Improved diabetic wound healing by LFcinB is associated with relevant changes in the skin immune response and microbiota

Real-time OXPHOS capacity analysis in wounded skin from diabetic mice: A pilot study

INTRODUCTION

Diabetes mellitus (DM) impairs wound healing. The aim was to determine whether DM influences mitochondrial respiration in wounded skin (WS) and non-wounded skin (NWS), in a pre-clinical wound healing model of streptozotocin (STZ)-induced diabetes.

METHODS

Six weeks after diabetes induction, two wounds were created in the back of C57BL/J6 mice. Using high-resolution respirometry (HRR), oxygen flux was measured, in WS and NWS, using two substrate-uncoupler-inhibitor titration protocols, at baseline (day 0), day 3 and 10 post-wounding, in STZ-DM and non-diabetic (NDM) mice. Flux control ratios for the oxidative phosphorylation (OXPHOS) capacity were calculated.

RESULTS

A significant increase in mitochondrial respiration was observed in STZ-DM skin compared to control skin at baseline. The OXPHOS capacity was decreased in WS under diabetes at day 3 post-wounding (inflammation phase). However, at day 10 post-wounding (remodeling phase), the OXPHOS capacity was higher in WS from STZ-DM compared to NDM mice, and compared to NWS from STZ-DM mice. A significant relative contribution of pyruvate, malate and glutamate (PMG) oxidation to the OXPHOS capacity was observed in WS compared to NWS from STZ-DM mice, at day 10, while the relative contribution of fatty acid oxidation to the OXPHOS capacity was higher in NWS. The OXPHOS capacity is altered in WS from STZ-DM compared to NDM mice across the healing process, and so is the substrate contribution in WS and NWS from STZ-DM mice, at each time point.

CONCLUSION

HRR may be a sensitive tool to evaluate the underlying mechanisms of tissue repair during wound healing.

What is the effect of lactoferrin on oral and jawbone tissue repair? A systematic review

Currently, there is growing interest in the potential use of lactoferrin (LTF), a member of the transferrin family, for the improvement of tissue healing. In this sense, a literature search was conducted to integrate data published on the effect of LTF on jawbone repair. PubMed/MEDLINE, Scopus, Embase, Web of Science, LILACS, and Cochrane databases were retrieved according to the PRISMA 2020 statement. Articles in English, Spanish, and Portuguese were recovered, with no year restriction. In vitro, in vivo, and clinical studies were selected. A total of 742 articles were retrieved, 11 of which met the inclusion criteria (5 in vitro and 5 in vivo studies, and one clinical trial). The included data demonstrated wide variations in study design and LTF therapy protocols. Cell proliferation and viability were the primary outcomes evaluated in the in vitro studies, all of which reported a potential effect of LTF on the repair process. Of three in vivo studies, one reported a reduction in the overall healing rate, whereas the other two showed that LTF inhibited bone resorption and increased bone formation. The clinical trial's findings showed that LTF is a potential promoter of wound repair in patients with medication-related osteonecrosis of the jaws. Overall, data from the studies support a potential effect of LTF therapy on the process of jawbone repair.

Fabrication and Characterization of an Enzyme-Triggered, Therapeutic-Releasing Hydrogel Bandage Contact Lens Material

PURPOSE

The purpose of this study was to develop an enzyme-triggered, therapeutic-releasing bandage contact lens material using a unique gelatin methacrylate formulation (GelMA+).

METHODS

Two GelMA+ formulations, 20% w/v, and 30% w/v concentrations, were prepared through UV polymerization. The physical properties of the material, including porosity, tensile strain, and swelling ratio, were characterized. The enzymatic degradation of the material was assessed in the presence of matrix metalloproteinase-9 (MMP-9) at concentrations ranging from 0 to 300 µg/mL. Cell viability, cell growth, and cytotoxicity on the GelMA+ gels were evaluated using the AlamarBlueTM assay and the LIVE/DEADTM Viability/Cytotoxicity kit staining with immortalized human corneal epithelial cells over 5 days. For drug release analysis, the 30% w/v gels were loaded with 3 µg of bovine lactoferrin (BLF) as a model drug, and its release was examined over 5 days under various MMP-9 concentrations.

RESULTS

The 30% w/v GelMA+ demonstrated higher crosslinking density, increased tensile strength, smaller pore size, and lower swelling ratio (p < 0.05). In contrast, the 20% w/v GelMA+ degraded at a significantly faster rate (p < 0.001), reaching almost complete degradation within 48 h in the presence of 300 µg/mL of MMP-9. No signs of cytotoxic effects were observed in the live/dead staining assay for either concentration after 5 days. However, the 30% w/v GelMA+ exhibited significantly higher cell viability (p < 0.05). The 30% w/v GelMA+ demonstrated sustained release of the BLF over 5 days. The release rate of BLF increased significantly with higher concentrations of MMP-9 (p < 0.001), corresponding to the degradation rate of the gels.

