Role of neuropeptides in skin inflammation and its involvement in diabetic wound healing

Microenvironmental dynamics of diabetic wounds and insights for hydrogel-based therapeutics

The rising prevalence of diabetes has underscored concerns surrounding diabetic wounds and their potential to induce disability. The intricate healing mechanisms of diabetic wounds are multifaceted, influenced by ambient microenvironment, including prolonged hyperglycemia, severe infection, inflammation, elevated levels of reactive oxygen species (ROS), ischemia, impaired vascularization, and altered wound physicochemical properties. In recent years, hydrogels have emerged as promising candidates for diabetic wound treatment owing to their exceptional biocompatibility and resemblance to the extracellular matrix (ECM) through a three-dimensional (3D) porous network. This review will first summarize the microenvironment alterations occurring in the diabetic wounds, aiming to provide a comprehensive understanding of its pathogenesis, then a comprehensive classification of recently developed hydrogels will be presented, encompassing properties such as hypoglycemic effects, anti-inflammatory capabilities, antibacterial attributes, ROS scavenging abilities, promotion of angiogenesis, pH responsiveness, and more. The primary objective is to offer a valuable reference for repairing diabetic wounds based on their unique microenvironment. Moreover, this paper outlines potential avenues for future advancements in hydrogel dressings to facilitate and expedite the healing process of diabetic wounds.

Neuropeptide substance P: A promising regulator of wound healing in diabetic foot ulcers

In the past, neuropeptide substance P (SP) was predominantly recognized as a neuroinflammatory factor, while its potent healing activity was overlooked. This paper aims to review the regulatory characteristics of neuropeptide SP in both normal and diabetic wound healing. SP actively in the regulation of wound healing-related cells directly and indirectly, exhibiting robust inflammatory properties, promoting cell proliferation and migration and restoring the activity and paracrine ability of skin cells under diabetic conditions. Furthermore, SP not only regulates healing-related cells but also orchestrates the immune environment, thereby presenting unique and promising application prospects in wound intervention. As new SP-based preparations are being explored, SP-related drugs are poised to become an effective therapeutic intervention for diabetic foot ulcers (DFU).

Development of Neuropeptide Hemokinin-1 Analogues with Antimicrobial and Wound-Healing Activity

Wound healing is a complex process that can be delayed in some pathological conditions, such as infection and diabetes. Following skin injury, the neuropeptide substance P (SP) is released from peripheral neurons to promote wound healing by multiple mechanisms. Human hemokinin-1 (hHK-1) has been identified as an SP-like tachykinin peptide. Surprisingly, hHK-1 shares similar structural features with antimicrobial peptides (AMPs), but it does not display efficient antimicrobial activity. Therefore, a series of hHK-1 analogues were designed and synthesized. Among these analogues, AH-4 was found to display the greatest antimicrobial activity against a broad spectrum of bacteria. Furthermore, AH-4 rapidly killed bacteria by membrane disruption, similar to most AMPs. More importantly, AH-4 showed favorable healing activity in all tested mouse full-thickness excisional wound models. Overall, this study suggests that the neuropeptide hHK-1 can be used as a desirable template for developing promising therapeutics with multiple functions for wound healing.

PDDA/Honey Antibacterial Nanofiber Composites for Diabetic Wound-Healing: Preparation, Characterization, and In Vivo Studies

In this paper, Poly (diallyldimethylammonium chloride) (PDDA)/honey nanofiber wound dressing composites were prepared and their effects on the diabetic wound-healing was evaluated using in vivo experiments. The release of effective compounds and the solubility of nanofibers were controlled through the crosslinking process by glutaraldehyde. The crosslinked nanofibers (crosslinking time was 3 h) showed an absorption capacity at a maximum value of 989.54%. Interestingly, the resultant composites were able to prevent 99.9% of Staphylococcus aureus and Escherichia coli bacteria. Furthermore, effective compounds were continuously released from nanofibers for up to 125 h. In vivo evaluation indicated that the use of PDDA/honey (40/60) significantly enhanced wound-healing. On the day 14th, the average healing rate for samples covered by conventional gauze bandage, PDDA, PDDA/honey (50/50), and PDDA/honey (40/60) were 46.8 ± 0.2, 59.4 ± 0.1, 81.7 ± 0.3, and 94.3 ± 0.2, respectively. The prepared nanofibers accelerated the wound-healing process and reduced the acute and chronic inflammation. Hence, our PDDA/honey wound dressing composites open up new future treatment options for diabetic wound diseases.

Sympathetic System in Wound Healing: Multistage Control in Normal and Diabetic Skin

In this review, we discuss sympathetic regulation in normal and diabetic wound healing. Experimental denervation studies have confirmed that sympathetic nerve endings in skin have an important and complex role in wound healing. Vasoconstrictor neurons secrete norepinephrine (NE) and neuropeptide Y (NPY). Both mediators decrease blood flow and interact with inflammatory cells and keratinocytes. NE acts in an ambiguous way depending on receptor type. Beta2-adrenoceptors could be activated near sympathetic endings; they suppress inflammation and re-epithelialization. Alpha1- and alpha2-adrenoceptors induce inflammation and activate keratinocytes. Sudomotor neurons secrete acetylcholine (ACh) and vasoactive intestinal peptide (VIP). Both induce vasodilatation, angiogenesis, inflammation, keratinocytes proliferation and migration. In healthy skin, all effects are important for successful healing. In treatment of diabetic ulcers, mediator balance could be shifted in different ways. Beta2-adrenoceptors blockade and nicotinic ACh receptors activation are the most promising directions in treatment of diabetic ulcers with neuropathy, but they require further research.

