The effects of advanced glycation end products (AGEs) on dermal wound healing and scar formation: a systematic review

The potential role of Hypericum perforatum in wound healing: A literature review on the phytochemicals, pharmacological approaches, and mechanistic perspectives

St. John's Wort, commonly known as Hypericum perforatum L., is a flowering plant in the Clusiaceae family that traditionally been employed for treating anxiety, depression, wounds, burns, sunburn, irritation, and stomach ailments. This review provides a synopsis of H. perforatum L. phytoconstituents and their biological effects, highlighting its beneficial therapeutic properties for dermatological indications, as well as its antioxidant, antimicrobial, anti-inflammatory, and anti-angiogenic activity in various applications including wound healing and skin conditions such as eczema, sun burn and minor burns also spastic paralysis, stiff neck and mood disorders as anti-depressant and nerve pains such as neuralgia. The data were collected from several databases as Web of Science PubMed, ScienceDirect, Scopus and Google Scholar using the terms: "H. perforatum L.", "H. perforatum L. /phytochemistry," and "H. perforatum extracts/wound healing" collected from 1994 to 2023. The findings suggest H. perforatum L. acts through various mechanisms and plays a role in each phase of the wound healing process, including re-epithelialization, angiogenesis, wound contraction, and connective tissue regeneration. H. perforatum L. enhances collagen deposition, decreases inflammation, inhibits fibroblast migration, and promotes epithelialization by increasing the number of fibroblasts with polygonal shape and the number of collagen fibers within fibroblasts. H. Perforatum L. extracts modulate the immune response and reduce inflammation were found to accelerate the wound healing process via inhibition of inflammatory mediators' production like interleukin-6, tumor necrosis factor-α, cyclooxygenase-2 gene expression, and inducible nitric oxide synthase. Thus, H. perforatum L. represents a potential remedy for a wide range of dermatological problems, owing to its constituents with beneficial therapeutic properties. H. perforatum L. could be utilized in the development of novel wound healing therapies.

Advanced glycation end products of dietary origin and their association with inflammation in diabetes - A minireview

Advanced glycation end products (AGEs) are a diverse group of compounds that are formed as a result of the non-enzymatic reaction between a reducing sugar such as glucose and the free NH2 groups of an amino acid in a protein or other biomolecule. The chemical reaction, by which these products are generated, is known as the Maillard reaction and occurs as a part of the body's normal metabolism. Such a reaction is enhanced during diabetes due to hyperglycemia, but it can also occur during the preparation, processing, and preservation of certain foods. Therefore, AGEs can also be obtained from the diet (d-AGE) and contribute to an increase of the total serum pool of these compounds. They have been implicated in a wide variety of pathological processes, mainly because of their ability to induce inflammatory responses and oxidative stress increase. They are extensively accumulated as a part of the normal aging, especially in tissues rich in long half-life proteins, which can compromise the physiology of these tissues. d-AGEs are abundant in diets rich in processed fats and sugars. This review is addressed to the current knowledge on these products and their impact on the immunomodulation of various mechanisms that may contribute to exacerbation of the diabetes pathophysiology.

Serum sRAGE levels in children with atopic dermatitis: a prospective study

Introduction

Atopic dermatitis (AD) is chronic inflammatory skin disorder. The receptor for advanced glycation end products (RAGE) plays a role in inflammatory reactions. The soluble form of RAGE (sRAGE) acts as a decoy to inhibit interactions of RAGE.

Aim

To determine serum sRAGE levels in children with AD.

Material and methods

AD diagnosis was made according to Hanifin and Rajka criteria. Disease severity was scored by the scoring atopic dermatitis (SCORAD) index. Skin prick testing (SPT), total immunoglobulin E (Ig E) and eosinophil counts were analysed. The sRAGE levels were determined using ELISA technique.

Results

The children, aged 0.4 to 2.0 years with AD (n = 65) were investigated in two groups according to the presence (AD+/Atopy+ [n = 40]) or absence (AD+/Atopy- [n = 25]) of SPT positivity. The comparisons were made with a healthy control group matched for age and sex. The medians (interquartile range) of sRAGE levels in patient and control groups were 8.43 (1.04-18.37) and 14.09 (6.35-28.64), respectively (p < 0.001). The medians (interquartile range) of sRAGE levels in AD+/Atopy+, AD+/Atopy- and control groups were 8.5 (3.1-17.27), 7.75 (1.04-18.37) and 14.09 (6.35-28.64), respectively (p = 0.004). Correlation analysis failed to reach significance with the disease severity sRAGE levels, total IgE levels and eosinophil counts.

Conclusions

To our knowledge, this is the first study investigating the association of sRAGE levels with AD and disease severity in childhood. Serum sRAGE levels are decreased in AD but not correlated with disease severity. sRAGE levels may be important in the AD disease process.

Novel approaches to target fibroblast mechanotransduction in fibroproliferative diseases

The ability of cells to sense and respond to changes in mechanical environment is vital in conditions of organ injury when the architecture of normal tissues is disturbed or lost. Among the various cellular players that respond to injury, fibroblasts take center stage in re-establishing tissue integrity by secreting and organizing extracellular matrix into stabilizing scar tissue. Activation, activity, survival, and death of scar-forming fibroblasts are tightly controlled by mechanical environment and proper mechanotransduction ensures that fibroblast activities cease after completion of the tissue repair process. Conversely, dysregulated mechanotransduction often results in fibroblast over-activation or persistence beyond the state of normal repair. The resulting pathological accumulation of extracellular matrix is called fibrosis, a condition that has been associated with over 40% of all deaths in the industrialized countries. Consequently, elements in fibroblast mechanotransduction are scrutinized for their suitability as anti-fibrotic therapeutic targets. We review the current knowledge on mechanically relevant factors in the fibroblast extracellular environment, cell-matrix and cell-cell adhesion structures, stretch-activated membrane channels, stress-regulated cytoskeletal structures, and co-transcription factors. We critically discuss the targetability of these elements in therapeutic approaches and their progress in pre-clinical and/or clinical trials to treat organ fibrosis.

