Molecular Biomarkers of Oxygen Therapy in Patients with Diabetic Foot Ulcers

Recurrence rates after healing in patients with neuroischemic diabetic foot ulcers healed with and without sucrose octasulfate-impregnated dressings: A 1-year comparative prospective study

To compare recurrence rates after a 1-year follow-up period of healed neuroischemic diabetic foot ulcers after treatment with or without sucrose octasulfate impregnated dressing. A 1-year prospective study with two arms was conducted between April 2021 and April 2023 on 92 patients with healed neuroischemic diabetic foot ulcers. Patients were divided into two groups; the treatment group, that includes patients healed with a sucrose octasulfate-impregnated dressing, and the control group, which includes patients treated with other local treatments different from sucrose octasulfate-impregnated dressings. After healing, patients were prospectively followed up during 1-year and assessed monthly in the specialised outpatient clinics. The main outcome of the study was ulcer recurrence after wound healing within 1 year follow-up. Secondary outcomes were minor or major amputation and all causes of death. Fifty patients in the treatment group and 42 patients in the control group were included. Fourteen (28%) patients suffered from a reulceration event in the treatment group compared to 28 (66.7%) in the control group, p < 0.001. Time to recurrence in the treatment group was 10 (16.26-2.75) and 11.50 (30.75-5.25) weeks in the control group, p = 0.464. There were no observed differences in the minor amputation rates between the two groups: 15.2% (n = 7) in the treatment group and 7.1% (n = 3) in the control group (p = 0.362). Major amputations and death outcomes were exclusively observed in the treatment group. Specifically, four major amputations (8.7%) in the treatment group were complications arising from recurring events complicated by infection during the SARS-CoV-2 period. Seven patients died due to complications not related with local therapy. The relative risk of recurrence was 20.18 times higher in the control group compared with those treated with octasulfate dressing (p < 0.001). Treatment with sucrose octasulfate-impregnated dressings can decrease recurrence rates of neuroischaemic diabetic foot ulcers more effectively than neutral dressings. Besides, it may enhance the foot's clinical properties in patients with poor microcirculation, which could aid in preventing future recurrences.

Hyperoxia in Sepsis and Septic Shock: A Comprehensive Review of Clinical Evidence and Therapeutic Implications

Sepsis and septic shock are leading causes of mortality in intensive care units, characterized by a dysregulated immune response to infection, leading to severe organ dysfunction. Oxygen therapy is a cornerstone of supportive care in sepsis management, aimed at correcting hypoxemia and improving tissue oxygenation. However, the administration of supplemental oxygen must be carefully managed to avoid hyperoxia, which can lead to oxidative stress and additional tissue damage. This review aims to comprehensively analyze the clinical evidence regarding hyperoxia in the context of sepsis and septic shock, evaluating its potential therapeutic benefits and risks and discussing the implications for clinical practice. A thorough literature review included observational studies, randomized controlled trials (RCTs), meta-analyses, and clinical guidelines. The review focuses on the pathophysiology of sepsis, the mechanisms of hyperoxia-induced injury, and the clinical outcomes associated with different oxygenation strategies. The evidence suggests that while oxygen is crucial in managing sepsis, the risk of hyperoxia-related complications is significant. Hyperoxia has been associated with increased mortality and adverse outcomes in septic patients due to mechanisms such as oxidative stress, impaired microcirculation, and potential worsening of organ dysfunction. RCTs and meta-analyses indicate that conservative oxygen therapy may be beneficial in reducing these risks, though optimal oxygenation targets remain under investigation. This review highlights the importance of careful oxygen management in sepsis and septic shock, emphasizing the need for individualized oxygen therapy to avoid the dangers of hyperoxia. Further research is required to refine oxygenation strategies, establish clear clinical guidelines, and optimize outcomes for sepsis and septic shock patients. Balancing adequate oxygenation with the prevention of hyperoxia-induced injury is crucial in improving the prognosis of these critically ill patients.

