Research Techniques Made Simple: Animal Models of Wound Healing

Endothelial cell supplementation promotes xenograft revascularization during short-term ovarian tissue transplantation

The ischemic/hypoxic window after Ovarian Tissue Transplantation (OTT) can be responsible for the loss of more than 60 % of follicles. The implantation of the tissue supplemented with endothelial cells (ECs) inside dermal substitutes represents a promising strategy for improving graft revascularization. Ovarian biopsies were partly cryopreserved and partly digested to isolate ovarian ECs (OVECs). Four dermal substitutes (Integra®, made of bovine collagen enriched with chondroitin 6-sulfate; PELNAC®, composed of porcine collagen; Myriad Matrix®, derived from decellularized ovine forestomach; and NovoSorb® BMT, a foam of polyurethane) were compared for their angiogenic bioactive properties. OVECs cultured onto the scaffolds upregulated the expression of angiogenic factors, supporting their use in boosting revascularization. Adhesion and proliferation assays suggested that the most suitable scaffold was the bovine collagen one, which was chosen for further in vivo experiments. Cryopreserved tissue was transplanted onto the 3D scaffold in immunodeficient mice with or without cell supplementation, and after 14 days, it was analyzed by immunofluorescence (IF) and X-ray phase contrast microtomography. The revascularization area of OVECs-supplemented tissue was doubled (7.14 %) compared to the scaffold transplanted alone (3.67 %). Furthermore, tissue viability, evaluated by nuclear counting, was significantly higher (mean of 169.6 nuclei/field) in the tissue grafted with OVECs than in the tissue grafted alone (mean of 87.2 nuclei/field). Overall, our findings suggest that the OVECs-supplementation shortens the ischemic interval and may significantly improve fertility preservation procedures.

Controlled release of antimicrobial peptides from nanocellulose wound dressings for treatment of wound infections

Wounds are highly prone to infection, which can delay healing and lead to severe complications such as gangrene and sepsis. Non-healing wounds significantly impact patients' physical and mental well-being and place a substantial financial burden on healthcare systems. Timely and effective treatment of wound infections is critical, but the rise of antibiotic-resistant pathogens complicates this process. In this study, we investigate a potent protease resistant antimicrobial peptide (AMP), PLNC8 αβ, for the treatment of wound infections and present a strategy for localized AMP delivery using functionalized advanced nanocellulose (NC) wound dressings. Two types of NC dressings were explored: bacterial cellulose (BC) and TEMPO-oxidized nanocellulose derived from wood powder (TC). In a porcine wound infection model, PLNC8 αβ exhibited high antimicrobial activity, successfully eradicating the infection while promoting wound re-epithelialization. To achieve controlled release of PLNC8 αβ from the NC dressings, the peptides were either physisorbed directly onto the nanofibrils or encapsulated within mesoporous silica nanoparticles (MSNs) that were incorporated into the dressings. The PLNC8 αβ functionalized dressings demonstrated low cytotoxicity toward human primary fibroblasts and keratinocytes. Both BC and TC dressings showed efficient contact inhibition of bacteria but were less effective in inhibiting bacteria in suspension. In contrast, MSN-functionalized dressings, displayed significantly enhanced peptide-loading and sustained release capacities, resulting in improved antimicrobial efficacy. These findings highlight the potential of PLNC8 αβ and PLNC8 αβ-functionalized nanocellulose wound dressings for the treatment of infected wounds, offering an effective alternative to conventional antibiotic therapies.

Precision exosome engineering for enhanced wound healing and scar revision

The dysfunction of wound-healing processes can result in chronic non-healing wounds and pathological scar formation. Current treatment options often fall short, necessitating innovative approaches. Exosomes, extracellular vesicles secreted by various cells, have emerged as promising therapeutic agents serving as an intercellular communication system. By engineering exosomes, their cargo and surface properties can be tailored to enhance therapeutic efficacy and specificity. Engineered exosomes (eExo) are emerging as a favorable tool for treating non-healing wounds and pathological scars. In this review, we delve into the underlying mechanisms of non-healing wounds and pathological scars, outline the current state of engineering strategies, and explore the clinical potential of eExo based on preclinical and clinical studies. In addition, we address the current challenges and future research directions, including standardization, safety and efficacy assessments, and potential immune responses. In conclusion, eExo hold great promise as a novel therapeutic approach for non-healing wounds and non-healing wounds and pathological scars. Further research and clinical trials are warranted to translate preclinical findings into effective clinical treatments.

Exploring the Efficacy of Selected Allografts in Chronic Wound Healing: Evidence from Murine Models and Clinical Data for a Proposed Treatment Algorithm

Significance: Chronic wounds can lead to poor outcomes for patients, with risks, including amputation and death. In the United States, chronic wounds affect 2.5% of the population and cost up to $28 billion per year in primary health care costs. Recent Advances: Allograft tissues (dermal, amnion, and amnion/chorion) have shown efficacy in improving healing of chronic, recalcitrant wounds in human patients, as evidenced by multiple clinical trials. Their mechanisms of actions have been relatively understudied, until recently. Research in murine models has shown that dermal allografts promote reepithelialization, amnion allografts promote granulation tissue formation and angiogenesis, and amnion/chorion allografts support all stages of wound healing. These findings confirm their effectiveness and illuminate their therapeutic mechanisms. Critical Issues: Despite the promise of allografts in chronic wound care, a gap exists in understanding which allografts are most effective during each wound healing stage. The variable efficacy among each type of allograft suggests a mechanistic approach toward a proposed clinical treatment algorithm, based on wound characteristics and patient's needs, may be beneficial. Future Directions: Recent advances in allografts provide a framework for further investigations into patient-specific allograft selection. This requires additional research to identify which allografts support the best outcomes during each stage of wound healing and in which wound types. Longitudinal human studies investigating the long-term impacts of allografts, particularly in the remodeling phase, are also essential to developing a deeper understanding of their role in sustained wound repair and recovery.

Paw Skin as a Translational Model for Investigating Fibrotic and Inflammatory Wound Healing Defects in Recessive Dystrophic Epidermolysis Bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is a severe genetic disease caused by COL7A1 mutations. It leads to skin fragility, chronic inflammation, and impaired wound healing. The condition often results in fibrotic scarring, pseudosyndactyly, and cutaneous squamous cell carcinoma (SCC). However, current animal models fail to fully replicate chronic RDEB wounds. In this study, we used Collagen VII-hypomorphic mice (Col7a1flNeo/flNeo) and created full-thickness wounds on their paw skin, an area prone to fibrosis due to mechanical stress. We analyzed the healing process using histology, immunofluorescence, and electron microscopy. The RDEB mice showed delayed wound closure, increased inflammation, and poor granulation tissue formation. At 30 days post-injury, we observed persistent fibrosis, with elevated levels of Collagen I, α-SMA+ myofibroblasts, and tenascin-C. These mice also had fewer intraepidermal nerve fibers, which may help explain the neuropathic pain associated with RDEB. Our model reproduces the main features of chronic RDEB wounds. It offers a useful tool for evaluating therapies aimed at reducing inflammation, fibrosis, and tumor risk in these patients.

Pregnancy-specific glycoprotein 1 promotes wound closure in animal models

Recombinant human PSG1 administered intradermally at wound margins enhances skin wound healing in the mouse and pig, including in an acute diabetic mouse model. A highly significant effect on wound re-epithelialisation was observed in the pig, and PSG1 treatment of the human HaCaT keratinocyte cell line regulated wound healing-associated genes and enhanced scratch wound closure in cell monolayers in vitro. Clinical use of PSG1 might enhance closure of incisional and traumatic wounds and enhance re-epithelialisation of burn injuries.