Cutaneous changes in diabetic patients: Primed for aberrant healing?

Cutaneous manifestations affect most patients with diabetes mellitus, clinically presenting with numerous dermatologic diseases from xerosis to diabetic foot ulcers (DFUs). Skin conditions not only impose a significantly impaired quality of life on individuals with diabetes but also predispose patients to further complications. Knowledge of cutaneous biology and the wound healing process under diabetic conditions is largely limited to animal models, and studies focusing on biology of the human condition of DFUs remain limited. In this review, we discuss the critical molecular, cellular, and structural changes to the skin in the hyperglycaemic and insulin-resistant environment of diabetes with a focus specifically on human-derived data. Elucidating the breadth of the cutaneous manifestations coupled with effective diabetes management is important for improving patient quality of life and averting future complications including wound healing disorders.

Enzymatic Deglycation of Damaged Skin by Means of Combined Treatment of Fructosamine-3-Kinase and Fructosyl-Amino Acid Oxidase

The consensus in aging is that inflammation, cellular senescence, free radicals, and epigenetics are contributing factors. Skin glycation through advanced glycation end products (AGEs) has a crucial role in aging. Additionally, it has been suggested that their presence in scars leads to elasticity loss. This manuscript reports fructosamine-3-kinase (FN3K) and fructosyl-amino acid oxidase (FAOD) in counteracting skin glycation by AGEs. Skin specimens were obtained (n = 19) and incubated with glycolaldehyde (GA) for AGE induction. FN3K and FAOD were used as monotherapy or combination therapy. Negative and positive controls were treated with phosphate-buffered saline and aminoguanidine, respectively. Autofluorescence (AF) was used to measure deglycation. An excised hypertrophic scar tissue (HTS) (n = 1) was treated. Changes in chemical bonds and elasticity were evaluated using mid-infrared spectroscopy (MIR) and skin elongation, respectively. Specimens treated with FN3K and FAOD in monotherapy achieved an average decrease of 31% and 33% in AF values, respectively. When treatments were combined, a decrease of 43% was achieved. The positive control decreased by 28%, whilst the negative control showed no difference. Elongation testing of HTS showed a significant elasticity improvement after FN3K treatment. ATR-IR spectra demonstrated differences in chemical bounds pre- versus post-treatment. FN3K and FAOD can achieve deglycation and the effects are most optimal when combined in one treatment.

Impact of elevated serum advanced glycation end products and exercise on intact and injured murine tendons

OVERVIEW

Delayed tendon healing is a significant clinical challenge for those with diabetes. We explored the role of advanced glycation end-products (AGEs), a protein modification present at elevated levels in serum of individuals with diabetes, on injured and intact tendons using a mouse model. Cell proliferation following tissue injury is a vital component of healing. Based on our previous work demonstrating that AGEs limit cell proliferation, we proposed that AGEs are responsible for the delayed healing process commonly observed in diabetic patients. Further, in pursuit of interventional strategies, we suggested that moderate treadmill exercise may support a healing environment in the presence of AGEs as exercise has been shown to stimulate cell proliferation in tendon tissue.

MATERIALS AND METHODS

Mice began receiving daily intraperitoneal injections of bovine serum albumin (BSA)-Control or AGE-BSA injections (200μg/ml) at 16-weeks of age. A tendon injury was created in the central third of both patellar tendons. Animals assigned to an exercise group began a moderate treadmill protocol one week following injury. The intact Achilles tendon and soleus muscle were also evaluated to assess the effect of BSA and AGE-BSA on un-injured muscle and tendon.

RESULTS

We demonstrate that our injection dosing and schedule lead to an increase in serum AGEs. Our findings imply that AGEs indeed modulate gene expression following a patellar tendon injury and have modest effects on gene expression in intact muscle and tendon.

CONCLUSIONS

While additional biomechanical analysis is warranted, these data suggest that elevated serum AGEs in persons with diabetes may impact tendon health.

Blocking RAGE improves wound healing in diabetic pigs

Receptor for Advanced Glycated End-products (RAGE) is highly expressed in diabetes and impairs wound healing. We proposed that administering an antibody that blocks RAGE will hasten the healing of dorsal wounds in diabetic pigs compared with a non-immune IgG. Two purpose-bred diabetic (D) Yucatan minipigs (Sinclair, Auxvasse MO) each underwent 12 2 × 2 cm full thickness dorsal wounds: four wounds received decellularized porcine skin patches (Xylyx Bio, Bklyn NY): four anti-RAGE Ab (CR-3) infused patches, four saline infused patches and four wounds were left open. One pig received anti-RAGE Ab (CR-3) 1 mg/kg IM q 10 days and other received non-immune IgG. Wounds were measured at 2 and 4 weeks followed by euthanasia and wound harvesting. At 2 weeks few of the patches appeared to be incorporated into the wound. By 4 weeks all patches in pigs treated systemically with CR-3 were detached and the wounds almost healed. For all 24 wounds for both pigs regardless of presence of patch or type of patch, the average IgG treated pig wound size at 4 weeks was 69.2 ± 14.6% of initial size and the average CR-3 treated pig wound size was 40.9 ± 11.3% of initial size (P = 0.0002). Quantitative immunohistology showed greater staining for collagen in the CR-3 treated wounds compared with IgG treated. Staining was positive for RAGE, Mac, and IL-6 in the IgG treated wounds and negative in the CR-3 treated wounds. From these pilot experiments, we conclude that a RAGE blocking antibody given parenterally improved wound healing in a diabetic pig while patches were not effective.

