Wound Hypoxia Research Articles

Enzyme-Like Photocatalytic Octahedral Rh/Ag2MoO4 Accelerates Diabetic Wound Healing by Photo-Eradication of Pathogen and Relieving Wound Hypoxia.

The harsh environment of diabetic wounds, including bacterial infection and wound hypoxia, is not conducive to wound healing. Herein, an enzyme-like photocatalytic octahedral Rh/Ag2MoO4 is developed to manage diabetic-infected wounds. The introduction of Rh nanoparticles with catalase-like catalytic activity can enhance the photothermal conversion and photocatalytic performance of Rh/Ag2MoO4 by improving near-infrared absorbance and promoting the separation of electron-hole pairs, respectively. Rh/Ag2MoO4 can effectively eliminate pathogens through a combination of photothermal and photocatalytic antibacterial therapy. After bacteria inactivation, Rh/Ag2MoO4 can catalyze hydrogen peroxide to produce oxygen to alleviate the hypoxic environment of diabetic wounds. The in vivo treatment effect demonstrated the excellent therapeutic performance of Rh/Ag2MoO4 on diabetic infected wounds by removing infectious pathogens and relieving oxygen deficiency, confirming the potential application of Rh/Ag2MoO4 in the treatment of diabetic infected wounds.

Exosome-coated oxygen nanobubble-laden hydrogel augments intracellular delivery of exosomes for enhanced wound healing

Wound healing is an obvious clinical concern that can be hindered by inadequate angiogenesis, inflammation, and chronic hypoxia. While exosomes derived from adipose tissue-derived stem cells have shown promise in accelerating healing by carrying therapeutic growth factors and microRNAs, intracellular cargo delivery is compromised in hypoxic tissues due to activated hypoxia-induced endocytic recycling. To address this challenge, we have developed a strategy to coat oxygen nanobubbles with exosomes and incorporate them into a polyvinyl alcohol/gelatin hybrid hydrogel. This approach not only alleviates wound hypoxia but also offers an efficient means of delivering exosome-coated nanoparticles in hypoxic conditions. The self-healing properties of the hydrogel, along with its component, gelatin, aids in hemostasis, while its crosslinking bonds facilitate hydrogen peroxide decomposition, to ameliorate wound inflammation. Here, we show the potential of this multifunctional hydrogel for enhanced healing, promoting angiogenesis, facilitating exosome delivery, mitigating hypoxia, and inhibiting inflammation in a male rat full-thickness wound model.

Lipoic acid/trometamol assembled hydrogel as injectable bandage for hypoxic wound healing at high altitude

To avoid chronic wound formation caused by hypoxia and cold in high-altitude areas, developing an injectable, strongly adhesive hydrogel bandage with controllable oxygen generation and inflammation regulation functions is of great value. Poly(lipoic acid) (PLA)-based adhesives have been well-developed from polymerization of α-Lipoic acid (LA), showing attractive performances including simple preparation, strong adhesion, anti-inflammatory. However, injection of PLA-based adhesives has not been well-practiced because of its high viscosity and strong adhesion. Herein, LA and trometamol are firstly found to rapidly gel into a supramolecular hydrogel within 5 min at room temperature, exhibiting well-performed injectability. Further presence of Ce3+ significantly accelerates this gelation within 2 min. Meanwhile, dopamine (DA) and g-C3N4 nanosheet synergistically endow the injectable hydrogel with photothermal function, which can convert near-infrared-light (NIR) into heat, triggering LA polymerization and achieving post-injection enhancement. In terms of bandage performance after molding, the introduction of Ce3+, DA, and g-C3N4 contributes to the improvement of mechanical and adhesion properties. The injectable hydrogel bandage not only possesses highly tough and adhesive features, but also produces oxygen under NIR irradiation, effectively alleviating wound hypoxia, creating anti-inflammatory microenvironment, and significantly promoting healing of incision in a low-pressure oxygen environment.

A Comparative Analysis of HBOT and L-HBOT: An Innovative Possibility to Enhance HBOT?

