Stem cells, niches and scaffolds: Applications to burns and wound care

Human keratin matrix in addition to standard of care accelerates healing of venous ulcers: a case series

OBJECTIVE

Venous leg ulcers (VLUs) are often large and complicated wounds that, despite combinations of advanced wound care techniques and systemic treatment of underlying vascular issues, take many months to heal and have high rates of recurrence. In this study, we investigated the efficacy of a novel wound care solution-human keratin matrix (HKM).

METHOD

A case series of VLUs were treated with HKM in conjunction with indicated vascular intervention and standard of care (SoC) procedures. For analysis, these wounds were divided into very large (>200 cm2) and smaller (<35 cm2) wounds.

RESULTS

The cohort comprised 16 VLUs (very large=7; smaller=9). Very large VLUs were reduced in size by an average of 71% within 10 weeks, and showed a 50% size reduction within four applications of HKM. Smaller VLUs reduced by 50% in size within the first three weeks of treatment, and 88.9% of these wounds healed completely with an average of 4.5 HKM applications over an average of 6.5 weeks.

CONCLUSION

The results of this series highlight the potential of HKM, in combination with indicated systemic interventions and SoC, as an effective treatment for hard-to-heal (chronic) VLUs, even in very large wounds.

Harnessing the potential of hydrogels for advanced therapeutic applications: current achievements and future directions

The applications of hydrogels have expanded significantly due to their versatile, highly tunable properties and breakthroughs in biomaterial technologies. In this review, we cover the major achievements and the potential of hydrogels in therapeutic applications, focusing primarily on two areas: emerging cell-based therapies and promising non-cell therapeutic modalities. Within the context of cell therapy, we discuss the capacity of hydrogels to overcome the existing translational challenges faced by mainstream cell therapy paradigms, provide a detailed discussion on the advantages and principal design considerations of hydrogels for boosting the efficacy of cell therapy, as well as list specific examples of their applications in different disease scenarios. We then explore the potential of hydrogels in drug delivery, physical intervention therapies, and other non-cell therapeutic areas (e.g., bioadhesives, artificial tissues, and biosensors), emphasizing their utility beyond mere delivery vehicles. Additionally, we complement our discussion on the latest progress and challenges in the clinical application of hydrogels and outline future research directions, particularly in terms of integration with advanced biomanufacturing technologies. This review aims to present a comprehensive view and critical insights into the design and selection of hydrogels for both cell therapy and non-cell therapies, tailored to meet the therapeutic requirements of diverse diseases and situations.

The Role and Prospects of Mesenchymal Stem Cells in Skin Repair and Regeneration

Mesenchymal stem cells (MSCs) have been recognized as a cell therapy with the potential to promote skin healing. MSCs, with their multipotent differentiation ability, can generate various cells related to wound healing, such as dermal fibroblasts (DFs), endothelial cells, and keratinocytes. In addition, MSCs promote neovascularization, cellular regeneration, and tissue healing through mechanisms including paracrine and autocrine signaling. Due to these characteristics, MSCs have been extensively studied in the context of burn healing and chronic wound repair. Furthermore, during the investigation of MSCs, their unique roles in skin aging and scarless healing have also been discovered. In this review, we summarize the mechanisms by which MSCs promote wound healing and discuss the recent findings from preclinical and clinical studies. We also explore strategies to enhance the therapeutic effects of MSCs. Moreover, we discuss the emerging trend of combining MSCs with tissue engineering techniques, leveraging the advantages of MSCs and tissue engineering materials, such as biodegradable scaffolds and hydrogels, to enhance the skin repair capacity of MSCs. Additionally, we highlight the potential of using paracrine and autocrine characteristics of MSCs to explore cell-free therapies as a future direction in stem cell-based treatments, further demonstrating the clinical and regenerative aesthetic applications of MSCs in skin repair and regeneration.

Marine-derived polysaccharides and their therapeutic potential in wound healing application - A review

Polysaccharides originating from marine sources have been studied as potential material for use in wound dressings because of their desirable characteristics of biocompatibility, biodegradability, and low toxicity. Marine-derived polysaccharides used as wound dressing, provide several benefits such as promoting wound healing by providing a moist environment that facilitates cell migration and proliferation. They can also act as a barrier against external contaminants and provide a protective layer to prevent further damage to the wound. Research studies have shown that marine-derived polysaccharides can be used to develop different types of wound dressings such as hydrogels, films, and fibres. These dressings can be personalised to meet specific requirements based on the type and severity of the wound. For instance, hydrogels can be used for deep wounds to provide a moist environment, while films can be used for superficial wounds to provide a protective barrier. Additionally, these polysaccharides can be modified to improve their properties, such as enhancing their mechanical strength or increasing their ability to release bioactive molecules that can promote wound healing. Overall, marine-derived polysaccharides show great promise for developing effective and safe wound dressings for various wound types.

Applications, opportunities, and challenges in using Telehealth for burn injury management: A systematic review

INTRODUCTION

Burns are global public health devastating and life-threatening injuries. Telehealth can be an appropriate answer for the effective utilization of health care resources, prevention referrals and reduce socio-economic burden of burns injuries. Thus, this study aimed to systematically evaluate the applications, opportunities, and challenges of using telehealth in burn injuries management.

METHODS

A structured search was conducted according to PRISMA statement guidelines in the Web of Science, PubMed, Scopus, and Science Direct as well as the Google Scholar for studies published until June 28, 2022. Of the total 2301 yielded studies, 36 articles were included in the final review. Quality appraisal was done according to the Mixed Methods Appraisal Tool (MMAT) version 2018. Thematic analysis was applied for data analysis.

RESULTS

Patient triage, transfer, and referral (38.9%) follow-up (22%), care (22%), consultation (9%), education (3%), and rehabilitation (3%) were the most prevalent application of telehealth, respectively. Our findings identified 72 unique concepts, eight initial themes, and two clinical and administrative final themes for opportunities of using telehealth in burn injury management. Furthermore, we identified 27 unique concepts, three initial themes, and two clinical and administrative final themes for remaining challenges.