Advanced Glycation End Products and Activation of Toll-like Receptor-2 and -4 Induced Changes in Aquaporin-3 Expression in Mouse Keratinocytes

Prolonged inflammation and impaired re-epithelization are major contributing factors to chronic non-healing diabetic wounds; diabetes is also characterized by xerosis. Advanced glycation end products (AGEs), and the activation of toll-like receptors (TLRs), can trigger inflammatory responses. Aquaporin-3 (AQP3) plays essential roles in keratinocyte function and skin wound re-epithelialization/re-generation and hydration. Suberanilohydroxamic acid (SAHA), a histone deacetylase inhibitor, mimics the increased acetylation observed in diabetes. We investigated the effects of TLR2/TLR4 activators and AGEs on keratinocyte AQP3 expression in the presence and absence of SAHA. Primary mouse keratinocytes were treated with or without TLR2 agonist Pam₃Cys-Ser-(Lys)₄ (PAM), TLR4 agonist lipopolysaccharide (LPS), or AGEs, with or without SAHA. We found that (1) PAM and LPS significantly upregulated AQP3 protein basally (without SAHA) and PAM downregulated AQP3 protein with SAHA; and (2) AGEs (100 µg/mL) increased AQP3 protein expression basally and decreased AQP3 levels with SAHA. PAM and AGEs produced similar changes in AQP3 expression, suggesting a common pathway or potential crosstalk between TLR2 and AGEs signaling. Our findings suggest that TLR2 activation and AGEs may be beneficial for wound healing and skin hydration under normal conditions via AQP3 upregulation, but that these pathways are likely deleterious in diabetes chronically through decreased AQP3 expression.

Modulation of the biophysical and biochemical properties of collagen by glycation for tissue engineering applications

The structural and functional properties of collagen are modulated by the presence of intramolecular and intermolecular crosslinks. Advanced Glycation End-products (AGEs) can produce intermolecular crosslinks by bonding the free amino groups of neighbouring proteins. In this research, the following hypothesis is explored: The accumulation of AGEs in collagen decreases its proteolytic degradation rates while increasing its stiffness. Fluorescence Lifetime Imaging (FLIM) and Fourier-transform infrared spectroscopy (FTIR) detect biochemical changes in collagen scaffolds during the glycation process. The accumulation of AGEs increases exponentially in the collagen scaffolds as a function of Methylglyoxal (MGO) concentration by performing autofluorescence measurement and competitive ELISA. Glycated scaffolds absorb water at a much higher rate confirming the direct affinity between AGEs and interstitial water within collagen fibrils. In addition, the topology of collagen fibrils as observed by Atomic Force Microscopy (AFM) is a lot more defined following glycation. The elastic modulus of collagen fibrils decreases as a function of glycation, whereas the elastic modulus of collagen scaffolds increases. Finally, the enzymatic degradation of collagen by bacterial collagenase shows a sigmoidal pattern with a much slower degradation rate in the glycated scaffolds. This study identifies unique variations in the properties of collagen following the accumulation of AGEs. STATEMENT OF SIGNIFICANCE: In humans, Advanced Glycation End-products (AGEs) are naturally produced as a result of aging process. There is an evident lack of knowledge in the basic science literature explaining the biomechanical impact of AGE-mediated crosslinks on the functional and structural properties of collagen at both the nanoscale (single fibrils) and mesoscale (bundles of fibrils). This research, demonstrates how it is possible to harness this natural phenomenon in vitro to enhance the properties of engineered collagen fibrils and scaffolds. This study identifies unique variations in the properties of collagen at nanoscale and mesoscale following accumulation of AGEs. In their approach, they investigate the unique properties conferred to collagen, namely enhanced water sorption, differential elastic modulus, and finally sigmoidal proteolytic degradation behavior.

Research Advances on the Damage Mechanism of Skin Glycation and Related Inhibitors

Our skin is an organ with the largest contact area between the human body and the external environment. Skin aging is affected directly by both endogenous factors and exogenous factors (e.g., UV exposure). Skin saccharification, a non-enzymatic reaction between proteins, e.g., dermal collagen and naturally occurring reducing sugars, is one of the basic root causes of endogenous skin aging. During the reaction, a series of complicated glycation products produced at different reaction stages and pathways are usually collectively referred to as advanced glycation end products (AGEs). AGEs cause cellular dysfunction through the modification of intracellular molecules and accumulate in tissues with aging. AGEs are also associated with a variety of age-related diseases, such as diabetes, cardiovascular disease, renal failure (uremia), and Alzheimer's disease. AGEs accumulate in the skin with age and are amplified through exogenous factors, e.g., ultraviolet radiation, resulting in wrinkles, loss of elasticity, dull yellowing, and other skin problems. This article focuses on the damage mechanism of glucose and its glycation products on the skin by summarizing the biochemical characteristics, compositions, as well as processes of the production and elimination of AGEs. One of the important parts of this article would be to summarize the current AGEs inhibitors to gain insight into the anti-glycation mechanism of the skin and the development of promising natural products with anti-glycation effects.

