Effects of a topical aqueous oxygen emulsion on collagen deposition and angiogenesis in a porcine deep partial-thickness wound model

Dissolved oxygen technologies as a novel strategy for non-healing wounds: A critical review

Non-healing wounds are steadily becoming a global-health issue. Prolonged hypoxia propagates wound chronicity; yet, oxygenating treatments are considered inadequate to date. Dissolved oxygen (DO) in aqueous solutions introduces a novel approach to enhanced wound oxygenation, and is robustly evaluated for clinical applications. A systematic literature search was conducted, whereby experimental and clinical studies of DO technologies were categorized per engineering approach. Technical principles, methodology, endpoints and outcomes were analysed for both oxygenating and healing effects. Forty articles meeting our inclusion criteria were grouped as follows: DO solutions (17), oxygen (O₂ ) dressings (9), O₂ hydrogels (11) and O₂ emulsions (3). All technologies improved wound oxygenation, each to a variable degree. They also achieved at least one statistically significant outcome related to wound healing, mainly in epithelialization, angiogenesis and collagen synthesis. Scarcity in clinical data and methodological variability precluded quantitative comparisons among the biotechnologies studied. DO technologies warrantee further evaluation for wound oxygenation in the clinical setting. Standardised methodologies and targeted research questions are pivotal to facilitate global integration in healthcare.

Effect of supersaturated oxygen emulsion treatment on chloropicrin-induced chemical injury in ex vivo rabbit cornea

With a possibility for the use of chemical weapons in battlefield or in terrorist activities, effective therapies against the devastating ocular injuries, from their exposure, are needed. Oxygen plays a vital role in ocular tissue preservation and wound repair. We tested the efficacy of supersaturated oxygen emulsion (SSOE) in reducing ex vivo corneal and keratocyte injury from chloropicrin (CP). CP, currently used as a pesticide, is a chemical threat agent like the vesicating mustard agents and causes severe corneal injury. Since our previous study in human corneal epithelial cells showed the treatment potential of SSOE (55 %), we further tested its efficacy in an ex vivo CP-induced rabbit corneal injury model. Corneas were exposed to CP (700 nmol) for 2 h, washed and cultured with or without SSOE for 24 h or 96 h. At 96 h post CP exposure, SSOE treatment presented a healing tendency of the corneal epithelial layer, and abrogated the CP-induced epithelial apoptotic cell death. SSOE treatment also reduced the CP induced DNA damage (H2A.X phosphorylation) and inflammatory markers (e.g. MMP9, IL-21, MIP-1β, TNFα). Further examination of the treatment efficacy of SSOE alone or in combination with other therapies in in vivo cornea injury models for CP and vesicants, is warranted.

A Supersaturated Oxygen Emulsion for the Topical Treatment of Ocular Trauma

INTRODUCTION

Roughly 13% of all battlefield injuries include some form of ocular trauma. Ocular tissue preservation is critical for wound healing for warfighters with ocular injuries. Our team hypothesized that oxygen plays a vital role in ocular tissue preservation and wound healing and has developed a supersaturated oxygen emulsion (SOE) for the topical treatment of ocular trauma.

MATERIALS AND METHODS

The partial pressure of oxygen (PO2) was measured in the SOE. Safety and efficacy studies were carried out in primary human corneal epithelial (HCE) cells, as the outermost layer is the first barrier to chemical and mechanical injury. Western blot, scratch assay, and MTT assays were conducted to determine the effect of the SOE on various molecular markers, the rate of scratch closure, and cellular viability, respectively.

RESULTS

Data indicate that the SOE releases oxygen in a time-dependent manner, reaching a partial pressure within the emulsion over four times atmospheric levels. Studies in HCE cells indicate that application of the SOE does not lead to DNA damage, promote cell death, or hinder the rate of scratch closure and enhances cellular viability. Preliminary studies were carried out with chloropicrin (CP; developed as a chemical warfare agent and now a commonly used pesticide) as a chemical agent to induce ocular injury in HCE cells. CP exposures showed that SOE treatment reverses CP-induced DNA damage, apoptotic cell death, and oxidative stress markers.

CONCLUSIONS

Maintaining adequate tissue oxygenation is critical for tissue preservation and wound repair, especially in avascular tissues like the cornea. Further studies examining the application of the SOE in corneal injury models are warranted.

