Increased skin inflammation and blood vessel density in human and experimental diabetes

Association between monocyte to lymphocyte ratio and diabetic foot ulcer in the population of the US with diabetes based on the 1999-2004 National Health and Nutrition Examination Survey data: a retrospective cross-sectional study

Background

Diabetic foot ulcer (DFU) is a severe complication that occurs in patients with diabetes and is a primary factor that necessitates amputation. Therefore, the occurrence and progression of DFU must be predicted at an early stage to improve patient prognosis and outcomes. In this regard, emerging evidence suggests that inflammation-related markers play a significant role in DFU. One such potential marker, the monocyte-lymphocyte ratio (MLR), has not been extensively studied in relation to DFU. This study aimed to define a connection between MLR and DFU.

Methods

A cross-sectional study was conducted using National Health and Nutrition Examination Survey (NHANES) data from 1999 to 2004. DFU was defined based on survey questionnaires assessing the presence of nonhealing ulcers in the lower extremities for more than 4 weeks in diabetes patients. The MLR was calculated as the ratio of the monocyte count to the lymphocyte count, which was directly obtained from laboratory data files. Logistic regression analysis was performed to assess the relationship between the MLR and DFU. Stratified analysis according to age, sex, body mass index, blood glucose, hemoglobin, and glycated hemoglobin categories was conducted, and multiple imputations were applied to missing data.

Results

In total, 1246 participants were included; the prevalence of DFU was 9.4% (117/1246). A multivariable regression model revealed a significant association between DFU and a 0.1 unit increase in MLR after adjusting for all covariates (adjusted odds ratio=1.16, 95% confidence interval: 1.02-1.33). Subgroup analyses revealed consistent findings regarding the impact of MLR on the presence of DFU (p > 0.05).

Conclusion

MLR is significantly associated with DFU in diabetes patients, and can be used as one of the indicators for predicting the occurrence of DFU. MLR assessment may be a valuable component in the follow-up of patients with diabetes.

Immunomodulation with AM3 and antioxidants creates an adequate framework for skin repair and decreases the monocyte proinflammatory stage in smoker women

Smoking has been considering a crucial factor in promoting skin and systemic aging that is associated with the development of a low-level, systemic, chronic inflammation known as "inflammaging" in which monocytes play a pivotal role. Our aim was to investigate the effects of AM3 plus antioxidants vs placebo in the activation status, function of monocytes and cutaneous aging parameters in healthy smoker middle-aged women. A total of 32 women were 1:1 randomly assigned to AM3 plus antioxidants or placebo for three months. Peripheral mononuclear blood cells and cutaneous biopsy were obtained and flow cytometry and immunohistological studies, respectively, were performed before and after the treatment. AM3 plus antioxidants treatment compared with placebo significantly reduced the monocyte production of the proinflammatory interleukin 1 (IL-1), tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) cytokines as well as increased the regulatory IL-10 in middle-aged smoker women. Furthermore, AM3 and antioxidants did not modify ROS production by monocytes and granulocytes but increased their phagocytic activity. The active combination also stimulated a significative increase in reticular dermis depth as well as an increase in the expression of CD117 and CD31. Thus, AM3 and antioxidants treatment reduces the systemic proinflammatory monocyte disturbance of heathy smoker middle-aged women and encourage skin repair mechanisms.

Dermal features derived from optoacoustic tomograms via machine learning correlate microangiopathy phenotypes with diabetes stage

Skin microangiopathy has been associated with diabetes. Here we show that skin-microangiopathy phenotypes in humans can be correlated with diabetes stage via morphophysiological cutaneous features extracted from raster-scan optoacoustic mesoscopy (RSOM) images of skin on the leg. We obtained 199 RSOM images from 115 participants (40 healthy and 75 with diabetes), and used machine learning to segment skin layers and microvasculature to identify clinically explainable features pertaining to different depths and scales of detail that provided the highest predictive power. Features in the dermal layer at the scale of detail of 0.1-1 mm (such as the number of junction-to-junction branches) were highly sensitive to diabetes stage. A 'microangiopathy score' compiling the 32 most-relevant features predicted the presence of diabetes with an area under the receiver operating characteristic curve of 0.84. The analysis of morphophysiological cutaneous features via RSOM may allow for the discovery of diabetes biomarkers in the skin and for the monitoring of diabetes status.

Transdermal wires for improved integration in vivo

Alternative engineering approaches have led the design of implants with controlled physical features to minimize adverse effects in biological tissues. Similar efforts have focused on optimizing the design features of percutaneous VAD drivelines with the aim to prevent infection, omitting however a thorough look on the implant-skin interactions that govern local tissue reactions. Here, we utilized an integrated approach for the biophysical modification of transdermal implants and their evaluation by chronic sheep implantation in comparison to the standard of care VAD drivelines. We developed a novel method for the transfer of breath topographical features on thin wires with modular size. We examined the impact of implant's diameter, surface topography, and chemistry on macroscopic, histological, and physical markers of inflammation, fibrosis, and mechanical adhesion. All implants demonstrated infection-free performance. The fibrotic response was enhanced by the increasing diameter of implants but not influenced by their surface properties. The implants of small diameter promoted mild inflammatory responses with improved mechanical adhesion and restricted epidermal downgrowth, in both silicone and polyurethane coated transdermal wires. On the contrary, the VAD drivelines with larger diameter triggered severe inflammatory reactions with frequent epidermal downgrowth. We validated these effects by quantifying the infiltration of macrophages and the level of vascularization in the fibrotic zone, highlighting the critical role of size reduction for the benign integration of transdermal implants with skin. This insight on how the biophysical properties of implants impact local tissue reactions could enable new solutions on the transdermal transmission of power, signal, and mass in a broad range of medical devices.

Topically-applied collagen-binding serum albumin-fused interleukin-4 modulates wound microenvironment in non-healing wounds

Non-healing wounds have a negative impact on quality of life and account for many cases of amputation and even early death among patients. Diabetic patients are the predominate population affected by these non-healing wounds. Despite the significant clinical demand, treatment with biologics has not broadly impacted clinical care. Interleukin-4 (IL-4) is a potent modulator of the immune system, capable of skewing macrophages towards a pro-regeneration phenotype (M2) and promoting angiogenesis, but can be toxic after frequent administration and is limited by its short half-life and low bioavailability. Here, we demonstrate the design and characterization of an engineered recombinant interleukin-4 construct. We utilize this collagen-binding, serum albumin-fused IL-4 variant (CBD-SA-IL-4) delivered in a hyaluronic acid (HA)-based gel for localized application of IL-4 to dermal wounds in a type 2 diabetic mouse model known for poor healing as proof-of-concept for improved tissue repair. Our studies indicate that CBD-SA-IL-4 is retained within the wound and can modulate the wound microenvironment through induction of M2 macrophages and angiogenesis. CBD-SA-IL-4 treatment significantly accelerated wound healing compared to native IL-4 and HA vehicle treatment without inducing systemic side effects. This CBD-SA-IL-4 construct can address the underlying immune dysfunction present in the non-healing wound, leading to more effective tissue healing in the clinic.