Uncovering the pharmacological mechanisms of Zizhu ointment against diabetic ulcer by integrating network analysis and experimental evaluation in vivo and in vitro

Diabetic ulcer (DU) has been recognized as one of the most prevalent and serious complications of diabetes. However, the clinical efficacy of standard treatments for DU remains poor. Traditional Chinese medicine (TCM) shows a positive therapeutic effect on DU. Specifically, Zizhu ointment (ZZO) has been widely used to treat DU in long-term clinical practice, but the exact mechanism by which it promotes DU wound healing remains unknown. In this study, network analysis and high-performance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) were conducted to identify the active compounds of ZZO. We detected isovalerylshikonin (ISO), mandenol, daidzein, kaempferol, and formononetin in both network analysis and UPLC-HRMS. Moreover, ZZO could ameliorate DU by regulating the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT) and inflammation signaling pathways, according to the results of KEGG analysis. We established a DU mouse model with a high-fat diet and streptozotocin injection in vivo to evaluate the network analysis result. The experimental results showed that ZZO could inhibit inflammation, remodel fibrous tissue, and promote angiogenesis in the DU area, facilitating wound healing in DU mice. Moreover, the PI3K/AKT signaling pathway was indeed activated by ZZO treatment, promoting macrophage M2 polarization. In addition, we used molecular docking technology to evaluate the binding sites between ZZO and the PI3K/AKT pathway. The results showed that ISO has a good binding interaction with AKT. Moreover, ISO promoted M2 polarization in macrophages in a dose-dependent manner in vitro. Our study found that ZZO could promote DU wound healing by inhibiting inflammation, which was achieved by macrophage M2 polarization through activating the PI3K/AKT pathway. Further studies have demonstrated that ISO plays major role in the above process. These findings provide a theoretical basis for further preclinical evaluation and lay a foundation for nano-gel compound treatment with ZZO.

The Contribution of Innervation to Tissue Repair and Regeneration

Animals such as amphibians have an incredible capacity for regeneration with some being able to regrow their tail or appendages. Although some mammalian tissues like the skin and bones can repair following injury, there are only a few examples of true multilineage regeneration, including the distal portion of the digit tip. In both amphibians and mammals, however, to achieve successful repair or regeneration, it is now appreciated that intact nerve innervation is a necessity. Here, we review the current state of literature and discuss recent advances that identify axon-derived signals, Schwann cells, and nerve-derived mesenchymal cells as direct and indirect supporters of adult tissue homeostasis and repair. We posit that understanding how nerves positively influence repair and regeneration could lead to targeted regenerative medicine strategies to enhance tissue repair in humans.

The Identification of the Biomarkers of Sheng-Ji Hua-Yu Formula Treated Diabetic Wound Healing Using Modular Pharmacology

Sheng-Ji Hua-Yu (SJHY) formula has been proved to reduce the severity of diabetic wound healing without significant adverse events in our previous clinical trials. However, based on multi-target characteristics, the regulatory network among herbs, ingredients, and hub genes remains to be elucidated. The current study aims to identify the biomarkers of the SJHY formula for the treatment of diabetic wound healing. First, a network of components and targets for the SJHY formula was constructed using network pharmacology. Second, the ClusterONE algorithm was used to build a modular network and identify hub genes along with kernel pathways. Third, we verified the kernel targets by molecular docking to select hub genes. In addition, the biomarkers of the SJHY formula were validated by animal experiments in a diabetic wound healing mice model. The results revealed that the SJHY formula downregulated the mRNA expression of Cxcr4, Oprd1, and Htr2a, while upregulated Adrb2, Drd, Drd4, and Hrh1. Besides, the SJHY formula upregulated the kernel pathways, neuroactive ligand-receptor interaction, and cAMP signaling pathway in the skin tissue homogenate of the diabetic wound healing mice model. In summary, this study identified the potential targets and kernel pathways, providing additional evidence for the clinical application of the SJHY formula for the treatment of diabetic wound healing.

The Modulatory Influence of Plant-Derived Compounds on Human Keratinocyte Function

The plant kingdom is a rich source of secondary metabolites with numerous properties, including the potential to modify keratinocyte biology. Keratinocytes are important epithelial cells that play a protective role against various chemical, physical and biological stimuli, and participate in reactive oxygen scavenging and inflammation and wound healing processes. The epidermal cell response may be modulated by phytochemicals via changes in signal transduction pathways. Plant extracts and single secondary compounds can possess a high antioxidant capacity and may suppress reactive oxygen species release, inhibit pro-apoptotic proteins and apoptosis and activate antioxidant enzymes in keratinocytes. Moreover, selected plant extracts and single compounds also exhibit anti-inflammatory properties and exposure may result in limited production of adhesion molecules, pro-inflammatory cytokines and chemokines in keratinocytes. In addition, plant extracts and single compounds may promote keratinocyte motility and proliferation via the regulation of growth factor production and enhance wound healing. While such plant compounds may modulate keratinocyte functions, further in vitro and in vivo studies are needed on their mechanisms of action, and more specific toxicity and clinical studies are needed to ensure their effectiveness and safety for use on human skin.

MiR-770-5p, miR-661 and miR-571 expression level in serum and tissue samples of foot ulcer caused by diabetes mellitus type II in Iranian population

BACKGROUND

Microvascular complications related to diabetes mellitus type II such as foot ulcers are the reason of many mortalities among T2DM patients. The role of microRNAs (miRNAs, miRs) as potent regulators of gene expression is studied in different diseases such as diabetes mellitus and primary studies revealed their importance as early detecting biomarkers. Therefore, in this study it is tried to evaluate the expression level of some miRNAs (miR-770-5p, miR-661 and miR-571) in serum and tissue samples of T2DM related foot ulcer among Iranian patients.

METHODS

30 samples of blood and 30 muscle tissue were collected from T2DM patients suffering foot ulcer (T2DM + FU), 30 blood samples collected from T2DM patients without foot ulcer (T2DM-FU). 30 tissue samples collected from patients with trauma and 30 blood samples were selected as healthy controls.

RESULTS

The three studied miRNAs were statistically significant in all groups in comparison to control blood group. Also, comparison between other groups showed a significant increase of all studied miRNAs especially in the blood and tissues of T2DM + FU patients. The only significant correlation detected between the FBS level and miR-571 expression pattern in blood samples of T2DM + FU group. Finally, the results showed that miR-571, -661, and -770 has a statistically significant discriminative character for differentiating T2DM + FU patients from T2DM-FU both in tissue and blood samples.

CONCLUSION

Although more studies are essential for certifying these findings, our results showed that miR-770-5p, miR-661 and miR-571 are correlated with the microvascular complications related with T2DM such as foot ulcer.