The vaginal microcirculation after prolapse surgery

Aims

Oxygen plays a crucial role in wound healing after prolapse surgery. Trauma to the vaginal vasculature might limit the delivery of oxygen to the surgical wound, which may negatively affect wound healing and regeneration of connective tissue. This possibly increases the future risk of recurrence. We aimed to determine the effects of vaginal prolapse surgery on the microcirculation of the vaginal wall.

Methods

We evaluated the vaginal microcirculation in healthy participants without known vascular disease undergoing anterior and/or posterior colporrhaphy. We used incident dark‐field imaging for in vivo assessment before and after (1 day, 2 weeks, and 6 weeks) surgery. We studied perfusion (microvascular flow index [MFI]), angioarchitecture (morphology/layout of microvessels) and capillary density.

Results

Ten women were included. Interindividual differences were observed 1 day postoperatively with regard to perfusion and angioarchitecture. Microvascular flow at the surgical site was absent or significantly reduced in some participants, whereas normal microvascular flow was observed in others (MFI range 0–3). Perfusion and angioarchitecture had been restored in all participants after 6 weeks (MFI range 2–3), regardless of the extent of vascular trauma 1 day postoperatively.

Conclusions

The difference in the extent of vascular trauma between women undergoing seemingly identical surgical procedures suggests that some individuals are more susceptible to vascular trauma than others. Delivery of oxygen to the wound and subsequent wound healing may be compromised in these cases, which could be related to the development of anatomical recurrence. Future studies should investigate whether there is a relationship between the vaginal microvasculature and the recurrence of prolapse.

Topical oxygen therapy & micro/nanobubbles: a new modality for tissue oxygen delivery

Up to 15 billion dollars of US health care expenditure each year is consumed by treatment of poorly healing wounds whose etiologies are often associated with aberrancies in tissue oxygenation. To address this issue, several modes of tissue oxygen delivery systems exist, including Hyperbaric Oxygen Therapy (HBOT) and Topical Oxygen Therapy (TOT), but their efficacies have yet to be fully substantiated. Micro/nanobubbles (MNBs), which range anywhere from 100 μm to <1 μm in diameter and are relatively stable for hours, offer a new mode of oxygen delivery to wounds. The aim of this article is to systematically review literature examining the use of TOT for wound healing and use of MNBs for tissue oxygenation using the MEDLINE database. The search yielded 87 articles (12 MNB articles and 75 TOT articles), of which 52 met the inclusion criteria for this literature review (12 MNB articles and 40 TOT articles). Additionally, we present an analysis on the efficacy of our MNB generating technology and propose its use as a wound healing agent.

Intravenous oxygen: a novel method of oxygen delivery in hypoxemic respiratory failure?

INTRODUCTION

Hypoxemic respiratory failure is a common problem in critical care. Current management strategies, including mechanical ventilation and extracorporeal membranous oxygenation, can be efficacious but these therapies put patients at risk for toxicities associated with invasive forms of support. Areas covered: In this manuscript, we discuss intravenous oxygen (IVO₂), a novel method to improve oxygen delivery that involves intravenous administration of a physiologic solution containing dissolved oxygen at hyperbaric concentrations. After a brief review of the physiology behind supersaturated fluids, we summarize the current evidence surrounding IVO₂. Expert commentary: Although not yet at the stage of clinical testing in the United States and Europe, IVO₂ has been used safely in Asia. Furthermore, preliminary laboratory data have been encouraging, suggesting that IVO₂ may play a role in the management of patients with hypoxemic respiratory failure in years to come. However, significantly more work needs to be done, including definitive evidence that such a therapy is safe, before it can be included in an intensivist's arsenal for hypoxemic respiratory failure.

A topical aqueous oxygen emulsion stimulates granulation tissue formation in a porcine second-degree burn wound

BACKGROUND

Oxygen is an essential substance for wound healing. Limited studies have shown that topical oxygen can influence healing. This study evaluated the effects of a Topical Oxygen Emulsion (TOE) on burn wound healing.