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.

Advanced polymer hydrogels that promote diabetic ulcer healing: mechanisms, classifications, and medical applications

Diabetic ulcers (DUs) are one of the most serious complications of diabetes mellitus. The application of a functional dressing is a crucial step in DU treatment and is associated with the patient's recovery and prognosis. However, traditional dressings with a simple structure and a single function cannot meet clinical requirements. Therefore, researchers have turned their attention to advanced polymer dressings and hydrogels to solve the therapeutic bottleneck of DU treatment. Hydrogels are a class of gels with a three-dimensional network structure that have good moisturizing properties and permeability and promote autolytic debridement and material exchange. Moreover, hydrogels mimic the natural environment of the extracellular matrix, providing suitable surroundings for cell proliferation. Thus, hydrogels with different mechanical strengths and biological properties have been extensively explored as DU dressing platforms. In this review, we define different types of hydrogels and elaborate the mechanisms by which they repair DUs. Moreover, we summarize the pathological process of DUs and review various additives used for their treatment. Finally, we examine the limitations and obstacles that exist in the development of the clinically relevant applications of these appealing technologies. This review defines different types of hydrogels and carefully elaborate the mechanisms by which they repair diabetic ulcers (DUs), summarizes the pathological process of DUs, and reviews various bioactivators used for their treatment.

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.

Preparation of therapy-grade extracellular vesicles from adipose tissue to promote diabetic wound healing

Background: Treatment of diabetic wounds is a major challenge in clinical practice. Extracellular vesicles (EVs) from adipose-derived stem cells have shown effectiveness in diabetic wound models. However, obtaining ADSC-EVs requires culturing vast numbers of cells, which is hampered by the need for expensive equipment and reagents, extended time cost, and complicated procedures before commercialization. Therefore, methods to extract EVs from discarded tissue need to be developed, for immediate application during surgery. For this reason, mechanical, collagenase-digestive, and constant in-vitro-collective methods were designed and compared for preparing therapy-grade EVs directly from adipose tissue. Methods: Characteristics and quantities of EVs were detected by transmission electron microscopy, nanoparticle tracking analysis, and Western blotting firstly. To investigate the biological effects of EVs on diabetic wound healing, angiogenesis, proliferation, migration, and inflammation-regulation assays were then evaluated in vitro, along with a diabetic wound healing mouse model in vivo. To further explore the potential therapeutic mechanism of EVs, miRNA expression profile of EVs were also identified and analyzed. Results: The adipose tissue derived EVs (AT-EVs) were showed to qualify ISEV identification by nanoparticle tracking analysis and Western blotting and the AT-EVs yield from three methods was equal. EVs also showed promoting effects on biological processes related to diabetic wound healing, which depend on fibroblasts, keratinocytes, endothelial cells, and macrophages both in vitro and in vivo. We also observed enrichment of overlapping or unique miRNAs originate from different types of AT-EVs associated with diabetic wound healing for further investigation. Conclusion: After comparative analyses, a mechanical method was proposed for preparing immediate clinical applicable EVs from adipose tissue that would result in reduced preparation time and lower cost, which could have promising application potential in treating diabetic wounds.

Fibronectin in hyperglycaemia and its potential use in the treatment of diabetic foot ulcers: A review

Metabolism of fibronectin, the protein that plays a key role in the healing of wounds, is changed in the patients with diabetes mellitus. Fibronectin can interact with other proteins and proteoglycans and organise them to form the extracellular matrix, the basis of the granulation tissue in healing wounds. However, diabetic foot ulcers (DFUs) suffer from inadequate deposition of this protein. Degradation prevails over fibronectin synthesis in the proteolytic inflammatory environment in the ulcers. Because of the lack of fibronectin in the wound bed, the assembly of the extracellular matrix and the deposition of the granulation tissue cannot be started. A number of methods have been designed that prevents fibronectin degradation, replace lacking fibronectin or support its formation in non-healing wounds in animal models of diabetes. The aim of this article is to review the metabolism of fibronectin in DFUs and to emphasise that it would be useful to pay more attention to fibronectin matrix assembly in the ulcers when laboratory methods are translated to clinical practice.

Low Temperature Plasma Jet Affects Acute Skin Wounds in Diabetic Mice Through Reactive Components

As a common complication of diabetes, diabetic foot ulcers serious affect the life quality even lead to amputation if it's not properly treated. In this paper, we developed a Low Temperature Plasma Jet (LTPJ) system for treating diabetic foot ulcers on streptozotocin-induced diabetic mice. This system generates time-dependent reactive nitrogen and oxygen species (RNOS), which have temperature below 40°C. The wound area of normal mice was significantly reduced after LTPJ treatment. Histological and immunohistochemistry analysis showed faster deposition of collagen and more vessel formation both in plasma-treated normal and diabetic mice on Day 3. However, diabetic wounds showed poor collagen deposition and angiogenesis on Day 8, which might be the reason of slow wound healing. Reactive nitrogen species (RNS) that generated by LTPJ can promote endogenous nitric oxide (NO) production in diabetic wounds, thus promoting inflammation, stromal deposition, angiogenesis, cell proliferation and remodeling, while excess reactive oxygen species (ROS) will exacerbate oxidative stress in wound tissues of diabetic mice. In conclusion, LTPJ improved acute wound healing in normal mice, increased collagen deposition and angiogenesis in initial diabetic wound healing, but had no significant effect on diabetic wound healing rate.

HA PEGylated Filler in Association with an Infrared Energy Device for the Treatment of Facial Skin Aging: 150 Day Follow-Up Data Report

BACKGROUND

The face is the area most exposed to the normal course of skin aging, both intrinsically and extrinsically. The aim of the study was to evaluate the cellular and clinical response of a therapeutic protocol aimed at countering facial skin aging.

MATERIALS AND METHODS

Twenty female patients with facial skin laxity and photodamage underwent combined therapy including mesotherapy using non-cross-linked hyaluronic acid with calcium hydroxyapatite and an infrared energy-based device treatment with subsequent implementation of PEG-cross-linked hyaluronic acid soft tissue fillers. To evaluate the benefits, patients underwent histological, immunological, and biomechanical evaluations before the treatment and at 21 and 150 days after the treatment.

RESULTS

The histological results at 21 days and 150 days after the procedure showed an increase in the number of fibroblasts and angiogenesis. As for the immunological aspect, it was shown that the treatment has an immunomodulating action, avoiding the activation of CD4 and CD8 cells. Biomechanical data showed that, at 150 days after treatment, the average changes in skin elasticity increased by 72% and the skin hydration increased by 49%.

CONCLUSIONS

A combination of an infrared energy-based device treatment with both non-cross-linked hyaluronic acid and novel PEG-cross-linked hyaluronic acid leads to numerous positive cutaneous changes after histological, immunological, and biomechanical evaluations.

