, and 3.0 for split-thickness skin graft (P = 0.05). No statistically significant differences were identified regarding distal, middle, or proximal volume deficits; however, a trend was observed regarding total volumetric deficits with BTM experiencing the lowest deficit (10.3 cm3) and skin graft experiencing the highest deficit (21.5 cm3, P = 0.82).

Conclusions

The addition of dermal matrix (BTM or Integra) to the treatment algorithm for RFP did not show statistically significant improvement in donor site volume deficits, patient-reported scar appearance (POSAS), or functionality (qDASH).

Outcomes of Biodegradable Temporizing Matrix for Soft Tissue Reconstruction of the Hand and Extremities

Background

NovoSorb biodegradable temporizing matrix (BTM) is a novel, bilayer, synthetic skin substitute made of biodegradable polyurethane foam covered with a sealing membrane. BTM has demonstrated excellent outcomes in burn literature; however, few studies have been published for hand and extremity soft tissue reconstruction.

Methods

All patients who underwent extremity reconstruction with BTM from 2018 to 2023 were reviewed. Demographics, presentations, and clinical outcomes were recorded.

Results

A total of 86 cases from 54 patients (53.7% pediatric; age range: 0-81 years) were included. Common indications included trauma (36%), infection (18.6%), and malignancy (11.6%). BTM was placed over exposed tendon (38.4%), bone (19%), joints (12.8%), nerves (8.1%), and/or blood vessels (7%). BTM served as temporary wound coverage in 26 cases. Complications included hematoma (8.1%), infection (4.7%), and spontaneous delamination (4.7%). Wound closure was successfully obtained without flap use in 93.3%. Poor BTM take was associated with peripheral vascular disease, hypertension, immunosuppression, and BTM hematoma and infection (<0.05).

Conclusion

This study contributes to the growing body of evidence favoring BTM use in challenging reconstructive cases. Although prospective comparative studies are forthcoming, BTM likely has broad applications in reconstructive surgery.

Electrospun skin dressings for diabetic wound treatment: a systematic review

Abstract

Diabetes mellitus is a metabolic disease characterized by persistent hyperglycemia associated with a lack of insulin production or insulin resistance. In diabetic patients, the capacity for healing is generally decreased, leading to chronic wounds. One of the most common treatments for chronic wounds is skin dressings, which serve as protection from infection, reduce pain levels, and stimulate tissue healing. Furthermore, electrospinning is one of the most effective techniques used for manufacturing skin dressings.

Objective

The purpose of this study was to perform a systematic review of the literature to examine the effects of electrospun skin dressings from different sources in the process of healing skin wounds using in vivo experiments in diabetic rats.

Methods

The search was carried out according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), and the Medical Subject Headings (MeSH) descriptors were defined as "wound dressing," "diabetes," "in vivo," and "electrospun." A total of 14 articles were retrieved from PubMed and Scopus databases.

Results

The results were based mainly on histological analysis and macroscopic evaluation, demonstrating moderate evidence synthesis for all experimental studies, showing a positive effect of electrospun skin dressings for diabetic wound treatment.

Conclusion

This review confirms the significant benefits of using electrospun skin dressings for skin repair and regeneration. All the inks used were demonstrated to be suitable for dressing manufacturing. Moreover, in vivo findings showed full wound closure in most of the studies, with well-organized dermal and epidermal layers.

A Model to Study Wound Healing Over Exposed Avascular Structures in Rodents With a 3D-Printed Wound Frame

BACKGROUND

Soft tissue defects with exposed avascular structures require reconstruction with well-vascularized tissues. Extensive research is ongoing to explore tissue engineered products that provide durable coverage. However, there is a lack of controlled and affordable testbeds in the preclinical setting to reflect this challenging clinical scenario. We aimed to address this gap in the literature and develop a feasible and easily reproducible model in rodents that reflects an avascular structure in the wound bed.

METHODS

We created 20 × 20 mm full thickness wounds on the dorsal skin of Lewis rats and secured 0.5-mm-thick silicone sheets of varying sizes to the wound bed. A 3D-printed wound frame was designed to isolate the wound environment. Skin graft and free flap survival along with exposure of the underlying silicone was assessed. Rats were followed for 4 weeks with weekly dressing changes and photography. Samples were retrieved at the endpoint for tissue viability and histologic analysis.

RESULTS

The total wound surface area was constant throughout the duration of the experiment in all groups and the wound frames were well tolerated. The portion of the skin graft without underlying silicone demonstrated integration with the underlying fascia and a histologically intact epidermis. Gradual necrosis of the portion of the skin graft overlying the silicone sheet was observed with varying sizes of the silicone sheet. When the size of the silicone sheet was reduced from 50% of the wound surface area, the portion surviving over the silicone sheet increased at the 4-week timepoint. The free flap provided complete coverage over the silicone sheet.

CONCLUSION

We developed a novel model of rodent wound healing to maintain the same wound size and isolate the wound environment for up to 4 weeks. This model is clinically relevant to a complex wound with an avascular structure in the wound bed. Skin grafts failed to completely cover increasing sizes of the avascular structure, whereas the free flap was able to provide viable coverage. This cost-effective model will establish an easily reproducible platform to evaluate more complex bioengineered wound coverage solutions.

Hydrogel-mediated extracellular vesicles for enhanced wound healing: the latest progress, and their prospects for 3D bioprinting

Extracellular vesicles have shown promising tissue recovery-promoting effects, making them increasingly sought-after for their therapeutic potential in wound treatment. However, traditional extracellular vesicle applications suffer from limitations such as rapid degradation and short maintenance during wound administration. To address these challenges, a growing body of research highlights the role of hydrogels as effective carriers for sustained extracellular vesicle release, thereby facilitating wound healing. The combination of extracellular vesicles with hydrogels and the development of 3D bioprinting create composite hydrogel systems boasting excellent mechanical properties and biological activity, presenting a novel approach to wound healing and skin dressing. This comprehensive review explores the remarkable mechanical properties of hydrogels, specifically suited for loading extracellular vesicles. We delve into the diverse sources of extracellular vesicles and hydrogels, analyzing their integration within composite hydrogel formulations for wound treatment. Different composite methods as well as 3D bioprinting, adapted to varying conditions and construction strategies, are examined for their roles in promoting wound healing. The results highlight the potential of extracellular vesicle-laden hydrogels as advanced therapeutic tools in the field of wound treatment, offering both mechanical support and bioactive functions. By providing an in-depth examination of the various roles that these composite hydrogels can play in wound healing, this review sheds light on the promising directions for further research and development. Finally, we address the challenges associated with the application of composite hydrogels, along with emerging trends of 3D bioprinting in this domain. The discussion covers issues such as scalability, regulatory considerations, and the translation of this technology into practical clinical settings. In conclusion, this review underlines the significant contributions of hydrogel-mediated extracellular vesicle therapy to the field of 3D bioprinting and wound healing and tissue regeneration. It serves as a valuable resource for researchers and practitioners alike, fostering a deeper understanding of the potential benefits, applications, and challenges involved in utilizing composite hydrogels for wound treatment.

The Feasibility and Outcome of Integra® Bilayer Matrix in the Reconstruction of Oral Cavity Defects

OBJECTIVE

To evaluate the feasibility, safety, and failure rate of Integra® Bilayer Wound Matrix (Integra) in the reconstruction of oral cavity defects.

