Cutaneous wound healing

MiR-494-3p regulates skin fibroblast activities by mediating fibromodulin production

Skin wound healing is a well-coordinated process in which various cells and factors participate, during which fibroblast exhibits a critical role by exerting its multiple activities, including proliferation, migration, invasion, and differentiation. Previous studies have identified that fibromodulin (FMOD) could enhance dermal wound healing by promoting skin fibroblast activities, but little is known about its upstream regulator. We occasionally found that FMOD expression was downregulated in skin fibroblast by transforming growth factor-β1 treatment. It was hypothesized that microRNAs (miRNA) in skin fibroblast could downregulate FMOD production and blocking them would increase FMOD expression, as well as promote skin wound healing. Here, by utilizing combined analysis of miRNA microarray from the Gene Expression Omnibus database and miRNA targets prediction, we successfully identified a miRNA, termed miR-494-3p, could regulate FMOD production in human skin fibroblast (BJ fibroblast). The functional analysis revealed that miR-494-3p mimics could inhibit BJ fibroblast migration and invasion but not proliferation and differentiation, while miR-494-3p inhibition markedly promotes migration, invasion, and differentiation of BJ fibroblast. Moreover, we established FMOD overexpression (OE) and knockout BJ fibroblast. We found that FMOD OE could rescue the inhibitory effects of miR-494-3p mimics on the migration and invasion of BJ fibroblast. In contrast, the miR-494-3p inhibitor transfection could not enhance migration, invasion, and differentiation of FMOD KO BJ fibroblast. Together, our results suggest that miR-494-3p may be a potential target for skin wound management via regulating FMOD production.

Topical delivery of insulin using novel organogel formulations: An approach for the management of diabetic wounds

Diabetes mellitus is a growing chronic form of diabetes, with lengthy health implications. It is predicted as poor diabetic wound recovery affects roughly 25% of all diabetes mellitus patients, frequently resulting in lower traumatic injury and severe external factors and emotional expenses. The insulin-resistant condition increases biofilm development, making diabetic wounds harder to treat. Nowadays, medical treatment and management of diabetic wounds, which have a significant amputation rate, a high-frequency rate, and a high death rate, have become a global concern. Topical formulations have played a significant part in diabetic wound management and have been developed to achieve a number of features. Because of its significant biocompatibility, moisture retention, and therapeutic qualities, topical insulin has emerged as an appealing and feasible wound healing process effector. With a greater comprehension of the etiology of diabetic wounds, numerous functionalized topical insulins have been described and shown good outcomes in recent years, which has improved some diabetic injuries. The healing of wounds is a physiological phenomenon that restores skin integrity and heals damaged tissues. Insulin, a powerful wound-healing factor, is also used in several experimental and clinical studies accelerate healing of diverse injuries.

Tetrahedral framework nucleic acids for improving wound healing

Wounds are one of the most common health issues, and the cost of wound care and healing has continued to increase over the past decade. In recent years, there has been growing interest in developing innovative strategies to enhance the efficacy of wound healing. Tetrahedral framework nucleic acids (tFNAs) have emerged as a promising tool for wound healing applications due to their unique structural and functional properties. Therefore, it is of great significance to summarize the applications of tFNAs for wound healing. This review article provides a comprehensive overview of the potential of tFNAs as a novel therapeutic approach for wound healing. In this review, we discuss the possible mechanisms of tFNAs in wound healing and highlight the role of tFNAs in modulating key processes involved in wound healing, such as cell proliferation and migration, angiogenesis, and tissue regeneration. The targeted delivery and controlled release capabilities of tFNAs offer advantages in terms of localized and sustained delivery of therapeutic agents to the wound site. In addition, the latest research progress on tFNAs in wound healing is systematically introduced. We also discuss the biocompatibility and biosafety of tFNAs, along with their potential applications and future directions for research. Finally, the current challenges and prospects of tFNAs are briefly discussed to promote wider applications.

Sucralfate Prevents Pin Site Infections of External Fixators in Open Tibia Fractures

Pin site infections are the main complication of external fixators. The most common pathogens are Staphylococcus epidermidis and Staphylococcus aureus. The incidence of pin site infections ranges from 2% to 30%. Until now, no satisfactory prevention strategy exists. Therefore, we performed this study to assess the effect of a sucralfate gel 25% applied around the pins of external fixation systems in trauma patients with open tibia fractures. We prospectively studied two groups of patients with open tibia fractures treated with external fixators. In group A patients, pin site care was performed with the use of normal saline and plain dressings once a day. In group B patients, pin site care was performed with the use of sucralfate gel 25%. The incidence of pin site infections was 33.33% for patients of group A and 16.67% for patients of group B. Patients of group B showed significantly lower rate of pin site infections compared to patients of group A (p-value = 0.032). No patient experienced any complications related to the local application of the drug. Sucralfate significantly prevents pin site infections of external fixators in open tibia fractures. Therefore, it can be used as a preventive antimicrobial agent for pin site infections in patients with external fixators.