Cutaneous innervation in impaired diabetic wound healing

Type 2 diabetes is associated with several potential comorbidities, among them impaired wound healing, chronic ulcerations, and the requirement for lower extremity amputation. Disease-associated abnormal cellular responses, infection, immunological and microvascular dysfunction, and peripheral neuropathy are implicated in the pathogenesis of the wound healing impairment and the diabetic foot ulcer. The skin houses a dense network of sensory nerve afferents and nerve-derived modulators, which communicate with epidermal keratinocytes and dermal fibroblasts bidirectionally to effect normal wound healing after trauma. However, the mechanisms through which cutaneous innervation modulates wound healing are poorly understood, especially in humans. Better understanding of these mechanisms may provide the basis for targeted treatments for chronic diabetic wounds. This review provides an overview of wound healing pathophysiology with a focus on neural involvement in normal and diabetic wound healing, as well as future therapeutic perspectives to address the unmet needs of diabetic patients with chronic wounds.

Neuropeptides, Inflammation, Biofilms, and diabetic Foot Ulcers

A diabetic foot ulcer (DFU) is a serious complication in patients with diabetes mellitus (DM). A DFU is the most common cause of non-traumatic limb amputation, and patients with DFUs have increased mortality rates within 5 years after amputation. DFUs also increase the risk of cardiovascular and cerebrovascular diseases; therefore, with the increasing incidence and prevalence of diabetic foot wounds, DFUs are gradually becoming a major public health problem. The pathophysiology of DFUs is complicated and remains unclear. In recent years, many studies have demonstrated that the pathophysiology of DFUs is especially associated with neuropeptides, inflammation, and biofilms. Neuropeptides, especially substance P (SP) and calcitonin gene-related peptide (CGRP), play an important role in wound healing. SP and CGRP accelerate the healing of cutaneous wounds by promoting neovascularization, inhibiting the release of certain proinflammatory chemokines, regulating macrophage polarization, and so on. However, the expression of SP and CGRP was downregulated in DM and DFUs. DFUs are characterized by a sustained inflammatory phase. Immune cells such as neutrophils and macrophages are involved in the sustained inflammatory phase in DFUs by extracellular traps (NETs) and dysregulated macrophage polarization, which delays wound healing. Furthermore, DFUs are at increased risk of biofilm formation. Biofilms disturb wound healing by inducing a chronic inflammatory response, inhibiting macrophage phagocytosis and keratinocyte proliferation migration, and transferring antimicrobial resistance genes. To understand the relationships among neuropeptides, inflammation, biofilms, and DFUs, this review highlights the recent scientific advances that provide possible pathophysiological insights into the delayed healing of DFUs.

Potential Applications of Nanomaterials and Technology for Diabetic Wound Healing

Diabetic wound shows delayed and incomplete healing processes, which in turn exposes patients to an environment with a high risk of infection. This article has summarized current developments of nanoparticles/hydrogels and nanotechnology used for promoting the wound healing process in either diabetic animal models or patients with diabetes mellitus. These nanoparticles/hydrogels promote diabetic wound healing by loading bioactive molecules (such as growth factors, genes, proteins/peptides, stem cells/exosomes, etc.) and non-bioactive substances (metal ions, oxygen, nitric oxide, etc.). Among them, smart hydrogels (a very promising method for loading many types of bioactive components) are currently favored by researchers. In addition, nanoparticles/hydrogels can be combined with some technology (including PTT, LBL self-assembly technique and 3D-printing technology) to treat diabetic wound repair. By reviewing the recent literatures, we also proposed new strategies for improving multifunctional treatment of diabetic wounds in the future.

Polyurethane/carboxymethylcellulose nanofibers containing Malva sylvestris extract for healing diabetic wounds: Preparation, characterization, in vitro and in vivo studies

In this study, new polyurethane (PU)-based nanofibers wound dressings containing Malva sylvestris extract were prepared and their effect on diabetic wound healing process was evaluated. Different amounts of carboxymethyl cellulose (CMC) were used to improve the absorption ability of wound exudates. The result showed that the usage of 20% w/w CMC in the polymer blend; and producing of nanofibers with an average diameter of 386.5 nm, led to the gradual release of the herbal compound in 85 h and bead-free morphology. Due to the antibacterial activity of wound dressing and wound healing process, the amount of 15% w/w herbal extract was selected as the optimum. For this sample, the fluid absorption was 412.31%. The extract loaded wound dressing samples showed satisfactory effects on Staphylococcus aureus and Escherichia coli bacteria. In vivo wound-healing and histological performance observations indicated that the use of the herbal extract in wound dressing improved wound healing significantly. On day 14, the average healing rate for gauze bandage, PU/CMC, and different amounts of 5, 10, 15 and 20% w/w extract containing wound dressings was 32.1 ± 0.2%, 51.4 ± 0.4%, 71 ± 0.14%, 87.64 ± 1.02%, 95.05 ± 0.24% and 95.11 ± 0.2%, respectively. Compared to the control groups, treatments with extract loaded wound dressings were effective in lowering acute and chronic inflammations. In diabetic rat wounds, collagen deposition and neovascularization were higher in wounds treated with an herbal extract containing wound dressing compared to the wounds treated with a gauze bandage and PU/CMC treated wounds. It can be suggested that this product may be considered as a good dual anti-inflammatory-antimicrobial wound dressing candidate for improving the diabetic wound healing.

Diabetic Foot Ulcers: Current Advances in Antimicrobial Therapies and Emerging Treatments

Diabetic foot ulcers (DFUs) are very important diabetes-related lesions that can lead to serious physical consequences like amputations of limbs and equally severe social, psychological, and economic outcomes. It is reported that up to 25% of patients with diabetes develop a DFU in their lifetime, and more than half of them become infected. Therefore, it is essential to manage infection and ulcer recovery to prevent negatives outcomes. The available information plays a significant role in keeping both physicians and patients aware of the emerging therapies against DFUs. The purpose of this review is to compile the currently available approaches in the managing and treatment of DFUs, including molecular and regenerative medicine, antimicrobial and energy-based therapies, and the use of plant extracts, antimicrobial peptides, growth factors, ozone, devices, and nano-medicine, to offer an overview of the assessment of this condition.

