Advances in keratinocyte delivery in burn wound care

High-Speed Fluorescence Imaging Corroborates Biological Data on the Influence of Different Nozzle Types on Cell Spray Viability and Formation

Treating severe dermal disruptions often presents significant challenges. Recent advancements have explored biological cell sprays as a promising treatment, but their success hinges on efficient cell delivery and complete wound coverage. This requires a good spray distribution with a small droplet size, high particle number, and ample surface coverage. The type of nozzle used with the spray device can impact these parameters. To evaluate the influence of different nozzles on spray characteristics, we compared air-assisted and unassisted nozzles. The unassisted nozzle displayed small particle size, high particle number, good overall coverage, high cell viability, preserved cell metabolic activity, and low cytotoxicity. Air-assisted nozzles did not perform well regarding cell viability and metabolic activity. Flow visualization analysis comparing two different unassisted nozzles using high-speed imaging (100 kHz frame rate) revealed a tulip-shaped spray pattern, indicating optimal spray distribution. High-speed imaging showed differences between the unassisted nozzles. One unassisted nozzle displayed a bi-modal distribution of the droplet diameter while the other unassisted nozzle displayed a mono-modal distribution. These findings demonstrate the critical role of nozzle selection in successful cell delivery. A high-quality, certified nozzle manufactured for human application omits the need for an air-assisted nozzle and provides a simple system to use with similar or better performance characteristics than those of an air-assisted system.

Unveiling the potential of biomaterials and their synergistic fusion in tissue engineering

Inspired by nature, tissue engineering aims to employ intricate mechanisms for advanced clinical interventions, unlocking inherent biological potential and propelling medical breakthroughs. Therefore, medical, and pharmaceutical fields are growing interest in tissue and organ replacement, repair, and regeneration by this technology. Three primary mechanisms are currently used in tissue engineering: transplantation of cells (I), injection of growth factors (II) and cellular seeding in scaffolds (III). However, to develop scaffolds presenting highest potential, reinforcement with polymeric materials is growing interest. For instance, natural and synthetic polymers can be used. Regardless, chitosan and keratin are two biopolymers presenting great biocompatibility, biodegradability and non-antigenic properties for tissue engineering purposes offering restoration and revitalization. Therefore, combination of chitosan and keratin has been studied and results exhibit highly porous scaffolds providing optimal environment for tissue cultivation. This review aims to give an historical as well as current overview of tissue engineering, presenting mechanisms used and polymers involved in the field.

Fabrication and Therapeutic Process of a Green Silver-Nanoparticle-Embedded Mucilage Microsphere for Pathogenic-Bacteria-Infected Second-Degree Burn and Excision Wounds

Multidrug-resistant bacteria are a serious problem in biomedical applications that decrease the wound healing process and increase the mortality rate. Therefore, in this study, we have prepared a green-synthesized silver-nanoparticle-encapsulated mucilage microsphere (HMMS@GSNP) from Hibiscus rosa sinensis leaves and applied it to pathogen-infected burn and excision wounds. Biophysical properties like size, polydispersity index, absorbance capacity, and drug release were measured by different techniques like field-emission scanning electron microscopy, dynamic light scattering, swelling ratio, etc. The strong antibacterial activity of a HMMS@GSNP microsphere was measured by minimum inhibitory concentration assay, minimum bactericidal concentration assay, and agar well diffusion methods. The HMMS@GSNP microsphere enhanced the cell viability, cell proliferation, migration, antioxidant, and antiinflammation activity compared to untreated GSNP and HMMS, as quantified by MTT assay, BrdU assay, scratch wound assay, reactive oxygen species scavenging assay, and Western blot analysis, respectively. In the in vivo experiment, we used a methicillin-resistant Staphylococcus aureus bacteria-infected, burn-and-excision-wound-created male BALB/c mice model. The HMMS@GSNP-treated burn-and-excision-wound-infected mice showed significant results compared to other groups (untreated, Silverex Ionic Gel, AgNO3, HMMS, and GSNP), and the mice tissues were utilized for bacteria count, immunoblot analysis, histological studies, and real-time polymerase chain reaction. Thus, the HMM@GSNP microsphere is an excellent therapeutic material that can be used as a topical agent for the management of chronic wound therapy.

Comparative Analysis of Animal-Derived vs Fully Synthetic Acellular Dermal Matrices in Reconstructive Surgery: An Examination of Clinical, Aesthetic, and Economic Measures

INTRODUCTION

The fully synthetic skin substitute, NovoSorb Biodegradable Temporizing Matrix (BTM), may be a cost-effective alternative to the animal-derived Integra Dermal Regeneration Template (IDRT). However, the current literature insufficiently compares the two. Therefore, our study compared clinical, aesthetic, and economic outcomes in treating soft tissue wounds with IDRT, an animal-derived template, vs BTM, a fully synthetic template.

METHODS

Our single-center retrospective study compared outcomes of 26 patient cases treated with BTM (57.7%) or IDRT (42.3%) during 2011-2022.

RESULTS

The mean surgery time was significantly shorter in BTM cases (1.632 ± 0.571 hours) compared with IDRT cases (5.282 ± 5.102 hours, P = 0.011). Median postoperative hospital stay was notably shorter for BTM placement than IDRT placement (0.95 vs 6.60 days, P = 0.003). The median postoperative follow-up length approached a shorter duration in the BTM group (P = 0.054); however, median follow-up visits were significantly lower in the BTM group compared with the IDRT group (5 vs 14, P = 0.012). The median duration for complete wound closure was shorter for BTM (46.96 vs 118.91 days, P = 0.011). Biodegradable Temporizing Matrix demonstrated a notably lower infection rate (0.0%) compared with IDRT (36.4%, P = 0.022). Integra Dermal Regeneration Template exhibited higher wound hypertrophy rates (81.8%) than BTM (26.7%, P = 0.015). Revisionary surgeries were significantly more frequent in the BTM group (P < 0.001). Failed closure, defined as requiring one or more attempts, exhibited a significant difference, with a higher risk in the IDRT group (26.7%) compared with BTM (6.7%, P = 0.003). Biodegradable Temporizing Matrix showed a lower mean Vancouver Scar Scale adjusted fraction (0.279) compared with IDRT (0.639, P < 0.001). Biodegradable Temporizing Matrix incurred lower costs compared with IDRT but displayed a lower mean profit per square centimeter ($10.63 vs $22.53, P < 0.001).

CONCLUSION

Economically, although the net profit per square centimeter of dermal template may favor IDRT, the ancillary benefits associated with BTM in terms of reduced hospital stay, shorter surgery times, fewer follow-up visits, and lower revisionary surgery rates contribute substantially to overall cost-effectiveness. Biodegradable Temporizing Matrix use reflects more efficient resource use and potential cost savings, aligning with broader trends in healthcare emphasizing value-based and patient-centered care.