STUDY DESIGN

Retrospective cohort study.

SETTING

All study information was collected from a single academic tertiary care hospital.

METHODS

Subjects included adult patients who underwent oral cavity resection and immediate subsequent reconstruction with Integra® Bilayer Wound Matrix at MD Anderson Cancer Center between the years 2015 and 2020. The following variables were collected: patient's demographics, comorbidities, disease stage, treatment and reconstruction modalities, and surgical outcome from the medical records. Statistical analysis included distribution analysis for all collected parameters and Pearson's χ2 tests to find correlation between variables and take rate of Integra.

RESULTS

Eighty-three patients underwent reconstruction with Integra® Bilayer Wound Matrix dressing. Average age was 66 years old. Thirty-nine patients (47%) had history of previous resections for oral cavity tumors. Fourteen patients (17%) had history of radiation therapy to the Head and Neck region. Most common pathology was invasive squamous cell carcinoma (75%) followed by dysplasia (12%). Complete wound healing with good cellular integration occurred in 83 patients (96%) with only 3 failures requiring additional surgery. Reconstruction of mandibulectomy defects was associated with increased risk of dehiscence and bone exposure (0.66, P = .03).

CONCLUSION

This study shows promising results with high take rate of Integra® Bilayer Wound Matrix dressing in the reconstruction of various oral cavity defects. We encourage surgeons to adopt this technique as a viable and versatile option into the reconstruction ladder of oral cavity defects.

Using Integra for Reconstruction of Facial Defects after Mohs Micrographic Surgery

Background

We aimed to identify how Integra bilayer wound matrix has expanded facial reconstruction options after Mohs surgery due to its reliability in both single- and dual-stage reconstruction.

Methods

A retrospective review of patients undergoing Mohs surgery and alloplastic facial reconstruction with Integra between 2012 and 2022 was performed. Patients who underwent single-stage reconstruction and dual-stage reconstruction with skin graft with at least 90 days of follow-up were included.

Results

One hundred thirty patients with a median age of 76 years were included. Basal cell carcinoma was the most common malignancy (39%). One hundred forty-two lesions were treated and reconstructed same-day with Integra. Lesions most commonly involved the nose (34%) and forehead (22%). The mean postoperative defect size was 26.9 cm2. An estimated 45.5% (n = 60) of defect sites underwent single-stage reconstruction with healing by secondary intention, whereas 54.5% (n = 72) underwent dual-stage reconstruction with skin graft. Integra success rate was 90.2%. Average time to re-epithelialization was 32.2 + 7.3 days. Average time to repigmentation was 169.5 + 14.6 days. The complication rate was 12.8% (n = 17), with 12 undergoing debridement, three needing new Integra graft, and seven needing new skin grafts. Average size for successful healing without complication was 26.6 cm2. Nineteen sites (13.2%) underwent aesthetic improvement procedures, with the majority occurring after dual-stage reconstruction (n = 13).

Conclusions

Integra is a reliable outpatient reconstructive option for facial Mohs defects that can increase the threshold for autologous tissue harvesting and successfully reconstruct large defects of 26.6 cm2 on average with low complication and reoperation rates.

Engineered dermis loaded with confining forces promotes full-thickness wound healing by enhancing vascularisation and epithelialisation

Tissue-engineered skin is ideal for clinical wound repair. Restoration of skin tissue defects using tissue-engineered skin remains a challenge owing to insufficient vascularisation. In our previous study, we developed a 3D bioprinted model with confined force loading and demonstrated that the confined force can affect vascular branching, which is regulated by the YAP signalling pathway. The mechanical properties of the model must be optimised to suture the wound edges. In this study, we explored the ability of a GelMA-HAMA-fibrin scaffold to support the confined forces created by 3D bioprinting and promote vascularisation and wound healing. The shape of the GelMA-HAMA-fibrin scaffold containing 3% GelMA was affected by the confined forces produced by the embedded cells. The GelMA-HAMA-fibrin scaffold was easy to print, had optimal mechanical properties, and was biocompatible. The constructs were successfully sutured together after 14 d of culture. Scaffolds seeded with cells were transplanted into skin tissue defects in nude mice, demonstrating that the cell-seeded GelMA-HAMA-fibrin scaffold, under confined force loading, promoted neovascularisation and wound restoration by enhancing blood vessel connections, creating a patterned surface, growth factors, and collagen deposition. These results provide further insights into the production of hydrogel composite materials as tissue-engineered scaffolds under an internal mechanical load that can enhance vascularisation and offer new treatment methods for wound healing. STATEMENT OF SIGNIFICANCE: Tissue-engineered skin is ideal for use in clinical wound repair. However, treatment of tissue defects using synthetic scaffolds remains challenging, mainly due to slow and insufficient vascularization. Our previous study developed a 3D bioprinted model with confined force loading, and demonstrated that confined force can affect vascular branching regulated by the YAP signal pathway. The mechanical properties of the construct need to be optimized for suturing to the edges of wounds. Here, we investigated the ability of a GelMA-HAMA-fibrin scaffold to support the confined forces created by 3D bioprinting and promote vascularization in vitro and wound healing in vivo. Our findings provide new insight into the development of degradable macroporous composite materials with mechanical stimulation as tissue-engineered scaffolds with enhanced vascularization, and also provide new treatment options for wound healing.

Artificial Skin Therapies; Strategy for Product Development

Significance: Tissue-engineered artificial skin for clinical reconstruction can be regarded as an established practice. Bi-layered skin equivalents are available as established allogenic or autologous therapy, and various acellular skin replacements can support tissue repair. Moreover, there is considerable commonality between the skin and other soft tissue reconstruction products. This article presents an attempt to create a comprehensive global landscape review of advanced replacement materials and associated strategies for skin and soft tissue reconstruction. Recent Advances: There has been rapid growth in the number of commercial and pre-commercial products over the past decade. In this survey, 263 base products for advanced skin therapy have been identified, across 8 therapeutic categories, giving over 350 products in total. The largest market is in the United States, followed by the E.U. zone. However, despite these advances, and the investment of resources in each product development, there are key issues concerning the clinical efficacy, cost-benefit of products, and clinical impact. Each therapeutic strategy has relative merits and limitations. Critical Issues: A critical consideration in developing and evaluating products is the therapeutic modality, associated regulatory processes, and the potential for clinical adoption geographically, determined by regulatory territory, intellectual property, and commercial distribution factors. The survey identifies an opportunity for developments that improve basic efficacy or cost-benefit. Future Directions: The economic pressures on health care systems, compounded by the demands of our increasingly ageing population, and the imperative to distribute effective health care, create an urgent global need for effective and affordable products.

Short- and Long-term Outcomes of an Acellular Dermal Substitute versus Standard of Care in Burns and Reconstructions: A Phase I/II Intrapatient Randomized Controlled Trial

OBJECTIVE

Dermal substitutes promote dermal regeneration and improve scar quality, but knowledge gaps remain regarding their efficacy and indications for use. The authors investigated the safety and short- and long-term efficacy of an acellular dermal substitute in patients with full-thickness wounds.

