Wound healing models: A systematic review of animal and non-animal models

Bioinspired nanofiber dressings with counter-transport of exudate and drug for treating heavily exuding wounds

Heavily exuding wounds are difficult to heal due to the accumulation of a large amount of exudates and the difficulty in efficient delivery of drugs by conventional wound dressings. Herein, inspired by the microstructure and function of octopus sucker (OS) and tree trunk (TT), we propose a bioinspired strategy to fabricate novel bioinspired OS&TT bilayered wound dressing, assembled by a lower OS-like nanofiber membrane with concave convex arrays and an upper TT-like nanofiber sponge with vertically aligned pores. The integration of bioinspired concave arrays and vertically aligned pores endows the bioinspired OS&TT dressing with dual vertical suction property, enabling effective drainage of significant amount of accumulated liquid. Moreover, the bioinspired convex arrays facilitate distinct drug reverse delivery, achieving a drug delivery efficiency exceeding 88.27 %. In vivo heavily exuding wound treatment results indicate that, the bioinspired OS&TT dressing can alleviate tissue edema, decrease the contents of proinflammatory cytokines, and accelerate wound healing due to the unique dual vertical suction of exudates. When treating the bacteria-infected wound, benefiting from the reverse delivery of antimicrobial ε-polylysine to efficiently kill bacteria, the bioinspired OS&TT dressing shows a better wound healing effect than the dressing with inefficient drug delivery capacity.

Comparative effects of various extracellular vesicle subpopulations derived from clonal mesenchymal stromal cells on cultured fibroblasts in wound healing-related process

INTRODUCTION

Non-healing wounds pose significant challenges and require effective therapeutic interventions. Extracellular vesicles (EVs) have emerged as promising cell-free therapeutic agents in tissue regeneration. However, the functional differences between different subpopulations of EVs in wound healing remain understudied. This study aimed to evaluate the effects of two distinct subpopulations of clonal mesenchymal stromal cells (cMSC)-derived EVs (cMSC-EVs), namely 20 K and 110K-cMSC-EVs, primarily on in vitro wound healing process, providing fast and cost-effective alternatives to animal models.

METHODS

In vitro assays were conducted to compare the effects of 20 K and 110K-cMSC-EVs, isolated through high-speed centrifugation and differential ultracentrifugation, respectively. For evaluation the main mechanisms of wound healing, including cell proliferation, cell migration, angiogenesis, and contraction. Human dermal fibroblasts (HDF) were considered as the main cells for analysis of these procedures. Moreover, gene expression analysis was performed to assess the impact of these EV subpopulations on the related process of wound healing on HDF.

RESULTS

The results demonstrated that both 20 K and 110K-cMSC-EVs exhibited beneficial effects on cell proliferation, cell migration, angiogenesis, and gel contraction. RT-qPCR revealed that both EV types downregulated interleukin 6 (IL6), induced proliferation by upregulating proliferating cell nuclear antigen (PCNA), and regulated remodeling by upregulating matrix metallopeptidase 1 (MMP1) and downregulating collagen type 1 (COL1).

DISCUSSION

This study highlights the effects of both 20 K and 110K-cMSC-EVs on the potency of HDFs in wound healing-related process. As the notable finding, 20K-cMSC-EVs offer a more feasible and cost-effective subpopulation for isolation and follow the GMP standard, recommended to utilize this fraction for therapeutic application.

Nitric oxide-based treatments improve wound healing associated with diabetes mellitus

Non-healing wounds are long-term complications of diabetes mellitus (DM) that increase mortality risk and amputation-related disability and decrease the quality of life. Nitric oxide (NO·)-based treatments (i.e., use of both systemic and topical NO· donors, NO· precursors, and NO· inducers) have received more attention as complementary approaches in treatments of DM wounds. Here, we aimed to highlight the potential benefits of NO·-based treatments on DM wounds through a literature review of experimental and clinical evidence. Various topical NO·-based treatments have been used. In rodents, topical NO·-based therapy facilitates wound healing, manifested as an increased healing rate and a decreased half-closure time. The wound healing effect of NO·-based treatments is attributed to increasing local blood flow, angiogenesis induction, collagen synthesis and deposition, re-epithelization, anti-inflammatory and anti-oxidative properties, and potent broad-spectrum antibacterial effects. The existing literature lacks human clinical evidence on the safety and efficacy of NO·-based treatments for DM wounds. Translating experimental favors of NO·-based treatments of DM wounds into human clinical practice needs conducting clinical trials with well-predefined effect sizes, i.e., wound reduction area, rate of wound healing, and hospital length of stay.

Honey, Gellan Gum, and Hyaluronic Acid as Therapeutic Approaches for Skin Regeneration

Background/Objectives: Chronic wounds pose a significant health concern, with their prevalence increasing due to various etiologies. The global aging population further contributes to this rise, placing a substantial burden on healthcare systems in developed countries. This work aimed to develop new therapeutic options in the form of creams and dressings based on honey, gellan gum, and hyaluronic acid for preventing and treating chronic wounds across all stages. Methods: To address this, after the formulations were developed, in vitro cytocompatibility was determined. To confirm biocompatibility, an ovine wound model was used: full-thickness excisional wounds were treated with three formulations, namely gellan gum and honey sponges (GG-HNY), gellan gum, honey and hyaluronic acid sponges (GG-HA-HNY) and a honey-based cream (cream FB002). Daily assessments, including visual evaluation and wound scoring, were conducted for 30 days. Following the study period, tissues were collected for histological analyses. Results: The macroscopic examination revealed that all therapeutic groups facilitated lesion closure. Lesion size reduction, granulation tissue disappearance, and scar tissue development were consistent across all groups, with the group receiving cream demonstrating an advanced stage of healing. All groups achieved substantial wound closure by day 30, with no significant differences. Histopathological analysis following ISO standards revealed that GG-HA-HNY had the lowest ISO score, indicating minimal reactivity and inflammation, which corroborated the cytocompatibility. Conclusions: Combining these insights with previous findings enhances our understanding of wound regeneration dynamics and contributes to refining therapeutic strategies for chronic wounds. The formulations were designed to balance therapeutic efficacy with cost-effectiveness, leveraging low-cost raw materials and straightforward production methods.

The Wound Reporting in Animal and Human Preclinical Studies (WRAHPS) Guidelines

Preclinical studies for wound healing disorders are an essential step in translating discoveries into therapies. Also, they are an integral component of initial safety screening and gaining mechanistic insights using an in vivo approach. Given the complexity of the wound healing process, existing guidelines for animal testing do not capture key information due to the inevitable variability in experimental design. Variations in study interpretation are increased by complexities associated with wound aetiology, wounding procedure, multiple treatment conditions, wound assessment, and analysis, as well as lack of acknowledgement of limitation of the model used. Yet, no standards exist to guide reporting crucial experimental information required to interpret results in translational studies of wound healing. Consistency in reporting allows transparency, comparative, and meta-analysis studies and avoids repetition and redundancy. Therefore, there is a critical and unmet need to standardise reporting for preclinical wound studies. To aid in reporting experimental conditions, The Wound Reporting in Animal and Human Preclinical Studies (WRAHPS) Guidelines have now been created by the authors working with the Wound Care Collaborative Community (WCCC) GAPS group to provide a checklist and reporting template for the most frequently used preclinical models in support of development for human clinical trials for wound healing disorders. It is anticipated that the WRAHPS Guidelines will standardise comprehensive methods for reporting in scientific manuscripts and the wound healing field overall. This article is not intended to address regulatory requirements but is intended to provide general guidelines on important scientific considerations for such studies.