Processed microalgae: green gold for tissue regeneration and repair

As novel biomedical materials, microalgae have garnered significant interest because of their ability to generate photosynthetic oxygen, their antioxidant activity, and their favorable biocompatibility. Many studies have concentrated on the hypoxia-alleviating effects of microalgae within tumor microenvironments. However, recent findings indicate that microalgae can significantly increase the regeneration of various tissues and organs. To augment microalgae's therapeutic efficacy and mitigate the limitations imposed by immune clearance, it is essential to process microalgae through various processing strategies. This review examines common microalgal species in biomedical applications, such as Chlorella, Chlamydomonas reinhardtii, diatoms, and Spirulina. This review outlines diverse processing methods, including microalgae extracts, microalgae‒nanodrug composite delivery systems, surface modifications, and living microalgae‒loaded hydrogels. It also discusses the latest developments in tissue repair using processed microalgae for skin, gastrointestinal, bone, cardiovascular, lung, nerve, and oral tissues. Furthermore, future directions are presented, and research gaps for processed microalgae are identified. Collectively, these insights may inform the innovation of processed microalgae for various uses and offer guidance for ongoing research in tissue repair.

Formulation strategies to provide oxygen-release to contrast local hypoxia for transplanted islets

Islet transplantation refers to the transfusion of healthy islet cells into the diabetic recipients and reconstruction of their endogenous insulin secretion to achieve insulin independence. It is a minimally invasive surgery that holds renewed prospect as a therapeutic method for type 1 diabetes mellitus. However, poor oxygenation in the early post-transplantation period is considered as one of the major causes of islet loss and dysfunction. Due to the metabolism chacteristics, islets required a high supply of oxygen for cell survival while a hypoxia environment would lead to severe islet loss and graft failure. Emerging strategies have been proposed, including providing external oxygen and speeding up revascularization. From the perspective of formulation science, it is feasible and practical to protect transplanted islets by oxygen-release before revascularization as opposed to local hypoxia. In this study, we review the potential formulation strategies that could provide oxygen-release by either delivering external oxygen or triggering localized oxygen generation for transplanted islets.

H2O2-PLA-(Alg)2Ca Hydrogel Enriched in Matrigel® Promotes Diabetic Wound Healing

Hydrogel-based dressings exhibit suitable features for successful wound healing, including flexibility, high water-vapor permeability and moisture retention, and exudate absorption capacity. Moreover, enriching the hydrogel matrix with additional therapeutic components has the potential to generate synergistic results. Thus, the present study centered on diabetic wound healing using a Matrigel-enriched alginate hydrogel embedded with polylactic acid (PLA) microspheres containing hydrogen peroxide (H2O2). The synthesis and physicochemical characterization of the samples, performed to evidence their compositional and microstructural features, swelling, and oxygen-entrapping capacity, were reported. For investigating the three-fold goal of the designed dressings (i.e., releasing oxygen at the wound site and maintaining a moist environment for faster healing, ensuring the absorption of a significant amount of exudate, and providing biocompatibility), in vivo biological tests on wounds of diabetic mice were approached. Evaluating multiple aspects during the healing process, the obtained composite material proved its efficiency for wound dressing applications by accelerating wound healing and promoting angiogenesis in diabetic skin injuries.

Pilot study: Utility of long-wave infrared thermography as a correlate to transcutaneous oximetry for candidates of hyperbaric oxygen therapy

Hyperbaric oxygen (HBO₂ ) has been used as an adjunctive treatment for the care of advanced non-healing diabetic foot ulcers (DFUs). A patient's in-chamber transcutaneous oximetry measurement (TCOM) is currently the most effective predictor for response to HBO₂ therapy but still excludes close to one in four patients who would benefit out of treatment groups when used for patient selection. Improving selection tools and criteria could potentially help better demonstrate HBO₂ therapy's efficacy for such patients. We sought to identify if long-wave infrared thermography (LWIT) measurements held any correlation with a patient's TCOM measurements and if LWIT could be used in a response prediction role for adjunctive HBO₂ therapy. To investigate, 24 patients already receiving TCOM measurements were enrolled to simultaneously be imaged with LWIT. LWIT measurements were taken throughout each patient's therapeutic course whether they underwent only standard wound care or adjunctive HBO₂ treatments. A significant correlation was found between in-chamber TCOM and post-HBO₂ LWIT. There was also a significant difference in the post-HBO₂ LWIT measurement from 1st treatment to 6 weeks or the last treatment recorded. These initial findings are important as they indicate a possible clinical use for LWIT in the selection process for patients for HBO₂ therapy. Larger studies should be carried out to further articulate the clinical use of LWIT in this capacity.

