Low recruitment of immune cells with increased expression of endothelial adhesion molecules in margins of the chronic diabetic foot ulcers

Wounds under diabetic milieu: The role of immune cellar components and signaling pathways

A major challenge in the field of diabetic wound healing is to confirm the body's intrinsic mechanism that could sense the immune system damage promptly and protect the wound from non-healing. Accumulating literature indicates that macrophage, a contributor to prolonged inflammation occurring at the wound site, might play such a role in hindering wound healing. Likewise, other immune cell dysfunctions, such as persistent neutrophils and T cell infection, may also lead to persistent oxidative stress and inflammatory reaction during diabetic wound healing. In this article, we discuss recent advances in the immune cellular components in wounds under the diabetic milieu, and the role of key signaling mechanisms that compromise the function of immune cells leading to persistent wound non-healing.

Synthesis and evaluation of wound healing properties of hydro-diab hydrogel loaded with green-synthetized AGNPS: in vitro and in ex vivo studies

In diabetic patients, the presence of neuropathy, peripheral vascular diseases and ischemia, leads to the formation of foot ulcerations with a higher risk of infection because the normal response to bacterial infection is missing. In the aim to control and treat diabetic foot ulcerations (DFUs), wound dressings that are able to absorb exudate, to prevent infections, and to promote wound healing are needed. For this reason, the aim of the present research was to synthetize a biocompatible hydrogel (called HyDrO-DiAb) composed of carboxymethylcellulose loaded with silver nanoparticles (AgNPs) for the treatment of diabetic foot ulcers. In this study, AgNPs were obtained by a green synthesis and, then, were dissolved in a CMC hydrogel that, after a freeze drying process, becomes a flexible and porous structure. The in vitro and in ex vivo wound healing activity of the obtained HyDrO-DiAb hydrogel was evaluated.

Glucose inhibits haemostasis and accelerates diet-induced hyperlipidaemia in zebrafish larvae

Hyperglycaemia damages the microvasculature in part through the reduced recruitment of immune cells and interference with platelet signalling, leading to poor wound healing and accelerated lipid deposition in mammals. We investigated the utility of zebrafish larvae to model the effect of exogenous glucose on neutrophil and macrophage recruitment to a tail wound, wound-induced haemostasis, and chicken egg yolk feed challenge-induced hyperlipidaemia by supplementing larvae with exogenous glucose by immersion or injection. Neither method of glucose supplementation affected the recruitment of neutrophils and macrophages following tail transection. Glucose injection reduced thrombocyte retention and fibrin plug formation while only thrombocyte retention was reduced by glucose immersion following tail transection. We observed accelerated lipid accumulation in glucose-injected larvae challenged with high fat chicken egg yolk feeding. Our study identifies conserved and divergent effects of high glucose on inflammation, haemostasis, and hyperlipidaemia in zebrafish larvae compared to mammals.

Small Nerve Fiber Damage and Langerhans Cells in Type 1 and Type 2 Diabetes and LADA Measured by Corneal Confocal Microscopy

Purpose

Increased corneal and epidermal Langerhans cells (LCs) have been reported in patients with diabetic neuropathy. The aim of this study was to quantify the density of LCs in relation to corneal nerve morphology and the presence of diabetic neuropathy and to determine if this differed in patients with type 1 diabetes mellitus (T1DM), type 2 diabetes mellitus (T2DM), and latent autoimmune diabetes of adults (LADA).

Methods

Patients with T1DM (n = 25), T2DM (n = 36), or LADA (n = 23) and control subjects (n = 23) underwent detailed assessment of peripheral neuropathy and corneal confocal microscopy. Corneal nerve fiber density (CNFD), branch density (CNBD), length (CNFL) and total, immature and mature LC densities were quantified.

Results

Lower CNFD (P < 0.001), CNBD (P < 0.0001), and CNFL (P < 0.0001) and higher LC density (P = 0.03) were detected in patients with T1DM, T2DM, and LADA compared to controls. CNBD was inversely correlated with mature (r = -0.5; P = 0.008), immature (r = -0.4; P = 0.02) and total (r = -0.5; P = 0.01) LC density, and CNFL was inversely correlated with immature LC density (r = -0.4; P = 0.03) in patients with T1DM but not in patients with T2DM and LADA.

