Protease activity as a prognostic factor for wound healing in complex wounds

Dysfunctional crosstalk between macrophages and fibroblasts under LPS-infected and hyperglycemic environment in diabetic wounds

Diabetic wounds, especially diabetic foot ulcers, present a major clinical challenge due to delayed healing and prolonged inflammation. Macrophage-fibroblast interactions are essential for wound repair, yet this crosstalk is disrupted in diabetic wounds due to hyperglycemia and bacterial infection. This study investigates the dysfunctional communication between macrophages and fibroblasts, focusing on autocrine, paracrine, and juxtacrine signaling in simulated diabetic environments. Using monoculture and co-culture models of THP-1-derived macrophages and primary human dermal fibroblasts, we simulated conditions of normal glucose, LPS-induced infection, high glucose (with AGEs), and combined high glucose (with AGEs) and LPS. Macrophages in hyperglycemic and LPS-infected environments exhibited a pro-inflammatory M1 phenotype with elevated expression of CD80, and STAT1 and increased production of IL-1β, TNF-α, and MMP9. Fibroblast migration was significantly impaired under high glucose conditions, particularly in paracrine model. Secretome profiling showed heightened pro-inflammatory cytokines and proteases, with reduced anti-inflammatory markers (IL-10 and VEGF-A) under hyperglycemic conditions. Paracrine signaling exacerbated the inflammatory response, while juxtacrine signaling showed more moderate effects, conducive to healing. These findings highlight the pathological macrophage-fibroblast crosstalk in diabetic wounds, particularly under hyperglycemic and LPS-infected conditions, offering insights for potential immunomodulatory therapies aimed at restoring effective signaling and improving wound healing outcomes.

Immunomarker profiling in human chronic wound swabs reveals IL-1 beta/IL-1RA and CXCL8/CXCL10 ratios as potential biomarkers for wound healing, infection status and regenerative stage

BACKGROUND

Chronic wounds, such as diabetic foot ulcers, venous leg ulcers, and post-surgical wound healing disorders pose a significant challenge due to prolonged healing, risk of infection, and impaired quality of life. Persistent inflammation and impaired tissue remodeling are common in these wounds. Traditional diagnostic methods, including visual inspection and microbiological cultures, offer limited insight into the wound micro-environment. Immunomarker profiling could provide a deeper understanding of the molecular mechanisms underpinning wound healing, offering potential biomarkers for infection status and healing progression.

METHODS

This observational, multi-center cohort study, part of the 'Wound-BIOME' project, analyzed 110 swab samples from patients with acute and chronic wounds using multiplex immunoassays. Clinical parameters such as wound type, healing status, regeneration stage, and microbial burden were recorded. Total protein concentration was assessed, and 35 key immunomarkers, including cytokines (e.g. IL- 1α, IL- 1β), chemokines (CCL2, CXCL8, CXCL10), growth factors (FGF- 2, VEGF) and matrix metalloproteinases (MMP- 7, MMP- 9, MMP- 13), were quantified. Statistical analyses were performed to correlate immunomarker levels with clinical outcomes.

RESULTS

Pro-inflammatory markers, such as IL- 1β, IL- 18 and chemokines like CCL2 and CXCL8, were significantly elevated in non-healing and infected wounds compared to healing wounds. The study identified two new immunomarker ratios - IL- 1β/IL- 1RA and CXCL8/CXCL10 - as potential predictors of wound healing status. The IL- 1β/IL- 1RA ratio showed the highest accuracy for distinguishing healing from non-healing wounds (AUC = 0.6837), while the CXCL8/CXCL10 ratio was most effective in identifying infection (AUC = 0.7669).

CONCLUSIONS

Immunomarker profiling via wound swabbing offers valuable insights into the wound healing process. Elevated levels of pro-inflammatory cytokines and MMPs are associated with chronic inflammation and impaired healing. The IL- 1β/IL- 1RA and CXCL8/CXCL10 ratios emerge as promising biomarkers to distinguish between infection and inflammation, with potential in targeted wound care. Further studies are needed to validate these findings and implement them in clinical practice.