Enhanced Diabetic Wound Healing Using Electrospun Biocompatible PLGA-Based Saxagliptin Fibrous Membranes

Delayed diabetic wound healing is an adverse event that frequently leads to limb disability or loss. A novel and promising vehicle for the treatment of diabetic wounds is required for clinical purposes. The biocompatible and resorbable poly (lactic-co-glycolic acid) (PLGA)-based fibrous membranes prepared by electrospinning that provide a sustained discharge of saxagliptin for diabetic wound healing were fabricated. The concentration of released saxagliptin in Dulbecco’s phosphate-buffered saline was analyzed for 30 days using high-performance liquid chromatography. The effectiveness of the eluted saxagliptin was identified using an endothelial progenitor cell migration assay in vitro and a diabetic wound healing in vivo. Greater hydrophilicity and water storage were shown in the saxagliptin-incorporated PLGA membranes than in the pristine PLGA membranes (both p < 0.001). For diabetic wound healing, the saxagliptin membranes accelerated the wound closure rate, the dermal thickness, and the heme oxygenase-1 level over the follicle areas compared to those in the pristine PLGA group at two weeks post-treatment. The saxagliptin group also had remarkably higher expressions of insulin-like growth factor I expression and transforming growth factor-β1 than the control group (p = 0.009 and p < 0.001, respectively) in diabetic wounds after treatment. The electrospun PLGA-based saxagliptin membranes exhibited excellent biomechanical and biological features that enhanced diabetic wound closure and increased the antioxidant activity, cellular granulation, and functionality.

Effects of cheerleading practice on advanced glycation end products, areal bone mineral density, and physical fitness in female adolescents

Background: Exercise has been widely reported to promote bone health, but it is unknown whether is associated with a reduction in advanced glycosylation end products (AGEs). This study aimed to investigate the effects of 14 weeks of cheerleading exercise on areal bone mineral density (aBMD) and AGEs.

Methods: In this study, 46 female teenagers (age, 19.52 ± 1.21 years; body mass index, 20.15 ± 2.47 kg/m²) were randomly divided into a cheerleading group (CHE, n = 21) and a control group (CON, n = 25). The CHE group was subjected to cheerleading practice twice a week for 14 weeks; the CON group maintained their daily routine. Dual-energy X-ray absorptiometry was used to measure aBMD, and autofluorescence (AF) values were used to reflect AGEs. Physical fitness testing all-in-one machines are used to test body composition, cardiorespiratory fitness, muscle fitness and flexibility. A mixed ANOVA model was used to examine the effect of the intervention on each outcome. A multiple mediation model with covariates for physical activity and eating behaviors was performed to explore the mediators between cheerleading exercise and aBMD.

Results: After 14 weeks of cheerleading practice, 1) aBMD increased significantly in both groups with significantly higher increases in the CHE group (p < 0.05). 2) AGEs significantly decreased in the CHE group (−2.7%), but not in the CON group (p > 0.05). 3) Vertical jumps and sit-ups significantly increased in the CHE group (p < 0.05), but not in the CON group (p > 0.05). 4) ΔAF values was significantly negatively correlated with Δ aBMD (r = −0.302, p < 0.05). 5) ΔAF values mediated the effect of exercise on the aBMD (indirect effect: 0.0032, 95% CI 0.0002–0.0079).

Conclusion: Cheerleading practice improved aBMD and physical fitness and reduced AGEs accumulation in female adolescents. The effect of exercise on aBMD was partially mediated by AGEs.

An inducible model for unraveling the effects of advanced glycation end-product accumulation in aging connective tissues

PURPOSE

In connective tissues there is a clear link between increasing age and degeneration. Advanced glycation end-products (AGEs) are believed to play a central role. AGEs are sugar-induced non-enzymatic crosslinks which accumulate in collagen with age and diabetes, altering tissue mechanics and cellular function. Despite ample correlative evidence linking collagen glycation to tissue degeneration, little is known how AGEs impact cell-matrix interactions, limiting therapeutic options. One reason for this limited understanding is that AGEs are typically induced using high concentrations of ribose which decrease cell viability, making it impossible to investigate cell-matrix interactions. The objective of this study was to develop a system to trigger AGE accumulation while maintaining cell viability.

MATERIALS AND METHODS

Using cell-seeded high density collagen gels, we investigated the effect of two systems for AGE induction, ribose at low concentrations (30, 100, and 200 mM) over 15 days of culture and riboflavin (0.25 and 0.75 mM) induced with blue light for 40 seconds (riboflavin-465 nm).

RESULTS

We found ribose and riboflavin-465 nm treatment produces fluorescent AGE quantities which match and/or exceed human fluorescent AGE levels for various tissues, ages, and diseases, without affecting cell viability or metabolism. Interestingly, a 40 second treatment of riboflavin-465 nm produced similar levels of fluorescent AGEs as 3 days of 100 mM ribose treatment.

CONCLUSIONS

Riboflavin-465 nm is a promising method to trigger AGEs on demand in vivo or in vitro without impacting cell viability and offers potential for unraveling the mechanism of AGEs in age and diabetes related tissue damage.

Advanced Glycation End-Products (AGEs): Formation, Chemistry, Classification, Receptors, and Diseases Related to AGEs

Advanced glycation end-products (AGEs) constitute a non-homogenous, chemically diverse group of compounds formed either exogeneously or endogeneously on the course of various pathways in the human body. In general, they are formed non-enzymatically by condensation between carbonyl groups of reducing sugars and free amine groups of nucleic acids, proteins, or lipids, followed by further rearrangements yielding stable, irreversible end-products. In the last decades, AGEs have aroused the interest of the scientific community due to the increasing evidence of their involvement in many pathophysiological processes and diseases, such as diabetes, cancer, cardiovascular, neurodegenerative diseases, and even infection with the SARS-CoV-2 virus. They are recognized by several cellular receptors and trigger many signaling pathways related to inflammation and oxidative stress. Despite many experimental research outcomes published recently, the complexity of their engagement in human physiology and pathophysiological states requires further elucidation. This review focuses on the receptors of AGEs, especially on the structural aspects of receptor-ligand interaction, and the diseases in which AGEs are involved. It also aims to present AGE classification in subgroups and to describe the basic processes leading to both exogeneous and endogeneous AGE formation.