Isoorientin Improves Excisional Skin Wound Healing in Mice

Background/Objectives: Wound healing relies on a coordinated process with the participation of different mediators. Natural products are a source of active compounds with healing potential. Isoorientin is a natural flavone recognized as having several pharmacological properties, such as anti-inflammatory effects, making it a potential treatment for wounds. We investigated the effect of isoorientin on the healing of excisional skin wounds. Methods: Male Swiss mice were subjected to the induction of excisional skin wounds (6 mm diameter) and treated with a vehicle (2% dimethyl sulfoxide in propylene glycol) or 2.5% isoorientin applied topically once a day for 14 days. The wound area was measured on days 0, 3, 7, and 14. Histopathological analyses were performed on the cicatricial tissue after 14 days. The myeloperoxidase activity and the interleukin-1β, tumoral necrosis factor (TNF)-α, and interleukin-6 concentrations were determined on the third day. Results: We observed that 3 days after the topical application of isoorientin, the lesion area was significantly smaller when compared to those of the vehicle (p < 0.01) and control (p < 0.05) groups. No difference was observed after 7 and 14 days of induction. Despite this, on day 14, histological analysis of cicatricial tissue from the animals treated with isoorientin showed reduced epidermal thickness (p < 0.001) and increased collagen deposition (p < 0.001). These effects were accompanied by decreased myeloperoxidase activity and interleukin-1β concentration on the third day of induction, without alteration in TNF-α and interleukin-6. Conclusions: The treatment with isoorientin promoted better tissue repair in excisional wounds in mice, which may be linked to the modulation of the early inflammatory response.

Unveiling advanced strategies for therapeutic stem cell interventions in severe burn injuries: a comprehensive review

This comprehensive review explores the complex terrain of stem cell therapies as a potential therapeutic frontier in the healing of complicated burn wounds. Serious tissue damage, impaired healing processes, and possible long-term consequences make burn wounds a complex problem. An in-depth review is required since, despite medical progress, existing methods for treating severe burn wounds have significant limitations. Burn wounds are difficult to heal because they cause extensive tissue damage. The challenges of burn injury-induced tissue regeneration and functional recovery are also the subject of this review. Although there is a lot of promise in current stem cell treatments, there are also some limitations with scalability, finding the best way to transport the cells, and finding consistent results across different types of patients. To shed light on how to improve stem cell interventions to heal severe burn wounds, this review covers various stem cell applications in burn wounds and examines these obstacles. To overcome these obstacles, one solution is to enhance methods of stem cell distribution, modify therapies according to the severity of the burn, and conduct more studies on how stem cell therapy affects individual patients. Novel solutions may also be possible through the combination of cutting-edge technologies like nanotechnology and biotechnology. This review seeks to increase stem cell interventions by analyzing present challenges and suggesting strategic improvements. The goal is to provide a more effective and tailored way to repair serious burn wounds.

The rat as an animal model in chronic wound research: An update

The increasing global prevalence of chronic wounds underscores the growing importance of developing effective animal models for their study. This review offers a critical evaluation of the strengths and limitations of rat models frequently employed in chronic wound research and proposes potential improvements. It explores these models in the context of key comorbidities, including diabetes, venous and arterial insufficiency, pressure-induced blood flow obstruction, and infections. Additionally, the review examines important wound factors including age, sex, smoking, and the impact of anesthetic and analgesic drugs, acknowledging their substantial effects on research outcomes. A thorough understanding of these variables is crucial for refining animal models and can provide valuable insights for future research endeavors.

A Standardized Porcine Model for Partial-Thickness Wound Healing Studies: Design, Characterization, Model Validation, and Histological Insights

Wound healing is a complex process that is still not fully understood despite extensive research. To address this, we aimed to design and characterize a standardized porcine model for the evaluation of wound healing, dressings, cell therapies, and pharmaceutical agents. Using a standardized approach, we examined the wound healing process in 1.2 mm-deep dermatome wounds at defined positions in 11 female pigs. Unlike previous studies that have only described/analyzed selected punch biopsies, we performed and described histological analyses along the complete wound length using quantitative morphometric methods. All animals remained fully healthy following surgery and showed no signs of infection. Our histopathological evaluation using a predetermined grading score and quantitative manual morphometry demonstrated the impact of different tissue sampling methods, sampling sites, and residual dermis thickness on wound healing. Our study presents a reproducible model for wound healing evaluation and demonstrates the usefulness of porcine models for assessing dermal and epidermal wound healing. The use of histological analyses over the complete wound length provides advantages over previous studies, leading to the possibility of a deeper understanding of the wound healing process. This model could potentially facilitate future research on novel wound dressings and local wound healing therapies.

Image-based non-invasive assessment of suction blister wounds for clinical safety and efficacy

Recognising the need for objective imaging-based technologies to assess wound healing in clinical studies, the suction blister wound model offers an easily accessible wound model that creates reproducible epidermal wounds that heal without scarring. This study provides a comprehensive methodology for implementing and evaluating photography-based imaging techniques utilising the suction blister wound model. Our method encompasses a protocol for capturing consistent, high-quality photographs and procedures for quantifying these images via a visual wound healing score and a computer-assisted colour analysis of wound exudation and wound redness. We employed this methodology on 16 suction blister wounds used as controls in a clinical phase-1 trial. Our method enabled us to discern and quantify subtle differences between individual wounds concerning healing progress, erythema and wound exudation. The wound healing score exhibited a high inter-rater agreement. There was a robust correlation between the spectrophotometer-measured erythema index and photography-based wound redness, as well as between dressing protein content and photography-based dressing yellowness. In conclusion, this study equips researchers conducting clinical wound studies with reproducible methods that may support future wound research and aid in the development of new treatments.

Effect of Ducrosia anethifolia methanol extract against methicillin resistant Staphylococcus aureus and Pseudomonas aeruginosa biofilms on excision wound in diabetic mice

Background

Ducrosia anethifolia is an aromatic desert plant used in Saudi folk medicine to treat skin infections. It is widely found in Middle Eastern countries.

Methods

A methanolic extract of the plant was prepared, and its phytoconstituents were determined using LC-MS. In-vitro and in-vivo antibacterial and antibiofilm activities of the methanolic extract were evaluated against multidrug-resistant bacteria. The cytotoxic effect was assessed using HaCaT cell lines in-vitro. Diabetic mice were used to study the in-vivo antibiofilm and wound healing activity using the excision wound method.

Results

More than 50 phytoconstituents were found in the extract after LC-MS analysis. The extract exhibited antibacterial activity against both the tested pathogens. The extract was free of irritant effects on mice skin, and no cytotoxicity was observed on HaCaT cells with an IC50 value of 1381 µg/ml. The ointment formulation of the extract increased the healing of diabetic wounds. The microbial load of both pathogens in the wounded tissue was also reduced after the treatment. The extract was more effective against methicillin-resistant Staphylococcus aureus (MRSA) than MDR-P. aeruginosa in both in vitro and in vivo experiments. Further, skin regeneration was also observed in histological studies.

Conclusions

The results showed that D. anethifolia methanol extract supports wound healing in infected wounds in diabetic mice through antibacterial, antibiofilm, and wound healing activities.

Bringing innovative wound care polymer materials to the market: Challenges, developments, and new trends

The development of innovative products for treating acute and chronic wounds has become a significant topic in healthcare, resulting in numerous products and innovations over time. The growing number of patients with comorbidities and chronic diseases, which may significantly alter, delay, or inhibit normal wound healing, has introduced considerable new challenges into the wound management scenario. Researchers in academia have quickly identified promising solutions, and many advanced wound healing materials have recently been designed; however, their successful translation to the market remains highly complex and unlikely without the contribution of industry experts. This review article condenses the main aspects of wound healing applications that will serve as a practical guide for researchers working in academia and industry devoted to designing, evaluating, validating, and translating polymer wound care materials to the market. The article highlights the current challenges in wound management, describes the state-of-the-art products already on the market and trending polymer materials, describes the regulation pathways for approval, discusses current wound healing models, and offers a perspective on new technologies that could soon reach consumers. We envision that this comprehensive review will significantly contribute to highlighting the importance of networking and exchanges between academia and healthcare companies. Only through the joint of these two actors, where innovation, manufacturing, regulatory insights, and financial resources act in harmony, can wound care products be developed efficiently to reach patients quickly and affordably.