Facile process ofHibiscusmucilage polymer formulation usingHibiscus rosa-sinensisleaves to treat second-degree burn and excision wounds

Mucilage is a sticky substance found in various plants and microorganisms and is made up of proteins and polysaccharides. Mucilage fromHibiscus rosa sinensisisis a complex polysaccharide traditionally used to treat different skin diseases. In our study, we fabricated mucilage polymer fromHibiscus rosa sinensisleaves and evaluated its potential application in second-degree burns and excision wounds. The physical properties of Hibiscus mucilage (HM) polymer were demonstrated by using Ultraviolet-visible absorption spectroscopy, x-ray diffraction, Fourier transform infrared spectroscopy, dynamic light scattering, Scanning electron microscopy, Brunauer-Emmett-Tellerand, Swelling ratio. The human cell lines WI-38, and HaCaT have been used forin-vitroexperiments like MTT, scratch wound, BrdU, ROS scavenging assays, and western blot analysis. The results of the MTT, scratch-wound, and BrdU assay indicated that the HM polymer is nontoxic in nature and also enhances both the properties of cellular migration and proliferation, respectively. On the other hand, the result of the ROS scavenging assay suggested that HM polymer enhances the antioxidant activity of cells while the western blot analysis designated that the HM polymer treatment caused downregulation of the pro-inflammatory cytokine IFN-γand upregulation of the pAkt (Serine 473) protein, and TGF-β1 signaling pathway. Therefore, allin-vitroexperimental studies recommended that HM polymer is biocompatible and has antioxidant and anti-inflammatory effects. In thein vivoexperiment, second-degree burns and excision wounds were created on the dorsal surface of male BALB/c mice. After the sixth day of HM polymer treatment have developed new tissue, hair follicles, blood vessels,α-SMA, and Collagen type-1 fiber on the burn and excision wound area while the 11th day of HM polymer treatment cured the wound area significantly. Therefore, it could be contemplated that HM polymer is a potential agent for treating different wounds in the near future.

A Systematic Review of Stem Cell Differentiation into Keratinocytes for Regenerative Applications

To improve wound healing or treatment of other skin diseases, and provide model cells for skin biology studies, in vitro differentiation of stem cells into keratinocyte-like cells (KLCs) is very desirable in regenerative medicine. This study examined the most recent advancements in in vitro differentiation of stem cells into KLCs, the effect of biofactors, procedures, and preparation for upcoming clinical cases. A range of stem cells with different origins could be differentiated into KLCs under appropriate conditions. The most effective ways of stem cell differentiation into keratinocytes were found to include the co-culture with primary epithelial cells and keratinocytes, and a cocktail of growth factors, cytokines, and small molecules. KLCs should also be supported by biomaterials for the extracellular matrix (ECM), which replicate the composition and functionality of the in vivo extracellular matrix (ECM) and, thus, support their phenotypic and functional characteristics. The detailed efficient characterization of different factors, and their combinations, could make it possible to find the significant inducers for stem cell differentiation into epidermal lineage. Moreover, it allows the development of chemically known media for directing multi-step differentiation procedures.In conclusion, the differentiation of stem cells to KLCs is feasible and KLCs were used in experimental, preclinical, and clinical trials. However, the translation of KLCs from in vitro investigational system to clinically valuable cells is challenging and extremely slow.

Development of a membrane and a bilayer of chitosan, gelatin, and polyhydroxybutyrate to be used as wound dressing for the regeneration of rat excisional wounds

The skin is the largest organ in the human body that acts as a protective barrier from the outside environment. Certain dermatological pathologies or significant skin lesions can result in serious complications. Several studies have focused on the development of tissue-engineered skin substitutes. In this study, a new bilayer scaffold composed of a chitosan-gelatin membrane and a chitosan-polyhydroxybutyrate (PHB) porous matrix was synthesized and populated with human adipose-derived mesenchymal stem cells (hASCs) to be potentially used for wound dressing applications. By combining this membrane and porous matrix with the stem cells, we aimed to provide immunomodulation and differentiation capabilities for the wound environment, as well as mechanical strength and biocompatibility for the underlying tissue. The membrane was prepared from the mixture of chitosan and gelatin in a 2:1 ratio and the porous matrix was prepared from the mixture of chitosan and PHB, in equal proportions to form a final solution at 2.5% (m/v). Fourier transform infrared spectroscopy analysis showed the formation of blends, and micro-computed tomography, scanning electron microscopy and atomic force microscopy images demonstrated membrane roughness and matrix porosity. The MTT assay showed that the scaffolds were biocompatible with hASC. The membrane and the bilayer were used as dressing and support for cell migration in the dorsal excisional wound model in Wistar rats. Histological and gene transcriptional analyses showed that the animals that received the scaffolds regenerated the hair follicles in the deep dermis in the central region of the wound. Our results demonstrate the potential of these new biomaterials as dressings in wound healing studies, favoring tissue regeneration.

Alloplastic Epidermal Skin Substitute in the Treatment of Burns

The goal of burn wound treatment is to ensure rapid epithelialization in superficial burns and the process of rebuilding the lost skin in deep burns. Topical treatment plays an important role. One of the innovations in the field of synthetic materials dedicated to the treatment of burns is epidermal skin substitutes. Since the introduction of Suprathel®, the alloplastic epidermal substitute, many research results have been published in which the authors investigated the properties and use of this substitute in the treatment of wounds of various origins, including burn wounds. Burn wounds cause both physical and psychological discomfort, which is why ensuring comfort during treatment is extremely important. Alloplastic epidermal substitute, due to its biodegradability, plasticity, no need to remove the dressing until healing, and the associated reduction in pain, is an alternative for treating burns, especially in children.

A systematic review of the exercise effects on burn wound healing

The emerging evidence has indicated the role of microRNAs (miRNA) in various physiological or pathological processes. Also, documents have suggested that exercise, by affecting miRNA regulation, may enhance burn wound healing. The current study aims to systematically review the role of exercise in regulating miRNAs related to burn wound healing to provide potential therapeutic targets. A comprehensive, systematic search was performed in different international electronic databases, such as Embase, PubMed and Google Scholar search engine, Science Direct, ProQuest and Ovid using keywords extracted from Medical Subject Headings from 2010 to September 2023. The keywords, including 'exercise' AND 'burn wound' AND 'microRNA' and finally, six cases were achieved. Evidence has indicated that exercise may promote the healing of burn wounds by regulating certain miRNAs. Studies have found that exercise regulates the expression of miRNAs such as mir-155, miR-21, let-7a, miR-146a, miR-122 and mir-210 in burn wound tissue, which regulate inflammation and angiogenesis. These findings suggest that miRNAs may play a role in the positive effect of exercise on burn wound healing. However, further research is needed to understand the mechanisms involved fully.