Conclusions

This study shows significant corneal nerve loss and an increase in LC density in patients with T1DM, T2DM, and LADA. Furthermore, increased LC density correlated with corneal nerve loss in patients with T1DM.

SDF-1α Gene-Activated Collagen Scaffold Restores Pro-Angiogenic Wound Healing Features in Human Diabetic Adipose-Derived Stem Cells

Non-healing diabetic foot ulcers (DFUs) can lead to leg amputation in diabetic patients. Autologous stem cell therapy holds some potential to solve this problem; however, diabetic stem cells are relatively dysfunctional and restrictive in their wound healing abilities. This study sought to explore if a novel collagen-chondroitin sulfate (coll-CS) scaffold, functionalized with polyplex nanoparticles carrying the gene encoding for stromal-derived factor-1 alpha (SDF-1α gene-activated scaffold), can enhance the regenerative functionality of human diabetic adipose-derived stem cells (ADSCs). We assessed the impact of the gene-activated scaffold on diabetic ADSCs by comparing their response against healthy ADSCs cultured on a gene-free scaffold over two weeks. Overall, we found that the gene-activated scaffold could restore the pro-angiogenic regenerative response in the human diabetic ADSCs similar to the healthy ADSCs on the gene-free scaffold. Gene and protein expression analysis revealed that the gene-activated scaffold induced the overexpression of SDF-1α in diabetic ADSCs and engaged the receptor CXCR7, causing downstream β-arrestin signaling, as effectively as the transfected healthy ADSCs. The transfected diabetic ADSCs also exhibited pro-wound healing features characterized by active matrix remodeling of the provisional fibronectin matrix and basement membrane protein collagen IV. The gene-activated scaffold also induced a controlled pro-healing response in the healthy ADSCs by disabling early developmental factors signaling while promoting the expression of tissue remodeling components. Conclusively, we show that the SDF-1α gene-activated scaffold can overcome the deficiencies associated with diabetic ADSCs, paving the way for autologous stem cell therapies combined with novel biomaterials to treat DFUs.

Biopolymer-based biomaterials for accelerated diabetic wound healing: A critical review

Non-healing, chronic wounds place a huge burden on healthcare systems as well as individual patients. These chronic wounds especially diabetic wounds will ultimately lead to compromised mobility, amputation of limbs and even death. Currently, wounds and limb ulcers associated with diabetes remain significant health issues; the associated healthcare cost ultimately leads to the increased clinical burden. The presence of diabetes interrupts a highly coordinated cascade of events in the wound closure process. Advances in the understanding of pathophysiological conditions associated with diabetic wounds lead to the development of drug delivery systems which can enhance wound healing by targeting various phases of the impaired processes. Wound environments typically contain degradative enzymes, along with an elevated pH and demonstrate a physiological cascade involved in the regeneration of tissue, which requires the application of an effective delivery system. This article aims to review the pathophysiological conditions associated with chronic and diabetic wounds. The delivery systems, involved in their treatment are described, highlighting potential biomaterials and polymers for establishing drug delivery systems, specifically for the treatment of diabetic wounds and the promotion of the associated mechanisms involved in advanced wound healing. Emerging approaches and engineered devices for effective wound care are reported. The discussion will give insight into the mechanisms relevant to all stages of wound healing.

Type 2 diabetes is associated with the accumulation of senescent T cells

Type 2 diabetes is a global health priority, given that it is driven, in part, by an ageing population, the role of immune senescence has been overlooked. This is surprising, as the functional impairments of senescent T cells show strong similarities to patients with hyperglycaemia. Immune senescence is typified by alterations in T cell memory, such as the accumulation of highly differentiated end‐stage memory T cells, as well as a constitutive low‐grade inflammation, which drives further immune differentiation. We show here in a preliminary study that people living with type 2 diabetes have a higher circulating volume of senescent T cells accompanied with a higher level of systemic inflammation. This inflammatory environment drives the expression of a unique array of chemokine receptors on senescent T cells, most notably C‐X‐C motif chemokine receptor type 2. However, this increased expression of migratory markers does not translate to improved extravasation owing to a lack of glucose uptake by the T cells. Our results therefore demonstrate that the presence of senescent T cells has a detrimental impact on immune function during type 2 diabetes.