Understanding the ideal wound healing mechanistic behavior using in silico modelling perspectives: A review

Complexity of the entire body precludes an accurate assessment of the specific contributions of tissues or cells during the healing process, which might be expensive and time consuming. Because of this, controlling the wound's size, depth, and dimensions may be challenging, and there is not yet an efficient and reliable chronic wound model representation. Furthermore, given the inherent challenges associated with conducting non-invasive in vivo investigations, it becomes peremptory to explore alternative methodologies for studying wound healing. In this context, biologically-realistic mathematical and computational models emerge as a valuable framework that can effectively address this need. Therefore, it might improve our approach to understanding the process at its core. This article will examines all facets of wound healing, including the kinds, pathways, and most current developments in wound treatment worldwide, particularly in silico modelling utilizing both mathematical and structure-based modelling techniques. It may be helpful to identify the crucial traits through the feedback loop of computer models and experimental investigations in order to build innovative therapies to cure wounds. Hence the effectiveness of personalised medicine and more targeted therapy in the healing of wounds may be enhanced by this interdisciplinary expertise.

The Potential of PIP3 in Enhancing Wound Healing

Given the role of phosphatidylinositol 3,4,5-trisphosphate (PIP3) in modulating cellular processes such as proliferation, survival, and migration, we hypothesized its potential as a novel therapeutic agent for wound closure enhancement. In this study, PIP3 was examined in its free form or as a complex with cationic starch (Q-starch) as a carrier. The intracellular bioactivity and localization of free PIP3 and the Q-starch/PIP3 complexes were examined. Our results present the capability of Q-starch to form complexes with PIP3, facilitate its cellular membrane internalization, and activate intracellular paths leading to enhanced wound healing. Both free PIP3 and Q-starch/PIP3 complexes enhanced monolayer gap closure in scratch assays and induced amplified collagen production within HaCAT and BJ fibroblast cells. Western blot presented enhanced AKT activation by free or complexed PIP3 in BJ fibroblasts in which endogenous PIP3 production was pharmacologically inhibited. Furthermore, both free PIP3 and Q-starch/PIP3 complexes expedited wound closure in mice, after single or daily dermal injections into the wound margins. Free PIP3 and the Q-starch/PIP3 complexes inherently activated the AKT signaling pathway, which is responsible for crucial wound healing processes such as migration; this was also observed in wound assays in mice. PIP3 was identified as a promising molecule for enhancing wound healing, and its ability to circumvent PI3K inhibition suggests possible implications for chronic wound healing.

Hydrogel-enabled mechanically active wound dressings

Wound care is a major clinical and social concern. However, effective wound repair remains challenging where conventional dressings yield detrimental healing outcomes. An emerging technique, named mechanically active dressing (MAD), uses self-contractile hydrogels to mechanically contract the wound bed. MAD has shown improved healing rates with limited side effects. These promising developments in wound care call for a timely review on the development of such technology. Herein, we shed light on the mechanism underlying mechanically modulated wound healing, carry out a systematic discussion on the status quo of designing hydrogels for MAD fabrication, and conclude with perspectives on design, use and clinical translation for realizing the future goal of personalized wound care.

From Time to Timer in Wound Healing Through the Regeneration

Hard-to-heal wounds are an important public health issue worldwide, with a significant impact on the quality of life of patients. It is estimated that approximately 1-2% of the global population suffers from difficult wounds, which can be caused by a variety of factors such as trauma, infections, chronic diseases like diabetes or obesity, or poor health conditions. Hard-to-heal wounds are often characterized by a slow and complicated healing process, which can lead to serious complications such as infections, pressure ulcers, scar tissue formation, and even amputations. These complications can have a significant impact on the mobility, autonomy, and quality of life of patients, leading to an increase in healthcare and social costs associated with wound care. The preparation of the wound bed is a key concept in the management of hard-to-heal wounds, with the aim of promoting an optimal environment for healing. The TIME (Tissue, Infection/Inflammation, Moisture, Edge) model is a systematic approach used to assess and manage wounds in a targeted and personalized way. The concept of TIMER, expanding the TIME model, further focuses on regenerative processes, paying particular attention to promoting tissue regeneration and wound healing in a more effective and comprehensive way. The new element introduced in the TIMER model is "Regeneration", which highlights the importance of activating and supporting tissue regeneration processes to promote complete and lasting wound healing. Regenerative therapies can include a wide range of approaches, including cellular therapies, growth factors, bioactive biomaterials, stem cell therapies, and growth factor therapies. These therapies aim to promote the formation of new healthy tissues, reduce inflammation, improve vascularization, and stimulate cellular proliferation to accelerate wound closure and prevent complications. Thanks to continuous progress in research and development of regenerative therapies, more and more patients suffering from difficult wounds can benefit from innovative and promising solutions to promote faster and more effective healing, improve quality of life, and reduce the risk of long-term complications.

Efficacy of nano encapsulated herbal extracts in the treatment of induced wounds in animal models: a systematic review protocol

BACKGROUND

Wounds inflict pain and affect human health causing high expenditure on treatment and management. Herbal crude extracts are used in traditional medicine as a treatment for wounds and other illnesses. However, the progress in the use of plants has been deterred due to their poor solubility and poor bioavailability requiring administration at high doses. It has been established that nanoencapsulation of herbal products in nanocarriers (size 1 nm to 100 nm) such as nanofibers, nanoparticles, nanospheres, and nanoliposomes greatly improves their efficacy. Due to their small and large surface area, nanocarriers are more biologically active, improve bioavailability, protect the drug from deterioration, and release it to the targeted site in a sustainable manner.

AIM

The review aims to collate and appraise evidence on the efficacy of nano encapsulated herbal extracts in the treatment of induced wounds in animal models.

METHODS

The review will be protocol-driven and conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis for Protocols (PRISMA-P) and protocol guidelines for systematic review and meta-analysis for animal intervention studies. The final review will be conducted and reported with reference to PRISMA 2020 statement. Studies will be searched in Pub Med, ProQuest, Web of Science, Medline Ovid, EMBASE, and Google Scholar. The PRISMA flow criteria will be followed in screening the articles for inclusion. Data extraction form will be designed in Excel spreadsheet 2013 and data extracted based on the primary and secondary outcomes. Risk of bias assessment will be done using SYRCLE's risk of bias tool for animal studies. Data analysis will be done using narrative and quantitative synthesis.

EXPECTED RESULTS

We hope to make meaningful comparisons between the effectiveness of the herb-loaded nanomaterials and other interventions (controls) in the selected studies, based on the primary and secondary outcome measures. We expect that these findings to inform clinical practice on whether preclinical studies show enough quality evidence on the efficacy and safety of herbal-loaded nanomaterials that can be translated into clinical trials and further research.

SYSTEMIC REVIEW REGISTRATION

PROSPERO 330330. The protocol was submitted on the 11th of May 2022.

Advancements and Insights in Exosome-Based Therapies for Wound Healing: A Comprehensive Systematic Review (2018-June 2023)

Exosomes have shown promising potential as a therapeutic approach for wound healing. Nevertheless, the translation from experimental studies to commercially available treatments is still lacking. To assess the current state of research in this field, a systematic review was performed involving studies conducted and published over the past five years. A PubMed search was performed for English-language, full-text available papers published from 2018 to June 2023, focusing on exosomes derived from mammalian sources and their application in wound healing, particularly those involving in vivo assays. Out of 531 results, 148 papers were selected for analysis. The findings revealed that exosome-based treatments improve wound healing by increasing angiogenesis, reepithelization, collagen deposition, and decreasing scar formation. Furthermore, there was significant variability in terms of cell sources and types, biomaterials, and administration routes under investigation, indicating the need for further research in this field. Additionally, a comparative examination encompassing diverse cellular origins, types, administration pathways, or biomaterials is imperative. Furthermore, the predominance of rodent-based animal models raises concerns, as there have been limited advancements towards more complex in vivo models and scale-up assays. These constraints underscore the substantial efforts that remain necessary before attaining commercially viable and extensively applicable therapeutic approaches using exosomes.