Surgical Bioengineering of the Microvasculature and Challenges in Clinical Translation

Tissue and organ dysfunction are major causes of worldwide morbidity and mortality with all medical specialties being impacted. Tissue engineering is an interdisciplinary field relying on the combination of scaffolds, cells, and biologically active molecules to restore form and function. However, clinical translation is still largely hampered by limitations in vascularization. Consequently, a thorough understanding of the microvasculature is warranted. This review provides an overview of (1) angiogenesis, including sprouting angiogenesis, intussusceptive angiogenesis, vascular remodeling, vascular co-option, and inosculation; (2) strategies for vascularized engineered tissue fabrication such as scaffold modulation, prevascularization, growth factor utilization, and cell-based approaches; (3) guided microvascular development via scaffold modulation with electromechanical cues, 3D bioprinting, and electrospinning; (4) surgical approaches to bridge the micro- and macrovasculatures in order to hasten perfusion; and (5) building specific vasculature in the context of tissue repair and organ transplantation, including skin, adipose, bone, liver, kidney, and lung. Our goal is to provide the reader with a translational overview that spans developmental biology, tissue engineering, and clinical surgery.

Superabsorbent wound dressings for the management of highly exuding wounds: a literature review

Exudate management is essential for creating a moist wound environment that promotes optimal healing, especially in highly exuding wounds, where choosing an appropriate wound dressing to handle high volumes of exudate is a key part of the wound management strategy. Superabsorbent wound dressings (SWDs) have been designed to absorb and retain large amounts of exudate. Thus, they are advocated for management of wounds with moderate-to-high levels of exudate to reduce the risk of leakage and damage to the periwound skin. The SWD category contains numerous brands with different structural and compositional designs. Those differences affect absorption capacity of the products, but also affect structural integrity, risk of leakage, adherence to the wound bed upon dressing removal etc. Herein, we aim to provide a brief overview of the clinical evidence and technical performance characteristics of the SWD category, and identify technical improvement areas. Clinical evidence within the SWD category was primarily limited to product evaluations, case series and case studies. With limited comparative clinical evidence available within this product category, we provide an overview of in vitro comparisons of technical performance characteristics related to absorption capacity, fluid retention, structural integrity, waterproofness, and ability to sequester host-derived enzymes and microorganisms. Substantial differences in in vitro performance characteristics in this product category were identified, which may have implications for their clinical performance. With the currently available in vitro evidence, there is no SWD showing superior performance across all functionalities, indicating a continued need for product development within this product category.

Neutrophil extracellular traps in wound healing

Wound healing is a complex and orchestrated process that involves hemostasis, inflammation, proliferation, and tissue remodeling. Neutrophil extracellular traps (NETs) are intricate web-like structures released by neutrophils, comprising decondensed chromatin, myeloperoxidase (MPO), and neutrophil elastase (NE), which play vital roles in regulating neutrophil-mediated immune regulation. While NETs contribute to wound healing, excessive activation induced by dysregulated inflammation can hinder the healing process. Understanding the pivotal role of NETs in wound healing and tissue remodeling, as well as their intricate interactions within the wound microenvironment, presents opportunities for innovative wound healing strategies. In this review we discuss the process of NET formation, explore the interactions between NETs and skin cells, and examine therapeutic strategies targeting NETs and drug delivery platforms to accelerate wound healing. Additionally, we discuss current clinical investigations and research challenges towards advancing wound care practices.

Assessment and Monitoring of the Wound Micro-Environment in Chronic Wounds Using Standardized Wound Swabbing for Individualized Diagnostics and Targeted Interventions

Background/Objectives: Patient-specific diagnostic and therapeutic approaches are important in the care of people with chronic wounds. The heterogeneity of underlying disease profiles and the diversity of the wound micro-environment make generalized approaches difficult. While high-throughput molecular diagnostic methods are increasingly widespread and available, the analysis of objective biomolecular disease patterns has not found its way into everyday wound management. The aim of this study is to evaluate the use of wound swab samples for the analysis of biomarkers and disease patterns in people with chronic wounds. Methods: A sample cohort from the multicenter "Wound-BIOME" project was analyzed. The project aims to comprehensively investigate the local micro-environment of chronic wounds of various entities, healing tendencies and regeneration stages at the biomolecular level. A sample collection and handling protocol suitable for everyday use was tested and evaluated regarding feasibility for multiplex immunoassay, proteomics, small RNA sequencing (miRNA) and metagenome analyses (microbiomics). Results: It could be shown that standard wound swabs are well-suited for the analysis of the complex wound micro-environment using various high-throughput methods. Despite the sample heterogeneity, the quality was adequate to analyze biomolecular patterns. Conclusions: Initial analyses of protein signatures, microbial wound communities and miRNA patterns show promising results for future individualized diagnostics and targeted interventions.