Gelatin methacryloyl granular hydrogel scaffolds for skin wound healing

The pore size and structure of hydrogel scaffolds play a key role in regulating host-scaffold interactions. Incorporating macropores within bulk hydrogels may increase cell ingrowth and modulate scaffold-induced inflammation. To this end, granular hydrogel scaffolds (GHS) have been developed via assembling hydrogel microparticles (microgels). GHS have interconnected cell-scale pores, tailored by microgel size, which are readily accessible to cells. Although bulk gelatin methacryloyl (GelMA) hydrogel scaffolds have frequently been used for tissue regeneration, the efficacy of GelMA GHS in wound healing remains unknown. Here, GelMA GHS are fabricated using microfluidic-generated near-uniform microgels to study the effect of macropores on macrophage behavior in vitro, followed by assessing wound healing in a murine model of full thickness skin injury. Compared with the bulk hydrogel counterpart, macrophages interfaced with GHS secrete less interferon gamma (IFN-γ) and more insulin-like growth factor 1 (IGF-1), which show a transition to pro-healing activities. In addition, GelMA GHS improve the quality of wound healing via increasing the thickness of granulation tissue and downregulating inflammatory markers without affecting the wound closure rate. This work is a step forward in engineering GelMA scaffolds with tailored porosity for wound care.

Green synthesis of silver and gold nanoparticles using seeds extract of Cichorium intybus and their comparative analysis with commercially available ointment for wound healing activity

Wound healing is a complicated physiological process that involves several stages including hemostasis, inflammation, proliferation and repair to rebuild the integrity of the skin and subcutaneous tissue. Millions of people around the world are affected by poor wound healing, causing increased mortality rates and related costs. Immedicable wounds are a health problem because they directly affect the person's standard of living and produce an ultimatum to the health of people and the international economy because of the expensive medical treatment. Other schemes/approaches must be designed to achieve productive and therapeutic results. In this context, the emergence of Nano biotechnology may provide another manifesto to produce latest drugs for long-term treatment processes. This article shows that the implementation of metal nanoparticles (Au and Ag) has unbolted a brand-new gateway in the discipline of eco-friendly medicine due to their unique properties such as medicine transportation, antimicrobial activity and quick recovery. Moreover, metal nanoparticles (NPs) manufactured by green synthesis not only add the effects of nanoparticles and plant extracts but also reduce toxicity to tissues and make their use safer. In the present work, Ag and Au nanoparticles were synthesized using an aqueous seed extract of Cichorium intybus and their wound healing ability was assessed by performing in-vivo wound healing activity on albino mice. Till now there is no study available on the in-vivo wound healing potential of Ag and Au nanoparticles using Cichorium intybus. This is the first study ever to assess the ability of Cichorium intybus seed extract and its metal nanoparticles (AgNPs & AuNPs) to promote wound healing in animals which shows its uniqueness and novelty. The results displayed augmented and quicker wound closure with Ag as compared to the Au nanoparticles, polyfax and simple plant extract in a 21-day research work. These results illustrated that eco-friendly prepared nanoparticles provide a prominent approach to fight with the bacteria resistant against combination therapy without any lethal affair. Environment-friendly NPs declared to be the low-cost best treatment for the faster recovery of wounds. The main goal of this research is to provide aid in the creation of plant-based, durable and affordable Nano medicine for wound care, lowering dependency on synthetic techniques and encouraging environmental friendly biomedical applications.

Targeting S100A12 to Improve Angiogenesis and Accelerate Diabetic Wound Healing

Long-term inflammation and impaired angiogenesis are thought to be the causes of delayed healing or nonhealing of diabetic wounds. S100A12 is an essential pro-inflammatory factor involved in inflammatory reactions and serves as a biomarker for various inflammatory diseases. However, whether high level of S100A12 exists in and affects the healing of diabetic wounds, as well as the underlying molecular mechanisms, remain unclear. In this study, we found that the serum concentration of S100A12 is significantly elevated in patients with type 2 diabetes. Exposure of stratified epidermal cells to high glucose environment led to increased expression and secretion of S100A12, resulting in impaired endothelial function by binding to the advanced glycation endproducts (RAGE) or Toll-like receptor 4 (TLR4) on endothelial cell. The transcription factor Krüpple-like Factor 5 (KLF5) is highly expressed in the epidermis under high glucose conditions, activating the transcriptional activity of the S100A12 and boost its expression. By establishing diabetic wounds model in alloxan-induced diabetic rabbit, we found that local inhibition of S100A12 significantly accelerated diabetic wound healing by promoting angiogenesis. Our results illustrated the novel endothelial-specific injury function of S100A12 in diabetic wounds and suggest that S100A12 is a potential target for the treatment of diabetic wounds.

Differences in thickness of dermal layers in cranio-caudal anatomic locations in porcine skin wounds: Implications for wound healing studies

The use of the domesticated swine is important for advancing our understanding of healing in human skin due to the architectural similarities in their skin. In swine wound studies, skin thickness may play a role in healing due to the anatomical variation in the thickness of the different skin compartments, such as the dermis and subcutaneous fat, as well as the differences in anatomical location of the wounds. Here, the thickness of different skin compartments were measured in excisional wounds created in different anatomical locations along the cranio-caudal axis. Full-thickness, 2 cm diameter circular excisions were created on the dorsal paravertebral area of pigs. Thickness of the dermal and adipose layers of excised tissues at day 3 post-excision were measured in fixed H&E sections. Wound re-epithelialization was measured on excised day 10 wounds. A significant difference in skin thickness between the cranial wounds compared to the caudal wounds is noted in skin excised down to the landmark of the subcutaneous fascial plane. There were also significant differences in the thickness of the dermal and fat layers. Skin thickness, and the variations of the dermal and fat compartments, and locations of wounds should be taken into consideration in porcine wound studies as they may contribute to alterations in healing in the different locations.

Assessing New Collagen Therapies for Wound Healing: A Murine Model Approach

Collagen proteins play important roles in wound healing and are of great interest in regenerative medicine. This study evaluated the efficacy of new collagen-based products and compared them to commercial products in a murine model of cutaneous healing. Circular excisional defects were generated on 72 Wistar rats. Six study groups were established according to the administered collagen treatment: Control (without treatment), SD-C (semidenatured), Catrix, Hy-C (hydrolyzed), N-C (native) and Helix3-CP. Seven and eighteen days post-surgery, animals were euthanized. Wound closure was macroscopically assessed by taking zenithal images of the defects. Morphological, histological and immunohistochemical studies were performed to evaluate the healing process. After 7 days, open areas and degree of epithelialization were similar among the groups. Significant differences were observed in contraction between control and the N-C and Helix3-CP groups. Untreated animals exhibited a more pronounced granulation tissue with a high number of inflammatory cells and a disorganised extracellular matrix with type III collagen deposition. After 18 days, animals treated with new collagen (Hy-C and N-C) exhibited accelerated wound closure, increased epithelialization and a more organised granulation tissue. Local administration of new collagen treatments promotes the progression of the reparative process and significantly accelerates wound closure compared with nontreated wounds.

Using Three-Dimensional Bioprinting to Generate Realistic Models of Wound Healing

Significance: The skin serves as the primary defense against external stimuli, making it vulnerable to damage. Injuries can cause a dysregulated environment, resulting in chronic inflammation and inhibition of cell proliferation and migration, which delays recovery. Innovative approaches, such as three-dimensional (3D) bioprinting, can foster a controlled healing environment by promoting synergy between the skin microbiome and cells. Recent Advances: Traditional approaches to wound healing have focused on fostering an environment conducive to the interplay between cells, extracellular proteins, and growth factors. 3D bioprinting, a manufacturing technology with applications in tissue engineering, deposits biomaterial-based bioink containing living cells to fabricate custom-designed tissue scaffolds in a layer-by-layer fashion. This process controls the architecture and composition of a construct, producing multilayered and complex structures such as skin. Critical Issues: The selection of biomaterials for scaffolds has been a challenge when 3D skin tissue engineering. While prioritizing mechanical properties, current biomaterials often lack the ability to interact with environmental stimuli such as pH, temperature, or oxygen levels. Employing smart biomaterials that integrate bioactive molecules and adapt to external conditions could overcome these limitations. This innovation would enable scaffolds to create a sustainable wound-healing environment, fostering microbiome balance, reducing inflammation, and facilitating cellular recovery and tissue restoration, addressing critical gaps in existing wound care solutions. Future Directions: Novel bioink formulations for skin injury recovery are focused on improving long-term cell viability, proliferation, vascularization, and immune integration. Efficient recovery of the skin microbiome using bioactive molecules has the potential to create microenriched environments that support the recovery of the skin microbiome and restore immune regulation. This promising direction for future research aims to improve patient outcomes in wound care.