CONCLUSIONS

Despite providing pivotal opportunities such as improving burn injury diagnosis and quality of care, increasing patient and provider satisfaction, and cost containment using telehealth in burn injuries management, the concept faces challenges such as the impossibility of the physical examination of patients and technological difficulties. Our findings provide valuable information for policymakers and decision-makers infield of burn injuries and effective planning for using telehealth technology.

GDF11 promotes wound healing in diabetic mice via stimulating HIF-1ɑ-VEGF/SDF-1ɑ-mediated endothelial progenitor cell mobilization and neovascularization

Non-healing diabetic wounds (DW) are a serious clinical problem that remained poorly understood. We recently found that topical application of growth differentiation factor 11 (GDF11) accelerated skin wound healing in both Type 1 DM (T1DM) and genetically engineered Type 2 diabetic db/db (T2DM) mice. In the present study, we elucidated the cellular and molecular mechanisms underlying the action of GDF11 on healing of small skin wound. Single round-shape full-thickness wound of 5-mm diameter with muscle and bone exposed was made on mouse dorsum using a sterile punch biopsy 7 days following the onset of DM. Recombinant human GDF11 (rGDF11, 50 ng/mL, 10 μL) was topically applied onto the wound area twice a day until epidermal closure (maximum 14 days). Digital images of wound were obtained once a day from D0 to D14 post-wounding. We showed that topical application of GDF11 accelerated the healing of full-thickness skin wounds in both type 1 and type 2 diabetic mice, even after GDF8 (a muscle growth factor) had been silenced. At the cellular level, GDF11 significantly facilitated neovascularization to enhance regeneration of skin tissues by stimulating mobilization, migration and homing of endothelial progenitor cells (EPCs) to the wounded area. At the molecular level, GDF11 greatly increased HIF-1ɑ expression to enhance the activities of VEGF and SDF-1ɑ, thereby neovascularization. We found that endogenous GDF11 level was robustly decreased in skin tissue of diabetic wounds. The specific antibody against GDF11 or silence of GDF11 by siRNA in healthy mice mimicked the non-healing property of diabetic wound. Thus, we demonstrate that GDF11 promotes diabetic wound healing via stimulating endothelial progenitor cells mobilization and neovascularization mediated by HIF-1ɑ-VEGF/SDF-1ɑ pathway. Our results support the potential of GDF11 as a therapeutic agent for non-healing DW.

Substance P&dimethyloxallyl glycine-loaded carboxymethyl chitosan/gelatin hydrogel for wound healing

Recent efforts have focused on preparing drug-loaded hydrogel for wound healing. In order to obtain an ideal hydrogel dressing for skin wound repair, a carboxymethyl chitosan-gelatin hydrogel was prepared for co-delivery of SP (substance P) and DMOG (dimethyloxallyl glycine) by a chemical cross-linking method using genipin as the cross-linking agent. The synthesized hydrogels have good biocompatibility and physicochemical properties due to the low toxicity of the hydrogel material. The three-dimensional network structure of the hydrogels supports cell migration and proliferation, and the combination of SP and DMOG drugs exhibited strong effects on cell proliferation. Moreover, the co-loaded drug hydrogels could significantly promote wound healing in vivo, and provide a potential hydrogel for wound healing.

(Bio)printing in Personalized Medicine—Opportunities and Potential Benefits

The global development of technologies now enters areas related to human health, with a transition from conventional to personalized medicine that is based to a significant extent on (bio)printing. The goal of this article is to review some of the published scientific literature and to highlight the importance and potential benefits of using 3D (bio)printing techniques in contemporary personalized medicine and also to offer future perspectives in this research field. The article is prepared according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Web of Science, PubMed, Scopus, Google Scholar, and ScienceDirect databases were used in the literature search. Six authors independently performed the search, study selection, and data extraction. This review focuses on 3D bio(printing) in personalized medicine and provides a classification of 3D bio(printing) benefits in several categories: overcoming the shortage of organs for transplantation, elimination of problems due to the difference between sexes in organ transplantation, reducing the cases of rejection of transplanted organs, enhancing the survival of patients with transplantation, drug research and development, elimination of genetic/congenital defects in tissues and organs, and surgery planning and medical training for young doctors. In particular, we highlight the benefits of each 3D bio(printing) applications included along with the associated scientific reports from recent literature. In addition, we present an overview of some of the challenges that need to be overcome in the applications of 3D bioprinting in personalized medicine. The reviewed articles lead to the conclusion that bioprinting may be adopted as a revolution in the development of personalized, medicine and it has a huge potential in the near future to become a gold standard in future healthcare in the world.

Rapid culture of human keratinocytes in an autologous, feeder-free system with a novel growth medium

BACKGROUND AIMS

The ability to culture human keratinocytes is beneficial in the treatment of skin injury and disease, as well as for testing chemicals in vitro as a substitute for animal testing.

RESULTS

We have identified a novel culture medium for the rapid growth of keratinocytes from human skin. "Kelch's medium" supports keratinocyte growth that is as rapid as in the classical Rheinwald and Green method, but without the need for cholera toxin or xenogeneic feeder cells. It enables keratinocytes to out-compete co-cultured autologous fibroblasts so that separation of the epidermis from the dermis is no longer required before keratinocyte culture. Enzymatic digests of whole human skin can therefore be used to generate parallel cultures of autologous keratinocytes, fibroblasts and melanocytes simply by using different cell culture media.

CONCLUSIONS

This new keratinocyte medium and the simplified manufacturing procedures it enables are likely to be beneficial in skin engineering, especially for clinical applications.

