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The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) Diabetic Foot Consortium (DFC) was established in September 2018 by the NIDDK to build an organization to facilitate the highest quality of clinical research on diabetic foot ulcers (DFUs) that will answer clinically significant questions to improve DFU healing and prevent amputations. The initial focus of the DFC is to develop and validate biomarkers for DFUs that can be used in clinical care and research. The DFC consists of a data coordinating center (DCC) for operational oversight and statistical analysis, clinical sites for participant recruitment and evaluation, and biomarker analysis units (BAUs). The DFC is currently studying biomarkers to predict wound healing and recurrence and is collecting biosamples for future studies through a biorepository. The DFC plans to address the challenges of recruitment and eligibility criteria for DFU clinical trials by taking an approach of “No DFU Patient Goes Unstudied.” In this platform approach, clinical history, DFU outcome, wound imaging, and biologic measurements from a large number of patients will be captured and the in-depth longitudinal data set will be analyzed to develop a computational-based DFU risk factor profile to facilitate scientifically sound clinical trial design. The DFC will expand its platform to include studies of the role of social determinants of health, such as food insecurity, housing instability, limited health literacy, and poor social support. The DFC is starting partnerships with the broad group of stakeholders in the wound care community.

Diabetic foot ulcers and other chronic wounds with impaired healing can be treated with bioengineered skin or with growth factors. However, most patients do not benefit from these treatments. Here we report the development and preclinical therapeutic performance of a strain-programmed patch that rapidly and robustly adheres to diabetic wounds, and promotes wound closure and re-epithelialization. The patch consists of a dried adhesive layer of crosslinked polymer networks bound to a pre-stretched hydrophilic elastomer backing, and implements a hydration-based shape-memory mechanism to mechanically contract diabetic wounds in a programmable manner on the basis of analytical and finite-element modelling. In mouse and human skin, and in mini-pigs and humanized mice, the patch enhanced the healing of diabetic wounds by promoting faster re-epithelialization and angiogenesis, and the enrichment of fibroblast populations with a pro-regenerative phenotype. Strain-programmed patches might also be effective for the treatment of other forms of acute and chronic wounds.

Diabetic foot ulcers are a health crisis that affect millions of individuals worldwide. Current standard of care involves diligent wound care with adjunctive antibiotics and surgical debridement. However, despite this, the majority will still become infected and fail to heal. Recent efforts using bioengineered skin initially appeared promising, but randomized clinical trials have disappointed. Scientists have now begun to understand that the normal wound healing physiology does not apply to diabetic foot ulcers as they maintain a chronic state of inflammation and fail to progress in a linear pathway. Using transcriptomics, research over the past decade has started identifying master genes and protein pathways that are dysregulated in patients with diabetes. This review paper discusses those genes involved and how novel advancements are using this information to create new biologically based compounds to accelerate wound healing in patients with diabetic foot ulcers.

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.

Cutaneous wound healing is a highly coordinated process involving numerous molecular pathways that regulate the function of specific skin cell types. One of the key decisions in acute and/or chronic wound healing management is to choose the skin substitute that, based on its composition and/or properties, may act as permanent skin replacement or temporary wound cover. The current products however are limited in their action, especially in the context of large chronic wounds or extensive second-/third-degree burns, due to the risk of developing infection, the limited vascularization, the inability to integrate to host tissue, and the lack in the healed area of skin apparatus responsible for temperature control, pigmentation, immune regulation, and nerve supply. In addition, the high cost of skin substitutes precludes their use in small- and moderate-size burns because they are economically impractical and protract the time to definitive wound closure. Thus, the need to develop cost-effective substitutes of high quality is imperative. The purpose of this review is to discuss current available products, their limitations and to provide some perspectives on future research toward generation of cost-effective, high-quality substitutes.

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.