Creating an Extremely Long-lasting Neuroischemic Wound Model

In wound study and dressing development, a lack of a suitable animal model that can recapitulate the complex pathophysiology of human chronic wounds has been a major hurdle. Chronic wounds are defined as wounds that heal with a significant delay, usually over a period >2-3 months, but no current animal wound model has such a longischemia. After a longexploration, our group has developed an animal wound model with ischemia and nerve damage lasting for at least 6 months. This model can be easily combined with other conditions such as diabetes and aging for wound mechanistic study and critical testing of dressings. This report presents the method that has significant utility in evaluating therapies that could become the future standard for screening all new wound dressings.

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.

Therapeutic potential of exosomal lncRNAs derived from stem cells in wound healing: focusing on mesenchymal stem cells

The self-renewal ability and multipotency of stem cells give them great potential for use in wound healing. Stem cell-derived exosomes, owing to their close biological resemblance to their parent cells, offer a more efficient, safer, and economical approach for facilitating cellular communication and interactions within different environments. This potential makes them particularly valuable in the treatment of both acute and chronic wounds, such as lacerations, burns, and diabetic ulcers. Long non-coding RNAs (lncRNAs) enclosed in exosomes, as one of the leading actors of these extracellular microvesicles, through interaction with miRNAs and regulation of various signaling pathways involved in inflammation, angiogenesis, cell proliferation, and migration, could heal the wounds. Exosome-derived lncRNAs from stem cells facilitate extracellular matrix remodeling through interaction between macrophages and fibroblasts. Moreover, alongside regulating the expression of inflammatory cytokines, controlling reactive oxygen species levels, and enhancing autophagic activity, they also modulate immune responses to support wound healing. Regulating the expression of genes and signaling pathways related to angiogenesis, by increasing blood supply and accelerating the delivery of essential substances to the wound environment, is another effect exosomal lncRNAs derived from stem cells for wound healing. These lncRNAs can also enhance skin wound healing by regulating homeostasis, increasing the proliferation and differentiation of cells involved in the wound-healing process, and enhancing fibroblast viability and migration to the injury site. Ultimately, exosome-derived lncRNAs from stem cells offer valuable and novel insights into the molecular mechanisms underlying improved wound healing. They can pave the way for potential therapeutic strategies, fostering further research for a better future. Meanwhile, exosomes derived from mesenchymal stem cells, due to their exceptional regenerative properties, as well as the lncRNAs derived from these exosomes, have emerged as one of the innovative tools in wound healing. This review article aims to narrate the cellular and molecular roles of exosome-derived lncRNAs from stem cells in enhancing wound healing with a focus on mesenchymal stem cells.

Peripherally mediated opioid combination therapy in mouse and pig

The concomitant epidemics of chronic pain and opioid misuse in the United States have led to a call for novel analgesics with limited abuse potential. Previously, we have shown that co-delivery of a novel combination targeting both μ- and δ-opioid receptors in the peripheral and central nervous systems can produce synergistic analgesia. Loperamide, a peripherally restricted μ-opioid agonist, and oxymorphindole, a δ-opioid receptor partial agonist, synergize in multiple mouse models of hyperalgesia. We predicted this effect would generalize across species and therefore assessed this combination for analgesic synergy in a mouse model of post-incisional hypersensitivity. In mice, oxymorphindole and loperamide displayed significant analgesic synergy. Similar synergy was observed with N-benzyl-oxymorphindole and loperamide. In cross-bred pigs, we compared the analgesic effects of either morphine alone or the combination of oxymorphindole and loperamide or the combination of N-benzyl-oxymorphindole and loperamide. Both combinations showed increased potency as compared to morphine sulfate and effectively reduced hypersensitivity following injury without side effects. From these data we conclude that the combination of oxymorphindole and loperamide or the combination of N-benzyl-oxymorphindole and loperamide reverse incisional hyperalgesia, likely by acting in the periphery, in a large animal model without adverse effects on respiration or heart rate. PERSPECTIVE: This article presents novel opioid combinations, the μ-opioid agonist loperamide with a δ-opioid agonist, either oxymorphindole (OMI) or N-benzyl-oxymorphindole (BOMI), that relieve pain in mice and pigs without adverse side effects. These therapies could help clinicians manage pain in patients while reducing overall opioid burden and limiting side effects.

A Novel Crosslinking Approach for Biomanufacturing of a Collagen-Based Skin Dermal Template

Third-degree burns result in extensive damage to the skin's epidermal and dermal layers, with limited treatment options available. Currently, xenogeneic collagen-based skin grafts are used as scaffolds to integrate into the wound bed and provide a template for neodermis formation. Existing commercial products like Integra dermal templates rely on a time-consuming and variable dehydrothermal (DHT) crosslinking process. This study presents a novel crosslinking process for collagen sponges, utilizing UV irradiation followed by glutaraldehyde (GA) crosslinking. This UV method allows to fine-tune the template's crosslink density and degradation profile while significantly reducing the total crosslinking time from 48 to 24 h compared to DHT/GA crosslinking. In vitro characterization and in vivo validation are conducted using a full-thickness skin wound mouse model. The collagen template supports the human dermal fibroblast cell line WS-1 proliferation more effectively than the Integra template after 2 weeks in culture. Additionally, in vivo data indicate a similar level of regeneration of full-thickness skin wounds in mouse models between the sponge and Integra templates. Furthermore, the sponge template does not elicit any abnormal angiogenic or immune responses. The crosslinking approach offers a promising alternative production process for collagen sponge scaffolds.

Structural analysis and accelerating wound healing function of a novel galactosylated glycosaminoglycan from the snail Helix lucorum

Diabetic foot ulcers (DFUs) as a nonhealing wound remain a clinical challenge, and the development of pro-healing and cost-effective drugs is in urgent need. Herein, we reported a novel galactosylated glycosaminoglycan (GAG) from the snail Helix lucorum, as an effective pro-healing compound. The snail GAG is composed of a heparan sulfate-like main chain and galactose side chains at C-3 of GlcNAc residue. Its main chain has a repeating disaccharide structure of → 4)-α-D-GlcNAc-(1 → 4)-α-L-IdoA2S(1 →. This is the first example of glycosaminoglycan with galactose branches from mollusks. Pharmacological experiments showed that the H. lucorum GAG significantly promoted skin wound healing in both healthy and diabetic mice by accelerating granulation tissue regeneration, angiogenesis, and collagen deposition. The distinctive galactosylated substitution may play an important role on its pro-healing activity. Our discovery enriches the diversity of non-anticoagulant heparan sulfate-like glycosaminoglycans, and provides a potential candidate of pro-healing drug for treating diabetic wound.

Galleria mellonella (Greater Wax Moth) as a Reliable Animal Model to Study the Efficacy of Nanomaterials in Fighting Pathogens

The spread of multidrug-resistant microbes has made it necessary and urgent to develop new strategies to deal with the infections they cause. Some of these are based on nanotechnology, which has revolutionized many fields in medicine. Evaluating the safety and efficacy of these new antimicrobial strategies requires testing in animal models before being tested in clinical trials. In this context, Galleria mellonella could represent a valid alternative to traditional mammalian and non-mammalian animal models, due to its low cost, ease of handling, and valuable biological properties to investigate host-pathogen interactions. The purpose of this review is to provide an updated overview of the literature concerning the use of G. mellonella larvae as an animal model to evaluate safety and efficacy of nanoparticles and nanomaterials, particularly, of those that are used or are under investigation to combat microbial pathogens.

