Mechanical offloading of incisional wounds is associated with transcriptional downregulation of inflammatory pathways in a large animal model

Novel design and development of Centella Asiatica extract - loaded poloxamer/ZnO nanocomposite wound closure material to improve anti-bacterial action and enhanced wound healing efficacy in diabetic foot ulcer

Diabetic wounds can occur as a prevalent complication among people diagnosed with diabetes, frequently resulting in the necessity for amputation. The cause and effect of diabetic foot ulcer is complex, involving multiple factors. In the present study, wound healing strategies utilizing nanomaterials have proven to be effective in battling bacterial infections and improve wound regeneration. Poloxamers (PLX) exhibit extensive potential as a viable option for the development of nanomedicines owing to their inherent characteristics of self-assembly and encapsulation. This study aims to design and develop a PLX/ZnO nanocomposite incorporated with Centella Asiatica extract (CAE) for the multi-functional action in the diabetic wound healing treatment. Subsequently physico-chemical characterizations, such as XRD, FTIR, and TEM observations, demonstrated that the ZnO were evenly distributed through the PLX framework. The developed nanocomposite was biocompatible with mouse fibroblast cell line (L929), and it had multiple beneficial characteristics, such as a rapid self-healing process and effective antibacterial action against G+ and G- bacterial pathogens. After being treated with the developed formulation, skin fibroblast cell line and HUVECs demonstrated a substantial increase in their in vitro cell proliferation ability, migration, and tube-forming abilities. The utilization of a CAE@PLX/ZnO nanoformulation presents a viable strategy and a distinctive, encouraging composite for diabetic wound healing treatment.

A versatile natural gelatin-based hydrogel for emergency wound treatment through hemostasis, antibacterial, and anti-inflammation

Emergency wounds are often accompanied by bacterial infection, oxidative stress, and excessive inflammation due to the inability to quickly close and stop bleeding, resulting in chronic wounds that are difficult to heal. Clinically, surgical suturing is the fastest method for wound closure, but it is only suitable for wounds with small bleeding volumes and causes unsightly scar formation. Consequently, there is a critical need for hemostatic dressings versatile enough to address a spectrum of diverse and intricate wounds, especially in emergency scenarios. In this study, we constructed a unique versatile natural gelatin-based hydrogel with hemostasis, antibacterial, and anti-inflammation properties. The hydrogel was composed of 4-(4-(hydroxymethyl)-2-methoxy-5-nitrophenoxy) butyrylethylenediamine-modified methacrylated gelatin (GelMA-NB) and epigallocatechin gallate-grafted polylysine (EPL-EGCG), which imparts adhesion, antibacterial and antioxidant properties to the hydrogel. Simultaneously, the hydrogel was loaded with GelMA microspheres encapsulating natural resveratrol (RES@GM). This combination not only exhibited outstanding hemostatic capabilities but also preserved the anti-inflammatory potential of RES. In different animal models, the hydrogel exhibited outstanding hemostatic and wound healing effects, down-regulated the expression of IL-1βto promote inflammatory regulation and potential for angiogenesis and anti-scar. In conclusion, unique versatile natural gelatin-based hydrogel suitable for various complex wounds provides a promising strategy for emergency wound dressing applications.

Postoperative Mechanomodulation Decreases T-Junction Dehiscence After Reduction Mammaplasty: Early Scar Analysis From a Randomized Controlled Trial

BACKGROUND

Soft tissue and cutaneous tension is an important contributor to complicated wound healing and poor scar cosmesis after surgery and its mitigation is a key consideration in aesthetic and reconstructive procedures.

OBJECTIVES

The study objective was to assess the efficacy of the force modulating tissue bridge (FMTB) ("Brijjit", Brijjit Medical Inc., Atlanta, GA) in reducing mechanical tension on postoperative wounds.

