Nanosphere-mediated co-delivery of VEGF-A and PDGF-B genes for accelerating diabetic foot ulcers healing in rats

Molecular immunological mechanisms of impaired wound healing in diabetic foot ulcers (DFU), current therapeutic strategies and future directions

Diabetic foot ulcer (DFU) is a foremost cause of amputation in diabetic patients. Consequences of DFU include infections, decline in limb function, hospitalization, amputation, and in severe cases, death. Immune cells including macrophages, regulatory T cells, fibroblasts and other damage repair cells work in sync for effective healing and in establishment of a healthy skin barrier post-injury. Immune dysregulation during the healing of wounds can result in wound chronicity. Hyperglycemic conditions in diabetic patients influence the pathophysiology of wounds by disrupting the immune system as well as promoting neuropathy and ischemic conditions, making them difficult to heal. Chronic wound microenvironment is characterized by increased expression of matrix metalloproteinases, reactive oxygen species as well as pro-inflammatory cytokines, resulting in persistent inflammation and delayed healing. Novel treatment modalities including growth factor therapies, nano formulations, microRNA based treatments and skin grafting approaches have significantly augmented treatment efficiency, demonstrating creditable efficacy in clinical practices. Advancements in local treatments as well as invasive methodologies, for instance formulated wound dressings, stem cell applications and immunomodulatory therapies have been successful in targeting the complex pathophysiology of chronic wounds. This review focuses on elucidating the intricacies of emerging physical and non-physical therapeutic interventions, delving into the realm of advanced wound care and comprehensively summarizing efficacy of evidence-based therapies for DFU currently available.

Healing the diabetic wound: Unlocking the secrets of genes and pathways

Diabetic wounds (DWs) are open sores that can occur anywhere on a diabetic patient's body. They are often complicated by infections, hypoxia, oxidative stress, hyperglycemia, and reduced growth factors and nucleic acids. The healing process involves four phases: homeostasis, inflammation, proliferation, and remodeling, regulated by various cellular and molecular events. Numerous genes and signaling pathways such as VEGF, TGF-β, NF-κB, PPAR-γ, MMPs, IGF, FGF, PDGF, EGF, NOX, TLR, JAK-STAT, PI3K-Akt, MAPK, ERK, JNK, p38, Wnt/β-catenin, Hedgehog, Notch, Hippo, FAK, Integrin, and Src pathways are involved in these events. These pathways and genes are often dysregulated in DWs leading to impaired healing. The present review sheds light on the pathogenesis, healing process, signaling pathways, and genes involved in DW. Further, various therapeutic strategies that target these pathways and genes via nanotechnology are also discussed. Additionally, clinical trials on DW related to gene therapy are also covered in the present review.

Evaluating a promising methylcellulose hydrogel for enhanced diabetic foot ulcer therapy through comprehensive preclinical studies

The present research focuses on formulating and evaluating hydrogels modified with crosslinking agents using methylcellulose to treat diabetic foot ulcers (DFU). Methylcellulose hydrogels are prepared and characterized for their crosslinking capacity through FTIR and degradation studies. The optimized hydrogel is further assessed for viscosity, gel strength, contact angle, in-vitro biodegradation, water-vapor transmission rate, anti-bacterial activity, and in-vivo efficacy. The results demonstrate that the developed hydrogel exhibits promising properties for DFU treatment, including increased wound healing percentage, improved ulcer morphology, reduced levels of proinflammatory cytokines, and enhanced tissue characteristics. These findings suggest that the novel hydrogel composition could serve as a viable alternative to existing dressings for DFU management.

Dehydrozingerone promotes healing of diabetic foot ulcers: a molecular insight

INTRODUCTION

One of the most common problems of diabetes are diabetic foot ulcers (DFUs). According to National Institute for Health, initial management of DFUs can decrease the complication of limb amputations and can improve the patient's quality of life. DFU treatment can be optimized with the help of multidisciplinary approach. Based on many studies, control of glucose levels in blood, antioxidant activity, reduction in cytokine levels, re-epithelialization, collagen formation, migration of fibroblasts are major phases involved in managing DFU. Dehydrozingerone (DHZ), has been known for its anti-inflammatory, antioxidant and wound healing properties.

METHODOLOGY

Three months high-fat diet and low dose of streptozotocin-induced type-II diabetic foot ulcer model was used to evaluate the effectiveness of dehydrozingerone. DHZ was given orally to rats for 15 days post wounding. TNF-α, IL-1β and antioxidant parameters like lipid peroxidation, glutathione reductase were estimated. Immunoblotting was done to investigate the effect of DHZ on the expression of ERK, JNK, HSP-27, P38, SIRT-1, NFκB, SMA, VEGF and MMP-9 in skin tissue. Histopathology was performed for analyzing DHZ effect on migration of fibroblasts, formation of epithelium, granulation tissue formation, angiogenesis and collagen formation.

RESULTS

DHZ decreased the levels of malondialdehyde, TNF-α, IL-1β and increased glutathione levels in wound tissue. Western blotting results suggested that DHZ activated ERK1/2/JNK/p38 signaling, increased expression of HSP-27, SIRT-1, VEGF, SMA thus facilitating the migration and proliferation of fibroblasts, angiogenesis and decreased inflammation. Masson Trichrome & histopathology showed an increase in collagen, epithelial and granulation tissue formation.

CONCLUSION

DHZ significantly accelerates the healing of diabetic foot ulcers in high fat diet fed plus low dose streptozotocin induced type-II diabetic Wistar rats.