High-parameter tissue imaging enables detailed molecular analysis of single cells in their spatial environment. However, the comprehensive characterization and mapping of tissue states through multimodal imaging across different physiological and pathological conditions requires data integration across multiple imaging systems. Here, we introduce MIAAIM (Multi-omics Image Alignment and Analysis by Information Manifolds) a modular, reproducible computational framework for aligning data across bioimaging technologies, modeling continuities in tissue states, and translating multimodal measures across tissue types. We demonstrate MIAAIM’s workflows across diverse imaging platforms, including histological stains, imaging mass cytometry, and mass spectrometry imaging, to link cellular phenotypic states with molecular microenvironments in clinical biopsies from multiple tissue types with high cellular complexity. MIAAIM provides a robust foundation for the development of computational methods to integrate multimodal, high-parameter tissue imaging data and enable downstream computational and statistical interrogation of tissue states.

Diabetic foot ulceration is a major diabetic complication with unmet needs. We investigated the efficacy of epidermal stem cells and epidermal stem cells-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 and promoted alternative or M2 macrophage polarization. In wounds of db/db mice, treatment with both epidermal stem cells and ESCs-Exo, when compared with fibroblast exosomes and PBS control, accelerated wound healing by decreasing inflammation, augmenting wound cell proliferation, stimulating angiogenesis, and inducing M2 macrophage 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 microRNAs than those contained in fibroblast exosomes. In silico functional analysis showed that the ESCs-Exo microRNAs‒target genes were primarily involved in homeostatic processes and cell differentiation and highlighted regulatory control of phosphatidylinositol-3 kinase/protein kinase B and TGFβ signaling pathways. This was also validated in vitro. Collectively, our results indicate that epidermal stem cells 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.

Neuropathy is a major cause of morbidity and mortality in individuals with diabetes, with no effective therapy to alter the inevitable progression of nerve damage. We hypothesized that mesenchymal stroma cell-like populations, that are characterized as immune modulators also have the potential of inducing angiogenesis and neurite outgrowth, might be useful in treating diabetic peripheral neuropathy (DPN). The aims of this study were to investigate the efficacy and safety of mesenchymal stem cell-like product (PDA-002) in treating DPN. A phase-2 randomized placebo-controlled trial was conducted in 26 patients with DPN. Treatment consisted of three rounds of intramuscular injections in one lower limb using one of the three randomized treatment arms PDA-002 (low-dose 3 × 106 cells), PDA-002 (high-dose 30 × 106 cells), or placebo. Three treatments per patient occurred on days 1, 29, and 57. Study endpoints included efficacy and safety of PDA-002 in treating DPN in both lower extremities following unilateral local injection. Outcome measures included intra-epidermal nerve fiber density (IENFD) up to 1 year from the day of treatment with 6-month as the primary outcome measurement. In this phase 2 study of DPN, PDA-002 was well tolerated in both doses. No significant changes were noted in IENFD in both the treated and untreated leg in the NIS-LL, NTSS-6, or UENS. Mesenchymal stem cells represent a novel mechanism for treating diabetic neuropathy and are well tolerated. Preliminary results highlight the need of further investigation of PDA-001 as a disease modifying agent for treatment of DPN.

IntroductionThe aim of the study was to develop and validate a clinical prediction rule (CPR) for foot ulceration in people with diabetes.Research design and methodsDevelopment of a CPR using individual participant data from four international cohort studies identified by systematic review, with validation in a fifth study. Development cohorts were from primary and secondary care foot clinics in Europe and the USA (n=8255, adults over 18 years old, with diabetes, ulcer free at recruitment). Using data from monofilament testing, presence/absence of pulses, and participant history of previous ulcer and/or amputation, we developed a simple CPR to predict who will develop a foot ulcer within 2 years of initial assessment and validated it in a fifth study (n=3324). The CPR’s performance was assessed with C-statistics, calibration slopes, calibration-in-the-large, and a net benefit analysis.ResultsCPR scores of 0, 1, 2, 3, and 4 had a risk of ulcer within 2 years of 2.4% (95% CI 1.5% to 3.9%), 6.0% (95% CI 3.5% to 9.5%), 14.0% (95% CI 8.5% to 21.3%), 29.2% (95% CI 19.2% to 41.0%), and 51.1% (95% CI 37.9% to 64.1%), respectively. In the validation dataset, calibration-in-the-large was −0.374 (95% CI −0.561 to −0.187) and calibration slope 1.139 (95% CI 0.994 to 1.283). The C-statistic was 0.829 (95% CI 0.790 to 0.868). The net benefit analysis suggested that people with a CPR score of 1 or more (risk of ulceration 6.0% or more) should be referred for treatment.ConclusionThe clinical prediction rule is simple, using routinely obtained data, and could help prevent foot ulcers by redirecting care to patients with scores of 1 or above. It has been validated in a community setting, and requires further validation in secondary care settings.