Artificial Skin Therapies; Strategy for Product Development

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

Designing a Biomaterial Approach to Control the Adaptive Response to a Skin Injury

The goal of this review is to explain how to design a biomaterial approach to control the adaptive response to injury, with an emphasis on skin wounds. The strategies will be selected based on whether they have a reasonable probability of meeting the desired clinical outcome vs. just comparing the pros and cons of different strategies. To do this, the review will look at the normal adaptive response in adults and why it does not meet the desired clinical outcome in most cases. In addition, the adaptive response will be looked at in cases where it does meet the clinical performance requirements including animals that regenerate and for fetal wound healing. This will lead to how biomaterials can be used to alter the overall adaptive response to allow it to meet the desired clinical outcome. The important message of the review is that you need to use the engineering design process, not the scientific method, to design a clinical treatment. Also, the clinical performance requirements are functional, not structural. The last section will give some specific examples of controlling the adaptive response for two skin injuries: burns and pressure ulcers. For burns, it will cover some preclinical studies used to justify a clinical study as well as discuss the results of a clinical study using this system. For pressure ulcers, it will cover some preclinical studies for two different approaches: electrical stimulation and degradable/regenerative scaffolds. For electrical stimulation, the results of a clinical study will be presented.

Cinnamaldehyde-Based Self-Nanoemulsion (CA-SNEDDS) Accelerates Wound Healing and Exerts Antimicrobial, Antioxidant, and Anti-Inflammatory Effects in Rats’ Skin Burn Model

Cinnamaldehyde, the main phytoconstituent of the cinnamon oil, has been reported for its potential wound healing activity, associated to its antimicrobial and anti-inflammatory effects. In this study, we are reporting on the cinnamaldehyde-based self-nanoemulsifying drug delivery system (CA-SNEDDS), which was prepared and evaluated for its antimicrobial, antioxidant, anti-inflammatory, and wound healing potential using the rat third-degree skin injury model. The parameters, i.e., skin healing, proinflammatory, and oxidative/antioxidant markers, were evaluated after 3 weeks of treatment regimens with CA-SNEDDS. Twenty rats were divided randomly into negative control (untreated), SNEDDS control, silver sulfadiazine cream positive control (SS), and CA-SNEDDS groups. An aluminum cylinder (120 °C, 10-s duration) was used to induce 3rd-degree skin burns (1-inch square diameter each) on the rat’s dorsum. At the end of the experiment, skin biopsies were collected for biochemical analysis. The significantly reduced wound size in CA-SNEDDS compared to the negative group was observed. CA-SNEDDS-treated and SS-treated groups demonstrated significantly increased antioxidant biomarkers, i.e., superoxide dismutase (SOD) and catalase (CAT), and a significant reduction in the inflammatory marker, i.e., NAP-3, compared to the negative group. Compared to SNEDDS, CA-SNEDDS exhibited a substantial antimicrobial activity against all the tested organisms at the given dosage of 20 µL/disc. Among all the tested microorganisms, MRSA and S. typhimurium were the most susceptible bacteria, with an inhibition zone diameter (IZD) of 17.0 ± 0.3 mm and 19.0 ± 0.9 mm, respectively. CA-SNEDDS also exhibited strong antifungal activity against C. albicans and A. niger, with IZD of 35.0 ± 0.5 mm and 34.0 ± 0.5 mm, respectively. MIC and MBC of CA-SNEDDS for the tested bacteria ranged from 3.125 to 6.25 µL/mL and 6.25 to 12.5 µL/mL, respectively, while the MIC and MBC for C. albicans and A. niger were 1.56 µL/mL and 3.125 µL/mL, respectively. The MBIC and MBEC of CA-SNEDDS were also very significant for the tested bacteria and ranged from 6.25 to 12.5 µL/mL and 12.5 to 25.0 µL/mL, respectively, while the MBIC and MBEC for C. albicans and A. niger were 3.125 µL/mL and 6.25 µL/mL, respectively. Thus, the results indicated that CA-SNEDDS exhibited significant wound healing properties, which appeared to be attributed to the formulation’s antimicrobial, antioxidant, and anti-inflammatory effects.

Studying the in vivo application of a liquid dermal scaffold in promoting wound healing in a mouse model

Lack of matrix deposition is one of the main factors that complicates the healing process of wounds. The aim of this study was to test the efficacy and safety of a liquid dermal scaffold, referred to as MeshFill (MF) that can fill the complex network of tunnels and cavities which are usually found in chronic wounds and hence improve the healing process. We evaluated in vitro and in vivo properties of a novel liquid dermal scaffold in a delayed murine full-thickness wound model. We also compared this scaffold with two commercially available granular collagen-based products (GCBP). Liquid dermal scaffold accelerated wound closure significantly compared with no-treated control and collagen-based injectable composites in a delayed splinted wound model. When we compared cellular composition and count between MF, no treatment and GCBP at the histology level, it was found that MF was the most analogous and consistent with the normal anatomy of the skin. These findings were matched with the clinical outcome observation. The flowable in situ forming scaffold is liquid at cold temperature and gels after application to the wound site. Therefore, it would conform to the topography of the wound when liquid and provides adequate tensile strength when solidified. This patient-ready gelling dermal scaffold also contains the nutritional ingredients and therefore supports cell growth. Applying an injectable liquid scaffold that can fill wound gaps and generate a matrix to promote keratinocytes and fibroblasts migration, can result in improvement of the healing process of complex wounds.

Corilagin alleviates hypertrophic scars via inhibiting the transforming growth factor (TGF)-β/Smad signal pathway

AIMS

Exploring the effects of corilagin on hypertrophic scar (HS) and its underlying mechanisms.