METHODS

This intrapatient randomized controlled, open-label, phase I (safety) and phase II (efficacy) study compared treatment with Novomaix (Matricel GmbH), a dermal collagen/elastin-based scaffold, with split-thickness skin graft (STSG) only. The primary safety outcome was graft take at 5 to 7 days postsurgery. Postsurgical scar quality was assessed by measuring elasticity, color, and scores on the Patient and Observer Scar Assessment Scale at 3 months, 12 months, and 6 years.

RESULTS

Twenty-five patients were included, of which 24 received treatment allocation. Graft take and wound healing were statistically significantly lower/delayed in the dermal matrix group compared with STSG alone (P < .004). Serious adverse events were delayed epithelialization in four dermal matrix and three STSG study areas. At 12 months postsurgery, skin extension (P = .034) and elasticity (P = .036) were better for the dermal matrix group compared with the group receiving STSG alone. Other scar quality parameters at 12 months and 6 years did not differ between treatment arms.

CONCLUSIONS

The dermal substitute was a safe treatment modality for full-thickness wounds. Compared with STSG alone, time to wound healing was slightly increased. Nevertheless, scar quality at 12 months seemed somewhat improved in the wounds treated with the dermal substitute, indicative of enhanced scar maturation. In the long term, final scar quality was similar for both treatment modalities.

Cutaneous Cell Therapy Manufacturing Timeframe Rationalization: Allogeneic Off-the-Freezer Fibroblasts for Dermo-Epidermal Combined Preparations (DE-FE002-SK2) in Burn Care

Autologous cell therapy manufacturing timeframes constitute bottlenecks in clinical management pathways of severe burn patients. While effective temporary wound coverings exist for high-TBSA burns, any means to shorten the time-to-treatment with cytotherapeutic skin grafts could provide substantial therapeutic benefits. This study aimed to establish proofs-of-concept for a novel combinational cytotherapeutic construct (autologous/allogeneic DE-FE002-SK2 full dermo-epidermal graft) designed for significant cutaneous cell therapy manufacturing timeframe rationalization. Process development was based on several decades (four for autologous protocols, three for allogeneic protocols) of in-house clinical experience in cutaneous cytotherapies. Clinical grade dermal progenitor fibroblasts (standardized FE002-SK2 cell source) were used as off-the-freezer substrates in novel autologous/allogeneic dermo-epidermal bilayer sheets. Under vitamin C stimulation, FE002-SK2 primary progenitor fibroblasts rapidly produced robust allogeneic dermal templates, allowing patient keratinocyte attachment in co-culture. Notably, FE002-SK2 primary progenitor fibroblasts significantly outperformed patient fibroblasts for collagen deposition. An ex vivo de-epidermalized dermis model was used to demonstrate the efficient DE-FE002-SK2 construct bio-adhesion properties. Importantly, the presented DE-FE002-SK2 manufacturing process decreased clinical lot production timeframes from 6-8 weeks (standard autologous combined cytotherapies) to 2-3 weeks. Overall, these findings bear the potential to significantly optimize burn patient clinical pathways (for rapid wound closure and enhanced tissue healing quality) by combining extensively clinically proven cutaneous cell-based technologies.

Skin substitutes as treatment for chronic wounds: current and future directions

Chronic wounds such as diabetic foot ulcers and venous leg ulcers place a significant burden on the healthcare system and in some cases, have 5-year mortality rates comparable to cancer. They negatively impact patients' quality of life due to pain, odor, decreased mobility, and social isolation. Skin substitutes are an advanced therapy recommended for wounds that fail to show decrease in size with standard care. The choice of substitute used should be based on evidence, which often differs based on wound etiology. There are more than 75 skin substitutes currently available, and that number is rising. In this review, we discuss current management and future directions of chronic wounds while providing a review of available randomized control trial data for various skin substitutes.

Personalised burn treatment: bedside electrospun nanofibre scaffold with cultured autologous keratinocytes: a case study

Nearly four decades after cultured epidermal autografts (CEA) were first used for the treatment of extensive burn wounds, the current gold standard treatment remains grafting healthy autologous skin from a donor site to the damaged areas, with current skin substitutes limited in their clinical use. We propose a novel treatment approach, using an electrospun polymer nanofibrous matrix (EPNM) applied on-site directly on the CEA-grafted areas. In addition, we propose a personalised treatment on hard-to-heal areas, in which we spray suspended autologous keratinocytes integrated with 3D EPNM applied on-site, directly onto the wound bed. This method enables the coverage of larger wound areas than possible with CEA. We present the case of a 26-year-old male patient with full-thickness burns covering 98% of his total body surface area (TBSA). We were able to show that this treatment approach resulted in good re-epithelialisation, seen as early as seven days post CEA grafting, with complete wound closure within three weeks, and to a lesser extent in areas treated with cell spraying. Moreover, in vitro experiments confirmed the feasibility of using keratinocytes embedded within the EPNM: cell and culture viability, identity, purity and potency were determined. These experiments show that the skin cells are viable and can proliferate within the EPNM. The results presented are of a promising novel strategy for the development of personalised wound treatment, integrating on-the-spot 'printed' EPNM with autologous skin cells, which will be applied at the bedside, over deep dermal wounds, to accelerate healing time and wound closure.

Modified gelatin hydrogel nonwoven fabrics (Genocel) as a skin substitute in murine skin defects

Introduction

From previous research, an emerging material composed of gelatin hydrogel nonwoven fabric (Genocel) has shown potential as a skin substitute, by improving neovascularization promotion in the early phase of wound healing. However, Genocel was inferior in terms of granulation formation compared to Pelnac. To solve this problem, we modified the manufacturing process of Genocel to reduce its water content, extend the degradation time (Genocel-L), and evaluate its healing process as a skin substitute.

Methods

Genocel with a low water content (Genocel-L) was prepared and the difference in water content compared to that of the conventional Genocel was confirmed. Degradation tests were performed using collagenase and compared among Genocel-L, Genocel, and Pelnac sheets. In the in vivo study, sheets of Genocel-L or Pelnac were applied to skin defects created on the backs of C57BL/6JJcl mice. On days 7, 14, and 21, the remaining wound area was evaluated and specimens were harvested for Hematoxylin and Eosin, Azan, anti-CD31, CD68, and CD163 staining to assess neoepithelialization, granulation tissue, capillary formation, and macrophage infiltration.

Results

Genocel-L had a lower water content than the conventional Genocel and a slower degradation than Genocel and Pelnac. In the in vivo experiment, no significant differences were observed between Genocel-L and Pelnac in relation to the wound area, neoepithelium length, granulation formation, and the number of newly formed capillaries. The area of newly formed capillaries in the Pelnac group was significantly larger than that in the Genocel-L group on day 21 (p < 0.05). Regarding macrophage infiltration, significantly more M2 macrophages were induced in the Pelnac group on days 14 and 21, and the M2 ratio was larger in the Pelnac group (p < 0.05) during the entire process.

Conclusions

Genocel-L has a lower water content and slower degradation rate than the conventional Genocel. Genocel-L had equivalent efficacy as a skin substitute to Pelnac, and can therefore be considered feasible for use as a skin substitute. However, a manufacturing method that can further modify Genocel-L is required to recover its early angiogenic potential.