DISCUSSION

The release of BLF from GelMA+ gels was driven by a combination of diffusion and degradation of the material by MMP-9 enzymes. This work demonstrated that a GelMA+-based material that releases a therapeutic agent can be triggered by enzymes found in the tear fluid.

Sodium alginate/poly(vinyl alcohol)/taxifolin nanofiber mat promoting diabetic wound healing by modulating the inflammatory response, angiogenesis, and skin flora

Diabetes-related ulcers are still a therapeutic problem because of their susceptibility to infection, ongoing inflammation, and diminished vascularization. The design and development of novel dressings are clinically urgent for the treatment of chronic wounds due to diabetic ulcers. In this study, we made taxifolin (TAX) loaded sodium alginate (SA)/poly(vinyl alcohol) (PVA) nanofibers for the treatment of chronic wounds. The SA/PVA/TAX nanofibers that have been created are smooth and bead-free, with good thermal stability, hydrophilicity, and mechanical properties. The release profile indicated a sustained drug release, with a cumulative release rate of 64.6 ± 3.7 % at 24 h. In vitro experiments have shown that SA/PVA/TAX has good antibacterial activity, antioxidant activity, and biocompatibility. In vivo experiments have shown that SA/PVA/TAX exhibits desirable biochemical properties and is involved in the diabetic wound healing process by promoting cell proliferation (Ki67), angiogenesis (CD31, VEGFA), and alleviating inflammation (CD68). Western blotting experiments suggest that SA/PVA/TAX may promote diabetic wound healing by inhibiting the TLR4/NF-κB/NLRP3 signaling pathway and upregulating the expression of VEGFA and PDGFA. The 16S rRNA sequencing results showed that SA/PVA/TAX increased the wound surface flora's diversity and reversed the skin microbiota's structural imbalance. Therefore, SA/PVA/TAX can promote diabetic wound healing by modulating the inflammatory response, angiogenesis, and skin flora and has the potential to be an excellent wound dressing.

Chitosan hydrogels with MK2 inhibitor peptide-loaded nanoparticles to treat atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disorder that lacks ideal long-term treatment options due to a series of side effects, such as skin atrophy, related to the most common treatment prescribed to manage moderate-to-severe AD. In this study, a cell-penetrating MK2 inhibitor peptide YARA (YARAAARQARAKALNRQGLVAA) was loaded into hollow thermo-responsive pNIPAM nanoparticles (NP), which were further incorporated into chitosan hydrogels (H-NP-YARA) to promote local drug delivery, improve moisture and the anti-inflammatory activity. The NPs exhibited high loading efficiency (>50%) and the hydrogel remained porous following NP incorporation as observed by scanning electron microscopy (SEM). Both nanoparticles and hydrogels were able to improve the release of YARA and sustained release to up to 120 h. The hydrogels and NPs delivered 2 and 4-fold more YARA into viable skin layers of porcine skin in vitro at 12 h post-application than the non-encapsulated compound in intact and impaired barrier conditions. Furthermore, the YARA-loaded NPs (NP-YARA) and H-NP-YARA treatment decreased the levels of inflammatory cytokines up to 20 time-fold compared with the non-treated group of human keratinocytes under inflammatory conditions. Consistent with the results in cell culture, the loading of YARA in NP reduced the levels of IL-1β, IL-6, and TNF-α up to 3.3 times in an ex vivo skin culture model after induction of inflammation. A further decrease of up to 17 times-fold was observed with H-NP-YARA treatment compared to the drug in solution. Our data collectively suggest that chitosan hydrogel containing YARA-loaded nanoparticles is a promising new formulation for the topical treatment of AD.

Skin Microbiota and the Cosmetic Industry

Skin harbors an important microbial ecosystem - the skin microbiota that is in homeostasis with its host and is beneficial for human health. Cosmetic products have the potential to interfere with this microbial community; therefore their impact should be assessed. The aim of this review is to highlight the importance of skin microbiota in the cosmetic industry. Several studies determined that cosmetic ingredients have the potential to disrupt the skin microbiota equilibrium leading to the development of skin diseases and dysregulation of immune response. These studies led their investigation by using different methodologies and models, concluding that methods must be chosen according to the aim of the study, the skin site to be evaluated, and the target population of the cosmetics. Overall, it is crucial to test the impact of cosmetics in the skin microbiota and to stablish standard procedures, as well as specific criteria that allow to classify a cosmetic product as skin microbiota friendly.