MAIN METHODS

Human HS-derived fibroblasts (HSFs) were isolated and treated with corilagin. To investigate the effects of corilagin on HSFs, quantitative real time polymerase chain reaction (qRT-PCR), western blotting, wound healing, and immunofluorescence assays were performed. These effects were confirmed in a rabbit ear scar model by histological and immunohistochemical studies. Lastly, western blot assay was performed to detect the protein levels of several components of the transforming growth factor (TGF)-β/Smad signaling pathway, as well as the protein levels of matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs).

KEY FINDINGS

Corilagin showed multiple effects on HSFs, including does-dependent inhibition of collagen production, cell proliferation, and migration, besides suppression of the activation of HSFs. Moreover, corilagin suppressed HS formation and collagen deposition in a rabbit ear scar model. Corilagin also inhibited fibroblast proliferation and α-smooth muscle actin (α-SMA) expression in vivo. Finally, western blot analysis revealed that corilagin downregulated the protein levels of TGF-β1 and TGF-β receptor type I (TGFβRI), thus lowering the level of p-smad2/3, also affected the protein levels of MMPs and TIMP1.

SIGNIFICANCE

Corilagin could be a potential agent for HS treatment through the inhibition of extracellular matrix (ECM) deposition and multiple functions of fibroblasts.

An on-chip wound healing assay fabricated by xurography for evaluation of dermal fibroblast cell migration and wound closure

Dermal fibroblast cell migration is a key process in a physiological wound healing. Therefore, the analysis of cell migration is crucial for wound healing research. In this study, lab-on-a-chip technology was used to investigate the effects of basic fibroblast growth factor (bFGF), mitomycin C (MMC), MEK1/2 inhibitor (U0126) and fetal calf serum (FCS) on human dermal fibroblast cell migration. The microdevice was fabricated consisting of microchannels, pneumatic lines and pneumatically-activated actuators by xurographic rapid prototyping. In contrast to current approaches in in vitro wound healing such as scratch assays and silicone inserts in wellplate format, which show high variability and poor reproducibility, the current system aims to automate the wounding procedure at high precision and reproducibility using lab-on-a-chip. Traumatic wounding was simulated on-chip on fibroblast cell monolayers by applying air pressure on the flexible circular membrane actuator. Wound closure was monitored using light microscopy and cell migration was evaluated using image analysis. The pneumatically controlled system generates highly reproducible wound sizes compared to the conventional wound healing assay. As proof-of-principle study wound healing was investigated in the presence of several stimulatory and inhibitory substances and culture including bFGF, MMC, U0126 MEK1/2 inhibitor as well as serum starvation to demonstrate the broad applicability of the proposed miniaturized culture microsystem.

Bioactive ECM Mimic Hyaluronic Acid Dressing via Sustained Releasing of bFGF for Enhancing Skin Wound Healing

Successful dermal wound regeneration requires the coordination of repair cells and cellular signals with the extracellular matrix (ECM), which serves as an indispensable mechanical and biological supporter for cell functions and communications with varied cytokines during healing processes. Here, we developed an injectable bioactive wound dressing, methacrylated hyaluronic acid (Me-HA)-based hydrogel loading with basic fibroblast growth factor (bFGF), endowing the dressing with the pleiotropic bioactivity to mimic natural ECM. This bFGF@Me-HA dressing was applied to a mouse with full-thickness excisional wounds to investigate its positive roles in wound repair owing to the complementary functions of HA with sustained release of bioactive bFGF. Compared with the single Me-HA and bFGF group, bFGF@Me-HA hydrogel dressings significantly enhanced wound healing with accelerated re-epithelialization, granulation formation, collagen, deposition and skin appendage regeneration. Further investigations showed significantly promoted cell proliferation and vascularization in the bFGF@Me-HA group, which was mediated by the upregulation of transforming growth factor-β (TGF-β) and vascular endothelial growth factor (VEGF) expressions. In conclusion, this bFGF@Me-HA hydrogel realized the optimization of simple ECM mimic dressing via introducing the bioactive effector, bFGF, and has the potential to be widely used as an effective bioactive ECM-based wound dressing in future wound care.

Knockout of E2F1 enhances the polarization of M2 phenotype macrophages to accelerate the wound healing process

Wound healing is a complex process, which is classically divided into inflammation, proliferation, and remodeling phases. Macrophages play a key role in wound healing, however, whether E2F1 mediates the M1/M2 polarization during the wound healing process is not known. Skin wounds were surgically induced in E2F1^-/- mice and their WT littermates. At day 2 and day 7 post-surgery, the wounded skin tissues including 2 to 3 mm normal skin were obtained. The wounded skin tissues were used for the analyses of immunofluorescence staining (CD68, iNOS, CD206), western blotting (CD68, iNOS, CD206, PPAR-γ) and Co-immunoprecipitation (E2F1-PPAR-γ interactions). E2F1^-/- mice exhibited faster wound healing process. At day 2, the M2 macrophages were remarkably increased in the E2F1^-/- mice. Surprisingly, in the border zone of the wound, E2F1^-/- mice had also more M2 macrophages and fewer M1 macrophages at day 7 post-surgery, suggesting a certain degree of polarization amongst the M1 and M2 phenotypes. Co-IP revealed that E2F1 indeed interacted with PPAR-γ, meanwhile western blotting and RT-PCR showed higher expression of PPAR-γ in the E2F1^-/- mice as compared to that in the WT mice. Therefore, the findings suggest that wound healing process could be accelerated with enhanced M2 polarization through increased PPAR-γ expression in E2F1 knockout mice.