METHODS

A prospective, single-center, randomized, within-subject clinical trial was conducted to evaluate wound healing and nascent scar formation after 8 weeks of postoperative wound support with the FMTB. Patients received standard of care (SOC) subcuticular closure on the vertical incision of 1 breast and experimental closure with the FMTB on the contralateral incision after Wise-pattern reduction mammaplasty. Three-dimensional wound analysis and rates of T-junction dehiscence were evaluated by clinical assessment at 2, 4, 6, and 8 weeks postsurgery.

RESULTS

Thirty-four patients (n = 68 breasts) completed 8 weeks of postoperative FMTB application. There was a reduced rate of T-junction wound dehiscence in FMTB breasts (n = 1) vs SOC breasts (n = 11) (P < .01). The mean vertical incision wound area during the intervention period was significantly decreased in the FMTB breast (1.5 cm2) vs the SOC breast (2.1 cm2) (P < .01) and was significantly lower at 2-, 4-, and 8-week follow-up (P < .01). Only the closure method was significantly associated with variations in Week 8 wound area (P < .01) after linear regression modeling.

CONCLUSIONS

FMTBs decrease nascent scar dimensions and reduce the occurrence of wound dehiscence. This study provides evidence that the use of continuous mechanomodulation significantly reduces postoperative wound complications after skin closure.

LEVEL OF EVIDENCE: 2

Treatment and Improvement of Healing after Surgical Intervention

The development of abnormal scars has a great impact on people's well-being, and improving scarring outcomes after surgery is a field that currently lacks consensus. This review aims to identify newly researched approaches to improving the quality of surgical scars. A systematic search of PubMed, Scopus, Web of Science, and ScienceDirect was conducted between 13 May 2023 and 17 May 2023, in accordance with the recommendations of the PRISMA Statement. Study selection and analysis of methodological quality were performed in parts, independently and blindly, based on eligibility criteria. The 21 prospective, comparative, and randomized studies reviewed included 1057 subjects and studied approaches such as topical applications of creams with herbal extracts and silicone gels, growth factors, negative pressure dressings, oligonucleotides, intralesional injection of compounds such as botulinum toxin, skin closure techniques such as suturing and tissue adhesive, and laser treatments. There are recent research techniques that generate good results and are really promising to improve the results of surgical scars; however, the available evidence is extremely limited in some cases, and it is necessary to deepen its analysis to obtain reliable action protocols in each type of surgery.

Mechano-biological and bio-mechanical pathways in cutaneous wound healing

Injuries to the skin heal through coordinated action of fibroblast-mediated extracellular matrix (ECM) deposition, ECM remodeling, and wound contraction. Defects involving the dermis result in fibrotic scars featuring increased stiffness and altered collagen content and organization. Although computational models are crucial to unravel the underlying biochemical and biophysical mechanisms, simulations of the evolving wound biomechanics are seldom benchmarked against measurements. Here, we leverage recent quantifications of local tissue stiffness in murine wounds to refine a previously-proposed systems-mechanobiological finite-element model. Fibroblasts are considered as the main cell type involved in ECM remodeling and wound contraction. Tissue rebuilding is coordinated by the release and diffusion of a cytokine wave, e.g. TGF-β, itself developed in response to an earlier inflammatory signal triggered by platelet aggregation. We calibrate a model of the evolving wound biomechanics through a custom-developed hierarchical Bayesian inverse analysis procedure. Further calibration is based on published biochemical and morphological murine wound healing data over a 21-day healing period. The calibrated model recapitulates the temporal evolution of: inflammatory signal, fibroblast infiltration, collagen buildup, and wound contraction. Moreover, it enables in silico hypothesis testing, which we explore by: (i) quantifying the alteration of wound contraction profiles corresponding to the measured variability in local wound stiffness; (ii) proposing alternative constitutive links connecting the dynamics of the biochemical fields to the evolving mechanical properties; (iii) discussing the plausibility of a stretch- vs. stiffness-mediated mechanobiological coupling. Ultimately, our model challenges the current understanding of wound biomechanics and mechanobiology, beside offering a versatile tool to explore and eventually control scar fibrosis after injury.