Oxygen is a vital component of wound healing. When trauma occurs, causing a wound, it is difficult to get oxygen to the wound site because of the damage that is present. Hyperbaric oxygen chamber therapy (HBOT) is employed to combat hypoxia in wounds by having the patient inhale high concentrations of oxygen at elevated atmospheric pressures, accelerating the rate at which oxygen dissolves into the bloodstream at a faster rate. HBOT has been used to treat a variety of conditions like diabetic foot ulcers, Crohn’s disease, and chronic wounds. Yet, the limited body of literature and the risk of complications have limited the application of HBOT. Medical professionals have proven the significance of oxygen on wound healing from stimulating most of the vital functions to initiating the production of certain genes, oxygen is the keystone for successful complete wound healing. On the other hand, the risk of oxygen toxicity is one of the main contraindications of HBOT. Contrary to common knowledge, recent studies have shown that HBOT administered at a lower atmospheric pressure with a lower oxygen concentration can decrease this risk significantly. Low-pressure hyperbaric oxygen therapy (L-HBOT) may still be as effective as traditional high-pressure hyperbaric oxygen therapy (H-HBOT) without the unpredictable complications that medical professionals are unsure of. In all, this review aims to analyze recent studies to provide a clear comparison between these two variations of HBOT.

Conjugated Polymer Composite Nanoparticles Augmenting Photosynthesis-Based Light-Triggered Hydrogel Promotes Chronic Wound Healing.

Diabetic chronic wounds are characterized by local hypoxia, impaired angiogenesis, and bacterial infection. In situ, self-supply of dissolved oxygen combined with the elimination of bacteria is urgent and challenging for chronic nonhealing wound treatment. Herein, an oxygen-generating system named HA-L-NB/PFE@cp involving biological photosynthetic chloroplasts (cp)/conjugated polymer composite nanoparticles (PFE-1-NPs@cp) and light-triggered hyaluronic acid-based (HA-L-NB) hydrogel for promoting diabetic wound healing is introduced. Briefly, conjugated polymer nanoparticles (PFE-1-NPs) possess unique light harvesting ability, which accelerates the electron transport rates in photosystem II (PS II) by energy transfer, elevating photosynthesis beyond natural chloroplasts. The enhanced release of oxygen can greatly relieve hypoxia, promote cell migration, and favor antibacterial photodynamic therapy. Additionally, the injectable hydrogel precursors are employed as a carrier to deliver PFE-1-NPs@cp into the wound. Under light irradiation, they quickly form a gel by S-nitrosylation coupling reaction and in situ anchor on tissues through amine-aldehyde condensation. Both in vitro and in vivo assays demonstrate that the oxygen-generating system can simultaneously relieve wound hypoxia, eliminate bacteria, and promote cell migration, leading to the acceleration of wound healing. This study provides a facile approach to develop an enhanced oxygen self-sufficient system for promoting hypoxic tissue, especially diabetic wound healing.

A Programmable Oxygenation Device Facilitates Oxygen Generation and Replenishment to Promote Wound Healing.

Inadequate oxygenation is one of the chief culprits for delayed wound healing. However, current oxygen therapies, such as hyperbaric oxygen therapy and topical oxygen therapy, face hurdles in providing sustained and long-term oxygenation to reverse wound hypoxia. Furthermore, their efficacy in rejuvenating wound injury is restricted by limited penetration of oxygen in the wound bed. Herein, this study proposes a programmable and portable oxygenation device (named GUFO oxydevice) by ingeniously integrating i) a controllable oxygen generation and unidirectional transmission system (COGT-UTS), and ii) a supramolecular assembled perfluorinated hyperbranched polymer/gelatin (GUF) hydrogel in which the perfluorinated hyperbranched polymer (FHBP) acts as an oxygen reservoir to ensure sustained and convenient oxygen replenishment and thus directly regulate the hypoxic wound microenvironment. Accelerating the wound healing process by GUFO oxydeviceis achieved in both a diabetic rat and an acute porcine wound model without any secondary tissue damages. The present study demonstrates that the GUFO oxydevice holds promise as a practically feasible candidate for wound treatment.