An injectable hydrogel of porcine cholecyst extracellular matrix for accelerated wound healing

Hydrogel formulations of xenogeneic extracellular matrices have been widely used for topical wound care because of their exceptional tunability over other formulations like lyophilized sheets, powders, non-injectable gels, pastes, and ointments. This is important in the treatment of wounds with irregular shapes and depth. This study identified an injectable hydrogel formulation of porcine cholecyst extracellular matrix (60%) in medical-grade carboxymethyl cellulose (40%) as vehicle and evaluated its biomaterial properties. Further, an in-depth evaluation of in vivo wound healing efficacy was conducted in a rat full-thickness skin excision wound healing model, which revealed that the hydrogel formulation accelerated wound healing process compared to wounds treated with a commercial formulation and untreated wounds. The hydrogel appeared to have promoted a desirable pro-regenerative tissue reaction predominated by Th2 helper lymphocytes and M2 macrophages as well as an effective collagen remodeling indicative of diminished scarring. In conclusion, the porcine cholecyst extracellular matrix injectable hydrogel formulation appeared to be a promising candidate formulation as an advanced wound care biomaterial for faster healing of skin wounds with minimal scarring.

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.

Advances in proteins, polysaccharides, and composite biomaterials for enhanced wound healing via microenvironment management: A review

Wound management is crucial yet imposes substantial social and economic burdens on patients and healthcare systems. The recent rapid advancements in biomaterials and manufacturing technology have created favorable conditions for expediting wound healing. This review examines the latest developments in biomacromolecule-based wound dressings, with a particular focus on proteins and polysaccharides, and their role in modulating the wound microenvironment. The importance of extracellular matrix (ECM)-inspired materials, such as hydrogels and biomimetic dressings, is emphasized. Additionally, this review explores the functionalization of wound dressings, emphasizing properties such as hemostatic capabilities, pain relief, antimicrobial activity, and innovative smart functions like electroceuticals and wound condition monitoring. The study integrates discussions on both the macroscopic healing outcomes and the microscopic pathophysiological mechanisms, highlighting recent advances in managing wound environments to expedite healing. Finally, the review critically assesses the challenges associated with the clinical translation of these wound-healing materials in the future.

Histomorphometric analysis of excisional cutaneous wounds with different diameters in an animal model

The skin wound model in rats is a fundamental stage in preclinical trials, but there is a lack of standardization in these trials regarding the initial wound area, making analysis and comparison between studies difficult. Therefore, this study evaluates the healing progression of excisional skin lesions of varying diameters in Wistar rats, aiming to identify the optimal wound size for monitoring treatment effects on wound healing. Excisions of 0.8, 1.5, 2.0 and 3.0 cm in diameter were made on the back of the animals. Thirty animals were used per treatment and evaluated on days 3, 7, 10, 14 and 21 after surgery. The lesions were cleaned daily with saline solution until they were completely closed. The 0.8 cm group showed complete repair on D14, while in the other groups, the wounds persisted until day 21, with a reddened surface and no complete epidermal coverage, but with greater keratinization and presence of appendages in the 1.5 cm lesions. Therefore, as a standardization model for creating skin wounds, we suggest using 1.5 or 2.0 cm excisions, considering that 0.8 cm wounds close very early and 3.0 cm wounds, although behaving similarly to 2.0 cm wounds, are more invasive for the animals. The 1.5 cm model proved to be suitable for closure within 21 days. When evaluating a product intended to accelerate wound healing, 2.0 cm lesions are recommended to assess the effectiveness of the treatment.

Preparation and characterization of Pistacia atlantica oleo-gum-resin-loaded electrospun nanofibers and evaluating its wound healing activity in two rat models of skin scar and burn wound

Background

A growing body of research is dedicated to developing new therapeutic agents for wound healing with fewer adverse effects. One of the proceedings being taken today in wound healing research is to identify promising biological materials that not only heal wounds but also vanish scarring. The effectiveness of nanofibers like polyvinyl alcohol (PVA), in improving wound healing can be related to their unique properties. Pistacia atlantica Desf. subsp. kurdica (Zohary) Rech. f. (PAK) [Anacardiaceae], also known as "Baneh" in traditional Iranian medicine, is one of the most effective herbal remedies for the treatment of different diseases like skin injuries due to its numerous pharmacological and biological properties, including anti-inflammatory, antioxidant, and anti-bacterial effects.

Purpose

Our study aimed to evaluate the wound-healing activity of nanofibers containing PVA/PAK oleo-gum-resin in two rat models of burn and excision wound repair.

Material and Methods

PVA/PKA nanofibers were prepared using the electrospinning method. Scanning electron microscope (SEM) images and mechanical properties of nanofibers were explored. Diffusion and releasing experiments of nanofibers were performed by the UV visible method at different time intervals and up to 72 h. The animal models were induced by excision and burn in Wistar rat's skin and the wound surface area was measured during the experiment for 10 and 21 days, respectively. On the last day, the wound tissue was removed for histological studies, and serum oxidative factors were measured to evaluate the antioxidant properties of the PVA/PKA. Data analysis was performed using ImageJ, Expert Design, and statistical analysis methods.

Results and discussion

PVA/PKA nanofibers were electrospun at different voltages (15, 18, and 20 kV). The most suitable fibers were obtained when the nozzle was positioned 15 cm away from the collector, with a working voltage of 15 kV, and an injection rate of 0.5 mm per hour, using the 30:70 w/v PKA gum. In the SEM images, it was found that the surface tension of the polymer solution decreased by adding the gum and yield thinner and longer fibers at a voltage of 15 kV with an average diameter of 96 ± 24 nm. The mechanical properties of PVA/PKA nanofibers showed that the presence of gum increased the tensile strength and decreased the tensile strength of the fibers simultaneously. In vivo results showed that PVA/PKA nanofibers led to a significant reduction in wound size and tissue damage (regeneration of the epidermal layer, higher density of dermal collagen fibers, and lower presence of inflammatory cells) compared to the positive (phenytoin and silver sulfadiazine) and negative control (untreated) groups. Wound contraction was higher in rats treated with PVA/PKA nanofibers. Additionally, antioxidative serum levels of catalase and glutathione were higher in the PVA/PKA nanofiber groups even in comparison to positive control groups.

Conclusion

Pistacia atlantica oleo-gum-resin-loaded electrospun nanofibers potentially improve excision and burn models of skin scars in rats through antioxidative and tissue regeneration mechanisms.

Forensic wound age estimation in dog tissue correlated with newly formed collagen fibres: a retrospective study

Parameters for wound age estimation are essential in forensic pathology but difficult to assess. With this retrospective study, wound age parameters in canine skin wounds were assessed with archive material of known age. Haematoxylin and eosin (HE) staining as standard, Prussian blue, Van Gieson (VG) and multiple other special stains were used as well as various immunohistochemistry (IHC) tests. Collagen fibre formation examination included HE staining but also immunolabelling for elastin and collagen I. Collagen fibre formation was further assessed by polarization in HE and VG. HE staining, erythrophagocytosis and presence of haemoglobin decay products in the Prussian blue stained-slides proved to be useful tools in wound age estimation in the early phase of wound repair of less than 5 days. The earliest detection of newly formed collagen was possible in 5-day-old wounds with HE and VG staining. Collagen I reactivity by IHC was weak at this time point, moderate to strong in the lesions older than 10 days and up to 30 days and strong in the lesions older than 3 months. Very slight polarization of collagen fibres was observed at 6 days, becoming stronger in wound lesions of 10-14 days and up to 30 days and reaching the same intensity as normal tissue in a 3-month-old lesion. The morphology of newly formed collagen fibres, utilizing HE and VG staining and polarization as well as collagen I IHC, which proved to be the most important parameters, correlated with distinguishable time points in the available cases of known wound age.