Human disease models in drug development

Biomedical research is undergoing a paradigm shift towards approaches centred on human disease models owing to the notoriously high failure rates of the current drug development process. Major drivers for this transition are the limitations of animal models, which, despite remaining the gold standard in basic and preclinical research, suffer from interspecies differences and poor prediction of human physiological and pathological conditions. To bridge this translational gap, bioengineered human disease models with high clinical mimicry are being developed. In this Review, we discuss preclinical and clinical studies that benefited from these models, focusing on organoids, bioengineered tissue models and organs-on-chips. Furthermore, we provide a high-level design framework to facilitate clinical translation and accelerate drug development using bioengineered human disease models.

Preclinical study models of psoriasis: State-of-the-art techniques for testing pharmaceutical products in animal and nonanimal models

Local and systemic treatments exist for psoriasis, but none can do more than control its symptoms because of its numerous unknown mechanisms. The lack of validated testing models or a defined psoriatic phenotypic profile hinders antipsoriatic drug development. Despite their intricacy, immune-mediated diseases have no improved and precise treatment. The treatment actions may now be predicted for psoriasis and other chronic hyperproliferative skin illnesses using animal models. Their findings confirmed that a psoriasis animal model could mimic a few disease conditions. However, their ethical approval concerns and inability to resemble human psoriasis rightly offer to look for more alternatives. Hence, in this article, we have reported various cutting-edge techniques for the preclinical testing of pharmaceutical products for the treatment of psoriasis.

Accelular nanofibrous bilayer scaffold intrapenetrated with polydopamine network and implemented into a full-thickness wound of a white-pig model affects inflammation and healing process

Treatment of complete loss of skin thickness requires expensive cellular materials and limited skin grafts used as temporary coverage. This paper presents an acellular bilayer scaffold modified with polydopamine (PDA), which is designed to mimic a missing dermis and a basement membrane (BM). The alternate dermis is made from freeze-dried collagen and chitosan (Coll/Chit) or collagen and a calcium salt of oxidized cellulose (Coll/CaOC). Alternate BM is made from electrospun gelatin (Gel), polycaprolactone (PCL), and CaOC. Morphological and mechanical analyzes have shown that PDA significantly improved the elasticity and strength of collagen microfibrils, which favorably affected swelling capacity and porosity. PDA significantly supported and maintained metabolic activity, proliferation, and viability of the murine fibroblast cell lines. The in vivo experiment carried out in a domestic Large white pig model resulted in the expression of pro-inflammatory cytokines in the first 1-2 weeks, giving the idea that PDA and/or CaOC trigger the early stages of inflammation. Otherwise, in later stages, PDA caused a reduction in inflammation with the expression of the anti-inflammatory molecule IL10 and the transforming growth factor β (TGFβ1), which could support the formation of fibroblasts. Similarities in treatment with native porcine skin suggested that the bilayer can be used as an implant for full-thickness skin wounds and thus eliminate the use of skin grafts.

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.

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

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

A single-stage bilayered skin reconstruction using Glyaderm® as an acellular dermal regeneration template results in improved scar quality: an intra-individual randomized controlled trial

Background

Absence of almost the entire reticular dermal layer is inherent to the use of autologous split-thickness skin grafting (STSG) to close full-thickness wounds, often resulting in hypertrophic scars and contractures. Many dermal substitutes have been developed, but unfortunately most have varying results in terms of cosmetic and/or functional improvement as well as patient satisfaction, in addition to high costs. Bilayered skin reconstruction using the human-derived glycerolized acellular dermis (Glyaderm®) has been reported to result in significantly improved scar quality using a two-step procedure. Unlike the necessary two-step procedure for most commercially available dermal substitutes, in this study we aimed to investigate the use of Glyaderm® in a more cost-effective single-stage engrafting. This is a method which, if autografts are available, is preferred by the majority of surgeons given the reduction in costs, hospitalization time and infection rate.

Methods

A prospective, randomized, controlled, intra-individual, single-blinded study was performed, investigating the simultaneous application of Glyaderm® and STSG vs. STSG alone in full-thickness burns or comparable deep skin defects. During the acute phase, bacterial load, graft take and time to wound closure were assessed and were the primary outcomes. Aesthetic and functional results (secondary outcomes) were evaluated at 3, 6, 9 and 12 months follow-up using subjective and objective scar measurement tools. Biopsies for histological analysis were taken at 3 and 12 months.

Results

A total of 66 patients representing 82 wound comparisons were included. Graft take (>95%), pain management and healing time were comparable in both groups. At 1 year follow-up, the overall Patient and Observer Scar Assessment Scale assessed by the patient was significantly in favour of sites where Glyaderm® was used. Not infrequently, patients attributed this difference to improved skin sensation. Histological analysis showed the presence of a well-formed neodermis, with donor elastin present for up to 12 months.

Conclusions

A single-stage bilayered reconstruction with Glyaderm® and STSG results in optimal graft take without loss of Glyaderm® nor the overlaying autografts due to infection. The presence of elastin in the neodermis was demonstrated during long-term follow-up in all but one patient, which is a crucial factor contributing to the significantly improved overall scar quality as evaluated by the blinded patients.

Trial registration

The trial was registered on clinicaltrials.gov and received the following registration code: NCT01033604.

3D bioprinting of an implantable xeno-free vascularized human skin graft

Bioengineered tissues or organs produced using matrix proteins or components derived from xenogeneic sources pose risks of allergic responses, immune rejection, or even autoimmunity. Here, we report successful xeno-free isolation, expansion, and cryopreservation of human endothelial cells (EC), fibroblasts (FBs), pericytes (PCs), and keratinocytes (KCs). We further demonstrate the bioprinting of a human skin substitute with a dermal layer containing xeno-free cultured human EC, FBs, and PCs in a xeno-free bioink containing human collagen type I and fibronectin layered in a biocompatible polyglycolic acid mesh and subsequently seeded with xeno-free human KCs to form an epidermal layer. Following implantation of such bilayered skin grafts on the dorsum of immunodeficient mice, KCs form a mature stratified epidermis with rete ridge-like structures. The ECs and PCs form human EC-lined perfused microvessels within 2 weeks after implantation, preventing graft necrosis, and eliciting further perfusion of the graft by angiogenic host microvessels. As proof-of-concept, we generated 12 individual grafts using a single donor of all four cell types. In summary, we describe the fabrication of a bioprinted vascularized bilayered skin substitute under completely xeno-free culture conditions demonstrating feasibility of a xeno-free approach to complex tissue engineering.

Hyaluronic acid-based nanofibers: Electrospun synthesis and their medical applications; recent developments and future perspective

Hyaluronan is a biodegradable, biopolymer that represents a major part of the extracellular matrix and has the potential to be fabricated in a fibrous form conjugated with other polymers via electrospinning. Unique physicochemical features such as viscoelasticity, conductivity, and biological activity mainly affected by molecular weight attracted the attention of biomedical researchers to utilize hyaluronan for designing novel HA-based nano-devices. Particularly HA-based nanofibers get focused on a diverse range of applications in medical like tissue implants for regeneration of damaged tissue or organ repair, wound dressings, and drug delivery carriers to treat various disorders. Currently, electrospinning represents an effective available method for designing highly porous, 3D, HA-based nanofibers with features similar to that of the extra-cellular matrix making them a promising candidate for designing advanced regenerative medicines. This review highlights the structural and physicochemical features of HA, recently cited protocols in literature for HA production via microbial fermentation with particular focus on electrospun fabrication of HA-based nanofibers and parameters affecting its synthesis, current progress in medical applications of these electrospun HA-based nanofibers, their limitations and future perspective about the potential of these HA-based nanofibers in medical field.