Inhibition of Enzyme and Bacteria Activities in Diabetic Ulcer-like Scenarios via WAAPV-Loaded Electrospun Fibers

In diabetic ulcers, an increased secretion of human neutrophil elastase (HNE) and bacterial infections play crucial roles in hindering healing. Considering that, the present study proposed the development of multi-action polycaprolactone (PCL)/polyethylene glycol (PEG) electrospun fibers incorporating elastase-targeting peptides, AAPV and WAAPV, via blending. Characterization confirmed WAAPV's efficacy in regulating proteolytic enzymes by inhibiting HNE. The engineered fibers, particularly those containing PEG, exhibited optimal wettability but an accelerated degradation that was mitigated with the peptide's inclusion, thus promoting a sustained peptide release over 24 h. Peptide loading was verified indirectly through thermal stability and hydration capacity studies (hydrophobic bonding between PCL and WAAPV and hydrophilic affinities between PCL/PEG and AAPV) and determined at ≈51.1 µg/cm2 and ≈46.0 µg/cm2 for AAPV and ≈48.5 µg/cm2 and ≈51.3 µg/cm2 for WAAPV, respectively, for PCL and PCL/PEG. Both AAPV and WAAPV effectively inhibited HNE, with PEG potentially enhancing this effect by interacting with the peptides and generating detectable peptide-PEG complexes (≈10% inhibition with PCL + peptide fibers after 6 h of incubation, and ≈20% with PCL/PEG + peptide fibers after 4 h incubation). Peptide-loaded fibers demonstrated antibacterial efficacy against Staphylococcus aureus (up to ≈78% inhibition) and Escherichia coli (up to ≈66% inhibition), with peak effectiveness observed after 4 and 2 h of incubation, respectively. This study provides initial insights into the WAAPV's potential for inhibiting HNE and bacteria activities, showing promise for applications in diabetic ulcer management.

Topical Application of Autologous Plasma-Derived Plasminogen Accelerates Healing of Chronic Foot Ulcers in Type 2 Diabetes Patients

Plasminogen (Pg) is currently considered a master regulator of wound healing, but the molecular mechanisms of its efficacy in improving impaired closure of chronic skin ulcers in type 2 diabetes patients remain unclear. Here, we investigated wound healing effects of autologous plasma-derived Pg in diabetes patients with chronic foot ulcers and evaluated Pg-induced changes in levels of key protein markers related to wound repair. Type 2 diabetes patients with chronic wounds of lower extremities were included in the study and received topical applications of Pg in a dose of 1.0 mg/mL every 2 days during 20 days, in addition to the standard wound management treatment. Patients treated only according to conventional protocol served as a control. Wound closure rates were monitored by digital planimetry of wound areas. Plasminogen supplementary treatment significantly accelerated relative wound closure as compared with diabetes patients from the control group (24 ± 4 days vs 120 ± 17 days, respectively, P < .01). As shown by Western blot, Pg application reduced expression of protein regulators of hypoxia events, angiogenesis, and autophagy such as hypoxia-inducible factor-1α (by 6.3-folds, P < .01), angiostatins (by 2.5-folds, P < .05), and autophagy marker LC3-II/LC3-I (by 8.6-folds, P < .05), while increasing vascular endothelial growth factor level by 1.9-folds (P < .05). Gelatin zymography showed that Pg-supplemented therapy decreased activity of matrix metalloproteinase-9 (MMP-9) by 3.5-folds at the end of treatment period (P < .01). We report here for the first time that topically applied plasma-derived Pg has a pronounced beneficial effect in promoting foot ulcer healing in patients with type 2 diabetes through preventing hypoxia-induced signaling, reducing autophagy flux, diminishing excessive MMP activity, and enhancing angiogenesis.

Emerging roles of lactate in acute and chronic inflammation

Traditionally, lactate has been considered a 'waste product' of cellular metabolism. Recent findings have shown that lactate is a substance that plays an indispensable role in various physiological cellular functions and contributes to energy metabolism and signal transduction during immune and inflammatory responses. The discovery of lactylation further revealed the role of lactate in regulating inflammatory processes. In this review, we comprehensively summarize the paradoxical characteristics of lactate metabolism in the inflammatory microenvironment and highlight the pivotal roles of lactate homeostasis, the lactate shuttle, and lactylation ('lactate clock') in acute and chronic inflammatory responses from a molecular perspective. We especially focused on lactate and lactate receptors with either proinflammatory or anti-inflammatory effects on complex molecular biological signalling pathways and investigated the dynamic changes in inflammatory immune cells in the lactate-related inflammatory microenvironment. Moreover, we reviewed progress on the use of lactate as a therapeutic target for regulating the inflammatory response, which may provide a new perspective for treating inflammation-related diseases.