Clinical Indications of Cultured Epithelial Autografts

ABSTRACT

Cultured epithelial autografts (CEAs) have been used for decades as a treatment for massive burn injuries. Cultured epithelial autografts allow for wounds to heal by taking a small sample and growing a patient's own epithelium in culture to create large, graftable sheets. This technique is especially useful in large wounds where donor sites are limited compared with conventional skin grafting. However, CEAs have a variety of uses in wound healing and reconstruction and have the potential to aid in the closure of several types of defects. Cultured epithelial autografts have shown applicability in large burns, chronic nonhealing wounds, ulcerating wounds of various etiologies, congenital defects, wounds requiring specialized epithelium to replace like by like, and wounds in critically ill patients. Several factors must be considered when using CEAs, such as time, cost, and outcomes. In this article, we detail the various clinical applications of CEAs and how they can be situationally advantageous outside of their original purpose.

Ultrasound-Augmented Multienzyme-like Nanozyme Hydrogel Spray for Promoting Diabetic Wound Healing

Treatment of diabetic foot ulcers (DFU) needs to reduce inflammation, relieve hypoxia, lower blood glucose, promote angiogenesis, and eliminate pathogenic bacteria, but the therapeutic efficacy is greatly limited by the diversity and synergy of drug functions as well as the DFU microenvironment itself. Herein, an ultrasound-augmented multienzyme-like nanozyme hydrogel spray was developed using hyaluronic acid encapsulated l-arginine and ultrasmall gold nanoparticles and Cu1.6O nanoparticles coloaded phosphorus doped graphitic carbon nitride nanosheets (ACPCAH). This nanozyme hydrogel spray possesses five types of enzyme-like activities, including superoxide dismutase (SOD)-, catalase (CAT)-, glucose oxidase (GOx)-, peroxidase (POD)-, and nitric oxide synthase (NOS)-like activities. The kinetics and reaction mechanism of the sonodynamic/sonothermal synergistic enhancement of the SOD-CAT-GOx-POD/NOS cascade reaction of ACPCAH are fully investigated. Both in vitro and in vivo tests demonstrate that this nanozyme hydrogel spray can be activated by the DFU microenvironment to reduce inflammation, relieve hypoxia, lower blood glucose, promote angiogenesis, and eliminate pathogenic bacteria, thus accelerating diabetic wound healing effectively. This study highlights a competitive approach based on multienzyme-like nanozymes for the development of all-in-one DFU therapies.

Transplantation of human induced pluripotent stem cell derived keratinocytes accelerates deep second-degree burn wound healing

BACKGROUND

Current evidence shows that human induced pluripotent stem cells (hiPSCs) can effectively differentiate into keratinocytes (KCs), but its effect on skin burn healing has not been reported.

AIM

To observe the effects of hiPSCs-derived KCs transplantation on skin burn healing in mice and to preliminarily reveal the underlying mechanisms.

METHODS

An analysis of differentially expressed genes in burn wounds based on GEO datasets GSE140926, and GSE27186 was established. A differentiation medium containing retinoic acid and bone morphogenetic protein 4 was applied to induce hiPSCs to differentiate into KCs. The expression of KCs marker proteins was detected using immunofluorescence staining. A model of a C57BL/6 mouse with deep cutaneous second-degree burn was created, and then phosphate buffered saline (PBS), hiPSCs-KCs, or hiPSCs-KCs with knockdown of COL7A1 were injected around the wound surface. The wound healing, re-epithelialization, engraftment of hiPSCs-KCs into wounds, proinflammatory factor level, and the NF-κB pathway proteins were assessed by hematoxylin-eosin staining, carboxifluorescein diacetate succinimidyl ester (CFSE) fluorescence staining, enzyme linked immunosorbent assay, and Western blotting on days 3, 7, and 14 after the injection, respectively. Moreover, the effects of COL7A1 knockdown on the proliferation and migration of hiPSCs-KCs were confirmed by immunohistochemistry, EdU, Transwell, and damage repair assays.

RESULTS

HiPSCs-KCs could express the hallmark proteins of KCs. COL7A1 was down-regulated in burn wound tissues and highly expressed in hiPSCs-KCs. Transplantation of hiPSCs-KCs into mice with burn wounds resulted in a significant decrease in wound area, an increase in wound re-epithelialization, a decrease in proinflammatory factors content, and an inhibition of NF-κB pathway activation compared to the PBS group. The in vitro assay showed that COL7A1 knockdown could rescue the inhibition of hiPSCs-KCs proliferation and migration, providing further evidence that COL7A1 speeds up burn wound healing by limiting cell proliferation and migration.

CONCLUSION

In deep, second-degree burn wounds, COL7A1 can promote KC proliferation and migration while also suppressing the inflammatory response.

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.

Burn wound conversion: clinical implications for the treatment of severe burns

The identification of novel treatments for severe burn wounds relies on accurate clinical assessments of the extent of injury. However, evaluation of burn wound depth can be challenging due to the tendency for burn wounds to progress over time in a little-understood process known as 'burn wound conversion'. Local factors affecting the burn wound, such as inflammation, oxidative stress-induced tissue damage, vasostasis and bacterial infections, lead to increased cell death by apoptosis or oncosis, while systemic events may promote burn wound conversion. Acute shock, metabolic derangements, age or immunomodulation can modify cytokine secretion, lower immune responses, decrease blood flow or cause bacterial infection at the burn wound site. Therefore, therapeutic approaches targeting specific mechanisms that reduce cell death, improve wound reperfusion and promote tissue regrowth should favourably enhance burn wound healing, and long-term functional and aesthetic outcomes. Our current understanding of these mechanisms mostly comes from animal studies, underscoring the need for extensive research in humans. A streamlined approach would be to investigate the parallels in other disease states that exhibit ischaemia and potential reperfusion, such as ischaemic stroke and myocardial infarction. Moreover, in view of the limited knowledge available on the subject, the need exists for further clinical research into burn wound conversion and novel target pathways to ameliorate its effects. This review describes events that affect the viability of cells at the burn wound site resulting in burn wound conversion, and identifies potential targets for clinical interventions that may diminish burn wound conversion.

Wound healing by transplantation of mesenchymal stromal cells loaded on polyethylene terephthalate scaffold: Implications for skin injury treatment

BACKGROUND

Several clinical studies have shown that cellular therapy based on mesenchymal stromal cells (MSCs) transplantation may accelerate wound healing. One major challenge is the delivery system used for MSCs transplantation. In this work, we evaluated the capacity of a scaffold based on polyethylene terephthalate (PET) to maintain the viability and biological functions of MSCs, in vitro. We examined the capacity of MSCs loaded on PET (MSCs/PET) to induce wound healing in an experimental model of full-thickness wound.

METHODS

Human MSCs were seeded and cultured on PET membranes at 37 °C for 48 h. Adhesion, viability, proliferation, migration, multipotential differentiation and chemokine production were evaluated in cultures of MSCs/PET. The possible therapeutic effect of MSCs/PET on the re-epithelialization of full thickness wounds was examined at day 3 post-wounding in C57BL/6 mice. Histological and immunohistochemical (IH) studies were performed to evaluate wound re-epithelialization and the presence of epithelial progenitor cells (EPC). As controls, wounds without treatment or treated with PET were established.