Comparison of Wound Healing Effect of Skin Micrograft Impregnated into Two Kinds of Artificial Dermis in a Murine Wound Model

A micrograft (MG) suspension produced by the Rigenera protocol has been used to stimulate tissue regeneration. Recently, a combination therapy of an artificial dermis and skin MG has been used to promote angiogenesis and granulation tissue formation in the artificial dermis. There are no reports comparing the differences in MG impregnation efficiency between different artificial dermis products. Therefore, we compared the impregnation of skin MG in Pelnac Gplus and Integra.

Methods

Skin MG was prepared from the skin of C57BL/6JJcl mice using Rigeneracons and administered onto Pelnac Gplus and Integra sheets. The amount of MG suspension impregnated in Pelnac Gplus and Integra was evaluated. Pelnac Gplus and Integra sheets combined with MG were applied to murine defects, and wound area, neoepithelium length, granulation tissue formation, and newly formed capillaries were compared with the control groups on days 7 and 14.

Results

The weight percentage of the MG absorbed by Pelnac Gplus and Integra was 88.8% ± 3.5% and 28.2% ± 7.0%, respectively (P < 0.05). In the in vivo experiment, the area of newly formed granulation tissue and both the number and area of newly formed capillaries in the PelnacG + MG group were significantly larger than those in the control group at 14 days after implantation (P < 0.05).

Conclusions

Skin MG was successfully impregnated into Pelnac Gplus by simple administration but not into Integra. Administration of skin MG into the Pelnac Gplus promoted granulation formation and angiogenesis. Pelnac Gplus was more suitable than Integra in the combination therapy.

In Vivo Comparison of Synthetic Macroporous Filamentous and Sponge-like Skin Substitute Matrices Reveals Morphometric Features of the Foreign Body Reaction According to 3D Biomaterial Designs

Synthetic macroporous biomaterials are widely used in the field of skin tissue engineering to mimic membrane functions of the native dermis. Biomaterial designs can be subclassified with respect to their shape in fibrous designs, namely fibers, meshes or fleeces, respectively, and porous designs, such as sponges and foams. However, synthetic matrices often have limitations regarding unfavorable foreign body responses (FBRs). Severe FBRs can result in unfavorable disintegration and rejection of an implant, whereas mild FBRs can lead to an acceptable integration of a biomaterial. In this context, comparative in vivo studies of different three-dimensional (3D) matrix designs are rare. Especially, the differences regarding FBRs between synthetically derived filamentous fleeces and sponge-like constructs are unknown. In the present study, the FBRs on two 3D matrix designs were explored after 25 days of subcutaneous implantation in a porcine model. Cellular reactions were quantified histopathologically to investigate in which way the FBR is influenced by the biomaterial architecture. Our results show that FBR metrics (polymorph-nucleated cells and fibrotic reactions) were significantly affected according to the matrix designs. Our findings contribute to a better understanding of the 3D matrix tissue interactions and can be useful for future developments of synthetically derived skin substitute biomaterials.

An Effective Method for Decellularization of Human Foreskin: Implications for Skin Regeneration in Small Wounds

OBJECTIVE

Acellular matrices of different allogeneic or xenogeneic origins are widely used as structural scaffolds in regenerative medicine. The main goal of this research was to optimize a method for decellularization of foreskin for skin regeneration in small wounds.

MATERIALS AND METHODS

In this experimental study, the dermal layers of foreskin were divided into two sections and subjected to two different decellularization methods: the sodium dodecyl sulfate method (SDS-M), and our optimized foreskin decellularization method (OFD-M). A combination of non-ionic detergents and SDS were used to decellularize the foreskin in OFD-M. The histological, morphological, and biomechanical properties of both methods were compared. In addition, human umbilical cord mesenchymal stem cells (hucMSCs) were isolated, and the biocompatibility and recellularization of both scaffolds by hucMSC were subsequently determined.

RESULTS

We observed that OFD-M is an appropriate approach for successful removal of cellular components from the foreskin tissue, without physical disturbance to the acellular matrix. In comparison to SDS-M, this new bioscaffold possesses a fine network containing a high amount of collagen fibers and glycosaminoglycans (GAG) (P≤0.03), is biocompatible and harmless for hucMSC (viability 91.7%), and exhibits a relatively high tensile strength.

CONCLUSION

We found that the extracellular matrix (ECM) structural integrity, the main ECM components, and the mechanical properties of the foreskin are well maintained after applying the OFD-M decellularization technique, indicating that the resulting scaffold would be a suitable platform for culturing MSC for skin grafting in small wounds.

Recent advances in bioprinting using silk protein-based bioinks

3D printing has experienced swift growth for biological applications in the field of regenerative medicine and tissue engineering. Essential features of bioprinting include determining the appropriate bioink, printing speed mechanics, and print resolution while also maintaining cytocompatibility. However, the scarcity of bioinks that provide printing and print properties and cell support remains a limitation. Silk Fibroin (SF) displays exceptional features and versatility for inks and shows the potential to print complex structures with tunable mechanical properties, degradation rates, and cytocompatibility. Here we summarize recent advances and needs with the use of SF protein from Bombyx mori silkworm as a bioink, including crosslinking methods for extrusion bioprinting using SF and the maintenance of cell viability during and post bioprinting. Additionally, we discuss how encapsulated cells within these SF-based 3D bioprinted constructs are differentiated into various lineages such as skin, cartilage, and bone to expedite tissue regeneration. We then shift the focus towards SF-based 3D printing applications, including magnetically decorated hydrogels, in situ bioprinting, and a next-generation 4D bioprinting approach. Future perspectives on improvements in printing strategies and the use of multicomponent bioinks to improve print fidelity are also discussed.

Clinical observation on healing of tarsal plate defect after reconstruction with xenogeneic acellular dermal matrix

Objective

To evaluate the safety, function, and cosmetic outcome of eyelid reconstruction using a xenogeneic acellular dermal matrix as a tarsal plate replacement in the repair of 50 to 100% eyelid defects following excision of large malignant tumours.

Methods

A retrospective, non-comparative, interventional study of 21 eyes was performed over 26 months. Fourteen patients were female and seven were male. In all cases, a xenogeneic acellular dermal matrix was used for total or subtotal replacement of the tarsal plate. The central vertical height of the palpebral fissure was measured immediately after eyelid margin incision and at 1 and 6 months postoperatively.

Results

In patients who underwent surgery, the mean palpebral fissure height (PFH) was not significantly different between immediately and 1 month after incision (8.10 ± 0.562 mm vs 8.17 ± 0.577 mm, respectively; P > 0.05). After 6 months, PFH was 8.26 ± 0.605 mm, which was significantly different from that immediately after incision (P < 0.05). After 6 months of follow-up, all patients had a good aesthetic appearance after eyelid reconstruction, with no obvious graft dissolution or rejection, normal eyelid activity, and normal opening, closing, and lifting function. None of the 21 patients experienced tumour recurrence during postoperative follow-up.

Conclusion

The xenogeneic acellular dermal matrix was a successful tarsal plate replacement. This material is readily available, and a second surgical site is avoided. The xenogeneic acellular dermal matrix is considered a promising alternative material for tarsal replacement in future generations.