In Vitro, Ex Vivo, and In Vivo Approaches for Investigation of Skin Scarring: Human and Animal Models

Significance: The cutaneous repair process naturally results in different types of scarring that are classified as normal or pathological. Affected individuals are often affected from an esthetic, physical (functional), and psychosocial perspective. The distinct nature of scarring in humans, particularly the formation of pathological scars, makes the study of skin scarring a challenge for researchers in this area. Several established experimental models exist for studying scar formation. However, the increasing development and validation of newly emerging models have made it possible to carry out studies focused on different variables that influence this unique process. Recent Advances: Experimental models such as in vitro, ex vivo, and in vivo models have obtained different degrees of success in the reproduction of the scar formation in its native milieu and true environment. These models also differ in their ability to elucidate the molecular, cellular, and structural mechanisms involved in scarring, as well as for testing new agents and approaches for therapies. The models reviewed here, including cells derived from human skin and in vivo animal models, have contributed to the advancement of skin scarring research. Critical Issues and Future Directions: The absence of experimental models that faithfully reproduce the typical characteristics of the different types of human skin scars makes the improvement of validated models and the establishment of new ones a critical unmet need. The fields of wound healing research combined with tissue engineering have offered newer alternatives for experimental studies with the potential to provide clinically useful knowledge about scar formation.

Advantages and Disadvantages of Using Small and Large Animals in Burn Research: Proceedings of the 2021 Research Special Interest Group

Multiple animal species and approaches have been used for modeling different aspects of burn care, with some strategies considered more appropriate or translatable than others. On April 15, 2021, the Research Special Interest Group of the American Burn Association held a virtual session as part of the agenda for the annual meeting. The session was set up as a pro/con debate on the use of small versus large animals for application to four important aspects of burn pathophysiology: burn healing/conversion; scarring; inhalation injury; and sepsis. For each of these topics, 2 experienced investigators (one each for small and large animal models) described the advantages and disadvantages of using these preclinical models. The use of swine as a large animal model was a common theme due to anatomic similarities with human skin. The exception to this was a well-defined ovine model of inhalation injury; both of these species have larger airways which allow for incorporation of clinical tools such as bronchoscopes. However, these models are expensive and demanding from labor and resource standpoints. Various strategies have been implemented to make the more inexpensive rodent models appropriate for answering specific questions of interest in burns. Moreover, modelling burn-sepsis in large animals has proven difficult. It was agreed that the use of both small and large animal models have merit for answering basic questions about the responses to burn injury. Expert opinion and the ensuing lively conversations are summarized herein, which we hope will help inform experimental design of future research.

Disrupting mechanotransduction decreases fibrosis and contracture in split-thickness skin grafting

Burns and other traumatic injuries represent a substantial biomedical burden. The current standard of care for deep injuries is autologous split-thickness skin grafting (STSG), which frequently results in contractures, abnormal pigmentation, and loss of biomechanical function. Currently, there are no effective therapies that can prevent fibrosis and contracture after STSG. Here, we have developed a clinically relevant porcine model of STSG and comprehensively characterized porcine cell populations involved in healing with single-cell resolution. We identified an up-regulation of proinflammatory and mechanotransduction signaling pathways in standard STSGs. Blocking mechanotransduction with a small-molecule focal adhesion kinase (FAK) inhibitor promoted healing, reduced contracture, mitigated scar formation, restored collagen architecture, and ultimately improved graft biomechanical properties. Acute mechanotransduction blockade up-regulated myeloid CXCL10-mediated anti-inflammation with decreased CXCL14-mediated myeloid and fibroblast recruitment. At later time points, mechanical signaling shifted fibroblasts toward profibrotic differentiation fates, and disruption of mechanotransduction modulated mesenchymal fibroblast differentiation states to block those responses, instead driving fibroblasts toward proregenerative, adipogenic states similar to unwounded skin. We then confirmed these two diverging fibroblast transcriptional trajectories in human skin, human scar, and a three-dimensional organotypic model of human skin. Together, pharmacological blockade of mechanotransduction markedly improved large animal healing after STSG by promoting both early, anti-inflammatory and late, regenerative transcriptional programs, resulting in healed tissue similar to unwounded skin. FAK inhibition could therefore supplement the current standard of care for traumatic and burn injuries.