Small Leucine-Rich Proteoglycans in Skin Wound Healing

Healing of cutaneous wounds is a complex and well-coordinated process requiring cooperation among multiple cells from different lineages and delicately orchestrated signaling transduction of a diversity of growth factors, cytokines, and extracellular matrix (ECM) at the wound site. Most skin wound healing in adults is imperfect, characterized by scar formation which results in significant functional and psychological sequelae. Thus, the reconstruction of the damaged skin to its original state is of concern to doctors and scientists. Beyond the traditional treatments such as corticosteroid injection and radiation therapy, several growth factors or cytokines-based anti-scarring products are being or have been tested in clinical trials to optimize skin wound healing. Unfortunately, all have been unsatisfactory to date. Currently, accumulating evidence suggests that the ECM not only functions as the structural component of the tissue but also actively modulates signal transduction and regulates cellular behaviors, and thus, ECM should be considered as an alternative target for wound management pharmacotherapy. Of particular interest are small leucine-rich proteoglycans (SLRPs), a group of the ECM, which exist in a wide range of connecting tissues, including the skin. This manuscript summarizes the most current knowledge of SLRPs regarding their spatial-temporal expression in the skin, as well as lessons learned from the genetically modified animal models simulating human skin pathologies. In this review, particular focus is given on the diverse roles of SLRP in skin wound healing, such as anti-inflammation, pro-angiogenesis, pro-migration, pro-contraction, and orchestrate transforming growth factor (TGF)β signal transduction, since cumulative investigations have indicated their therapeutic potential on reducing scar formation in cutaneous wounds. By conducting this review, we intend to gain insight into the potential application of SLRPs in cutaneous wound healing management which may pave the way for the development of a new generation of pharmaceuticals to benefit the patients suffering from skin wounds and their sequelae.

Adipose tissue-derived mesenchymal stem cells and keratinocytes co-culture on gelatin/chitosan/β-glycerol phosphate nanoscaffold in skin regeneration

Using cell-based engineered skin is an emerging strategy for treating difficult-to-heal wounds. To date, much endeavor has been devoted to the fabrication of appropriate scaffolds with suitable biomechanical properties to support cell viability and growth in the microenvironment of a wound. The aim of this research was to assess the impact of adipose tissue-derived mesenchymal stem cells (AD-MSCs) and keratinocytes on gelatin/chitosan/β-glycerol phosphate (GCGP) nanoscaffold in full-thickness excisional skin wound healing of rats. For this purpose, AD-MSCs and keratinocytes were isolated from rats and GCGP nanoscaffolds were electrospun. Through an in vivo study, the percentage of wound closure was assessed on days 7, 14, and 21 after wound induction. Samples were taken from the wound sites in order to evaluate the density of collagen fibers and vessels at 7 and 14 days. Moreover, sampling was done on days 7 and 14 from wound sites to assess the density of collagen fibers and vessels. The wound closure rate was significantly increased in the keratinocytes-AD-MSCs-scaffold (KMS) group compared with other groups. The expressions of vascular endothelial growth factor, collagen type 1, and CD34 were also significantly higher in the KMS group compared with the other groups. These results suggest that the combination of AD-MSCs and keratinocytes seeded onto GCGP nanoscaffold provides a promising treatment for wound healing.

Kartogenin and Its Application in Regenerative Medicine

Regenerative medicine refers to the possibility of replacing aged/damaged cells with genetically similar young and functional cells to restore or establish normal function. Kartogenin (KGN), a small heterocyclic, drug-like compound was discovered in 2012, which is strongly associated with regenerative medicine. KGN has been applied in many regenerative fields, including cartilage regeneration and protection, tendon-bone healing, wound healing, and limb development. KGN could facilitate cartilage repair, promote formation of cartilage-like transition zone in tendon-bone junctions, stimulate collagen synthesis for wound healing, and regulate limb development in a coordinated manner. Considering the related mechanism, filamin A/CBFβ/RUNX1, Ihh, and TGFβ/Smad pathways have been reported to involve KGN. Therefore, KGN is proven a promising agent in regenerative medicine; however, studies conducted on the effect of KGN are limited to date and not convictive for long-term use. Further studies are recommended to explore the long-term effect and potential molecular mechanisms of KGN. Our investigations may motivate researchers to expand its applications in different forms and fields.

Biomaterial Enhanced Regeneration Design Research for Skin and Load Bearing Applications

Biomaterial enhanced regeneration (BER) falls mostly under the broad heading of Tissue Engineering: the use of materials (synthetic and natural) usually in conjunction with cells (both native and genetically modified as well as stem cells) and/or biological response modifiers (growth factors and cytokines as well as other stimuli, which alter cellular activity). Although the emphasis is on the biomaterial as a scaffold it is also the use of additive bioactivity to enhance the healing and regenerative properties of the scaffold. Enhancing regeneration is both moving more toward regeneration but also speeding up the process. The review covers principles of design for BER as well as strategies to select the best designs. This is first general design principles, followed by types of design options, and then specific strategies for applications in skin and load bearing applications. The last section, surveys current clinical practice (for skin and load bearing applications) including limitations of these approaches. This is followed by future directions with an attempt to prioritize strategies. Although the review is geared toward design optimization, prioritization also includes the commercializability of the devices. This means a device must meet both the clinical performance design constraints as well as the commercializability design constraints.