A photocrosslinking antibacterial decellularized matrix hydrogel with nanofiber for cutaneous wound healing

ddECMMA is the methacrylating product of decellularized dermal extracellular matrix with biological signals and capable of photocrosslinking. Thiolated chitosan (TCS) is an effective antibacterial component. PCLPBA is a kind of plasma-treated polycaprolactone nanofiber dispersions (PCLP) that regulates macrophage polarization and promotes angiogenesis. In this study, we obtained ddECMMA via methacrylation reaction. TCS was prepared by reaction between chitosan and thioglycolic acid. PCLPBA was fabricated via reaction between PCLP and 3-buten-1-amine. TCS and PCLPBA were mixed in ddECMMA solution and photocrosslinked to form DTP4 hydrogel. The hydrogel showed rapid gelation, good mechanical strength, antibacterial and antioxidant properties. When it was cocultured with NIH 3T3 cells, the cells showed good morphology and proliferation rate. After applying it to the full-thickness cutaneous wound, wounds almost healed in 2 weeks via re-epithelialization and neovascularization with negligible scar tissue. The results indicate that DTP4 hydrogel is a promising candidate for clinic skin wound healing.

Knowledge Domain and Hotspots Predict Concerning Electroactive Biomaterials Applied in Tissue Engineering: A Bibliometric and Visualized Analysis From 2011 to 2021

Objective: Electroactive biomaterials used in tissue engineering have been extensively studied. Electroactive biomaterials have unique potential advantages in cell culture and tissue regeneration, which have attracted the attention of medical researchers worldwide. Therefore, it is important to understand the global scientific output regarding this topic. An analysis of publications on electroactive biomaterials used in tissue engineering over the past decade was performed, and the results were summarised to track the current hotspots and highlight future directions.

Methods: Globally relevant publications on electroactive biomaterials used in tissue engineering between 2011 and 2021 were extracted from the Web of Science database. The VOSviewer software and CiteSpace were employed to visualise and predict trends in research on the topic.

Results: A total of 3,374 publications were screened. China contributed the largest number of publications (995) and citations (1581.95, actual value ×0.05). The United States achieved the highest H-index (440 actual values ×0.05). The journal Materials Science &amp; Engineering C-materials for Biological Applications (IF = 7.328) published the most studies on this topic (150). The Chinese Academy of Science had the largest number of publications (107) among all institutions. The publication titled Nanotechnological strategies for engineering complex tissues by Dir, T of the United States had the highest citation frequency (985 times). Regarding the function of electroactive materials, the keyword “sensors” emerged in recent years. Regarding the characterisation of electroactive materials, the keyword “water contact angle” appeared lately. Regarding electroactive materials in nerve and cardiac tissue engineering, the keywords “silk fibroin and conductive hydrogel” appeared recently. Regarding the application of electroactive materials in bone tissue engineering, the keyword “angiogenesis” emerged in recent years. The current research trend indicates that although new functional materials are constantly being developed, attention should also be paid to their application and transformation in tissue engineering.

Conclusion: The number of publications on electroactive biomaterials used in tissue engineering is expected to increase in the future. Topics like sensors, water contact angle, angiogenesis, silk fibroin, and conductive hydrogels are expected to be the focuses of research in the future; attention should also be paid to the application and transformation of electroactive materials, particularly bone tissue engineering. Moreover, further development of the field requires joint efforts from all disciplines.

Technical Refinements with the Use of Biologic Healing Agents

Soft tissue defects resulting from trauma, vascular disease, burns, and postoncologic resections require reconstructive surgery for appropriate wound coverage and support. Dermal substitutes have been applied to a vast array of reconstructive settings across nearly all anatomical areas with demonstrable success. However, they require meticulous handling and operative technical expertise to optimize management of these soft tissue defects. In this review, we will address three dermal substitutes, their operative techniques, and their surgical applications.

Use of a purified reconstituted bilayer matrix in the management of chronic diabetic foot ulcers improves patient outcomes vs standard of care: Results of a prospective randomised controlled multi-centre clinical trial

Diabetic foot infections continue to be a major challenge for health care delivery systems. Following encouraging results from a pilot study using a novel purified reconstituted bilayer matrix (PRBM) to treat chronic diabetic foot ulcers (DFUs), we designed a prospective, multi‐centre randomised trial comparing outcomes of PRBM at 12 weeks compared with a standard of care (SOC) using a collagen alginate dressing. The primary endpoint was percentage of wounds closed after 12 weeks. Secondary outcomes included assessments of complications, healing time, quality of life, and cost to closure. Forty patients were included in an intent‐to‐treat (ITT) and per‐protocol (PP) analysis, with 39 completing the study protocol (n = 19 PRBM, n = 20 SOC). Wounds treated with PRBM were significantly more likely to close than wounds treated with SOC (ITT: 85% vs 30%, P = .0004, PP: 94% vs 30% P = .00008), healed significantly faster (mean 37 days vs 67 days for SOC, P = .002), and achieved a mean wound area reduction within 12 weeks of 96% vs 8.9% for SOC. No adverse events (AEs) directly related to PRBM treatment were reported. Mean PRBM cost of healing was $1731. Use of PRBM was safe and effective for treatment of chronic DFUs.

Cell secretomes for wound healing and tissue regeneration: Next generation acellular based tissue engineered products

Wound represents a significant socioeconomic burden for both affected individuals and as a whole healthcare system. Accordingly, stem cells have garnered attention due to their differentiation capacity and ability to aid tissue regeneration by releasing biologically active molecules, found in the cells' cultivated medium which known as conditioned medium (CM) or secretomes. This acellular approach provides a huge advantage over conventional treatment options, which are mainly used cellular treatment at wound closure. Interestingly, the secretomes contained the cell-secreted proteins such as growth factors, cytokines, chemokines, extracellular matrix (ECM), and small molecules including metabolites, microvesicles, and exosomes. This review aims to provide a general view on secretomes and how it is proven to have great potential in accelerating wound healing. Utilizing the use of secretomes with its secreted proteins and suitable biomaterials for fabrications of acellular skin substitutes can be promising in treating skin loss and accelerate the healing process.

Wound healing properties of a fibrin-based dermal replacement scaffold

When serious cutaneous injury occurs, the innate wound healing process attempts to restore the skin's appearance and function. Wound healing outcome is affected by factors such as contraction, revascularisation, regeneration versus fibrosis and re-epithelialisation and is also strongly influenced by the pattern and extent of damage to the dermal layer. Dermal replacement scaffolds have been designed to substitute for lost tissue, provide a structure to promote dermal regeneration, and aid skin grafting, resulting in a superior healing outcome. In this study the wound healing properties of a novel fibrin-alginate dermal scaffold were assessed in the porcine wound healing model and also compared to two widely used dermal scaffolds and grafting alone. The fibrin-alginate scaffold, unlike the other scaffolds tested, is not used in combination with an overlying skin graft. Fibrin scaffold treated wounds showed increased, sustained superficial blood flow and reduced contraction during early healing while showing comparable wound closure, re-epithelialisation and final wound outcome to other treatments. The increase in early wound vascularisation coupled with a decrease in contraction and no requirement for a skin graft suggest that the fibrin-based scaffold could provide an effective, distinctive treatment option to improve healing outcomes in human patients.