Therapeutic role of growth factors in treating diabetic wound

Wounds in diabetic patients, especially diabetic foot ulcers, are more difficult to heal compared with normal wounds and can easily deteriorate, leading to amputation. Common treatments cannot heal diabetic wounds or control their many complications. Growth factors are found to play important roles in regulating complex diabetic wound healing. Different growth factors such as transforming growth factor beta 1, insulin-like growth factor, and vascular endothelial growth factor play different roles in diabetic wound healing. This implies that a therapeutic modality modulating different growth factors to suit wound healing can significantly improve the treatment of diabetic wounds. Further, some current treatments have been shown to promote the healing of diabetic wounds by modulating specific growth factors. The purpose of this study was to discuss the role played by each growth factor in therapeutic approaches so as to stimulate further therapeutic thinking.

PDGF and VEGF-releasing bi-layer wound dressing made of sodium tripolyphosphate crosslinked gelatin-sponge layer and a carrageenan nanofiber layer

The use of dressings is one of the most common methods for wound treatment. Since most single-layer dressings cannot mimic the hierarchical structure of the skin well, multi-layer dressings have been considered. In this study, a bilayer dressing was fabricated using a gelatin sponge layer cross-linked with sodium tripolyphosphate (Gel-STPP) and a layer of carrageenan nanofibers containing platelet-rich fibrin (Carr-PRF). Chemical interactions between the two layers were characterized by FTIR, and the microstructure was visualized by SEM. It was found that the presence of Carr-PRF nanofiber layer increased tensile strength by 12.96 % (from 0.216 ± 0.015 to 0.268 ± 0.036 MPa) and elastic modulus by 56.70 % (from 0.388 ± 0.072 to 0.608 ± 0.029 MPa) compared to Gel-STPP sponge. Gel-STPP/Carr-PRF wound dressing had a 45.76 ± 4.18 % degradability after 7 days of immersion in phosphate buffered saline (PBS). PRF-containing bilayer wound dressing was able to sustainably release growth factors over 7 days. The Carr-PRF nanofiber layer coated on Gel-STPP sponge was an ideal environment for adhesion and proliferation of L929 cells. Gel-STPP/Carr-PRF bilayer dressing outperformed the other tested samples in terms of angiogenic potential. Average wound closure was 94.21 ± 2.06 % in Gel-STPP/Carr-PRF dressing treated rats after 14 days, and based on the histopathological and immunohistochemical examinations, the Gel-STPP/Carr-PRF dressing group augmented full-thickness wound healing, keratin layer and skin appendages formation after 14 days.

Microenvironment-Based Diabetic Foot Ulcer Nanomedicine

Diabetic foot ulcers (DFU), one of the most serious complications of diabetes, are essentially chronic, nonhealing wounds caused by diabetic neuropathy, vascular disease, and bacterial infection. Given its pathogenesis, the DFU microenvironment is rather complicated and characterized by hyperglycemia, ischemia, hypoxia, hyperinflammation, and persistent infection. However, the current clinical therapies for DFU are dissatisfactory, which drives researchers to turn attention to advanced nanotechnology to address DFU therapeutic bottlenecks. In the last decade, a large number of multifunctional nanosystems based on the microenvironment of DFU have been developed with positive effects in DFU therapy, forming a novel concept of "DFU nanomedicine". However, a systematic overview of DFU nanomedicine is still unavailable in the literature. This review summarizes the microenvironmental characteristics of DFU, presents the main progress of wound healing, and summaries the state-of-the-art therapeutic strategies for DFU. Furthermore, the main challenges and future perspectives in this field are discussed and prospected, aiming to fuel and foster the development of DFU nanomedicines successfully.

A Comprehensive Review of the Application of Nanoparticles in Diabetic Wound Healing: Therapeutic Potential and Future Perspectives

Diabetic wounds are one of the most challenging public health issues of the 21st century due to their inadequate vascular supply, bacterial infections, high levels of oxidative stress, and abnormalities in antioxidant defenses, whereas there is no effective treatment for diabetic wounds. Due to the distinct properties of nanoparticles, such as their small particle size, elevated cellular uptake, low cytotoxicity, antibacterial activity, good biocompatibility, and biodegradability. The application of nanoparticles has been widely used in the treatment of diabetic wound healing due to their superior anti-inflammatory, antibacterial, and antioxidant activities. These nanoparticles can also be loaded with various agents, such as organic molecules (eg, exosomes, small molecule compounds, etc.), inorganic molecules (metals, nonmetals, etc.), or complexed with various biomaterials, such as smart hydrogels (HG), chitosan (CS), and hyaluronic acid (HA), to augment their therapeutic potential in diabetic wounds. This paper reviews the therapeutic potential and future perspective of nanoparticles in the treatment of diabetic wounds. Together, nanoparticles represent a promising strategy in the treatment of diabetic wound healing. The future direction may be to develop novel nanoparticles with multiple effects that not only act in wound healing at all stages of diabetes but also provide a stable physiological environment throughout the wound-healing process.

A novel matrix metalloproteinases-cleavable hydrogel loading deferoxamine accelerates diabetic wound healing

The hyperglycemia microenvironment of diabetic foot ulcer (DFU) led to impaired angiogenesis and delayed wound healing. An elevated matrix metalloproteinase (MMP) is one of the significant factors to delay healing. Herein, we designed a deferoxamine (DFO)-loaded MMP responsive hydrogel, thus promoting angiogenesis and accelerating wound healing by increasing the expression of hypoxia-inducible factor-1α (HIF-1α). Hyaluronic acid was modified with maleimide and grafted with MMP-cleavable peptides (HA-peptide). Then, HA-peptide was crosslinked with oxidized dextran (Dex-CHO) based on Schiff-base reaction. In vitro tests showed that the hydrogel had excellent swelling properties, degradation behavior, rheological characterization, and biocompatibility. Compared with an MMP-insensitive hydrogel, the MMP-cleavable hydrogel allowed for efficient release of DFO continuously within 24 h, which could address the problems of the extremely short half-life and neurotoxicity of DFO. In vivo experiments demonstrated that the hydrogel wound dressing facilitated faster wound epithelialization and accelerated angiogenesis in diabetic rats. Altogether, the DFO-loaded MMP-cleavable hydrogel may lead to a potential and novel treatment strategy of DFU.