Mechanomodulation of Burn Scarring Via Pressure Therapy

Significance: The physical and psychological sequalae of burn injuries account for 10 million disability-adjusted life years lost annually. Hypertrophic scarring (HSc) after burn injury results in reduced mobility, contracture, pain, itching, and aesthetic changes for burn survivors. Despite the prevalence of scarring and the number of scar therapies available, none are highly effective at preventing HSc after burn injury. Recent Advances: Recent studies modulating the mechanical environment surrounding incisional and excisional wounds have shown off-loading of tension to be a powerful strategy to prevent scar formation. Preclinical studies applying force perpendicular to the surface of the skin or using a combination of pressure both circumferentially and perpendicularly have shown substantial reductions in scar thickness and contraction after burn injury. Critical Issues: Though pressure therapy is highly effective in preclinical studies, outcomes in clinical studies have been variable and may be a result of differing therapy protocols and garment material fatigue. A recent adult clinical study reported a significant reduction in pressure after 1 month of use and significant reduction between 1 and 2 months of use, resulting in below therapeutic doses of pressure applied after only 1 month of use. Future Directions: To enhance efficacy of pressure garments, new low-fatigue materials must be developed for use in standard garments or garments must be redesigned to allow for adjustment to compensate for the loss of pressure with time. Additionally, measurements of applied pressure should be performed routinely during clinic visits to ensure that therapeutic doses of pressure are being delivered.

Healing Mechanisms in Cutaneous Wounds: Tipping the Balance

Acute and chronic cutaneous wounds pose a significant health and economic burden. Cutaneous wound healing is a complex process that occurs in four distinct, yet overlapping, highly coordinated stages: hemostasis, inflammation, proliferation, and remodeling. Postnatal wound healing is reparative, which can lead to the formation of scar tissue. Regenerative wound healing occurs during fetal development and in restricted postnatal tissues. This process can restore the wound to an uninjured state by producing new skin cells from stem cell reservoirs, resulting in healing with minimal or no scarring. Focusing on the pathophysiology of acute burn wounds, this review highlights reparative and regenerative healing mechanisms (including the role of cells, signaling molecules, and the extracellular matrix) and discusses how components of regenerative healing are being used to drive the development of novel approaches and therapeutics aimed at improving clinical outcomes. Important components of regenerative healing, such as stem cells, growth factors, and decellularized dermal matrices, are all being evaluated to recapitulate more closely the natural regenerative healing process.

Disrupting biological sensors of force promotes tissue regeneration in large organisms

Tissue repair and healing remain among the most complicated processes that occur during postnatal life. Humans and other large organisms heal by forming fibrotic scar tissue with diminished function, while smaller organisms respond with scarless tissue regeneration and functional restoration. Well-established scaling principles reveal that organism size exponentially correlates with peak tissue forces during movement, and evolutionary responses have compensated by strengthening organ-level mechanical properties. How these adaptations may affect tissue injury has not been previously examined in large animals and humans. Here, we show that blocking mechanotransduction signaling through the focal adhesion kinase pathway in large animals significantly accelerates wound healing and enhances regeneration of skin with secondary structures such as hair follicles. In human cells, we demonstrate that mechanical forces shift fibroblasts toward pro-fibrotic phenotypes driven by ERK-YAP activation, leading to myofibroblast differentiation and excessive collagen production. Disruption of mechanical signaling specifically abrogates these responses and instead promotes regenerative fibroblast clusters characterized by AKT-EGR1.

Humans and other large mammals heal wounds by forming fibrotic scar tissue with diminished function. Here, the authors show that disrupting mechanotransduction through the focal adhesion kinase pathway in large animals accelerates healing, prevents fibrosis, and enhances skin regeneration.