RESULTS

We observed MSCs adhered to PET membranes and maintained their viability, proliferation and migration. They preserved their multipotential capacity of differentiation and ability of chemokine production. MSCs/PET implants promoted an accelerated wound re-epithelialization, after three days post-wounding. It was associated with the presence of EPC Lgr6⁺ and K6⁺.

DISCUSSION

Our results show that MSCs/PET implants induce a rapid re-epithelialization of deep- and full-thickness wounds. MSCs/PET implants constitute a potential clinical therapy for treating cutaneous wounds.

Role of Oral Retinoids in Treatment of Acne Vulgaris With a Bioinformatics-Based Perspective of Personalized Medicine

Acne vulgaris is a skin condition characterized by the inflammation or hyperactivity of sebaceous glands on the skin, which results in the creation of comedones, lesions, nodules, and perifollicular hyperkeratinization. Increased sebum production, follicular blockage, and bacterial colonization may contribute to the disease etiology. Environmental factors, hormonal imbalance, and genetic predisposition can alter the severity of the disease. Its mental and monetary effects can be problematic for the society. In this study, we examined the role of isotretinoin in the treatment of acne vulgaris based on evidence from prior research. This review literature study compiled publications on the treatment of acne vulgaris from 1985 to 2022 based on PubMed and Google Scholar publications. Additional bioinformatics analyses were accompanied by GeneCards, STRING model, and DrugBank databases. These complementary analyses were designed to obtain a better perspective of personalized medicine which is highly required for dose-precise administrations of acne vulgaris treatment. Isotretinoin has been recognized as an effective treatment for acne vulgaris, particularly in cases that have been resistant to previous medications or have resulted in scarring, according to gathered data. Oral isotretinoin inhibits the proliferation of Propionibacterium acne, a critical factor in the development of acne lesions; also, it has been shown to be effective in reducing the number of Propionibacterium-resistant patients and regulating sebum production and reducing sebaceous gland size more effectively than other treatment options resulting in general improvements in skin clarity and acne severity and reduce inflammatory in 90% of patients. In addition to its efficacy, the majority of patients have shown that oral isotretinoin is well tolerated. This review highlights the use of oral retinoids, particularly isotretinoin, as an effective and well-tolerated treatment option for acne vulgaris. It has been proven that oral isotretinoin is useful for achieving long-lasting remission in patients with severe or resistant instances. Despite the fact that oral isotretinoin is related to a number of potential harmful effects, skin dryness was the most common side effect reported by patients that can be managed with the aid of suitable monitoring and drug administration against specific genes identified by genotyping of the susceptible variants of genes involved in TGFβ signaling pathway.

FEATURES OF QUALITY CONTROL STRATEGY FOR DRUGS BASED ON VIABLE SKIN CELLS

The aim of the study was to research the international experience in quality assurance of the products based on skin cells in order to identify the features of the quality control strategy in the development, production, as well as during an expert quality assessment as a part of the state registration procedure in the Russian Federation.

Materials and methods. The article provides an analysis of the materials presented in the assessment reports of the USA and Japanese regulatory authorities, as well as on the official websites of manufacturers, in review and scientific papers on the study of the structure and properties of tissue-engineered skin analogs.

Results. The manufacture of products containing human skin cells is associated with such risks as the possibility of contamination of the preparation with infective agents transmitted by materials of the animal origin, feeder cells, donor cells, or during the manufacturing process; a small amount of biopsy materials; a complexity of a three-dimensional product structure when combining cells with a scaffold; continuity of the manufacture process and a short product expiry date. The raw materials and reagents control, the creation of cell banks, using animal feeder cells only from qualified cell banks, an in-process control and release testing in accordance with the requirements of the finished product specification, make it possible to obtain a preparation with a reproducible quality. The specification should contain information about the identity, safety and potency of the product. For each preparation, the choice of approaches for assessing the quality is individual and depends on its composition and mode of action.

Conclusion. The features of the quality control strategy for the drugs based on human skin cells, consist in the implementation of control measures in order to obtain a proper quality of cellular (viability, sterility, identity, potency, et al) and non-cellular (physico-chemical scaffold properties) components or the whole graft (bioburden, barrier properties). The approaches and methods for determining the potency should be selected individually for each product and reflect the number, viability and identity of cells, a proliferative activity and secretable ability of the cellular component.

Angiopoietin-1 derived peptide hydrogel promotes molecular hallmarks of regeneration and wound healing in dermal fibroblasts

By providing an ideal environment for healing, biomaterials can be designed to facilitate and encourage wound regeneration. As the wound healing process is complex, there needs to be consideration for the cell types playing major roles, such as fibroblasts. As a major cell type in the dermis, fibroblasts have a large impact on the processes and outcomes of wound healing. Prevopisly, conjugating the angiopoietin-1 derived Q-peptide (QHREDGS) to a collagen-chitosan hydrogel created a biomaterial with in vivo success in accelerating wound healing. This study utilized solvent cast Q-peptide conjugated collagen-chitosan seeded with fibroblast monolayers to investigate the direct impact of the material on this major cell type. After 24 h, fibroblasts had a significant change in release of anti-inflammatory, pro-healing, and ECM deposition cytokines, with demonstrated immunomodulatory effects on macrophages and upregulated expression of critical wound healing genes.

Application and Management of Cultured Epidermal Autografts on Posterior Burns-A 5-Year, Multicenter, Retrospective Review of Outcomes

Severe burns on the posterior trunk present a treatment challenge in that these surfaces bear the major portion of body weight, with shearing forces exerted when changing the patient from supine to prone position. In their high-volume center at Burn and Reconstructive Centers of America, the authors developed protocols for use of cultured epidermal autografts (CEAs) for coverage of large burns, including those specific to posterior burns. This paper describes techniques and approaches, including milestone timelines, to treat and manage these patients. Key factors for successful treatment begin with early development of a detailed surgical plan. Members of the trained team participate in the plan and understand standard procedures and any deviation. Patients are identified early for treatment with CEA so that a full thickness skin biopsy can be sent to the manufacturer for processing. Patients with >30% total body surface area (TBSA) burns are considered for CEA burn wound coverage due to the potential for conversion of superficial partial thickness to deep partial thickness or full thickness burns over hospitalization time. We also present the outcomes in patients with posterior trunk burns treated with CEA from 2016 to 2019 in three participating centers within our network. Data in 40 patients with mean TBSA of 56% demonstrated a high rate of successful CEA engraftment (83%), and overall survival rate (90%) following one or two applications with CEA and/or CEA + split thickness skin graft (STSG). Development of standard treatment protocols and surgical plans has enabled positive outcomes with CEA in severe burns including posterior burns.