Nano-Enabled Chronic Wound Healing Strategies: Burn and Diabetic Ulcer Wounds

The human skin serves as the body’s first line of defense against the environment. Diabetes mellitus (DM) and 2nd–4th degree burns, on the other hand, affect the skin’s protective barrier features. Burn wounds, hypermetabolic state, and hyperglycemia compromise the immune system leading to chronic wound healing. Unlike acute wound healing processes, chronic wounds are affected by reinfections which can lead to limb amputation or death. The conventional wound dressing techniques used to protect the wound and provide an optimal environment for repair have their limitations. Various nanomaterials have been produced that exhibit distinct features to tackle issues affecting wound repair mechanisms. This review discusses the emerging technologies that have been designed to improve wound care upon skin injury. To ensure rapid healing and possibly prevent scarring, different nanomaterials can be applied at different stages of healing (hemostasis, inflammation, proliferation, remodeling).

Gene therapy to enhance angiogenesis in chronic wounds

Skin injuries and chronic non-healing wounds are one of the major global burdens on the healthcare systems worldwide due to their difficult-to-treat nature, associated co-morbidities, and high health care costs. Angiogenesis has a pivotal role in the wound-healing process, which becomes impaired in many chronic non-healing wounds, leading to several healing disorders and complications. Therefore, induction or promotion of angiogenesis can be considered a promising approach for healing of chronic wounds. Gene therapy is one of the most promising upcoming strategies for the treatment of chronic wounds. It can be classified into three main approaches: gene augmentation, gene silencing, and gene editing. Despite the increasing number of encouraging results obtained using nucleic acids (NAs) as active pharmaceutical ingredients of gene therapy, efficient delivery of NAs to their site of action (cytoplasm or nucleus) remains a key challenge. Selection of the right therapeutic cargo and delivery methods is crucial for a favorable prognosis of the healing process. This article presents an overview of gene therapy and non-viral delivery methods for angiogenesis induction in chronic wounds.

Nucleic acid-based therapeutics for dermal wound healing

Non-healing wounds have long been the subject of scientific and clinical investigations. Despite breakthroughs in understanding the biology of delayed wound healing, only limited advances have been made in properly treating wounds. Recently, research into nucleic acids (NAs) such as small-interfering RNA (siRNA), microRNA (miRNA), plasmid DNA (pDNA), aptamers, and antisense oligonucleotides (ASOs) has resulted in the development of a latest therapeutic strategy for wound healing. In this regard, dendrimers, scaffolds, lipid nanoparticles, polymeric nanoparticles, hydrogels, and metal nanoparticles have all been explored as NA delivery techniques. However, the translational possibility of NA remains a substantial barrier. As a result, different NAs must be identified, and their distribution method must be optimized. This review explores the role of NA-based therapeutics in various stages of wound healing and provides an update on the most recent findings in the development of NA-based nanomedicine and biomaterials, which may offer the potential for the invention of novel therapies for this long-term condition. Further, the challenges and potential for miRNA-based techniques to be translated into clinical applications are also highlighted.

Endothelial Phospholipase Cγ2 Improves Outcomes of Diabetic Ischemic Limb Rescue Following VEGF Therapy

Therapeutic vascular endothelial growth factor (VEGF) replenishment has met with limited success for the management of critical limb-threatening ischemia. To improve outcomes of VEGF therapy, we applied single-cell RNA sequencing (scRNA-seq) technology to study the endothelial cells of the human diabetic skin. Single-cell suspensions were generated from the human skin followed by cDNA preparation using the Chromium Next GEM Single-cell 3' Kit v3.1. Using appropriate quality control measures, 36,487 cells were chosen for downstream analysis. scRNA-seq studies identified that although VEGF signaling was not significantly altered in diabetic versus nondiabetic skin, phospholipase Cγ2 (PLCγ2) was downregulated. The significance of PLCγ2 in VEGF-mediated increase in endothelial cell metabolism and function was assessed in cultured human microvascular endothelial cells. In these cells, VEGF enhanced mitochondrial function, as indicated by elevation in oxygen consumption rate and extracellular acidification rate. The VEGF-dependent increase in cell metabolism was blunted in response to PLCγ2 inhibition. Follow-up rescue studies therefore focused on understanding the significance of VEGF therapy in presence or absence of endothelial PLCγ2 in type 1 (streptozotocin-injected) and type 2 (db/db) diabetic ischemic tissue. Nonviral topical tissue nanotransfection technology (TNT) delivery of CDH5 promoter-driven PLCγ2 open reading frame promoted the rescue of hindlimb ischemia in diabetic mice. Improvement of blood flow was also associated with higher abundance of VWF+/CD31+ and VWF+/SMA+ immunohistochemical staining. TNT-based gene delivery was not associated with tissue edema, a commonly noted complication associated with proangiogenic gene therapies. Taken together, our study demonstrates that TNT-mediated delivery of endothelial PLCγ2, as part of combination gene therapy, is effective in diabetic ischemic limb rescue.