Bacterial Cellulose-Based Materials as Dressings for Wound Healing

Bacterial cellulose (BC) is produced by several microorganisms as extracellular structures and can be modified by various physicochemical and biological strategies to produce different cellulosic formats. The main advantages of BC for biomedical applications can be summarized thus: easy moldability, purification, and scalability; high biocompatibility; and straightforward tailoring. The presence of a high amount of free hydroxyl residues, linked with water and nanoporous morphology, makes BC polymer an ideal candidate for wound healing. In this frame, acute and chronic wounds, associated with prevalent pathologies, were addressed to find adequate therapeutic strategies. Hence, the main characteristics of different BC structures-such as membranes and films, fibrous and spheroidal, nanocrystals and nanofibers, and different BC blends, as well as recent advances in BC composites with alginate, collagen, chitosan, silk sericin, and some miscellaneous blends-are reported in detail. Moreover, the development of novel antimicrobial BC and drug delivery systems are discussed.

Renewable marine polysaccharides for microenvironment-responsive wound healing

Marine polysaccharides (MPs) are an eco-friendly and renewable resource with a distinctive set of biological functions and are regarded as biological materials that can be in contact with tissues and body fluids for an extended time and promote tissue or organ regeneration. Skin tissue is easily invaded by the external environment due to its softness and large surface area. However, the body's natural physiological healing process is often too slow or suffers from the incomplete restoration of skin structure and function. Functional wound dressings are crucial for skin tissue engineering. Herein, popular MPs from different sources are summarized systematically. In particular, the structure-effectiveness of MP-based wound dressings and the physiological remodeling process of different wounds are reviewed in detail. Finally, the prospect of MP-based smart wound dressings is stated in conjunction with the wound microenvironment and provides new opportunities for high-value biomedical applications of MPs.

Fenugreek Extract-Loaded Polycaprolacton/Cellulose Acetate Nanofibrous Wound Dressings for Transplantation of Unrestricted Somatic Stem Cells: An In Vitro and In Vivo Evaluation

Complex pathophysiology of diabetic wounds causes a delayed wound healing response. Advanced wound dressing materials that deliver biochemical cues are of particular interest in wound healing research. Here, we developed a dual-function delivery vehicle for drug and cell delivery applications to treat diabetic wounds. The delivery system was developed via electrospinning of polycaprolacton/cellulose acetate solution containing fenugreek extract. The produced delivery vehicle was characterized using microstructural studies, cell viability assay, cytoprotection assay, cell migration assay, In Vitro anti-inflammatory assay, free radical scavenging assay, tensile strength studies, swelling studies, and protein adsorption test. Scaffolds were then seeded with 30000 unrestricted somatic stem cells and transplanted into the rat model of excisional diabetic wound. Wound healing assay showed that the co-delivery of fenugreek extract and unrestricted somatic stem cells led to a substantial improvement in the healing activity of electrospun dressings, as evidenced by higher wound contraction, epithelial thickness, and collagen deposition in this group compared with other experimental groups. Gene expression analysis showed that dual-function delivery system could increase the expression level of VEGF, b-FGF, and collagen type II genes. Furthermore, the tissue expression level of IL-1β and glutathione peroxidase genes was significantly reduced in this group compared with other groups. This study shows that the developed system may be considered as a potential treatment modality for diabetic wounds in the clinic.

Rational Design of Intelligent and Multifunctional Dressing to Promote Acute/Chronic Wound Healing

Currently, the clinic's treatment of acute/chronic wounds is still unsatisfactory due to the lack of functional and appropriate wound dressings. Intelligent and multifunctional dressings are considered the most advanced wound treatment modalities. It is essential to design and develop wound dressings with required functions according to the wound microenvironment in the clinical treatment. This work summarizes microenvironment characteristics of various common wounds, such as acute wound, diabetic wound, burns wound, scalded wound, mucosal wound, and ulcers wound. Furthermore, the factors of transformation from acute wounds to chronic wounds were analyzed. Then we focused on summarizing how researchers fully and thoroughly combined the complex microenvironment with modern advanced technology to ensure the usability and value of the dressing, such as photothermal-sensitive dressings, microenvironment dressing (pH-sensitive dressings, ROS-sensitive dressings, and osmotic pressure dressings), hemostatic dressing, guiding tissue regeneration dressing, microneedle dressings, and 3D/4D printing dressings. Finally, the revolutionary development of wound dressings and how to transform the existing advanced functional dressings into clinical needs as soon as possible have carried out a reasonable and meaningful outlook.

Proliferating Stem Cells are Acutely Affected by DNA Damage Induced by Sulfur Mustard

Sulfur mustard (SM), a chemical warfare agent, can form adducts with DNA, RNA, and proteins. Reactions with DNA lead to the formation of both DNA monoadducts and interstrand cross-links, resulting in DNA damage, and is an important component of SM toxicity. Our previous in vivo studies indicated that dividing cells such as hematopoietic stem cells and intestinal villi stem cells seemed to have increased sensitivity to SM. Therefore, to compare the sensitivity of somatic and stem cells to SM and to investigate the mechanism of SM cytotoxicity, we isolated human foreskin fibroblasts, reprogrammed them into pluripotent stem cells, and then compared the DNA damage repair pathways involved upon SM treatment. Our results indicated that proliferating stem cells were more sensitive to SM-induced DNA damage, and the damage mainly comprised single-stranded breaks. Furthermore, the pathways involved in DNA repair in stem cells and somatic cells were different.

Bioactive Materials Promote Wound Healing through Modulation of Cell Behaviors

Skin wound repair is a multistage process involving multiple cellular and molecular interactions, which modulate the cell behaviors and dynamic remodeling of extracellular matrices to maximize regeneration and repair. Consequently, abnormalities in cell functions or pathways inevitably give rise to side effects, such as dysregulated inflammation, hyperplasia of nonmigratory epithelial cells, and lack of response to growth factors, which impedes angiogenesis and fibrosis. These issues may cause delayed wound healing or even non-healing states. Current clinical therapeutic approaches are predominantly dedicated to preventing infections and alleviating topical symptoms rather than addressing the modulation of wound microenvironments to achieve targeted outcomes. Bioactive materials, relying on their chemical, physical, and biological properties or as carriers of bioactive substances, can affect wound microenvironments and promote wound healing at the molecular level. By addressing the mechanisms of wound healing from the perspective of cell behaviors, this review discusses how bioactive materials modulate the microenvironments and cell behaviors within the wounds during the stages of hemostasis, anti-inflammation, tissue regeneration and deposition, and matrix remodeling. A deeper understanding of cell behaviors during wound healing is bound to promote the development of more targeted and efficient bioactive materials for clinical applications.