Burn Wound Bed Management

Critical to the success of modern burn care is the management of the burn wound. Timely and complete removal of nonviable tissue is complicated by the irreplaceable nature of the tissue lost either through the burn injury or as "collateral damage" as part of the treatment. Challenges in distinguishing between viable and nonviable tissue and "replacing the irreplaceable" are discussed alongside potential disruptive technologies which could fundamentally change how burn care is delivered. Advances in burn wound bed management forms the foundation on which the goal of zero preventable death and disability after burn injury can be achieved.

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.

New insights into balancing wound healing and scarless skin repair

Scars caused by skin injuries after burns, wounds, abrasions and operations have serious physical and psychological effects on patients. In recent years, the research of scar free wound repair has been greatly expanded. However, understanding the complex mechanisms of wound healing, in which various cells, cytokines and mechanical force interact, is critical to developing a treatment that can achieve scarless wound healing. Therefore, this paper reviews the types of wounds, the mechanism of scar formation in the healing process, and the current research progress on the dual consideration of wound healing and scar prevention, and some strategies for the treatment of scar free wound repair.

3-D tissue-engineered epidermis against human primary keratinocytes apoptosis via relieving mitochondrial oxidative stress in wound healing

The tissue-engineered epidermal (TEE), composed of biocompatible vectors and autogenous functional cells, is a novel strategy to solve the problem of shortage of donor skin sources. The human primary keratinocyte (HPK), the major skin components, are self-evident vital in wound healing and was considered as one of the preferred seed cells for TEEs. Since the process of separating HPKs from the skin triggers a stress state of the cells, achieving its rapid adhesion and proliferation on biomaterials remains challenging. The key to the clinical application is to ensure the normal function of cells while improving the proliferation ability in vitro, and to complete the complex mesenchymal epithelialization to achieve tissue remodeling after vivo implantation. Herein, in order to aid HPKs adhesion and proliferation in vitro and promoting wound healing, we developed a three dimensional collagen scaffold with Y-27632 sustainedly released from the nanoplatform, hollow mesoporous organosilica nanoparticles (HMON). The results showed that the porous structure within the TEE supports the implanted HPKs expanding in a three-dimensional mode to jointly construct the tissue-engineered epidermis in vitro and inhibited the mitochondria-mediated cell apoptosis. It was confirmed that the TEEs with suitable degradation rate could maintain drug release after implantation and could accelerate vascularization of wound base and further revealed the involvement of mesenchymal transformation of transplanted HPKs during skin regeneration in a nude mouse model with full-thickness skin resection. In conclusion, our study highlights the great potential of constructing TEE using a nanoparticle platform for the treatment of large-area skin defects.

Cell-surface contacts determine volume and mechanical properties of human embryonic kidney 293 T cells

Alterations in the organization of the cytoskeleton precede the escape of adherent cells from the framework of cell-cell and cell-matrix interactions into suspension. With cytoskeletal dynamics being linked to cell mechanical properties, many studies elucidated this relationship under either native adherent or suspended conditions. In contrast, tethered cells that mimic the transition between both states have not been the focus of recent research. Using human embryonic kidney 293 T cells we investigated all three conditions in the light of alterations in cellular shape, volume, as well as mechanical properties and relate these findings to the level, structure, and intracellular localization of filamentous actin (F-actin). For cells adhered to a substrate, our data shows that seeding density affects cell size but does not alter their elastic properties. Removing surface contacts leads to cell stiffening that is accompanied by changes in cell shape, and a reduction in cellular volume but no alterations in F-actin density. Instead, we observe changes in the organization of F-actin indicated by the appearance of blebs in the semi-adherent state. In summary, our work reveals an interplay between molecular and mechanical alterations when cells detach from a surface that is mainly dominated by cell morphology.

Fabrication and characterization of bilayer scaffolds - nanocellulosic cryogels - for skin tissue engineering by co-culturing of fibroblasts and keratinocytes

This study focuses on developing a microarchitectural bilayer structure for stimulating the two top layers of skin tissue (epidermis and dermis) fabricated using a one-step freeze-drying method. Cellulose nanofibers (CNFs) and poly (vinyl) alcohol (PVA) were used as a biocompatible scaffolding material, and the composition was designed in such a way that it provides physical and biological property attributes. In this work, scaffolding materials with integrated layer structures and well interconnected and open pore structures were obtained. This bilayer structure had porosity with a pore size of 19.72 μm and 90.71 μm for the simulation of the epidermis and dermis, respectively. The production and expression of laminin, collagen IV, and keratin 10 proteins in the bilayer cryogel scaffolds obtained from the immunofluorescence study were 49.7 %, 63.8 %, and 49.3 %, respectively. The extracellular matrix (ECM) was produced in each scaffold layer. The observations confirmed that the porosity and pore size of both N1 and N2 layers were appropriate for the fibroblast and keratinocyte cells, respectively. H&E stained cross-sections of bilayer cryogel scaffolds illustrated epidermal and dermal layers produced by co-culturing keratinocytes and fibroblasts. Based on the results, the bilayer CNF/PVA scaffold can be used in skin tissue engineering applications. However, more experiments and in vivo evaluations are needed to express this conclusion more accurately.

Classic and Current Opinions in Human Organ and Tissue Transplantation

Graft tolerance is a pathophysiological condition heavily reliant on the dynamic interaction of the innate and adaptive immune systems. Genetic polymorphism determines immune responses to tissue/organ transplantation, and intricate humoral and cell-mediated mechanisms control these responses. In transplantation, the clinician's goal is to achieve a delicate equilibrium between the allogeneic immune response, undesired effects of the immunosuppressive drugs, and the existing morbidities that are potentially life-threatening. Transplant immunopathology involves sensitization, effector, and apoptosis phases which recruit and engages immunological cells like natural killer cells, lymphocytes, neutrophils, and monocytes. Similarly, these cells are involved in the transfer of normal or genetically engineered T cells. Advances in tissue transplantation would involve a profound knowledge of the molecular mechanisms that underpin the respective immunopathology involved and the design of precision medicines that are safe and effective.

Skin cell-derived extracellular vesicles: a promising therapeutic strategy for cutaneous injury

Wound healing refers to the healing process that occurs after the skin and other tissues are separated or damaged by internal or external forces. It is a complex combination of tissue regeneration, granulation tissue hyperplasia, and scar formation, and shows the synergistic effects of these processes. After skin damage, the environment around the wound and the cells at site of the damage respond immediately, and a range of cytokines and growth factors are released. In cutaneous injury, extracellular vesicle (EV) signaling plays a vital role in the healing process via paracrine and endocrine mechanisms. EVs are natural intercellular and inter-organ communication tools that carry various bioactive substances for message exchange. Stem cells and stem cell EVs facilitate tissue repair, showing promising potential in regenerative medicine. Nevertheless, EVs derived from specific skin tissue cells, such as epidermal cells, fibroblasts, vascular endothelial cells and inflammatory cells, also play important roles in cutaneous tissue repair. Here, we describe the characteristics of wound healing, concentrating on the production and functions of EVs derived from specific skin cells, and provide new ideas for wound therapy using EVs.