Comparison of different modern wound dressings on full-thickness murine cutaneous wound healing with wild-type and type-2 diabetes db/db mice

BACKGROUND

To evaluate the process of cutaneous wound healing, experiments have been conducted. However, to date, what modern wound dressings are suitable remains unclear. Therefore, this study aimed to compare the healing process in different modern wound dressings to determine their suitability in experimental acute wound and chronic diabetic wound.

MATERIALS AND METHODS

Twelve C57BL/6J mice and eleven db/db mice were subjected to full-thickness wound injuries. The mice were divided into the following four groups: hydrocolloid, form, film, and gauze groups in both wild-type and db/db mice. Wound healing was assessed until day 14.

RESULTS

In the wild-type groups, all wounds were healed and completed re-epithelialization by day 14. However, the wound surface was dry, and the periwound was hypercontracted in the wild-type-form and wild-type-gauze groups. In the db/db groups, wounds were not healed until day 14. Wound exudates in the db/db-hydrocolloid group were abundant and gradually increased until day 14. Wound exudates in the db/db-film group were present until day 14. Conversely, in the db/db-form and db/db-gauze groups, the wound surface was dry, and the periwound was hypercontracted.

CONCLUSION

These results showed that hydrocolloid and film dressings are suitable modern wound dressings for the mice wound models of acute wound and chronic diabetic wound. Moreover, using either hydrocolloid or film dressing depending on the purpose of the study on cutaneous wound healing in diabetes is necessary.

Development and characterization of contraction-suppressed full-thickness skin wound model in rabbits

The wound healing process in rodents (rats and mice) and lagomorphs (rabbits) predominantly relies on wound contraction rather than re-epithelialization and granulation tissue formation. As a result, existing laboratory animal models for wound healing often fail to mimic human wound healing mechanisms accurately. This study introduces a standardized rabbit model with superior translational potential for skin wound healing research. Two full-thickness dermal wounds were created on the posterior dorsal surface of each rabbit using a standard 2 ×2 cm² template. One of these wounds was randomly selected to be treated as a contraction-suppressed wound by applying a transparent adhesive elastic bandage. At the same time, the other was retained as a standard full-thickness wound. Wound contraction was measured on 7, 14, 21, 28, and 35 days. Histomorphological evaluation was done on day 35 to evaluate the quality of wound healing. The findings indicate that transparent adhesive elastic bandage prolonged the wound healing time and suppressed wound contraction in rabbits. In addition, the healed contraction-suppressed full-thickness wounds had denser and thicker collagen fibers than the healed standard full-thickness wounds, indicating better collagen fiber deposition. Our model achieved a 100 % success rate in maintaining the transparent adhesive elastic bandage in the rabbits. Therefore, we have developed a simple, non-invasive, cost-effective method for preventing wound contraction. Further studies are required to establish the utility of this model for studying wound healing mechanisms and evaluating therapeutic interventions.

OxInflammation Affects Transdifferentiation to Myofibroblasts, Prolonging Wound Healing in Diabetes: A Systematic Review

Skin wounds, primarily in association with type I diabetes mellitus, are a public health problem generating significant health impacts. Therefore, identifying the main pathways/mechanisms involved in differentiating fibroblasts into myofibroblasts is fundamental to guide research into effective treatments. Adopting the PRISMA guidelines, this study aimed to verify the main pathways/mechanisms using diabetic murine models and analyze the advances and limitations of this area. The Medline (PubMed), Scopus, and Web of Science platforms were used for the search. The studies included were limited to those that used diabetic murine models with excisional wounds. Bias analysis and methodological quality assessments were undertaken using the SYRCLE bias risk tool. Eighteen studies were selected. The systematic review results confirm that diabetes impairs the transformation of fibroblasts into myofibroblasts by affecting the expression of several growth factors, most notably transforming growth factor beta (TGF-beta) and NLRP3. Diabetes also compromises pathways such as the SMAD, c-Jun N-terminal kinase, protein kinase C, and nuclear factor kappa beta activating caspase pathways, leading to cell death. Furthermore, diabetes renders the wound environment highly pro-oxidant and inflammatory, which is known as OxInflammation. As a consequence of this OxInflammation, delays in the collagenization process occur. The protocol details for this systematic review were registered with PROSPERO: CRD42021267776.

Fabrication and Evaluation of a Soy Protein Isolate/Collagen/Sodium Alginate Multifunctional Bilayered Wound Dressing: Release of Cinnamaldehyde, Artemisia absinthium, and Oxygen

Chronic wounds, such as diabetic ulcers and pressure sores, pose significant challenges in modern healthcare due to their prolonged healing times and susceptibility to infections. This study aims to engineer a bilayered wound dressing (BLWD) composed of soy protein isolate/collagen with the ability to release Cinnamaldehyde, Artemisia absinthium (AA), and oxygen. Cinnamaldehyde, magnesium peroxide (MgO2), and AA extract were encapsulated. Nanoparticles were evaluated using scanning electron microscopy (SEM), dynamic light scattering, and ZETA potential tests. Swelling, degradation, water vapor penetration, tensile, MTT, SEM, oxygen release, AA extract release, and antibacterial properties were performed. An in vivo study was carried out to assess the final wound dressing under Hematoxiline&Eosin and Masson trichrome staining analysis and compared to a commercial product. According to the results, the synthesized nanoparticles had an average diameter of about 20 nm with a zeta potential in the range of -20 to -30 mV. The layers had uniform and dense surfaces. The maximum swelling and degradation of the dressing was about 130 and 13% respectively. Generally, better mechanical properties were observed in BLWD than in the single-layer case. More than 90% biocompatibility for the wound dressing was reported. The BLWD could inhibit the growth of Gram-positive and Gram-negative microorganisms. Histopathological analysis showed an acceptable wound-healing property. To sum up, the engineered wound dressing can be a good candidate for more clinical trials.

Lyophilized Polyvinyl Alcohol and Chitosan Scaffolds Pre-Loaded with Silicon Dioxide Nanoparticles for Tissue Regeneration

Materials with a soft tissue regenerative capacity can be produced using biopolymer scaffolds and nanomaterials, which allow injured tissue to recover without any side effects or limitations. Four formulations were prepared using polyvinyl alcohol (PVA) and chitosan (CS), with silicon dioxide nanoparticles (NPs-SiO2) incorporated using the freeze-drying method at a temperature of -50 °C. TGA and DSC showed no change in thermal degradation, with glass transition temperatures around 74 °C and 77 °C. The interactions between the hydroxyl groups of PVA and CS remained stable. Scanning electron microscopy (SEM) indicated that the incorporation of NPs-SiO2 complemented the freeze-drying process, enabling the dispersion of the components on the polymeric matrix and obtaining structures with a small pore size (between 30 and 60 μm) and large pores (between 100 and 160 μm). The antimicrobial capacity analysis of Gram-positive and Gram-negative bacteria revealed that the scaffolds inhibited around 99% of K. pneumoniae, E. cloacae, and S. aureus ATCC 55804. The subdermal implantation analysis demonstrated tissue growth and proliferation, with good biocompatibility, promoting the healing process for tissue restoration through the simultaneous degradation and formation of type I collagen fibers. All the results presented expand the boundaries in tissue engineering and regenerative medicine by highlighting the crucial role of nanoparticles in optimizing scaffold properties.

Replacing Animal Testing with Stem Cell-Organoids : Advantages and Limitations

Various groups including animal protection organizations, medical organizations, research centers, and even federal agencies such as the U.S. Food and Drug Administration, are working to minimize animal use in scientific experiments. This movement primarily stems from animal welfare and ethical concerns. However, recent advances in technology and new studies in medicine have contributed to an increase in animal experiments throughout the years. With the rapid increase in animal testing, concerns arise including ethical issues, high cost, complex procedures, and potential inaccuracies.Alternative solutions have recently been investigated to address the problems of animal testing. Some of these technologies are related to stem cell technologies, such as organ-on-a-chip, organoids, and induced pluripotent stem cell models. The aim of the review is to focus on stem cell related methodologies, such as organoids, that can serve as an alternative to animal testing and discuss its advantages and limitations, alongside regulatory considerations.Although stem cell related methodologies has shortcomings, it has potential to replace animal testing. Achieving this requires further research on stem cells, with potential societal and technological benefits.