To understand the diabetic wound healing microenvironment, we profiled 174,962 single cells from foot, forearm, and PBMCs using single-cell RNA sequencing (scRNASeq) approach. Our analysis shows enrichment of a unique population of fibroblasts overexpressing MMP1, MMP3, MMP11, HIF1A, CHI3L1, and TNFAIP6 genes and M1 macrophage polarization in the DFU patients with healing wounds. Further, scRNASeq of spatially separated samples from same patient and spatial transcriptomics (ST) revealed preferential localization of these healing associated fibroblasts toward deep wound/ulcer bed as compared to wound edge or non-wounded skin. ST also validated our findings of higher enrichment of M1 macrophages in healers and M2 macrophages in non-healers. Our analysis provides deep insights into the wound healing microenvironment, identifying cell types that could be critical in promoting DFU healing, and may inform novel therapeutic approaches for DFU treatment.

A major challenge in the management of patients suffering from diabetes is the risk of developing nonhealing foot ulcers. Most in vitro methods to screen drugs for wound healing therapies rely on conventional 2D cell cultures that do not closely mimic the complexity of the diabetic wound environment. In addition, while three-dimensional (3D) skin tissue models of human skin exist, they have not previously been adapted to incorporate patient-derived macrophages to model inflammation from these wounds. In this study, we present a 3D human skin equivalent (HSE) model incorporating blood-derived monocytes and primary fibroblasts isolated from patients with diabetic foot ulcers (DFUs). We demonstrate that the monocytes differentiate into macrophages when incorporated into HSEs and secrete a cytokine profile indicative of the proinflammatory M1 phenotype seen in DFUs. We also show how the interaction between fibroblasts and macrophages in the HSE can guide macrophage polarization. Our findings take us a step closer to creating a human, 3D skin-like tissue model that can be applied to evaluate the response of candidate compounds needed for potential new foot ulcer therapies in a more complex tissue environment that contributes to diabetic wounds. IMPACT STATEMENT: This study is the first to incorporate disease-specific, diabetic macrophages into a three-dimensional (3D) model of human skin. We show how to fabricate skin that incorporates macrophages with disease-specific fibroblasts to guide macrophage polarization. We also show that monocytes from diabetic patients can differentiate into macrophages directly in this skin disease model, and that they secrete a cytokine profile mimicking the proinflammatory M1 phenotype seen in diabetic foot ulcers. The data presented here indicate that this 3D skin disease model can be used to study macrophage-related inflammation in diabetes and as a drug testing tool to evaluate new treatments for the disease.

Epidemiological studies have reported strong association between sleep loss and hypertension with unknown mechanisms. This study investigated macrovascular and microcirculation changes and inflammatory markers during repetitive sleep restriction. Sex differences were also explored. Forty-five participants completed a 22-day in-hospital protocol. Participants were assigned to, (1) eight-hour sleep per night (control), or (2) sleep restriction (SR) condition: participants slept from 0300 to 0700 h for three nights followed by a recovery night of 8-h sleep, repeated four times. Macrocirculation assessed by flow mediated dilation (FMD) and microcirculation reactivity tests were performed at baseline, last day of each experimental block and during recovery at the end. Cell adhesion molecules and inflammatory marker levels were measured in blood samples. No duration of deprivation (SR block) by condition interaction effects were found for FMD, microcirculation, norepinephrine, cell adhesion molecules, IL-6 or IL-8. However, when men and women were analyzed separately, there was a statistical trend (p = 0.08) for increased IL-6 across SR blocks in women, but not in men. Interestingly, men showed a significant progressive (dose dependent) increase in skin vasodilatation (p = 0.02). A novel and unexpected finding was that during the recovery period, men that had been exposed to repeated SR blocks had elevated IL-8 and decreased norepinephrine. Macrocirculation, microcirculation, cell adhesion molecules, and markers of inflammation appeared to be resistant to this model of short-term repetitive exposures to the blocks of shortened sleep in healthy sleepers. However, men and women responded differently, with women showing mild inflammatory response and men showing more vascular system sensitivity to the repetitive SR.