Human keratin matrices promote wound healing by modulating skin cell expression of cytokines and growth factors

A wide variety of biomaterials has been developed to assist in wound healing, including acellular animal and human-derived protein matrices. However, millions of patients worldwide still suffer from non-healing chronic wounds, demonstrating a need for further innovation in wound care. To address this need, a novel biomaterial, the human keratin matrix (HKM), was developed, characterised, and tested in vitro and in vivo. HKM was found to be degradation-resistant, and a proteomics analysis showed it to be greater than 99% human keratin proteins. PCR revealed adult human epidermal keratinocytes (HEKa) grown in contact with HKM showed increased gene expression of keratinocyte activations markers such as Epidermal Growth Factor (EGF). Additionally, a cytokine microarray demonstrated culture on HKM increased the release of cytokines involved in wound inflammatory modulation by both HEKa cells and adult human dermal fibroblasts (HDFa). Finally, in a murine chronic wound model, full-thickness wounds treated weekly with HKM were smaller through the healing process than those treated with human amniotic membrane (AM), bovine dermis (BD), or porcine decellularized small intestinal submucosa (SIS). HKM-treated wounds also closed significantly faster than AM- and SIS-treated wounds. These data suggest that HKM is an effective novel treatment for chronic wounds.

A pH/enzyme dual responsive PMB spatiotemporal release hydrogel promoting chronic wound repair

Suppressing persistent multidrug-resistant (MDR) bacterial infections and excessive inflammation is the key for treating chronic wounds. Therefore, developing a microenvironment-responsive material with good biodegradability, drug-loading, anti-infection, and anti-inflammatory properties is desired to boost the chronic wounds healing process; however, using ordinary assembly remains a defect. Herein, we propose a pH/enzyme dual-responsive polymyxin B (PMB) spatiotemporal-release hydrogel (GelMA/OSSA/PMB), namely, the amount of OSSA and PMB released from GelMA/OSSA/PMB was closely related the wound pH and the enzyme concentration changing. The GelMA/OSSA/PMB showed better biosafety than equivalent free PMB, owing to the controlled release of PMB, which helped kill planktonic bacteria and inhibit biofilm activity in vitro. In addition, the GelMA/OSSA/PMB exhibited excellent antibacterial and anti-inflammatory properties. A MDR Pseudomonas aeruginosa caused infection was effectively resolved by the GelMA/OSSA/PMB hydrogel in vivo, thereby significantly boosting wound closure during the inflammatory phase. Furthermore, GelMA/OSSA/PMB accelerated the sequential phases of wound repair.

Adipose-Derived Stromal Cells for Chronic Wounds: Scientific Evidence and Roadmap Toward Clinical Practice

Chronic wounds, ie, non-healing ulcers, have a prevalence of ~1% in the general population. Chronic wounds strongly affect the quality of life and generate considerable medical costs. A fraction of chronic wounds will heal within months of appropriate treatment; however, a significant fraction of patients will develop therapy-refractory chronic wounds, leading to chronic pain, infection, and amputation. Given the paucity of therapeutic options for refractory wounds, cell therapy and in particular the use of adipose-derived stromal cells (ASC) has emerged as a promising concept. ASC can be used as autologous or allogeneic cells. They can be delivered in suspension or in 3D cultures within scaffolds. ASC can be used without further processing (stromal vascular fraction of the adipose tissue) or can be expanded in vitro. ASC-derived non-cellular components, such as conditioned media or exosomes, have also been investigated. Many in vitro and preclinical studies in animals have demonstrated the ASC efficacy on wounds. ASC efficiency appears to occurs mainly through their regenerative secretome. Hitherto, the majority of clinical trials focused mainly on safety issues. However more recently, a small number of randomized, well-controlled trials provided first convincing evidences for a clinical efficacy of ASC-based chronic wound therapies in humans. This brief review summarizes the current knowledge on the mechanism of action, delivery and efficacy of ASC in chronic wound therapy. It also discusses the scientific and pharmaceutical challenges to be solved before ASC-based wound therapy enters clinical reality.