Functional molecule-mediated assembled copper nanozymes for diabetic wound healing

BackgroundThe complex hyperglycemic, hypoxic, and reactive oxygen species microenvironment of diabetic wound leads to vascular defects and bacterial growth and current treatment options are relatively limited by their poor efficacy.ResultsHerein, a functional molecule-mediated copper ions co-assembled strategy was constructed for collaborative treatment of diabetic wounds. Firstly, a functional small molecule 2,5-dimercaptoterephthalic acid (DCA) which has symmetrical carboxyl and sulfhydryl structure, was selected for the first time to assisted co-assembly of copper ions to produce multifunctional nanozymes (Cu-DCA NZs). Secondly, the Cu-DCA NZs have excellent multicatalytic activity, and photothermal response under 808 nm irradiation. In vitro and in vivo experiments showed that it not only could efficiently inhibit bacterial growth though photothermal therapy, but also could catalyze the conversion of intracellular hydrogen peroxide to oxygen which relieves wound hypoxia and improving inflammatory accumulation. More importantly, the slow release of copper ions could accelerate cellular proliferation, migration and angiogenesis, synergistically promote the healing of diabetic wound furtherly.ConclusionsThe above results indicate that this multifunctional nanozymes Cu-DCA NZs may be a potential nanotherapeutic strategy for diabetic wound healing.

Pharmacological Ischemic Conditioning with Roxadustat Does Not Affect Pain-Like Behaviors but Mitigates Sudomotor Impairment in a Murine Model of Deep Hind Paw Incision.

The involvement of hypoxic response mechanisms in local functional impairments in surgical wounds is unclear. In the present study, we characterized tissue hypoxia in surgical wounds and investigated the role of pharmacological ischemic conditioning (PIC) using roxadustat, an oral prolyl hydroxylase domain enzyme inhibitor, in postoperative local functional impairments in a murine model of deep hind paw incision. Male BALB/cAJcl mice aged 9-13 weeks were used in all experiments. Plantar skins of mice that underwent surgical incision were subjected to immunohistochemistry to localise tissue hypoxia. Pain-like behaviours and sudomotor function were compared between mice treated with 6-week perioperative PIC and control mice. The effects of PIC were examined in vitro by immunocytochemistry using sympathetically differentiated PC12 cells and in vivo by immunohistochemistry using plantar skins collected on postoperative day 21. Prominent tissue hypoxia was detected within axons in the nerve bundles underneath surgical wounds. Six-week perioperative PIC using roxadustat failed to ease spontaneous pain-like behaviors; however, it mitigated local sudomotor impairment postoperatively. Upregulation of sympathetic innervation to the eccrine glands was observed in the PIC-treated skins collected on postoperative day 21, in accordance with the in vitro study wherein roxadustat promoted neurite growth of sympathetically differentiated PC12 cells. This study suggests that tissue hypoxia is involved in the pathogenesis of local sudomotor dysfunction associated with surgical trauma. Targeting the hypoxic response mechanisms with PIC may be of therapeutic potential in postsurgical local sympathetic impairments that can be present in complex regional pain syndrome.

Collagen hydrogel with multiple antimicrobial mechanisms as anti-bacterial wound dressing

Wound infection by multidrug-resistant bacteria seriously threatens human life. Chronic wounds, with necrosis, persistent inflammation, and covered by hypoxic tissue, seriously hinder anti-infection treatments. Herein, we have developed a multifunctional hydrogel dressing with antibacterial activity in the hypoxia environment to promote wound healing. The hydrogel comprises Cypate-conjugated antimicrobial peptides (AMP-Cypates), liposome-encapsulated perfluorodecalin, and recombinant type III collagen. AMP-Cypates exhibited outstanding antibacterial activity, jointly achieved through antimicrobial peptide (AMP) activity, photothermal therapy (PTT), and photodynamic therapy (PDT). The perfluorodecalin liposomes act as the oxygen carrier to mitigate wound hypoxia condition and enhance the efficacy of PDT. The recombinant type III collagen in the hydrogel further promoted the healing of the wounds together with the eradication of bacterial infection. Taken together, the hydrogel dressing provides a platform for integrating multiple antimicrobial mechanisms for the rapid removal of bacterial infection and the healing of chronic wounds.