Current treatment options for foot ulcers, a serious and prevalent complication of diabetes, remain nonspecific. In this Perspective, we present recent advances in understanding the pathophysiology of diabetic wound healing and the emergence of previously unidentified targets. We discuss wound dressings tailored to the diabetic wound environment currently under development.

Nonhealing diabetic foot ulcers (DFUs) are characterized by low-grade chronic inflammation, both locally and systemically. We prospectively followed a group of patients who either healed or developed nonhealing chronic DFUs. Serum and forearm skin analysis, both at the protein expression and the transcriptomic level, indicated that increased expression of factors such as interferon-γ (IFN-γ), vascular endothelial growth factor, and soluble vascular cell adhesion molecule-1 were associated with DFU healing. Furthermore, foot skin single-cell RNA sequencing analysis showed multiple fibroblast cell clusters and increased inflammation in the dorsal skin of patients with diabetes mellitus (DM) and DFU specimens compared with control subjects. In addition, in myeloid cell DM and DFU upstream regulator analysis, we observed inhibition of interleukin-13 and IFN-γ and dysregulation of biological processes that included cell movement of monocytes, migration of dendritic cells, and chemotaxis of antigen-presenting cells pointing to an impaired migratory profile of immune cells in DM skin. The SLCO2A1 and CYP1A1 genes, which were upregulated at the forearm of nonhealers, were mainly expressed by the vascular endothelial cell cluster almost exclusively in DFU, indicating a potential important role in wound healing. These results from integrated protein and transcriptome analyses identified individual genes and pathways that can potentially be targeted for enhancing DFU healing.

Diabetic foot ulcers (DFUs) are a major complication of diabetes, and there is a critical need to develop novel cell- and tissue-based therapies to treat these chronic wounds. Induced pluripotent stem cells (iPSCs) offer a replenishing source of allogeneic and autologous cell types that may be beneficial to improve DFU wound-healing outcomes. However, the biologic potential of iPSC-derived cells to treat DFUs has not, to our knowledge, been investigated. Toward that goal, we have performed detailed characterization of iPSC-derived fibroblasts from both diabetic and nondiabetic patients. Significantly, gene array and functional analyses reveal that iPSC-derived fibroblasts from both patients with and those without diabetes are more similar to each other than were the primary cells from which they were derived. iPSC-derived fibroblasts showed improved migratory properties in 2-dimensional culture. iPSC-derived fibroblasts from DFUs displayed a unique biochemical composition and morphology when grown as 3-dimensional (3D), self-assembled extracellular matrix tissues, which were distinct from tissues fabricated using the parental DFU fibroblasts from which they were reprogrammed. In vivo transplantation of 3D tissues with iPSC-derived fibroblasts showed they persisted in the wound and facilitated diabetic wound closure compared with primary DFU fibroblasts. Taken together, our findings support the potential application of these iPSC-derived fibroblasts and 3D tissues to improve wound healing.-Kashpur, O., Smith, A., Gerami-Naini, B., Maione, A. G., Calabrese, R., Tellechea, A., Theocharidis, G., Liang, L., Pastar, I., Tomic-Canic, M., Mooney, D., Veves, A., Garlick, J. A. Differentiation of diabetic foot ulcer-derived induced pluripotent stem cells reveals distinct cellular and tissue phenotypes.