Wound healing dynamics, morbidity, and complications of palatal soft-tissue harvesting

Palatal-tissue harvesting is a routinely performed procedure in periodontal and peri-implant plastic surgery. Over the years, several surgical approaches have been attempted with the aim of obtaining autogenous soft-tissue grafts while minimizing patient morbidity, which is considered the most common drawback of palatal harvesting. At the same time, treatment errors during the procedure may increase not only postoperative discomfort or pain but also the risk of developing other complications, such as injury to the greater palatine artery, prolonged bleeding, wound/flap sloughing, necrosis, infection, and inadequate graft size or quality. This chapter described treatment errors and complications of palatal harvesting techniques, together with approaches for reducing patient morbidity and accelerating donor site wound healing. The role of biologic agents, photobiomodulation therapy, local and systemic factors, and genes implicated in palatal wound healing are also discussed.

Chronic Wound Healing Models

In this paper, we review and analyze the commonly available wound healing models reported in the literature and discuss their advantages and issues, considering their relevance and translational potential to humans. Our analysis includes different in vitro and in silico as well as in vivo models and experimental techniques. We further explore the new technologies in the study of wound healing to provide an all encompassing review of the most efficient ways to proceed with wound healing experiments. We revealed that there is not one model of wound healing that is superior and can give translatable results to human research. Rather, there are many different models that have specific uses for studying certain processes or stages of wound healing. Our analysis suggests that when performing an experiment to assess stages of wound healing or different therapies to enhance healing, one must consider not only the species that will be used but also the type of model and how this can best replicate the physiology or pathophysiology in humans.

CuS Hybrid Hydrogel for Near-Infrared-Enhanced Infected Wound Healing: A Gelatin-Assisted Synthesis and Direct Incorporation Strategy

Developing antibacterial hydrogels, with good mechanical strength and self-healing ability to resist bacterial invasion and accelerate skin regeneration, is critical for infected full-thickness skin wound treatment. Herein, we report a gelatin-assisted synthesis and direct incorporation strategy to construct a CuS hybrid hydrogel for infected wound healing applications. CuS nanodots (NDs) were synthesized directly inside a gelatin host matrix (Gel-CuS), and these tightly confined and evenly distributed CuS NDs displayed superb dispersibility and stability against oxidation. Gel-CuS was then used to crosslink with oxidized dextran (ODex) to form a Gel-CuS-8/ODex hydrogel (8 stands for the concentration of CuS, in mM) via a facile Schiff-base reaction, which exhibited improved mechanical properties, excellent adhesion and self-healing ability, suitable swelling and degradation behavior, and good biocompatibility. The Gel-CuS-8/ODex hydrogel can act as an efficient antibacterial agent due to its photothermal and photodynamic properties under a 1064 nm laser irradiation. Furthermore, in animal experiments, when being applied as wound dressing, the Gel-CuS-8/ODex hydrogel significantly promoted infected full-thickness cutaneous wound healing through improved epidermis and granulation tissue formation and accelerated generation of new blood vessels, hair follicles, and collagen deposition after proper near-infrared irradiation treatment. This work provides a promising strategy to synthesize functional inorganic nanomaterials tightly and evenly embedded inside modified natural hydrogel networks for wound healing applications.

Effect of Chitosan-Diosgenin Combination on Wound Healing

The difficult-to-heal wounds continue to be a problem for modern medicine. Chitosan and diosgenin possess anti-inflammatory and antioxidant effects making them relevant substances for wound treatment. That is why this work aimed to study the effect of the combined application of chitosan and diosgenin on a mouse skin wound model. For the purpose, wounds (6 mm diameter) were made on mice's backs and were treated for 9 days with one of the following: 50% ethanol (control), polyethylene glycol (PEG) in 50% ethanol, chitosan and PEG in 50% ethanol (Chs), diosgenin and PEG in 50% ethanol (Dg) and chitosan, diosgenin and PEG in 50% ethanol (ChsDg). Before the first treatment and on the 3rd, 6th and 9th days, the wounds were photographed and their area was determined. On the 9th day, animals were euthanized and wounds' tissues were excised for histological analysis. In addition, the lipid peroxidation (LPO), protein oxidation (POx) and total glutathione (tGSH) levels were measured. The results showed that ChsDg had the most pronounced overall effect on wound area reduction, followed by Chs and PEG. Moreover, the application of ChsDg maintained high levels of tGSH in wound tissues, compared to other substances. It was shown that all tested substances, except ethanol, reduced POx comparable to intact skin levels. Therefore, the combined application of chitosan and diosgenin is a very promising and effective medication for wound healing.

Beyond the Scar: A Basic Science Review of Wound Remodeling

Significance: Increasing development of experimental animal models has allowed for the study of scar formation. However, many pathophysiological unknowns remain in the longest stage of healing, the remodeling stage, which may continue for a year or more. The wound healing process results in different types of scarring classified as normal or pathological depending on failures at each stage. Failures can also occur during wound remodeling, but the molecular mechanisms driving the wound remodeling process have yet to be investigated. Recent Advances: While the current understanding of wound repair is based on investigations of acute healing, these experimental models have informed knowledge of key components of remodeling. This review examines the components that contribute to collagen organization and the final scar, including cell types, their regulation, and signaling pathways. Dysregulation in any one of these components causes pathologic healing. Critical Issues and Future Directions: As wounds continue to remodel months to years after reepithelialization, new models to better understand long-term remodeling will be critical for improving healing outcomes. Further investigation of the contributions of fibroblasts and cell signaling pathways involved during remodeling as well as their potential failures may inform new approaches in promoting regenerative healing beyond reepithelialization.

Comparison of biopolymer scaffolds for the fabrication of skin substitutes in a porcine wound model

This study compared three acellular scaffolds as templates for the fabrication of skin substitutes. A collagen-glycosaminoglycan (C-GAG), a biodegradable polyurethane foam (PUR) and a hybrid combination (PUR/C-GAG) were investigated. Scaffolds were prepared for cell inoculation. Fibroblasts and keratinocytes were serially inoculated onto the scaffolds and co-cultured for 14 days before transplantation. Three pigs each received four full-thickness 8 cm × 8 cm surgical wounds, into which a biodegradable temporising matrix (BTM) was implanted. Surface seals were removed after integration (28 days), and three laboratory-generated skin analogues and a control split-thickness skin graft (STSG) were applied for 16 weeks. Punch biopsies confirmed engraftment and re-epithelialisation. Biophysical wound parameters were also measured and analysed. All wounds showed greater than 80% epithelialisation by day 14 post-transplantation. The control STSG displayed 44% contraction over the 16 weeks, and the test scaffolds, C-GAG 64%, Hybrid 66.7% and PUR 67.8%. Immunohistochemistry confirmed positive epidermal keratins and basement membrane components (Integrin alpha-6, collagens IV and VII). Collagen deposition and fibre organisation indicated the degree of fibrosis and scar produced for each graft. All scaffold substitutes re-epithelialised by 4 weeks. The percentage of original wound area for the Hybrid and PUR was significantly different than the STSG and C-GAG, indicating the importance of scaffold retainment within the first 3 months post-transplant. The PUR/C-GAG scaffolds reduced the polymer pore size, assisting cell retention and reducing the contraction of in vitro collagen. Further investigation is required to ensure reproducibility and scale-up feasibility.