Polysaccharide-Based Membrane Biocompatibility Study of Anacardium occidentale L. and Polyvinyl Alcohol after Subcutaneous Implant in Rats

Polymeric membranes are a viable and sustainable option for the biotechnology industry from an economic and environmental point of view. In this study, we evaluated tissue response and tolerance to the implantation of a polymeric membrane prepared with cashew gum polysaccharide (CGP) associated with polyvinyl alcohol (PVA). The objective was to characterize the biocompatibility of the CGP/PVA membrane in vivo. Following the evaluation criteria of the ISO 10993-6 standard, we demonstrated that the CGP/PVA membrane showed moderate tissue reaction, with a non-irritating ISO pattern, a thinner fibrous capsule, and a smaller amount of collagen compared to the positive control group. At 30 and 60 days, the membrane presented a similar amount of mast cells to that observed in the negative control group. The data demonstrate that the CGP/PVA membrane presents biocompatibility in accordance with the ISO 10993-6 standard.

Piper crocatum Ruiz & Pav. ameliorates wound healing through p53, E-cadherin and SOD1 pathways on wounded hyperglycemia fibroblasts

INTRODUCTION

Piper crocatum Ruiz & Pav (P. crocatum) has been reported to accelerate the diabetic wound healing process empirically. Some studies showed the benefits of P. crocatum in treating various diseases but its mechanisms in diabetic wound healing have never been reported. In the present study we investigated the diabetic wound healing activity of the active fraction of P. crocatum on wounded hyperglycemia fibroblasts (wHFs).

METHODS

Bioassay-guided fractionation was performed to get the most active fraction. The selected active fraction was applied to wHFs within 72 h incubation. Mimicking a diabetic condition was done using basal glucose media containing an additional 17 mMol/L D-glucose. A wound was simulated via the scratch assay. The collagen deposition was measured using Picro-Sirius Red and wound closure was measured using scratch wound assay. Underlying mechanisms through p53, αSMA, SOD1 and E-cadherin were measured using western blotting.

RESULTS

We reported that FIV is the most active fraction of P. crocatum. We confirmed that FIV \(7.81 µg/ml, 15.62 µg/ml, 31.25 µg/ml, 62.5 µg/ml, and 125 µg/ml) induced the collagen deposition and wound closure of wHFs. Furthermore, FIV treatment (7.81 µg/ml, 15.62 µg/ml, 31.25 µg/ml) down-regulated the protein expression level of p53 and up-regulated the protein expression levels of αSMA, E-cadherin, and SOD1.

DISCUSSION/CONCLUSIONS

Our findings suggest that ameliorating collagen deposition and wound closure through protein regulation of p53, αSMA, E-cadherin, and SOD1 are some of the mechanisms by which FIV of P. crocatum is involved in diabetic wound healing therapy.

AGE/Non-AGE Glycation: An Important Event in Rheumatoid Arthritis Pathophysiology

Rheumatoid arthritis (RA) is a chronic inflammatory, autoimmune disease that gradually affects the synovial membrane and joints. Many intrinsic and/or extrinsic factors are crucial in making RA pathology challenging throughout the disease. Substantial enzymatic or non-enzymatic modification of proteins driving inflammation has gained a lot of interest in recent years. Endogenously modified glycated protein influences disease development linked with AGEs/non-AGEs and is reported as a disease marker. In this review, we summarized current knowledge of the differential abundance of glycated proteins by compiling and analyzing a variety of AGE and non-AGE ligands that bind with RAGE to activate multi-faceted inflammatory and oxidative stress pathways that are pathobiologically associated with RA-fibroblast-like synoviocytes (RA-FLS). It is critical to comprehend the connection between oxidative stress and inflammation generation, mediated by glycated protein, which may bind to the receptor RAGE, activate downstream pathways, and impart immunogenicity in RA. It is worth noting that AGEs and non-AGEs ligands play a variety of functions, and their functionality is likely to be more reliant on pathogenic states and severity that may serve as biomarkers for RA. Screening and monitoring of these differentially glycated proteins, as well as their stability in circulation, in combination with established pre-clinical characteristics, may aid or predict the onset of RA.

Updates in Diabetic Wound Healing, Inflammation, and Scarring

Diabetic patients can sustain wounds either as a sequelae of their disease process or postoperatively. Wound healing is a complex process that proceeds through phases of inflammation, proliferation, and remodeling. Diabetes results in several pathological changes that impair almost all of these healing processes. Diabetic wounds are often characterized by excessive inflammation and reduced angiogenesis. Due to these changes, diabetic patients are at a higher risk for postoperative wound healing complications. There is significant evidence in the literature that diabetic patients are at a higher risk for increased wound infections, wound dehiscence, and pathological scarring. Factors such as nutritional status and glycemic control also significantly influence diabetic wound outcomes. There are a variety of treatments available for addressing diabetic wounds.

Effect of Advanced Glycation End-Products and Excessive Calorie Intake on Diet-Induced Chronic Low-Grade Inflammation Biomarkers in Murine Models

Chronic Low-Grade Inflammation (CLGI) is a non-overt inflammatory state characterized by a continuous activation of inflammation mediators associated with metabolic diseases. It has been linked to the overconsumption of Advanced Glycation End-Products (AGEs), and/or macronutrients which lead to an increase in local and systemic pro-inflammatory biomarkers in humans and animal models. This review provides a summary of research into biomarkers of diet-induced CLGI in murine models, with a focus on AGEs and obesogenic diets, and presents the physiological effects described in the literature. Diet-induced CLGI is associated with metabolic endotoxemia, and/or gut microbiota remodeling in rodents. The mechanisms identified so far are centered on pro-inflammatory axes such as the interaction between AGEs and their main receptor AGEs (RAGE) or increased levels of lipopolysaccharide. The use of murine models has helped to elucidate the local and systemic expression of CLGI mediators. These models have enabled significant advances in identification of diet-induced CLGI biomarkers and resultant physiological effects. Some limitations on the translational (murine → humans) use of biomarkers may arise, but murine models have greatly facilitated the testing of specific dietary components. However, there remains a lack of information at the whole-organism level of organization, as well as a lack of consensus on the best biomarker for use in CLGI studies and recommendations as to future research conclude this review.