A desiccation compound as a biofilm- and necrosis-removing agent: a case series

Objective:

A new compound, Debrichem (DEBx Medical BV, the Netherlands), a topical desiccation agent (TDA), is an active gel that contains an acidic species with a potent hygroscopic action. When in contact with microorganisms and necrosis, rapid desiccation and carbonisation of the proteins in these microorganisms, as well as of the extracellular matrix of biofilms and necrosis, occurs. The resulting ‘precipitate’ rapidly dislodges from the wound bed, resulting in a clean wound which granulates, which is a prerequisite for healing by secondary intention.

Method:

In a retrospective study, a series of mostly large and hard-to-heal lesions of different aetiologies were treated with a one-time application of the TDA, followed by weekly dressing changes.

Results:

Of the total of 54 lesions included in this case series, 22 were diagnosed as venous leg ulcers (VLUs), 20 as diabetic foot ulcers (DFUs), nine as post-traumatic, hard-to-heal lesions, two as vascular ulcers and one as an ischaemic ulcer. All of the VLUs, 75% of the DFUs and all of the other lesions reached complete granulation.

Conclusion:

The use of a TDA may contribute to the consistent, fast and easy removal of both biofilms and necrosis, and hence to wound healing.

Murine macrophages or their secretome delivered in alginate dressings enhance impaired wound healing in diabetic mice

Diabetic foot ulceration is a devastating diabetic complication with unmet needs. We explored the efficacy of calcium-crosslinked alginate dressings in topically delivering primary macrophages and their secretome to diabetic wounds. The alginate bandages had a microporous structure that enabled even cell loading with prolonged cell survival and egress following wound placement. In vitro experiments showed that we could successfully differentiate and polarize primary murine bone marrow derived monocytes into M0, M1, M2a and M2c defined states with distinct gene expression, surface protein and secretome profiles. The primary macrophages were delivered in the bandages, migrated within the wounds and were still present for as long as 16 days post-injury. In wounds of db/db mice, treatment with all macrophage subtypes and their secretome, when compared to control, accelerated wound healing. Bulk RNA sequencing analysis and multiplex protein quantification of wound lysates revealed that M2c macrophages conditioned media had the most impact in wound healing affecting processes like neurogenesis, while M1 conditioned media promoted keratinization and epidermal differentiation. Collectively, our results indicate that alginate dressings can serve as a delivery platform for topical treatment of diabetic wounds and that conditioned media from distinctly polarized macrophages is equally or more effective than their parental cells in advancing wound healing and could therefore be a promising and technically advantageous alternative to cell therapy.

Effect of a Topical Gel Based on Adelmidrol + Trans-Traumatic Acid in the Treatment of Diabetic Foot Ulcers: An Open-Label Study

BACKGROUND

Diabetic foot ulceration is a severe complication of diabetes characterized by chronic inflammation and impaired wound healing. This study aimed to evaluate the effect of a medical device gel based on adelmidrol + trans-traumatic acid in the healing process of diabetic foot ulcers.

METHODS

Thirty-seven diabetic patients with foot ulcers of mild/moderate grade were treated with the gel daily for 4 weeks on the affected area. The following parameters were evaluated at baseline and weekly: 1) wound area, measured by drawing a map of the ulcer and then calculated with photo editing software tools, and 2) clinical appearance of the ulcer, assessed by recording the presence/absence of dry/wet necrosis, infection, fibrin, neoepithelium, exudate, redness, and granulation tissue.

RESULTS

Topical treatment led to progressive healing of diabetic foot ulcers with a significant reduction of the wound area and an improvement in the clinical appearance of the ulcers. No treatment-related adverse events were observed.

CONCLUSIONS

The results of this open-label study show the potential benefits of adelmidrol + trans-traumatic acid topical administration to promote reepithelialization of diabetic foot ulcers. Further studies are needed to confirm the observed results.

Exosomes Derived from Epidermal Stem Cells Improve Diabetic Wound Healing

Diabetic foot ulceration is a major diabetic complication with unmet needs. We investigated the efficacy of epidermal stem cells (ESCs) and ESCs-derived exosomes (ESCs-Exo) in improving impaired diabetic wound healing and their mechanisms of action. In vitro experiments showed that ESCs-Exo enhanced the proliferation and migration of diabetic fibroblasts and macrophages (Mφ), and promoted alternative or M2 Mφ polarization. In wounds of db/db mice, treatment with both ESCs and ESCs-Exo, when compared to fibroblast exosomes (FB-Exo) and PBS control, accelerated wound healing by decreasing inflammation, augmenting wound cell proliferation, stimulating angiogenesis and inducing M2 Mφ polarization. Multiplex protein quantification of wound lysates revealed TGFβ signaling influenced by ESCs-Exo. High-throughput sequencing of small RNAs contained in the ESCs-Exo showed higher proportions of miRNAs when compared to FB-Exo. In silico functional analysis demonstrated that the ESCs-Exo-miRNAs target genes were primarily involved in homeostatic processes and cell differentiation and highlighted regulatory control of PI3K/AKT and TGFβ signaling pathways. This was also validated in vitro. Collectively, our results indicate that ESCs and ESCs-Exo are equally effective in promoting impaired diabetic wound healing and that ESCs-Exo treatment may be a promising and technically advantageous alternative to stem cell therapies.

The Role of Oxidative Stress, Inflammation, and Advanced Glycation End Product in Skin Manifestations of Diabetes Mellitus

Diabetes mellitus is a metabolic disorder caused by an increase in insulin resistance, a decrease in insulin production, or both of them, resulting in a high level of blood glucose or hyperglycemia. An uncontrolled state of DM may cause complications, namely skin disorder. One or more skin disorders are found amongst 74% of T2DM patients, with the highest percentage is dry skin (47%), followed by infection (10%), diabetic hand (5%), hair loss and diabetic dermopathy (each 4%). In DM, the state of hyperglycemia and production of advanced glycaemic end-products (AGEs) profoundly impact skin changes. In the pathological pathway, AGEs induce oxidative stress and inflammation. Nonetheless, AGEs level is higher in T2DM patients compared to non- T2DM people. This is caused by hyperglycemia and oxidative stress. Binding between AGEs and receptor of AGEs (RAGE) promotes pathway of oxidative stress and inflammation cascade via mitogen- activated protein kinases (MAPK), nuclear factor-k-light-chain-enhancer of activated β cells (NF-kβ), interleukin- 6 (IL-6), tumor necrosis factor-α (TNF-α), expression of intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 2 (VCAM-2) pathway which furtherly effectuates DM complication including skin disorders.