Regenerative Approaches for Chronic Wounds

Chronic skin wounds are commonly found in older individuals who have impaired circulation due to diabetes or are immobilized due to physical disability. Chronic wounds pose a severe burden to the health-care system and are likely to become increasingly prevalent in aging populations. Various treatment approaches exist to help the healing process, although the healed tissue does not generally recapitulate intact skin but rather forms a scar that has inferior mechanical properties and that lacks appendages such as hair or sweat glands. This article describes new experimental avenues for attempting to improve the regenerative response of skin using biophysical techniques as well as biochemical methods, in some cases by trying to harness the potential of stem cells, either endogenous to the host or provided exogenously, to regenerate the skin. These approaches primarily address the local wound environment and should likely be combined with other modalities to address regional and systemic disease, as well as social determinants of health. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

ROS-responsive nanoparticle-mediated delivery of CYP2J2 gene for therapeutic angiogenesis in severe hindlimb ischemia

With critical limb ischemia (CLI) being a multi-factorial disease, it is becoming evident that gene therapy with a multiple bio-functional growth factor could achieve better therapeutic outcomes. Cytochrome P450 epoxygenase-2J2 (CYP2J2) and its catalytic products epoxyeicosatrienoic acids (EETs) exhibit pleiotropic biological activities, including pro-angiogenic, anti-inflammatory and cardiovascular protective effects, which are considerably beneficial for reversing ischemia and restoring local blood flow in CLI. Here, we designed a nanoparticle-based pcDNA3.1-CYP2J2 plasmid DNA (pDNA) delivery system (nanoparticle/pDNA complex) composed of a novel three-arm star block copolymer (3S-PLGA-po-PEG), which was achieved by conjugating three-armed PLGA to PEG via the peroxalate ester bond. Considering the multiple bio-functions of CYP2J2-EETs and the sensitivity of the peroxalate ester bond to H₂O₂, this nanoparticle-based gene delivery system is expected to exhibit excellent pro-angiogenic effects while improving the high oxidative stress and inflammatory micro-environment in ischemic hindlimb. Our study reports the first application of CYP2J2 in the field of therapeutic angiogenesis for CLI treatment and our findings demonstrated good biocompatibility, stability and sustained release properties of the CYP2J2 nano-delivery system. In addition, this nanoparticle-based gene delivery system showed high transfection efficiency and efficient VEGF expression in vitro and in vivo. Intramuscular injection of nanoparticle/pDNA complexes into mice with hindlimb ischemia resulted in significant rapid blood flow recovery and improved muscle repair compared to mice treated with naked pDNA. In summary, 3S-PLGA-po-PEG/CYP2J2-pDNA complexes have tremendous potential and provide a practical strategy for the treatment of limb ischemia. Moreover, 3S-PLGA-po-PEG nanoparticles might be useful as a potential non-viral carrier for other gene delivery applications.

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Cytochrome P450 epoxygenase-2J2 (CYP2J2) was first applied in the field of therapeutic angiogenesis for critical limb ischemia treatment.

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The ROS-responsive three-arm star block copolymer (3S-PLGA-po-PEG) was synthesized with peroxalate ester as H₂O₂-responsive linkages through the esterification reaction of oxalyl chloride and hydroxyl group.

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The CYP2J2 nano-delivery system achieved high transfection efficiency and significant therapeutic angiogenesis effect.

Angiogenic efficacy of ASC spheroids filtrated on porous nanosheets for the treatment of a diabetic skin ulcer

Stem cell transplantation is expected to be an effective treatment for intractable skin ulcers by promoting angiogenesis; however, it is challenging to quickly realize a sufficient bloodstream for the ulcers. For this treatment, sheet-like materials with monolayer cells such as cell sheets have been investigated. However, they have a limitation of cell number that can be transplanted at one time due to the two-dimensional, monolayer cell structure, and sufficient secretion of growth factors cannot be expected. In this regard, cellular aggregates, such as spheroids, can reproduce three-dimensional cell-cell interactions that cause biological functions of living tissues more representative than monolayer cells, which is important to achieving efficient secretion of growth factors. In this study, we focused on free-standing porous polymer ultrathin films ("porous nanosheets") comprising poly(d,l-lactic acid) (PDLLA) and succeeded in developing a spheroid-covered nanosheet, on which more than 1000 spheroids from adipose-tissue derived stem cells (ASCs) were loaded. The porous structure with an average pore diameter of 4 μm allowed for facile filtration and carrying spheroids on the nanosheet, as well as sufficient oxygen and nutrients inflow to the cells. The spheroid-covered nanosheet achieved homogeneous transference of spheroids to a whole skin defect in diabetic model mice. Given the continuous release of vascular endothelial growth factor (VEGF) from the spheroids, the transplanted spheroids promoted healing with more accelerated angiogenesis than a nanosheet with a monolayer of cells. The spheroid-covered nanosheet may be a new regenerative material for promoting intractable skin ulcer healing.

Nanotechnology-based therapeutic applications: in vitro and in vivo clinical studies for diabetic wound healing

Diabetic wounds often indicate chronic complications that are difficult to treat. Unfortunately, existing conventional treatment modalities often cause unpremeditated side effects, given the need to develop alternative therapeutic phenotypes that are safe or have minimal side effects and risks. Nanotechnology-based platforms, including nanotherapeutics, nanoparticles (NPs), nanofibers, nanohydrogels, and nanoscaffolds, have garnered attention for their groundbreaking potential to decipher the biological environment and offer personalized treatment methods for wound healing. These nanotechnology-based platforms can successfully overcome the impediments posed by drug toxicity, existing treatment modalities, and the physiology and complexity of the wound sites. Furthermore, studies have shown that they play an essential role in influencing angiogenesis, collagen production, and extracellular matrix (ECM) synthesis, which are integral in skin repair mechanisms. In this review, we emphasized the importance of various nanotechnology-based platforms for healing diabetic wounds and report on the innovative preclinical and clinical outcomes of different nanotechnology-based platforms. This review also outlined the limitations of existing conventional treatment modalities and summarized the physiology of acute and chronic diabetic wounds.