Fibrin as a Tissue Adhesive and Scaffold with an Angiogenic Agent (FGF-1) to Enhance Burn Graft Healing In Vivo and Clinically

There is a need for a strategy to reduce scarring in meshed skin graft healing leading to a better cosmetic result without a significant increase in cost. The strategy in this paper is to increase the closure rate of a meshed skin graft to reduce scarring, which should also decrease the infection rate. Specifically, we used fibrin glue to attach all parts of the graft to the wound bed and added in an angiogenic growth factor and made the fibrin porous to further help the growth of blood vessels from the wound bed into the graft. There was a 10-day animal study and a one-month clinical study. Neither making the fibrin porous or adding an angiogenic agent (i.e., fibroblast growth factor-1 (FGF-1)) seemed to make a significant improvement in vivo or clinically. The use of fibrin on a meshed skin graft appears to speed up the regenerative healing rate leading to less scarring in the holes in the mesh. It appears to shorten the healing time by five days and keep the tissue stiffness close to normal levels vs. the doubling of the stiffness by the controls. A larger clinical study, however, is needed to definitively prove this benefit as well as the mechanism for this improvement.

Burn Wound Healing and Tissue Engineering

In 2016 the American Burn Association held a State of the Science conference to help identify burn research priorities for the next decade. The current paper summarizes the work of the sub-committee on Burn Wound Healing and Tissue Engineering. We first present the priorities in wound healing research over the next 10 years. We then summarize the current state of the science related to burn wound healing and tissue engineering including determination of burn depth, limiting burn injury progression, eschar removal, management of microbial contamination and wound infection, measuring wound closure, accelerating wound healing and durable wound closure, and skin substitutes and tissue engineering. Finally, a summary of the round table discussion is presented.

A multi-walled silk fibroin/silk sericin nerve conduit coated with poly(lactic-co-glycolic acid) sheath for peripheral nerve regeneration

The linearly oriented multi-walled silk fibroin/silk sericin (SF/SS) nerve conduits (NCs) can provide physical cues similar to native peripheral nerve fasciculi, but the mechanical properties of which are not excellent enough. In this study, NCs with a novel and bionic design with dual structures were developed. The important features of our NCs is that the internal skeleton (the multi-walled SF/SS conduits) has a bionic structure similar to the architecture of native peripheral nerve fasciculi, which is beneficial for nerve regeneration, and the outer sheath (the hollow poly(lactic-co-glycolic acid) [PLGA] conduits) could provide strong mechanical protection for the internal skeleton. The linearly oriented multi-walled SF/SS conduit was fabricated and inserted in the hollow PLGA sheath lumen and then used for the bridge across the sciatic nerve defect in rats. The outcome of the peripheral nerve repair post implantation was evaluated. The functional and morphological parameters were examined and showed that the novel PLGA-coated SF/SS NCs could promote peripheral nerve regeneration, approaching those elicited by nerve autografts that are the first candidate for repair of peripheral nerve defects. Thus, these updated NCs have potential usefulness to enhance functional recovery after repair of peripheral nerve defect.

Interim pressure garment therapy (4-6 mmHg) and its effect on donor site healing in burn patients: study protocol for a randomised controlled trial

Background

Pressure garment therapy (PGT) is well accepted and commonly used by clinicians in the treatment of burns scars and grafts. The medium to high pressures (24–40 mmHg) in these garments can support scar minimisation, and evidence is well documented for this particular application. However, PGT specifically for burn donor sites, of which a sequela is also scarring, is not well documented. This study protocol investigates the impact of a low pressure (4–6 mmHg) interim garment on donor site healing and scarring. With a primary purpose of holding donor dressings in place, the application of the interim pressure garment (IPG) appears to have been twofold. IPGs for donor sites have involved inconsistent application with a focus on securing wound dressing rather than scar management. However, anecdotal and observational evidence suggests that IPGs also make a difference to some patient’s scar outcomes for donor sites. This study protocol outlines a randomised controlled trial designed to test the effectiveness of this treatment on reducing scarring to burn donor sites.

Methods/design

This study is a single-centre, single (assessor)-blinded, randomised control trial in patients with burns donor sites to their thighs. Patients will be randomly allocated to a control group (with no compression to donor sites) or to an experimental group (with compression to donor sites) as the comparative treatment. Groups will be compared at baseline regarding the important prognostic indicators: donor site location, depth, size, age, and time since graft (5 days). The IPG treatment will be administered post-operatively (on day 5). Follow-up assessments and garment replacement will be undertaken fortnightly for a period of 2 months.

Discussion

This study focuses on a unique area of burns scar management using a low-pressure tubular support garment for the reduction of donor site scars. Such therapy specifically for donor scar management is poorly represented in the literature. This study was designed to test a potentially cost-effective scar prevention for patients with donor sites to the thigh. No known studies of this nature have been carried out to date, and there is a need for rigorous clinical evidence for low-pressure support garments for donor site scar minimisation.

Trial registration

Australian New Zealand Clinical Trials Registry identifier ACTRN12610000127000. Registered 8 Mar 2010.