Dextran-shelled oxygen-loaded nanodroplets modulate macrophages killing and inflammatory response to Enterococcus faecalis

Chronic wounds are associated with inflammation, infections, and hypoxic environment. Macrophages play a crucial role in wound healing removing bacteria and secreting signal molecules to coordinate tissue repair. Recently, dextran-shelled Oxygen-Loaded NanoDroplets (OLNDs) have been proposed as new tools to counteract hypoxia in chronic wounds. Here we investigated the effects of OLNDs on Enterococcus faecalis (E. faecalis) killing and the secretion of inflammatory and angiogenic factors by murine (BMDM) and human (dTHP-1, differentiated THP-1) macrophages, in normoxia and hypoxia. Both OLNDs and Oxygen-Free NanoDroplets (OFNDs) significantly increased reactive oxygen species production by BMDM in normoxia (4.1 and 4 fold increase by 10% OLNDs and OFNDs, respectively, after 120 min) and hypoxia (3.8 and 4 fold increase by 10% OLNDs and OFNDs respectively) but not by dTHP-1. Moreover, only OLNDs induced nitric oxide secretion by BMDM in normoxia. Consequently, both nanodroplets improved E. faecalis killing by BMDM in normoxia (% of killing OLNDs = 44.2%; p < 0.01; OFNDs = 41.4%; p < 0.05) and hypoxia (% of killing OLNDs = 43.1%; p < 0.01; OFNDs = 37.7%; p < 0.05), while dTHP-1-mediated killing was not affected. The secretion of the inflammatory cytokines (TNFα, IL-6, IL-1β) induced by E. faecalis infection in dTHP-1 was reduced by both types of nanodroplets, suggesting a novel anti-inflammatory activity of the dextran shell. Instead, the increase of VEGF induced by hypoxia was reduced only by OLNDs. These data provide new knowledge on the effects of OLNDs as innovative adjuvant in chronic wounds healing promoting bacterial killing and reducing inflammation.

Dynamic Role of Oxygen in Wound Healing: A Microbial, Immunological, and Biochemical Perspective.

A wound is a temporary break in the continuity of the protective skin barrier. Wound healing is central in maintaining the body's normal homeostatic mechanism, and open wounds raise the risk of microbial infection and amputation. A successful wound healing event is achieved through a series of evolutionarily conserved biochemical pathways orchestrated by various cytokines, growth factors, and immune cells. Chronic wounds are generally oxygen-deficient, and wound hypoxia impairs the wound healing process. Therefore, the use of external oxygen may improve wound health by reducing wound hypoxia, promoting tissue regeneration and granulation tissue formation, reducing anaerobic bacteria colonization, and promoting the growth of beneficial aerobic bacteria. Relevant data were searched and gathered from scientific databases, including PubMed, ScienceDirect, and Google Scholar using relevant keywords, such as "Chronic Wounds", "Topical Oxygen Therapy", "Inflammatory Markers/ Lactate/ Matrix Metalloproteinase", "Collagen", and "Wound Healing". Relevant articles were shortlisted and used in the present study. Chronic wounds show higher expression of pro-inflammatory mediators, such as C-reactive protein, and higher levels of tissue-degrading matrix metalloproteinases. In addition, chronic wounds are generally oxygen-deficient, and wound hypoxia is directly associated with wound deterioration. Several microbial, immunological, and biochemical markers show a direct association with the oxygen availability in the wound. Therefore, a detailed understanding of these microbial, immunological, and biochemical markers will certainly help clinicians understand the interplay between various factors and topical oxygen therapy and may improve patient outcomes.