Fibrosis: from mechanisms to medicines

Fibrosis can affect any organ and is responsible for up to 45% of all deaths in the industrialized world. It has long been thought to be relentlessly progressive and irreversible, but both preclinical models and clinical trials in various organ systems have shown that fibrosis is a highly dynamic process. This has clear implications for therapeutic interventions that are designed to capitalize on this inherent plasticity. However, despite substantial progress in our understanding of the pathobiology of fibrosis, a translational gap remains between the identification of putative antifibrotic targets and conversion of this knowledge into effective treatments in humans. Here we discuss the transformative experimental strategies that are being leveraged to dissect the key cellular and molecular mechanisms that regulate fibrosis, and the translational approaches that are enabling the emergence of precision medicine-based therapies for patients with fibrosis.

Inflammation as an orchestrator of cutaneous scar formation: a review of the literature

Inflammation is a key phase in the cutaneous wound repair process. The activation of inflammatory cells is critical for preventing infection in contaminated wounds and results in the release of an array of mediators, some of which stimulate the activity of keratinocytes, endothelial cells, and fibroblasts to aid in the repair process. However, there is an abundance of data suggesting that the strength of the inflammatory response early in the healing process correlates directly with the amount of scar tissue that will eventually form. This review will summarize the literature related to inflammation and cutaneous scar formation, highlight recent discoveries, and discuss potential treatment modalities that target inflammation to minimize scarring.

Current and Emerging Topical Scar Mitigation Therapies for Craniofacial Burn Wound Healing

Burn injury in the craniofacial region causes significant health and psychosocial consequences and presents unique reconstructive challenges. Healing of severely burned skin and underlying soft tissue is a dynamic process involving many pathophysiological factors, often leading to devastating outcomes such as the formation of hypertrophic scars and debilitating contractures. There are limited treatment options currently used for post-burn scar mitigation but recent advances in our knowledge of the cellular and molecular wound and scar pathophysiology have allowed for development of new treatment concepts. Clinical effectiveness of these experimental therapies is currently being evaluated. In this review, we discuss current topical therapies for craniofacial burn injuries and emerging new therapeutic concepts that are highly translational.

Improved Scar Outcomes with Increased Daily Duration of Pressure Garment Therapy

Objective: Despite the development of a number of treatment modalities, scarring remains common postburn injury. To reduce burn scarring, pressure garment therapy has been widely utilized but is complicated by low patient adherence. To improve adherence, reduced hours of daily garment wear has been proposed. Approach: To examine the efficacy of pressure garment therapy at reduced durations of daily wear, a porcine burn-excise-autograft model was utilized. Grafted burns were treated with pressure garments (20 mmHg) for 8, 16, or 24 h of daily wear with untreated burns serving as controls. Scar area, thickness, biomechanical properties, and tissue structure were assessed over time. Results: All treatment groups reduced scar thickness and contraction versus controls and improved scar pliability and elasticity. Pressure garments worn 24 h per day significantly reduced contraction versus the 8- and 16-h groups and prevented alignment of collagen within the dermis. Innovation: Though pressure garment therapy is prescribed for use 23 h per day, the need for almost continuous use has not been previously examined. Adjustable, low-fatigue pressure garments were developed for this porcine study to examine the role of daily duration of wear without confounding factors such as garment fatigue and patient adherence. Conclusion: For maximum efficacy, pressure garments should be worn 23 to 24 h per day; however, garments worn as little as 8 h per day significantly improve scar outcomes versus no treatment.

The Northwestern Abdominoplasty Scar Model: A Tool for High-Throughput Assessment of Scar Therapeutics