Proteoglycans in Normal and Healing Skin

Significance: Proteoglycans have a distinct spatial localization in normal skin and are essential for the correct structural development, organization, hydration, and functional properties of this tissue. The extracellular matrix (ECM) is no longer considered to be just an inert supportive material but is a source of directive, spatial and temporal, contextual information to the cells via components such as the proteoglycans. There is a pressing need to improve our understanding of how these important molecules functionally interact with other matrix structures, cells and cellular mediators in normal skin and during wound healing. Recent Advances: New antibodies to glycosaminoglycan side chain components of skin proteoglycans have facilitated the elucidation of detailed localization patterns within skin. Other studies have revealed important proliferative activities of proteinase-generated fragments of proteoglycans and other ECM components (matricryptins). Knockout mice have further established the functional importance of skin proteoglycans in the assembly and homeostasis of the normal skin ECM. Critical Issues: Our comprehension of the molecular and structural complexity of skin as a complex, dynamic, constantly renewing, layered connective tissue is incomplete. The impact of changes in proteoglycans on skin pathology and the wound healing process is recognized as an important area of pathobiology and is an area of intense investigation. Future Directions: Advanced technology is allowing the development of new artificial skins. Recent knowledge on skin proteoglycans can be used to incorporate these molecules into useful adjunct therapies for wound healing and for maintenance of optimal tissue homeostasis in aging skin.

Accelerated healing of cutaneous wounds using phytochemically stabilized gold nanoparticle deposited hydrocolloid membranes

Rapid healing of dermatological wounds is of vital importance in preventing infection and reducing post-treatment side-effects.

The characteristics of bacterial nanocellulose gel releasing silk sericin for facial treatment

BACKGROUND

Recently, naturally derived facial masks with beneficial biological properties have received increasing interest. In this study, silk sericin-releasing bacterial nanocellulose gel was developed to be applied as a bioactive mask for facial treatment.

RESULTS

The silk sericin-releasing bacterial nanocellulose gel produced at a pH of 4.5 had an ultrafine and extremely pure fiber network structure. The mechanical properties and moisture absorption ability of the gel were improved, compared to those of the commercially available paper mask. Silk sericin could be control-released from the gel. A peel test with porcine skin showed that the gel was less adhesive than the commercially available paper mask, which would be removed from the face more easily without pain. The in vitro cytotoxicity test showed that the gel was not toxic to L929 mouse fibroblast and HaCaT human keratinocyte cells. Furthermore, when implanted subcutaneously and evaluated according to ISO10993-6 standard, the gel was not irritant to tissue.

CONCLUSION

The silk sericin-releasing bacterial nanocellulose gel had appropriate physical and biological properties and safety for the facial treatment application.

Skin regeneration: the complexities of translation into clinical practise

The integration of engineering into biological science has resulted in the capacity to provide tissue engineered solutions for tissue damage. Skin regeneration remains the goal of skin repair to reduce the long term consequences of scarring to the individual. A scar is abnormal in its architecture, chemistry and cell phenotype, tissue engineering of scaffolds and cells opens up the potential of tissue regeneration into the future. Tissue engineering solutions have been applied to skin many decades despite technical success the clinical application has been modest. To realise the potential of the developing technologies needs alignment of not only the science and engineering but also the commercial upscaling of production in a safe and regulated framework for clinical use. In addition the education and training for the introduction of new technology within the health system is essential, bringing together the technology and systems for utilisation to optimise the patient outcome. This article is part of a Directed Issue entitled: Regenerative Medicine: The challenge of translation.

Anchoring a cytoactive factor in a wound bed promotes healing

Wound healing is a complex process that requires the intervention of cytoactive factors. The one-time application of soluble factors to a wound bed does not maintain a steady, sufficient concentration. Here we investigated the benefits of anchoring a factor in a wound bed via a tether to endogenous collagen. We used a collagen-mimetic peptide (CMP) as a pylon. The CMP binds to damaged but not intact collagen and thus localizes a pendant cytoactive factor in the regions of a wound bed that require intervention. As a model factor, we chose substance P, a peptide of the tachykinin family that promotes wound healing. Using splinted wounds in db/db mice, we found that the one-time application of a CMP-substance P conjugate enhances wound healing compared to unconjugated substance P and other controls. Specifically, all 16 wounds treated with the conjugate closed more thoroughly and, did so with extensive re-epithelialization and mitigated inflammatory activity. These data validate a simple and general strategy for re-engineering wound beds by the integration of beneficial cytoactive factors. Copyright © 2014 John Wiley & Sons, Ltd.

Preliminary characterization of genipin-cross-linked silk sericin/poly(vinyl alcohol) films as two-dimensional wound dressings for the healing of superficial wounds

The genipin-cross-linked silk sericin/poly(vinyl alcohol) (PVA) films were developed aiming to be applied as two-dimensional wound dressings for the treatment of superficial wounds. The effects of genipin cross-linking concentration on the physical and biological properties of the films were investigated. The genipin-cross-linked silk sericin/PVA films showed the increased surface density, tensile strength, and percentage of elongation, but decreased percentage of light transmission, water vapor transmission rate, and water swelling, compared to the non-cross-linked films. This explained that the cross-linking bonds between genipin and silk sericin would reduce the mobility of molecular chains within the films, resulting in the more rigid molecular structure. Silk sericin was released from the genipin-cross-linked films in a sustained manner. In addition, either L929 mouse fibroblast or HaCat keratinocyte cells showed high percentage of viability when cultured on the silk sericin/PVA films cross-linked with 0.075 and 0.1% w/v genipin. The in vivo safety test performed according to ISO 10993-6 confirmed that the genipin-cross-linked silk sericin/PVA films were safe for the medical usages. The efficacy of the films for the treatment of superficial skin wounds will be further investigated in vivo and clinically. The genipin-cross-linked silk sericin/PVA films would be promising choices of two-dimensional wound dressings for the treatment of superficial wounds.