Multifunctional hydrogel platform for biofilm scavenging and O2 generating with photothermal effect on diabetic chronic wound healing

Diabetic wound treatment remains a major challenge due to the difficulties of eliminating bacterial biofilm and relieving wound hypoxia. To address these issues simultaneously, a multifunctional Dex-SA-AEMA/MnO2/PDA (DSAMP) hydrogel platform was developed with excellent biocompatibility and porous structure. The hydrogel could absorb the exudate, maintain humidity and permeate oxygen, which was prepared by encapsulating polydopamine (PDA) and manganese dioxide (MnO2) into Dex-SA-AEMA (DSA) hydrogel by UV irradiation. With the addition of PDA, the DSAMP hydrogel was proved to eliminate the biofilm after NIR photodynamic therapy (PTT, 808 nm) irradiation at 54 °C. Furthermore, in order to mitigate hypoxia wound microenvironment, MnO2 nanoparticles were added to convert the endogenous hydrogen peroxide (H2O2) into oxygen (O2, 16 mg L−1). The diabetic wound in vivo treated by DSAMP hydrogel was completely healed on 14 days. It was revealed that the DSAMP hydrogel possessed a great potential as dressing for diabetic chronic wound healing.

Hyperbaric oxygen therapy: when pressure is good for diabetic foot ulcers.

The diabetic foot ulcer (DFU) as a common complication of diabetes. Even with adequate treatment, up to 35% of these ulcers do not heal. This is due to the effect of aging, repeated ischemia-reperfusion (IR) injury, bacterial colonisation of the wound and chronic hypoxia. All wound-healing processes are highly dependent on oxygen, so hyperbaric oxygen therapy (HBOT) can be employed to improve wound healing and correct the four pathophysiological factors for chronic wounds. It is, in fact, internationally recognised as a treatment option for non-healing DFUs. Several trials and systematic reviews have been performed on its efficacy, which show a positive trend towards increased wound healing and reduced amputation risk. Some controversy exists due to contradictory results in these studies, which may be due to grouping patients with and without peripheral arterial occlusive disease (PAOD) together. Side effects are usually mild and transient, and the treatment is considered safe.

Polydeoxyribonucleotide: A Promising Biological Platform to Accelerate Impaired Skin Wound Healing.

The normal wound healing process is characterized by a complex, highly integrated cascade of events, requiring the interactions of many cell types, including inflammatory cells, fibroblasts, keratinocytes and endothelial cells, as well as the involvement of growth factors and enzymes. However, several diseases such as diabetes, thermal injury and ischemia could lead to an impaired wound healing process characterized by wound hypoxia, high levels of oxygen radicals, reduced angiogenesis, decreased collagen synthesis and organization. Polydeoxyribonucleotide (PDRN) has been used to improve wound healing through local and systemic administration thanks to its ability to promote cell migration and growth, angiogenesis, and to reduce inflammation on impaired wound healing models in vitro, in vivo and clinical studies. In light of all these observations, the aim of this review is to provide a full overview of PDRN applications on skin regeneration. We reviewed papers published in the last 25 years on PubMed, inserting “polydeoxyribonucleotide and wound healing” as the main search term. All data obtained proved the ability of PDRN in promoting physiological tissue repair through adenosine A2A receptor activation and salvage pathway suggesting that PDRN has proven encouraging results in terms of healing time, wound regeneration and absence of side effects.

The Bioactive Core and Corona Synergism of Quantized Gold Enables Slowed Inflammation and Increased Tissue Regeneration in Wound Hypoxia.

The progress of wound regeneration relies on inflammation management, while neovascular angiogenesis is a critical aspect of wound healing. In this study, the bioactive core and corona synergism of quantized gold (QG) were developed to simultaneously address these complicated issues, combining the abilities to eliminate endotoxins and provide oxygen. The QG was constructed from ultrasmall nanogold and a loosely packed amine-based corona via a simple process, but it could nonetheless eliminate endotoxins (a vital factor in inflammation also called lipopolysaccharides) and provide oxygen in situ for the remodeling of wound sites. Even while capturing endotoxins through electrostatic interactions, the catalytic active sites inside the nanogold could maintain its surface accessibility to automatically transform the overexpressed hydrogen peroxide in hypoxic wound regions into oxygen. Since the inflammatory stage is an essential stage of wound healing, the provision of endotoxin clearance by the outer organic corona of the QG could slow inflammation in a way that subsequently promoted two other important stages of wound bed healing, namely proliferation and remodeling. Relatedly, the efficacy of two forms of the QG, a liquid form and a dressing form, was demonstrated at wound sites in this study, with both forms promoting the development of granulation, including angiogenesis and collagen deposition. Thus, the simply fabricated dual function nanocomposite presented herein not only offers reduced batch-to-batch variation but also increased options for homecare treatments.