Silicon-Based Scaffold for Wound Healing Skin Regeneration Applications: A Concise Review

Silicon has made its breakthrough in various industries, including clinical and biomedical applications. Silicon-based biomaterials that were fabricated into various types of scaffolds may attract interest due to their highly favorable properties covering their excellent biocompatibility, high surface area, mechanical strength, and selectivity depending on their application including film, hydrogel, nanoparticles, and so on. Silicon-based materials have also shown exciting results involving cell culture, cell growth, as well as tissue engineering. In this article, a simple review compromising the evaluation of silicon's unique properties has been discussed and followed by the application of the silicone-based product in future perspectives in biomedical fields. The review goals are to widen and inspire broader interest in silicone-based materials in wound healing research.

Additive Manufacturing of Biomaterials-Design Principles and Their Implementation

Additive manufacturing (AM, also known as 3D printing) is an advanced manufacturing technique that has enabled progress in the design and fabrication of customised or patient-specific (meta-)biomaterials and biomedical devices (e.g., implants, prosthetics, and orthotics) with complex internal microstructures and tuneable properties. In the past few decades, several design guidelines have been proposed for creating porous lattice structures, particularly for biomedical applications. Meanwhile, the capabilities of AM to fabricate a wide range of biomaterials, including metals and their alloys, polymers, and ceramics, have been exploited, offering unprecedented benefits to medical professionals and patients alike. In this review article, we provide an overview of the design principles that have been developed and used for the AM of biomaterials as well as those dealing with three major categories of biomaterials, i.e., metals (and their alloys), polymers, and ceramics. The design strategies can be categorised as: library-based design, topology optimisation, bio-inspired design, and meta-biomaterials. Recent developments related to the biomedical applications and fabrication methods of AM aimed at enhancing the quality of final 3D-printed biomaterials and improving their physical, mechanical, and biological characteristics are also highlighted. Finally, examples of 3D-printed biomaterials with tuned properties and functionalities are presented.

Innovative Treatment Strategies to Accelerate Wound Healing: Trajectory and Recent Advancements

Wound healing is highly specialized dynamic multiple phase process for the repair of damaged/injured tissues through an intricate mechanism. Any failure in the normal wound healing process results in abnormal scar formation, and chronic state which is more susceptible to infections. Chronic wounds affect patients’ quality of life along with increased morbidity and mortality and are huge financial burden to healthcare systems worldwide, and thus requires specialized biomedical intensive treatment for its management. The clinical assessment and management of chronic wounds remains challenging despite the development of various therapeutic regimens owing to its painstakingly long-term treatment requirement and complex wound healing mechanism. Various conventional approaches such as cell therapy, gene therapy, growth factor delivery, wound dressings, and skin grafts etc., are being utilized for promoting wound healing in different types of wounds. However, all these abovementioned therapies are not satisfactory for all wound types, therefore, there is an urgent demand for the development of competitive therapies. Therefore, there is a pertinent requirement to develop newer and innovative treatment modalities for multipart therapeutic regimens for chronic wounds. Recent developments in advanced wound care technology includes nanotherapeutics, stem cells therapy, bioengineered skin grafts, and 3D bioprinting-based strategies for improving therapeutic outcomes with a focus on skin regeneration with minimal side effects. The main objective of this review is to provide an updated overview of progress in therapeutic options in chronic wounds healing and management over the years using next generation innovative approaches. Herein, we have discussed the skin function and anatomy, wounds and wound healing processes, followed by conventional treatment modalities for wound healing and skin regeneration. Furthermore, various emerging and innovative strategies for promoting quality wound healing such as nanotherapeutics, stem cells therapy, 3D bioprinted skin, extracellular matrix-based approaches, platelet-rich plasma-based approaches, and cold plasma treatment therapy have been discussed with their benefits and shortcomings. Finally, challenges of these innovative strategies are reviewed with a note on future prospects.

Hormesis and Epidermal Stem Cells

This paper provides an assessment of hormetic dose responses in epidermal stem cells (EpSCs) in animal models and humans, with emphasis on cell proliferation and differentiation and application to wound healing and aging processes. Hormetic dose responses were induced by several agents, including dietary supplements (eg, luteolin, quercetin), pharmaceuticals (eg, nitric oxide), endogenous agents (eg, growth/differentiation factor 5), and via diverse chemical means to sustain steaminess features to retard aging and disease onset. While hormetic dose responses have been extensively reported in a broad spectrum of stem cells, this area has only been explored to a limited extent in EpSCs, principally within the past 5 years. Nonetheless, these findings provide the first integrated assessment of hormesis and EpSC biology within the context of enhancing key functions such as cell proliferation and differentiation and resilience to inflammatory stresses. This paper assesses putative mechanisms of hormetic responses in EpSCs and potential therapeutic applications to prevent dermatological injury and disease.

Exosomes from human induced pluripotent stem cells-derived keratinocytes accelerate burn wound healing through miR-762 mediated promotion of keratinocytes and endothelial cells migration

Background

The use of keratinocytes derived from induced pluripotent stem cells (iPSCs-KCs) may represent a novel cell therapy strategy for burn treatment. There is growing evidence that extracellular vesicles, including exosomes, are primary mediators of the benefits of stem cell therapy. Herein, we thus explored the effects of exosomes produced by iPSCs-derived keratinocytes (iPSCs-KCs-Exos) in a model of deep second-degree burn wound healing and evaluated the mechanistic basis for the observed activity.

Methods

iPSCs-KCs-Exos were isolated from conditioned medium of iPSCs-KCs and verified by electron micrograph and size distribution. Next, iPSCs-KCs-Exos were injected subcutaneously around wound sites, and its efficacy was evaluated by measuring wound closure areas, histological examination, and immunohistochemistry staining. The effects of iPSCs-KCs-Exos on proliferation and migration of keratinocytes and endothelial cells in vitro were assessed by EdU staining, wound healing assays, and transwell assay. Then, high-throughput microRNA sequencing was used to explore the underlying mechanisms. We assessed the roles of miR-762 in iPSCs-KCs-Exos-induced regulation of keratinocytes and endothelial cells migration. Furthermore, the target gene which mediated the biological effects of miR-762 in keratinocytes and endothelial cells was also been detected.

Results

The analysis revealed that iPSCs-KCs-Exos application to the burn wound drove the acceleration of wound closure, with more robust angiogenesis and re-epithelialization being evident. Such iPSCs-KCs-Exos treatment effectively enhanced endothelial cell and keratinocyte migration in vitro. Moreover, the enrichment of miR-762 was detected in iPSCs-KCs-Exos and was found to target promyelocytic leukemia (PML) as a means of regulating cell migration through a mechanism tie to integrin beta1 (ITGB1).

Conclusion

These results thus provide a foundation for the further study of iPSCs-KCs-Exos as novel cell-free treatments for deep second-degree burns.