Objective: The elderly are at high risk for developing chronic skin wounds, but the effects of intrinsic aging on skin healing are difficult to isolate due to common comorbidities like diabetes. Our objective is to use multiphoton microscopy (MPM) to find endogenous, noninvasive biomarkers to differentiate changes in skin wound healing metabolism between young and aged mice in vivo. Approach: We utilized MPM to monitor skin metabolism at the edge of full-thickness, excisional wounds in 24- and 4-month-old mice of both sexes for 10 days. MPM can assess quantitative biomarkers of cellular metabolism in vivo by utilizing autofluorescence from the cofactors nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD). Results: An optical redox ratio of FAD/(NADH+FAD) autofluorescence and NADH fluorescence lifetime imaging revealed dynamic changes in keratinocyte function during healing. Aged female mice demonstrated an attenuation of keratinocyte proliferation during wound healing detectable optically through a higher redox ratio and longer NADH fluorescence lifetime. By measuring the correlation between NADH lifetime and the optical redox ratio at each day, we also demonstrate sensitivity to the proliferative phase of wound healing. Innovation: Label-free MPM was used to longitudinally monitor individual wounds in vivo, which revealed age-dependent differences in wound metabolism. Conclusion: These results indicate in vivo MPM can provide quantitative biomarkers of age-related delays in healing, which can be used in the future to provide patient-specific wound care.

Rationale: Although both type 2 diabetes mellitus (T2DM) and obstructive sleep apnea (OSA) are independently recognized as risk factors for cardiovascular disease, little is known about their interaction.Objectives: We hypothesized that T2DM and OSA act synergistically to increase vascular risk, and that treatment of OSA would improve vascular reactivity in patients with T2DM plus OSA.Methods: Cross-sectional study of 141 adults with T2DM, OSA, T2DM plus OSA, and control subjects, followed by a 3-month, parallel-arm, randomized, placebo-controlled trial comparing active and sham continuous positive airway pressure (CPAP) in 53 adults with T2DM plus OSA. Endothelium-dependent macro- and microvascular reactivity (flow-mediated dilation [FMD] of the brachial artery and acetylcholine-induced dilation of forearm microvasculature, respectively) and cardiovascular magnetic resonance to assess left- and right-ventricular mass/volume.Results: Mean (±SD) FMD was 6.1 (±4.0)%, 7.3 (±3.6)%, 6.8 (±4.5)%, and 4.8 (±2.9)% in control subjects, T2DM only, OSA only, and T2DM plus OSA, respectively. We observed a significant T2DM × OSA interaction on FMD, such that the mean effect of OSA in those with T2DM was 3.1% (95% confidence interval [CI], 0.6 to 5.6) greater than the effect of OSA in those without T2DM. A total of 3 months of CPAP resulted in a mean absolute increase in FMD of 0.3% (95% CI, -1.9 to 2.5; primary endpoint), with a net improvement of 1.1% (95% CI, -1.4 to 3.6) among those with adherence of 4 h/night or greater. A significant T2DM × OSA interaction was found for both left ventricular (LV) and right ventricular end-diastolic volume, such that OSA was associated with a 22.4 ml (95% CI, 3.2 to 41.6) greater LV end-diastolic volume and 23.2 ml (95% CI, 2.6 to 43.8) greater right ventricular end-diastolic volume in those with T2DM compared with the impact of OSA in those without T2DM. We observed a net improvement in LV end-diastolic volume of 8.7 ml (95% CI, -7.0 to 24.4).Conclusions: The combination of T2DM plus OSA is associated with macrovascular endothelial dysfunction beyond that observed with either disease alone. CPAP for 3 months did not significantly improve macrovascular endothelial function in the intent-to-treat analysis; however, cardiovascular magnetic resonance results suggest that there may be a beneficial effect of CPAP on LV diastolic volume.Clinical trial registered with www.clinicaltrials.gov (NCT01629862).

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.

Lower extremity ulcerations represent a major complication in diabetes mellitus and involve multiple physiological factors that lead to impairment of wound healing. Neuropeptides are neuromodulators implicated in various processes including diabetic wound healing. Diabetes causes autonomic and small sensory nerve fibers neuropathy as well as inflammatory dysregulation, which manifest with decreased neuropeptide expression and a disproportion in pro- and anti- inflammatory cytokine response. Therefore to fully understand the contribution of autonomic nerve dysfunction in diabetic wound healing it is crucial to explore the implication of neuropeptides. Here, we will discuss recent studies elucidating the role of specific neuropeptides in wound healing.