Information and Scientific Impact of Advanced Therapies in the Age of Mass Media: Altmetrics-Based Analysis of Tissue Engineering

BACKGROUND

Tissue engineering (TE) constitutes a multidisciplinary field aiming to construct artificial tissues to regenerate end-stage organs. Its development has taken place since the last decade of the 20th century, entailing a clinical revolution. TE research groups have worked and shared relevant information in the mass media era. Thus, it would be interesting to study the online dimension of TE research and to compare it with traditional measures of scientific impact.

OBJECTIVE

The objective of this study was to evaluate the online dimension of TE documents from 2012 to 2018 using metadata obtained from the Web of Science (WoS) and Altmetric and to develop a prediction equation for the impact of TE documents from altmetric scores.

METHODS

We analyzed 10,112 TE documents through descriptive and statistical methods. First, the TE temporal evolution was exposed for WoS and 15 online platforms (news, blogs, policy, Twitter, patents, peer review, Weibo, Facebook, Wikipedia, Google, Reddit, F1000, Q&A, video, and Mendeley Readers). The 10 most cited TE original articles were ranked according to the normalized WoS citations and the normalized Altmetric Attention Score. Second, to better comprehend the TE online framework, correlation and factor analyses were performed based on the suitable results previously obtained for the Bartlett sphericity and Kaiser-Meyer-Olkin tests. Finally, the linear regression model was applied to elucidate the relation between academics and online media and to construct a prediction equation for TE from altmetrics data.

RESULTS

TE dynamic shows an upward trend in WoS citations, Twitter, Mendeley Readers, and Altmetric Scores. However, WoS and Altmetric rankings for the most cited documents clearly differ. When compared, the best correlation results were obtained for Mendeley Readers and WoS (ρ=0.71). In addition, the factor analysis identified 6 factors that could explain the previously observed differences between academic institutions and the online platforms evaluated. At this point, the mathematical model constructed is able to predict and explain more than 40% of TE WoS citations from Altmetric scores.

CONCLUSIONS

Scientific information related to the construction of bioartificial tissues increasingly reaches society through different online media. Because the focus of TE research importantly differs when the academic institutions and online platforms are compared, basic and clinical research groups, academic institutions, and health politicians should make a coordinated effort toward the design and implementation of adequate strategies for information diffusion and population health education.

Microvascular fragments in microcirculation research and regenerative medicine

Adipose tissue-derived microvascular fragments (MVF) are functional vessel segments, which rapidly reassemble into new microvasculatures under experimental in vitro and in vivo conditions. Accordingly, they have been used for many years in microcirculation research to study basic mechanisms of endothelial cell function, angiogenesis and microvascular network formation in two- and three-dimensional environments. Moreover, they serve as vascularization units for musculoskeletal regeneration and implanted biomaterials as well as for the treatment of myocardial infarction and the generation of prevascularized tissue organoids. Besides, multiple factors determining the vascularization capacity of MVF have been identified, including their tissue origin and cellular composition, the conditions for their short- and long-term storage as well as their implantation site and the general health status and medication of the recipient. The next challenging step is now the successful translation of all these promising experimental findings into clinical practice. If this succeeds, a multitude of future therapeutic applications may significantly benefit from the remarkable properties of MVF.

Conductive Polymeric-Based Electroactive Scaffolds for Tissue Engineering Applications: Current Progress and Challenges from Biomaterials and Manufacturing Perspectives

The practice of combining external stimulation therapy alongside stimuli-responsive bio-scaffolds has shown massive potential for tissue engineering applications. One promising example is the combination of electrical stimulation (ES) and electroactive scaffolds because ES could enhance cell adhesion and proliferation as well as modulating cellular specialization. Even though electroactive scaffolds have the potential to revolutionize the field of tissue engineering due to their ability to distribute ES directly to the target tissues, the development of effective electroactive scaffolds with specific properties remains a major issue in their practical uses. Conductive polymers (CPs) offer ease of modification that allows for tailoring the scaffold's various properties, making them an attractive option for conductive component in electroactive scaffolds. This review provides an up-to-date narrative of the progress of CPs-based electroactive scaffolds and the challenge of their use in various tissue engineering applications from biomaterials perspectives. The general issues with CP-based scaffolds relevant to its application as electroactive scaffolds were discussed, followed by a more specific discussion in their applications for specific tissues, including bone, nerve, skin, skeletal muscle and cardiac muscle scaffolds. Furthermore, this review also highlighted the importance of the manufacturing process relative to the scaffold's performance, with particular emphasis on additive manufacturing, and various strategies to overcome the CPs' limitations in the development of electroactive scaffolds.

Oral wound healing models and emerging regenerative therapies

Following injury, the oral mucosa undergoes complex sequences of biological healing processes to restore homeostasis. While general similarities exist, there are marked differences in the genomics and kinetics of wound healing between the oral cavity and cutaneous epithelium. The lack of successful therapy for oral mucosal wounds has influenced clinicians to explore alternative treatments and potential autotherapies to enhance intraoral healing. The present in-depth review discusses current gold standards for oral mucosal wound healing and compares endogenous factors that dictate the quality of tissue remodeling. We conducted a review of the literature on in vivo oral wound healing models and emerging regenerative therapies published during the past twenty years. Studies were evaluated by injury models, therapy interventions, and outcome measures. The success of therapeutic approaches was assessed, and research outcomes were compared based on current hallmarks of oral wound healing. By leveraging therapeutic advancements, particularly within in cell-based biomaterials and immunoregulation, there is great potential for translational therapy in oral tissue regeneration.

Bacterial Cellulose as a Potential Bio-Scaffold for Effective Re-Epithelialization Therapy

Currently, there are several therapeutic approaches available for wound injury management. However, a better understanding of the underlying mechanisms of how biomaterials affect cell behavior is needed to develop potential repair strategies. Bacterial cellulose (BC) is a bacteria-produced biopolymer with several advantageous qualities for skin tissue engineering. The aim here was to investigate BC-based scaffold on epithelial regeneration and wound healing by examining its effects on the expression of scavenger receptor-A (SR-A) and underlying macrophage behavior. Full-thickness skin wounds were generated on Sprague-Dawley rats and the healing of these wounds, with and without BC scaffolds, was examined over 14 days using Masson’s trichome staining. BC scaffolds displayed excellent in vitro biocompatibility, maintained the stemness function of cells and promoted keratinocyte differentiation of cells, which are vital in maintaining and restoring the injured epidermis. BC scaffolds also exhibited positive in vivo effects on the wound microenvironment, including improved skin extracellular matrix deposition and controlled excessive inflammation by reduction of SR-A expression. Furthermore, BC scaffold significantly enhanced epithelialization by stimulating the balance of M1/M2 macrophage re-programming for beneficial tissue repair relative to that of collagen material. These findings suggest that BC-based materials are promising products for skin injury repair.