No country for old antibiotics! Antimicrobial peptides (AMPs) as next-generation treatment for skin and soft tissue infection

In recent years, the unprecedented rise of bacterial antibiotic resistance together with the lack of adequate therapies have made the treatment of skin infections and chronic wounds challenging, urging the scientific community to focus on the development of new and more efficient treatment strategies. In this context, there is a growing interest in the use of natural molecules with antimicrobial features, capable of supporting wound healing i.e., antimicrobial peptides (AMPs), for the treatment of skin and soft tissue infections. In this review, we give a short overview of the bacterial skin infections as well as some of the classic treatments used for topical application. We then summarize the AMPs classes, stressing the importance of the appropriate selection of the peptides based on their characteristics and physicochemical properties in order to maximize the antibacterial efficacy of the therapeutic systems against multi-drug resistant pathogens. Additionally, the present paper provides a comprehensive and rigorous assessment of the latest clinical trials investigating the efficacy of AMPs in the treatment of skin and soft tissue infections, highlighting the relevant outcomes. Seeking to obtain novel and improved compounds with synergistic activity, while also decreasing some of the known side effects of AMPs, we present two employed strategies using AMPs: (i) AMPs-conjugated nanosystems for systemic and topical drug delivery systems and (ii) antibiotics-peptide conjugates as a strategy to overcome antibiotics resistance. Finally, an important property of some of the AMPs used in wound treatment is highlighted: their ability to help in wound healing by generally promoting cell proliferation and migration, and in some cases re-epithelialization and angiogenesis among others. Thus, as the pursuit of improvement is an ongoing effort, this work presents the advances made in the treatment of skin and soft tissue infections along with their advantages and limitations, while the still remaining challenges are addressed by providing future prospects and strategies to overcome them.

Breakthrough treatments for accelerated wound healing

Skin injuries across the body continue to disrupt everyday life for millions of patients and result in prolonged hospital stays, infection, and death. Advances in wound healing devices have improved clinical practice but have mainly focused on treating macroscale healing versus underlying microscale pathophysiology. Consensus is lacking on optimal treatment strategies using a spectrum of wound healing products, which has motivated the design of new therapies. We summarize advances in the development of novel drug, biologic products, and biomaterial therapies for wound healing for marketed therapies and those in clinical trials. We also share perspectives for successful and accelerated translation of novel integrated therapies for wound healing.

Colonizing microbiota is associated with clinical outcomes in diabetic wound healing

With the development of society and the improvement of life quality, more than 500 million people are affected by diabetes. More than 10 % of people with diabetes will suffer from diabetic wounds, and 80 % of diabetic wounds will reoccur, so the development of new diabetic wound treatments is of great importance. The development of skin microbe research technology has gradually drawn people's attention to the complex relationship between microbes and diabetic wounds. Many studies have shown that skin microbes are associated with the outcome of diabetic wounds and can even be used as one of the indicators of wound prognosis. Skin microbes have also been found to have the potential to treat diabetic wounds. The wound colonization of different bacteria can exert opposing therapeutic effects. It is necessary to fully understand the skin microbes in diabetic wounds, which can provide valuable guidance for clinical diabetic wound treatment.

A Review of Immunomodulatory Reprogramming by Probiotics in Combating Chronic and Acute Diabetic Foot Ulcers (DFUs)

Diabetic foot ulcers (DFUs) are characterized by a lack of angiogenesis and distal limb diabetic neuropathy. This makes it possible for opportunistic pathogens to protect the biofilm-encased micro-communities, causing a delay in wound healing. The acute and chronic phases of DFU-associated infections are distinguished by the differential expression of innate proinflammatory cytokines and tumor necrosis factors (TNF-α and -β). Efforts are being made to reduce the microbial bioburden of wounds by using therapies such as debridement, hyperbaric oxygen therapy, shock wave therapy, and empirical antibiotic treatment. However, the constant evolution of pathogens limits the effectiveness of these therapies. In the wound-healing process, continuous homeostasis and remodeling processes by commensal microbes undoubtedly provide a protective barrier against diverse pathogens. Among commensal microbes, probiotics are beneficial microbes that should be administered orally or topically to regulate gut-skin interaction and to activate inflammation and proinflammatory cytokine production. The goal of this review is to bridge the gap between the role of probiotics in managing the innate immune response and the function of proinflammatory mediators in diabetic wound healing. We also highlight probiotic encapsulation or nanoformulations with prebiotics and extracellular vesicles (EVs) as innovative ways to tackle target DFUs.