Mesenchymal stem cells are prospective novel off-the-shelf wound management tools

Chronic/non-healing cutaneous wounds pose a debilitating burden on patients and healthcare system. Presently, treatment modalities are rapidly shifting pace from conventional methods to advanced wound care involving cell-based therapies. Mesenchymal stem cells (MSCs) have come across as a prospective option due to its pleiotropic functions viz. non-immunogenicity, multipotency, multi-lineage plasticity and secretion of growth factors, cytokines, microRNAs (miRNA), exosomes, and microvesicles as part of their secretome for assisting wound healing. We outline the therapeutic role played by MSCs and its secretome in suppressing tissue inflammation, causing immunomodulation, aiding angiogenesis and assisting in scar-free wound healing. We further assess the mechanism of action by which MSCs contribute in manifesting tissue repair. The review flows ahead in exploring factors that influence healing behavior including effect of multiple donor sites, donor age and health status, tissue microenvironment, and in vitro expansion capability. Moving ahead, we overview the advancements achieved in extending the lifespan of cells upon implantation, influence of genetic modifications aimed at altering MSC cargo, and evaluating bioengineered matrix-assisted delivery methods toward faster healing in preclinical and clinical models. We also contribute toward highlighting the challenges faced in commercializing cell-based therapies as standard of care treatment regimens. Finally, we strongly advocate and highlight its application as a futuristic technology for revolutionizing tissue regeneration.

Electrospinning: New Strategies for the Treatment of Skin Melanoma

Recent studies have shown a significant growth of skin cancer cases in northern regions of the world, in which its presence was not common. Skin cancer is one of the cancers that mostly affects the world's population, ranking fifth in studies conducted in the United States (USA). Melanoma is cancer that has the highest number of deaths worldwide since it is the most resistant skin cancer to current treatments. This is why alternatives for its treatment has been investigated considering nanomedicine concepts. This study approaches the role of this field in the creation of promising electrospun devices, composed of nanoparticles and nanofibers, among other structures, capable of directing and/or loading active drugs and/or materials with the objective of inhibiting the growth of melanoma cells or even eliminating those cells.

Biomimetic immunomodulation strategies for effective tissue repair and restoration

Inflammation plays a central role in wound healing following injury or disease and is mediated by a precise cascade of cellular and molecular events. Unresolved inflammatory processes lead to chronic inflammation and fibrosis, which can result in prolonged wound healing lasting months or years that hampers tissue function. Therapeutic interventions mediated by immunomodulatory drugs, cells, or biomaterials, are therefore most effective during the inflammatory phase of wound healing when a pro-regenerative environment is essential. In this review, we discuss the advantages of exploiting knowledge of the native tissue microenvironment to develop therapeutics capable of modulating the immune response and promoting functional tissue repair. In particular, we provide examples of the most recent biomimetic platforms proposed to accomplish this goal, with an emphasis on those able to induce macrophage polarization towards a pro-regenerative phenotype.

The interplay between extracellular matrix and progenitor/stem cells during wound healing: Opportunities and future directions

Skin wound healing, a dynamic physiological process, progresses through coordinated overlapping phases to restore skin integrity. In some pathological conditions such as diabetes, wounds become chronic and hard-to-heal resulting in substantial morbidity and healthcare costs. Despite much advancement in understanding mechanisms of wound healing, chronic and intractable wounds are still a considerable challenge to nations' health care systems. Extracellular matrix (ECM) components play pivotal roles in all phases of wound healing. Therefore, a better understanding of their roles during wound healing can help improve wound care approaches. The ECM provides a 3D structure and forms the stem cell niche to support stem cell adhesion and survival and to regulate stem cell behavior and fate. Also, this dynamic structure reserves growth factors, regulates their bioavailability and provides biological signals. In various diseases, the composition and stiffness of the ECM is altered, which as a result, disrupts bidirectional cell-ECM interactions and tissue regeneration. Hence, due to the impact of ECM changes on stem cell fate during wound healing and the possibility of exploring new strategies to treat chronic wounds through manipulation of these interactions, in this review, we will discuss the importance/impact of ECM in the regulation of stem cell function and behavior to find ideal wound repair and regeneration strategies. We will also shed light on the necessity of using ECM in future wound therapy and highlight the potential roles of various biomimetic and ECM-based scaffolds as functional ECM preparations to mimic the native stem cell niche.

Physically crosslinked PVA/graphene-based materials/aloe vera hydrogel with antibacterial activity

Burn is a major skin injury that occurs worldwide. For second-degree burns, special treatment should be given for creating a suitable wound healing environment. Hydrogel wound dressing as the primary care should possess extra properties that include antibacterial activity and cytocompatibility to enhance the treatment effectiveness. Additional therapy such as electrical stimulation can be applied as well promote wound healing. Herein, we used the tissue engineering concept to create a novel antibacterial and cytocompatible hydrogel made of polyvinyl alcohol (PVA), graphene-based material (GBM), and aloe vera extract (Av) through the freeze-thaw process. We prepared the PVA/GBM/Av hydrogel and examined its potential as a wound dressing. We found that it exhibited excellent hydrophilicity with a contact angle between 15 and 31 degrees and electrical conductivity within the range of 0.0102-0.0154 S m-1, which is comparable to that of the human skin tissue and possesses tensile strength up to 1.5 MPa with elongation of 405%. It also demonstrated good stability in phosphate buffer saline with a weight ratio of 73-80% after 14 days of immersion. We presented that the addition of graphene and graphene oxide (GO) inhibited the growth of Gram-positive Staphylococcus aureus ATCC 6538 with the lowest bacterial population observed in PVA/GO, which is 1.74 × 107 cfu mL-1 after 1 day incubation and 99.94% bacterial reduction. Furthermore, our PVA/GBM/Av showed no toxicity to 3T3 fibroblast cells after 48 h with viability up to 295% for PVA/GO/Av. In summary, our fabricated hydrogels have shown their potential as wound dressing with antibacterial and non-cytotoxic properties.