Accelerated infected wound healing by probiotic-based living microneedles with long-acting antibacterial effect

Delays in infected wound healing are usually a result of bacterial infection and local inflammation, which imposes a significant and often underappreciated burden on patients and society. Current therapies for chronic wound infection generally suffer from limited drug permeability and frequent drug administration, owing to the existence of a wound biofilm that acts as a barrier restricting the entry of various antibacterial drugs. Here, we report the design of a biocompatible probiotic-based microneedle (MN) patch that can rapidly deliver beneficial bacteria to wound tissues with improved delivery efficiency. The probiotic is capable of continuously producing antimicrobial substances by metabolizing introduced glycerol, thereby facilitating infected wound healing through long-acting antibacterial and anti-inflammatory effects. Additionally, the beneficial bacteria can remain highly viable (>80 %) inside MNs for as long as 60 days at 4 °C. In a mouse model of Staphylococcus aureus-infected wounds, a single administration of the MN patch exhibited superior antimicrobial efficiency and wound healing performance in comparison with the control groups, indicating great potential for accelerating infected wound closure. Further development of live probiotic-based MN patches may enable patients to better manage chronically infected wounds.

Wound Healing Promotion via Release of Therapeutic Metallic Ions from Phosphate Glass Fibers: An In Vitro and Ex Vivo Study

Biomaterials capable of promoting wound healing and preventing infections remain in great demand to address the global unmet need for the treatment of chronic wounds. Phosphate-based glasses (PG) have shown potential as bioresorbable materials capable of inducing tissue regeneration, while being replaced by regenerated tissue and releasing therapeutic species. In this work, phosphate-glass-based fibers (PGF) in the system P2O5-CaO-Na2O added with 1, 2, 4, 6, and 10 mol % of the therapeutic metallic ions (TMI) Ag+, Zn2+, and Fe3+ were manufactured via electrospinning of coacervate gels. Coacervation is a sustainable, cost-effective, water-based method to produce PG. All TMI are effective in promoting wound closure (re-epithelialization) in living human skin ex vivo, where the best-performing system is PGF containing Ag+. In particular, PGF with ≥4 mol % of Ag+ is capable of promoting 84% wound closure over 48 h. These results are confirmed by scratch test migration assays, with the PGF-Ag systems containing ≥6 mol % of Ag+, demonstrating significant wound closure enhancement (up to 72%) after 24 h. The PGF-Ag systems are also the most effective in terms of antibacterial activity against both the Gram-positive Staphylococcus aureus and the Gram-negative Escherichia coli. PGF doped with Zn2+ shows antibacterial activity only against S. aureus in the systems containing Zn2+ ≥ 10 mol %. In addition, PGF doped with Fe3+ rapidly accelerates ex vivo healing in patient chronic wound skin (>30% in 48 h), demonstrating the utility of doped PGF as a potential therapeutic strategy to treat chronic wounds.

Review of Malaysian medicinal plants with potential wound healing activity

Wound is defined as the damage to biological tissues including skin, mucous membranes and organ tissues. The acute wound heals in less than 4 weeks without complications, while a chronic wound takes longer than 6 weeks to heal. Wound healing occurs in 4 phases, namely, coagulation, inflammatory, proliferative and remodeling phases. Triclosan and benzalkonium chloride are commonly used as skin disinfectants in wound healing. However, they cause allergic contact dermatitis and antibiotic resistance. Medicinal plants are widely studied due to the limited availability of wound healing agents. The present review included six commonly available medicinal plants in Malaysia such as Aloe barbadensis Miller, Carica papaya Linn., Centella asiatica Linn., Cymbopogon nardus Linn., Ficus benghalensis Linn. and Hibiscus rosa sinensis Linn. Various search engines and databases were used to obtain the scientific findings, including Google Scholar, ScienceDirect, PubMed Central and Research Gate. The review discussed the possible mechanism of action of medicinal plants and their active constituents in the wound healing process. In addition, their application in nanotechnology and wound dressings was also discussed in detail.

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.

Decellularized Umbilical Cord as a Scaffold to Support Healing of Full-Thickness Wounds

The umbilical cord is a material that enhances regeneration and is devoid of age-related changes in the extracellular matrix (ECM). The aim of this work was to develop a biodegradable scaffold from a decellularized human umbilical cord (UC-scaffold) to heal full-thickness wounds. Decellularization was performed with 0.05% sodium dodecyl sulfate solution. The UC-scaffold was studied using morphological analysis methods. The composition of the UC-scaffold was studied using immunoblotting and Fourier transform infrared spectroscopy. The adhesion and proliferation of mesenchymal stromal cells were investigated using the LIVE/DEAD assay. The local reaction was determined by subcutaneous implantation in mice (n = 60). A model of a full-thickness skin wound in mice (n = 64) was used to assess the biological activity of the UC-scaffold. The proposed decellularization method showed its effectiveness in the umbilical cord, as it removed cells and retained a porous structure, type I and type IV collagen, TGF-β3, VEGF, and fibronectin in the ECM. The biodegradation of the UC-scaffold in the presence of collagenase, its stability during incubation in hyaluronidase solution, and its ability to swell by 1617 ± 120% were demonstrated. Subcutaneous scaffold implantation in mice showed gradual resorption of the product in vivo without the formation of a dense connective tissue capsule. Epithelialization of the wound occurred completely in contrast to the controls. All of these data suggest a potential for the use of the UC-scaffold.

Plantar Skin Exhibits Altered Physiology, Constitutive Activation of Wound-Associated Phenotypes, and Inherently Delayed Healing

Wound research has typically been performed without regard for where the wounds are located on the body, despite well-known heterogeneities in physical and biological properties between different skin areas. The skin covering the palms and soles is highly specialized, and plantar ulcers are one of the most challenging and costly wound types to manage. Using primarily the porcine model, we show that plantar skin is molecularly and functionally more distinct from nonplantar skin than previously recognized, with unique gene and protein expression profiles, broad alterations in cellular functions, constitutive activation of many wound-associated phenotypes, and inherently delayed healing. This unusual physiology is likely to play a significant but underappreciated role in the pathogenesis of plantar ulcers as well as the last 25+ years of futility in therapy development efforts. By revealing this critical yet unrecognized pitfall, we hope to contribute to the development of more effective therapies for these devastating nonhealing wounds.

Modeling Wound Chronicity In Vivo: The Translational Challenge to Capture the Complexity of Chronic Wounds

In an aging society with common lifestyle-associated health issues such as obesity and diabetes, chronic wounds pose a frequent challenge that physicians face in everyday clinical practice. Therefore, nonhealing wounds have attracted much scientific attention. Several in vitro and in vivo models have been introduced to deepen our understanding of chronic wound pathogenesis and amplify therapeutic strategies. Understanding how wounds become chronic will provide insights to reverse or avoid chronicity. Although choosing a suitable model is of utmost importance to receive valuable outcomes, an ideal in vivo model capturing the complexity of chronic wounds is still missing and remains a translational challenge. This review discusses the most relevant mammalian models for wound healing studies and provides guidance on how to implement the hallmarks of chronic wounds. It highlights the benefits and pitfalls of established models and maps out future avenues for research.