Skin Wound Healing: Normal Macrophage Function and Macrophage Dysfunction in Diabetic Wounds

Macrophages play a prominent role in wound healing. In the early stages, they promote inflammation and remove pathogens, wound debris, and cells that have apoptosed. Later in the repair process, they dampen inflammation and secrete factors that regulate the proliferation, differentiation, and migration of keratinocytes, fibroblasts, and endothelial cells, leading to neovascularisation and wound closure. The macrophages that coordinate this repair process are complex: they originate from different sources and have distinct phenotypes with diverse functions that act at various times in the repair process. Macrophages in individuals with diabetes are altered, displaying hyperresponsiveness to inflammatory stimulants and increased secretion of pro-inflammatory cytokines. They also have a reduced ability to phagocytose pathogens and efferocytose cells that have undergone apoptosis. This leads to a reduced capacity to remove pathogens and, as efferocytosis is a trigger for their phenotypic switch, it reduces the number of M2 reparative macrophages in the wound. This can lead to diabetic foot ulcers (DFUs) forming and contributes to their increased risk of not healing and becoming infected, and potentially, amputation. Understanding macrophage dysregulation in DFUs and how these cells might be altered, along with the associated inflammation, will ultimately allow for better therapies that might complement current treatment and increase DFU’s healing rates.

Effects of advanced glycation end products on neutrophil migration and aggregation in diabetic wounds

Increased accumulation of advanced glycation end products (AGEs) in diabetic skin is closely related to delayed wound healing. Studies have shown that the concentration of AGEs is elevated in the skin tissues and not subcutaneous tissues in refractory diabetic wounds, which suggests there may be a causal relationship between the two. In the present study, in vitro experiments revealed that AGEs activated neutrophils, and the migratory and adhesive functions of neutrophils decreased once AGE levels reached a certain threshold. Different levels of AGE expression differentially affected the function of neutrophils. Messenger RNA (mRNA) sequencing analysis combined with real-time polymerase chain reaction (PCR) showed that poliovirus receptor (PVR/CD155) and CTNND1, which play a role in migration- and adhesion-related signaling pathways, were decreased following AGE stimulation. Consequently, neutrophils cannot effectively stimulate the formation of the inflammatory belt needed to remove necrotic tissues and defend against foreign microorganisms within diabetic chronic wounds. In addition, this phenomenon may be related to the differential accumulation of AGEs in different layers of the skin.

Deep learning differentiates between healthy and diabetic mouse ears from optical coherence tomography angiography images

We trained a deep learning algorithm to use skin optical coherence tomography (OCT) angiograms to differentiate between healthy and type 2 diabetic mice. OCT angiograms were acquired with a custom‐built OCT system based on an akinetic swept laser at 1322 nm with a lateral resolution of ∼13 μm and using split‐spectrum amplitude decorrelation. Our data set consisted of 24 stitched angiograms of the full ear, with a size of approximately 8.2 × 8.2 mm, evenly distributed between healthy and diabetic mice. The deep learning classification algorithm uses the ResNet v2 convolutional neural network architecture and was trained on small patches extracted from the full ear angiograms. For individual patches, we obtained a cross‐validated accuracy of 0.925 and an area under the receiver operating characteristic curve (ROC AUC) of 0.974. Averaging over multiple patches extracted from each ear resulted in the correct classification of all 24 ears.

The role of the microbiome in diabetes mellitus

The microbiome is greatly significant for immune system development and homeostasis. Dysbiosis in gut microbial composition and function is linked to immune responses and the development of metabolic diseases, including diabetes mellitus (DM). However, skin microbiome changes in diabetic patients and their role in DM are poorly elucidated. In this review, we summarize recent findings about the association between the gut and skin microbiota and DM, highlighting their roles in the proinflammatory status of DM. Moreover, although there is evidence that the connection between the gut and skin causes the same activated innate immune response, additional studies are needed to explore the mechanism. These findings might inform future DM prevention, diagnosis and treatment.

Mast Cells in Diabetes and Diabetic Wound Healing

Mast cells (MCs) are granulated, immune cells of the myeloid lineage that are present in connective tissues. Apart from their classical role in allergies, MCs also mediate various inflammatory responses due to the nature of their secretory products. They are involved in important physiological and pathophysiological responses related to inflammation, chronic wounds, and autoimmune diseases. There are also indications that MCs are associated with diabetes and its complications. MCs and MC-derived mediators participate in all wound healing stages and are involved in the pathogenesis of non-healing, chronic diabetic foot ulcers (DFUs). More specifically, recent work has shown increased degranulation of skin MCs in human diabetes and diabetic mice, which is associated with impaired wound healing. Furthermore, MC stabilization, either systemic or local at the skin level, improves wound healing in diabetic mice. Understanding the precise role of MCs in wound progression and healing processes can be of critical importance as it can lead to the development of new targeted therapies for diabetic foot ulceration, one of the most devastating complications of diabetes.

Selected conditions associated with an increased incidence of incisional hernia: A review of molecular biology

BACKGROUND

Incisional hernias (IH) following a laparotomy, on average, occur in 10-20% of patients, however, little is known about its molecular basis. Thus, a better understanding of the molecular mechanisms could lead to the identification of key target(s) to intervene pre-and post-operatively.

METHODS

We examined the current literature describing the molecular mechanisms of IH and overlap these factors with smoking, abdominal aortic aneurysm, obesity, diabetes mellitus, and diverticulitis.

RESULTS

The expression levels of collagen I and III, matrix metalloproteinases, and tissue inhibitors of metalloproteases are abnormal in the extracellular matrix (ECM) of IH patients and ECM disorganization has an overlap with these comorbid conditions.

CONCLUSION

Understanding the pathophysiology of IH development and associated risk factors will allow physicians to identify patients that may be at increased risk for IH and to possibly act preemptively to decrease the incidence of IH.

Wound healing activity of Pimpinella anisum methanolic extract in streptozotocin-induced diabetic rats

OBJECTIVE

To assess the wound healing potential of Pimpinella anisum on cutaneous wounds in diabetic rats.

METHOD

Full-thickness excisional wounds were made on the back of male, Sprague-Dawley rats with diabetes. The rats were randomly allocated into four treatment groups: 1ml basal cream; tetracycline (3%); Pimpinella anisum 10% for 14 days; and a control group. At days seven, 14 and 21 post-injury, five animals of each group were euthanised, and wounds were assessed through gross, histopathological and oxidant/antioxidant evaluations. Additionally, the dry matter and hydroxyproline contents of the skin samples were measured.

RESULTS

A total of 60 rats were used in the study. A significant decrease in the wound size was observed in treated animals with Pimpinella anisum compared with other groups during the experiment. Additionally, treatment with Pimpinella anisum decreased the number of lymphocytes and improved the number of fibroblasts at the earlier stages and increased a number of fibrocytes at the later stages of wound healing. Other parameters such as re-epithelialisation, tissue alignment, greater maturity of collagen fibres and large capillary-sized blood vessels revealed significant changes when compared with the control. Pimpinella anisum significantly reverted oxidative changes of total antioxidant capacity, malondialdehyde and glutathione peroxidase induced by diabetic wounds (p<0.05). Furthermore, it significantly increased the dry matter and hydroxyproline contents at various stages of wound healing (p<0.05).