Trauma in the Diabetic Limb

Poorly controlled diabetes with comorbid manifestations negatively affects outcomes in lower extremity trauma, increasing the risk of short-term and long-term complications. Management strategies of patients with diabetes that experience lower extremity trauma should also include perioperative management of hyperglycemia to reduce adverse and serious adverse events.

The role of microRNAs in the healing of diabetic ulcers

MicroRNAs (miRNAs) are small protected molecules with a length of 18 to 25 nucleotides. Many studies have recently been conducted on miRNAs, illustrating their role in regulating many biological, physiological, and pathological activities, such as maintaining cellular signalling and regulating cellular pathways. The main role of miRNAs is to regulate the expression of genes after translation, which can lead to the destruction or suppression of translation by binding to mRNAs. As any change in the regulation of miRNAs is associated with several physiological abnormalities, such as type 2 diabetes and its complications, these molecules can be used for therapeutic purposes or as biomarkers for the diagnosis of diseases such as diabetes and its complications. In this review article, we will discuss important findings about the miRNAs and the role of these molecules in different phases of the wound-healing process of chronic wounds, especially diabetic ulcer.

Controlled-release neurotensin-loaded silk fibroin dressings improve wound healing in diabetic rat model

Diabetic foot ulcers (DFU), which may lead to lower extremity amputation, is one of the severe and chronic complications of diabetic mellitus. This study aims to develop, and use dressings based on Silk fibroin (SF) as the scaffold material, gelatin microspheres (GMs) as the carrier for the neurotensin (NT), a neuropeptide that acts as an inflammatory modulator in wound healing and NT as accelerate wound healing drug to treat DFU. We evaluated the wound healing processes and neo-tissue formation in rat diabetic model by macroscopic observation, histological observation (H&E staining and Masson's trichrome staining) and immunofluorescence analysis at 3, 7, 14, 21 and 28 post-operation days. Our results show that the NT/GMs/SF group performance the best not only in macroscopic healing and less scars in 28 post-operation days, but also in fibroblast accumulation in tissue granulation, collagen expression and deposition at the wound site. From release profiles, we can know the GMs are a good carrier for control release drugs. The SEM results shows that the NT/GMs/SF dressings have an average pore size are 40–80 μm and a porosity of ∼85%, this pore size is suit for wound healing regeneration. These results suggest that the NT/GMs/SF dressings may work as an effective support for control release NT to promote DFU wound healing.

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This study aims to develop, and use dressings based on Silk fibroin (SF) as the scaffold material, gelatin microspheres (GMs) as the carrier for the Neurotensin (NT), a neuropeptide that acts as an inflammatory modulator in wound healing and NT as accelerate wound healing drug to treat DFU.

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The NT/GMs/SF dressings stimulated fibroblast accumulation in tissue granulation, collagen expression and deposition at the wound site, which lead to the production of a more organized collagen matrix.

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This treatment effectively accelerating wound regeneration and re-epithelialization.

Immune aging in diabetes and its implications in wound healing

Immune systems have evolved to recognize and eliminate pathogens and damaged cells. In humans, it is estimated to recognize 109 epitopes and natural selection ensures that clonally expanded cells replace unstimulated cells and overall immune cell numbers remain stationary. But, with age, it faces continuous repertoire restriction and concomitant accumulation of primed cells. Changes shaping the aging immune system have bitter consequences because, as inflammatory responses gain intensity and duration, tissue-damaging immunity and inflammatory disease arise. During inflammation, the glycolytic flux cannot cope with increasing ATP demands, limiting the immune response's extent. In diabetes, higher glucose availability stretches the glycolytic limit, dysregulating proteostasis and increasing T-cell expansion. Long-term hyperglycemia exerts an accumulating effect, leading to higher inflammatory cytokine levels and increased cytotoxic mediator secretion upon infection, a phenomenon known as diabetic chronic inflammation. Here we review the etiology of diabetic chronic inflammation and its consequences on wound healing.

Recent advancements in biopolymer and metal nanoparticle-based materials in diabetic wound healing management

Currently, diabetes mellitus (DM) accelerated diabetic foot ulcer (DFU) remains vivacious health problem related with delayed healing and high amputation rates which leads to enormous clinical obligation. Keeping in view of the foregoing, researchers have been made in their efforts to develop novel materials which accelerate delayed wound healing in the diabetic patient and reduce the adversative influences of DFUs. The most prominent materials used for the wound healing application have biocompatibility, low cytotoxicity, excellent biodegradable properties, and antimicrobial activity properties. Utilization of nanoparticles has emerged as a protruding scientific and technological revolution in controlling DFUs. Biopolymers in combination with bioactive nanoparticles having antimicrobial, antibacterial, and anti-inflammatory properties have great potential in wound care to enhance the healing process of diabetic wound infectious. Combination of antibacterial nanoparticles like silver nanoparticles (AgNPs), gold nanoparticles (AuNPs), copper nanoparticles (CuNPs) etc. with polymeric matrix could efficiently inhibit bacterial growth and at the same time fastens the healing process of a wound. This review briefed the recent development of different natural polymers and antibacterial nanoparticles to mitigate the diabetes mellitus based DFU.

Optimized Scratch Assay for In Vitro Testing of Cell Migration with an Automated Optical Camera

Cell migration is an important process that influences many aspects of health, such as wound healing and cancer, and it is, therefore, crucial for developing methods to study the migration. The scratch assay has long been the most common in vitro method to test compounds with anti- and pro-migration properties because of its low cost and simple procedure. However, an often-reported problem of the assay is the accumulation of cells across the edge of the scratch. Furthermore, to obtain data from the assay, images of different exposures must be taken over a period of time at the exact same spot to compare the movements of the migration. Different analysis programs can be used to describe the scratch closure, but they are labor intensive, inaccurate, and forces cycles of temperature changes. In this study, we demonstrate an optimized method for testing the migration effect, e.g. with the naturally occurring proteins Human- and Bovine-Lactoferrin and their N-terminal peptide Lactoferricin on the epithelial cell line HaCaT. A crucial optimization is to wash and scratch in PBS, which eliminates the aforementioned accumulation of cells along the edge. This could be explained by the removal of cations, which have been shown to have an effect on keratinocyte cell-cell connection. To ensure true detection of migration, pre-treating with mitomycin C, a DNA synthesis inhibitor, was added to the protocol. Finally, we demonstrate the automated optical camera, which eliminates excessive temperature cycles, manual labor with scratch closure analysis, while improving on reproducibility and ensuring analysis of identical sections of the scratch over time.