Significance: Scar management is an important concern in plastic surgery. Scar models that best mimic in vivo human scarring are essential for understanding scar development and progression, assessing the efficacy of therapeutics, and providing reliable and valid research outcomes. Recent Advances: In 2016, Lanier et al. proposed a new in vivo patient model, the Northwestern Abdominoplasty Scar Model, that overcomes the prior limitations of both animal and human models, with greater representativeness of the human scarring process, expedited recruitment, smaller sample requirements, and greater flexibility in the types and number of interventions that can be studied simultaneously. Critical Issues: Existing animal models suffer from limitations that impede generalization to human scars. Human scar studies are difficult to conduct and rarely used due to recruitment difficulties, ethical concerns regarding purposeful wounding, and inherent variability based on location, type of scar, and the heterogeneity of the host response between humans. Although overcoming many of these hurdles, the Northwestern Abdominoplasty Scar Model still has a few limitations. In addition, there remains a need for further study of and comparison between the Northwestern Abdominoplasty Scar Model and existing human and animal models, to inspire more widespread acceptance of a standardized human scar model. Future Directions: The Northwestern Abdominoplasty Scar Model is a critical stepping stone toward better human scar models. This model hopefully will inspire other in vivo patient models utilizing elective surgery to overcome recruitment and ethical concerns.

Experimental models and methods for cutaneous wound healing assessment

Wound healing studies are intricate, mainly because of the multifaceted nature of the wound environment and the complexity of the healing process, which integrates a variety of cells and repair phases, including inflammation, proliferation, reepithelialization and remodelling. There are a variety of possible preclinical models, such as in mice, rabbits and pigs, which can be used to mimic acute or impaired for example, diabetic and nutrition-related wounds. These can be induced by many different techniques, with excision or incision being the most common. After determining a suitable model for a study, investigators need to select appropriate and reproducible methods that will allow the monitoring of the wound progression over time. The assessment can be performed by non-invasive protocols such as wound tracing, photographic documentation (including image analysis), biophysical techniques and/or by invasive protocols that will require wound biopsies. In this article, we provide an overview of some of the most often needed and used: (a) preclinical/animal models including incisional, excisional, burn and impaired wounds; (b) methods to evaluate the healing progression such as wound healing rate, wound analysis by image, biophysical assessment, histopathological, immunological and biochemical assays. The aim is to help researchers during the design and execution of their wound healing studies.

Controlled Delivery of a Focal Adhesion Kinase Inhibitor Results in Accelerated Wound Closure with Decreased Scar Formation

Formation of scars after wounding or trauma represents a significant health care burden costing the economy billions of dollars every year. Activation of focal adhesion kinase (FAK) has been shown to play a pivotal role in transducing mechanical signals to elicit fibrotic responses and scar formation during wound repair. We have previously shown that inhibition of FAK using local injections of a small molecule FAK inhibitor (FAKI) can attenuate scar development in a hypertrophic scar model. Clinical translation of FAKI therapy has been challenging, however, because of the lack of an effective drug delivery system for extensive burn injuries, blast injuries, and large excisional injuries. To address this issue, we have developed a pullulan collagen-based hydrogel to deliver FAKI to excisional and burn wounds in mice. Specifically, two distinct drug-laden hydrogels were developed for rapid or sustained release of FAKI for treatment of burn wounds and excisional wounds, respectively. Controlled delivery of FAKI via pullulan collagen hydrogels accelerated wound healing and reduced collagen deposition and activation of scar-forming myofibroblasts in both wound healing models. Our study highlights a biomaterial-based drug delivery approach for wound and scar management that has significant translational implications.

Scarless wound healing: Transitioning from fetal research to regenerative healing

Since the discovery of scarless fetal skin wound healing, research in the field has expanded significantly with the hopes of advancing the finding to adult human patients. There are several differences between fetal and adult skin that have been exploited to facilitate scarless healing in adults including growth factors, cytokines, and extracellular matrix substitutes. However, no one therapy, pathway, or cell subtype is sufficient to support scarless wound healing in adult skin. More recently, products that contain or mimic fetal and adult uninjured dermis were introduced to the wound healing market with promising clinical outcomes. Through our review of the major experimental targets of fetal wound healing, we hope to encourage research in areas that may have a significant clinical impact. Additionally, we will investigate therapies currently in clinical use and evaluate whether they represent a legitimate advance in regenerative medicine or a vulnerary agent. WIREs Dev Biol 2018, 7:e309. doi: 10.1002/wdev.309 This article is categorized under: Adult Stem Cells, Tissue Renewal, and Regeneration > Regeneration Plant Development > Cell Growth and Differentiation Adult Stem Cells, Tissue Renewal, and Regeneration > Environmental Control of Stem Cells.