Dysregulation of TSP2-Rac1-WAVE2 axis in diabetic cells leads to cytoskeletal disorganization, increased cell stiffness, and dysfunction

Fibroblasts are a major cell population that perform critical functions in the wound healing process. In response to injury, they proliferate and migrate into the wound space, engaging in extracellular matrix (ECM) production, remodeling, and contraction. However, there is limited knowledge of how fibroblast functions are altered in diabetes. To address this gap, several state-of-the-art microscopy techniques were employed to investigate morphology, migration, ECM production, 2D traction, 3D contraction, and cell stiffness. Analysis of cell-derived matrix (CDM) revealed that diabetic fibroblasts produce thickened and less porous ECM that hindered migration of normal fibroblasts. In addition, diabetic fibroblasts were found to lose spindle-like shape, migrate slower, generate less traction force, exert limited 3D contractility, and have increased cell stiffness. These changes were due, in part, to a decreased level of active Rac1 and a lack of co-localization between F-actin and Waskott-Aldrich syndrome protein family verprolin homologous protein 2 (WAVE2). Interestingly, deletion of thrombospondin-2 (TSP2) in diabetic fibroblasts rescued these phenotypes and restored normal levels of active Rac1 and WAVE2-F-actin co-localization. These results provide a comprehensive view of the extent of diabetic fibroblast dysfunction, highlighting the regulatory role of the TSP2-Rac1-WAVE2-actin axis, and describing a new function of TSP2 in regulating cytoskeleton organization.

Bioengineered Wound Healing Skin Models: The Role of Immune Response and Endogenous ECM to Fully Replicate the Dynamic of Scar Tissue Formation In Vitro

The healing of deep skin wounds is a complex phenomenon evolving according with a fine spatiotemporal regulation of different biological events (hemostasis, inflammation, proliferation, remodeling). Due to the spontaneous evolution of damaged human dermis toward a fibrotic scar, the treatment of deep wounds still represents a clinical concern. Bioengineered full-thickness skin models may play a crucial role in this direction by providing a deep understanding of the process that leads to the formation of fibrotic scars. This will allow (i) to identify new drugs and targets/biomarkers, (ii) to test new therapeutic approaches, and (iii) to develop more accurate in silico models, with the final aim to guide the closure process toward a scar-free closure and, in a more general sense, (iv) to understand the mechanisms involved in the intrinsic and extrinsic aging of the skin. In this work, the complex dynamic of events underlaying the closure of deep skin wound is presented and the engineered models that aim at replicating such complex phenomenon are reviewed. Despite the complexity of the cellular and extracellular events occurring during the skin wound healing the gold standard assay used to replicate such a process is still represented by planar in vitro models that have been largely used to identify the key factors regulating the involved cellular processes. However, the lack of the main constituents of the extracellular matrix (ECM) makes these over-simplistic 2D models unable to predict the complexity of the closure process. Three-dimensional bioengineered models, which aim at recreating the closure dynamics of the human dermis by using exogenous biomaterials, have been developed to fill such a gap. Although interesting mechanistic effects have been figured out, the effect of the inflammatory response on the ECM remodelling is not replicated yet. We discuss how more faithful wound healing models can be obtained by creating immunocompetent 3D dermis models featuring an endogenous ECM.

Acceleration of wound healing by topical application of gel formulation of Barringtonia racemosa (L.) Spreng kernel extract

Background: Phytomedicines are gaining a spotlight in wound management, where much research has suggested the wound healing potential of Barringtonia racemosa. The objective of this study was to investigate the effectiveness of B. racemosa kernel extract in accelerating wound healing process in animal models. Methods:B. racemosa kernel was extracted using ethanol:water (7:3) solvent and was then used as a bioactive ingredient in a Carbopol 940-based gel formulation in four different concentrations (1, 3, 5 and 7 ppm). A 3 cm diameter wound was made in the dorsal area of Rattus norvegicus rat and wound healing process was assessed up to 12 days using DESIGN (Depth, Exudate, Size of Inflammation/Infection, Granulation tissue, and Necrotic tissue) scoring system. Results: Our data suggested that the DESIGN scores were significantly different among concentration groups after the 3 rd day onward suggesting B. racemosa extract accelerated the wound healing process. Rats treated with gel formulation containing 7 ppm of B. racemosa kernel extract had faster wound healing than that treated with topical Metcovazin. Conclusion:B. racemosa kernel extract was effective in accelerating wound healing on rats. Further study is warranted to purify the bioactive component and the action mechanism in wound healing process.

Acceleration of wound healing by topical application of gel formulation of Barringtonia racemosa (L.) Spreng kernel extract

Background: Phytomedicines are gaining a spotlight in wound management, where much research has suggested the wound healing potential of Barringtonia racemosa. The objective of this study was to investigate the effectiveness of B. racemosa kernel extract in accelerating wound healing process in animal models. Methods:B. racemosa kernel was extracted using ethanol:water (7:3) solvent and was then used as a bioactive ingredient in a Carbopol 940-based gel formulation in four different concentrations (1, 3, 5 and 7 ppm). A 3 cm diameter wound was made in the dorsal area of Rattus norvegicus rat and wound healing process was assessed up to 12 days using DESIGN (Depth, Exudate, Size of Inflammation/Infection, Granulation tissue, and Necrotic tissue) scoring system. Results: Our data suggested that the DESIGN scores were significantly different among concentration groups after the 3 rdday onward suggesting B. racemosa extract accelerated the wound healing process. Rats treated with gel formulation containing 7 ppm of B. racemosa kernel extract had faster wound healing than that treated with topical Metcovazin. On day 6, macroscopic observation on 7 ppm group revealed that the wound had persistent redness, lesion area of < 3 cm 2, and 80% healthy granulation, where presence of exudate and redness were not observable. Conclusion:B. racemosa kernel extract was effective in accelerating wound healing on rats. Further study is warranted to purify the bioactive component and the action mechanism in wound healing process.

Clinically relevant experimental rodent models of diabetic foot ulcer

Chronic wounds are a substantial clinical problem in diabetes and nearly 6% of diabetics suffer from foot disease including ulceration, infection, and tissue necrosis. Wound healing in diabetes is impaired and delayed and is augmented by diabetic complications. Wound healing involves complex cellular, molecular, and biochemical processes and animal models are the most suitable prototype to investigate and understand the underlying pathological changes in the process of wound healing. Animal models are also useful in evaluating the safety and efficacy of newer therapeutic agents and improving the clinical approaches for human patients with chronic ulcers. The wound healing strategies get more complicated in the presence of diabetes and its associated complication. Despite the advancement in methods of wound healing, the healing of the chronic diabetic foot ulcer (DFU) remains an important clinical problem resulting in costly and prolonged treatment and poses a risk for major amputation. Saying that it is important to elucidate the newer therapeutic targets and strategies via an in-depth understanding of the complicated cascade of the chronic DFU. A major challenge in translating lab findings to clinics is the lack of an optimal preclinical model capable of properly recapitulating human wounds. Both small and large animal models of wound healing involving rodents, rabbits, and pigs have been discussed. Mouse and rats as small animal models and pig as large animal models have been discussed in association with the diabetic wound but there are advantages and limitations for each model. In this review, we critically reviewed the pros and cons of experimental models of diabetic wound healing with a focus on type II diabetes rodent models.

The Regenerative Potential of Substance P

Wound healing is a highly coordinated process which leads to the repair and regeneration of damaged tissue. Still, numerous diseases such as diabetes, venous insufficiencies or autoimmune diseases could disturb proper wound healing and lead to chronic and non-healing wounds, which are still a great challenge for medicine. For many years, research has been carried out on finding new therapeutics which improve the healing of chronic wounds. One of the most extensively studied active substances that has been widely tested in the treatment of different types of wounds was Substance P (SP). SP is one of the main neuropeptides released by nervous fibers in responses to injury. This review provides a thorough overview of the application of SP in different types of wound models and assesses its efficacy in wound healing.

Redox Active Cerium Oxide Nanoparticles: Current Status and Burning Issues

Research on cerium oxide nanoparticles (nanoceria) has captivated the scientific community due to their unique physical and chemical properties, such as redox activity and oxygen buffering capacity, which made them available for many technical applications, including biomedical applications. The redox mimetic antioxidant properties of nanoceria have been effective in the treatment of many diseases caused by reactive oxygen species (ROS) and reactive nitrogen species. The mechanism of ROS scavenging activity of nanoceria is still elusive, and its redox activity is controversial due to mixed reports in the literature showing pro-oxidant and antioxidant activity. In light of its current research interest, it is critical to understand the behavior of nanoceria in the biological environment and provide answers to some of the critical and open issues. This review critically analyzes the status of research on the application of nanoceria to treat diseases caused by ROS. It reviews the proposed mechanism of action and shows the effect of surface coatings on its redox activity. It also discusses some of the crucial issues in deciphering the mechanism and redox activity of nanoceria and suggests areas of future research.