CONCLUSION

The present study showed that application of Pimpinella anisum extract promotes wound healing activity in diabetic rats. The wound-healing property of Pimpinella anisum can be attributed to the phytoconstituents present in the plant.

Enhancement of cellular activity in hyperglycemic mice dermal wounds dressed with chitosan-alginate membranes

The use of specially designed wound dressings could be an important alternative to facilitate the healing process of wounds in the hyperglycemic state. Biocompatible dressings combining chitosan and alginate can speed up wound healing by modulating the inflammatory phase, stimulating fibroblast proliferation, and aiding in remodeling phases. However, this biomaterial has not yet been explored in chronic and acute lesions of diabetic patients. The aim of this study was to evaluate the effect of topical treatment with a chitosan-alginate membrane on acute skin wounds of hyperglycemic mice. Diabetes mellitus was induced by streptozotocin (60 mg · kg^-1 · day^-1 for 5 days, intraperitoneally) and the cutaneous wound was performed by removing the epidermis using a surgical punch. The results showed that after 10 days of treatment the chitosan and alginate membrane (CAM) group exhibited better organization of collagen fibers. High concentrations of interleukin (IL)-1α, IL-1β, granulocyte colony-stimulating factor (G-CSF), and tumor necrosis factor-alpha (TNF-α) were detected in the first and second days of treatment. G-CSF and TNF-α level decreased after 5 days, as well as the concentrations of TNF-α and IL-10 compared with the control group (CG). In this study, the inflammatory phase of cutaneous lesions of hyperglycemic mice was modulated by the use of CAM, mostly regarding the cytokines IL-1α, IL-1β, TNF-α, G-CSF, and IL-10, resulting in better collagen III deposition. However, further studies are needed to better understand the healing stages associated with CAM use.

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.

Obesity-associated insulin resistance adversely affects skin function

The aim of this study was to identify changes in skin function associated with obesity and the mechanisms underlying these changes. Functional changes and gene expression in skin were investigated in C57BL/6J mice fed either a control or high-fat diet (HFD). The insulin responsiveness of the skin and skeletal muscle was also evaluated. The effects of inhibiting insulin signaling and altered glucose concentration on skin function-associated molecules and barrier function were analyzed in keratinocytes. HFD-fed mice were not only severely obese, but also exhibited impaired skin barrier function and diminished levels of glycerol transporter aquaporin-3, keratins, and desmosomal proteins involved in maintaining skin structure. Moreover, the expression of cell cycle regulatory molecules was altered. Insulin signaling was attenuated in the skin and skeletal muscle of HFD-fed mice. In keratinocytes, inhibition of insulin signaling leads to decreased keratin expression and diminished barrier function, and higher glucose concentrations increased the expression of CDK inhibitor 1A and 1C, which are associated with cell-cycle arrest. Obesity-associated impairment of skin function can be attributed to structural fragility, abnormal glycerol transport, and dysregulated proliferation of epidermal cells. These alterations are at least partly due to cutaneous insulin resistance and hyperglycemia.

Topical Application of a Mast Cell Stabilizer Improves Impaired Diabetic Wound Healing

Impaired wound healing in the diabetic foot is a major problem often leading to amputation. Mast cells have been shown to regulate wound healing in diabetes. We developed an indole-carboxamide type mast cell stabilizer, MCS-01, which proved to be an effective mast cell degranulation inhibitor in vitro and can be delivered topically for prolonged periods through controlled release by specifically designed alginate bandages. In diabetic mice, both pre- and post-wounding, topical MCS-01 application accelerated wound healing comparable to that achieved with systemic mast cell stabilization. Moreover, MCS-01 altered the macrophage phenotype, promoting classically activated polarization. Bulk transcriptome analysis from wounds treated with MCS-01 or placebo showed that MCS-01 significantly modulated the mRNA and microRNA profile of diabetic wounds, stimulated upregulation of pathways linked to acute inflammation and immune cell migration, and activated the NF-κB complex along with other master regulators of inflammation. Single-cell RNA sequencing analysis of 6,154 cells from wounded and unwounded mouse skin revealed that MCS-01 primarily altered the gene expression of mast cells, monocytes, and keratinocytes. Taken together, these findings offer insights into the process of diabetic wound healing and suggest topical mast cell stabilization as a potentially successful treatment for diabetic foot ulceration.

[Role of the microbiome in chronic wounds]

BACKGROUND

The microbiome, collective microbial life in defined areas of the body, is of great importance.

OBJECTIVE

What is the significance of the wound microbiome in the treatment of chronic wounds? Which interactions exist with other microbiomes and which conclusions can be drawn for wound management?

MATERIALS AND METHODS

Swabs or debridement samples from wounds were analysed for microbial growth by culture or gene-based techniques. The genetic results are used to determine the wound microbiome. The pathogens were evaluated according to proportion of different species and related to different factors like type and location of wound, disease and underlying illnesses and to define the wound microbiome.

RESULTS

In comparison with conventional microbiological detection methods the wound microbiome comprises many more types and quantities of species. The wound microbiome is related to skin microbiome showing complex and time-dependent composition, as well as inter- and intraindividual differences. Diabetic wounds exhibit disease-related changes, e.g. staphylococcal species dominate whereas streptococcal species dominate in nondiabetic wounds.

CONCLUSIONS

The analysis of wound microbiome is still at an early stage; however it has already been shown that in hemodynamic disorders there are disease-specific relationships with the wound microbiome, which can also provide clues about the course of the disease. Phenomena from the skin microbiome should also be effective in wounds. In this context modern antimicrobial treatment options beyond conventional chemotherapy like colonization modulation become possible.

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.

Descriptive vs mechanistic scientific approach to study wound healing and its inhibition: Is there a value of translational research involving human subjects?

The clinical field of wound healing is challenged by numerous hurdles. Not only are wound-healing disorders complex and multifactorial, but the corresponding patient population is diverse, often elderly and burdened by multiple comorbidities such as diabetes and cardiovascular disease. The care of such patients requires a dedicated, multidisciplinary team of physicians, surgeons, nurses and scientists. In spite of the critical clinical need, it has been over 15 years since a treatment received approval for efficacy by the FDA in the United States. Among the reasons contributing to this lack of effective new treatment modalities is poor understanding of mechanisms that inhibit healing in patients. Additionally, preclinical models do not fully reflect the disease complexity of the human condition, which brings us to a paradox: if we are to use a "mechanistic" approach that favours animal models, we can dissect specific mechanisms using advanced genetic, molecular and cellular technologies, with the caveat that it may not be directly applicable to patients. Traditionally, scientific review panels, for either grant funding or manuscript publication purposes, favour such "mechanistic" approaches whereby human tissue analyses, deemed "descriptive" science, are characterized as a "fishing expedition" and are considered "fatally flawed." However, more emerging evidence supports the notion that the use of human samples provides significant new knowledge regarding the molecular and cellular mechanisms that control wound healing and contribute to inhibition of the process in patients. Here, we discuss the advances, benefits and challenges of translational research in wound healing focusing on human subject research.