Introduction Diabetic peripheral neuropathy (DPN) is one of the most common complications of diabetes and has been associated with cardiovascular disease, the leading cause of mortality in diabetes. As asymptomatic myocardial ischemia (MI) is frequent in diabetes, we hypothesized that DPN may be associated with MI in patients with type 2 diabetes mellitus and no history of cardiovascular events. Methods Eighty-two patients with DPN (n = 41) or without DPN (n = 41) were included. Among the DPN group, 15 had active foot ulcers. All subjects underwent Technetium-99 m sestamibi single-photon emission computed tomographic imaging for the estimation of myocardial ischemia, expressed as Summed Stress Score (SSS). The Neuropathy Disability Score (NDS) was used to quantify DPN and abnormal ratio of the longest electrocardiographic RR interval between the 28th and 32nd beats, after standing to the shortest interval between the 13th and 17th beats (RR ratio) was used as an index of cardiovascular autonomic neuropathy (CAN). Results Abnormal SSS was observed in 9.8% of patients without DPN and in 46.3% of patients with DPN (p

Obstructive sleep apnea (OSA) affects a large proportion of adults, and is as an independent risk factor for cerebrovascular and cardiovascular disease. The repetitive airway obstruction that characterizes OSA results in intermittent hypoxia, intrathoracic pressure swings, and sleep fragmentation, which in turn lead to sympathetic activation, oxidative stress, inflammation, and endothelial dysfunction. This review outlines the associations between OSA and vascular diseases and describes basic mechanisms that may be responsible for this association, in both the micro- and macrocirculation. It also reports on interventional studies that aim to ameliorate OSA and thereby reduce vascular disease burden. © 2016 American Physiological Society. Compr Physiol 6:1519-1528, 2016.

Current chronic wound treatments often fail to promote healing of diabetic foot ulcers (DFU), leading to amputation and increased patient morbidity. A critical mediator of proper wound healing is the production, assembly, and remodeling of the extracellular matrix (ECM) by fibroblasts. However, little is known about how these processes are altered in fibroblasts within the DFU microenvironment. Thus, we investigated the capacity of multiple, primary DFU-derived fibroblast strains to express, produce, and assemble ECM proteins compared to diabetic patient-derived fibroblasts and healthy donor-derived fibroblasts. Gene expression microarray analysis showed differential expression of ECM and ECM-regulatory genes by DFU-derived fibroblasts which translated to functional differences in a 3D in vitro ECM tissue model. DFU-derived fibroblasts produced thin, fibronectin-rich matrices, and responded abnormally when challenged with transforming growth factor-beta, a key regulator of matrix production during healing. These results provide novel evidence that DFU-derived fibroblasts contribute to the defective matrices of DFUs and chronic wound pathogenesis.

Purpose To assess differences in the phosphorus-31 (31P) metabolism and morphology in multiple muscle regions in the forefoot of diabetic patients and normal subjects. Materials and Methods Fifteen diabetic patients and 15 normal subjects were assessed for muscle atrophy by 1H magnetic resonance imaging (MRI) at 3T to grade the flexor hallucis, adductor hallucis, interosseous regions, and entire foot cross-section. Each region and the entire foot were also quantitatively evaluated for metabolic function using 31P imaging for spatial mapping of the inorganic phosphate (Pi) to phosphocreatine (PCr) ratio (Pi/PCr). The ratio of viable muscle area to the predefined region areas (31P/1H) was calculated. The variability of each method was assessed by its coefficient of variation (CV). Results Muscle atrophy was significantly more severe in diabetic compared to normal subjects in all regions (P < 0.01). The 31P/1H area ratio was significantly larger in the adductor hallucis than in the other two regions (P < 0.05). The Pi/PCr ratio was significantly different between the two groups in the flexor hallucis and interosseous regions (P < 0.05) but not adductor hallucis region. The CV for Pi/PCr ranged from 10.13 to 55.84, while it ranged from 73.40 to 263.90 for qualitative grading. Conclusion Changes in atrophy and metabolism appear to occur unequally between different regions of the forefoot in diabetes. The adductor hallucis region appears more capable of maintaining structural and metabolic integrity than the flexor hallucis or interosseous regions. The CV analysis suggests that the quantitative 31P methods have less variability than the qualitative grading. J. Magn. Reson. Imaging 2016;44:1132–1142.