Development of a photosynthetic hydrogel as potential wound dressing for the local delivery of oxygen and bioactive molecules

The development of biomaterials to improve wound healing is a critical clinical challenge and an active field of research. As it is well described that oxygen plays a critical role in almost each step of the wound healing process, in this work, an oxygen producing photosynthetic biomaterial was generated, characterized, and further modified to additionally release other bioactive molecules. Here, alginate hydrogels were loaded with the photosynthetic microalgae Chlamydomonas reinhardtii, showing high integration as well as immediate oxygen release upon illumination. Moreover, the photosynthetic hydrogel showed high biocompatibility in vitro and in vivo, and the capacity to sustain the metabolic oxygen requirements of zebrafish larvae and skin explants. In addition, the photosynthetic dressings were evaluated in 20 healthy human volunteers following the ISO-10993-10-2010 showing no skin irritation, mechanical stability of the dressings, and survival of the photosynthetic microalgae. Finally, hydrogels were also loaded with genetically engineered microalgae to release human VEGF, or pre-loaded with antibiotics, showing sustained release of both bioactive molecules. Overall, this work shows that photosynthetic hydrogels represent a feasible approach for the local delivery of oxygen and other bioactive molecules to promote wound healing. STATEMENT OF SIGNIFICANCE: As oxygen plays a key role in almost every step of the tissue regeneration process, the development of oxygen delivering therapies represents an active field of research, where photosynthetic biomaterials have risen as a promising approach for wound healing. Therefore, in this work a photosynthetic alginate hydrogel-based wound dressing containing C. reinhardtii microalgae was developed and validated in healthy skin of human volunteers. Moreover, hydrogels were modified to additionally release other bioactive molecules such as recombinant VEGF or antibiotics. The present study provides key scientific data to support the use of photosynthetic hydrogels as customizable dressings to promote wound healing.

Hyperbaric Oxygen Therapy and Tissue Regeneration: A Literature Survey

By addressing the mechanisms involved in transcription, signaling, stress reaction, apoptosis and cell-death, cellular structure and cell-to-cell contacts, adhesion, migration as well as inflammation; HBO upregulates processes involved in repair while mechanisms perpetuating tissue damage are downregulated. Many experimental and clinical studies, respectively, cover wound healing, regeneration of neural tissue, of bone and cartilage, muscle, and cardiac tissue as well as intestinal barrier function. Following acute injury or in chronic healing problems HBO modulates proteins or molecules involved in inflammation, apoptosis, cell growth, neuro- and angiogenesis, scaffolding, perfusion, vascularization, and stem-cell mobilization, initiating repair by a variety of mechanisms, some of them based on the modulation of micro-RNAs. HBO affects the oxidative stress response via nuclear factor erythroid 2-related factor 2 (Nrf2) or c-Jun N-terminal peptide and downregulates inflammation by the modulation of high-mobility group protein B1 (HMGB-1), toll-like receptor 4 and 2 (TLR-4, TLR-2), nuclear factor kappa-B (NFκB), hypoxia-inducible factor (HIF-1α) and nitric oxide (NO•). HBO enhances stem-cell homeostasis via Wnt glycoproteins and mammalian target of rapamycin (mTOR) and improves cell repair, growth, and differentiation via the two latter but also by modulation of extracellular-signal regulated kinases (ERK) and the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT) pathway. The HBO-induced downregulation of matrix metalloproteinases-2 and 9 (MMP-2/-9), rho-associated protein kinase (ROCK) and integrins improve healing by tissue remodeling. Interestingly, the action of HBO on single effector proteins or molecules may involve both up- or downregulation, respectively, depending on their initial level. This probably mirrors a generally stabilizing potential of HBO that tends to restore the physiological balance rather than enhancing or counteracting single mechanisms.