In vivo imaging the motility of monocyte/macrophage during inflammation in diabetic mice

Diabetes, as a chronic metabolic disease, can impair the immune function of monocytes/macrophages (MMs). However, it is unclear how MM immune response to inflammation with the development of diabetes, and whether immune response around the inflammatory foci depends on the depth in tissue. Footpad provides a classical physiological site for monitoring cellular behavior during inflammation, but limited to the superficial dermis due to the strong scattering of footpad. Herein, we used confocal microscopy to monitor the motility of MMs in deeper tissue around inflammatory foci with the development of type 1 diabetic (T1D) mice through a switchable footpad skin optical clearing window. Delayed-type hypersensitivity (DTH) model was elicited on the footpad of T1D. Results demonstrated that progressive T1D led to the gradually potentiated MM recruitment and increased expression of monocyte chemoattractant protein-1 during DTH, but MM migration displacement, motion velocity and motility coefficient were significantly attenuated. Besides, MMs from the deeper dermis had a much larger migration displacement than those from superficial dermis at early stages of DTH but an opposite tendency at late stages for non-T1D, while progressive T1D obscured this difference gradually. This study will be helpful for investigating the influences of progressive metabolic diseases on immune response. MM motion trajectory at depth of superficial dermis and the deeper dermis at AOVA (heat-aggregated ovalbumin)-4 hours and AOVA-72 hours on non-T1D (A) and T1D-4 weeks (B). Mean motility coefficient (C) at the 2 depths. Data were pooled from 6 mice per group. *P < .05 and **P < .01 compared among different T1D disease durations. #P < .05 compared between different depths.

Whole-genome expression analyses of type 2 diabetes in human skin reveal altered immune function and burden of infection

Skin disorders are among most common complications associated with type 2 diabetes mellitus (T2DM). Although T2DM patients are known to have increased risk of infections and other T2DM-related skin disorders, their molecular mechanisms are largely unknown. This study aims to identify dysregulated genes and gene networks that are associated with T2DM in human skin. We compared the expression profiles of 56,318 transcribed genes on 74 T2DM cases and 148 gender- age-, and race-matched non-diabetes controls from the Genotype-Tissue Expression (GTEx) database. RNA-Sequencing data indicates that diabetic skin is characterized by increased expression of genes that are related to immune responses (CCL20, CXCL9, CXCL10, CXCL11, CXCL13, and CCL18), JAK/STAT signaling pathway (JAK3, STAT1, and STAT2), tumor necrosis factor superfamily (TNFSF10 and TNFSF15), and infectious disease pathways (OAS1, OAS2, OAS3, and IFIH1). Genes in cell adhesion molecules pathway (NCAM1 and L1CAM) and collagen family (PCOLCE2 and COL9A3) are downregulated, suggesting structural changes in the skin of T2DM. For the first time, to the best of our knowledge, this pioneer analytic study reports comprehensive unbiased gene expression changes and dysregulated pathways in the non-diseased skin of T2DM patients. This comprehensive understanding derived from whole-genome expression profiles could advance our knowledge in determining molecular targets for the prevention and treatment of T2DM-associated skin disorders.

Impaired glyoxalase activity is associated with reduced expression of neurotrophic factors and pro-inflammatory processes in diabetic skin cells

Patients suffering from type II diabetes develop several skin manifestations including cutaneous infections, diabetic dermopathy, diabetic bullae and acanthosis nigricans. Diabetic micro- and macroangiopathy as well as diabetic neuropathy are believed to play a crucial role in the development of diabetic skin disorders. A reduced cutaneous nerve fibre density was reported in diabetic subjects, which subsequently leads to impaired sensory nerve functions. Using an innervated skin model, we investigated the impact of human diabetic dermal fibroblasts and keratinocytes on porcine sensory neurons. Diabetic skin cells showed a reduced capacity to induce neurite outgrowth due to a decreased support with neurotrophic factors, such as NGF. Furthermore, diabetic keratinocytes displayed insulin resistance and increased expression of pro-inflammatory cytokines demonstrating the persistent effect of diabetes mellitus on human skin cells. Dysregulations were related to a significantly reduced glyoxalase enzyme activity in diabetic keratinocytes as experimentally reduced glyoxalase activity mimicked the increase in pro-inflammatory cytokine expression and reduction in NGF. Our results demonstrate an impaired crosstalk of diabetic skin cells and sensory neurons favouring hypo-innervation. We suggest that reduced methylglyoxal detoxification contributes to an impaired neurocutaneous interaction in diabetic skin.

Polydeoxyribonucleotide Improves Peripheral Tissue Oxygenation and Accelerates Angiogenesis in Diabetic Foot Ulcers

BACKGROUND

Polydeoxyribonucleotide (PDRN) is known to have anti-inflammatory and angiogenic effects and to accelerate wound healing. The aim of this study was to investigate whether PDRN could improve peripheral tissue oxygenation and angiogenesis in diabetic foot ulcers.

METHODS

This was a prospective randomized controlled clinical trial. Twenty patients with a non-healing diabetic foot ulcer were randomly distributed into a control group (n=10) and a PDRN group (n=10). Initial surgical debridement and secondary surgical procedures such as a split-thickness skin graft, primary closure, or local flap were performed. Between the initial surgical debridement and secondary surgical procedures, 0.9% normal saline (3 mL) or PDRN was injected for 2 weeks by the intramuscular (1 ampule, 3 mL, 5.625 mg, 5 days per week) and perilesional routes (1 ampule, 3 mL, 5.625 mg, 2 days per week). Transcutaneous oxygen tension (TcPO₂) was evaluated using the Periflux System 5000 with TcPO₂/CO₂ unit 5040 before the injections and on days 1, 3, 7, 14, and 28 after the start of the injections. A pathologic review (hematoxylin and eosin stain) of the debrided specimens was conducted by a pathologist, and vessel density (average number of vessels per visual field) was calculated.

RESULTS

Compared with the control group, the PDRN-treated group showed improvements in peripheral tissue oxygenation on day 7 (P<0.01), day 14 (P<0.001), and day 28 (P<0.001). The pathologic review of the specimens from the PDRN group showed increased angiogenesis and improved inflammation compared with the control group. No statistically significant difference was found between the control group and the PDRN group in terms of vessel density (P=0.094). Complete healing was achieved in every patient.

CONCLUSIONS

In this study, PDRN improved peripheral tissue oxygenation. Moreover, PDRN is thought to be effective in improving inflammation and angiogenesis in diabetic foot ulcers.