Physical Properties of Implanted Porous Bioscaffolds Regulate Skin Repair: Focusing on Mechanical and Structural Features

Porous bioscaffolds are applied to facilitate skin repair since the early 1990s, but a perfect regeneration outcome has yet to be achieved. Until now, most efforts have focused on modulating the chemical properties of bioscaffolds, while physical properties are traditionally overlooked. Recent advances in mechanobiology and mechanotherapy have highlighted the importance of biomaterials' physical properties in the regulation of cellular behaviors and regenerative processes. In skin repair, the mechanical and structural features of porous bioscaffolds are two major physical properties that determine therapeutic efficacy. Here, first an overview of natural skin repair with an emphasis on the major biophysically sensitive cell types involved in this multistage process is provided, followed by an introduction of the four roles of bioscaffolds as skin implants. Then, how the mechanical and structural features of bioscaffolds influence these four roles is discussed. The mechanical and structural features of porous bioscaffolds should be tailored to balance the acceleration of wound closure and functional improvements of the repaired skin. This study emphasizes that decoupling and precise control of the mechanical and structural features of bioscaffolds are significant aspects that should be considered in future biomaterial optimization, which can build a foundation to ultimately achieve perfect skin regeneration outcomes.

Mechanical Forces in Cutaneous Wound Healing: Emerging Therapies to Minimize Scar Formation

Significance: Excessive scarring is major clinical and financial burden in the United States. Improved therapies are necessary to reduce scarring, especially in patients affected by hypertrophic and keloid scars. Recent Advances: Advances in our understanding of mechanical forces in the wound environment enable us to target mechanical forces to minimize scar formation. Fetal wounds experience much lower resting stress when compared with adult wounds, and they heal without scars. Therapies that modulate mechanical forces in the wound environment are able to reduce scar size. Critical Issues: Increased mechanical stresses in the wound environment induce hypertrophic scarring via activation of mechanotransduction pathways. Mechanical stimulation modulates integrin, Wingless-type, protein kinase B, and focal adhesion kinase, resulting in cell proliferation and, ultimately, fibrosis. Therefore, the development of therapies that reduce mechanical forces in the wound environment would decrease the risk of developing excessive scars. Future Directions: The development of novel mechanotherapies is necessary to minimize scar formation and advance adult wound healing toward the scarless ideal. Mechanotransduction pathways are potential targets to reduce excessive scar formation, and thus, continued studies on therapies that utilize mechanical offloading and mechanomodulation are needed.

The tension biology of wound healing

Following skin wounding, the healing outcome can be: regeneration, repair with normal scar tissue, repair with hypertrophic scar tissue or the formation of keloids. The role of chemical factors in wound healing has been extensively explored, and while there is evidence suggesting the role of mechanical forces, its influence is much less well defined. Here, we provide a brief review on the recent progress of the role of mechanical force in skin wound healing by comparing laboratory mice, African spiny mice, fetal wound healing and adult scar keloid formation. A comparison across different species may provide insight into key regulators. Interestingly, some findings suggest tension can induce an immune response, and this provides a new link between mechanical and chemical forces. Clinically, manipulating skin tension has been demonstrated to be effective for scar prevention and treatment, but not for tissue regeneration. Utilising this knowledge, specialists may modulate regulatory factors and develop therapeutic strategies to reduce scar formation and promote regeneration.