Neurotensin, substance P, and insulin enhance cell migration

Neurotensin, substance P, and insulin have been demonstrated to improve wound healing in vivo. However, the mechanism behind their effect is still not fully understood. This study investigates the effects leading to enhanced scratch closure by these peptides in vitro. The skin keratinocyte cell line, HaCaT, was used to test scratch closure effects of the peptides and alterations of cytokine levels. HUVEC cells were used to test the angiogenic effect of the peptides. Furthermore, clinical isolates of Staphylococcus lugdunensis were used to examine the potential antimicrobial activity of each peptide. Our results demonstrate that neurotensin, substance P, and insulin had significant migratory effects in scratch assays were neurotensin had the lowest effect. Furthermore, we investigated use of the peptides in combination. When substance P was used in combination with neurotensin, the cell migratory capacity was decreased, and the peptides showed a negative correlation (r = -0.298, P < .001). Neurotensin and insulin significantly increased levels of monocyte chemoattractant protein-1 (P < .001) secreted from white blood cells, whereas substance P showed a tendency. Interestingly, neurotensin increased the level of monocyte chemoattractant protein-1 significantly compared to substance P (P < .01). Additionally, the peptides decreased TNFα mRNA levels (P < .001) in HaCaT cells, whereas only neurotensin and insulin decreased IL-8 mRNA (P < .001) but had no significant effect on IL-6 mRNA levels. Surprisingly, substance P increased IL-6 mRNA 9-fold (P < .001). Furthermore, we demonstrate that the peptides increased angiogenesis in the HUVEC cells (P < .001). Finally, S. lugdunensis isolates were not susceptible to the peptides. We demonstrate that the peptides worked differently on HaCaT cells, but substance P acted differently than neurotensin on cytokine levels expression as well as on migration of HaCaT cells. On the contrary, neurotensin and insulin worked similarly. All of these aspects are crucial for proper wound healing, and the results suggest multiple mechanisms for wound-healing properties of these peptides.

Topical application of Hydroxysafflor Yellow A accelerates the wound healing in streptozotocin induced T1DM rats

To investigate the effects of Hydroxysafflor Yellow A (HSYA), which is derived from safflower, on the proliferation, migration and angiogenesis of cells in vitro and its potential efficacy in vivo when topically applied to a diabetic wound. Human umbilical vein endothelial cells (HUVECs) and mouse macrophage cells (RAW264.7) were used to evaluate angiogenesis and anti-inflammatory activities, respectively. The influence of HSYA on the wound scratch assay was investigated in keratinocytes. A splinted excisional wound model in rats with TIDM induced by streptozotocin was used to assess the effects of wound healing. Collagen disposition and secretion of vascular growth factors (VEGF) as well as transforming growth factor-β1 (TGF-β1) were evaluated by an ELISA assay and histological staining. The in vitro results showed that HSYA could significantly enhance both the neovascularization of HUVECs and the migration of keratinocytes. It showed the significant inhibitory effect on nitric oxide production, indicating the anti-inflammatory activity of HSYA. In vivo, the topical application of HSYA significantly enhanced the wound closure rate, and the time to complete wound closure was 17 days, whereas 30 days were needed with PBS treatment. Further, treatment with HSYA exhibited significant granulation tissue formation with higher collagen content, re-epithelialization and angiogenesis according to Masson's trichrome staining evaluation, VEGE and TGF-β1 ELISA measurement. In conclusion, HSYA application could be considered a promising therapeutic strategy for treating chronic non-healing diabetic foot ulcers.

A Chitosan-Based Liposome Formulation Enhances the In Vitro Wound Healing Efficacy of Substance P Neuropeptide

Currently, there is considerable interest in developing innovative biodegradable nanoformulations for controlled administration of therapeutic proteins and peptides. Substance P (SP) is a neuropeptide of 11 amino acids that belongs to the tachykinins family and it plays an important role in wound healing. However, SP is easily degradable in vivo and has a very short half-life, so the use of chitosan-based nanocarriers could enhance its pharmaceutical properties. In light of the above, the aim of this work was to produce and characterize chitosan-coated liposomes loaded with SP (SP-CH-LP) as novel biomaterials with potential application in mucosal wound healing. The loaded system’s biophysical properties were characterized by dynamic light scattering with non-invasive back scattering (DLS-NIBS), mixed mode measurements and phase analysis light scattering (M3-PALS) and high performance liquid chromatography with ultraviolet/visible light detection (HPLC-UV/VIS). Then, the efficacy of the obtained nanoformulations was examined via proof-of-principle experiments using in vitro cell assays. These assays showed an increment on cell motility and proliferation after treatment with free and encapsulated neuropeptides. Additionally, the effect of SP on wound healing was enhanced by the entrapment on CH-LP. Overall, the amenability of chitosan-based nanomaterials to encapsulate peptides and proteins constitutes a promising approach towards potential novel therapies to treat difficult wounds.

pH and Glucose Dual-Responsive Injectable Hydrogels with Insulin and Fibroblasts as Bioactive Dressings for Diabetic Wound Healing

pH and glucose dual-responsive injectable hydrogels were prepared through the cross-linking of Schiff's base and phenylboronate ester using phenylboronic-modified chitosan, poly(vinyl alcohol) and benzaldehyde-capped poly(ethylene glycol). Protein drugs and live cells could be incorporated into the hydrogels during the in situ cross-linking, displaying sustained and pH/glucose-triggered drug release from the hydrogels and cell viability and proliferation in the three-dimensional hydrogel matrix as well. Hence, the hydrogels with insulin and fibroblasts were considered as bioactive dressings for diabetic wound healing. A streptozotocin-induced diabetic rat model was used to evaluate the efficacy of hydrogel dressings in wound repair. The results revealed that the incorporation of insulin and L929 in the hydrogels could promote neovascularization and collagen deposition and enhance the wound-healing process of diabetic wounds. Thus, the drug- and cell-loaded hydrogels have promising potential in wound healing as a medicated system for various therapeutic proteins and live cells.