Immune aging in diabetes and its implications in wound healing

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

An Antifouling Hydrogel Containing Silver Nanoparticles for Modulating the Therapeutic Immune Response in Chronic Wound Healing

Patients with diabetic wounds have deficient local and systemic cellular immunity. Herein, a new silver nanoparticle-containing hydrogel with antifouling properties was developed for enhancing the immune response in diabetic wound healing. The antifouling property was obtained by adjusting the composition of cationic chitosan and anionic dextran to approach zero charge. Furthermore, this hybrid hydrogel showed long-lasting and broad-spectrum antibacterial activity. Rapid wound contraction was observed after the treatment with the hydrogel, which suggested its superior healing activity to promote fibroblast migration, granulation tissue formation, and angiogenesis. The upregulation of CD68+ and CD3+ expression levels demonstrated that the hydrogel could trigger immune responses in the treatment of wound healing. These results show that this antifouling hybrid hydrogel as a wound dressing provided a promising strategy for the treatment of diabetic ulcers.

Differentiation of diabetic foot ulcer-derived induced pluripotent stem cells reveals distinct cellular and tissue phenotypes

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.

Drug delivery and tissue engineering to promote wound healing in the immunocompromised host: Current challenges and future directions

As regenerative medicine matures as a field, more promising technologies are being translated from the benchtop to the clinic. However, many of these strategies are designed with otherwise healthy hosts in mind and validated in animal models without other co-morbidities. In reality, many of the patient populations benefiting from drug delivery and tissue engineering-based devices to enhance wound healing also have significant underlying immunodeficiency. Specifically, patients suffering from diabetes, malignancy, human immunodeficiency virus, post-organ transplantation, and other compromised states have significant pleotropic immune defects that affect wound healing. In this work, we review the role of different immune cells in the regenerative process, highlight the effect of several common immunocompromised states on wound healing, and discuss different drug delivery strategies for overcoming immunodeficiencies.

Microhemorrhage-associated tissue iron enhances the risk for Aspergillus fumigatus invasion in a mouse model of airway transplantation

Invasive pulmonary disease due to the mold Aspergillus fumigatus can be life-threatening in lung transplant recipients, but the risk factors remain poorly understood. To study this process, we used a tracheal allograft mouse model that recapitulates large airway changes observed in patients undergoing lung transplantation. We report that microhemorrhage-related iron content may be a major determinant of A. fumigatus invasion and, consequently, its virulence. Invasive growth was increased during progressive alloimmune-mediated graft rejection associated with high concentrations of ferric iron in the graft. The role of iron in A. fumigatus invasive growth was further confirmed by showing that this invasive phenotype was increased in tracheal transplants from donor mice lacking the hemochromatosis gene (Hfe^-/- ). The invasive phenotype was also increased in mouse syngrafts treated with topical iron solution and in allograft recipients receiving deferoxamine, a chelator that increases iron bioavailability to the mold. The invasive growth of the iron-intolerant A. fumigatus double-knockout mutant (ΔsreA/ΔcccA) was lower than that of the wild-type mold. Alloimmune-mediated microvascular damage and iron overload did not appear to impair the host's immune response. In human lung transplant recipients, positive staining for iron in lung transplant tissue was more commonly seen in endobronchial biopsy sections from transplanted airways than in biopsies from the patients' own airways. Collectively, these data identify iron as a major determinant of A. fumigatus invasive growth and a potential target to treat or prevent A. fumigatus infections in lung transplant patients.

Redox Signaling in Diabetic Wound Healing Regulates Extracellular Matrix Deposition

SIGNIFICANCE

Impaired wound healing is a major complication of diabetes, and can lead to development of chronic foot ulcers in a significant number of patients. Despite the danger posed by poor healing, very few specific therapies exist, leaving patients at risk of hospitalization, amputation, and further decline in overall health. Recent Advances: Redox signaling is a key regulator of wound healing, especially through its influence on the extracellular matrix (ECM). Normal redox signaling is disrupted in diabetes leading to several pathological mechanisms that alter the balance between reactive oxygen species (ROS) generation and scavenging. Importantly, pathological oxidative stress can alter ECM structure and function.