Injectable Pore-Forming Hydrogel Scaffolds for Complex Wound Tissue Engineering: Designing and Controlling Their Porosity and Mechanical Properties

Traumatic soft tissue wounds present a significant reconstructive challenge. The adoption of closed-circuit negative pressure wound therapy (NPWT) has enabled surgeons to temporize these wounds before reconstruction. Such systems use porous synthetic foam scaffolds as wound fillers at the interface between the negative pressure system and the wound bed. The idea of using a bespoke porous biomaterial that enhances wound healing, as filler for an NPWT system, is attractive as it circumvents concerns regarding reconstructive delay and the need for dressing changes that are features of the current systems. Porous foam biomaterials are mechanically robust and able to synthesize in situ. Hence, they exhibit potential to fulfill the niche for such a functionalized injectable material. Injectable scaffolds are currently in use for minimally invasive surgery, but the design parameters for large-volume expansive foams remain unclear. Potential platforms include hydrogel systems, (particularly superabsorbent, superporous, and nanocomposite systems), polyurethane-based moisture-cured foams, and high internal phase emulsion polymer systems. The aim of this review is to discuss the design parameters for such future biomaterials and review potential candidate materials for further research into this up and coming field.

Substrate modulus of 3D-printed scaffolds regulates the regenerative response in subcutaneous implants through the macrophage phenotype and Wnt signaling

The growing need for therapies to treat large cutaneous defects has driven recent interest in the design of scaffolds that stimulate regenerative wound healing. While many studies have investigated local delivery of biologics as a restorative approach, an increasing body of evidence highlights the contribution of the mechanical properties of implanted scaffolds to wound healing. In the present study, we designed poly(ester urethane) scaffolds using a templated-Fused Deposition Modeling (t-FDM) process to test the hypothesis that scaffolds with substrate modulus comparable to that of collagen fibers enhance a regenerative versus a fibrotic response. We fabricated t-FDM scaffolds with substrate moduli varying from 5 to 266 MPa to investigate the effects of substrate modulus on healing in a rat subcutaneous implant model. Angiogenesis, cellular infiltration, collagen deposition, and directional variance of collagen fibers were maximized for wounds treated with scaffolds having a substrate modulus (Ks = 24 MPa) comparable to that of collagen fibers. The enhanced regenerative response in these scaffolds was correlated with down-regulation of Wnt/β-catenin signaling in fibroblasts, as well as increased polarization of macrophages toward the restorative M2 phenotype. These observations highlight the substrate modulus of the scaffold as a key parameter regulating the regenerative versus scarring phenotype in wound healing. Our findings further point to the potential use of scaffolds with substrate moduli tuned to that of the native matrix as a therapeutic approach to improve cutaneous healing.

Anti-inflammatory and protective investigations on the effects of Theranekron® "an alcoholic extract of the Tarantula cubensis" on wound healing of peritoneal in the rat: an in vivo comparative study

Background

The present study sought to investigate the effects of Tarantula cubensis extract (TC; Theranekron®) on the histopathological scores of peritoneal wound healing after laparotomy in the rats.

Methods

This study was designed to investigate the effects of Theranekron on the peritoneal wound healing after wound creation, on days9, 14, 19, 24 and 29 post-injury in rats. Twenty-four mature Wister-albino male rats were randomly divided into two groups. In the experimental group, TC was repeatedly injected subcutaneously (SC) over the lesion 9, 14,19 and 24 days after laparotomy, whereas the control group received only normal saline by subcutaneous injection and then the animal groups were euthanized9, 14, 19, 24, and 29 days after wounding respectively by intravenous injections of pentobarbital (50 mg/kg). Finally, assessment of the peritoneal wound healing between the groups was carried out by histopathologic data and statistical tests as Mann-Whitney U, Wilcoxon W and Z

Results

Histopathological examination indicated significant improvement in angiogenesis, re-epithelialization and less inflammatory response in comparison to control and also, revealed matured, compact and parallel deposition of collagen fibrils on day 29. So, at long term, treatment reduced the inflammation and increased the quality and rate of wound re- epithelialization compared to controls(P < 0.05). Furthermore, excluding the control group, rats exhibited the most pronounced effect on wound closure, with the statistically significant improvement in wound healing being seen at post-operative day 29. Moreover, collagen content on days 24 and 29 in the test group was found to be higher than in the healthy group. To warp up, treated groups had a significant increase in peritoneal wound healing area compared to the control group on all days (P < 0.05).

Conclusions

Our results suggested that Theranekron have delivered a novel therapeutic route for wound treatment in clinical practice.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/2958770714954315.