Harnessing Multifaceted Next-Generation Technologies for Improved Skin Wound Healing

Dysregulation of sequential and synchronized events of skin regeneration often results in the impairment of chronic wounds. Conventional wound dressings fail to trigger the normal healing mechanism owing to the pathophysiological conditions. Tissue engineering approaches that deal with the fabrication of dressings using various biomaterials, growth factors, and stem cells have shown accelerated healing outcomes. However, most of these technologies are associated with difficulties in scalability and cost-effectiveness of the products. In this review, we survey the latest developments in wound healing strategies that have recently emerged through the multidisciplinary approaches of bioengineering, nanotechnology, 3D bioprinting, and similar cutting-edge technologies to overcome the limitations of conventional therapies. We also focus on the potential of wearable technology that supports complete monitoring of the changes occurring in the wound microenvironment. In addition, we review the role of advanced devices that can precisely enable the delivery of nanotherapeutics, oligonucleotides, and external stimuli in a controlled manner. These technological advancements offer the opportunity to actively influence the regeneration process to benefit the treatment regime further. Finally, the clinical relevance, trajectory, and prospects of this field have been discussed in brief that highlights their potential in providing a beneficial wound care solution at an affordable cost.

Therapeutic approaches targeting molecular signaling pathways common to diabetes, lung diseases and cancer

Diabetes mellitus (DM), is the most common metabolic disease and is characterized by sustained hyperglycemia. Accumulating evidences supports a strong association between DM and numerous lung diseases including chronic obstructive pulmonary disease (COPD), fibrosis, and lung cancer (LC). The global incidence of DM-associated lung disorders is rising and several ongoing studies, including clinical trials, aim to elucidate the molecular mechanisms linking DM with lung disorders, in particular LC. Several potential mechanisms, including hyperglycemia, hyperinsulinemia, glycation, inflammation, and hypoxia, are cited as plausible links between DM and LC. In addition, studies also propose a connection between the use of anti-diabetic medications and reduction in the incidence of LC. However, the exact cause for DM associated lung diseases especially LC is not clear and is an area under intense investigation. Herein, we review the biological links reported between DM and lung disorders with an emphasis on LC. Furthermore, we report common signaling pathways (eg: TGF-β, IL-6, HIF-1, PDGF) and miRNAs that are dysregulated in DM and LC and serve as molecular targets for therapy. Finally, we propose a nanomedicine based approach for delivering therapeutics (eg: IL-24 plasmid DNA, HuR siRNA) to disrupt signaling pathways common to DM and LC and thus potentially treat DM-associated LC. Finally, we conclude that the effective modulation of commonly regulated signaling pathways would help design novel therapeutic protocols for treating DM patients diagnosed with LC.

Tannic acid-inspired, self-healing, and dual stimuli responsive dynamic hydrogel with potent antibacterial and anti-oxidative properties

Due to their intrinsic injectable and self-healing characteristics, dynamic hydrogels, based on dynamic covalent bonds, have gained a great attention. In this study, a novel dynamic hydrogel based on the boronic ester dynamic covalent bond is facilely developed using phenylboronic acid-modified hyaluronic acid (HA-PBA) and plant-derived polyphenol-tannic acid (TA). The dynamic hydrogel gelated quickly under mild conditions and had favorable viscoelastic properties with good self-healing and shear-thinning capabilities. Moreover, the simultaneous utilization of TA as a reductant for the green synthesis of silver nanoparticles (AgNP) inspired the preparation of a TA-reduced AgNP hybrid dynamic hydrogel with potent and broad-spectrum antibacterial activities. The dynamic hydrogels could also be applied for pH- and reactive oxygen species (ROS)-responsive release of loaded protein molecules without showing evident cytotoxicity and hemolysis in vitro. In addition, the dynamic hydrogels showed the anti-oxidative properties of high free radical and ROS scavenging capacity, which was verified by the DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) free radical assay and ROS fluorescence staining. Overall, this novel class of cytocompatible, self-healing, dual stimuli responsive, antibacterial, anti-oxidative, and injectable hydrogels could be promising as a wound dressing for chronic wound healing.

Approaches to Modulate the Chronic Wound Environment Using Localized Nucleic Acid Delivery

Significance: Nonhealing wounds have been the subject of decades of basic and clinical research. Despite new knowledge about the biology of impaired wound healing, little progress has been made in treating chronic wounds, leaving patients with few therapeutic options. Diabetic ulcers are a particularly common form of nonhealing wound. Recent Advances: Recently, investigation of therapeutic nucleic acids (TNAs), including plasmid DNA, small interfering RNA, microRNA mimics, anti-microRNA oligonucleotides, messenger RNA, and antisense oligonucleotides, has created a new treatment strategy for chronic wounds. TNAs can modulate the wound toward a prohealing environment by targeting gene pathways associated with inflammation, proteases, cell motility, angiogenesis, epithelialization, and oxidative stress. A variety of delivery systems have been investigated for TNAs, including dendrimers, lipid nanoparticles (NPs), polymeric micelles, polyplexes, metal NPs, and hydrogels. This review summarizes recent developments in TNA delivery for therapeutic targets associated with chronic wounds, with an emphasis on diabetic ulcers. Critical Issues: Translational potential of TNAs remains a key challenge; we highlight some drug delivery approaches for TNAs that may hold promise. We also describe current commercial efforts to locally deliver nucleic acids to modulate the wound environment. Future Directions: Localized nucleic acid delivery holds promise for the treatment of nonhealing chronic wounds. Future efforts to improve targeting of these nucleic acid therapies in the wound with both spatial and temporal control through drug delivery systems will be crucial to successful clinical translation.