Molecular Changes Underlying Hypertrophic Scarring Following Burns Involve Specific Deregulations at All Wound Healing Stages (Inflammation, Proliferation and Maturation)

Excessive connective tissue accumulation, a hallmark of hypertrophic scaring, results in progressive deterioration of the structure and function of organs. It can also be seen during tumor growth and other fibroproliferative disorders. These processes result from a wide spectrum of cross-talks between mesenchymal, epithelial and inflammatory/immune cells that have not yet been fully understood. In the present review, we aimed to describe the molecular features of fibroblasts and their interactions with immune and epithelial cells and extracellular matrix. We also compared different types of fibroblasts and their roles in skin repair and regeneration following burn injury. In summary, here we briefly review molecular changes underlying hypertrophic scarring following burns throughout all basic wound healing stages, i.e. during inflammation, proliferation and maturation.

Mesenchymal Stem Cell-derived Extracellular Vesicles for Skin Wound Healing

Skin is vulnerable to various external insults such as burn, severe injury, or inflammation, which necessitates a better strategy for wound repair. Mesenchymal stem cells (MSCs) can self-renew and differentiate into various supporting tissues including cartilage, bone, muscle, and adipose tissue. Along with their unique multipotent capacity, they secrete various paracrine mediators such as growth factors, cytokines, and membrane-enclosed particles called extracellular vesicles (EVs). Herein, we discussed the general traits of EVs such as cell-to-cell communicator, and highlighted the recent preclinical outcomes, with a focus on the application of MSC-derived EVs in wound repair. This chapter provides insights into developing novel strategies for skin wound healing in a cell-free manner.

Proinflammatory cytokines regulate epidermal stem cells in wound epithelialization

The skin, which serves as the first barrier of the human body, is particularly susceptible to exogenous injuries. Skin wounds, including acute burns and chronic non-healing ulcers, are commonly observed in clinics. Healing of skin wounds is a complex process, consisting of infiltration of inflammatory cells, cellular proliferation, and tissue remodeling phases, which restore the integrity and functions of the skin. Epithelialization is involved in wound healing through re-establishing an intact keratinocyte layer. Epidermal stem cells are indispensable for epithelialization, and they are regulated by multiple proinflammatory cytokines or growth factors. In this review, we summarize recent advances in the effect of these cytokines on migration, proliferation, and differentiation processes of epidermal stem cells. We also introduce promising therapeutic strategies targeting epidermal stem cells or related proinflammatory cytokines for patients with skin wounds.

Homing and Engraftment of Intravenously Administered Equine Cord Blood-Derived Multipotent Mesenchymal Stromal Cells to Surgically Created Cutaneous Wound in Horses: A Pilot Project

Limb wounds on horses are often slow to heal and are prone to developing exuberant granulation tissue (EGT) and close primarily through epithelialization, which results in a cosmetically inferior and non-durable repair. In contrast, wounds on the body heal rapidly and primarily through contraction and rarely develop EGT. Intravenous (IV) multipotent mesenchymal stromal cells (MSCs) are promising. They home and engraft to cutaneous wounds and promote healing in laboratory animals, but this has not been demonstrated in horses. Furthermore, the clinical safety of administering >1.00 × 10⁸ allogeneic MSCs IV to a horse has not been determined. A proof-of-principle pilot project was performed with two horses that were administered 1.02 × 10⁸ fluorescently labeled allogeneic cord blood-derived MSCs (CB-MSCs) following wound creation on the forelimb and thorax. Wounds and contralateral non-wounded skin were sequentially biopsied on days 0, 1, 2, 7, 14, and 33 and evaluated with confocal microscopy to determine presence of homing and engraftment. Results confirmed preferential homing and engraftment to wounds with persistence of CB-MSCs at 33 days following wound creation, without clinically adverse reactions to the infusion. The absence of overt adverse reactions allows further studies to determine effects of IV CB-MSCs on equine wound healing.

The Clinical Efficacy of ReCell® Autologous Cell Regeneration Techniques Combined with Dermabrasion Treatment in Acne Scars

OBJECTIVE

To evaluate the efficacy of ReCell® autologous cell regeneration techniques combined with dermabrasion treatment on the therapy of acne scars.

METHODS

We analyzed retrospectively 78 patients with acne scars who presented to the Department of Plastic Surgery at Peking Union Medical College Hospital from May 2015 to May 2017; 30 patients were treated with dermabrasion (Group 1), and the other 48 patients were treated with ReCell® autologous regeneration techniques combined with dermabrasion (Group 2). Efficacy was evaluated through self-evaluation of the patient, third-party evaluation and photographs taken before and after treatment. The wound healing time and postoperative complication rate were also recorded.

RESULTS

The study revealed a significant difference in healing time (P < 0.001) between patients treated with dermabrasion (Group 1) and patients treated with ReCell® autologous regeneration techniques combined with dermabrasion (Group 2). The average healing time of Group 1 was 12.30 ± 1.725 days, while the average healing time of Group 2 was 5.27 ± 1.086 days. In Group 2, patient self-evaluation and third-party evaluation were more satisfactory than those of Group 1 (P < 0.001). Moreover, there were no postoperative complications in Group 2 such as pigmentation and scar hyperplasia.