Metformin accelerates wound healing in type 2 diabetic db/db mice

Wound healing impairment is increasingly recognized to be a consequence of hyperglycemia-induced dysfunction of endothelial precursor cells (EPCs) in type 2 diabetes mellitus (T2DM). Metformin exhibits potential for the improvement of endothelial function and the wound healing process. However, the underlying mechanisms for the observed beneficial effects of metformin application remain to be completely understood. The present study assessed whether metformin, a widely used therapeutic drug for T2DM, may accelerate wound closure in T2DM db/db mice. Genetically hyperglycemic db/db mice were used as the T2DM model. Metformin (250 mg/kg/day; intragastric) was administered for two weeks prior to EPC collection and wound model creation in db/db mice. Wound healing was evaluated by alterations in the wound area and the number of platelet endothelial cell adhesion molecule-positive cells. The function of the isolated bone marrow-derived EPCs (BM-EPCs) was assessed by a tube formation assay. The number of circulating EPCs, and the levels of intracellular nitric oxide (NO) and superoxide (O₂⁻) were detected by flow cytometry. Thrombospondin-1 (TSP-1) expression was determined by western blot analysis. It was observed that treatment with metformin accelerated wound healing, improved angiogenesis and increased the circulating EPC number in db/db mice. In vitro, treatment with metformin reversed the impaired BM-EPC function reflected by tube formation, and significantly increased NO production while decreasing O₂⁻ levels in BM-EPCs from db/db mice. In addition, TSP-1 expression was markedly attenuated by treatment with metformin in cultured BM-EPCs. Metformin contributed to wound healing and improved angiogenesis in T2DM mice, which was, in part, associated with stimulation of NO, and inhibition of O₂⁻ and TSP-1 in EPCs from db/db mice.

A longitudinal study of the diabetic skin and wound microbiome

Background

Type II diabetes is a chronic health condition which is associated with skin conditions including chronic foot ulcers and an increased incidence of skin infections. The skin microbiome is thought to play important roles in skin defence and immune functioning. Diabetes affects the skin environment, and this may perturb skin microbiome with possible implications for skin infections and wound healing. This study examines the skin and wound microbiome in type II diabetes.

Methods

Eight type II diabetic subjects with chronic foot ulcers were followed over a time course of 10 weeks, sampling from both foot skin (swabs) and wounds (swabs and debrided tissue) every two weeks. A control group of eight control subjects was also followed over 10 weeks, and skin swabs collected from the foot skin every two weeks. Samples were processed for DNA and subject to 16S rRNA gene PCR and sequencing of the V4 region.

Results

The diabetic skin microbiome was significantly less diverse than control skin. Community composition was also significantly different between diabetic and control skin, however the most abundant taxa were similar between groups, with differences driven by very low abundant members of the skin communities. Chronic wounds tended to be dominated by the most abundant skin Staphylococcus, while other abundant wound taxa differed by patient. No significant correlations were found between wound duration or healing status and the abundance of any particular taxa.

Discussion

The major difference observed in this study of the skin microbiome associated with diabetes was a significant reduction in diversity. The long-term effects of reduced diversity are not yet well understood, but are often associated with disease conditions.

Curcumol Promotes Vascular Endothelial Growth Factor (VEGF)-Mediated Diabetic Wound Healing in Streptozotocin-Induced Hyperglycemic Rats

BACKGROUND Wound healing in chronic diabetic mellitus is mainly associated with the management of angiogenesis. The angiogenic mechanism of vascular endothelial growth factor (VEGF) has been widely studied in the context of diabetic ulcers. The aim of this study was to investigate the wound-healing potential of curcumol in streptozotocin-induced diabetic rats. MATERIAL AND METHODS Sixty male SD (Sprague Dawley) rats were purchased and randomly assigned into four groups: a control group and a model group treated with blank ointment, a high-dose curcumol group, and a low-dose curcumol group. The number of animals in each group was 15. Diabetes was induced by an intraperitoneal injection of streptozotocin. Two cutaneous wounds were incised at the dorsal region of all the experimental animals. Wound healing was assessed for all animal groups by observing the rate of wound closure. The expression of VEGF at the wound sites was studied by immunohistochemical staining to evaluate the vascular endothelial cell reaction. VEGF protein and related mRNA levels were analyzed by Western blotting and RT-PCR (reverse transcription-polymerase chain reaction). RESULTS Curcumol treatment significantly increased the rates of wound closure in treated animals, and hence wound healing was drastically enhanced for treatment groups compared to control groups. Histological observations and related mRNA and protein levels showed a higher VEGF expression in the treatment groups. CONCLUSIONS Our analyses clearly suggested that the observed enhancement in wound healing as a result of curcumol administration was attributable to VEGF-mediated angiogenesis.

Effects of insulin on the skin: possible healing benefits for diabetic foot ulcers

Diabetic foot ulcers affect 15-20 % of all diabetic patients and remain an important challenge since the available therapies have limited efficacy and some of the novel therapeutic approaches, which include growth factors and stem cells, are highly expensive and their safety remains to be evaluated. Despite its low cost and safety, the interest for topical insulin as a healing agent has increased only in the last 20 years. The molecular mechanisms of insulin signaling and its metabolic effects have been well studied in its classical target tissues. However, little is known about the specific effects of insulin in healthy or even diabetic skin. In addition, the mechanisms involved in the effects of insulin on wound healing have been virtually unknown until about 10 years ago. This paper will review the most recent advances in the cellular and molecular mechanisms that underlie the beneficial effects of insulin on skin wound healing in diabetes. Emerging evidence that links dysfunction of key cellular organelles, namely the endoplasmic reticulum and the mitochondria, to changes in the autophagy response, as well as the impaired wound healing in diabetic patients will also be discussed along with the putative mechanisms whereby insulin could regulate/modulate these alterations.

Painful neuropathy: Mechanisms

Painful neuropathy, like the other complications of diabetes, is a growing healthcare concern. Unfortunately, current treatments are of variable efficacy and do not target underlying pathogenic mechanisms, in part because these mechanisms are not well defined. Rat and mouse models of type 1 diabetes are frequently used to study diabetic neuropathy, with rats in particular being consistently reported to show allodynia and hyperalgesia. Models of type 2 diabetes are being used with increasing frequency, but the current literature on the progression of indices of neuropathic pain is variable and relatively few therapeutics have yet been developed in these models. While evidence for spontaneous pain in rodent models is sparse, measures of evoked mechanical, thermal and chemical pain can provide insight into the pathogenesis of the condition. The stocking and glove distribution of pain tantalizingly suggests that the generator site of neuropathic pain is found within the peripheral nervous system. However, emerging evidence demonstrates that amplification in the spinal cord, via spinal disinhibition and neuroinflammation, and also in the brain, via enhanced thalamic activity or decreased cortical inhibition, likely contribute to the pathogenesis of painful diabetic neuropathy. Several potential therapeutic strategies have emerged from preclinical studies, including prophylactic treatments that intervene against underlying mechanisms of disease, treatments that prevent gains of nociceptive function, treatments that suppress enhancements of nociceptive function, and treatments that impede normal nociceptive mechanisms. Ongoing challenges include unraveling the complexity of underlying pathogenic mechanisms, addressing the potential disconnect between the perceived location of pain and the actual pain generator and amplifier sites, and finding ways to identify which mechanisms operate in specific patients to allow rational and individualized choice of targeted therapies.