An electrospun scaffold integrating nucleic acid delivery for treatment of full-thickness wounds

We developed a multi-functional construct capable of controlled delivery of bioactive substances that can improve wound repair by supporting the intrinsic ability of the skin to heal. We synthesized electrospun scaffolds-composed of a blend of the degradable polymers poly(l-lactide) (PLA) or polycaprolactone (PCL)-that produce highly efficient non-viral in vivo gene delivery to cells in the wound bed, provide a protective barrier during early wound healing, and support cell migration and growth. This multi-functional material was tested for its influence on wound healing: scaffolds were loaded with plasmids encoding keratinocyte growth factor (KGF) and applied to full-thickness wounds in mice. Compared to scaffolds with control plasmids, animals receiving the KGF plasmid-loaded scaffold produced significant enhancements in wound healing, which was quantified by improvements in the rate of wound re-epithelialization, keratinocyte proliferation, and granulation response. Further, we quantified the expression level of endogenous and plasmid-derived KGF in wound samples: qRT-PCR on wound sections revealed a correlation between the levels of plasmid-derived protein expression and histological analysis of wound healing, revealing an inverse relationship between the expression level of exogenous KGF and the size of the unhealed epithelial layer in wounds. Our findings suggest that engineered nanofiber PLA/PCL scaffolds are capable of highly efficient controlled DNA delivery and are promising materials for treatment of cutaneous wounds.

Development of ethyl alcohol-precipitated silk sericin/polyvinyl alcohol scaffolds for accelerated healing of full-thickness wounds

Silk sericin has been recently reported for its advantageous biological properties to promote wound healing. In this study, we established that the ethyl alcohol (EtOH) could be used to precipitate sericin and form the stable sericin/polyvinyl alcohol (PVA) scaffolds without the crosslinking. The sericin/PVA scaffolds were fabricated via freeze-drying and subsequently precipitating in various concentrations of EtOH. The EtOH-precipitated sericin/PVA scaffolds showed denser structure, higher compressive modulus, but lower water swelling ability than the non-precipitated scaffolds. Sericin could be released from the EtOH-precipitated sericin/PVA scaffolds in a sustained manner. After cultured with L929 mouse fibroblasts, the 70 vol% EtOH-precipitated sericin/PVA scaffolds showed the highest potential to promote cell proliferation. After applied to the full-thickness wounds of rats, the 70 vol% EtOH-precipitated sericin/PVA scaffolds showed significantly higher percentage of wound size reduction and higher extent of type III collagen formation and epithelialization, compared with the control scaffolds without sericin. The accelerated wound healing by the 70 vol% EtOH-precipitated sericin/PVA scaffolds was possibly due to (1) the bioactivity of sericin itself to promote wound healing, (2) the sustained release of precipitated sericin from the scaffolds, and (3) the activation and recruitment of wound healing-macrophages by sericin to the wounds. This finding suggested that the EtOH-precipitated sericin/PVA scaffolds were more effective for the wound healing, comparing with the EtOH-precipitated PVA scaffolds without sericin.

Local delivery of nitric oxide: targeted delivery of therapeutics to bone and connective tissues

Non-invasive treatment of injuries and disorders affecting bone and connective tissue remains a significant challenge facing the medical community. A treatment route that has recently been proposed is nitric oxide (NO) therapy. Nitric oxide plays several important roles in physiology with many conditions lacking adequate levels of NO. As NO is a radical, localized delivery via NO donors is essential to promoting biological activity. Herein, we review current literature related to therapeutic NO delivery in the treatment of bone, skin and tendon repair.

Mobilised bone marrow-derived cells accelerate wound healing

Massive skin defects caused by severe burn and trauma are a clinical challenge to surgeons. Timely and effective wound closure is often hindered by the lack of skin donor site. Bone marrow-derived cells (BMDCs) have been shown to 'differentiate' into multiple tissue cells. In this study we focused on the direct manipulation of endogenous BMDCs, avoiding the immunocompatibility issues and complicated cell isolation, purification, identification and amplification procedures in vitro on wound repair. We found that mobilisation of the BMDCs into the circulation significantly increased the amount of BMDCs at the injury site which in turn accelerated healing of large open wound. We used a chimeric green fluorescent protein (GFP) mouse model to track BMDCs and to investigate their role in full-thickness skin excisional wounds. We have shown that bone marrow mobilisation by granulocyte colony stimulating factor (G-CSF) exerted multiple beneficial effects on skin repair, both by increasing the engraftment of BMDCs into the skin to differentiate into multiple skin cell types and by upregulating essential cytokine mRNAs critical to wound repair. The potential trophic effects of G-CSF on bone marrow stem cells to accelerate wound healing could have a significant clinical impact.

The effect of nano-scale topography on keratinocyte phenotype and wound healing following burn injury

Topographic modulation of tissue response is an important consideration in the design and manufacture of a biomaterial. In developing new tissue therapies for skin, all levels of architecture, including the nanoscale need to be considered. Here we show that keratinocyte phenotype is affected by nanoscale changes in topography with cell morphology, proliferation, and migration influenced by the pore size in anodic aluminum oxide membranes. A membrane with a pore size of 300 nm, which enhanced cell phenotype in vitro, was used as a dressing to cover a partial thickness burn injury in the pig. Wounds dressed with the membrane showed evidence of advanced healing with significantly less organizing granulation tissue and more mature epidermal layers than control wounds dressed with a standard burns dressing. The results demonstrate the importance of nanoscale topography in modulating keratinocyte phenotype and skin wound healing.