CONCLUSION

The ReCell® technique is simple, minimally invasive, biocompatible and effective in the treatment of acne scars. It can shorten healing time and reduce the occurrence of postoperative complications, thereby providing a safe and effective treatment approach for patients with facial acne scars.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Extract of Cornus officinalis Protects Keratinocytes from Particulate Matter-induced Oxidative Stress

The skin is one of the large organs in the human body and the most exposed to outdoor contaminants such as particulate matter < 2.5 µm (PM_2.5). Recently, we reported that PM_2.5 induced cellular macromolecule disruption of lipids, proteins, and DNA, via reactive oxygen species, eventually causing cellular apoptosis of human keratinocytes. In this study, the ethanol extract of Cornus officinalis fruit (EECF) showed anti-oxidant effect against PM_2.5-induced cellular oxidative stress. EECF protected cells against PM_2.5-induced DNA damage, lipid peroxidation, and protein carbonylation. PM_2.5 up-regulated intracellular and mitochondrial Ca²⁺ levels excessively, which led to mitochondrial depolarization and cellular apoptosis. However, EECF suppressed the PM_2.5-induced excessive Ca²⁺ accumulation and inhibited apoptosis. The data confirmed that EECF greatly protected human HaCaT keratinocytes from PM_2.5-induced oxidative stress.

The effects of epidermal growth factor on early burn-wound progression in rats

After burns, protecting tissues by medicines in the zone of stasis reduces the width and depth of injury. This study's goal was to reduce burned tissue damage in the zone of stasis using epidermal growth factor (EGF). Forty-eight Wistar rats were separated into three groups. In all groups, the burn procedure was applied following the comb burn model. In Group 1, no postburn treatment was administered. In Group 2, physiological saline solution (0.3 cc) was injected intradermally and in Group 3, EGF (0.3 cc) was injected intradermally into stasis zone tissues after the burn procedure. Surviving tissue rates were 24.0% in Group 1, 25.3% in Group 2, and 70.2% in Group 3. The average numbers of cells stained with Nrf2, HO-1, and the number of apoptotic cells were 230, 150, and 17.5 in Group 1, 230, 145, and 15.0 in Group 2, and 370, 230, and 0 in Group 3, respectively. Values in Group 3 were found to be statistically significantly different than those of Groups 1 and 2; there was no difference between Groups 1 and 2. This study shows that EGF protects zone of stasis tissue from burn damage.

A Critical Update of the Assessment and Acute Management of Patients with Severe Burns

Significance: Burns are debilitating, life threatening, and difficult to assess and manage. Recent advances in assessment and management have occurred since a comprehensive review of the care of patients with severe burns was last published, which may influence research and clinical practice. Recent Advances: Recent advances have occurred in the understanding of burn pathophysiology, which has led to the identification of potential biomarkers of burn severity, such as protein C. There is new evidence about the potential superiority of natural colloids over crystalloids during fluid resuscitation, and new evidence about components of initial and perioperative management, including an improved understanding of pain following burns. Critical Issues: The limitations of the clinical examination highlight the need for imaging and biomarkers to assist in estimations of burn severity. Fluid resuscitation reduces mortality, although there is conjecture over the ideal method. The subsequent perioperative period is associated with significant morbidity and the evidence for preventing and treating pain, infection, and fluid overload while maximizing wound healing potential is described. Future Directions: Promising developments are ongoing in imaging technology, histopathology, biomarkers, and wound healing adjuncts such as hyperbaric oxygen therapy, topical negative pressure therapy, stem cell treatments, and skin substitutes. The greatest benefit from further research on management of patients with burns would most likely be derived from the elucidation of optimal fluid resuscitation protocols, pain management protocols, and surgical techniques from randomized controlled trials.

Combining ECM Hydrogels of Cardiac Bioactivity with Stem Cells of High Cardiomyogenic Potential for Myocardial Repair

Tissue engineering exploring the combination of scaffolds and seeding cells was proposed as a promising strategy for myocardial repair. However, the therapeutic outcomes varied greatly due to different selection of scaffolds and seeding cells. Herein, the potential of combining bioactive extracellular matrix (ECM) hydrogels and high cardiomyogenic seeding cells was explored for myocardial repair in vitro and in vivo. Temperature-sensitive ECM hydrogels were prepared from decellularized rat hearts, and cardiomyogenic seeding cells were isolated from brown adipose (brown adipose-derived stem cells (BADSCs)). The in vitro studies demonstrated that ECM hydrogel significantly supported the proliferation and cardiomyogenic differentiation of BADSCs. Importantly, the function and maturation of BADSC-derived cardiomyocytes were also promoted as evidenced by Ca²⁺ transient's measurement and protein marker expression. After myocardial transplantation, the combination of BADSCs and ECM hydrogels significantly preserved cardiac function and chamber geometry compared with BADSCs or ECM hydrogels alone. Meanwhile, the ECM hydrogel also enhanced BADSC engraftment and myocardial regeneration in vivo. These results indicated that heart-derived ECM hydrogels exerted significant influence on the fate of cardiomyogenic cells toward benefiting myocardial repair, which may explain the enhanced stem cell therapy by the scaffold. Collectively, it indicated that the combination of ECM hydrogel and the cardiomyogenic cells may represent a promising strategy for cardiac tissue engineering.

Human amniotic mesenchymal stem cells and their paracrine factors promote wound healing by inhibiting heat stress-induced skin cell apoptosis and enhancing their proliferation through activating PI3K/AKT signaling pathway

Background

Increasing evidence has shown that mesenchymal stem cells (MSCs) yield a favorable therapeutic benefit for thermal burn skin wounds. Human amniotic MSCs (hAMSCs) derived from amniotic membrane have multilineage differentiation, immunosuppressive, and anti-inflammatory potential which makes them suitable for treating skin wounds. However, the exact effects of hAMSCs on the healing of thermal burn skin wounds and their potential mechanisms are not explored.

Methods

hAMSCs were isolated from amniotic membrane and characterized by RT-PCR, flow cytometry, immunofluorescence, and tumorigenicity test. We assessed the effects of hAMSCs and hAMSC conditional medium (CM) on wound healing in a deep second-degree burn injury model of mice. We then investigated the biological effects of hAMSCs and hAMSC-CM on the apoptosis and proliferation of heat stress-injured human keratinocytes HaCAT and dermal fibroblasts (DFL) both in vivo and in vitro. Next, we explored the underlying mechanisms by assessing PI3K/AKT and GSK3β/β-catenin signaling pathways in heat injured HaCAT and DFL cells after hAMSCs and hAMSC-CM treatments using PI3K inhibitor LY294002 and β-catenin inhibitor ICG001. Antibody array assay was used to identify the cytokines secreted by hAMSCs that may activate PI3K/AKT signaling pathway.