METHODS

A porcine second-degree burn wound model was used in the study. Burn wounds were randomly assigned to TOE, vehicle control, and no-treatment (air) groups. Effects of TOE on the granulation tissue formation and angiogenesis were studied using hematoxylin and eosin histological analysis. Protein production and gene expression of types I and III collagen and vascular endothelial growth factor (VEGF) were determined using immunofluorescent staining and Reverse Transcription and Polymerase Chain Reaction (RT-PCR), respectively.

RESULTS

The TOE treated wounds exhibited better angiogenesis and granulation tissue formation by histology examination. The immunofluorescence staining and RT-PCR analysis demonstrated that protein production and mRNA expression of VEGF and collagen III were significantly higher in TOE treatment group than vehicle alone and air control groups, while there was no significant difference in the level of collagen I.

CONCLUSIONS

Our data demonstrate that TOE enhances burn wound healing via stimulating the expression of VEGF and type III collagen and strongly indicates the potential use of TOE in wounds.

Neuroprotectin/protectin D1: endogenous biosynthesis and actions on diabetic macrophages in promoting wound healing and innervation impaired by diabetes

Dysfunction of macrophages (MΦs) in diabetic wounds impairs the healing. MΦs produce anti-inflammatory and pro-resolving neuroprotectin/protectin D1 (NPD1/PD1, 10R,17S-dihydroxy-docosa-4Z,7Z,11E,13E,15Z,19Z-hexaenoic acid); however, little is known about endogenous NPD1 biosynthesis by MΦs and the actions of NPD1 on diabetic MΦ functions in diabetic wound healing. We used an excisional skin wound model of diabetic mice, MΦ depletion, MΦs isolated from diabetic mice, and mass spectrometry-based targeted lipidomics to study the time course progression of NPD1 levels in wounds, the roles of MΦs in NPD1 biosynthesis, and NPD1 action on diabetic MΦ inflammatory activities. We also investigated the healing, innervation, chronic inflammation, and oxidative stress in diabetic wounds treated with NPD1 or NPD1-modulated MΦs from diabetic mice. Injury induced endogenous NPD1 biosynthesis in wounds, but diabetes impeded NPD1 formation. NPD1 was mainly produced by MΦs. NPD1 enhanced wound healing and innervation in diabetic mice and promoted MΦs functions that accelerated these processes. The underlying mechanisms for these actions of NPD1 or NPD1-modulated MΦs involved 1) attenuating MΦ inflammatory activities and chronic inflammation and oxidative stress after acute inflammation in diabetic wound, and 2) increasing MΦ production of IL10 and hepatocyte growth factor. Taken together, NPD1 appears to be a MΦs-produced factor that accelerates diabetic wound healing and promotes MΦ pro-healing functions in diabetic wounds. Decreased NPD1 production in diabetic wound is associated with impaired healing. This study identifies a new molecular target that might be useful in development of more effective therapeutics based on NPD1 and syngeneic diabetic MΦs for treatment of diabetic wounds.

Maresin-like lipid mediators are produced by leukocytes and platelets and rescue reparative function of diabetes-impaired macrophages

Nonhealing diabetic wounds are associated with impaired macrophage (Mf) function. Leukocytes and platelets (PLT) play crucial roles in wound healing by poorly understood mechanisms. Here we report the identification and characterization of the maresin-like(L) mediators 14,22-dihydroxy-docosa-4Z,7Z,10Z,12E,16Z,19Z-hexaenoic acids, 14S,22-diHDHA (maresin-L1), and 14R,22-diHDHA (maresin-L2) that are produced by leukocytes and PLT and involved in wound healing. We show that 12-lipoxygenase-initiated 14S-hydroxylation or cytochrome P450 catalyzed 14R-hydroxylation and P450-initiated ω(22)-hydroxylation are required for maresin-L biosynthesis. Maresin-L treatment restores reparative functions of diabetic Mfs, suggesting that maresin-Ls act as autocrine/paracrine factors responsible for, at least in part, the reparative functions of leukocytes and PLT in wounds. Additionally, maresin-L ameliorates Mf inflammatory activation and has the potential to suppress the chronic inflammation in diabetic wounds caused by activation of Mfs. These findings provide initial insights into maresin-L biosynthesis and mechanism of action and potentially offer a therapeutic option for better treatment of diabetic wounds.