CRITICAL ISSUES

There is limited understanding of the specific role of altered redox signaling in the diabetic wound, although there is evidence that ROS are involved in the underlying pathology.

FUTURE DIRECTIONS

Preclinical studies of antioxidant-based therapies for diabetic wound healing have yielded promising results. Redox-based therapeutics constitute a novel approach for the treatment of wounds in diabetes patients that deserve further investigation. Antioxid. Redox Signal. 27, 823-838.

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

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

The phagocytic fitness of leucopatches may impact the healing of chronic wounds

Chronic non-healing wounds are significantly bothersome to patients and can result in severe complications. In addition, they are increasing in numbers, and a challenging problem to the health-care system. Handling of chronic, non-healing wounds can be discouraging due to lack of improvement, and a recent explanation can be the involvement of biofilm infections in the pathogenesis of non-healing wounds. Therefore, new treatment alternatives to improve outcome are continuously sought-after. Autologous leucopatches are such a new, adjunctive treatment option, showing promising clinical effects. However, the beneficial effect of the patches are not understood fully, although a major contribution is believed to be from the release of stimulating growth factors from activated thrombocytes within the leucopatch. Because the leucopatches also contain substantial numbers of leucocytes, the aim of the present study was to investigate the activity of the polymorphonuclear neutrophils (PMNs) within the leucopatch. By means of burst assay, phagocytosis assay, migration assay, biofilm killing assay and fluorescence in-situ hybridization (FISH) assay we showed significant respiratory burst in PMNs, active phagocytosis and killing of Pseudomonas aeruginosa by the leucopatch. In addition, bacterial-induced migration of PMNs from the leucopatch was shown, as well as uptake of P. aeruginosa by PMNs within the leucopatch. The present study substantiated that at least part of the beneficial clinical effect in chronic wounds by leucopatches is attributed to the activity of the PMNs in the leucopatch.

The Anti-Inflammatory and Antibacterial Action of Nanocrystalline Silver and Manuka Honey on the Molecular Alternation of Diabetic Foot Ulcer: A Comprehensive Literature Review

Honey and silver have been used since ancient times for treating wounds. Their widespread clinical application has attracted attention in light of the increasing prevalence of antibiotic-resistant bacteria. While there have been a number of studies exploring the anti-inflammatory and antibacterial effects of manuka honey and nanocrystalline silver, their advantages and limitations with regard to the treatment of chronic wounds remain a subject of debate. The aim of this paper is to examine the evidence on the use of nanocrystalline silver and manuka honey for treating diabetic foot ulcers through a critical and comprehensive review of in vitro studies, animal studies, and in vivo studies. The findings from the in vitro and animal studies suggest that both agents have effective antibacterial actions. Their anti-inflammatory action and related impact on wound healing are unclear. Besides, there is no evidence to suggest that any topical agent is more effective for use in treating diabetic foot ulcer. Overall, high-quality, clinical human studies supported by findings from the molecular science on the use of manuka honey or nanocrystalline silver are lacking. There is a need for rigorously designed human clinical studies on the subject to fill this knowledge gap and guide clinical practice.

Preclinical and clinical evidence for stem cell therapies as treatment for diabetic wounds

Diabetic wounds remain a global unsolved problem and the cost of diabetes-related amputations and diabetic wound treatment is approximately US$3 billion and US$9 billion per year, respectively. Diabetic foot ulcers (DFUs) occur in 15% of all patients with diabetes and precede 84% of all diabetes-related lower leg amputations. Currently, there is no satisfying treatment for these hard-to-heal-wounds. However, as we discuss here, experimental preclinical evidence for the successful use of adult stem cell therapies for diabetic wounds gives new hope for the development of effective treatments for use in the clinic.