Microbiota of Chronic Diabetic Wounds: Ecology, Impact, and Potential for Innovative Treatment Strategies

World Health Organization considered diabetes as one of the 20th century epidemics, estimating that over 10% of the world population is diabetic or at high risk. Self-assessment studies indicate that diabetic patients consider chronic wounds to affect their quality of life more dramatically than vision loss or renal failure. In addition to being the main reason for diabetic patients' hospitalization, the economic burden of diabetic chronic wounds is close to 1% of United Kingdom and United States health systems budgets, which exceeds the funds allocated to the treatment of some types of cancer in both countries. Among the factors preceding the emergence of chronic diabetic wounds, also designated diabetic foot ulcers (DFUs), hygiene and pressure in specific areas are under patient control, while others are still far from being understood. A triple impairment in the innervation, immune responses, and vascularization associated to DFU has been extensively studied by the scientific community. However, the skin natural microbiota has only recently emerged as having a tremendous impact on DFU emergence and evolution to chronicity. Despite the great inter- and intra-variability of microbial colonizers, ongoing efforts are now focused on deciphering the impact of commensal and pathogenic microbiota on DFU etiology, as well as the mechanisms of interkingdom microbial-host communication. This review summarizes recent work in this context and offers new microbiological perspectives that may hold potential in the prevention and treatment of chronic diabetic wounds.

Nanoencapsulation, an efficient and promising approach to maximize wound healing efficacy of curcumin: A review of new trends and state-of-the-art

Wound healing is a multifarious and vibrant process of replacing devitalized and damaged cellular structures, leading to restoration of the skin's barrier function, re-establishment of tissue integrity, and maintenance of the internal homeostasis. Curcumin (CUR) and its analogs have gained widespread recognition due to their remarkable anti-inflammatory, anti-infective, anticancer, immunomodulatory, antioxidant, and wound healing activities. However, their pharmaceutical significance is limited due to inherent hydrophobic nature, poor water solubility, low bioavailability, chemical instability, rapid metabolism and short half-life. Owing to their pharmaceutical limitations, newer strategies have been attempted in recent years aiming to mitigate problems related to the effective delivery of curcumanoids and to improve their wound healing potential. These advanced strategies include nanovesicles, polymeric micelles, conventional liposomes and hyalurosomes, nanocomposite hydrogels, electrospun nanofibers, nanohybrid scaffolds, nanoconjugates, nanostructured lipid carriers (NLCs), nanoemulsion, nanodispersion, and polymeric nanoparticles (NPs). The superior wound healing activities achieved after nanoencapsulation of the CUR are attributed to its target-specific delivery, longer retention at the target site, avoiding premature degradation of the encapsulated cargo and the therapeutic superiority of the advanced delivery systems over the conventional delivery. We have critically reviewed the literature and summarize the convincing evidence which explore the pharmaceutical significance and therapeutic feasibility of the advanced delivery systems in improving wound healing activities of the CUR and its analogs.

Neuropathy and Diabetic Foot Syndrome

Diabetic foot ulceration is a serious complication of diabetes mellitus worldwide and the most common cause of hospitalization in diabetic patients. The etiology of diabetic foot ulcerations is complex due to their multifactorial nature; in the pathophysiology of diabetic foot ulceration polyneuropathy is important. Proper adherence to standard treatment strategies and interdisciplinary cooperation can reduce the still high rates of major amputations.

Nanomaterials as a game changer in the management and treatment of diabetic foot ulcers

Nanoengineered biomaterials have tremendously improved the range of tools utilized for the control of as well as acceleration of healing of diabetic foot ulcers (DFU) over the last few decades.

The Roles of Growth Factors in Keratinocyte Migration

Significance: The re-epithelialization of wounded skin requires the rapid and coordinated migration of keratinocytes (KC) into the wound bed. Almost immediately after wounding, cells present at or attracted to the wound site begin to secrete a complex milieu of growth factors. These growth factors exert mitogenic and motogenic effects on KCs, inducing the rapid proliferation and migration of KCs at the wound edge. Recent Advances: New roles for growth factors in KC biology are currently being discovered and investigated. This review will highlight the growth factors, particularly transforming growth factor-α (TGF-α), heparin-binding epidermal growth factor (HB-EGF), insulin-like growth factor 1 (IGF-1), fibroblast growth factor 7 (FGF-7), FGF-10, and hepatocyte growth factor (HGF), which have conclusively been shown to be the most motogenic for KCs. Critical Issues: The cellular and molecular heterogeneity of wounded tissue makes establishing direct relationships between specific growth factors and KC migration difficult in situ. The absence of this complexity in simplified in vitro experimental models of migration makes the clinical relevance of the results obtained from these in vitro studies ambiguous. Future Directions: Deciphering the relationship between growth factors and KC migration is critical for understanding the process of wound healing in normal and disease states. Insights into the basic science of the effects of growth factors on KC migration will hopefully lead to the development of new therapies to treat acute and chronic wounds.

The Role of MicroRNAs in Diabetic Complications-Special Emphasis on Wound Healing

Overweight and obesity are major problems in today’s society, driving the prevalence of diabetes and its related complications. It is important to understand the molecular mechanisms underlying the chronic complications in diabetes in order to develop better therapeutic approaches for these conditions. Some of the most important complications include macrovascular abnormalities, e.g., heart disease and atherosclerosis, and microvascular abnormalities, e.g., retinopathy, nephropathy and neuropathy, in particular diabetic foot ulceration. The highly conserved endogenous small non-coding RNA molecules, the micro RNAs (miRNAs) have in recent years been found to be involved in a number of biological processes, including the pathogenesis of disease. Their main function is to regulate post-transcriptional gene expression by binding to their target messenger RNAs (mRNAs), leading to mRNA degradation, suppression of translation or even gene activation. These molecules are promising therapeutic targets and demonstrate great potential as diagnostic biomarkers for disease. This review aims to describe the most recent findings regarding the important roles of miRNAs in diabetes and its complications, with special attention given to the different phases of diabetic wound healing.