Chitosan alginate nanoparticles as a platform for the treatment of diabetic and non-diabetic pressure ulcers: Formulation and in vitro/in vivo evaluation

Chitosan and alginate are natural bioactive polymers with wound healing properties, in addition to chitosan's anti-bacterial properties. In this study, these two polymers were combined in a drug-free nanosystem with positive or negative surface charges, for the treatment of non-diabetic and diabetic pressure ulcers. Chitosan alginate nanoparticles (CA NPs) were prepared by a modified ionic gelation method. Interaction between the polymers and formation of the NPs were confirmed by Fourier-Transform infrared spectroscopy, differential scanning calorimetry and transmission electron microscopy. For in vivo study, selected CA NPs with optimum particle size, polydispersity index, positive and negative zeta potential, were evaluated for their pressure ulcers-healing effect using non-diabetic and diabetic rats. Rate of wound closure, histological examination and histomorphometric assessment were used to evaluate the CA NPs' wound healing potential. Positively and negatively charged CA NPs significantly enhanced wound closure rates, compared to control untreated group. Histological and histomorphometric analysis revealed higher quality and maturation of the formed granulation tissue, less inflammation and higher collagen content with positively charged CA NPs containing higher amount of chitosan. These results suggest that chitosan alginate nanoparticles offer a promising platform for diabetic and non-diabetic wound healing applications.

Plantar soft tissues and Achilles tendon thickness and stiffness in people with diabetes: a systematic review

BACKGROUND

Diabetes mellitus is associated with changes in soft tissue structure and function. However, the directionality of this change and the extent to which either tissue thickness or stiffness contributes to the pathogenesis of diabetes-related foot ulcerations is unclear. Hence, this systematic review aims to summarise the existing evidence for soft tissue structural differences in the feet of people with and without diabetes.

METHODS

In compliance with MOOSE and PRISMA guidelines, AMED, CINAHL, MEDLINE, ProQuest Health & Medical Collection, ProQuest Nursing & Allied Health Database, and Web of Science electronic databases were systematically searched for studies published from database inception until 1st October 2020 [Prospero CRD42020166614]. Reference lists of included studies were further screened. Methodological quality was appraised using a modified critical appraisal tool for quantitative studies developed by McMaster University.

RESULTS

A total of 35 non-randomised observational studies were suitable for inclusion. Within these, 20 studies evaluated plantar tissue thickness, 19 studies evaluated plantar tissue stiffness, 9 studies evaluated Achilles tendon thickness and 5 studies evaluated Achilles tendon stiffness outcomes. No significant differences in plantar tissue thickness were found between people with and without diabetes in 55% of studies (11/20), while significantly increased plantar tissue stiffness was found in people with diabetes in 47% of studies (9/19). Significantly increased Achilles tendon thickness was found in people with diabetes in 44% of studies (4/9), while no significant differences in Achilles tendon stiffness were found between people with and without diabetes in 60% of studies (3/5).

CONCLUSIONS

This systematic review found some evidence of soft tissue structural differences between people with and without diabetes. However, uncertainty remains whether these differences independently contribute to diabetes-related foot ulcerations. The heterogeneity of methodological approaches made it difficult to compare across studies and methodological quality was generally inadequate. High-quality studies using standardised and validated assessment techniques in well-defined populations are required to determine more fully the role of structural tissue properties in the pathogenesis of diabetes-related foot ulcerations.

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.

Absolute Configuration of Mycosporine-Like Amino Acids, Their Wound Healing Properties and In Vitro Anti-Aging Effects

Mycosporine-like amino acids (MAAs) are water-soluble metabolites, reported to exhibit strong UV-absorbing properties. They have been found in a wide range of marine organisms, especially those that are exposed to extreme levels of sunlight, to protect them against solar radiation. In the present study, the absolute configuration of 14 mycosporine-like-amino acids was determined by combining the results of electronic circular dichroism (ECD) experiments and that of advanced Marfey's method using LC-MS. The crystal structure of a shinorine hydrate was determined from single crystal X-ray diffraction data and its absolute configuration was established from anomalous-dispersion effects. Furthermore, the anti-aging and wound-healing properties of these metabolites were evaluated in three different assays namely the inhibition of collagenase, inhibition of advanced glycation end products (AGEs) and wound healing assay (scratch assay).

When Wounds Are Good for You: The Regenerative Capacity of Fractional Resurfacing and Potential Utility in Chronic Wound Prevention

Significance: Fractional resurfacing involves producing arrays of microinjuries on the skin, by thermal or mechanical means, to trigger tissue regeneration. Originally developed for cosmetic enhancement, fractional resurfacing induces a broad array of improvements in the structural and functional qualities of the treated skin and is especially effective at returning defective skin to a more normal state. In addition to fascinating questions about the nature of this remarkable regenerative capacity, there may be potential utility in ulcer prevention by halting or even reversing the progressive decline in overall skin quality that usually precedes chronic wound development. Recent Advances: Photoaging and scarring are the two skin defects most commonly treated by fractional resurfacing, and the treatment produces profound and long-lasting improvements in skin quality, both clinically and at the cellular/histologic level. Chronic wounds usually occur in skin that is compromised by various pathologic factors, and many of the defects found in this ulcer-prone skin are similar to those that have seen improvements after fractional resurfacing. Critical Issues: The mechanisms responsible for the regenerative capacity of fractional resurfacing are mostly unknown, as is how ulcer-prone skin, which is usually afflicted by stressors external to the skin tissue itself, would respond to fractional resurfacing. Future Directions: Better understanding of the cellular and molecular mechanisms underlying the unique healing response to fractional resurfacing could reveal fundamental information about adult tissue regeneration, lead to improvements in current applications, as well as new therapies in other pathologic conditions.