Reprograming the immune niche for skin tissue regeneration - From cellular mechanisms to biomaterials applications

Despite the rapid development of therapeutic approaches for skin repair, chronic wounds such as diabetic foot ulcers remain an unaddressed problem that affects millions of people worldwide. Increasing evidence has revealed the crucial and diverse roles of the immune cells in the development and repair of the skin tissue, prompting new research to focus on further understanding and modulating the local immune niche for comprehensive, 'perfect' regeneration. In this review, we first introduce how different immunocytes and certain stromal cells involved in innate and adaptive immunity coordinate to maintain the immune niche and tissue homeostasis, with emphasis on their specific roles in normal and pathological wound healing. We then discuss novel engineering approaches - particularly biomaterials systems and cellular therapies - to target different players of the immune niche, with three major aims to i) overcome 'under-healing', ii) avoid 'over-healing', and iii) promote functional restoration, including appendage development. Finally, we highlight how these strategies strive to manage chronic wounds and achieve full structural and functional skin recovery by creating desirable 'soil' through modulating the immune microenvironment.

Restoring Pro-healing/remodeling- associated M2a/c Macrophages using ON101 Accelerates Diabetic Wound Healing

Diabetic wounds exhibit chronic inflammation and delayed tissue proliferation or remodeling, mainly owing to prolonged proinflammatory (M1) macrophage activity and defects in transition to prohealing/proremodeling (M2a/M2c; CD206⁺ and/or CD163⁺) macrophages. We found that topical treatment with ON101, a plant-based potential therapeutic for diabetic foot ulcers, increased M2c-like (CD163⁺ and CD206⁺) cells and suppressed M1-like cells, altering the inflammatory gene profile in a diabetic mouse model compared with that in the controls. An in vitro macrophage-polarizing model revealed that ON101 directly suppressed CD80⁺ and CD86⁺ M1-macrophage polarization and M1-associated proinflammatory cytokines at both protein and transcriptional levels. Notably, conditioned medium collected from ON101-treated M1 macrophages reversed the M1-conditioned medium‒mediated suppression of CD206⁺ macrophages. Furthermore, conditioned medium from ON101-treated adipocyte progenitor cells significantly promoted CD206⁺ and CD163⁺ macrophages but strongly inhibited M1-like cells. ON101 treatment also stimulated the expression of GCSF and CXCL3 genes in human adipocyte progenitor cells. Interestingly, treatment with recombinant GCSF protein enhanced both CD206⁺ and CD163⁺ M2 markers, whereas CXCL3 treatment only stimulated CD163⁺ M2 macrophages. Depletion of cutaneous M2 macrophages inhibited ON101-induced diabetic wound healing. Thus, ON101 directly suppressed M1 macrophages and facilitated the GCSF- and CXCL3-mediated transition from M1 to M2 macrophages, lowering inflammation and leading to faster diabetic wound healing.

Prospects and Applications of Natural Blood-Derived Products in Regenerative Medicine

Currently, there are a number of therapeutic schemes used for the treatment of various types of musculoskeletal disorders. However, despite the use of new treatment options, therapeutic failure remains common due to impaired and delayed healing, or implant rejection. Faced with this challenge, in recent years regenerative medicine started looking for alternative solutions that could additionally support tissue regeneration. This review aims to outline the functions and possible clinical applications of, and future hopes associated with, using autologous or heterologous products such as antimicrobial peptides (AMPs), microvesicles (MVs), and neutrophil degranulation products (DGP) obtained from circulating neutrophils. Moreover, different interactions between neutrophils and platelets are described. Certain products released from neutrophils are critical for interactions between different immune cells to ensure adequate tissue repair. By acting directly and indirectly on host cells, these neutrophil-derived products can modulate the body’s inflammatory responses in various ways. The development of new formulations based on these products and their clinically proven success would give hope for significant progress in regenerative therapy in human and veterinary medicine.