Recent Advances and Challenges in Gene Delivery Mediated by Polyester-Based Nanoparticles

Gene therapy is a promising approach for the treatment of several diseases, such as chronic or viral infections, inherited disorders, and cancer. The cellular internalization of exogenous nucleic acids (NA) requires efficient delivery vehicles to overcome their inherent pharmacokinetic drawbacks, e.g. electrostatic repulsions, enzymatic degradation, limited cellular uptake, fast clearance, etc. Nanotechnological advancements have enabled the use of polymer-based nanostructured biomaterials as safe and effective gene delivery systems, in addition to viral vector delivery methods. Among the plethora of polymeric nanoparticles (NPs), this review will provide a comprehensive and in-depth summary of the polyester-based nanovehicles, including poly(lactic-co-glycolic acid) (PLGA) and polylactic acid (PLA) NPs, used to deliver a variety of foreign NA, e.g. short interfering RNA (siRNA), messenger RNA (mRNA), and plasmid DNA (pDNA). The article will review the versatility of polyester-based nanocarriers including their recent application in the delivery of the clustered, regularly-interspaced, short palindromic repeats/Cas (CRISPR/Cas) genome editing system for treating gene-related diseases. The remaining challenges and future trend of the targeted delivery of this revolutionary genome-editing system will be discussed. Special attention will be given to the pivotal role of nanotechnology in tackling emerging infections such as coronavirus disease 2019 (COVID-19): ground-breaking mRNA vaccines delivered by NPs are currently used worldwide to fight the pandemic, pushing the boundaries of gene therapy.

Antimicrobial Peptides: The Promising Therapeutics for Cutaneous Wound Healing

Chronic wound infections have caused an increasing number of deaths and economic burden, which necessitates wound treatment options. Hitherto, the development of functional wound dressings has achieved reasonable progress. Antibacterial agents, growth factors, and miRNAs are incorporated in different wound dressings to treat various types of wounds. As an effective antimicrobial agent and emerging wound healing therapeutic, antimicrobial peptides (AMPs) have attracted significant attention. The present study focuses on the application of AMPs in wound healing and discusses the types, properties and formulation strategies of AMPs used for wound healing. In addition, the clinical trial and the current status of studies on "antimicrobial peptides and wound healing" are elaborated through bibliometrics. Also, the challenges and opportunities for further development and utilization of AMP formulations in wound healing are discussed.

Limited Treatment Options for Diabetic Wounds: Barriers to Clinical Translation Despite Therapeutic Success in Murine Models

Significance: Millions of people worldwide suffer from diabetes mellitus and its complications, including chronic diabetic wounds. To date, there are few widely successful clinical therapies specific to diabetic wounds beyond general wound care, despite the vast number of scientific discoveries in the pathogenesis of defective healing in diabetes. Recent Advances: In recent years, murine animal models of diabetes have enabled the investigation of many possible therapeutics for diabetic wound care. These include specific cell types, growth factors, cytokines, peptides, small molecules, plant extracts, microRNAs, extracellular vesicles, novel wound dressings, mechanical interventions, bioengineered materials, and more. Critical Issues: Despite many research discoveries, few have been translated from their success in murine models to clinical use in humans. This massive gap between bench discovery and bedside application begs the simple and critical question: what is still missing? The complexity and multiplicity of the diabetic wound makes it an immensely challenging therapeutic target, and this lopsided progress highlights the need for new methods to overcome the bench-to-bedside barrier. How can laboratory discoveries in animal models be effectively translated to novel clinical therapies for human patients? Future Directions: As research continues to decipher deficient healing in diabetes, new approaches and considerations are required to ensure that these discoveries can become translational, clinically usable therapies. Clinical progress requires the development of new, more accurate models of the human disease state, multifaceted investigations that address multiple critical components in wound repair, and more innovative research strategies that harness both the existing knowledge and the potential of new advances across disciplines.

Immunomodulatory biomaterials and their application in therapies for chronic inflammation-related diseases

The degree of tissue injuries such as the level of scarring or organ dysfunction, and the immune response against them primarily determine the outcome and speed of healing process. The successful regeneration of functional tissues requires proper modulation of inflammation-producing immune cells and bioactive factors existing in the damaged microenvironment. In the tissue repair and regeneration processes, different types of biomaterials are implanted either alone or by combined with other bioactive factors, which will interact with the immune systems including immune cells, cytokines and chemokines etc. to achieve different results highly depending on this interplay. In this review article, the influences of different types of biomaterials such as nanoparticles, hydrogels and scaffolds on the immune cells and the modification of immune-responsive factors such as reactive oxygen species (ROS), cytokines, chemokines, enzymes, and metalloproteinases in tissue microenvironment are summarized. In addition, the recent advances of immune-responsive biomaterials in therapy of inflammation-associated diseases such as myocardial infarction, spinal cord injury, osteoarthritis, inflammatory bowel disease and diabetic ulcer are discussed.