Neurotensin decreases the proinflammatory status of human skin fibroblasts and increases epidermal growth factor expression

Fibroblasts colonization into injured areas during wound healing (WH) is responsible for skin remodelling and is also involved in the modulation of inflammation, as fibroblasts are immunologically active. Herein, we aimed to determine neurotensin effect on the immunomodulatory profile of fibroblasts, both in homeostatic and inflammatory conditions. Neurotensin mediated responses occurred through NTR1 or NTR3 receptors, while under inflammatory conditions NTR1 expression increase seemed to modulate neurotensin responses. Among different immunomodulatory genes, CCL11, IL-8, and IL-6 were the most expressed genes, while CCL4 and EGF were the less expressed genes. After neurotensin exposure, IL-8 mRNA expression was increased while CCL11 was decreased, suggesting a proinflammatory upregulation and chemoattractant ability downregulation of fibroblasts. Under inflammatory conditions, gene expression was significantly increased. After neurotensin exposure, CCL4 and IL-6 mRNA expression were decreased while CCL11 was increased, suggesting again a decrease in the chemoattractant capacity of fibroblasts and in their proinflammatory status. Furthermore, the expression of EGF, a crucial growth factor for skin cells proliferation and WH, was increased in all conditions. Overall, neurotensin, released by nerve fibers or skin cells, may be involved in the decrease of the chemotaxis and the proinflammatory status in the proliferation and remodelling phases of WH.

Evaluation of soluble CD200 levels in type 2 diabetic foot and nephropathic patients: association with disease activity

BACKGROUND

CD200 (OX-2) is a novel immune-effective molecule, existing in a cell membrane-bound form, as well as in a soluble form in serum (s OX-2), which acts to regulate inflammatory and acquired immune responses.

MATERIAL AND METHODS

We planned this study to evaluate the sOX-2 levels of type 2 diabetic foot (group B), and compare it with that of healthy controls (group A). The patient group had the following values: DM period: 27.9±10.3 year [mean ±SD], HbA1c: 9.52±2.44% [mean ±SD].

RESULTS

Blood samples for sCD200 measurement were always taken in the morning between 8 and 10 A.M.. The results were reported as means of duplicate measurements. Concentrations of sOX-2 in the serum samples were quantified using an ELISA kit. Serum hs-CRP levels were measured using an hs-CRP assay kit. The sOX-2 level in group B was 173.8±3.1 and in group A was 70.52±1.2 [p<0.0001). In subgroup analysis of T2DM-DFI patients, we noticed that sOX-2 levels were higher in WGS (Wagner grading system) I and II patients than in WGS III and IV patients. The HbA1c, BUN, creatinine, hs-CRP levels, and sedimentation rates were higher in the patient group (p<0.0001, p<0.001, p<0.001, p<0.005, and p<0.0001, respectively).

CONCLUSIONS

We suggest that there are vascular, immunologic, and neurologic components in DFI, whereas autoimmune diseases and inflammatory skin disorders have only an immunologic component. This is possibly evidence of a pro-inflammatory effect seen in DFI as a vascular complication.

Neuropathy and poorly controlled diabetes increase the rate of surgical site infection after foot and ankle surgery

BACKGROUND

This prospective study was designed to evaluate the frequency of surgical site infection in patients treated with foot and ankle surgery. Our hypothesis was that patients with complications of diabetes are at increased risk for surgical site infection compared with patients without diabetes and patients with diabetes who do not have diabetic complications. Another goal was to compare the association of neuropathy with surgical site infection in both nondiabetic and diabetic patients.

METHODS

Two thousand and sixty consecutive surgical cases were evaluated. Group 1 included nondiabetic patients without neuropathy, Group 2 included nondiabetic patients with neuropathy, Group 3 included patients with diabetes but no diabetic complications, and Group 4 included patients with diabetes who had at least one complication of diabetes.

RESULTS

The surgical site infection rate in this study was 3.1%. Patients with complicated diabetes had a 7.25-fold increased risk of surgical site infection compared with nondiabetic patients without neuropathy and a 3.72-fold increased risk compared with patients with uncomplicated diabetes. Patients with complicated diabetes had a nonsignificant 1.54-fold higher rate of surgical site infection compared with nondiabetic patients with neuropathy. Nondiabetic patients with neuropathy had a significant 4.72-fold increased risk of surgical site infection compared with nondiabetic patients without neuropathy. Despite this, nondiabetic patients with neuropathy did not have a significantly higher rate of surgical site infection than patients with uncomplicated diabetes, and the frequency of surgical site infection in the group with uncomplicated diabetes was not significantly different from that in the nondiabetic patients without neuropathy. Multivariable logistic regression analysis demonstrated that peripheral neuropathy and a hemoglobin A1c of ≥8% were independently associated with surgical site infection.

CONCLUSIONS

Complicated diabetes increases the risk of surgical site infection after foot and ankle surgery. Patients who had diabetes without complications did not have a greater risk of surgical site infection compared with nondiabetic patients without neuropathy. The presence of neuropathy increases the risk of surgical site infection even in patients without diabetes. Poor long-term glycemic control is also associated with an increased risk of surgical site infection.

LEVEL OF EVIDENCE

Prognostic Level I. See Instructions for Authors for a complete description of levels of evidence.

Chitosan-based dressings loaded with neurotensin--an efficient strategy to improve early diabetic wound healing

One important complication of diabetes mellitus is chronic, non-healing diabetic foot ulcers (DFUs). This study aims to develop and use dressings based on chitosan derivatives for the sustained delivery of neurotensin (NT), a neuropeptide that acts as an inflammatory modulator in wound healing. Three different derivatives, namely N-carboxymethyl chitosan, 5-methyl pyrrolidinone chitosan (MPC) and N-succinyl chitosan, are presented as potential biomaterials for wound healing applications. Our results show that MPC has the best fluid handling capacity and delivery profile, also being non-toxic to Raw 264.7 and HaCaT cells. NT-loaded and non-loaded MPC dressings were applied to control/diabetic wounds to evaluate their in vitro/in vivo performance. The results show that the former induced more rapid healing (50% wound area reduction) in the early phases of wound healing in diabetic mice. A NT-loaded MPC foam also reduced expression of the inflammatory cytokine TNF-α (P<0.001) and decreased the amount of inflammatory infiltrate on day 3. On day 10 MMP-9 was reduced in diabetic skin (P<0.001), significantly increasing fibroblast migration and collagen (COL1A1, COL1A2 and COL3A1) expression and deposition. These results suggest that MPC-based dressings may work as an effective support for sustained NT release to reduce DFUs.