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.

Neuropathies of the peripheral and autonomic nervous systems affect up to half of all people with diabetes mellitus, and are major risk factors for foot ulceration, amputation and cardiovascular dysfunction. Peripheral neuropathies manifest with either painful or painless symptoms, but many patients experience both. Once diagnosed appropriately, painful diabetic neuropathy management presents a unique challenge for physicians and should be considered as a syndrome, clinically distinct from diabetic peripheral neuropathy. The aetiology is multifactorial: metabolic changes in diabetes may directly affect neural tissue and neurodegenerative changes are precipitated by compromised nerve vascular supply. Metabolic changes include the elevated polyol pathway activity, the increased oxidative stress, the formation of advanced glycation and lipoxidation end products, and various pro-inflammatory changes. These mechanisms work in combination and interact in a mutually facilitatory fashion. This review focuses on the current therapies for the management of peripheral and cardiovascular autonomic neuropathy and of painful neuropathy as a distinct entity, based on the current knowledge of diabetic neuropathy. Moreover, the role of ACE inhibition has been explored in the treatment of Cardiovascular Autonomic Neuropathy.

Fifteen percent of diabetes mellitus (DM) patients are expected to develop a diabetic foot ulcer (DFU) within their lifetime. DFUs represent an ever increasing burden for the healthcare system. Chronic wounds, lack the linear progression from one classical phase of healing to the next and are mainly characterized by the persistence of the inflammatory phase. To define the transcriptome landscape of healthy uninjured skin, DM and DFU skin, we performed transcriptome profiling on skin specimens from foot surgeries obtained from 4 controls, 4 DM patients without DFU and on samples from 2 DM patients after DFU debridement . We generated the single cell transcriptome profiles of 3,766 and 3,469 cells from non-DM and DM patients and of 660 cells from patients with active DFUs. Further, bioinformatics analysis identified clusters of cells with similar transcriptome states. The most abundant cell type was fibroblast. Other clusters included adipocytes and endothelial cells. T-cells, monocytes, and macrophages were the main immune cell types identified. As macrophages are critical for healing of DFUs, we estimated the abundance of total macrophages and their polarization. Approximately 10% of cells were macrophages in each group while DFU group had significantly more M1 polarized as compared to M2 (M1/M2=2.4 times). Supervised analysis identified a set of 66 and 1genes that are significantly differentially expressed in macrophages of DFU and DM patients respectively as compared to controls. A master regulator (MR) analysis in DFU patients identified activation of inflammatory and angiogenesis related MRs (e.g., STAT3, IL15). while in DM patients it identified activation of distinct inflammatory MRs (e.g., SMAD3, CD44). In summary, we present for the first time sc-RNAseq data on lower extremity skin samples that could help delineate the molecular mechanisms of dysregulated wound healing and identify novel therapeutic targets. Disclosure G. Theocharidis: None. S.S. Bhasin: None. K. Kounas: None. M.K. Bhasin: None. A. Veves: Advisory Panel; Self; HyperMed Imaging, Inc., AOBiome.

Diabetes, especially type 2, is characterized by systemic inflammation. At the skin level, there is increased infiltration by inflammatory cells and polarization of the macrophages toward the M1 inflammatory type. In addition, there is increased expression of MMP-9 and protein tyrosine phosphatase-1B (PTP1B). Other dermatologic conditions include acanthosis nigricans, characterized by a hyperpigmented, velvety, cutaneous thickening that appears predominantly in the neck, axilla, and groin areas; necrobiosis lipoidica (NL), a chronic, necrotizing, granulomatous skin disease; granuloma annulare; diabetic bullae; and diabetic dermopathy. As these conditions can be present in the lower extremity, they should be sought and easily recognized by the health care providers who manage the diabetic lower extremity.