Biomarkers of Skin Graft Healing in Venous Leg Ulcers

There is a need for biomarkers that predict the success of transplantation of venous leg ulcers (with autologous split-thickness skin grafts). The primary objective of this exploratory study was to investigate the association between split-thickness skin graft healing in venous leg ulcers and candidate wound fluid biomarkers representing inflammatory cell and endogenous proteinase activities, and bioactivity. A secondary objective was to compare biomarker levels of the 17 venous leg ulcers with sterile split-thickness skin graft donor-site wounds in another 10 patients with venous leg ulcers. Wound fluids were collected for 24 h using a validated method. The concentration of pre-operative matrix metalloproteinase-9 in wound fluid was higher in venous leg ulcers showing good healing (n = 10) than in venous leg ulcers showing poor healing (n = 7) 12 weeks after transplantation with meshed split-thickness skin grafts. The diagnostic value of matrix metalloproteinase-9 was good according to receiver-operating characteristic curve analysis. Matrix metalloproteinase activity in wound fluids from split-thickness skin graft donor-site wounds increased as a function of time and healing, but was still lower than matrix metalloproteinase activity in venous leg ulcer wound fluids, which showed increased levels of most biomarkers except for matrix metalloproteinase-9 and matrix metalloproteinase-2. In conclusion, wound fluid matrix metalloproteinase-9 concentration is a potential predictive biomarker of split-thickness skin graft healing in venous leg ulcers.

Nitrosylation of Tissue Transglutaminase enhances fibroblast migration and regulates MMP activation

In wound healing, the TG2 enzyme plays a dual functional role. TG2 has been shown to regulate extracellular matrix (ECM) stabilization by its transamidase activity while increasing cell migration by acting as a cell adhesion molecule. In this process, nitric oxide (NO) plays a particularly important role by nitrosylation of free cysteine ​​residues on TG2, leading to the irreversible inactivation of the catalytic activity. In this study, transfected fibroblasts expressing TG2 under the control of the tetracycline-off promoter were treated with NO donor s-nitroso-n-acetyl penicillamine (SNAP) to analyze the interplay between NO and TG2 in the regulation of cell migration/invasion as well as TGF-β1-dependent MMP activation. Our results demonstrated that inhibition of TG2 cross-linking activity by SNAP promoted the migration and invasion capacity of fibroblasts by hindering TG2-mediated TGF-β1 activation. While the inhibition of TG2 activity by NO downregulated the biosynthesis and activity of MMP-2 and MMP-9, that of MMP-1a and MMP-13 shown to be upregulated in a TGF-β1-dependent manner under the same conditions. In the presence of SNAP, interaction of TG2 with its cell surface binding partners Integrin-β1 and Syndecan-4 was reduced, which was paralleled by an increase in TG2 and PDGF association. These findings suggests that migratory phenotype of fibroblasts can be regulated by the interplay between nitric oxide and TG2 activity.

Resveratrol inhibits matrix metalloproteinase-1 and -3 expression by suppressing of p300/NFκB acetylation in TNF-α-treated human dermal fibroblasts

The aim of this study was to explore the signaling pathways associated with the effects of tumor necrosis factor alpha (TNF-α) on matrix metalloproteinase-1 (MMP-1) and MMP-3 expression in the human dermal fibroblast cell line CCD-966SK. TNF-α upregulated MMP-1 and MMP-3 mRNA and protein expression, and NFκB/p65 activation was found to be involved in TNF-α-induced MMP-1 and MMP-3 upregulation. TNF-α induced p65 phosphorylation at Ser536 and acetylation at Lys310. p300 knockdown suppressed TNF-α-induced p65 acetylation and reduced MMP-1 and MMP-3 expression in TNF-α-treated cells, but did not greatly restore MMP-1 and MMP-3 expression when p65 phosphorylation was inhibited by Bay11-7082 (IκBα inhibitor). NF-κB/luciferase reporter assay revealed that p300-mediated p65 acetylation was crucial for TNF-α-induced nuclear factor-kappa B (NF-κB) transcriptional activity. The chromatin immunoprecipitation (ChIP) assay indicated that TNF-α increased p300 recruitment to the MMP-1 and MMP-3 promoter regions surrounding the NFκB-binding site. Resveratrol notably inhibited TNF-α-induced MMP-1 and MMP-3 upregulation and abrogated TNF-α-induced p65 acetylation, leading to the downregulation of MMP-1 and MMP-3 expression in TNF-α-treated cells. Our data indicate that TNF-α-induced p300-mediated p65 acetylation leads to the upregulation of MMP-1 and MMP-3 expression in dermal fibroblasts, whereas resveratrol reduces this TNF-α-induced upregulation by downregulating p300 expression.