The effect of neurotensin in human keratinocytes--implication on impaired wound healing in diabetes

Diabetic foot ulcers are an important complication of diabetes mellitus characterized by chronic, non-healing ulcers resulting from poor proliferation and migration of fibroblasts and keratinocytes, thus impairing a correct re-epithelialization of wounded tissues. This healing process can be modulated by neuropeptides released from peripheral nerves; however, little is known regarding the role of neurotensin (NT) as a modulator of human keratinocyte function under hyperglycemic conditions. Therefore, this work is focused on the effect of NT in human keratinocytes, under normal and hyperglycemic conditions at different functional levels, namely NT receptors, cytokine, and growth factor expression, as well as proliferation and migration. Human keratinocyte cells were maintained at either 10/30 mM glucose and treated with or without NT (10 nM). The results show that NT did not affect keratinocyte viability. In addition, NT and all NT receptor expression levels were significantly reduced by hyperglycemia; however, NT treatment stimulated expression of NT and neurotensin receptor 2 (NTR2) while neurotensin receptor 1 (NTR1) and neurotensin receptor 3 (NTR3) expression levels were unchanged. Keratinocyte proliferation was not affected by NT and hyperglycemia, while cell migration was reduced by NT treatment. These results demonstrated that hyperglycemic conditions strongly impaired endogenous NT and NTR2 expression in keratinocytes. Despite the addition of exogenous NT to stimulate the endogenous NT and NTR2 expression, these changes do not translate into functional modifications on keratinocytes, particularly in terms of migration, proliferation, and production of cytokines or growth factors. These results suggest that NT production by keratinocytes may exert a paracrine effect on other skin cells, namely fibroblasts, macrophages, and dendritic cells for correct wound healing.

Neurotensin-loaded collagen dressings reduce inflammation and improve wound healing in diabetic mice

Impaired wound healing is an important clinical problem in diabetes mellitus and results in failure to completely heal diabetic foot ulcers (DFUs), which may lead to lower extremity amputations. In the present study, collagen based dressings were prepared to be applied as support for the delivery of neurotensin (NT), a neuropeptide that acts as an inflammatory modulator in wound healing. The performance of NT alone and NT-loaded collagen matrices to treat wounds in streptozotocin (STZ) diabetic induced mice was evaluated. Results showed that the prepared dressings were not-cytotoxic up to 72h after contact with macrophages (Raw 264.7) and human keratinocyte (HaCaT) cell lines. Moreover, those cells were shown to adhere to the collagen matrices without noticeable change in their morphology. NT-loaded collagen dressings induced faster healing (17% wound area reduction) in the early phases of wound healing in diabetic wounded mice. In addition, they also significantly reduced inflammatory cytokine expression namely, TNF-α (p<0.01) and IL-1β (p<0.01) and decreased the inflammatory infiltrate at day 3 post-wounding (inflammatory phase). After complete healing, metalloproteinase 9 (MMP-9) is reduced in diabetic skin (p<0.05) which significantly increased fibroblast migration and collagen (collagen type I, alpha 2 (COL1A2) and collagen type III, alpha 1 (COL3A1)) expression and deposition. These results suggest that collagen-based dressings can be an effective support for NT release into diabetic wound enhancing the healing process. Nevertheless, a more prominent scar is observed in diabetic wounds treated with collagen when compared to the treatment with NT alone.

Keratinocytes express cytokines and nerve growth factor in response to neuropeptide activation of the ERK1/2 and JNK MAPK transcription pathways

Sensory neurons innervating the skin can release neuropeptides that are believed to modulate cellular proliferation, wound healing, pigmentation, and keratinocyte innate immune responses. While the ability of neuropeptides to stimulate keratinocyte production of inflammatory mediators has been demonstrated, there is no information concerning the mechanisms by which neuropeptide activation of keratinocyte cell surface receptors ultimately leads to the up-regulation of mediator production. In this study we used a keratinocyte cell line to identify the presence of substance P (SP) and calcitonin gene-related peptide (CGRP) receptors on keratinocytes and examined the effects of SP and CGRP stimulation on keratinocyte neuropeptide signaling, cell proliferation, and interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor α (TNF-α), and nerve growth factor (NGF) expression. Neuropeptide stimulation caused an up-regulation of neuropeptide receptor expression in keratinocytes and a dramatic increase in keratinocyte secretion of SP and CGRP, suggesting possible autocrine or paracrine stimulatory effects and amplification of neuropeptide signaling. Both SP and CGRP concentration-dependently stimulated cellular proliferation and the expression and secretion of inflammatory cytokines and NGF in keratinocytes. SP also activated all 3 families of mitogen activated protein kinase (MAPK) and nuclear factor κB (NFκB) in keratinocytes, while CGRP only activated p38 and extracellular signal related kinase1/2 (ERK1/2) MAPKs. Neuropeptide stimulated inflammatory mediatory production in keratinocytes was reversed by ERK1/2 and JNK inhibitors. The current study is the first to observe; 1) that CGRP stimulates keratinocyte expression of CGRP and its receptor complex, 2) that SP and CGRP stimulate IL-6 and TNF-α secretion in keratinocytes, 3) that SP activated all three MAPK families and the NFκB transcriptional signaling pathway in keratinocytes, and 4) that SP and CGRP stimulated inflammatory mediator production in keratinocytes is dependent on ERK1/2 and JNK activation. These studies provide evidence suggesting that disruption of ERK1/2 and JNK signaling may potentially be an effective therapy for inflammatory skin diseases and pain syndromes mediated by exaggerated sensory neuron-keratinocyte signaling.