Bioactive Antimicrobial Peptides as Therapeutic Agents for Infected Diabetic Foot Ulcers

Diabetic foot ulcer (DFU) is a devastating complication, affecting around 15% of diabetic patients and representing a leading cause of non-traumatic amputations. Notably, the risk of mixed bacterial–fungal infection is elevated and highly associated with wound necrosis and poor clinical outcomes. However, it is often underestimated in the literature. Therefore, polymicrobial infection control must be considered for effective management of DFU. It is noteworthy that antimicrobial resistance is constantly rising overtime, therefore increasing the need for new alternatives to antibiotics and antifungals. Antimicrobial peptides (AMPs) are endogenous peptides that are naturally abundant in several organisms, such as bacteria, amphibians and mammals, particularly in the skin. These molecules have shown broad-spectrum antimicrobial activity and some of them even have wound-healing activity, establishing themselves as ideal candidates for treating multi-kingdom infected wounds. Furthermore, the role of AMPs with antifungal activity in wound management is poorly described and deserves further investigation in association with antibacterial agents, such as antibiotics and AMPs with antibacterial activity, or alternatively the application of broad-spectrum antimicrobial agents that target both aerobic and anaerobic bacteria, as well as fungi. Accordingly, the aim of this review is to unravel the molecular mechanisms by which AMPs achieve their dual antimicrobial and wound-healing properties, and to discuss how these are currently being applied as promising therapies against polymicrobial-infected chronic wounds such as DFUs.

Skin Wound Healing: Normal Macrophage Function and Macrophage Dysfunction in Diabetic Wounds

Macrophages play a prominent role in wound healing. In the early stages, they promote inflammation and remove pathogens, wound debris, and cells that have apoptosed. Later in the repair process, they dampen inflammation and secrete factors that regulate the proliferation, differentiation, and migration of keratinocytes, fibroblasts, and endothelial cells, leading to neovascularisation and wound closure. The macrophages that coordinate this repair process are complex: they originate from different sources and have distinct phenotypes with diverse functions that act at various times in the repair process. Macrophages in individuals with diabetes are altered, displaying hyperresponsiveness to inflammatory stimulants and increased secretion of pro-inflammatory cytokines. They also have a reduced ability to phagocytose pathogens and efferocytose cells that have undergone apoptosis. This leads to a reduced capacity to remove pathogens and, as efferocytosis is a trigger for their phenotypic switch, it reduces the number of M2 reparative macrophages in the wound. This can lead to diabetic foot ulcers (DFUs) forming and contributes to their increased risk of not healing and becoming infected, and potentially, amputation. Understanding macrophage dysregulation in DFUs and how these cells might be altered, along with the associated inflammation, will ultimately allow for better therapies that might complement current treatment and increase DFU’s healing rates.

Immunomodulatory Properties of Host Defence Peptides in Skin Wound Healing

Cutaneous wound healing is a vital biological process that aids skin regeneration upon injury. Wound healing failure results from persistent inflammatory conditions observed in diabetes, or autoimmune diseases like psoriasis. Chronic wounds are incurable due to factors like poor oxygenation, aberrant function of peripheral sensory nervature, inadequate nutrients and blood tissue supply. The most significant hallmark of chronic wounds is heavily aberrant immune skin function. The immune response in humans relies on a large network of signalling molecules and their interactions. Research studies have reported on the dual role of host defence peptides (HDPs), which are also often called antimicrobial peptides (AMPs). Their duality reflects their potential for acting as antibacterial peptides, and as immunodulators that assist in modulating several biological signalling pathways related to processes such as wound healing, autoimmune disease, and others. HDPs may differentially control gene regulation and alter the behaviour of epithelial and immune cells, resulting in modulation of immune responses. In this review, we shed light on the understanding and most recent advances related to molecular mechanisms and immune modulatory features of host defence peptides in human skin wound healing. Understanding their functional role in skin immunity may further inspire topical treatments for chronic wounds.

Antimicrobial Peptides: A New Hope in Biomedical and Pharmaceutical Fields

Antibiotics are essential drugs used to treat pathogenic bacteria, but their prolonged use contributes to the development and spread of drug-resistant microorganisms. Antibiotic resistance is a serious challenge and has led to the need for new alternative molecules less prone to bacterial resistance. Antimicrobial peptides (AMPs) have aroused great interest as potential next-generation antibiotics, since they are bioactive small proteins, naturally produced by all living organisms, and representing the first line of defense against fungi, viruses and bacteria. AMPs are commonly classified according to their sources, which are represented by microorganisms, plants and animals, as well as to their secondary structure, their biosynthesis and their mechanism of action. They find application in different fields such as agriculture, food industry and medicine, on which we focused our attention in this review. Particularly, we examined AMP potential applicability in wound healing, skin infections and metabolic syndrome, considering their ability to act as potential Angiotensin-Converting Enzyme I and pancreatic lipase inhibitory peptides as well as antioxidant peptides. Moreover, we argued about the pharmacokinetic and pharmacodynamic approaches to develop new antibiotics, the drug development strategies and the formulation approaches which need to be taken into account in developing clinically suitable AMP applications.