Increased Rates of Readmission, Reoperation, and Mortality Following Open Reduction and Internal Fixation of Ankle Fractures Are Associated With Diabetes Mellitus

The purpose of this study was to compare the rates of readmission, reoperation, and mortality in patients with and without diabetes mellitus during the 30-day postoperative period after ankle fracture surgery. Patients who underwent operative management for ankle fractures between 2006 and 2015 were identified in the American College of Surgeons National Surgical Quality Improvement Program^® database by using Current Procedural Terminology codes for ankle fracture surgery. A total of 17,464 patients undergoing ankle fracture surgery were identified. Of these patients, 2044 (11.7%) had diabetes and 15,420 (88.3%) did not have diabetes. We excluded patients older than 90 years or with inadequate perioperative data. Patients with diabetes had significantly higher rates of readmission (2.84% vs 1.05%, p < .0001), significantly higher rates of unplanned reoperation (2.3% vs 0.74%, p < .0001), and significantly higher rates of mortality (0.7% vs 0.2%, p < .0001) compared with patients without diabetes. Additionally, patients with diabetes had significantly greater age-adjusted odds ratios (ORs) of unplanned readmission (OR 2.40, 95% confidence interval [CI] 1.74 to 3.31, p < .0001), unplanned reoperation (OR 2.56, 95% CI 1.44 to 3.27, p < .0001), and mortality (OR 2.01, 95% CI 1.08 to 3.62, p = .0432) than did patients without diabetes after ankle surgery. In this large-scale retrospective study, we demonstrated that the presence of diabetes significantly increases the risk of unplanned readmission, unplanned reoperation, and mortality during the 30-day postoperative period after ankle fracture surgery.

Cecropia pachystachya Leaves Present Potential to Be Used as New Ingredient for Antiaging Dermocosmetics

Several biological activities have been reported for leaf extracts of Cecropia pachystachya species, including antioxidant and wound healing activities. This study aims to report, for the first time, the antiaging potential of the hydroethanolic (HE) and the ethanolic (EE) extracts obtained from the leaves of C. pachystachya using different in vitro assays. Both HE and EE presented relevant antioxidant capacity in different models, including phosphomolybdenum, 1,1-diphenyl-2-picryl-hydrazyl (DPPH), carotene/linoleic acid bleaching, and thiobarbituric acid reactive substances (TBARS) assays. Their ability to prevent the production of advanced glycation end products (AGEs) was also evaluated, and both extracts showed important activity, especially HE. The extracts also stimulated the fibroblasts proliferation in vitro, specialized cells that produce several mediators which maintain the skin integrity and youthfulness. Cytotoxicity of the extracts was not observed for this lineage or HEK-293, human embryonic kidney cells widely used to evaluate cytotoxicity of chemical compounds. HE also exhibited the ability to inhibit the collagenase (metalloproteinase MMP-2) and elastase activities. The total phenolic and flavonoids contents were also determined. HPLC analysis revealed the presence of the flavonoids orientin and iso-orientin, which were quantified to be used as chemical markers. The results suggested that the extracts of C. pachystachya leaves present the potential to be used in dermocosmetic formulations to prevent the skin aging process, which attracts the attention of pharmaceutical companies and researchers interested in the development of novel ingredients likely to be used as active principles in antiaging products.

Advanced glycation end products as biomarkers in systemic diseases: premises and perspectives of salivary advanced glycation end products

Advanced glycation end products (AGEs) are glycated proteins associated with high dry temperature food processing, coloring and flavor modification of food products. Previous studies on diet-related disease support the role of the glycation products as biomarkers in local and general proinflammatory response. Exogenous and endogenous AGEs are involved in chronic low-level inflammation, which underlies the onset of metabolic syndrome influenced by food intake, there by demonstrating their implication in diet-related pathologies. Although studies have revealed a strong association between the accumulation of AGEs and the occurrence/worsening of metabolic diseases, their routine use for the diagnosis or monitoring of local and general disease has not yet been reported.

Stain-free LED scanning lifetime imaging system for diabetes modified tissue matrices

In contrast to labor intensive and destructive histological techniques, intrinsic autofluorescence lifetimes of extra cellular matrix proteins can provide label-free imaging of tissue modifications in diseases, including the diabetic ulcers. However, decoupling the complex mixture of tissue fluorophores requires costly and complicated fluorescent lifetime instrumentation. Furthermore, a list of autofluorescent and fluorogenic proteins must be characterized to profile their changes during disease progression. Towards these goals, an imaging system based on frequency domain light-emitting diode (LED) modulation was designed and demonstrated, using off-the-shelf components in a low complexity design. The system was operated by coupling and imaging fluorescence intensities using a pair of objectives. The system's scanning and signal acquisition performances were optimized with respect to etendues. To study fluorescent proteins in diabetic ulcers, lifetimes from purified and pentosidine modified collagen I, collagen III, and elastin were measured. Pentosidine measurements showed a decrease in autofluorescent lifetimes while elevated collagen III in diabetic ulcers showed increased lifetimes. These lifetimes, plus future protein measurements enabled by our system, can serve as standards for developing a biophotonic model of diabetic ulcers. As a proof-of-concept, a 3 cm × 3 cm diabetic foot ulcer was imaged using the developed system. Phasor analysis was applied to aid the interpretation of lifetime images. As a result, a compact biophotonic imaging system targeting diabetic tissue was achieved, towards making the technique accessible for clinical histology.