The use of mesenchymal stem cells in animal models for gastrointestinal anastomotic leak: A systematic review

AIM

Anastomotic leak is the most feared complication of gastrointestinal surgery. Mesenchymal stem cell technology is used clinically to promote wound healing; however, the safety and efficacy of this technology on anastomotic healing has yet to be defined. The aim of this study was to investigate whether mesenchymal stem cells confer any benefit when applied to animal models for gastrointestinal anastomotic leak, identify the methodology and how efficacy is assessed.

METHODS

The MEDLINE, EMBASE, WebofScience and Cochrane Library databases were interrogated between 1 January1947 to 1 May 2020. All studies where mesenchymal stem cells were applied to laboratory animal leak models to demonstrate a healing effect were considered. All experimental and histological outcomes were examined. Compliance to ARRIVE and current International Consensus was assessed.

RESULTS

A total of 1205 studies were screened. Twelve studies reported on 438 gastrointestinal anastomoses in four species using 11 models; seven in the colon. No studies utilised a model with a known leak rate. Significant variance was observed in histological outcomes with efficacy demonstrated in five out of 12 studies. One study demonstrated a benefit in leak rate. Colorectal studies had a greater median ARRIVE compliance, 60.8% (IQR 63.2-64.5) compared to noncolorectal 45.4% (IQR 43.8-49.0).

CONCLUSIONS

Mesenchymal stem cell delivery to an animal anastomosis is safe and feasible. Use may confer benefit but findings are currently limited to surrogate histological outcomes. There is consistency in outcome measures reported but variance in how this is assessed. Poor compliance to ARRIVE but good compliance to current international consensus in leak models of the colon was observed.

Challenges with Wound Infection Models in Drug Development

Wound research is an evolving science trying to unfold the complex untold mechanisms behind the wound healing cascade. In particular, interest is growing regarding the role of microorganisms in both acute and chronic wound healing. Microbial burden plays an important role in the persistence of chronic wounds, ultimately resulting in delayed wound healing. It is therefore important for clinicians to understand the evolution of infection science and its various etiologies. Therefore, to understand the role of bacterial biofilm in chronic wound pathogenesis, various in vitro and in vivo models are required to investigate biofilms in wound-like settings. Infection models should be refined comprising an important signet of biofilms. These models are eminent for translational research to obtain data for designing an improved wound care formulation. However, all the existing models possess limitations and do not fit properly in the model frame for developing wound care agents. Among various impediments, one of the major drawbacks of such models is that the wound they possess does not mimic the wound a human develops. Therefore, a novel wound infection model is required which can imitate the human wounds. This review article mainly discusses various in vitro and in vivo models showing microbial colonization, their advantages and challenges. Apart from these models, there are also present ex vivo wound infection models, but this review mainly focused on various in vitro and in vivo models available for studying wound infection in controlled conditions. This information might be useful in designing an ideal wound infection model for developing an effective wound healing formulation.

Gas Plasma-Augmented Wound Healing in Animal Models and Veterinary Medicine

The loss of skin integrity is inevitable in life. Wound healing is a necessary sequence of events to reconstitute the body’s integrity against potentially harmful environmental agents and restore homeostasis. Attempts to improve cutaneous wound healing are therefore as old as humanity itself. Furthermore, nowadays, targeting defective wound healing is of utmost importance in an aging society with underlying diseases such as diabetes and vascular insufficiencies being on the rise. Because chronic wounds’ etiology and specific traits differ, there is widespread polypragmasia in targeting non-healing conditions. Reactive oxygen and nitrogen species (ROS/RNS) are an overarching theme accompanying wound healing and its biological stages. ROS are signaling agents generated by phagocytes to inactivate pathogens. Although ROS/RNS’s central role in the biology of wound healing has long been appreciated, it was only until the recent decade that these agents were explicitly used to target defective wound healing using gas plasma technology. Gas plasma is a physical state of matter and is a partially ionized gas operated at body temperature which generates a plethora of ROS/RNS simultaneously in a spatiotemporally controlled manner. Animal models of wound healing have been vital in driving the development of these wound healing-promoting technologies, and this review summarizes the current knowledge and identifies open ends derived from in vivo wound models under gas plasma therapy. While gas plasma-assisted wound healing in humans has become well established in Europe, veterinary medicine is an emerging field with great potential to improve the lives of suffering animals.

Burns and biofilms: priority pathogens and in vivo models

Burn wounds can create significant damage to human skin, compromising one of the key barriers to infection. The leading cause of death among burn wound patients is infection. Even in the patients that survive, infections can be notoriously difficult to treat and can cause lasting damage, with delayed healing and prolonged hospital stays. Biofilm formation in the burn wound site is a major contributing factor to the failure of burn treatment regimens and mortality as a result of burn wound infection. Bacteria forming a biofilm or a bacterial community encased in a polysaccharide matrix are more resistant to disinfection, the rigors of the host immune system, and critically, more tolerant to antibiotics. Burn wound-associated biofilms are also thought to act as a launchpad for bacteria to establish deeper, systemic infection and ultimately bacteremia and sepsis. In this review, we discuss some of the leading burn wound pathogens and outline how they regulate biofilm formation in the burn wound microenvironment. We also discuss the new and emerging models that are available to study burn wound biofilm formation in vivo.

Wound opening in a thin incompressible viscoelastic tissue

We develop a model to investigate analytically and numerically the mechanics of wound opening made in a viscoelastic, isotropic, homogeneous, and incompressive thin tissue. This process occurs just immediately after the wound infliction. Before any active biological action has taken place, the tissue relaxes, and the wound opens mostly due to the initial homeostatic tension of the tissue, its elastic and viscous properties, and the existing friction between the tissue and its substrate. We find that for a circular wound the regimes of deformation are defined by a single adimensional parameter λ, which characterizes the relative importance of viscosity over friction.

Histological and clinical evaluation of wound healing in pressure ulcers: a novel animal model

OBJECTIVE

Pressure ulcers (PUs) are a major healthcare problem, commonly associated with older people, patients who are bedbound and patients with diabetes. The impact of PUs can decrease patients' quality of life, and lead to high morbidity and mortality rates. In this study, we aimed to describe a novel PU model that simulates pressure ulcers in humans to provide a research tool for new drug testing.

METHOD

Diabetes was induced using streptozocin in 75 adult Sprague Dawley rats. To create the PU, skin was sandwiched between two magnets, one of them implanted below the panniculus carnosus muscle and the other above the skin. The model was tested on nondiabetic rats and diabetic rats, each with pressure ulcers, compared to nondiabetic rats with excisional wounds.

RESULTS

Results showed that the PU model in diabetic (p-value<0.000001) and non-diabetic rats (p-value<0.05) exhibited significantly delayed healing (no healing over 21 days) compared with the excisional wound that was completely healed by day 21.

CONCLUSION

Diabetic rats showed significant changes in intact skin compared with non-diabetic rats, as well as a significant delay in the healing process compared with the non-diabetic group. By effectively impairing the skin contraction otherwise seen in the rats, and thereby delaying healing and making it similar to that seen in hard-to-heal PUs in humans, this model provides an effective tool for wound healing research.

Histological and clinical evaluation of wound healing in pressure ulcers: a novel animal model

OBJECTIVE

Pressure ulcers (PUs) are a major healthcare problem, commonly associated with older people, patients who are bedbound and patients with diabetes. The impact of PUs can decrease patients' quality of life, and lead to high morbidity and mortality rates. In this study, we aimed to describe a novel PU model that simulates pressure ulcers in humans to provide a research tool for new drug testing.