Graphical Abstract

Glassy-like Metal Oxide Particles Embedded on Micrometer Thicker Alginate Films as Promising Wound Healing Nanomaterials

Micrometer-thicker, biologically responsive nanocomposite films were prepared starting from alginate-metal alkoxide colloidal solution followed by sol-gel chemistry and solvent removal through evaporation-induced assembly. The disclosed approach is straightforward and highly versatile, allowing the entrapment and growth of a set of glassy-like metal oxide within the network of alginate and their shaping as crake-free transparent and flexible films. Immersing these films in aqueous medium triggers alginate solubilization, and affords water-soluble metal oxides wrapped in a biocompatible carbohydrate framework. Biological activity of the nano-composites films was also studied including their hemolytic activity, methemoglobin, prothrombin, and thrombine time. The effect of the films on fibroblasts and keratinocytes of human skin was also investigated with a special emphasis on the role played by the incorporated metal oxide. This comparative study sheds light on the crucial biological response of the ceramic phase embedded inside of the films, with titanium dioxide being the most promising for wound healing purposes.

Fibroblasts in Scar Formation: Biology and Clinical Translation

Scarring, which develops due to fibroblast activation and excessive extracellular matrix deposition, can cause physical, psychological, and cosmetic problems. Fibroblasts are the main type of connective tissue cells and play important roles in wound healing. However, the underlying mechanisms of fibroblast in reaching scarless wound healing require more exploration. Herein, we systematically reviewed how fibroblasts behave in response to skin injuries, as well as their functions in regeneration and scar formation. Several biocompatible materials, including hydrogels and nanoparticles, were also suggested. Moreover, factors that concern transformation from fibroblasts into cancer-associated fibroblasts are mentioned due to a tight association between scar formation and primary skin cancers. These findings will help us better understand skin fibrotic pathogenesis, as well as provide potential targets for scarless wound healing therapies.

The Role of Skin Substitutes in Acute Burn and Reconstructive Burn Surgery: An Updated Comprehensive Review

Burns disrupt the protective skin barrier with consequent loss of cutaneous temperature regulation, infection prevention, evaporative losses, and other vital functions. Chronically, burns lead to scarring, contractures, pain, and impaired psychosocial well-being. Several skin substitutes are available and replace the skin and partially restore functional outcomes and improve cosmesis. We performed a literature review to update readers on biologic and synthetic skin substitutes to date applied in acute and reconstructive burn surgery. Improvement has been rapid in the development of skin substitutes in the last decade; however, no available skin substitute fulfills criteria as a perfect replacement for damaged skin.

Advances in spray products for skin regeneration

To date, skin wounds are still an issue for healthcare professionals. Although numerous approaches have been developed over the years for skin regeneration, recent advances in regenerative medicine offer very promising strategies for the fabrication of artificial skin substitutes, including 3D bioprinting, electrospinning or spraying, among others. In particular, skin sprays are an innovative technique still under clinical evaluation that show great potential for the delivery of cells and hydrogels to treat acute and chronic wounds. Skin sprays present significant advantages compared to conventional treatments for wound healing, such as the facility of application, the possibility to treat large wound areas, or the homogeneous distribution of the sprayed material. In this article, we review the latest advances in this technology, giving a detailed description of investigational and currently commercially available acellular and cellular skin spray products, used for a variety of diseases and applying different experimental materials. Moreover, as skin sprays products are subjected to different classifications, we also explain the regulatory pathways for their commercialization and include the main clinical trials for different skin diseases and their treatment conditions. Finally, we argue and suggest possible future trends for the biotechnology of skin sprays for a better use in clinical dermatology.

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Skin sprays represent a promising technique for wound healing applications.

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Skin sprays can deliver cells and hydrogels with great facility over large wounds.

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Many skin spray products have been studied, only a few have been commercialized.

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Numerous clinical trials study spray products for skin diseases like psoriasis.

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Improved spraying devices should be developed for different materials and cells.

Chemical Composition of Salix koreensis Anderss Flower Absolute and Its Skin Wound Healing Activities In Vitro

Salix koreensis Anderss (SKA) has been used traditionally to treat inflammation, pain, and edema. SKA has anti-inflammatory and antioxidant effects, but no study has examined its effects on skin wound healing. Here, we aimed to investigate the effects of the absolute extracted from SKA flower (SKAFAb) on skin wound healing-associated responses in keratinocytes. SKAFAb was produced using a solvent extraction method and its chemical composition was analyzed by gas chromatography/mass spectrometry. The effects of SKAFAb on HaCaT cells (a human epidermal keratinocyte cell line) were investigated using a Boyden chamber and 5-bromo-2′-deoxyuridine incorporation, sprout outgrowth, immunoblotting, enzyme-linked immunosorbent, and water-soluble tetrazolium salt assays. Sixteen constituents were identified in SKAFAb. SKAFAb promoted HaCaT cell proliferation, migration, and type I and IV collagen productions. SKAFAb increased sprout outgrowth and increased the phosphorylations of serine/threonine-specific protein kinase (Akt), c-Jun NH2-terminal kinase, extracellular signal-regulated kinase1/2, and p38 mitogen-activated protein kinase (MAPK) in HaCaT cells. These results indicate that SKAFAb promotes keratinocyte proliferation and migration, probably by activating Akt and MAPK signaling pathways, and induces collagen synthesis in keratinocytes. SKAFAb may be a promising material for promoting skin wound healing.

Use of Cultivated Epidermal Allograft in Chronic Wounds: A Novel Therapeutic Alternative

Introduction

Chronic wounds represent a frequent cause of consultation for plastic and reconstructive surgeons. The use of epidermal culture stands out because they provide complete epithelialization, adequate aesthetic-functional results, and no morbidity for the patient. Epifast® is a pre-manufactured cultured epidermal allograft derived from the amplification in vitro of human keratinocytes.

Materials and Methods

A prospective longitudinal multicenter study was carried out in four chronic wound reference centers, which were in charge of plastic and reconstructive surgery services. For a standardized wound bed preparation, the protocol synthesized by the acronym "TIME" was used. At the end of the "TIME" protocol, the pre-fabricated allograft was applied and removed 7 days after its application.

Results

A total of 133 patients with diagnosis of chronic wound were included in the study. The median age was 69.3 ± 13.6 years. The most common comorbidity found was diabetes mellitus type 2 in 71.4% of the patients (n = 95) and systemic arterial hypertension in 60.2% of the patients (n = 80). The most frequent location of chronic wounds was seen in the lower extremity with 45.1% (n = 60). The mean duration for it to close was 46 ± 14 days, in which they closed within the first 3 months in 93% (n = 125) of the cases. About 91.7% (n = 122) of the wounds achieved total closure.

Conclusion

Cultured epidermal allograft, combined with a meticulous technique and an adequate selection of patients, represents a safe and effective tool for chronic wounds.