Results

Our results showed that hAMSCs expressed various markers of embryonic stem cells and mesenchymal stem cells and have low immunogenicity and no tumorigenicity. hAMSC and hAMSC-CM transplantation significantly promoted thermal burn wound healing by accelerating re-epithelialization with increased expression of CK19 and PCNA in vivo. hAMSCs and hAMSC-CM markedly inhibited heat stress-induced apoptosis in HaCAT and DFL cells in vitro through activation of PI3K/AKT signaling and promoted their proliferation by activating GSK3β/β-catenin signaling. Furthermore, we demonstrated that hAMSC-mediated activation of GSK3β/β-catenin signaling was dependent on PI3K/AKT signaling pathway. Antibody array assay showed that a panel of cytokines including PAI-1, C-GSF, periostin, and TIMP-1 delivered from hAMSCs may contribute to the improvement of the wound healing through activating PI3K/AKT signaling pathway.

Conclusion

Our results demonstrated that hAMSCs and hAMSC-CM efficiently cure heat stress-induced skin injury by inhibiting apoptosis of skin cells and promoting their proliferation through activating PI3K/AKT signaling pathway, suggesting that hAMSCs and hAMSC-CM may provide an alternative therapeutic approach for the treatment of skin injury.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1366-y) contains supplementary material, which is available to authorized users.

Re-epithelialization of adult skin wounds: Cellular mechanisms and therapeutic strategies

Cutaneous wound healing in adult mammals is a complex multi-step process involving overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodelling. Re-epithelialization describes the resurfacing of a wound with new epithelium. The cellular and molecular processes involved in the initiation, maintenance, and completion of epithelialization are essential for successful wound closure. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here, we focus on cellular mechanisms underlying keratinocyte migration and proliferation during epidermal closure. Inability to re-epithelialize is a clear indicator of chronic non-healing wounds, which fail to proceed through the normal phases of wound healing in an orderly and timely manner. This review summarizes the current knowledge regarding the management and treatment of acute and chronic wounds, with a focus on re-epithelialization, offering some insights into novel future therapies.

Plasma-Coated Polycaprolactone Nanofibers with Covalently Bonded Platelet-Rich Plasma Enhance Adhesion and Growth of Human Fibroblasts

Biodegradable nanofibers are extensively employed in different areas of biology and medicine, particularly in tissue engineering. The electrospun polycaprolactone (PCL) nanofibers are attracting growing interest due to their good mechanical properties and a low-cost structure similar to the extracellular matrix. However, the unmodified PCL nanofibers exhibit an inert surface, hindering cell adhesion and negatively affecting their further fate. The employment of PCL nanofibrous scaffolds for wound healing requires a certain modification of the PCL surface. In this work, the morphology of PCL nanofibers is optimized by the careful tuning of electrospinning parameters. It is shown that the modification of the PCL nanofibers with the COOH plasma polymers and the subsequent binding of NH2 groups of protein molecules is a rather simple and technologically accessible procedure allowing the adhesion, early spreading, and growth of human fibroblasts to be boosted. The behavior of fibroblasts on the modified PCL surface was found to be very different when compared to the previously studied cultivation of mesenchymal stem cells on the PCL nanofibrous meshes. It is demonstrated by X-ray photoelectron spectroscopy (XPS) that the freeze-thawed platelet-rich plasma (PRP) immobilization can be performed via covalent and non-covalent bonding and that it does not affect biological activity. The covalently bound components of PRP considerably reduce the fibroblast apoptosis and increase the cell proliferation in comparison to the unmodified PCL nanofibers or the PCL nanofibers with non-covalent bonding of PRP. The reported research findings reveal the potential of PCL matrices for application in tissue engineering, while the plasma modification with COOH groups and their subsequent covalent binding with proteins expand this potential even further. The use of such matrices with covalently immobilized PRP for wound healing leads to prolonged biological activity of the immobilized molecules and protects these biomolecules from the aggressive media of the wound.

Novel pharmacotherapy for burn wounds: what are the advancements

INTRODUCTION

The prognosis for severe burns has improved significantly over the past 50 years. Meanwhile, burns have become an affliction mainly affecting the less well-developed regions of the world. Early excision and skin grafting has led to major improvements in therapeutic outcomes.

AREAS COVERED

The purpose of this article is to survey the use of pharmacotherapy to treat different pathophysiological complications of burn injury. The author, herein, discusses the use of drug treatments for a number of systemic metabolic disturbances including hyperglycemia, elevated catabolism, and gluconeogenesis.

EXPERT OPINION

Advancements in personalized and molecular medicine will make an impact on burn therapy. Similarities between severe burns and other critically ill patients will lead to cross-fertilization between different medical specialties. Furthermore, advances in stem cells and tissue regeneration will lead to improved healing and less lifelong disability. Indeed, research in new drug therapy for burns is actively progressing for many different complications.

Comparative effectiveness of Biobrane®, RECELL® Autologous skin Cell suspension and Silver dressings in partial thickness paediatric burns: BRACS randomised trial protocol

BACKGROUND

Mixed partial thickness burns are the most common depth of burn injury managed at a large Australian paediatric hospital specialty burns unit. Prolonged time until re-epithelialisation is associated with increased burn depth and scar formation. Whilst current wound management approaches have benefits such as anti-microbial cover, these are not without inherent limitations including multiple dressing changes. The Biobrane® RECELL® Autologous skin Cell suspension and Silver dressings (BRACS) trial aims to identify the most effective wound management approach for mixed partial thickness injuries in children.