Hyperbaric oxygen therapy for healthy aging: From mechanisms to therapeutics

Hyperbaric oxygen therapy (HBOT), a technique through which 100% oxygen is provided at a pressure higher than 1 atm absolute (ATA), has become a well-established treatment modality for multiple conditions. The noninvasive nature, favorable safety profile, and common clinical application of HBOT make it a competitive candidate for several new indications, one of them being aging and age-related diseases. In fact, despite the conventional wisdom that excessive oxygen accelerates aging, appropriate HBOT protocols without exceeding the toxicity threshold have shown great promise in therapies against aging. For one thing, an extensive body of basic research has expanded our mechanistic understanding of HBOT. Interestingly, the therapeutic targets of HBOT overlap considerably with those of aging and age-related diseases. For another, pre-clinical and small-scale clinical investigations have provided validated information on the efficacy of HBOT against aging from various aspects. However, a generally applicable protocol for HBOT to be utilized in therapies against aging needs to be defined as a subsequent step. It is high time to look back and summarize the recent advances concerning biological mechanisms and therapeutic implications of HBOT in promoting healthy aging and shed light on prospective directions. Here we provide the first comprehensive overview of HBOT in the field of aging and geriatric research, which allows the scientific community to be aware of the emerging tendency and move beyond conventional wisdom to scientific findings of translational value.

Novel therapeutic targets for diabetes-related wounds or ulcers: an update on preclinical and clinical research

INTRODUCTION

Diabetes-related wounds, particularly diabetes-related foot ulcers, are mainly caused by lack of foot sensation and high plantar tissue stress secondary to peripheral neuropathy, ischemia secondary to peripheral artery disease, and dysfunctional wound healing. Current management of diabetes-related wounds involves the offloading of high foot pressures and the treatment of ischemia through revascularization. Despite these treatments, the global burden of diabetes-related wounds is growing, and thus, novel therapies are needed. The normal wound healing process is a coordinated remodeling process orchestrated by fibroblasts, endothelial cells, phagocytes, and platelets, controlled by an array of growth factors. In diabetes-related wounds, these coordinated processes are dysfunctional. The past animal model and human research suggest that prolonged wound inflammation, failure to adequately correct ischemia, and impaired wound maturation are key therapeutic targets to improve diabetes-related wound healing.

AREAS COVERED

This review summarizes recent preclinical and clinical research on novel diabetes-related wound treatments. Animal models of diabetes-related wounds and recent studies testing novel therapeutic agents in these models are described. Findings from clinical trials are also discussed. Finally, challenges to identifying and implementing novel therapies are described.

EXPERT OPINION

Given the growing volume of promising drug therapies currently under investigation, it is expected within the next decade, that diabetes-related wound treatment will be transformed.

Topical Wound Oxygen Therapy in the Treatment of Chronic Diabetic Foot Ulcers

Oxygen is a critical component of many biological processes and is essential for wound healing. Chronic wounds are typically characterized as being hypoxic in that the partial pressure of oxygen (pO2) in the center of the wound is often below a critical threshold necessary to fully support those enzymatic processes necessary for tissue repair. Providing supplemental oxygen can effectively raise pO2 levels to better optimize functioning of these essential enzymes. While hyperbaric oxygen therapy has been well studied in this regard, comparative clinical studies have fallen short of providing clear evidence in support of this modality for healing chronic diabetic foot ulcers (DFU). Topical oxygen therapy (TOT) has been in clinical use for over 50 years with encouraging pre-clinical and clinical studies that have shown improved healing rates when compared to standard care. Nonetheless, TOT has heretofore been discounted as an unproven wound healing modality without theoretical or clinical evidence to support its use. This review shall provide a brief summary of the role of oxygen in wound healing and, specifically, discuss the different types of topical oxygen devices and associated studies that have convincingly shown their efficacy in healing chronic DFUs. The time has come for topical oxygen therapy to be embraced as a proven adjunctive modality in this regard.