The role of keratinocyte function on the defected diabetic wound healing

Non-healing wounds are a major complication of diabetes that can lead to limb amputation and disability in patients. The normal process of wound repair progresses through well-defined stages including hemostasis, inflammation, proliferative, and remodeling, which may be impaired in diabetic wounds. In recent years, it has been reported that keratinocytes, a major cell type in human skin, play a key role in the healing process of wounds. In this overview, firstly, a summary of the wound healing process is provided and the role of keratinocytes in wound healing is briefly reviewed. Then, a set of evidence about the impaired keratinocytes activities in diabetic wounds and clinical trials focused mainly on improving keratinocytes in the context of diabetic wound therapeutics are summarized. Keratinocytes can produce signaling molecules that act in a paracrine and autocrine way, causing pleiotropic effects on various cell types. The affected cells respond to keratinocytes by creating several signaling molecules, which also adjust keratinocyte activation through wound healing. In diabetic wounds, disruption of various biological mechanisms leads to dysfunction of keratinocytes including impaired migration, adhesion, and proliferation. The function of abnormal keratinocytes can lead to poor diabetic wound healing. Taken together, clarification of molecular and functional disturbances of keratinocyte cells and applying them in diabetic wounds can contribute to enhanced treatment of diabetic wounds. Based on the location of keratinocytes in the epidermis and the central role of keratinocytes in the diabetic wound healing process, applying keratinocytes has great potential for the treatment of diabetic burn wounds.

Early non-excisional debridement of paediatric burns under general anaesthesia reduces time to re-epithelialisation and risk of skin graft

Reported advantages of early excision for larger burn injuries include reduced morbidity, mortality, and hospital length of stay for adult burn patients. However, a paucity of evidence supports the best option for paediatric burns and the advantages of non-excisional (mechanical) debridement. Procedural sedation and analgesia in the emergency department is a popular alternative to debridement in operating theatres under general anaesthesia. This study aims to evaluate the association between early (< 24 h post-injury) non-excisional debridement under general anaesthesia with burn wound re-epithelialisation time and skin graft requirements. Cohort study of children younger than 17 years who presented with burns of five percent total body surface area or greater. Data from January 2013 to December 2019 were extracted from a prospectively collected state-wide paediatric burns' registry. Time to re-epithelialisation was tested using survival analysis, and binary logistic regression for odds of skin graft requirementto analyse effects of early non-excisional debridement in the operating theatre. Overall, 292 children met eligibility (males 55.5%). Early non-excisional debridement under general anaesthesia in the operating theatre, significantly reduced the time to re-epithelialisation (14 days versus 21 days, p = 0.029)) and the odds of requiring a skin graft in comparison to paediatric patients debrided in the emergency department under Ketamine sedation (OR: 6.97 (2.14-22.67), p < 0.001. This study is the first to demonstrate that early non-excisional debridement under general anaesthesia in the operating theatre significantly reduces wound re-epithelialisation time and subsequent need for a skin graft in paediatric burn patients. Analysis suggests that ketamine procedural sedation and analgesia in the emergency department used for burn wound debridement is not an effective substitute for debridement in the operating theatre.

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

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

Conductive Biomaterials as Bioactive Wound Dressing for Wound Healing and Skin Tissue Engineering

Conductive biomaterials based on conductive polymers, carbon nanomaterials, or conductive inorganic nanomaterials demonstrate great potential in wound healing and skin tissue engineering, owing to the similar conductivity to human skin, good antioxidant and antibacterial activities, electrically controlled drug delivery, and photothermal effect. However, a review highlights the design and application of conductive biomaterials for wound healing and skin tissue engineering is lacking. In this review, the design and fabrication methods of conductive biomaterials with various structural forms including film, nanofiber, membrane, hydrogel, sponge, foam, and acellular dermal matrix for applications in wound healing and skin tissue engineering and the corresponding mechanism in promoting the healing process were summarized. The approaches that conductive biomaterials realize their great value in healing wounds via three main strategies (electrotherapy, wound dressing, and wound assessment) were reviewed. The application of conductive biomaterials as wound dressing when facing different wounds including acute wound and chronic wound (infected wound and diabetic wound) and for wound monitoring is discussed in detail. The challenges and perspectives in designing and developing multifunctional conductive biomaterials are proposed as well.

Xeno-free workflow exhibits comparable efficiency and quality of keratinocytes isolated from human skin biopsies

INTRODUCTION

Regenerative solutions of the skin represent a hope for burn victims with extensive skin loss and chronic wound patients. The development of xeno-free workflow is crucial for clinical application in compliance with the directives of the European Medicines Agency. This study aimed at evaluating the outcome of the xeno-free isolation workflow of keratinocytes from human skin biopsy.

METHODS

Skin biopsies were obtained from volunteers. The epidermis was digested with TrypLE™ Select, which was deactivated by dilution or with trypsin, deactivated by media with fetal bovine serum. Freshly isolated cells were compared for total cell number, viability, activity of caspase 3, gene expression and the presence of the keratinocyte surface markers cytokeratin 14. The cells were cultured in xeno-free conditions for one week and characterized regarding the number and viability as well as the metalloproteinase secretion.

RESULTS

The number of obtained cells was similar in both workflows. The cell viability was less in the TrypLE group, with slight reduction of the cell surface marker cytokeratin 14. Caspase 3 activity was comparable as well as the gene expression of the apoptotic markers BAX, BCL2 and SLUG, as well as the keratinocyte markers cytokeratin 14, stratifin and filaggrin. Upon culture, the number of keratinocytes, their viability and secretion of matrix metalloproteinases 1 and 10 were equal in both groups.

CONCLUSION

This study reports the possibility of isolating functioning and viable keratinocytes through a xeno-free workflow for clinical application.

Novel tissue-engineered skin equivalent from recombinant human collagen hydrogel and fibroblasts facilitated full-thickness skin defect repair in a mouse model

Tissue-engineered skin equivalent (TESE) is an optimized alternative for the treatment of skin defects. Designing and fabricating biomaterials with desired properties to load cells is critical for the approach. In this study, we aim to develop a novel TESE with recombinant human collagen (rHC) hydrogel and fibroblasts to improve full-thickness skin defect repair. First, the bioactive effect of rHC on fibroblast proliferation, migration and phenotype was assayed. The results showed that rHC had good biocompatibility and could stimulate fibroblasts migration and secrete various growth factors. Then, rHC was cross-linked with transglutaminase (TG) to prepare rHC hydrogel. Rheometer tests indicated that 10% rHC/TG hydrogel could reach a oscillate stress of 251 Pa and remained stable. Fibroblasts were seeded into rHC/TG hydrogel to prepare TESE. Confocal microscope and scanning electronic microscope observation showed that seeded fibroblasts survived well in the hydrogel. Finally, the therapeutic effect of the newly prepared TESE was tested in a mouse full-thickness skin defect model. The results demonstrated that TESE could significantly improve skin defect repair in vivo. Conclusively, TESE prepared from rHC and fibroblasts in this study exhibits great potential for clinical application in the future.