Mast Cells Regulate Wound Healing in Diabetes

Diabetic foot ulceration is a severe complication of diabetes that lacks effective treatment. Mast cells (MCs) contribute to wound healing, but their role in diabetes skin complications is poorly understood. Here we show that the number of degranulated MCs is increased in unwounded forearm and foot skin of patients with diabetes and in unwounded dorsal skin of diabetic mice (P < 0.05). Conversely, postwounding MC degranulation increases in nondiabetic mice, but not in diabetic mice. Pretreatment with the MC degranulation inhibitor disodium cromoglycate rescues diabetes-associated wound-healing impairment in mice and shifts macrophages to the regenerative M2 phenotype (P < 0.05). Nevertheless, nondiabetic and diabetic mice deficient in MCs have delayed wound healing compared with their wild-type (WT) controls, implying that some MC mediator is needed for proper healing. MCs are a major source of vascular endothelial growth factor (VEGF) in mouse skin, but the level of VEGF is reduced in diabetic mouse skin, and its release from human MCs is reduced in hyperglycemic conditions. Topical treatment with the MC trigger substance P does not affect wound healing in MC-deficient mice, but improves it in WT mice. In conclusion, the presence of nondegranulated MCs in unwounded skin is required for proper wound healing, and therapies inhibiting MC degranulation could improve wound healing in diabetes.

Impaired T-cell differentiation in diabetic foot ulceration

Foot ulceration is one of the most debilitating complications associated with diabetes, but its cause remains poorly understood. Several studies have been undertaken to understand healing kinetics or find possible therapies to enhance healing. However, few studies have been directed at understanding the immunological alterations that could influence wound healing in diabetes. In this study, we analysed the T-cell receptor (TCR) repertoire diversity in TCR-αβ⁺ T cells. We also analysed the distribution and phenotype of T cells obtained from the peripheral blood of healthy controls and diabetic individuals with or without foot ulcers. Our results showed that diabetic individuals, especially those with foot ulcers, have a significantly lower naive T-cell number and a poorer TCR-Vβ repertoire diversity. We also showed that the reduced TCR-Vβ repertoire diversity in diabetic individuals was mainly owing to the accumulation of effector T cells, the major source of tumour necrosis factor-α production, which was even more pronounced in patients with acute foot ulceration. Moreover, the expression of several inflammatory chemokine receptors was significantly reduced in diabetic patients. In conclusion, effector T-cell accumulation and TCR repertoire diversity reduction appear to precede the development of foot ulcers. This finding may open new immunological therapeutic possibilities and provide a new prognostic tool in diabetic wound care.

Skin disorders in diabetes mellitus: an epidemiology and physiopathology review

Skin disorders, usually neglected and frequently underdiagnosed among diabetic patients, are common complications and encounter a broad spectrum of disorders in both type 1 and type 2 diabetes mellitus (DM)-e.g. cutaneous infection, dry skin, pruritus. Skin disorders are highly associated with increased risk of important outcomes, such as skin lesions, ulcerations and diabetic foot, which can lead to major complications and revolve around multifactorial factors besides hyperglycemia and advanced glycation end products. Although diabetic's skin disorders are consistent in the literature, there is limited data regarding early-stage skin disorders in DM patients. Disease control, early-stage treatment (e.g. skin hydration, orthotic devices) and awareness can reduce morbidity of DM patients. Thus, better understanding of the burden of skin disorders in DM patients may raise awareness on prevention and management. Therefore, the aim of this study is to perform a literature review to evaluate the main clinical characteristics and complications of skin disorders in diabetic's patients. Additionally, physiopathology early-stage skin disorders and dermocosmetic management were also reviewed.

Comparative Genomic, MicroRNA, and Tissue Analyses Reveal Subtle Differences between Non-Diabetic and Diabetic Foot Skin

Diabetes Mellitus (DM) is a chronic, severe disease rapidly increasing in incidence and prevalence and is associated with numerous complications. Patients with DM are at high risk of developing diabetic foot ulcers (DFU) that often lead to lower limb amputations, long term disability, and a shortened lifespan. Despite this, the effects of DM on human foot skin biology are largely unknown. Thus, the focus of this study was to determine whether DM changes foot skin biology predisposing it for healing impairment and development of DFU. Foot skin samples were collected from 20 patients receiving corrective foot surgery and, using a combination of multiple molecular and cellular approaches, we performed comparative analyses of non-ulcerated non-neuropathic diabetic foot skin (DFS) and healthy non-diabetic foot skin (NFS). MicroRNA (miR) profiling of laser captured epidermis and primary dermal fibroblasts from both DFS and NFS samples identified 5 miRs de-regulated in the epidermis of DFS though none reached statistical significance. MiR-31-5p and miR-31-3p were most profoundly induced. Although none were significantly regulated in diabetic fibroblasts, miR-29c-3p showed a trend of up-regulation, which was confirmed by qPCR in a prospective set of 20 skin samples. Gene expression profiling of full thickness biopsies identified 36 de-regulated genes in DFS (>2 fold-change, unadjusted p-value ≤ 0.05). Of this group, three out of seven tested genes were confirmed by qPCR: SERPINB3 was up-regulated whereas OR2A4 and LGR5 were down-regulated in DFS. However no morphological differences in histology, collagen deposition, and number of blood vessels or lymphocytes were found. No difference in proliferative capacity was observed by quantification of Ki67 positive cells in epidermis. These findings suggest DM causes only subtle changes to foot skin. Since morphology, mRNA and miR levels were not affected in a major way, additional factors, such as neuropathy, vascular complications, or duration of DM, may further compromise tissue's healing ability leading to development of DFUs.

Alginate and DNA Gels Are Suitable Delivery Systems for Diabetic Wound Healing

Diabetic foot ulcers (DFU) represent a severe health problem and an unmet clinical challenge. In this study, we tested the efficacy of novel biomaterials in improving wound healing in mouse models of diabetes mellitus (DM). The biomaterials are composed of alginate- and deoxyribonucleic acid (DNA)-based gels that allow incorporation of effector cells, such as outgrowth endothelial cells (OEC), and provide sustained release of bioactive factors, such as neuropeptides and growth factors, which have been previously validated in experimental models of DM wound healing or hind limb ischemia. We tested these biomaterials in mice and demonstrate that they are biocompatible and can be injected into the wound margins without major adverse effects. In addition, we show that the combination of OEC and the neuropeptide Substance P has a better healing outcome than the delivery of OEC alone, while subtherapeutic doses of vascular endothelial growth factor (VEGF) are required for the transplanted cells to exert their beneficial effects in wound healing. In summary, alginate and DNA scaffolds could serve as potential delivery systems for the next-generation DFU therapies.