Systems of conductive skin for power transfer in clinical applications

The primary aim of this article is to review the clinical challenges related to the supply of power in implanted left ventricular assist devices (LVADs) by means of transcutaneous drivelines. In effect of that, we present the preventive measures and post-operative protocols that are regularly employed to address the leading problem of driveline infections. Due to the lack of reliable wireless solutions for power transfer in LVADs, the development of new driveline configurations remains at the forefront of different strategies that aim to power LVADs in a less destructive manner. To this end, skin damage and breach formation around transcutaneous LVAD drivelines represent key challenges before improving the current standard of care. For this reason, we assess recent strategies on the surface functionalization of LVAD drivelines, which aim to limit the incidence of driveline infection by directing the responses of the skin tissue. Moreover, we propose a class of power transfer systems that could leverage the ability of skin tissue to effectively heal short diameter wounds. In this direction, we employed a novel method to generate thin conductive wires of controllable surface topography with the potential to minimize skin disruption and eliminate the problem of driveline infections. Our initial results suggest the viability of the small diameter wires for the investigation of new power transfer systems for LVADs. Overall, this review uniquely compiles a diverse number of topics with the aim to instigate new research ventures on the design of power transfer systems for IMDs, and specifically LVADs.

Progenitor Biological Bandages: An Authentic Swiss Tool for Safe Therapeutic Management of Burns, Ulcers, and Donor Site Grafts

Clinical experience gathered over two decades around therapeutic use of primary human dermal progenitor fibroblasts in burn patient populations has been at the forefront of regenerative medicine in Switzerland. Relative technical simplicity, ease of extensive serial multitiered banking, and high stability are major advantages of such cell types, assorted to ease of safety and traceability demonstration. Stringent optimization of cell source selection and standardization of biobanking protocols enables the safe and efficient harnessing of the considerable allogenic therapeutic potential yielded by primary progenitor cells. Swiss legal and regulatory requirements have led to the procurement of fetal tissues within a devised Fetal Progenitor Cell Transplantation Program in the Lausanne University Hospital. Proprietary nonenzymatic isolation of primary musculoskeletal cell types and subsequent establishment of progeny tiered cell banks under cGMP standards have enabled safe and effective management of acute and chronic cutaneous affections in various patient populations. Direct off-the-freezer seeding of viable dermal progenitor fibroblasts on a CE marked equine collagen scaffold is the current standard for delivery of the therapeutic biological materials to patients suffering from extensive and deep burns. Diversification in the clinical indications and delivery methods for these progenitor cells has produced excellent results for treatment of persistent ulcers, autograft donor site wounds, or chronic cutaneous affections such as eczema. Herein we describe the standard operating procedures for preparation and therapeutic deployment of the progenitor biological bandages within our translational musculoskeletal regenerative medicine program, as they are routinely used as adjuvants in our Burn Center to treat critically ailing patients.

Skin Substitutes for Adults With Diabetic Foot Ulcers and Venous Leg Ulcers: A Health Technology Assessment

BACKGROUND

Wounds may be caused in a variety of ways. Some wounds are difficult to heal, such as diabetic foot ulcers and venous leg ulcers. We conducted a health technology assessment of skin substitutes for adults with neuropathic diabetic foot ulcers and venous leg ulcers, which included an evaluation of effectiveness, safety, cost-effectiveness, the budget impact of publicly funding skin substitutes, and patient preferences and values.

METHODS

We performed a systematic literature search of the clinical evidence. We assessed the risk of bias of each included study using the Cochrane risk-of-bias tool for randomized studies (version 2), and the quality of the body of evidence according to the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group criteria. We performed a systematic economic literature search and conducted a cost-utility analysis with a 26-week time horizon from a public payer perspective. We also analyzed the budget impact of publicly funding skin substitutes in adults with diabetic foot ulcers and venous leg ulcers in Ontario. We explored the underlying values, needs, and priorities of those who have lived experience with diabetic leg ulcers and venous leg ulcers, as well as their preferences for and perceptions of skin substitutes.

RESULTS

We included 40 studies in the clinical evidence review. Adults with difficult-to-heal neuropathic diabetic foot ulcers who used dermal (GRADE: High) or multi-layered (GRADE: Moderate) skin substitutes as an adjunct to standard care were more likely to experience complete wound healing than those whose who used standard care alone. Adults with difficult-to-heal venous leg ulcers who used dermal (GRADE: Moderate) or multi-layered (GRADE: High) skin substitutes as an adjunct to standard care were more likely to experience complete wound healing than those who used standard care alone. The evidence for the effectiveness of epidermal skin substitutes was inconclusive for venous leg ulcers because of the small size of the individual studies (GRADE: Very low). We found no studies on epidermal skin substitutes for diabetic foot ulcers. We could not evaluate the safety of skin substitutes versus standard care, because the number of adverse events was either very low or zero (because sample sizes were too small).In our economic analysis, the use of skin substitutes as an adjunct to standard care was more costly and more effective than standard care alone for the treatment of difficult-to-heal diabetic foot ulcers and venous leg ulcers. For diabetic foot ulcers, the incremental cost-effectiveness ratio (ICER) of skin substitutes plus standard care compared with standard care alone was $48,242 per quality-adjusted life-year (QALY), and the cost per ulcer-free week was $158. For venous leg ulcers, the ICER was $1,868,850 per QALY, and the cost per ulcer-free week was $3,235. At the commonly used willingness-to-pay of $50,000 per QALY, the cost-effectiveness of skin substitutes plus standard care versus standard care alone was uncertain (47% probability of being cost-effective) for diabetic foot ulcers and highly unlikely (0% probability of being cost-effective) for venous leg ulcers. At the commonly used willingness-to-pay of $100,000 per QALY, the cost-effectiveness of skin substitutes plus standard care versus standard care alone was moderately likely (71% probability of cost-effectiveness) for people with diabetic foot ulcers and highly unlikely (0% probability of being cost-effective) for people with venous leg ulcers. The annual budget impact of publicly funding skin substitutes in Ontario over the next 5 years would range from an additional $0.17 million in year 1 to $1.2 million in year 5 for people with diabetic foot ulcers, and from $1 million in year 1 to $7.7 million in year 5 for people with venous leg ulcers.Direct patient engagement consisted of three participants for this assessment and 51 from previous health technology assessments that addressed interventions for diabetic foot ulcers and venous leg ulcers. Participants spoke of the negative impact on their quality of life with regard to mobility, employment, social activities, and emotional and mental health. No participants had direct experience using skin substitutes, but participants were open to this treatment option. Barriers to access included the limited use of skin substitutes across Ontario, lack of knowledge of skin substitutes among people with diabetic foot ulcers and venous leg ulcers, and cost.

CONCLUSIONS

Dermal and multi-layered skin substitutes, when used as an adjunct to standard care, were more effective than standard care alone in completely healing difficult-to-heal neuropathic diabetic foot ulcers and venous leg ulcers in adults. Using skin substitutes as an adjunct to standard care was more costly and more effective than standard care alone for the treatment of difficult-to-heal neuropathic diabetic foot ulcers and venous leg ulcers. For adults with diabetic foot ulcers, the likelihood of skin substitutes being cost-effective compared with standard care depends on the willingness to pay. The likelihood of skin substitutes being cost-effective compared with standard care is uncertain at $50,000 per QALY and moderately likely at $100,000 per QALY. For adults with venous leg ulcers, skin substitutes were highly unlikely to be cost-effective compared with standard care. We estimated that publicly funding skin substitutes in Ontario would result in additional costs of $3 million and $20 million over the next 5 years for people with diabetic foot ulcers and venous leg ulcers, respectively. The people with diabetic foot ulcers and venous leg ulcers we spoke with were open to using skin substitutes as a treatment option.