METHOD

Diabetes was induced using streptozocin in 75 adult Sprague Dawley rats. To create the PU, skin was sandwiched between two magnets, one of them implanted below the panniculus carnosus muscle and the other above the skin. The model was tested on nondiabetic rats and diabetic rats, each with pressure ulcers, compared to nondiabetic rats with excisional wounds.

RESULTS

Results showed that the PU model in diabetic (p-value<0.000001) and non-diabetic rats (p-value<0.05) exhibited significantly delayed healing (no healing over 21 days) compared with the excisional wound that was completely healed by day 21.

CONCLUSION

Diabetic rats showed significant changes in intact skin compared with non-diabetic rats, as well as a significant delay in the healing process compared with the non-diabetic group. By effectively impairing the skin contraction otherwise seen in the rats, and thereby delaying healing and making it similar to that seen in hard-to-heal PUs in humans, this model provides an effective tool for wound healing research.

A review of animal models from 2015 to 2020 for preclinical chronic wounds relevant to human health

SIGNIFICANCE

Chronic wounds fail to heal in a timely manner and exhibit sustained inflammation with slow tissue repair and remodelling. They decrease mobility and quality of life, and remain a major clinical challenge in the long-term care of many patients, affecting 6.5 million individuals annually in the U.S., decreasing mobility and quality of life. Treatment costs are a major burden on the U.S. healthcare system, totalling between $25 and $100 billion annually. Chronic wound severity depends upon several factors such as comorbidities, severity of tissue damage, infection and presence of necrosis and vary greatly in their healing mechanisms. In vivo animal models are critical for studying healing pathways of chronic wounds and seek to replicate clinical factors for trials of topical, systemic, and device-based therapeutics. This comprehensive review discusses murine, rat, lapine, canine, feline and porcine models of chronic wounds.

RECENT ADVANCES

Foundational chronic wound models for several species are discussed together with refinements and advances in the time period between 2015 and 2020 which have the potential for broad utility in investigating biological and device-based wound treatment therapies for human health.

CRITICAL ISSUES

Chronic wounds fail to heal in a timely manner and have differing aetiologies, rendering no single in vivo animal model universally applicable.

FUTURE DIRECTIONS

Further studies are required to develop clinically relevant chronic wound animal model which reflect the clinical reality of the various influences of age, disease, comorbidities and gender on delayed healing and enhance understanding of the biological processes of human wound healing.

Histological and microbiological evaluation of surgical wound closure in mouse skin with cyanoacrylate (Histoacryl®) in comparison to poliglecaprone (Monocryl®) traditional suture

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Incisional wound closure is a critical surgical step to facilitate tissue healing.

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Cyanoacrylates (Histoacryl®) have become a popular veterinary wound closure practice.

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Effects of Histoacryl® over traditional suture on wounds rest undetermined.

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Histoacryl® vs. Poliglecaprone (Monocryl®) have similar regenerative results in mice.

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Histoacryl® or Monocryl® could be used to treat wounds in rodents.

Incisional wound closure is a key surgical step to facilitate tissue healing, reduce the risk of infection and obtain esthetic and functional recovery. Cyanoacrylates such as Histoacryl® have become a popular choice in surgical veterinary practice. However, how Histoacryl® is affecting tissue regeneration and bacterial load in the wound in comparison to poliglecaprone (Monocryl®) traditional suture methods remains to be determined. This work aimed to evaluate how wounded tissue responds to traditional suture with Monocryl® (poliglecaprone 25/4-0) and Histoacryl®, as well as provide evidence of their effects on wound healing in mice. Fortyeight hours after the incisional procedure, wound tissue biopsies were prepared for histological and microbiological analysis. Biopsies were fixed and colored with Mallory's trichrome and hematoxylin-eosin stains. For microbiological assays, biopsies were suspended in tryptic soy broth (TSB) and 1/10 diluted to evaluate the number of CFU in nutrient agar plates. Our results show no differences between Histoacryl® and Monocryl® traditional suture suggesting that both methods could be used to treat wounds in small animals such as rodents.

Hydrogel containing (1 → 6)-β-D-glucan (lasiodiplodan) effectively promotes dermal wound healing

A hydrogel containing exocellular (1 → 6)-β-D-glucan (lasiodiplodan, LAS) was developed and its wound healing potential was evaluated. β-Glucans have attracted much interest by the cosmetic industry sector because of their bioactive and functional properties and in promoting skin health. In the present work an β-glucan was studied as a healing biomaterial that has not hitherto been reported in the scientific literature. LAS produced by the ascomycete Lasiodiplodia theobromae MMPI was used in the formulation of a healing hydrogel. Physicochemical and microbiological quality parameters, antioxidant potential and stability of the formulation was evaluated. FTIR, thermal analysis and SEM techniques were also employed in the characterization. Wistar rats were used as a biological model to investigate the wound healing potential. Histological analyses of cutaneous tissue from the dorsal region were conducted after 4, 7, 10 and 14 days of treatment, and evaluated re-epithelialization, cell proliferation and collagen production. Physicochemical stability, microbiological quality and antioxidant potential, especially in relation to its ability to scavenge hydroxyl radicals were found. The hydrogel stimulated cell re-epithelialization and proliferation during all days of the treatment, and stimulated an increase of collagen fibers. Lasiodiplodan showed immunomodulatory activity in wound healing and this biomacromolecule could be an alternative compound in wound care.

Anti-inflammatory, pro-proliferative and antimicrobial potential of the compounds isolated from Daemonorops draco (Willd.) Blume

ETHNO-PHARMACOLOGICAL RELEVANCE

Daemonorops draco (D. draco) commonly known as "Dragon's blood" is one of the most used plants by Momok, Anak Dalam and Talang Mamak tribes from Indonesia as a remedy for wound healing.

AIM OF THE STUDY

This study aimed to identify the extract, fractions and compounds responsible for the anti-inflammatory and pro-proliferative activities of the D. draco resin. Additionally, the antimicrobial activity against two bacteria and one yeast species was analysed.

MATERIALS AND METHODS

Bio-guided isolation of compounds with anti-inflammatory, pro-proliferative and antimicrobial activities from the D. draco resin was carried out by measuring: the inhibition of NF-κB and activation of Nrf2 in THP-1, HaCaT, NIH-3T3 cells; cell proliferation in NIH-3T3 and HaCaT cells; and the antimicrobial effect on E. coli, S. aureus and C. albicans.

RESULTS

Guided isolation by bioassay gave rise to the isolation and characterisation by nuclear magnetic resonance and mass spectrometry of three compounds: 1 (Bexarotene), 2 (Taspine) and 3 (2-hydroxy-1-naphthaldehyde isonicotinoyl hydrazone). All compounds showed NF-κB inhibitory activity with IC₅₀ values of 0.10-0.13, 0.22-0.24 and 3.75-4.78 μM, respectively, while the positive control, Celastrol, had an IC₅₀ of 7.96 μM. Likewise, all compounds showed an activating effect of Nrf2 with EC₅₀ values of 5.34-5.43, 163.20-169.20 and 300.82-315.56 nM, respectively, while the positive control, CDDO-Me, had an EC₅₀ of 0.11 nM. In addition, concerning the pro-proliferative activity, compound 1 (IC₅₀ = 8.62-8.71 nM) showed a capacity of 100%, compound 2 (IC₅₀ = 166-171 nM) showed a capacity of 75%, and compound 3 (IC₅₀ = 469-486 nM) showed a capacity of 65%, while FSB 10% (positive control) had a pro-proliferative activity of 100% in the NIH3T3 cell lines (fibroblasts) and HaCaT (keratinocytes). Finally, all the compounds showed antimicrobial activity with MIC values of 0.12-0.16, 0.31-0.39 and 3.96-3.99 μM, respectively, in S. aureus, E. coli and C. albicans strains, while the positive control, Ofloxacin, had a MIC of 27.65 μM.