Targeting Oxidative Stress and Mitochondrial Dysfunction in the Treatment of Impaired Wound Healing: A Systematic Review

Wound healing is a well-tuned biological process, which is achieved via consecutive and overlapping phases including hemostasis, inflammatory-related events, cell proliferation and tissue remodeling. Several factors can impair wound healing such as oxygenation defects, aging, and stress as well as deleterious health conditions such as infection, diabetes, alcohol overuse, smoking and impaired nutritional status. Growing evidence suggests that reactive oxygen species (ROS) are crucial regulators of several phases of healing processes. ROS are centrally involved in all wound healing processes as low concentrations of ROS generation are required for the fight against invading microorganisms and cell survival signaling. Excessive production of ROS or impaired ROS detoxification causes oxidative damage, which is the main cause of non-healing chronic wounds. In this context, experimental and clinical studies have revealed that antioxidant and anti-inflammatory strategies have proven beneficial in the non-healing state. Among available antioxidant strategies, treatments using mitochondrial-targeted antioxidants are of particular interest. Specifically, mitochondrial-targeted peptides such as elamipretide have the potential to mitigate mitochondrial dysfunction and aberrant inflammatory response through activation of nucleotide-binding oligomerization domain (NOD)-like family receptors, such as the pyrin domain containing 3 (NLRP3) inflammasome, nuclear factor-kappa B (NF-κB) signaling pathway inhibition, and nuclear factor (erythroid-derived 2)-like 2 (Nrf2).

The effects of advanced glycation end products (AGEs) on dermal wound healing and scar formation: a systematic review

Introduction:

With ageing, the skin gradually loses its youthful appearance and functions like wound healing and scar formation. The pathophysiological theory of Advanced Glycation End products (AGEs) has gained traction during the last decade. This review aims to document the influence of AGEs on the mechanical and physiologic properties of the skin, how they affect dermal wound healing and scar formation in high-AGE populations like elderly patients and diabetics, and potential therapeutic strategies.

Methods:

This systematic literature study involved a structured search in Pubmed and Web of Science with qualitative analysis of 14 articles after a three-staged selection process with the use of in- and exclusion criteria.

Results:

Overall, AGEs cause shortened, thinned, and disorganized collagen fibrils, consequently reducing elasticity and skin/scar thickness with increased contraction and delayed wound closure. Documented therapeutic strategies include dietary AGE restriction, sRAGE decoy receptors, aminoguanidine, RAGE-blocking antibodies, targeted therapy, thymosin β4, anti-oxidant agents and gold nanoparticles, ethyl pyruvate, Gal-3 manipulation and metformin.

Discussion:

With lack of evidence concerning scars, no definitive conclusions can yet be made about the role of AGEs on possible appearance or function of scar tissue. However, all results suggest that scars tend to be more rigid and contractile with persistent redness and reduced tendency towards hypertrophy as AGEs accumulate.

Conclusion:

Abundant evidence supports the pathologic role of AGEs in ageing and dermal wound healing and the effectiveness of possible therapeutic agents. More research is required to conclude its role in scar formation and scar therapy.

Our skin is the body’s first line of defense. It is the barrier that protects us from chemical and biological threats such as viruses, bacteria or corrosive liquids. It is the sensor that allows us to detect physical threats like extreme temperatures, pressure and pain. And when these preventative measures fail, the skin has yet another property: the ability to heal.

Skin changes visibly with age, most notably with the appearance of wrinkles. However, there is more to ageing than meets the eye; invisible alterations cause the decline of various functions of the skin, such as wound healing and scar formation. An array of non-conclusive research has been done in this field. One theory that has gained traction during the last decade is the Advanced Glycation End products (AGEs) theory. The theory states that AGEs play an important role in skin aging, wound healing and the effectiveness of different therapeutic options. Their presence supposedly indicates a diminished ability for wound healing and scar formation.

AGEs are proteins to which sugar molecule is bound. The sugar molecule inhibits the original protein from functioning properly. As skin contains many proteins like collagen, the formation of these AGEs could be a viable explanation for the diminished functioning with ageing. In this review, we investigated whether the accumulation of AGEs affects wound healing and scar formation.

Normal scar formation results in a thin scar. However, it may happen that scarring results in thick, large, painful and itchy scars. We investigated whether people with a high AGE content in their skin, like diabetics and elderly, have difficulties forming aesthetically pleasing scars. Secondly, we investigated which therapies reduce the AGE content and, if so, whether these therapies can improve wound healing and scarring. This literature study involved research in scientific databases with qualitative analysis of 14 articles after a three-staged selection process with the use of set criteria.

We found the different ways in which AGEs affect skin properties and wound healing. Collagen, one of the most important proteins in the skin, is affected by these AGEs. Once a sugar binds to it, the collagen strings becomes thinner and shorter, and the different collagen proteins cross-link with each other in an unstructured way. The result of these alterations is a reduced elasticity, i.e. the skin becomes stiffer. The scar will be thinner and the time for wounds to close is longer. We also found strategies to diminish the AGE content, including dietary AGE restriction and Metformin, a drug used in diabetes.

We can conclude that there is proof of AGEs playing an important role in skin ageing, wound healing and the effectiveness of different therapeutic options. However, more research is required to conclude the exact role of AGEs in scar formation and scar therapy.