Increased number of Langerhans cells in the epidermis of diabetic foot ulcers correlates with healing outcome

Langerhans cells (LCs) are a specialized subset of epidermal dendritic cells. They represent one of the first cells of immunologic barrier and play an important role during the inflammatory phase of acute wound healing. Despite considerable progress in our understanding of the immunopathology of diabetes mellitus and its associated comorbidities such as diabetic foot ulcers (DFUs), considerable gaps in our knowledge exist. In this study, we utilized the human ex vivo wound model and confirmed the increased epidermal LCs at wound edges during early phases of wound healing. Next, we aimed to determine differences in quantity of LCs between normal human and diabetic foot skin and to learn if the presence of LCs correlates with the healing outcome in DFUs. We utilized immunofluorescence to detect CD207+ LCs in specimens from normal and diabetic foot skin and DFU wound edges. Specimens from DFUs were collected at the initial visit and 4 weeks later at the time when the healing outcome was determined. DFUs that decreased in size by >50 % were considered to be healing, while DFUs with a size reduction of <50 % were considered non-healing. Quantitative assessment of LCs showed a higher number of LCs in healing when compared to non-healing DFU's. Our findings provide evidence that LCs are present in higher number in diabetic feet than normal foot skin. Healing DFUs show a higher number of LCs compared to non-healing DFUs. These findings indicate that the epidermal immune barrier plays an important role in the DFU healing outcome and may offer new therapeutic avenues targeting LC in non-healing DFUs.

High serum concentration of interleukin-18 in diabetic patients with foot ulcers

BACKGROUND

It is well known that interleukin-18 (IL-18) plays a key role in the inflammatory process. However, there are limited data on the role IL-18 plays with diabetic foot ulcers, an acute and complex inflammatory situation. Therefore, we aimed to evaluate serum IL-18 levels of diabetic patients with foot ulcers.

METHODS

Twenty diabetic patients with acute foot ulcers, 21 diabetic patients without a history of foot ulcers, and 21 healthy volunteers were enrolled in our study. Circulating levels of IL-18, and other biochemical markers are parameters of inflammation and were measured in all three groups.

RESULTS

Diabetic patients both with and without foot ulcers had high IL-18 concentrations (P < 0.001 and P = 0.020, respectively) when compared with the nondiabetic volunteers. Those with foot ulcers had higher levels of IL-18 level (P < 0.001), high-sensitivity C-reactive protein (hsCRP) (P = 0.001), and erythrocyte sedimentation rate (ESR) (P < 0.001) than those without foot ulcers.

CONCLUSIONS

We found that serum IL-18 concentrations were elevated in diabetic patients with acute diabetic foot ulcers. However, these findings do not indicate whether the IL-18 elevation is a cause or a result of the diabetic foot ulceration. Further studies are needed to show the role of IL-18 in the course of these ulcers.

Diabetic foot ulcers: Part I. Pathophysiology and prevention

Diabetes mellitus is a serious, life-long condition that is the sixth leading cause of death in North America. Dermatologists frequently encounter patients with diabetes mellitus. Up to 25% of patients with diabetes mellitus will develop diabetic foot ulcers. Foot ulcer patients have an increased risk of amputation and increased mortality rate. The high-risk diabetic foot can be identified with a simplified screening, and subsequent foot ulcers can be prevented. Early recognition of the high-risk foot and timely treatment will save legs and improve patients' quality of life. Peripheral arterial disease, neuropathy, deformity, previous amputation, and infection are the main factors contributing to the development of diabetic foot ulcers. Early recognition of the high-risk foot is imperative to decrease the rates of mortality and morbidity. An interprofessional approach (ie, physicians, nurses, and foot care specialists) is often needed to support patients' needs.