Comparison of healing parameters in porcine full-thickness wounds transplanted with skin micrografts, split-thickness skin grafts, and cultured keratinocytes

BACKGROUND

Transplantation of skin micrografts (MGs), split-thickness skin grafts (STSGs), or cultured autologous keratinocytes (CKs) enhances the healing of large full-thickness wounds. This study compares these methods in a porcine wound model, investigating the utility of micrograft transplantation in skin restoration.

STUDY DESIGN

Full-thickness wounds were created on Yorkshire pigs and assigned to one of the following treatment groups: MGs, STSGs, CKs, wet nontransplanted, or dry nontransplanted. Dry wounds were covered with gauze and the other groups' wounds were enclosed in a polyurethane chamber containing saline. Biopsies were collected 6, 12, and 18 days after wounding. Quantitative and qualitative wound healing parameters including macroscopic scar appearance, wound contraction, neoepidermal maturation, rete ridge formation, granulation tissue thickness and width, and scar tissue formation were studied.

RESULTS

Transplanted wounds scored lower on the Vancouver Scar Scale compared with nontransplanted wounds, indicating a better healing outcome. All transplanted wounds exhibited significantly lower contraction compared with nontransplanted wounds. Wounds transplanted with either MGs, STSGs, or CKs showed a significant increase in re-epithelialization compared with nontransplanted wounds. Wounds transplanted with MGs or STSGs exhibited improved epidermal healing compared with nongrafted wounds. Furthermore, transplantation with STSGs or MGs led to less scar tissue formation compared with the nontransplanted wounds. No significant impact on scar formation was observed after transplantation of CKs.

CONCLUSIONS

Qualitative and quantitative measurements collected from full-thickness porcine wounds show that transplantation of MGs improve wound healing parameters and is comparable to treatment with STSGs.

The effect of a self-assembling peptide nanofiber scaffold (peptide) when used as a wound dressing for the treatment of deep second degree burns in rats

RADARADARADARADA (RADA16-I) peptide, consisting of 16 alternating hydrophobic and hydrophilic (also alternating negative and positive charges) amino acids, forms extremely stable beta-pleated sheet structure and then self-assembles into nanofibers to produce high-order interwoven nanofiber scaffold hydrogel. To investigate its therapeutic effects, a burn model of partial thickness-deep dermal injury (the deep second degree burns) was performed at the dorsal skin of female Sprague-Dawley rats with an electrical scalding machine. The wounds treated with either RADA16-I or control materials were carefully examined at morphological, histological and cellular levels. We found that RADA16-I can advance the time of eschar appearance and the time of eschar disappearance both by 3-5 days, and speed up wound contraction by 20-30% compared with contrast groups (chitosan, poly(DL)-lactic acid (PDLA), collagen I and the blank) without obvious edema. Immunohistochemical studies showed that both FGF and EGF were obviously expressed in nascent tissue such as epidermis and glands when wounds were treated with the RADA16-I after injury. When peptide stock solution was diluted from 10 to 0.17 mg/mL, atomic force microscopy (AFM) observation showed that the shape of peptide nanofibers changed from the globular-pieces-clustered filaments with 4.8 +/- 0.38 nm in height, 61.6 +/- 6.10 nm in width and 708 +/- 80.2 nm in length, to general filaments with 1.4 +/- 0.36 nm, 17.5 +/- 1.13 nm and 1108 +/- 184 nm. The nanofiber surface porosity gradually decreased from 49-70% to 12-28%. These characteristics contribute to wound healing by offering an "ideal dressing" moist healing microenvironment and a nanofiber 3D scaffold. These results suggest that the self-assembling peptide might be a promising wound dressing with being simple, effective, and affordable.

Memory encoded throughout our bodies: molecular and cellular basis of tissue regeneration

When a sheep loses its tail, it cannot regenerate it in the manner of lizards. On the other hand, it is possible to clone mammals from somatic cells, showing that a complete developmental program is intact in a wounded sheep's tail the same way it is in a lizard. Thus, there is a requirement for more than only the presence of the entire genetic code in somatic cells for regenerative abilities. Thoughts like this have motivated us to assemble more than just a factographic synopsis on tissue regeneration. As a model, we review skin wound healing in chronological order, and when possible, we use that overview as a framework to point out possible mechanisms of how damaged tissues can restore their original structure. This article postulates the existence of tissue structural memory as a complex distributed homeostatic mechanism. We support such an idea by referring to an extremely fragmented literature base, trying to synthesize a broad picture of important principles of how tissues and organs may store information about their own structure for the purposes of regeneration. Selected developmental, surgical, and tissue engineering aspects are presented and discussed in the light of recent findings in the field. When a sheep loses its tail, it cannot regenerate it in the manner of lizards. On the other hand, it is possible to clone mammals from somatic cells, showing that a complete developmental program is intact in a wounded sheep's tail the same way it is in a lizard. Thus, there is a requirement for more than only the presence of the entire genetic code in somatic cells for regenerative abilities. Thoughts like this have motivated us to assemble more than just a factographic synopsis on tissue regeneration. As a model, we review skin wound healing in chronological order, and when possible, we use that overview as a framework to point out possible mechanisms of how damaged tissues can restore their original structure. This article postulates the existence of tissue structural memory as a complex distributed homeostatic mechanism. We support such an idea by referring to an extremely fragmented literature base, trying to synthesize a broad picture of important principles of how tissues and organs may store information about their own structure for the purposes of regeneration. Selected developmental, surgical, and tissue engineering aspects are presented and discussed in the light of recent findings in the field.