3D scaffolds in the treatment of diabetic foot ulcers: New trends vs conventional approaches

Diabetic foot ulcer (DFU) is a serious complication of diabetes mellitus, affecting roughly 25% of diabetic patients and resulting in lower limb amputation in over 70% of known cases. In addition to the devastating physiological consequences of DFU and its impact on patient quality of life, DFU has significant clinical and economic implications. Various traditional therapies are implemented to effectively treat DFU. However, emerging technologies such as bioprinting and electrospinning, present an exciting opportunity to improve current treatment strategies through the development of 3D scaffolds, by overcoming the limitations of current wound healing strategies. This review provides a summary on (i) current prevention and treatment strategies available for DFU; (ii) methods of fabrication of 3D scaffolds relevant for this condition; (iii) suitable materials and commonly used molecules for the treatment of DFU; and (iv) future directions offered by emerging technologies.

Influence of Recombinant Codon-Optimized Plasmid DNA Encoding VEGF and FGF2 on Co-Induction of Angiogenesis

Simple Summary

Over the past few decades, several methods have been proposed to stimulate skin wound healing. The most promising of these are gene therapy and stem cell therapy. Our present experiments have combined several approaches utilizing human umbilical cord blood mononuclear cells using cell therapy, and direct gene therapy using genetic constructs to accelerate complete healing of skin wounds in rats. Studies have shown that the transplantation of transfected cells stopped proliferative processes in regenerating wounds earlier than the transplantation of untransfected cells. The use of direct gene therapy using the VEGF and FGF2 genes stimulates the revascularization of the rat cutaneous wound.

Abstract

Several methods for the stimulation of skin wound repair have been proposed over the last few decades. The most promising among them are gene and stem cell therapy. Our present experiments combined several approaches via the application of human umbilical cord blood mononuclear cells (hUCB-MC) that were transfected with pBud-VEGF165-FGF2 plasmid (gene-cell therapy) and direct gene therapy using pBud-VEGF165-FGF2 plasmid to enhance healing of full thickness skin wounds in rats. The dual expression cassette plasmid pBud-VEGF165-FGF2 encodes both VEGF and FGF2 therapeutic genes, expressing pro-angiogenic growth factors. Our results showed that, with two weeks post-transplantation, some transplanted cells still retained expression of the stem cell and hematopoietic markers C-kit and CD34. Other transplanted cells were found among keratinocytes, hair follicle cells, endothelial cells, and in the derma. PCNA expression studies revealed that transplantation of transfected cells terminated proliferative processes in regenerating wounds earlier than transplantation of untransfected cells. In the direct gene therapy group, four days post-operatively, the processes of flap revascularization, while using Easy LDI Microcirculation Camera, was higher than in control wounded skin. We concluded that hUCB-MC can be used for the treatment of skin wounds and transfection these cells with VEGF and FGF2 genes enhances their regenerative abilities. We also concluded that the application of pBud-VEGF165-FGF2 plasmids is efficient for the direct gene therapy of skin wounds by stimulation of wound revascularization.

Sesamol-Loaded PLGA Nanosuspension for Accelerating Wound Healing in Diabetic Foot Ulcer in Rats

Background

Diabetic foot ulcer is an intractable complication of diabetes, characterized by the disturbed inflammatory and proliferative phases of wound healing. Sesamol, a phenolic compound, has been known for its powerful antioxidant, anti-inflammatory, anti-hyperglycaemic and wound healing properties. The aim of the present study was to develop a sesamol nano formulation and to study its effect on the various phases of the wound healing process in diabetic foot condition.

Methods

Sesamol-PLGA (SM-PLGA) nanosuspension was developed  using nanoprecipitation method. TEM, in vitro drug release assay and in vivo pharmacokinetic studies were performed for the optimised formulation. Diabetic foot ulcer (DFU) in high fat diet (HFD)-fed streptozotocin-induced type-II diabetic animal model was used to assess the SM-PLGA nanosuspension efficacy. SM-PLGA nanosuspension was administered by oral route. TNF-α levels were estimated using ELISA and Western blot analysis was performed to assess the effect on the expression of HSP-27, ERK, PDGF-B and VEGF in wound tissue. Wound re-epithelization, fibroblast migration, collagen deposition and inflammatory cell infiltration were assessed by H&E and Masson’s trichrome staining. Effect on angiogenesis was assessed by CD-31 IHC staining in wound sections.

Results

The optimized SM-PLGA nanosuspension had an average particle size of <300 nm, PDI<0.200 with spherical shaped particles. Approximately 80% of the drug was released over a period of 60 h in in vitro assay. Half-life of the formulation was found to be 13.947 ± 0.596 h. SM-PLGA nanosuspension treatment decreased TNF-α levels in wound tissue and accelerated the collagen deposition. Whereas, HSP-27, ERK, PDGF-B and VEGF expression increased and improved new blood vessels’ development. Rapid re-epithelization, fibroblast migration, collagen deposition and reduced inflammatory cell infiltration at the wound site were also observed.

Conclusion

Results indicate that sesamol-PLGA nanosuspension significantly promotes the acceleration of wound healing in diabetic foot ulcers by restoring the altered wound healing process in diabetic condition.