Characteristics of an autologous leukocyte and platelet-rich fibrin patch intended for the treatment of recalcitrant wounds

We have investigated the physical, biochemical, and cellular properties of an autologous leukocyte and platelet-rich fibrin patch. This was generated in an automated device from a sample of a patient's blood at the point of care. Using microscopy, cell counting, enzyme-linked immunosorbent assay, antibody arrays, and cell culture assays, we show that the patch is a three-layered membrane comprising a fibrin sheet, a layer of platelets, and a layer of leukocytes. Mean recovery of platelets from the donated blood was 98% (±95%CI 0.8%). Mean levels of platelet-derived growth factor AB, human transforming growth factor beta 1, and vascular endothelial growth factor extracted from the patch were determined as 127 ng (±95% CI 20), 92 ng (±95%CI 17), and 1.35 ng (±95%CI 0.37), respectively. We showed a continued release of PDGF-AB over several days, the rate of which was increased by the addition of chronic wound fluid. By comparison with traditional platelet-rich plasma, differences in immune components were found. The relevance of these findings was assessed by showing a mitogenic and migratory effect on cultured human dermal fibroblasts. Further, we showed that fibrocytes, a cell type important for acute wound healing, could be grown from the patch. The relevance of these findings in relation to the use of the patch for treating recalcitrant wounds is discussed.

Osteomyelitis: an update for hospitalists

Osteomyelitis is a common and challenging condition for hospitalists to manage. The 3 main types of osteomyelitis that are commonly seen in the hospital setting are 1) contiguous spread from decubitus or diabetic ulcers, 2) hematogenous spread, such as in vertebral or long bone metaphyses, and 3) infections associated with a prosthetic joint. In patients with diabetes, osteomyelitis is the underlying cause of about 20% of foot infections, and greatly increases the chance that the patient will eventually need an amputation and be subject to perioperative risks. Osteomyelitis from hematogenous spread is increasing. The prevalence of vertebral osteomyelitis is also increasing, particularly in intravenous drug users and patients treated with immune-modulating agents. Prosthetic joint infections are perhaps the most challenging type to treat, and require hospitalists, orthopedic surgeons, and infectious disease specialists to work closely together to plan for effective treatment. Due to increasing antibiotic resistance, the microorganisms involved are also proving more difficult to treat. Emerging resistance to the commonly used antibiotics is resulting in changes in treatment choices. Community-acquired methicillin-resistant Staphylococcus aureus is commonly seen, and there is increasing concern about emerging vancomycin resistance. Treatment of osteomyelitis is still based largely on expert opinion rather than evidence from controlled studies.

Altered molecular mechanisms of diabetic foot ulcers

The continuously increasing worldwide prevalence of diabetes will be accompanied by a greater incidence of diabetic foot ulcer, a complication in which many of the morphological processes involved in normal wound healing are disrupted. The highly complex and integrated process of wound healing is regulated by a large array of molecular factors. These often have overlapping functions, ensuring a certain degree of tolerance through redundancy. In diabetes, changes to the expression of a large number of molecular factors have been observed, overwhelming this inbuilt redundancy. This results in delayed healing or incomplete healing as in ulceration. Understanding the relationship between altered levels of molecular factors and the inhibited healing process in such ulcers will permit the development of targeted treatments aimed to greatly improve the quality of life of patients, at the same time helping to reduce the huge costs associated with treating this diabetic condition and its long-term consequences. This short review examines how changes in the expression of molecular factors are related to altered morphology in diabetic foot ulceration and very briefly considers treatment strategies at molecular level.

The biology of chronic foot ulcers in persons with diabetes

Diabetic foot ulcers constitute a major health problem and they are recalcitrant to healing due to a constellation of intrinsic and extrinsic factors. The purpose of this article is to review the potential biological mechanisms that deter healing and perpetuate inflammatory responses in chronic diabetes foot ulcers. The link between hyperglycemia induced oxidative stress and its negative impact on cellular functions are explained. Key evidence related to alteration in tissue perfusion, bacterial balance, sustained proteases and cytokines release, leukocyte function, and growth factor production at the local wound level are summarized.