MAP4 regulates Tctex-1 and promotes the migration of epidermal cells in hypoxia.

After acute wound formation, the oxygen supply is reduced, which results in the formation of an acute hypoxic microenvironment; whether this hypoxic microenvironment enhances epidermal cell migration and the underlying regulatory molecular mechanism of this effect are unclear. In this study, HaCaT cells were maintained under hypoxic (1% oxygen) or normoxic conditions. Methods including immunofluorescence staining, wound scratch assays, transwell assays, Western blotting and high- and low-expression lentiviral vector transfection were utilized to observe the changes in cell migration, microtubule dynamics and the expression levels of microtubule-associated protein (MAP) 4 and the light chain protein DYNLT1 (Tctex-1). The possible mechanisms were studied and discussed. The results showed that epidermal cell migration was enhanced during early hypoxia. Further experiments revealed that MAP4 regulates microtubule dynamics and promotes epidermal cell migration through Tctex-1. MAP4 and Tctex-1 play important roles in regulating the migration of epidermal cells under hypoxia. This evidence will provide a basis for further revealing the cellular and molecular mechanisms of local wound hypoxia and for promoting wound healing.

A hypoxia response element in the Vegfa promoter is required for basal Vegfa expression in skin and for optimal granulation tissue formation during wound healing in mice.

Hypoxia in skin wounds is thought to contribute to healing through the induction of hypoxia inducible factor-1 (HIF-1). Although HIF-1 can regulate the expression of vascular endothelial growth factor A (Vegfa), whether hypoxia and HIF-1 are required to induce Vegfa expression in the context of wound healing is unknown. To test this hypothesis, we evaluated Vegfa expression and wound healing in mutant mice that lack a functional HIF-1 binding site in the Vegfa promoter. Full-thickness excisional wounds were made using a biopsy punch, left to heal by second intention, and granulation tissue isolated on a time course during healing. mRNA levels of Vegfa and its target genes platelet-derived growth factors B (Pdgfb) and stromal cell-derived factor-1 (Sdf1) were measured by RT-qPCR, and HIF-1alpha and VEGFA protein levels measured by immunoblotting. Lower levels of Vegfa, Pdgf1 and Sdf1 mRNA were found in intact skin of mutant mice relative to wild-type controls (n = 6 mice/genotype), whereas levels in granulation tissue during wound healing were unaltered. VEGFA protein levels were also lower in intact skin of the mutant versus the wild-type mice. Decreased Vegfa mRNA levels in skin of mutant mice could not be attributed to decreased HIF-1alpha protein expression, and were therefore a consequence of the loss of HIF-1 responsiveness of the Vegfa promoter. Comparative histologic analyses of healing wounds in mutant and wild-type mice (n = 8 mice/genotype) revealed significant defects in granulation tissue in the mutant mice, both in terms of quantity and capillary density, although epithelialization and healing rates were unaltered. We conclude that HIF-1 is not a major regulator of Vegfa expression during wound healing; rather, it serves to maintain basal levels of expression of Vegfa and its target genes in intact skin, which are required for optimal granulation tissue formation in response to wounding.

The Impact of Tourniquet Release Time on Wound Healing in Patients Undergoing Tibia Fracture Plating Surgery