Long noncoding RNA H19 acts as a miR-29b sponge to promote wound healing in diabetic foot ulcer

Aberrant expression of long noncoding RNA (lncRNA) H19 and microRNA (miR)-29b has been implicated in the complications of diabetes mellitus (DM). As a common and important complication of DM, diabetic foot ulcer (DFU) is characterized by high incidence and poor prognosis. Herein, we explored the role of lncRNA H19 in wound healing of DFU. Differentially expressed DM-related lncRNAs were initially screened by microarray data analysis. DFU models were then induced in DM mouse models. The functional role and interaction of lncRNA H19, miR-29b and FBN1 in DFU were subsequently determined by examining the proliferation, migration, and apoptosis of fibroblasts after silencing H19, inhibiting or overexpressing miR-29b and FBN1. According to microarray-based analysis, lncRNA H19 was upregulated in DM. In the ulcerative edge tissues of DFU, high expression of lncRNA H19 and FBN1 and low expression of miR-29b were observed. FBN1 was identified to be a target gene of miR-29b. LncRNA H19 could competitively bind to miR-29b, and then, inhibited its expression, which consequently upregulating FBN1. Silencing of lncRNA H19 led to inhibited proliferation, migration, and enhanced apoptosis of fibroblasts, accompanied by downregulated FBN1 but upregulated miR-29b, which diminished the expression of TGF-β1, Smad3, FN, and Col-1 and reduced extracellular matrix accumulation. Altogether, upregulation of lncRNA H19 can elevate the expression of FBN1 through competitively binding to miR-29b, which enhances the proliferation, migration, and inhibits apoptosis of fibroblasts, thus facilitating the wound healing of DFU.

Nanotechnology-driven advances in the treatment of diabetic wounds

Diabetic foot ulcers (DFUs) are chronic severe complications of diabetes disease and remain a worldwide clinical challenge with social and economic consequences. Diabetic wounds can cause infection, amputation of lower extremities, and even death. Several factors including impaired angiogenesis, vascular insufficiency, and bacterial infections result in a delayed process of wound healing in diabetic patients. Treatment of wound infections using traditional antibiotics has become a critical status. Thus, finding new therapeutic strategies to manage diabetic wounds is urgently needed. Nanotechnology has emerged as an efficient approach for this purpose. This review aimed to summarize recent advances using nanotechnology for the treatment of diabetic wounds.

Topical GDF11 accelerates skin wound healing in both type 1 and 2 diabetic mouse models

This study aimed to investigate the role of truncated growth differentiation factor 11 (GDF11), in which the recognition site of Furin from wild-type GDF11 was deleted to enhance the cellular stability, in skin wound healing in the setting of diabetes mellitus (DM) and the underlying mechanisms. Our study found that both truncated and natural GDF11s effectively accelerated wound healing processes in both T1DM and T2DM mice with a potency compatible to PDGF, bFGF, and EGF, but being much higher than GDF8. At the cellular level, GDF11 stimulated the proliferation and suppressed HG-induced apoptosis of HSFs. Further study revealed that GDF11 activated the YAP-Smad2/3-CTGF fibrotic signaling pathway by reversing HG-induced upregulation of phosphorylated form of YAP (p-YAP), increases p-Smad2/3 levels, and restoring HG-induced repression of CTGF expression by GDF11. Overall, the study shows that both natural and truncated GDF11s promote the healing process of skin wound in mice of both T1DM and T2DM partly via stimulating dermal fibrosis via the YAP-Smad2/3-CTGF pathway, suggesting it a potential agent for treating skin wound in diabetic population.

Enhanced wound healing via collagen-turnover-driven transfer of PDGF-BB gene in a murine wound model

Wound healing is a complex biological process that requires coordinated cell proliferation, migration, and extracellular matrix production/remodeling, all of which are inhibited/delayed in chronic wounds. In this study, a formulation was developed that marries a fibrin-based, provisional-like matrix with collagen mimetic peptide (CMP)/PDGF gene-modified collagens, leading to the formation of robust gels that supported temporally controlled PDGF expression and facile application within the wound bed. Analysis employing in vitro co-gel scaffolds confirmed sustained and temporally controlled gene release based on matrix metalloproteinase (MMP) activity, with ~30% higher PDGF expression in MMP producing fibroblasts as-compared with non-MMP-expressing cells. The integration of fibrin with the gene-modified collagens resulted in co-gels that strongly supported both fibroblast cell recruitment/invasion as well as multiple aspects of the longer-term healing process. The excisional wound healing studies in mice established faster wound closure using CMP-modified PDGF polyplex-loaded co-gels, which exhibited up to 24% more wound closure (achieved with ~2 orders of magnitude lower growth factor dosing) after 9 days as compared to PDGF-loaded co-gels, and 19% more wound closure after 9 days as compared to CMP-free polyplex loaded co-gels. Moreover, minimal scar formation as well as improved collagen production, myofibroblast activity, and collagen orientation was observed following CMP-modified PDGF polyplex-loaded co-gel application on wounds. Taken together, the combined properties of the co-gels, including their stability and capacity to control both cell recruitment and cell phenotype within the murine wound bed, strongly supports the potential of the co-gel scaffolds for improved treatment of chronic non-healing wounds.

Advances in surgical applications of growth factors for wound healing

Growth factors have recently gained clinical importance for wound management. Application of recombinant growth factors has been shown to mimic cell migration, proliferation, and differentiation in vivo, allowing for external modulation of the healing process. Perioperative drug delivery systems can enhance the biological activity of these growth factors, which have a very short in vivo half-life after topical administration. Although the basic mechanisms of these growth factors are well understood, most have yet to demonstrate a significant impact in animal studies or small-sized clinical trials. In this review, we emphasized currently approved growth factor therapies, including a sustained release system for growth factors, emerging therapies, and future research possibilities combined with surgical procedures. Approaches seeking to understand wound healing at a systemic level are currently ongoing. However, further research and consideration in surgery will be needed to provide definitive confirmation of the efficacy of growth factor therapies for intractable wounds.