Diabetic foot ulcers — a comprehensive review

As the incidence of diabetes mellitus is increasing globally, complications related to this endocrine disorder are also mounting. Because of the large number of patients, foot ulcers developing in the feet of diabetics have become a public health problem. The predisposing factors include abnormal plantar pressure points, foot deformities, and minor trauma. Vulnerable feet usually already have vascular insufficiency and peripheral neuropathy. The complex nature of these ulcers deserves special care. The most useful prognostic feature for healing remains the ulcer depth, ulcers heal poorly if they clearly involve underlying tendons, ligament or joints and, particularly, when gangrenous tissue is seen. Local treatment of the ulcer consists of repeated debridement and dressing. No 'miraculous' outcome is expected, even with innovative agents like skin cover synthetics, growth factors and stem cells. Simple surgery like split skin grafting or minor toe amputations may be necessary. Sophisticated surgery like flap coverages are indicated for younger patients. The merits of an intact lower limb with an abnormal foot have to be weighed against amputation and prosthesis in the overall planning of limb salvage or sacrifice. If limb salvage is the decision, additional means like oxygen therapy, and other alternative medicines, might have benefits. The off-loading of footwear should always be a major consideration as a prevention of ulcer formation.

Chemokines, cytokines, and growth factors in keratinocytes and dermal endothelial cells in the margin of chronic diabetic foot ulcers

Keratinocytes and dermal endothelial cells, excluding leukocytes that infiltrate wounds, are the main source of soluble factors regulating healing of skin ulcers. We used immunohistochemistry to analyze the expression of various chemotactic and growth factors and their receptors in the margin of diabetic foot ulcers and in normal nondiabetic foot skin. Our study found significantly elevated expression of transforming growth factor-beta1 (TGF-beta1) and type I TGF-beta receptors (TGFbetaR1), granulocyte macrophage colony-stimulating factor (GM-CSF), and epidermal growth factor (EGF) in keratinocytes in the ulcer margin (p < 0.05). Significantly increased expression of monocyte chemotactic protein-1, GM-CSF, CXCR1, and TGFbetaRI and decreased expression of interleukin (IL)-10, IL-15, and TGF-beta1 were observed in ulcer dermal endothelial cells (p < 0.05). There was a lack of up-regulation of IL-8, CCR2A, IL-10 receptor, GM-CSF receptor, platelet-derived growth factors and their receptors, vascular endothelial growth factor and its type II receptor, EGF receptor, insulin-like growth factor-1, and nitric oxide synthase-2 in both KCs and endothelial cells in the ulcer. Finally, there was a lack of up-regulation of IL-10 and IL-15 in keratinocytes and of EGF, basic fibroblast growth factor, and nitric oxide synthase-3 in endothelial cells in the ulcer margins. The enhanced expression of some factors responsible for KC behavior could suggest an unimpaired capacity of keratinocytes to reepithelialize the margin of diabetic foot ulcers. However, lack of up-regulation of some angiogenic and leukocyte chemotactic factors, associated with the reduced influx of immune cells, may account for a poor formation of granulation tissue and chronicity of ulcer epithelialization.

Neurogenic factors in the impaired healing of diabetic foot ulcers

BACKGROUND

We hypothesize that the reduced innervation of skin can be observed both in clinically neuropathic and non-neuropathic diabetic foot ulcers and can contribute to low inflammatory cell infiltration.

MATERIALS AND METHODS

Twenty patients with type 2 diabetes and active foot ulcers, without clinical evidence of peripheral sensory neuropathy (n = 12) and with sensory neuropathy (n = 8) were involved in this study. Biopsies from ulcer margin were examined immunohistochemically.

RESULTS

Studies revealed presence of protein gene product 9.5 (PGP9.5)+ nerve endings only in reticular dermis in 3 of 12 non-neuropathic subjects, however, regenerating GAP-43+ endings were seen in dermis of almost all specimens. Lack of substance P+ nerve endings was characteristic for both groups. The reduced distribution of calcitonin gene-related peptide+ nerves in epidermis and dermis was seen mainly in neuropathic group. In neo-epidermis lack of nerve growth factor expression was observed in both groups, whereas neurotrophin 3 immunostaining was characteristic for neuropathic specimens (P < 0.03). Expression of trkA and trkC receptors did not differ significantly between groups. Low inflammatory cell infiltration and moderate presence of fibroblasts was characteristic for all studied specimens.

CONCLUSIONS

The observed reduction of foot skin innervation and neurogenic factors expression can be correlated with low inflammatory cell accumulation and subsequently leads to the observed chronicity of diabetic foot ulcer healing process in both neuropathic and non-neuropathic patients.