Dermal Dive: An Overview of Cutaneous Wounding Techniques in Zebrafish

Cutaneous wounds are common injuries that affect millions of people around the world. In vulnerable populations such as the elderly and those with diabetes, defects in wound healing can lead to the development of chronic open wounds. Although mammalian models are commonly used to study cutaneous wound healing, the challenges of in vivo imaging in mammals have hampered detailed observation of cell coordination and cell signaling during wound healing. The zebrafish is becoming increasingly popular for studying cutaneous wound healing owing to its genetic accessibility, suitability for experimental manipulation, and the ability to perform live, in vivo imaging with cellular or even subcellular resolution. In this paper, we review some of the techniques that have been developed for eliciting cutaneous wounds in the zebrafish, including an economical method we recently developed using a rotary tool that generates consistent and reproducible full-thickness wounds. Combined with the thousands of transgenic lines and experimental assays available in zebrafish, the ability to generate reproducible cutaneous wounds makes it possible to study key cellular and molecular events during wound healing using this powerful experimental model organism.

A Novel Dehydrated Human Umbilical Cord Particulate Medical Device: Matrix Characterization, Performance, and Biocompatibility for the Management of Acute and Chronic Wounds

Chronic wounds present a significant socioeconomic burden forecasted to increase in prevalence and cost. Minimally manipulated human placental tissues have been increasingly employed and proven to be advantageous in the treatment of chronic wounds, showing improved clinical outcomes and cost-effectiveness. However, technological advances have been constrained by minimal manipulation and homologous use criteria. This study focuses on the characterization of a novel dehydrated human umbilical cord particulate (dHUCP) medical device, which offers a unique allogeneic technological advancement and the first human birth tissue device for wound management. Characterization analyses illustrated a complex extracellular matrix composition conserved in the dHUCP device compared to native umbilical cord, with abundant collagens and glycosaminoglycans imbibing an intricate porous scaffold. Dermal fibroblasts readily attached to the intact scaffold of the dHUCP device. Furthermore, the dHUCP device elicited a significant paracrine proliferative response in dermal fibroblasts, in contrast to fibrillar collagen, a prevalent wound device. Biocompatibility testing in a porcine full-thickness wound model showed resorption of the dHUCP device and normal granulation tissue maturation during healing. The dHUCP device is a promising advancement in wound management biomaterials, offering a unique combination of structural complexity adept for challenging wound topographies and a microenvironment supportive of tissue regeneration.

Promoting tissue repair using deferoxamine nanoparticles loaded biomimetic gelatin/HA composite hydrogel

To effectively address underlying issues and enhance the healing process of hard-to-treat soft tissue defects, innovative therapeutic approaches are required. One promising strategy involves the incorporation of bioactive substances into biodegradable scaffolds to facilitate synergistic tissue regeneration, particularly in vascular regeneration. In this study, we introduce a composite hydrogel design that mimics the extracellular matrix by covalently combining gelatin and hyaluronic acid (HA), with the encapsulation of deferoxamine nanoparticles (DFO NPs) for potential tissue regeneration applications. Crosslinked hydrogels were fabricated by controlling the ratio of HA in the gelatin-based hydrogels, resulting in improved mechanical properties, enhanced degradation ability, and optimised porosity, compared with hydrogel formed by gelatin alone. The DFO NPs, synthesized using a double emulsion method with poly (D,L-lactide-co-glycolide acid), exhibited a sustained release of DFO over 12 d. Encapsulating the DFO NPs in the hydrogel enabled controlled release over 15 d. The DFO NPs, composite hydrogel, and the DFO NPs loaded hydrogel exhibited excellent cytocompatibility and promoted cell proliferationin vitro. Subcutaneous implantation of the composite hydrogel and the DFO NPs loaded hydrogel demonstrated biodegradability, tissue integration, and no obvious adverse effects, evidenced by histological analysis. Furthermore, the DFO NPs loaded composite hydrogel exhibited accelerated wound closure and promoted neovascularisation and granular formation when tested in an excisional skin wound model in mice. These findings highlight the potential of our composite hydrogel system for promoting the faster healing of diabetes-induced skin wounds and oral lesions through its ability to modulate tissue regeneration processes.

In situ light-activated materials for skin wound healing and repair: A narrative review

Dermal wounds are a major global health burden made worse by common comorbidities such as diabetes and infection. Appropriate wound closure relies on a highly coordinated series of cellular events, ultimately bridging tissue gaps and regenerating normal physiological structures. Wound dressings are an important component of wound care management, providing a barrier against external insults while preserving the active reparative processes underway within the wound bed. The development of wound dressings with biomaterial constituents has become an attractive design strategy due to the varied functions intrinsic in biological polymers, such as cell instructiveness, growth factor binding, antimicrobial properties, and tissue integration. Using photosensitive agents to generate crosslinked or photopolymerized dressings in situ provides an opportunity to develop dressings rapidly within the wound bed, facilitating robust adhesion to the wound bed for greater barrier protection and adaptation to irregular wound shapes. Despite the popularity of this fabrication approach, relatively few experimental wound dressings have undergone preclinical translation into animal models, limiting the overall integrity of assessing their potential as effective wound dressings. Here, we provide an up-to-date narrative review of reported photoinitiator- and wavelength-guided design strategies for in situ light activation of biomaterial dressings that have been evaluated in preclinical wound healing models.

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.

Regenerative inflammation: When immune cells help to re-build tissues

Inflammation is an essential immune response critical for responding to infection, injury and maintenance of tissue homeostasis. Upon injury, regenerative inflammation promotes tissue repair by a timed and coordinated infiltration of diverse cell types and the secretion of growth factors, cytokines and lipids mediators. Remarkably, throughout evolution as well as mammalian development, this type of physiological inflammation is highly associated with immunosuppression. For instance, regenerative inflammation is the consequence of an in situ macrophage polarization resulting in a transition from pro-inflammatory to anti-inflammatory/pro-regenerative response. Immune cells are the first responders upon injury, infiltrating the damaged tissue and initiating a pro-inflammatory response depleting cell debris and necrotic cells. After phagocytosis, macrophages undergo multiple coordinated metabolic and transcriptional changes allowing the transition and dictating the initiation of the regenerative phase. Differences between a highly efficient, complete ad integrum tissue repair, such as, acute skeletal muscle injury, and insufficient regenerative inflammation, as the one developing in Duchenne Muscular Dystrophy (DMD), highlight the importance of a coordinated response orchestrated by immune cells. During regenerative inflammation, these cells interact with others and alter the niche, affecting the character of inflammation itself and, therefore, the progression of tissue repair. Comparing acute muscle injury and chronic inflammation in DMD, we review how the same cells and molecules in different numbers, concentration and timing contribute to very different outcomes. Thus, it is important to understand and identify the distinct functions and secreted molecules of macrophages, and potentially other immune cells, during tissue repair, and the contributors to the macrophage switch leveraging this knowledge in treating diseases.

Bioactive nanomaterials kickstart early repair processes and potentiate temporally modulated healing of healthy and diabetic wounds

Slow-healing and chronic wounds represent a major global economic and medical burden, and there is significant unmet need for novel therapies which act to both accelerate wound closure and enhance biomechanical recovery of the skin. Here, we report a new approach in which bioactives that augment early stages of wound healing can kickstart and engender effective wound closure in healthy and diabetic, obese animals, and set the stage for subsequent tissue repair processes. We demonstrate that a nanomaterial dressing made of silk fibroin and gold nanorods (GNR) stimulates a pro-neutrophilic, innate immune, and controlled inflammatory wound transcriptomic response. Further, Silk-GNR, lasered into the wound bed, in combination with exogeneous histamine, accelerates early-stage processes in tissue repair leading to effective wound closure. Silk-GNR and histamine enhanced biomechanical recovery of skin, increased transient neoangiogenesis, myofibroblast activation, epithelial-to-mesenchymal transition (EMT) of keratinocytes and a pro-resolving neutrophilic immune response, which are hitherto unknown activities for these bioactives. Predictive and temporally coordinated delivery of growth factor nanoparticles that modulate later stages of tissue repair further accelerated wound closure in healthy and diabetic, obese animals. Our approach of kickstarting healing by delivering the "right bioactive at the right time" stimulates a multifactorial, pro-reparative response by augmenting endogenous healing and immunoregulatory mechanisms and highlights new targets to promote tissue repair.