Background: The use of tourniquet is very common in orthopedic surgeries. By obstructing blood flow in the limb, tourniquet may result in muscle ischemia and skin flap hypoxia. This study aimed at determining and comparing the effects of tourniquet release time on wound healing in patients undergoing tibia fracture plating surgery. Methods: This study was a randomized clinical trial, wherein 40 patients with acute extra-articular tibia fractures were randomly assigned to 2 groups of A (releasing the tourniquet after fracture fixation and before wound closure) and B (releasing the tourniquet after wound closure and application of compression dressing). Duration of surgery in each group was recorded and independent t test was utilized to compare the 2 groups. The wound healing rate was investigated in the patients 24 hours and 14 days after surgery using the Redness, Oedema, Ecchymosis, Discharge, Approximation (REEDA) scale. In this tool, 0 represents “lack of the variable” and 3 indicates “maximum variable score”. The scores in this scale range from 0 to 15. The Mann-Whitney test was used in order to compare the wound healing rates between the 2 groups. Results: There was no significant difference between the 2 groups concerning the average duration of surgery. Wound redness, edema, ecchymosis, discharge, approximation, and the general condition of wound healing showed no significant difference in the 2 groups 24 hours after surgery, while there was a significant difference 14 days after surgery with the aforementioned parameters being greater in group B than group A. Conclusions: The results showed that releasing the tourniquet before wound closure in group A led to improved wound healing. Wounds need oxygen for restoration and prevention from infections. As the use of tourniquet occludes blood flow to the limb for a while, it can result in increased wound hypoxia after surgery and delayed healing process; hence, less tourniquet time is more desirable for oxygenation of tissues and wound dryness.

AntihypoxamiR functionalized gramicidin lipid nanoparticles rescue against ischemic memory improving cutaneous wound healing

Peripheral vasculopathies cause severe wound hypoxia inducing the hypoxamiR miR-210. High level of miR-210, persisting in wound-edge tissue as ischemic memory, suppresses oxidative metabolism and inhibits cell proliferation necessary for healing. In wound-edge tissue of chronic wound patients, elevated miR-210 was tightly associated with inhibition of epidermal cell proliferation as evident by lowered Ki67 immunoreactivity. To inhibit miR-210 in murine ischemic wound-edge tissue, we report the formulation of antihypoxamiR functionalized gramicidin lipid nanoparticles (AFGLN). A single intradermal delivery of AFGLN encapsulating LNA-conjugated anti-hypoximiR-210 (AFGLNmiR-210) lowered miR-210 level in the ischemic wound-edge tissue. In repTOP™mitoIRE mice, AFGLNmiR-210 rescued keratinocyte proliferation as visualized by in vivo imaging system (IVIS). 31P NMR studies showed elevated ATP content at the ischemic wound-edge tissue following AFGLNmiR-210 treatment indicating recovering bioenergetics necessary for healing. Consistently, AFGLNmiR-210 improved ischemic wound closure. The nanoparticle based approach reported herein is effective for miR-directed wound therapeutics warranting further translational development.

The Role of Hypoxia-Inducible Factor in Wound Healing

Significance: Poor wound healing remains a significant health issue for a large number of patients in the United States. The physiologic response to local wound hypoxia plays a critical role in determining the success of the normal healing process. Hypoxia-inducible factor-1 (HIF-1), as the master regulator of oxygen homeostasis, is an important determinant of healing outcomes. HIF-1 contributes to all stages of wound healing through its role in cell migration, cell survival under hypoxic conditions, cell division, growth factor release, and matrix synthesis throughout the healing process. Recent Advances: Positive regulators of HIF-1, such as prolyl-4-hydroxylase inhibitors, have been shown to be beneficial in enhancing diabetic ischemic wound closure and are currently undergoing clinical trials for treatment of several human-ischemia-based conditions. Critical Issues: HIF-1 deficiency and subsequent failure to respond to hypoxic stimuli leads to chronic hypoxia, which has been shown to contribute to the formation of nonhealing ulcers. In contrast, overexpression of HIF-1 has been implicated in fibrotic disease through its role in increasing myofibroblast differentiation leading to excessive matrix production and deposition. Both positive and negative regulators of HIF-1 therefore provide important therapeutic targets that can be used to manipulate HIF-1 expression where an excess or deficiency in HIF-1 is known to correlate with pathogenesis. Future Directions: Targeting HIF-1 during wound healing has many important clinical implications for tissue repair. Counteracting the detrimental effects of excessive or deficient HIF-1 signaling by modulating HIF-1 expression may improve future management of poorly healing wounds.