METHODS

All children presenting with an acute burn injury to the study site will be screened for eligibility. This is a single-centre, three-arm, parallel group, randomised trial. Children younger than 16 years, with burns ≥ 5% total body surface area involving any anatomical location, up to 48 h after the burn injury, and of a superficial partial to mid-dermal depth, will be included. A sample size of 84 participants will be randomised to standard silver dressing or a Regenerative Epithelial Suspension (RES™) with Biobrane® or Biobrane® alone. The first dressing will be applied under general anaesthesia and subsequent dressings will be changed every 3 to 5 days until the wound is ≥ 95% re-epithelialised, with re-epithelialisation time the primary outcome. Secondary outcomes of acute pain, acute itch, scar severity, health-related quality of life, treatment satisfaction, dressing application ease and healthcare resource use will be assessed at each dressing change and 3, 6 and 12 months post-burn injury.

DISCUSSION

The findings of this study can potentially change the wound management approach for superficial partial to mid-dermal burns in children locally and worldwide.

TRIAL REGISTRATION

The Australian New Zealand Clinical Trials Registry (ACTRN12618000245291) approved prospective registration on 15 February 2018. Registration details can be viewed at https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=374272&isReview=true.

Stem cells in burn wound healing: A systematic review of the literature

INTRODUCTION

Severe burns are often associated with high morbidity and unsatisfactory functional and esthetic outcomes. Over the last two decades, stem cells have generated great hopes for the treatment of numerous conditions including burns. The aim of this systematic review is to evaluate the role of stem cell therapy as a means to promote burn wound healing.

METHODS

Comprehensive searches in major databases were carried out in March 2017 for articles on stem cell therapy in burn wound healing. In total 2103 articles were identified and screened on the basis of pre-determined inclusion and exclusion criteria.

RESULTS

Fifteen experimental and two clinical studies were included in the review. The majority of studies reported significant improvement in macroscopic burn wound appearance as well as a trend toward improved microscopic appearance, after stem cell therapy. Other parameters evaluated, such as re-vascularization, collagen formation, level of pro- and anti-inflammatory mediators, apoptosis and cellular infiltrates, yielded heterogeneous results across studies.

CONCLUSION

Stem cell therapy appears to exert a positive effect in burn wound healing. There is, therefore, justification for continued efforts to evaluate the use of stem cells as an adjunct to first-line therapies in burns.

Preclinical assessment of safety and efficacy of intravenous delivery of autologous adipose-derived regenerative cells (ADRCs) in the treatment of severe thermal burns using a porcine model

OBJECTIVE

A number of studies have reported that application of autologous adipose-derived cell populations leads to improved outcome in different preclinical models of thermal burn injury. However, these studies were limited to assessment of relatively small injuries amounting to only ∼2% of total body surface area (TBSA) in which the complications associated with large burns (e.g.: systemic inflammation and the need for fluid resuscitation) are absent. In anticipation of translating this approach to a clinical trial in which these complications would be present we applied a preclinical model that more closely resembles a patient with large thermal burn injury requiring skin grafting. Thus, the present study used a porcine model to investigate safety and efficacy of intravenous delivery of ADRCs in the treatment of a complex burn injury comprising ∼20% TBSA and including both moderately deep (44%) partial and full thickness burns, and the injury associated with skin graft harvest.

METHODS

Two pairs of full thickness and partial thickness burns involving in total ∼20% TBSA were created on the back of Yorkshire pigs (n=15). Three days post-burn, full thickness wounds were excised and grafted with a 3:1 meshed autologous split thickness skin graft (STSG). Partial thickness wounds were not treated other than with dressings. Animals were then randomized to receive intravenous delivery of ADRCs (n=8) or vehicle control (n=7). Safety was assessed by monitoring systemic parameters (blood gases, hematology, and clinical chemistry) throughout the course of the study. Wound healing for both types of burn wound and for the skin graft donor sites was followed for 18days using wound imaging, histology, and trans-epidermal water loss (TEWL; skin barrier function assessment).

RESULTS

No serious adverse events related to ADRC infusion were noted in any of the animals. Delivery of ADRCs appeared to be safe with none of the systemic safety parameters worsened compared to the control group. TEWL and histological analyses revealed that ADRC treatment was associated with significantly accelerated healing of skin graft (27.1% vs. 1.1% on Day 5 post-grafting), donor site (52.8% vs. 33.1% on Day 5 post-excision) and partial thickness burn (81.8% vs. 59.8% on Day 18 post-treatment). Data also suggested that ADRC treatment improved parameters associated with skin graft elasticity.

CONCLUSIONS

This study demonstrated that intravenous delivery of autologous ADRCs appears to be a safe and feasible approach to the treatment of large burns and supports the use of ADRCs as an adjunct therapy to skin grafting in patients with severe burns.

Three-dimensional reconstructed eccrine sweat glands with vascularization and cholinergic and adrenergic innervation

Functional integrity of the regenerated tissues requires not only structural integrity but also vascularization and innervation. We previously demonstrated that the three-dimensional (3D) reconstructed eccrine sweat glands had similar structures as those of the native ones did, but whether the 3D reconstructed glands possessing vascularization and innervation was still unknown. In the study, Matrigel-embedded eccrine sweat gland cells were implanted under the inguinal skin. Ten weeks post-implantation, the vascularization, and innervation in the 10-week reconstructed eccrine sweat glands and native human eccrine sweat glands were detected by immunofluorescence staining. The results showed that the fluorescent signals of general neuronal marker protein gene product 9.5, adrenergic nerve fiber marker tyrosine hydroxylase, and cholinergic nerve fiber markers acetylcholinesterase and vasoactive intestinal peptide embraced the 3D reconstructed glands in circular patterns, as the signals appeared in native eccrine sweat glands. There were many CD31- and von Willebrand factor-positive vessels growing into the plugs. We demonstrated that the 3D reconstructed eccrine sweat glands were nourished by blood vessels, and we for the first time demonstrated that the engineering sweat glands were innervated by both cholinergic and adrenergic fibers. In conclusion, the 3D reconstructed eccrine sweat glands may have functions as the native ones do.