Diabetic peripheral neuropathy and vascular disease, along with trauma, have long been recognized as major risk factors for the development of diabetic foot ulcerations (DFUs). More recently, chronic inflammation, abnormal extracellular matrix (ECM) remodeling, and reduced wound neovascularization, as a result of dysregulated cell function with imbalanced secretion of cytokines, matrix metalloproteinases, and growth factors, have been implicated in DFU failure to heal. Therefore, researchers are now focusing their efforts on further understanding the cellular and molecular mechanisms of diabetes-associated impaired wound healing, in an attempt to identify new targets and novel potential therapeutic approaches for DFUs, which remain a serious unmet clinical need. A growing body of evidence suggests an important role of neuropeptides in skin repair, particularly in diabetes, where neuropeptide levels are diminished. On the other hand, there is emerging interest in dissecting the mechanisms of dysregulated inflammation, namely the changes in immune cells, such as macrophages and mast cells (MCs), in diabetic wound healing. Studies using in vitro and in vivo models of diabetic wound healing have considerably improved our understanding of the healing process. However, the currently available models have major caveats and are not ideal to study chronic, complicated, and multifactorial wounds, such as DFUs. In this chapter we summarize the involvement of neuropeptides and mast cells in diabetic wound healing, highlighting the most recent findings. We also discuss the benefits and limitations of the current wound healing models, emphasizing the need for confirmation and/or validation in multiple models and/or tissue specimens from human subjects.

Normal vascular function is characterized by a continuous interaction between the endothelium and vascular smooth muscle that maintains optimal vascular tone and organ perfusion via balanced vasodilatory and vasoconstrictive mechanisms. In an environment of chronic hyperglycemia, such as that occurring in diabetes mellitus, normal vascular function is disrupted most likely due to elevations in reactive oxygen species and the compounding effects of vascular inflammation. Such vascular dysfunctions represent key mechanisms for atherosclerotic changes and primary events in the pathogenesis of cardiovascular disease, which remains the single leading cause of mortality for those with type 1 or type 2 diabetes. Exercise has been described as a cornerstone in the management and treatment of diabetes due to its prominent role in improving both metabolic and cardiovascular health. Evidence suggests that habitual physical activity disrupts chronic hyperglycemic by improving glycemic control via enhanced GLUT protein activation and increased insulin sensitivity. Furthermore, exercise-mediated shear stress may enhance vasodilatory capacity by improving expression of endothelial nitric oxide synthase proteins and enhancing nitric oxide bioavailability. Although some specific precautions must be adhered to when prescribing exercise to diabetic populations, the benefits significantly outweigh the consequences of continuing a sedentary lifestyle. This chapter will present a non-exhaustive review focusing on changes in vascular function and inflammatory status from healthy to diabetic states, techniques that are often implemented to quantify such changes in vascular function, and the role of exercise in improving underlying mechanisms critical to maintaining normal vascular function and disrupting the pathogenesis of cardiovascular disease.

Diabetic foot ulcers (DFUs) are one of the most common and serious complications of diabetes mellitus, as wound healing is impaired in the diabetic foot. Wound healing is a dynamic and complex biological process that can be divided into four partly overlapping phases: hemostasis, inflammation, proliferative and remodeling. These phases involve a large number of cell types, extracellular components, growth factors and cytokines. Diabetes mellitus causes impaired wound healing by affecting one or more biological mechanisms of these processes. Most often, it is triggered by hyperglycemia, chronic inflammation, micro- and macro-circulatory dysfunction, hypoxia, autonomic and sensory neuropathy, and impaired neuropeptide signaling. Research focused on thoroughly understanding these mechanisms would allow for specifically targeted treatment of diabetic foot ulcers. The main principles for DFU treatment are wound debridement, pressure off-loading, revascularization and infection management. New treatment options such as bioengineered skin substitutes, extracellular matrix proteins, growth factors, and negative pressure wound therapy, have emerged as adjunctive therapies for ulcers. Future treatment strategies include stem cell-based therapies, delivery of gene encoding growth factors, application of angiotensin receptors analogs and neuropeptides like substance P, as well as inhibition of inflammatory cytokines. This review provides an outlook of the pathophysiology in diabetic wound healing and summarizes the established and adjunctive treatment strategies, as well as the future therapeutic options for the treatment of DFUs.