In Vivo Evaluation of Wound Healing Efficacy of Gel-Based Dressings Loaded with Pycnogenol™ and Ceratothoa oestroides Extracts

Ceratothoa oestroides and French maritime pine bark (Pycnogenol™) extracts are considered promising therapeutic agents in wound healing. This study explores the healing efficacy of composite dressings containing these extracts, aiming to enhance their stability and effectiveness, utilizing a low-temperature vacuum method for producing Sodium Alginate-Maltodextrin gel dressings. Surgical wounds were inflicted on SKH-hr2 hairless mice. Dressings were loaded with Pycnogenol™ and/or C. oestroides extracts and assessed for their efficacy. Wound healing was primarily evaluated by clinical and histopathological evaluation and secondarily by Antera 3D camera and biophysical measurements. Dressings were stable and did not compromise the therapeutic properties of C. oestroides extract. All interventions were compared to the C. oestroides ointment as a reference product. Most of the wounds treated with the reference formulation and the C. oestrodes dressing had already closed by the 15th day, with histological scores of 7 and 6.5, respectively. In contrast, wounds treated with Pycnogenol™, either alone or in combination with C. oestroides, did not close by the end of the experiment (16th day), with histological scores reaching 15 in both cases. Furthermore, treatment with 5% Pycnogenol™ dressing appeared to induce skin thickening and increase body temperature. The study underscores the wound healing potential of C. oestroides extracts and highlights the need for further research to optimize Pycnogenol™ dosing in topical applications.

Staphopain mediated virulence and antibiotic resistance alteration in co-infection of Staphylococcus aureus and Pseudomonas aeruginosa: an animal model

Polymicrobial communities lead to worsen the wound infections, due to mixed biofilms, increased antibiotic resistance, and altered virulence production. Promising approaches, including enzymes, may overcome the complicated condition of polymicrobial infections. Therefore, this study aimed to investigate Staphopain A-mediated virulence and resistance alteration in an animal model of Staphylococcus aureus and Pseudomonas aeruginosa co-infection. S. aureus and P. aeruginosa were co-cultured on the L-929 cell line and wound infection in an animal model. Then, recombinant staphopain A was purified and used to treat mono- and co-infections. Following the treatment, changes in virulence factors and resistance were investigated through phenotypic methods and RT-PCR. Staphopain A resulted in a notable reduction in the viability of S. aureus and P. aeruginosa. The biofilm formed in the wound infection in both animal model and cell culture was disrupted remarkably. Moreover, the biofilm-encoding genes, quorum sensing regulating genes, and virulence factors (hemolysin and pyocyanin) controlled by QS were down-regulated in both microorganisms. Furthermore, the resistance to vancomycin and doripenem decreased following treatment with staphopain A. According to this study, staphopain A might promote wound healing and cure co-infection. It seems to be a promising agent to combine with antibiotics to overcome hard-to-cure infections.

Multilayer PVA/gelatin nanofibrous scaffolds incorporated with Tanacetum polycephalum essential oil and amoxicillin for skin tissue engineering application

Wound infection is still an important challenge in healing of different types of skin injuries. This highlights the need for new and improved antibacterial agents with novel and different mechanisms of action. In this study, by electrospinning process Tanacetum polycephalum essential oil (EO), as a natural antibacterial and anti-inflammatory agent, along with Amoxicillin (AMX) as an antibiotic are incorporated into PVA/gelatin-based nanofiber mats individually and in combination to fabricate a novel wound dressing. Briefly, we fabricated PVA/gelatin loaded by Amoxicillin as first layer for direct contact with wound surface to protects the wound from exogenous bacteria, and then built a PVA/gelatin/Tanacetum polycephalum essential oil layer on the first layer to help cleanses the wound from infection and accelerates wound closure. Finally, PVA/gelatin layer as third layer fabricated on middle layer to guarantee desirable mechanical properties. For each layer, the electrospinning parameters were adjusted to form bead-free fibers. The morphology of fabricated nanofiber scaffolds was characterized by Fourier-transform infrared (FTIR) and scanning electron microscopy (SEM). Microscopic images demonstrated the smooth bead-free microstructures fabrication of every layer of nanofiber with a uniform fiber size of 126.888 to 136.833 nm. While, EO and AMX increased the diameter of nanofibers but there was no change in physical structure of nanofiber. The water contact angle test demonstrated hydrophilicity of nanofibers with 47.35°. Although EO and AMX had little effect on reducing hydrophilicity but nanofibers with contact angle between 51.4° until 65.4° are still hydrophilic. Multilayer nanofibers loaded by EO and AMX killed 99.99 % of both gram-negative and gram-positive bacteria in comparison with control and PVA/gelatin nanofiber. Also, in addition to confirming the non-toxicity of nanofibers, MTT results also showed the acceleration of cell proliferation. In vivo wound evaluation in mouse models showed that designed nanofibrous scaffolds could be an appropriate option for wound treatment due to their positive effect on angiogenesis, collagen deposition, granulation tissue formation, epithelialization, and wound closure.

Chitosan-polygalacturonic acid complex dressing improves diabetic wound healing and hair growth in diabetic mice

Chronic skin wounds decrease the quality of life of millions of diabetic patients worldwide. Chitosan has previously been shown to possess hemostatic properties, decrease inflammation, promote fibroblast proliferation, and hair growth. We developed a relatively low-cost polyelectrolyte complex (PEC) film dressing made of chitosan and polygalacturonic acid and tested it for its ability to accelerate diabetic wound healing. Genetically diabetic male mice were shaved on the dorsum, and one day later a 1 cm diameter full-thickness excisional wound was created. The PEC film was applied immediately after wounding and left in place for 14 days. Controls consisted of wounds treated with a fibrin gel. Wounds covered with the PEC film had closed completely by post-wounding day 42, while untreated wounds were only half-way closed. Histological analysis of wounds confirmed that PEC-treated wounds had fully re-epithelialized, while control wounds lacked a continuous epidermis at the wound center. We also observed that the area of skin under the PEC film experienced much more rapid hair growth. Histologically, there were significantly more hair follicles around the scar area (p < 0.05) in the PEC-treated group as compared to the control group. Thus, chitosan-polygalacturonic acid PEC films can accelerate both wound healing and hair growth in diabetic mice, and should be further investigated as a potential future treatment for diabetic chronic wounds.

Inhibition of the CoREST Repressor Complex Promotes Wound Re-Epithelialization through the Regulation of Keratinocyte Migration

Wound healing is a complex process involving phases of hemostasis, inflammation, proliferation, and remodeling. The regenerative process in the skin requires coordination between many regulators, including signaling molecules, transcription factors, and the epigenetic machinery. In this study, we show that chromatin regulators HDAC1 and LSD1, key components of the CoREST repressor complex, are upregulated in the regenerating epidermis during wound repair. We also show that corin, a synthetic dual inhibitor of the CoREST complex and HDAC1/LSD1 activities, significantly accelerates wound closure through enhanced re-epithelialization in a mouse tail wound model. Acetylated H3K9 (methylation of histone H3 at lysine 9) expression, a histone modification targeted by HDAC1, is increased in keratinocytes after topical treatment with 100 nM and 1 μM of corin. In vitro experiments demonstrate that corin promotes migration and inhibits the proliferation of human keratinocytes. Furthermore, expression levels of genes promoting keratinocyte migration, such as AREG, CD24, EPHB2, ITGAX, PTGS, SCT1, SERPINB2, SERPINE1, SLPI, SNAI2, and TWIST, increased in keratinocytes treated with corin. These data demonstrate that dual inhibition of class I histone deacetylases and LSD1 by corin may serve as a new approach for promoting wound re-epithelialization and provide a platform for further applications of corin for the treatment of chronic wounds.