CONCLUSION

This study managed to isolate, for the first time, three compounds (Bexarotene, Taspine and 2-hydroxy-1-naphthaldehyde isonicotinoyl hydrazone) from the resin of D. draco, with anti-inflammatory, and pro-proliferative as well as antimicrobial activities.

Tracing skin aging process: a mini- review of in vitro approaches

Skin is a rather complex, yet useful organ of our body. Besides, skin aging is a complicated process that gains a growing interest as mediates many molecular processes in our body. Thus, an efficient skin model is important to understand skin aging function as well as to develop an effective innovative product for skin aging treatment. In this mini review, we present in vitro methods for assessments of skin aging in an attempt to pinpoint basic molecular mechanisms behind this process achieving both a better understanding of aging function and an effective  evaluation of potential products or ingredients that counteract aging. Specifically, this study presents in vitro assays such as 2D or 3D skin models, to evaluate skin aging-related processes such as skin moisturization, photoaging, wound healing, menopause, and skin microbiome as novel efforts in the designing of efficacy assessments in the development of skincare products.

Investigation of Skin Wound Healing Using a Mouse Model

Wound repair is a fundamental physiological process to keep the integrity of the skin, and its dysregulation results in diseases, such as chronic nonhealing wounds or excessive scarring. To study the underlying cellular and molecular mechanisms and identify new therapeutic targets, animal models are often used in the wound healing research. In this chapter, we describe an easy step-by-step protocol to generate skin wounds in a mouse model. Briefly, two full-thickness wounds extending through the panniculus carnosus are made on the dorsum on each side of the midline of a mouse, which is followed by monitoring and quantifying the wound closure. Moreover, the biopsy tissues of skin and wound-edges are collected at different time points for subsequent histology and gene expression analysis.

Recent Advances in the Design of Three-Dimensional and Bioprinted Scaffolds for Full-Thickness Wound Healing

Three-dimensional (3D) printed scaffolds have recently emerged as an innovative treatment option for patients with critical-sized skin wounds. Current approaches to managing life-threatening wounds include skin grafting and application of commercially sourced skin substitutes. However, these approaches are not without several challenges. Limited donor tissue and donor site morbidity remain a concern for tissue grafting, while engineered skin substitutes fail to fully recapitulate the complex native environment required for wound healing. The implementation of 3D printed dermal scaffolds offers a potential solution for these shortcomings. Spatial control over scaffold structure, the ability to incorporate multiple materials and bioactive ingredients, enables the creation of conditions specifically optimized for wound healing. Three-dimensional bioprinting, a subset of 3D printing, allows for the replacement of lost cell populations and secreted active compounds that contribute to tissue repair and recovery. The replacement of damaged and lost cells delivers beneficial effects directly, or synergistically, supporting injured tissue to recover its native state. Despite encouraging results, the promise of 3D printed scaffolds has yet to be realized. Further improvements to current material formulations and scaffold designs are required to achieve the goal of clinical adoption. Herein, we provide an overview of 3D printing techniques and discuss several strategies for healing of full-thickness wounds by using 3D printed acellular scaffolds or bioprinted cellular scaffolds, aimed at translating this technology to the clinical management of skin lesions. We identify the challenges associated with designing and optimizing printed tissue replacements, and discuss the future perspectives of this emerging option for managing patients who present with critical-sized life-threatening cutaneous wounds.

In vitro and in vivo testing of nanofibrous membranes doped with alaptide and L-arginine for wound treatment

We have prepared a candidate biocompatible construct for skin wound healing based on electrospun polycaprolactone (PCL) nanofibrous membranes. The membrane material was loaded either with L-arginine or with alaptide, or with a mixture of both bioactive components. Alaptide is a spirocyclic synthetic dipeptide, an analogue of melanocyte-stimulating hormone release-inhibiting factor. L-arginine is an amino acid with a basic guanidine side chain. It is a direct precursor of nitric oxide, which plays a pivotal role in skin repair. The presence and the distribution of the additives were proved with high-performance liquid chromatography, Fourier-transform infrared spectroscopy and Raman spectroscopy. The influence of L-arginine and alaptide on the morphology of the membrane was characterized using scanning electron microscopy. No statistically significant correlation between fiber diameter and drug concentration was observed. The membranes were then tested in vitro for their cytotoxicity, using primary human dermal fibroblasts, in order to obtain the optimal concentrations of the additives for in vivo tests in a rat model. The membranes with the highest concentration of L-arginine (10 wt. %) proved to be cytotoxic. The membranes with alaptide in concentrations from 0.1 to 2.5 wt.%, and with the other L-arginine concentrations (1 and 5 wt.%), did not show high toxicity. In addition, there was no observed improvement in cell proliferation on the membranes. The in vivo experiments revealed that membranes with 1.5 wt.% of alaptide or with 1.5 wt.% of alaptide in combination with 5 wt.% of L-arginine markedly accelerated the healing of skin incisions, and particularly the healing of skin burns, i.e. wounds of relatively large extent. These results indicate that our newly-developed nanofibrous membranes are promising for treating wounds with large damaged areas, where a supporting material is needed.

Hydrogels based on low-methoxyl amidated citrus pectin and flaxseed gum formulated with tripeptide glycyl-l-histidyl-l-lysine improve the healing of experimental cutting wounds in rats

Hydrogels based on natural and modified polysaccharides represent growing group of suitable matrices for the construction of effective wound healing materials. Bioactive tripeptide glycyl-l-histidyl-l-lysine and amino acid α-l-arginine are known to accelerate wound healing and skin repair. In this study, hydrogels based on low-methoxyl amidated citrus pectin or flaxseed gum were prepared and used for the transport of these healing agents to the experimental cutting wounds affected by extensive skin damage. Fourier-transform infrared spectroscopy, rheology, differential scanning calorimetry, scanning electron microscopy, swelling and release tests confirmed that these hydrogels differed in structure and physical properties. The cationic tripeptide was found to bind to carboxylic groups in LMA pectin, and the C3OH hydroxyl and ring oxygen O5 are involved in this interaction. The pectin hydrogel showed high viscosity and strong elastic properties, while the flaxseed gum hydrogel was characterised as a viscoelastic system of much lower viscosity. The former hydrogel released the drugs very slowly, while the latter hydrogel demonstrated zero order releasing kinetics optimal for drug delivery. In the in vivo wound healing testing on rats, both polysaccharide hydrogels improved the healing process mediated by the mentioned biomolecules. The tripeptide applied in the hydrogels showed significantly higher healing degree and lower healing time than in the control animals without treatment and when it was applied in an aqueous solution. Despite the absence of a synergistic effect, the mixture of the tripeptide and α-l-arginine in the hydrogels was also quite effective in wound healing. According to histological analysis, complete healing was achieved only when using the tripeptide in the flaxseed gum hydrogel. These observations might have an important prospect in clinical application of polysaccharide hydrogels.

Nanotechnology-Based Medical Devices for the Treatment of Chronic Skin Lesions: From Research to the Clinic

Chronic wounds, such as pressure ulcers, diabetic ulcers, venous ulcers and arterial insufficiency ulcers, are lesions that fail to proceed through the normal healing process within a period of 12 weeks. The treatment of skin chronic wounds still represents a great challenge. Wound medical devices (MDs) range from conventional and advanced dressings, up to skin grafts, but none of these are generally recognized as a gold standard. Based on recent developments, this paper reviews nanotechnology-based medical devices intended as skin substitutes. In particular, nanofibrous scaffolds are promising platforms for wound healing, especially due to their similarity to the extracellular matrix (ECM) and their capability to promote cell adhesion and proliferation, and to restore skin integrity, when grafted into the wound site. Nanotechnology-based scaffolds are emphasized here. The discussion will be focused on the definition of critical quality attributes (chemical and physical characterization, stability, particle size, surface properties, release of nanoparticles from MDs, sterility and apyrogenicity), the preclinical evaluation (biocompatibility testing, alternative in vitro tests for irritation and sensitization, wound healing test and animal wound models), the clinical evaluation and the CE (European Conformity) marking of nanotechnology-based MDs.